rmchrgr
Skate And Destroy
You could easily make the argument to ditch V.A. in any performance application. It's tough to dial it in with bigger cams, carbs and intakes. The gain in mileage is probably not worth the effort.
Gas Mileage???
- Thread starter y2swinger69
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brasil
Well-Known Member
I worked a lot today... went down to 10 deg @ idle then 25 deg advance all in @ 4000 rpm.. ( the engine has a lot more torque now ! ) and I installed the crane VC limiter... ( kind of tricky...but at the end it worked ) The VC now pulls 10 deg. more is not possible.... but better than nothing. Also the VC helps on the start line...
Greetings Juergen
Greetings Juergen
rmchrgr
Skate And Destroy
10 degrees at idle is low, like factory spec low. 25 degrees all in by 4,000 rpm is also low and slow.
In general, your timing curve should be around 15 -18 degrees initial with any sort of cam and 34-36 total, all in by 3,000 rpm. 10 degrees from the vacuum can seems about right though but if your total timing is only 25 degrees then you're still low.
Two different situations being discussed here. One is a near factory stock engine and drivetrain, the other is a hot rodded engine. The first will work best, especially for milage, using the stock specs as a baseline. The hot rodded cases should use the accumulated experience of hot rodders and racers as a baseline.
Y2 - That's not too far off from factory. CarLife Road test for 1969 340 'cuda states 11-14 mpg as normal range. Since you are running everything close to factory spec, use the factory specs as baseline for the ignition timing. Then fiddle with the carb.
Side note on carb: With the total gearing combination some of your highway driving will be low throttle position. So don't think its neccessarily all in the primary jetting (it could even be drawing from 'idle circuit' as Holley's do when coasting at moderate highway speeds). Chrysler Master Tech Conference is as good as any place to start for explanation of Carter carbs. (available on-line at www.imperialclub.org as well as Hammtramck Historical and mymopar)
For the timing curves, look up the factory specs in a '69 FSM. Compare that with the timing on your engine. ALL of it; idle, the entire mechanical advance curve (at least three points), the vacuum advance (at least 3 points). IF the factory used manifold vacuum for the distributor advance, use manifold vac. If it used ported, use ported vacuum. With a factory cam, the actual timing at idle when using manifold vacuum will be idle spec plus vacuum advance. So don't get fooled by a low initial. Go for max advance the engine will tolerate. Today's fuel may result in ping at part throttle. In this case - adjust for less vacuum advance.
Those with mildly hot rodded engines - Cam overlap etc reduces the manifold vac at idle. Using more initial timing compensates for this. As soon as the throttle opens just a bit, manifold vacuum increases. That's why many have found ported vacuum advance plus more initial is better for hotrods. This arrangement is fairly simple to set up and eliminates the question of whether the vacuum advance will be in play at idle.
Adjusting Vacuum Advance Pods - For mopar distributors, the cans with a hex shaped nose usually can be adjusted with an allen key. This alters the vacuum when the advance is added or not. The maximum amount of advance a vacuum pod can add is based on the notch in the arm. A piece of wire or sheet metal can be used to reduce the movement.
If you're willing to do a little work, I think there is some good info in the threads here:
Racing Fuel systems Forum Ignition
especially Too much advance at light throttle?
Y2 - That's not too far off from factory. CarLife Road test for 1969 340 'cuda states 11-14 mpg as normal range. Since you are running everything close to factory spec, use the factory specs as baseline for the ignition timing. Then fiddle with the carb.
Side note on carb: With the total gearing combination some of your highway driving will be low throttle position. So don't think its neccessarily all in the primary jetting (it could even be drawing from 'idle circuit' as Holley's do when coasting at moderate highway speeds). Chrysler Master Tech Conference is as good as any place to start for explanation of Carter carbs. (available on-line at www.imperialclub.org as well as Hammtramck Historical and mymopar)
For the timing curves, look up the factory specs in a '69 FSM. Compare that with the timing on your engine. ALL of it; idle, the entire mechanical advance curve (at least three points), the vacuum advance (at least 3 points). IF the factory used manifold vacuum for the distributor advance, use manifold vac. If it used ported, use ported vacuum. With a factory cam, the actual timing at idle when using manifold vacuum will be idle spec plus vacuum advance. So don't get fooled by a low initial. Go for max advance the engine will tolerate. Today's fuel may result in ping at part throttle. In this case - adjust for less vacuum advance.
Those with mildly hot rodded engines - Cam overlap etc reduces the manifold vac at idle. Using more initial timing compensates for this. As soon as the throttle opens just a bit, manifold vacuum increases. That's why many have found ported vacuum advance plus more initial is better for hotrods. This arrangement is fairly simple to set up and eliminates the question of whether the vacuum advance will be in play at idle.
Adjusting Vacuum Advance Pods - For mopar distributors, the cans with a hex shaped nose usually can be adjusted with an allen key. This alters the vacuum when the advance is added or not. The maximum amount of advance a vacuum pod can add is based on the notch in the arm. A piece of wire or sheet metal can be used to reduce the movement.
If you're willing to do a little work, I think there is some good info in the threads here:
Racing Fuel systems Forum Ignition
especially Too much advance at light throttle?
brasil
Well-Known Member
@rmchrgr I think you understood me wrong.. I meant 10 deg @ idle...and 25 deg. advance on top...so 35 deg. all in.. at 4000 rpm.. ( yes I know the curve is slow..but the enginge pulls very very strong .. sadly the vacuum canister... only works well under WOT and off the line. The 50-60 mph ratteling is still there.... ( Made some test runs today )
@all
Next I changed the VC from Ported to Full Manifold Vacuum.. Great for a smooth idle..( 20 deg )
but that it... 50-60 mph rattteling...
So I changed the set up again.... 16 deg. @ idle and 18 deg advance...all in @
3500 rpm.... still a little rattleing...at 50 -55 mph without load... Frustrating !!
Beside this "50-60 mph problem " the engine pulls strong also...
I know now...that the engine doesn´t want more than 25 deg of advance @ 2400 /2500 rpm....
Is that normal ??
Greetings Juergen
@all
Next I changed the VC from Ported to Full Manifold Vacuum.. Great for a smooth idle..( 20 deg )
but that it... 50-60 mph rattteling...
So I changed the set up again.... 16 deg. @ idle and 18 deg advance...all in @
3500 rpm.... still a little rattleing...at 50 -55 mph without load... Frustrating !!
Beside this "50-60 mph problem " the engine pulls strong also...
I know now...that the engine doesn´t want more than 25 deg of advance @ 2400 /2500 rpm....
Is that normal ??
Greetings Juergen
rmchrgr
Skate And Destroy
OK, gotcha. That sounds about right but... your initial is still low. 10 degrees is not much, that's factory spec. and does not allow for much 'performance'. I didn't see what your engine combo was but if it's stock, then OK but if it's modified in any way then you want more initial. Even a stock 318 2bbl can benefit from more initial.
But, the caveat here is that you need to limit the mechanical advance. This will segue into my next reply, see below.
I think what's happening here is that since your advance curve is slow to come in, it's probably still advancing at anything under 4,000 rpm. Add in vacuum advance and you have too much timing for that low of an an RPM. Vacuum advance comes in with a high vacuum situation like cruise so yeah, it's gonna ping.
If you're wanting to get this sorted out, you have to get into the distributor. You need to change the advance weight springs to get the curve to come in quicker, so likely a lighter spring than what you have now. The advance curve should be 'all in' by 2,500-3,000 rpm. Just to make sure - when you set the timing, you have the vacuum advance disconnected and plugged, right?
If you decide to try more initial timing, you will need to figure out how much centrifugal advance is in the distributor. You have to measure the slots in the plate under the pickup.
Here's a chart to show how much advance the plate gives. Multiply the number X2 to get the amount of advance. Most of the 'stock' type distributors I've taken apart usually have 13 degrees and up (13 x 2 = 26). If you want less, you have to weld/epoxy the slots to get the advance to stop. Or, get the FBO limiter plate which also comes with springs.
So you can see what happens if you have a lot of centrifugal advance, you can't run a lot of initial or you start to go beyond the normal 34-36 range.
degrees / slot size
6.............. .340
7................355
8................375
9................390
10...............405
11.5 ...........420
12...............435
13...............445
14...............460
15...............475
16...............490
17...............505
18...............520
Not normal. It should be happy with more timing at light throttle. For example a stock 1968 340 distributor would have advanced 22 to 24 degrees at 2400 rpm, plus whatever the initial timing was spec'd at. For cruising it would have 17 more degrees as long as there was at least 10 inches of manifold vacuum. So that's at least 39 degrees while cruising at 50 mph or so.
How are you measuring the timing?
What distributor is that? Are you going by info in an instruction manual? It might be giving you distributor (cam) degrees. My advice is measure and plot out the timing curve. Then measure when the vac advance starts and stops as well as how much it adds.
How are you measuring the timing?
What distributor is that? Are you going by info in an instruction manual? It might be giving you distributor (cam) degrees. My advice is measure and plot out the timing curve. Then measure when the vac advance starts and stops as well as how much it adds.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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brasil
If I understand your ramblings correctly, you ended up at ;16/34@ 3500plus10 ported
If your curve starts at 1000 then your dizzy is kicking in 18* in 3500 less 1000= 2500rpm. so that would be 18/25 = .72*/100rpm. I like that number. It means that at 2500, the engine is seeing;(2500 less 1000)/100 x .72 =10.8 degrees plus your initial of 16* =27*. That puts your power curve just a little ahead of mine,( which works very well for me, on 87E10.). To that 27* you then add the Vcan of 10 =37* for cruise timing.
If your engine will not accept 37* of cruise timing, something is wrong.
The first place I would look is the timing lite and the second is the TDC mark.And the third is the engine running temp.After that is the Squish. There is a squish dimension that actually makes things worse. We all know that that squish from .030 to about .050 works pretty good, We also know than squish greater than about .080 is no squish at all. It's that in between zone that can cause trouble. IIRC your cylinder pressure was quite high. And that would compound the problem. That is to say; high cylinder pressures and intermediate squish makes trouble. If your carb is also sucking hot underhood air, that's a triple whammy.
Now I tell you what; up to this point you haven't offered your cam specs.Nor your true compression ratio. So if you post those up, I will attempt to back-calculate your Dcr. But I cannot see into your engine to measure your squish.
These are the numbers I need; exact bore and stroke, rod length(or stock), Static compression ratio OR average cylinder pressure from a known good gauge, and the intake closing angle. If you don't know the intake closing angle, then I need the advertised intake-duration and lobe displacement angle.If you don't know any of that, how about a cam part number, and I'll go look it up. What's the big deal about the Dcr? well it could help to figure out what is going on.
If I understand your ramblings correctly, you ended up at ;16/34@ 3500plus10 ported
If your curve starts at 1000 then your dizzy is kicking in 18* in 3500 less 1000= 2500rpm. so that would be 18/25 = .72*/100rpm. I like that number. It means that at 2500, the engine is seeing;(2500 less 1000)/100 x .72 =10.8 degrees plus your initial of 16* =27*. That puts your power curve just a little ahead of mine,( which works very well for me, on 87E10.). To that 27* you then add the Vcan of 10 =37* for cruise timing.
If your engine will not accept 37* of cruise timing, something is wrong.
The first place I would look is the timing lite and the second is the TDC mark.And the third is the engine running temp.After that is the Squish. There is a squish dimension that actually makes things worse. We all know that that squish from .030 to about .050 works pretty good, We also know than squish greater than about .080 is no squish at all. It's that in between zone that can cause trouble. IIRC your cylinder pressure was quite high. And that would compound the problem. That is to say; high cylinder pressures and intermediate squish makes trouble. If your carb is also sucking hot underhood air, that's a triple whammy.
Now I tell you what; up to this point you haven't offered your cam specs.Nor your true compression ratio. So if you post those up, I will attempt to back-calculate your Dcr. But I cannot see into your engine to measure your squish.
These are the numbers I need; exact bore and stroke, rod length(or stock), Static compression ratio OR average cylinder pressure from a known good gauge, and the intake closing angle. If you don't know the intake closing angle, then I need the advertised intake-duration and lobe displacement angle.If you don't know any of that, how about a cam part number, and I'll go look it up. What's the big deal about the Dcr? well it could help to figure out what is going on.
brasil
Well-Known Member
...good morning
So first of all Thank you for your help !! I apreciate this very much
@ aj/forms what does Squish mean ?
About the timing light... I have two a dial back from equs and a Bosch TL both show the same numbers...but the Dial back is not so good to use.. because of the MSD Dizzy...
About my engine....
340 block from 1973 ( with cast crank ) X heads from 1969 4bbl intake from 1971 ( Oem Cast Iron for Spread bore carbs )
MSD ready to run distributor ( so I can limit the advance very easy ) HP Manifolds
Passenger side: Part#2863549
Drivers side: Part#2863553
The pistons are Flat Top ( bought a endoscope to look inside the cylinders)
I am not sure if the former builder saved the heads.) The compression test showed
180-190 psi on all cyl. Vacuum @ idle with 16 deg initial is 15inches ROCK SOLID when I shift into DRIVE the vacumm goes down.... flucktrating very fast between 10 and 13 inches..
Sparkplugs are 65 Autolite
The Tranny is a 727 with stock TC ( still has the drain plug ) axle gears are 3.23
Tires are 225 / 60 /15
The engine runs with 180°F doesn´t matter if I drive on the highway...in the city..or whatever... So no cooling issues...
The Balancer seems to be o.k... I changed the timing chain /gears... and the TDC
mark showed exacatly 0 . ( Also the Problem existed before the chain change.. and the old chain had a lot of slash 1/2 inch )
Sadly I don´t know...what kind of cam is installed... also the CR is unknown.
Intresting thing.... I found out that the engine makes a lot more power ...if the curve is slower.... with a fast curve the engine sounds very stressed! Using the slow curve ( curve A or Curve B from the MSD Instructions ) the engine pulls like a
TRUCK... Using a fast curve makes the "pinging / rattling " issue worse
When I use less than 10 deg timing @ idle the engine shakes like hell... and I have to open the primary trottle blades too far...
I think to know whats going on ..I have to pull the engine ... pull the heads and the cam... also....
Greetings Juergen
Btw... forgot something.... The last curve I posted...is without VC ! The engine doesn´t accept the extra deg. of Timing....coming from the VC @ cruise speed ..50-60 mph till 45 mph everthing is fine... WOT also.... off the line... etc...
So first of all Thank you for your help !! I apreciate this very much
@ aj/forms what does Squish mean ?
About the timing light... I have two a dial back from equs and a Bosch TL both show the same numbers...but the Dial back is not so good to use.. because of the MSD Dizzy...
About my engine....
340 block from 1973 ( with cast crank ) X heads from 1969 4bbl intake from 1971 ( Oem Cast Iron for Spread bore carbs )
MSD ready to run distributor ( so I can limit the advance very easy ) HP Manifolds
Passenger side: Part#2863549
Drivers side: Part#2863553
The pistons are Flat Top ( bought a endoscope to look inside the cylinders)
I am not sure if the former builder saved the heads.) The compression test showed
180-190 psi on all cyl. Vacuum @ idle with 16 deg initial is 15inches ROCK SOLID when I shift into DRIVE the vacumm goes down.... flucktrating very fast between 10 and 13 inches..
Sparkplugs are 65 Autolite
The Tranny is a 727 with stock TC ( still has the drain plug ) axle gears are 3.23
Tires are 225 / 60 /15
The engine runs with 180°F doesn´t matter if I drive on the highway...in the city..or whatever... So no cooling issues...
The Balancer seems to be o.k... I changed the timing chain /gears... and the TDC
mark showed exacatly 0 . ( Also the Problem existed before the chain change.. and the old chain had a lot of slash 1/2 inch )
Sadly I don´t know...what kind of cam is installed... also the CR is unknown.
Intresting thing.... I found out that the engine makes a lot more power ...if the curve is slower.... with a fast curve the engine sounds very stressed! Using the slow curve ( curve A or Curve B from the MSD Instructions ) the engine pulls like a
TRUCK... Using a fast curve makes the "pinging / rattling " issue worse
When I use less than 10 deg timing @ idle the engine shakes like hell... and I have to open the primary trottle blades too far...
I think to know whats going on ..I have to pull the engine ... pull the heads and the cam... also....
Greetings Juergen
Btw... forgot something.... The last curve I posted...is without VC ! The engine doesn´t accept the extra deg. of Timing....coming from the VC @ cruise speed ..50-60 mph till 45 mph everthing is fine... WOT also.... off the line... etc...
Last edited:
BigBlockMopar
BigBlockMember
squish = quench (distance between piston and head).
brasil
Well-Known Member
O.k I Understand thank you
You may be able to see the markings on the flat tops, for TRWs I have the overbore size is marked on the tops.
How many bumps? Regardless, that seems healthy and also suggests cam closer to stock.
This suggests the fuel/air and timing are are not providing quite enough power to idle smooth in Drive. Try a little bit more fuel at idle (idle mix screws another 1/16 to 1/8 turn richer).
If you have the time and patience, you could measure the cam lift and and degrees each opens using a degree wheel and dial indicator at the rockers....
Don't worry about 'fast' or 'slow'. An engine engine with an efficient burn will need less timing.
What do those curves look like?
With an MSD distributor you may need to make adjustments beyond what they supply. Besides changing springs, you can make your own bushings or modify the shape of the curve. See link to forum I posted previously to find info on how to do that. But first you need to know what you have. Measure and plot it out from 500 rpm (or as low as it will go) to 4000 rpm (if you can do so safely).
brasil
Well-Known Member
when I looked inside the cylinders.... the surface of the piston was not clean...so I can´t see anything like numbers.. or so...
when I made the compression test..i gave every cyl. 5 bumps...
The mixture @ idle is around 12.5-13 AFR
tomorrow I will write down the numbers of the timing curve
the plugs are middle brown... btw..
I also read the thread about the distributors... your set up looks very close to mine.. So can you tell me what springs you use..and the numbers @ idle and the advance rate ?
Greetings Juergen
when I made the compression test..i gave every cyl. 5 bumps...
The mixture @ idle is around 12.5-13 AFR
tomorrow I will write down the numbers of the timing curve
the plugs are middle brown... btw..
I also read the thread about the distributors... your set up looks very close to mine.. So can you tell me what springs you use..and the numbers @ idle and the advance rate ?
Greetings Juergen
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Carbon on the cylinder tops but sparky is clean. Interesting. Since what you're seeing is cumulative from all sorts of driving its probably not good to jump to any conclusions. However it is good to make a mental note of it.
OK. (see AFR relation to load for ranges to expect). That doesn't change the fact that the engine seems to be telling you it wants slightly richer. As long as it doesn't load up the spark plugs with carbon, give it what it wants.
PS. Check it in Drive as well as Neutral - it might get a little leaner in D because the vacuum went down.
PSS. The AFR mixture from a WBO2 is based on Lambda and a factor based on an assumed stoichiometric ratio of 14.7:1. If the petrol used has a different density and stoich (as is common here in the USA), the actual afr will be a little different than what the meter shows. Our usual petrol here nowadays is something like 40% refined petroleum, and as much as 10% ethanol.
Even racing fuels vary quite a bit when it comes to density and stoich. But at least the suppliers of race fuel publish all the specs...Anyway, the point is not to target an AFR, but pay attention to what AFR gets the results.
brasil
Well-Known Member
Thank you Mattax
I will check for the AFR Numbers tomorrow. Will take some pics from the plugs also.
Perhaps the fuel we use here is a little better than yours ? I use a fuel that not contains ethanol.. ( is a little more expensive..but well worth the money ) This gas has 102 European Octane.. so about 97 -98 of your Ron /moz gas
We have also Shell V Power that has 100 Octane.. 95-96 in your numbers..
Greetings Juergen
I will check for the AFR Numbers tomorrow. Will take some pics from the plugs also.
Perhaps the fuel we use here is a little better than yours ? I use a fuel that not contains ethanol.. ( is a little more expensive..but well worth the money ) This gas has 102 European Octane.. so about 97 -98 of your Ron /moz gas
We have also Shell V Power that has 100 Octane.. 95-96 in your numbers..
Greetings Juergen
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
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Greetings
Yes your combo is messed up. But not hopeless.
Your vacuum reading is ambiguous on account of there is no frame of reference. It must be accompanied by rpm and timing.
And here is why; Using the same warmed up engine,try this; put the vacuum gauge on it as it sits. read the timing and the rpm. Now advance the timing5*, and re-read the rpm and vacuum. Now retard the timing 10*, and reread the rpm and vacuum.Then put the timing back to the start.
So you see what happened? The vacuum and idle speed may have changed dramatically.
However I got one clue; The dramatic fluctuation from out of gear, to in gear. The biggest contributor to this phenomenon is the T-port synchronization,
See http://www.forabodiesonly.com/mopar/threads/ajs-guide-to-transfer-port-synchronization.
So I played with the Wallace calculator, and here are the results.With your idle-vacuum, and power descriptions, I guessed at at a 276* cam with a 64* ICA. This is a pure guess. I inputed a 4.07 bore x 3.58 stroke, and a stock 6.123 rod. At a Scr(Static Cr) of 11.3, the calculator spit out a Dcr(Dynamic CR) of 9.0 and cylinder pressure of 186psi.There are many other numbers that could spit out the same pressure, so this is not an exact number.
Now here's the deal; if 9.0Dcr is close, then you are between 1/2, and 1.0 point too high on the Dcr and the same on the Scr. My calculator says to make 11.3Scr you need a total chamber volume of just 74cc. Assuming a 8.9cc gasket(.039) and no eyebrows on the pistons(you didn't mention seeing any) that means you have 65cc heads. These indicate nothing out of the ordinary yet. But 65cc X-heads are fairly heavily cut, or nailhead valves might have been installed.
So your engine is operating under a double whammy; 1) too much Scr, and 2) too much Dcr.
There is only one cure for too much Scr and that is to increase the total chamber volume. Unfortunately, to get down to 9.5 would require a huge change of 15.8cc. There is no cheap or easy way to do this. Further more we don't know what is inside the chamber without looking. There might be eyebrows, and there might be an .020 gasket, and there might be pop-up pistons in there, so we cannot formulate a plan of action at this time.
Now we could slam a cam in there about three sizes bigger, say the 292/108, in at 106, and get an ICA of 72*. This would drop the Dcr down to 8.4/170psi. While this would make a ton of power on unlimited gas, and the more sane Dcr would make a strong bottom end, this cam won't make any mpgs. It also won't put up with that TC or gears. So this is not a good solution in the long run.
Now just a reminder; this is all speculative.
If you are really running 11.3 Scr at near sealevel, you are gonna break something at WOT, soon,Especially with a small cam. It is just a matter of time. (EDIT; maybe not with your 98 equivalent gas).
There is one hope. And I would certainly try it. And that is water injection. You have an engine with a great deal of potential, as it sits. If it was mine I would give water injection a try. It is not magic, but certainly cheaper than a whole new top-end and the possibility of pistons too.Plus there is a very really possibility of a lot more power lurking in that engine, with just a cam-swap.
RSR 1000 PSI Water Injection
Yes your combo is messed up. But not hopeless.
Your vacuum reading is ambiguous on account of there is no frame of reference. It must be accompanied by rpm and timing.
And here is why; Using the same warmed up engine,try this; put the vacuum gauge on it as it sits. read the timing and the rpm. Now advance the timing5*, and re-read the rpm and vacuum. Now retard the timing 10*, and reread the rpm and vacuum.Then put the timing back to the start.
So you see what happened? The vacuum and idle speed may have changed dramatically.
However I got one clue; The dramatic fluctuation from out of gear, to in gear. The biggest contributor to this phenomenon is the T-port synchronization,
See http://www.forabodiesonly.com/mopar/threads/ajs-guide-to-transfer-port-synchronization.
So I played with the Wallace calculator, and here are the results.With your idle-vacuum, and power descriptions, I guessed at at a 276* cam with a 64* ICA. This is a pure guess. I inputed a 4.07 bore x 3.58 stroke, and a stock 6.123 rod. At a Scr(Static Cr) of 11.3, the calculator spit out a Dcr(Dynamic CR) of 9.0 and cylinder pressure of 186psi.There are many other numbers that could spit out the same pressure, so this is not an exact number.
Now here's the deal; if 9.0Dcr is close, then you are between 1/2, and 1.0 point too high on the Dcr and the same on the Scr. My calculator says to make 11.3Scr you need a total chamber volume of just 74cc. Assuming a 8.9cc gasket(.039) and no eyebrows on the pistons(you didn't mention seeing any) that means you have 65cc heads. These indicate nothing out of the ordinary yet. But 65cc X-heads are fairly heavily cut, or nailhead valves might have been installed.
So your engine is operating under a double whammy; 1) too much Scr, and 2) too much Dcr.
There is only one cure for too much Scr and that is to increase the total chamber volume. Unfortunately, to get down to 9.5 would require a huge change of 15.8cc. There is no cheap or easy way to do this. Further more we don't know what is inside the chamber without looking. There might be eyebrows, and there might be an .020 gasket, and there might be pop-up pistons in there, so we cannot formulate a plan of action at this time.
Now we could slam a cam in there about three sizes bigger, say the 292/108, in at 106, and get an ICA of 72*. This would drop the Dcr down to 8.4/170psi. While this would make a ton of power on unlimited gas, and the more sane Dcr would make a strong bottom end, this cam won't make any mpgs. It also won't put up with that TC or gears. So this is not a good solution in the long run.
Now just a reminder; this is all speculative.
If you are really running 11.3 Scr at near sealevel, you are gonna break something at WOT, soon,Especially with a small cam. It is just a matter of time. (EDIT; maybe not with your 98 equivalent gas).
There is one hope. And I would certainly try it. And that is water injection. You have an engine with a great deal of potential, as it sits. If it was mine I would give water injection a try. It is not magic, but certainly cheaper than a whole new top-end and the possibility of pistons too.Plus there is a very really possibility of a lot more power lurking in that engine, with just a cam-swap.
RSR 1000 PSI Water Injection
Last edited:
brasil
Well-Known Member
Thank you aj/forms
sounds not so good.... too much DCR too much SCR.. Sadly I just bought the new Distributor...and also a 670 Streetavernger Carb ( I think the carb is way too small... if my combo is as you think... ) Today I will check the Holley Carb... put him on the engine yesterday..but because of the neighbours I couldn´t let him run.....
So for the next step...I think I will buy some Aluminium heads.. because here in Germany we can not install Water Injektion legaly.... First I will pull the heads
and measure the cc then thickness of the current Head gasket... and the size of the pistons... incl deck height...
I also will try to make the T Port Sync. today... hope to get it done
Greetings Juergen
@ all : once again...thank you very much for your help !! Here in Germany ....a US car owner is lost... nobody knows anything about engine builts....
sounds not so good.... too much DCR too much SCR.. Sadly I just bought the new Distributor...and also a 670 Streetavernger Carb ( I think the carb is way too small... if my combo is as you think... ) Today I will check the Holley Carb... put him on the engine yesterday..but because of the neighbours I couldn´t let him run.....
So for the next step...I think I will buy some Aluminium heads.. because here in Germany we can not install Water Injektion legaly.... First I will pull the heads
and measure the cc then thickness of the current Head gasket... and the size of the pistons... incl deck height...
I also will try to make the T Port Sync. today... hope to get it done
Greetings Juergen
@ all : once again...thank you very much for your help !! Here in Germany ....a US car owner is lost... nobody knows anything about engine builts....
In my opinion you are jumping ahead. Work one step at a time - unless you just want to start over with a fresh engine build.
I thought you're running a Carter Thermoquad on a spreadbore intake? In any event, any carb can be made to run well. However I think mixing spreadbore and 'squarebore' is less likely to have good fuel distribution.
The Holley transfer slots do need to be within a limited range for the carb to work properly. - just to be clear - I agree with AJ
Figure out your timing first. Tuning is an iterative process, but if the timing is too far off, playing with the fuel air mix is wasting time. AJ wrote he guessing based on very limited info. If you measure the valve lift you will know much more about both cam and then make a better guess at compression.
I thought you're running a Carter Thermoquad on a spreadbore intake? In any event, any carb can be made to run well. However I think mixing spreadbore and 'squarebore' is less likely to have good fuel distribution.
The Holley transfer slots do need to be within a limited range for the carb to work properly. - just to be clear - I agree with AJ
Figure out your timing first. Tuning is an iterative process, but if the timing is too far off, playing with the fuel air mix is wasting time. AJ wrote he guessing based on very limited info. If you measure the valve lift you will know much more about both cam and then make a better guess at compression.
BigBlockMopar
BigBlockMember
I agree with measuring the actual valve lift (or lifter lift) first. Then go online and find cams that have similar lifts.
This will give you a better idea of the current cam in the engine.
This will give you a better idea of the current cam in the engine.
brasil
Well-Known Member
so for measuring the valvelift...I can do this on the edge of the rocker ? I have magnet dial watch... so if I set the tip on the edge of the rocker and turn the engine over..will the result be o.k ( because of the hydraulic tappet )
The carb runs good b.t.w. .
@ mattax.... yes I used a Thermoquad..nut unfortunatly the bowl has a crack...
and the fuel was dripping into the manifold.. Now I use the Holley with a square to spread bore adapater ..
Greetings Juergen
The carb runs good b.t.w. .
@ mattax.... yes I used a Thermoquad..nut unfortunatly the bowl has a crack...
and the fuel was dripping into the manifold.. Now I use the Holley with a square to spread bore adapater ..
Greetings Juergen
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
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- 24,913
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- 12,263
I'll go you one better
Crank the engine over to put #6 piston on the compression stroke. Install a compression tester hose with the lower valve removed. Inject about 20 psi in there, to push the piston back down the way it came. Then reduce the pressure, while hand-cranking the piston up against the pressure. There will come a point when the intake valve closes, and pressure will no longer be heard hissing into the intake, and it will become difficult to raise the piston. Try to pinpoint this exact spot. When you get it, mark the damper next to the TDC mark. That is your Intake Closing Angle. It may not be exact, but if you are real careful it will be pretty close.
Now, finding the other end is impossible with the valve gear installed. But if you are serious, you will pop the entire rocker arm assembly off then reinstall number 6 intake rocker only,and go find it the same way. Simply turn the engine over backwards until the hissing stops and again find that exact spot and mark the damper next to the TDC mark.This is your intake opening angle. With a cloth tape or some flexible tape, measure the distance between the marks. Them measure the entire circumference of the damper. Or you can take a shortcut and take a diameter of the damper and just multiply that by 3.1416(Pi).
Now you do the math, Say you have a 7" damper which would be 22 inches around, and you measured 16.5 inches between the marks. Then 16.5/22 = 3/4 of a turn and since a full turn is 360 degrees, that makes your cam .75 x 360 =270 degrees on the intake. If you measured 17.6, then 17.6/22 x 360 =288*. With this number and the lift numbers, finding the cam in a catalog should be easy. Is it easier than degreeing it?heckYa. Is it faster? heckYa. Is it accurate? It can be pretty close, but it is only as accurate as the guy doing it, and it can be a little difficult with the fan in there, so I take it out. That thing has eaten enough of my skin for two lifetimes. It should get you pretty close cuz most cams are rated at .006 or .008 lift. and you are finding Zero lift. So this method should be a little more than advertised, but with errors, it might be right on. But even if you are off at each end by 1/16, that totals (2 x .0625)/22 x 360 = 2 degrees, and if your tape measure is off another 1/16, that could either reduce the error to 1* or increase it to 3 degrees. This is still less than one cam size.
You can actually use any cylinder to do this, but by using #6 or #1, I suppose you could also figure out the installed centerline, cuz you have a correct TDC mark.
Crank the engine over to put #6 piston on the compression stroke. Install a compression tester hose with the lower valve removed. Inject about 20 psi in there, to push the piston back down the way it came. Then reduce the pressure, while hand-cranking the piston up against the pressure. There will come a point when the intake valve closes, and pressure will no longer be heard hissing into the intake, and it will become difficult to raise the piston. Try to pinpoint this exact spot. When you get it, mark the damper next to the TDC mark. That is your Intake Closing Angle. It may not be exact, but if you are real careful it will be pretty close.
Now, finding the other end is impossible with the valve gear installed. But if you are serious, you will pop the entire rocker arm assembly off then reinstall number 6 intake rocker only,and go find it the same way. Simply turn the engine over backwards until the hissing stops and again find that exact spot and mark the damper next to the TDC mark.This is your intake opening angle. With a cloth tape or some flexible tape, measure the distance between the marks. Them measure the entire circumference of the damper. Or you can take a shortcut and take a diameter of the damper and just multiply that by 3.1416(Pi).
Now you do the math, Say you have a 7" damper which would be 22 inches around, and you measured 16.5 inches between the marks. Then 16.5/22 = 3/4 of a turn and since a full turn is 360 degrees, that makes your cam .75 x 360 =270 degrees on the intake. If you measured 17.6, then 17.6/22 x 360 =288*. With this number and the lift numbers, finding the cam in a catalog should be easy. Is it easier than degreeing it?heckYa. Is it faster? heckYa. Is it accurate? It can be pretty close, but it is only as accurate as the guy doing it, and it can be a little difficult with the fan in there, so I take it out. That thing has eaten enough of my skin for two lifetimes. It should get you pretty close cuz most cams are rated at .006 or .008 lift. and you are finding Zero lift. So this method should be a little more than advertised, but with errors, it might be right on. But even if you are off at each end by 1/16, that totals (2 x .0625)/22 x 360 = 2 degrees, and if your tape measure is off another 1/16, that could either reduce the error to 1* or increase it to 3 degrees. This is still less than one cam size.
You can actually use any cylinder to do this, but by using #6 or #1, I suppose you could also figure out the installed centerline, cuz you have a correct TDC mark.
Last edited:
MopaR&D
Nerd Member
How do they regulate something like that? Do you have inspections where someone looks under the hood of your car? That's the only way someone could catch it. Also do you know why it's illegal? I can't think of a good reason why... Just wondering...
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
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- 24,913
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Oh chit, Brasil did you say 340?
I screwed up and nobody caught it.
But the good news is I screwed up twice and they cancelled each other out.
So reworking the formulas for a 3.31 stroke and one size smaller cam to get the 15 inches idle at 16* timing , all the numbers work out close to the same.
And so, back in 99 I ran my aluminum headed 360 at 11.3 Scr with a 292/509 on 87E10 with no detonation at 34degrees. The Wallace calculator says the Dcr on that was 9.03/186psi.
Your 340 with say 11.2 and a 270/110cam would be at 9.1/188. That's about the same so it should be easy with your cam, and should be dynomite with those 3.23s. You are gonna need more rubber tho. It will certainly be infinitely better than it is now. And you will finally be able to run a Vcan.
So off with a head!
I screwed up and nobody caught it.
But the good news is I screwed up twice and they cancelled each other out.
So reworking the formulas for a 3.31 stroke and one size smaller cam to get the 15 inches idle at 16* timing , all the numbers work out close to the same.
And so, back in 99 I ran my aluminum headed 360 at 11.3 Scr with a 292/509 on 87E10 with no detonation at 34degrees. The Wallace calculator says the Dcr on that was 9.03/186psi.
Your 340 with say 11.2 and a 270/110cam would be at 9.1/188. That's about the same so it should be easy with your cam, and should be dynomite with those 3.23s. You are gonna need more rubber tho. It will certainly be infinitely better than it is now. And you will finally be able to run a Vcan.
So off with a head!
Last edited:
brasil
Well-Known Member
AJ/FORMS yes 340 
so you think the best way is to pull a head... ( or both ) see what is inside.... the surprise box and go from there... Here in Germany I can get these heads..
Designed for 1967 bis 1991 318, 340, 360 cid engines. These are brand new castings with the 62cc closed chamber. Dual exhaust bolt pattern to use sandart or W-2 headers. Assembeled with premium components. Intake runners volume is 179cc compared to the J or X Head 160cc. The original Valvetrain does fit, no offset Rockers are needed.
• LA style using standard intake
manifold and rocker shaft, heads
are drilled for the correct valve
cover & gasket.
• LA and Magnum accessory holes
on both ends of head.
Heads Feature:
• Dual pattern exhaust bolts,
standard pattern & W2
• 8mm intake valves 1.92 or 2.02
• 8mm exhaust valves 1.625
• 62 cc combustion chamber
(wir haben auch schon mal 59cc gemessen)
• 179 cc intake runner (as cast)
• 67 cc exhaust runner (as cast)
• Multi-angled intake valve seats
• Radius exhaust valve seats
• Improved valve guide design
• Highly effi cient water jacket
• Hardened valve seats
• Extra thick deck faces
Options:
*2,02" Intake Valves
• Available with no push rod holes drilled in
casting for CNC intake porting.
• Offset rocker arm sets available for CNC
ported heads.
• LA-X casting available with 3/8 valve
guides for stock valves.
• Stage I, II, & III CNC porting available.
The following parts are included:
360-H1-LAXB (Lax Bare Head Castings)
360-V1-X-192 (1.92 Valve 5/16)
ALL-R1-X (X Heads Standard Retainers)
ALL-V3-VS802V (5/16 X .530 Viton Seal
360-V1-X162 (1.625 Valve 5/16
If I can use them ( depends on the combustion camber ) I will also buy a EDE performer RPM Intake...to get rid of the Adapter...
Hope to get the "train " runnin... soon
Greetings Juergen
@ All here in Germany...we have a LAW that you can drive a OLD car without Catalyc Converter.... with low TAXES ... BUT the car ( older than 30 years ) has
to be in a close to original shape... disc brakes on the rear axle is a no go ( for example )... a Water injection or even a fuel injection is the same... NOT allowed
You can be happy to live in the US or Canada....
so you think the best way is to pull a head... ( or both
) see what is inside.... the surprise box and go from there... Here in Germany I can get these heads..Designed for 1967 bis 1991 318, 340, 360 cid engines. These are brand new castings with the 62cc closed chamber. Dual exhaust bolt pattern to use sandart or W-2 headers. Assembeled with premium components. Intake runners volume is 179cc compared to the J or X Head 160cc. The original Valvetrain does fit, no offset Rockers are needed.
• LA style using standard intake
manifold and rocker shaft, heads
are drilled for the correct valve
cover & gasket.
• LA and Magnum accessory holes
on both ends of head.
Heads Feature:
• Dual pattern exhaust bolts,
standard pattern & W2
• 8mm intake valves 1.92 or 2.02
• 8mm exhaust valves 1.625
• 62 cc combustion chamber
(wir haben auch schon mal 59cc gemessen)
• 179 cc intake runner (as cast)
• 67 cc exhaust runner (as cast)
• Multi-angled intake valve seats
• Radius exhaust valve seats
• Improved valve guide design
• Highly effi cient water jacket
• Hardened valve seats
• Extra thick deck faces
Options:
*2,02" Intake Valves
• Available with no push rod holes drilled in
casting for CNC intake porting.
• Offset rocker arm sets available for CNC
ported heads.
• LA-X casting available with 3/8 valve
guides for stock valves.
• Stage I, II, & III CNC porting available.
The following parts are included:
360-H1-LAXB (Lax Bare Head Castings)
360-V1-X-192 (1.92 Valve 5/16)
ALL-R1-X (X Heads Standard Retainers)
ALL-V3-VS802V (5/16 X .530 Viton Seal
360-V1-X162 (1.625 Valve 5/16
If I can use them ( depends on the combustion camber ) I will also buy a EDE performer RPM Intake...to get rid of the Adapter...
Hope to get the "train " runnin... soon
Greetings Juergen
@ All here in Germany...we have a LAW that you can drive a OLD car without Catalyc Converter.... with low TAXES ... BUT the car ( older than 30 years ) has
to be in a close to original shape... disc brakes on the rear axle is a no go ( for example )... a Water injection or even a fuel injection is the same... NOT allowed
You can be happy to live in the US or Canada....
-
