Super tuning car runs good shooting for great

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skep419

skep419

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69 dart 360 ede heads,voodoo 60403, speed pro 416 Pistons,scat i beams, ede air gap, 750 Holley dp.

4 speed cf dual friction 2.66

8 3/4 3.91 have a 3.23 set up that I'd like to swap soon.

Car runs good. But I recently swapped cams so I thought I should check the cranking compression.

It's now at 200.
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I've been running 91 for the most part but put in 87 without any issues (haven't felt any pinging) when 91 isn't available.

Initial is at 20 with 34 total. It comes in fast and I'd like to get aggressive with the vacuum advance if I could find the right can.
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Are you willing,to commit to premium(a j oke,in itself ) pump gas?.. At 200 cranking : I would Personally,I would start with wideband O2 sensors,before adding that vacuum advance..FWIW,quite a bit of adjustments,via allen wrench in stock mopar diaphragms. I would worry about air & fuel ratios ,before vacuum advance. J.M.O....
 
Trust me, with 200 REAL PSI and 87 you HAVE detonation. Just because you do not hear it, doesn't mean it's not doing it. It NEEDS better fuel.
 
RustyRatRod said:
Trust me, with 200 REAL PSI and 87 you HAVE detonation. Just because you do not hear it, doesn't mean it's not doing it. It NEEDS better fuel.
Click to expand...

Nevermind........I missed that you have Eddy heads. That changes things somewhat.
 
Abodybomber said:
Are you willing,to commit to premium(a j oke,in itself ) pump gas?.. At 200 cranking : I would Personally,I would start with wideband O2 sensors,before adding that vacuum advance..FWIW,quite a bit of adjustments,via allen wrench in stock mopar diaphragms. I would worry about air & fuel ratios ,before vacuum advance. J.M.O....
Click to expand...

I agree with all that, even with the aluminum heads pump gas gets sh***ier every year I would run strictly premium. I had to do the same on my iron Magnum headed 10.5:1 360, after I saw the telltale signs of detonation ('dust' on spark plugs, tiny pits on piston heads) I added a hood scoop for proper cold-air intake and now only run "premium" 91 after also adjusting the timing a hair.

If you want to tune properly by the plugs you need a plug reader tool or similar microscope thingy (Mike Finnegan from Roadkill recommends a doctor's tool for looking inside ears) to look down at the lower parts of the porcelain. The wideband O2 sensor and AFR gauge is a huge help for tuning as well but if you want that last bit of physical information to get the tune 100% spot-on you kind of need to check the plugs.

As far as vacuum advance goes that just helps during cruise/light throttle (in case you didn't already know) for better MPGs and reduced cylinder wear. There are writeups out there on how to adjust the Mopar vacuum advance if you search, my advice would be to use a Mity-Vac handheld pump with a line going into the car from the can on the dist. so you can adjust it on-the-fly while driving and figure out what the engine likes best. And/or you can also pop off the dist. cap and look at the advance plate while you pump up the vacuum and watch the gauge on the pump; this will give you a good idea of when the can starts to pull.
 
vacuum advance

AJ/FormSFormulaS clone 367/3.55s 3.09-1.92-1.40-1.00-.78GVFABO Gold Member
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Many times when setting this, the idle timing will creep up and up as various engine parameters interplay. So if it ends up that your particular combo requires a large amount of timing to get the t-port properly working, then the addition of vacuum advance, by way of full manifold vacuum may drive the engine into pinging at very small throttle openings where the vacuum advance will not yet drop out.
One solution to this might be to use ported vacuum, instead. In this case the vacuum might not be enough to even activate the can and so the pinging goes away.
A second solution might be to reduce the initial timing, and a third solution might be to get a smaller can, and a fourth solution might be to adjust the onset of the Vcan, and a fifth, is some combination of all of these.
I try to leave the initial timing alone once the T-port sync is established.
On the other hand, with a small cam and lots of compression. The T-port sync might generate a very small number for idle timing.Yet the engine might still accept 34 to 36 as power-timing.And most guys will want to bring it in really early.And without a Vcan or with a high-stall, there is almost nothing wrong with that. As your engine snaps up to stall it runs through this zone and is never stuck working there.But if you have a typical stock-type TC which fits well with the small cam engine, then you run into issues where the centrifugal timing overlaps with the vacuum timing at small throttle settings and there's that pesky ping again.
The 360 is a good example. With a 223 cam and 10.7Scr,and a stick and 3.23s.This combo packs a wicked street punch, once wound up a little. But the 2.66 x 3.23 offers just 8.59 as a starter gear. The T-port sync might call for 12* initial. The power timing will still be 34 to 36.So yo have to build a centrifugal curve to go from 12 to 36. That's 24* in the dizzy;no biggie. But that engine at 65mph, will be turning 2600 Rs and might like 50* or more timing. So I like to work with the 20*Vcan. Then 50 less 20 is 30 in the centrifugal.That curve is almost buildable. But back up to first gear. If you hook the can to manifold vacuum it will idle at 12 + 20 =32*It might put up with that at idle.But as soon as you roll on the throttle, you will force the engine to to be heavily loaded by the clutch and the 8.59 starter gear. And she is gonna rattle to no end.And it will only get worse with more throttle, until the manifold vacuum falls to a level that the timing drops out to a level the engine can accept.
On the otherhand, hooking the can to the sparkport, gives you a lot of throttle blade angle before the Vcan gets signal, and the signal is weak in the early part as the blade goes by and strengthens over time until the vacuum begins to fall.You can handily take advantage of this, by adding the Vcan timing which is varying from zero to 20* and back to zero, with manipulation of the gas-pedal.In this way you can add up to 20* of timing at any time in the low to medium loading parameter, and the beast will be more controllable than the typical on/off behavior that full manifold vacuum exhibits.
But notice that this applies to a stickshift car with hi-way gears, almost a worst case scenario.But this is what guys build cuz that's what we are stuck with in terms of having just a 4speed.
The thing to keep in mind is that I set the initial timing by the T-port sync. I let it tell me what the engine wants. I don't even pay attention to the timing lite or a vacuum gauge, at this stage.You may end up with idle timing anywhere between 10 and 20-25, depending on your particular combo. This target is primarily determined by cam size and compression, but there are other factors.
 
Do you mean Speed Pro H116CP pistons? The 416 PN is not registering with me. Or is this a 416 stroker? This engine must be pushing into the 12:1 SCR range if this compression pressure if true and with this 271* advertised cam.

For H116CP pistons and Edelbrock heads and this cam, and a typical setup, this compression pressure does not work out to being even close to reality; that is why I ask about the gauge being correct, the pistons, the cam being very advanced, etc. Just trying to make sense of your numbers before commenting on tuning.
 
I assume you have closed chamber heads. Also assume your pistons are near zero deck and your using approx .040 thick head gasket. If all my assumptions are correct you have a quench motor and 200 psi is ok with the proper tune.
As mentioned you need to look at the porcelain for metallic specks.
The 4 speed and 3.91 is in your favor (no engine lugging)
I run a 360 Magnum OEM pistons and heads, 234@.050 cam 108 LSA 106 ICL, 200 psi cranking compression on 89 octane. 27* initial, 34* total, 48* with Vacuum adv highway cruise AFR 14.5 with no issues. Car was dialed in with wideband and slowly advanced timing and leaned fuel curved until it was dialed in.
Distributor is modified to limit max Vac Advance. Adjust can allen screw for when advance starts, adjust max advance stop (4-40 mach screw and lock nut) for how much. See mod picture.

dist mod 002.JPG
 
nm9stheham said:
Do you mean Speed Pro H116CP pistons? The 416 PN is not registering with me. Or is this a 416 stroker? This engine must be pushing into the 12:1 SCR range if this compression pressure if true and with this 271* advertised cam.

For H116CP pistons and Edelbrock heads and this cam, and a typical setup, this compression pressure does not work out to being even close to reality; that is why I ask about the gauge being correct, the pistons, the cam being very advanced, etc. Just trying to make sense of your numbers before commenting on tuning.
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yes h116cp pistons, 63cc ede heads, stock blue felpro head gaskets cam installed straight up
 
skep419 said:
yes h116cp pistons, 63cc ede heads, stock blue felpro head gaskets cam installed straight up
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OK, that is what seesm odd to me.....with stock stroke, that combo works out to around 9.8 SCR in an LA block and 10.1 in a Magnum block (with no significant decking on either block), with DCR's in the low 8's for both, and the compression numbers should be in the 160ish range. With zero decking, it is up to 10.5 SCR and about 8.5 DCR; cranking pressures are still in the 170ish range.

So IMHO the gauge may be dodgey, or the cam is installed waaaay advanced, or the lifters are bleeding down and shortening cam duration a lot. Or maybe someone DID sneak in an itty-bitty turbo and you just have not spotted it yet LOL

IMHO, it should be a good combo for the street with a good torque band.
 
I would say ditch the vacuum advance. What do you want/need it for? I've never had vacuum advance on my Duster.

Also, my slug of a truck runs better with no V.A. and I even saw a mileage increase without it.
 
rmchrgr said:
I would say ditch the vacuum advance. What do you want/need it for? I've never had vacuum advance on my Duster.

Also, my slug of a truck runs better with no V.A. and I even saw a mileage increase without it.
Click to expand...

Basically free MPGs on the street... if that was the case with your truck then it wasn't working right, plain and simple.

"BUT WE DRIVE OLD V8 MOPARS who cares about gas mileage blah blah blah" there I said it before anyone else lol. That kind of reasoning is like turning down a free baker's dozen of donuts just because you don't feel like going to the donut shop right around the corner. It's so easy if you just take a little time to get it right.
 
Except in cases where vacuum advance throws a wrench in everything and causes issues. Sometimes it's just doesn't work out.

With 200 psi cylinder pressure you may not be able to feed much vacuum advance in over whatever total you currently have.
 
mderoy340 said:
I assume you have closed chamber heads. Also assume your pistons are near zero deck and your using approx .040 thick head gasket. If all my assumptions are correct you have a quench motor and 200 psi is ok with the proper tune.
As mentioned you need to look at the porcelain for metallic specks.
The 4 speed and 3.91 is in your favor (no engine lugging)
I run a 360 Magnum OEM pistons and heads, 234@.050 cam 108 LSA 106 ICL, 200 psi cranking compression on 89 octane. 27* initial, 34* total, 48* with Vacuum adv highway cruise AFR 14.5 with no issues. Car was dialed in with wideband and slowly advanced timing and leaned fuel curved until it was dialed in.
Distributor is modified to limit max Vac Advance. Adjust can allen screw for when advance starts, adjust max advance stop (4-40 mach screw and lock nut) for how much. See mod picture.

View attachment 1714960837
Click to expand...

I saw this mod somewhere else and could not remember how it was done, thanks for posting!
 
crackedback said:
Except in cases where vacuum advance throws a wrench in everything and causes issues. Sometimes it's just doesn't work out.

With 200 psi cylinder pressure you may not be able to feed much vacuum advance in over whatever total you currently have.
Click to expand...

Thanks for clarifying Rob.

I believe the benefits would be minimal on this combo, it wouldn't be worth the effort trying to tune it, you'd be fighting an uphill battle. V.A. is essentially a controlled vacuum leak.

Generally, vacuum advance adds timing at part throttle/high vacuum/cruise situations. Why do you need that here? If 'ol Skep is driving his car on the highway more than not, well, the combo is probably not the greatest for that.

In the case of my truck - a heavy vehicle with a low-geared, wide ratio transmission and highway gears - I have relatively LOW cylinder pressure because the P.O. put a large duration cam in a stock, low compression short block with the pistons a mile down in the cylinder. Heads are open chamber with a high-rise intake. The tune requires a bunch of initial timing to get it to run OK and under under a slight load it pings and stumbles like crazy. I messed with it to no end and tried my best to find the spot where it liked it but in the end it was not worth the hassle.

Only thing I could say is that perhaps I could put some heavier springs in the distributor to slow down the advance at low RPM under load but that's another Catch 22 that's probably not worth the slight gain in mileage.
 
I had trouble getting my 340 to run with vacuum advance without pinging with my last cam, 235@.50 solid cam 106 LSA, installed at 102. It had 185 psi cranking pressure. Never did get it to work without pinging, new cam is 252 @ .50 but on a wider 110 LSA, in at 106, and actually acts a lot smaller than it really is. Going to try out the vacuum advance with this cam, limiting the amount like shown above, after I check cranking compression.
 
For the OP, we are running vacuum advance on my son's 340 on the street with a very similar combo to yours:
- flat top KB's, zero decked
- 63 cc Edelbrocks, quench gap at .040-045"
- true SCR at 10-10.2, DCR at around 8.2-8.4 with a Crane Z-268 hydraulic flat lifter cam; cranking compression averaging at 158 psi (that number is right where it should be)
- Initial at 15 and total at 35-37
This engine has yet to ping once, running 93 octane Shell premium, or no-name ethanol free premium.

If you are aiming for better fuel economy, then look into an AFR gague and work your AFR up into the 15's at light cruise.
 
skep419 said:
with the comp xe284 cam that i just took out it had 175
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Interesting.....What lifters are you running and rockers? Where is the lifter preload set?? (These numbers are still high for the combo of parts so I am trying to understand the cause.)
 
rmchrgr said:
Thanks for clarifying Rob.

I believe the benefits would be minimal on this combo, it wouldn't be worth the effort trying to tune it, you'd be fighting an uphill battle. V.A. is essentially a controlled vacuum leak.

Generally, vacuum advance adds timing at part throttle/high vacuum/cruise situations. Why do you need that here? If 'ol Skep is driving his car on the highway more than not, well, the combo is probably not the greatest for that.

In the case of my truck - a heavy vehicle with a low-geared, wide ratio transmission and highway gears - I have relatively LOW cylinder pressure because the P.O. put a large duration cam in a stock, low compression short block with the pistons a mile down in the cylinder. Heads are open chamber with a high-rise intake. The tune requires a bunch of initial timing to get it to run OK and under under a slight load it pings and stumbles like crazy. I messed with it to no end and tried my best to find the spot where it liked it but in the end it was not worth the hassle.

Only thing I could say is that perhaps I could put some heavier springs in the distributor to slow down the advance at low RPM under load but that's another Catch 22 that's probably not worth the slight gain in mileage.
Click to expand...

That is a pretty unique case, also Crackedback there must be some validity from that statement coming from you so I'll have to rethink my opinion a bit lol!

I know messing around with the vacuum can on mine, it can be adjusted "tight" enough to where it never reaches full advance based on the amount of vacuum the engine can pull. Ex: vacuum can is adjusted to have full advance in at 25" but your engine only pulls 15", you'll only ever get 1/2 or so the 'available' vacuum advance from the can... Really not the ideal way to do it though the proper way to limit vacuum advance is with a different can altogether
 
When you have a rowdy cam with lots of overlap and low vacuum at idle, you're starting from a decidedly different point than your average '60's-'70's pass. car tune. Your initial timing is usually much higher than the limp-wristed factory settings. Start adding extra timing in and you can see why it doesn't work in some situations.

Trying to tune vacuum advance so it doesn't produce negative effects seems counterproductive. If you have to fiddle with it more than just a little bit, it's not worth the effort.

An air fuel ratio gauge is a great tool but it's only for one part of the equation. It's easy enough to run a vacuum gauge into the car while driving and see what numbers come up during different driving scenarios. Make a chart and try to determine where and how the extra advance would do benefit the tune in specific situations. I bet you wouldn't find many places it would be of use except for part throttle cruise on the highway.
 
I've run up to about 185psi or a bit more with aluminum heads on 87E10, and 22 * in the Vcan, for 44 to 46 total@2200 for cruising.And she wants more.
My initial is adjusted to 14*, and PowerTiming is 28*@2800,32/34 @3400.My centrifugal is running at about .8* per 100 rpm from 1000 to 2800 rpm, and then it slows down to bring in another 4* by about 3400.This curve lets me burn 87E10 for all circumstances.
Since such a huge part of my driving is to and from town;20 minutes each way, and since such a huge part of my driving is at low power settings, the vacuum advance was very important to me.For me,the vacuum advance smooths the cruise and PT power delivery, and keeps the oil cleaner.

Between this and overdrive, I was able to take a Hughes270* cam to 32mpgUS.
Final drive ratio was 1.965, making 65mph=1600 or so;so the 600 Holley was just barely open. That's what 185psi is good for.
We were cruising with traffic for a good number of hours, at around 2100rpm
At 2100, the centrifugal was about 23*. The vcan is able to add up to 22, but I no longer recall what the vacuum was on that trip. I think I was running full Vcan, so that would be 23+22=45*; about double. You cant do 45* on centrifugal alone.
 
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Manifold vacuum is 21 above 2200 in 4th.

Stays the same all the way up to 2800 which is 60mph

Letting off coasting it gets to 24.
 
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