Definitely with that elevation you are going to want to narrow the lobe separation angle, as others have stated, to 108, or possibly 106. This fools the engine into thinking it has more compression by building more cylinder pressure. This comes at the price of a more choppy idle, worse mileage, and sometimes a more peaked power curve. Again, I recommend speaking with a cam grinder specializing in Mopar. Try Jim Dowel at Racer Brown Cams.
340 street build help from experienced input
- Thread starter Cmanhattan
- Start date
-
Cmanhattan
Member
Love your math, have 3.91 set I will likely swap into then. 6000ft is a bummer here, vs. being from 700ft WI…No on the first gear change. Been eyeing a passion hemi OD gear set to swap out guts but that’s still 2.66 first. Entertain me on some roller solid choices that would be beneficial for this platform. I figured the 10.6 cr with aluminum heads would be maxing out utilizing pump gas on a daily here, and again thanks for your and everybody else’s help.
furrystump
Well-Known Member
- Joined
- Nov 13, 2004
- Messages
- 2,103
- Reaction score
- 1,699
So, here is a question, so with a street car why a roller cam. Not a race car, so you don’t need to snap the valve open. Not chasing the last hp. Solid flat tappet. Much cheaper, dependable as a anvil. If the car progresses towards more power to take advantage of the heads. Then you can go serious solid roller. This has the feel of “it has a roller cam, whoo hoo” but not needing one, which is putting you in a hyd lifter box. I mean no disrespect.
Cmanhattan
Member
No disrespect taken, that’s why I came here, for some knowledge of “you’re being dumb and you should use this instead.” I figured on a hydraulic roller merely on the guise of driver with less maintenance and higher lift over a flat cam. Not afraid of a solid, just mindset wasn’t there. Last solid cam I had was a ‘66 Fury II 318 poly.
@Cmanhattan I want to apologize for missing your 6,000 ft altitude. IF! You see a shelf cam that fits the bill, mostly.... ask the cam company to narrow the cam up for what AJ & cpearce was saying. Getting that adjusted is cheap and more of what will help the engine out in a few fronts.
Just food for thought.... if this route is within hour wallet... a low first gear trans would be a good swap. IIRC (and I would check this!) a 3.09 first gear non OD trans was available. This would really help out a lot for the initial get up and go factor. Coupled with the adjustment on the cam it should really be quit nice.
I’m down near sea level. Living on an island that doesn’t leak very high. I can squeak by on a few items that I would seriously consider doing in your area.
If the wallet was thick enough, I’d look into an OD trans with the 3.91’s rod that Hwy. drivability. Perhaps a 5spd manual. It will turn 3.91’s into 2.70-ish ratio. Ideas for the future.....
Just food for thought.... if this route is within hour wallet... a low first gear trans would be a good swap. IIRC (and I would check this!) a 3.09 first gear non OD trans was available. This would really help out a lot for the initial get up and go factor. Coupled with the adjustment on the cam it should really be quit nice.
I’m down near sea level. Living on an island that doesn’t leak very high. I can squeak by on a few items that I would seriously consider doing in your area.
If the wallet was thick enough, I’d look into an OD trans with the 3.91’s rod that Hwy. drivability. Perhaps a 5spd manual. It will turn 3.91’s into 2.70-ish ratio. Ideas for the future.....
512Stroker
We are all here because we are not all there.
Rumble have you measured cranking cylinder pressure with this cam?
I use the same cam in my 340 and have recorded low cylinder pressures.
Always wondered if it was the cam or other?
512Stroker
We are all here because we are not all there.
Do your homework on the forum for issues related to retro fit hyd rollers.
No disrespect taken, that’s why I came here, for some knowledge of “you’re being dumb and you should use this instead.” I figured on a hydraulic roller merely on the guise of driver with less maintenance and higher lift over a flat cam. Not afraid of a solid, just mindset wasn’t there. Last solid cam I had was a ‘66 Fury II 318 poly.
The can/have become troublesome and are not worth the $.
Go solid you will be better off all around.
Sorry no. This stuff, in general, is in my head as to what is crappy, good, great and pushing it. IIRC, my static is 11.3-1. More than enough on the island. It runs well on 93. I believe I could find more power with more octane. But pump gas was the target.
Thanks! Is that an easy to change over?
I agree with that. If you had a Magnum block call moments to begin with..... then IMO, it becomes ether or cam style.
This is true, it is however an easy conversion. To make the swap you will need a different tailhousing and mainshaft. I have a 3.09 non od A833 in my Dart and I am very happy with it.
furrystump
Well-Known Member
- Joined
- Nov 13, 2004
- Messages
- 2,103
- Reaction score
- 1,699
The maintenance on a solid is overstated. Once it settles in it doesn’t change much. If it starts to open up, you know you have an small issue before it becomes a bigger issue. Checking it once a year is like a physical for the car. A car capable of low 11’s is pretty easy with solid flat tappet. Especially with a good cylinder head. Roller lifter is good for snapping the valve open to a useable lift number very quickly. It is more complex and can be harder on everything else in the valvetrain, because the speed at which it can move the valve. They need more valve spring etc. For someone like me, yes. Solid roller is in my future. The class I run put’s me in a box where it is difficult to increase gross valve lift. So a good option is to snap open the valve quicker. But street car, no real need to add a complex part when a simple one will get you to your goal rather easily. You also can go roller in the future if you want more power. Oh, personally if it has adjustable rockers, I will never use a hydr lifter. Stock rebuild, ok. Anything else for me its gets a solid lifter. I have been down the hydr mysterious lifter road. Pumps up/bleeds down, and rollers REALLY don’t like to bounce!
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,898
- Reaction score
- 12,251
Wait!!!!!!! you have aluminum heads?
Well then
Let me tell you, I have run the pressure to 185psi AND MORE with a tight-Q and STILL BURNED 87E10. I did that for FOUR or more years, in my Daily Driver, taking the engine apart every winter for inspection. After that, I changed the cam, increased the Scr to keep the pressure up and drove another decade or more.
Aluminum heads is absolutely the best thing you can do for altitude compensation. This opens up a whole new page of cam selection.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,898
- Reaction score
- 12,251
Yes; plug and play; I have done exactly that. I ordered the gearset from Passon, and supplied the shaft and tail-piece from my stock, to make it a slip-yoke trans. While I had Jamie on the line I ordered his aluminum box and side-cover as well. I have not ever had problems with this combo or with Jamie's parts.
BTW
even tho the ratios from second to fourth are almost identical to the 2.66low box; NONE of the gears are interchangeable. With the possible exception of the M/S* First; I forget. The tooth counts are all different.
You can often find this "Commando " trans for sale right here on FABO. Usually for a fair price. Everybody has a short tail cast-iron housing for give-away prices. But the large-spline short A-body M/S you might have to cough up some cash for. With 16% more Torque Multiplication, you could theoretically run 16% less rear gear. In practice, I found 3.55s still give the best zero to 60, finishing at 60= 5140 in Second gear, with 27" tires. This then allows a power-peak as low as 4800. Which is like a 220*@.050 cam. And a cam this small brings new vigor to a Lo-Compression engine, and offers the possibility of GREAT fuel economy to a DD.
Edit; M/S is mainshaft
Last edited:
Quick question AJ, what does “M/S” stand for. Manual shift? Thanks.
Personally myself, I’d leave the 3.55’s in there and let it rip.
Personally myself, I’d leave the 3.55’s in there and let it rip.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,898
- Reaction score
- 12,251
With alloy heads and a solid-lifter cam, you can bump the pressure to 185 and still run pump gas. I would willingly run 87E10 .
That pressure is now governed by the co-operation of the Scr (static Compression Ratio) and the Ica( Intake closing angle).
If you have and intend to keep the 2.66 low trans, then you have to keep that in mind when engineering the cranking cylinder pressure. But when the pressure goes over 170ish, a funny thing happens; the First-gear traction goes away. I guarantee you that you will need to fit 295/50-15s, to keep it from spinning out, in aggressive driving, even in Second gear.
So ,IMO, there is not much benefit to a streeter, to go too crazy with a very high cranking cylinder pressure. A better measuring stick for your combo, is the V/P index number, and a combination of the right gearing.
Read about V/P here
V/P Index Calculation
V/P is dependent on pressure and cylinder volume. So, if you target a specific V/P number, you can do it by varying one or both of the pressures or the volume. This how a stock 318LA can make the same VP as a big-cammed 340, or even run with a 440Magnum; With a manual trans at low-rpm, it's all about VP.
Ok so here are the stock V/P numbers of a few engines corrected to 6000ft;
225 @8.0 Scr is 72
273 @8.0 Scr is 78
318 @8.0 Scr is 91
360 @8.0 Scr is 98
318@9.2Scr is 113
340@10.5Scr is 114 ( Like yours will be with a 340 cam)
so that is how they stack up at 6000 ft.
My 367 came in at 163VP with an Ica of 61* at 900 ft, with no other changes , at 6000 the VP drops to 139. At 900ft this was a Monster fun combo, with any gear I tried, 2.76s included. So My conclusion is that 163VP is waaaaaaaay overkill .
IMO, 140 at 900ft would likely have been sufficient ......... but once I had 163 it was too much fun to run less.
Now;
for you, running 163 is out of the question. 140 will be hard enough, depending on how small a cam you are willing to run.
If you can't get up to 140, you will need more TM(Torque Multiplication), to make the engine feel bigger than it is. This works very well in the first two gears, but at the top of Third, the Power will seem flat, and in Fourth, the truth will come out.
So lets target 140@6000ft and see what the Wallace spits out.
At 10.95Scr I get 140@ Ica of 56* , and pressure of 164psi.... so these are the MINUMUMs to get 140. And you could easily run iron heads at 164psi.
So lets increase the Scr .
At 11.50 Scr I get 140 @ Ica of 60 and the pressure is 170psi
At 11.85 Scr I get 140 @ Ica of 62, and the pressure is 173
I don't know how much more Scr your combo can run at WOT, so I will stop there.
But I didn't buy alloy heads to run iron pressures so lets get the pressure up to in the range of 180 to 185, what's it gonna take.
Ok well, at 11.8Scr and Ica of 56* the pressure has risen to 183psi with a V/P of, are you ready? 156VP. This is big-block V/P. This is about your Maximum.
So that means; at the minimum, you can run a hydro, but at the maximum, you would have to run a solid.
Ok now why would you want to run 183 psi?
Well for one thing this has the potential to make fantastic fuel economy. But more importantly, when you step on the gas of a well tuned engine at 183psi......... chit happens right away. There is no lag, no hesitation, no "please massa, not again, bs"; the engine just goes. And it starts so nice; click-vroom. And it will idle right down slooooooow, with minimum timing.
The thing is, with a manual trans, your engine is married to the tires; there is no hydraulic coupling and NO TM in the convertor, so V/P and pressure are suddenly your best friends. The smaller the engine, the more important this becomes. Now, I know a 340 is not generally though of as small, but at 6000ft it is actually tiny, because it just cannot process a lot of air.
So at low-rpm, which is what a streeter is, anything you can do to get your engine to process more air, will help it overcome it's "smallness."
Ok so, in my mind, I have settled on a solid-lifter cam. Because it will have a small Ica for a bigger .050, making the getting of pressure easier. Plus getting 11.8 Scr is gonna be impossible if all your players are already chosen, and I don't wanna send you to the poorhouse. So what is the maximum Scr you can make with your parts using the thinnest reliable gasket that you can find? Is it just 10.5? Or was that calculated using the ever-popular FelPro .039?
You said your Scr was 10.5. Well, to get that at a bore of 4.06 requires a total chamber volume of 74.2cc. You said your chambers were 60cc, so that leaves 14.2 for everything else. Assuming flat-tops with 5cc eyebrows, that then leaves 9.2 for the gasket and the deck-height. If the gasket is .039(8.8cc) then the deck-height is .4cc or pistons .0014 below deck. Ok so that is making sense. The simplest solution is the .028 gasket, which is good for 2.5cc so the chamber size would fall to 71.7 and your new Scr comes to 10.83 lets call that accurate, and the best you are willing to do. Lets plug that into the Wallace. I get 140VP at Ica of 55* and pressure of 163. Not a lot of pressure for alloy heads, but for 140VP, this is what it is with an Ica of 55*
How about we sacrifice a bit of VP and we'll make it up with the 3.91s. This will allow a drop in VP of 10% so now targeting a minimum of 126, no way. I ain't agoing that low. Lets target 135.
Ok at Ica of 57*, Scr of 10.83 the VP falls to 135 with pressure of 160, A V/P of 135 is the very least I would run. and This would then be the latest Ica (57*) I would run with an Scr of 10.83
So now we have an Ica range of 55 to 57 degrees
Ok lets recap at Scr of 10.83 (.028 gasket at about zero-deck), and a V/P range of 135 to 140, we need an Ica of 55 to 57 Degrees.
see how easy that was? lol.
Sooo final question is; what size cam is this?
Well it turns out that this Ica can be had on a lot of hi-torque hydraulic cams; not hi-power. Here are some;
256/262/110 in at 108, or estimated .050 of 212
262/266/108 in at 105, or estimated .050 of 216
268/276/106 in at 102, ...estimated .050 of 222
All of these hydros will have an Ica of 56* when installed at the listed numbers. Notice how small these hydros have to be, to satisfy the 56* Ica.
What about a solid?
IDK the numbers with those are crazy to try and guess because, they are rated differently because of the lash factor. However you can still run off the .050 numbers if the manufacture will supply it. In that case you can add some arbitrary number representing the opening ramp from the point the lash is actually taken up to zero. When I have seen this done, I have seen ramp lengths of as little as 36* but typically 39/40.
If that is true
then
I suppose, and I'm guessing, that you could subtract this fictional 40 degrees from the cams listed and get NEW theoretical .050s of 216/222/and 228
Ima liking that 222.
But you will HAVE to call a grinder to get the true numbers. I have given you this story so you can at least understand how this all works
because at 6000 ft, and just 10.83Scr, there will not be any off-the-shelf performance-cam to satisfy your build, that will not suffer from a soft bottom end, which, with a manual trans, will be intolerable in just a few hours of around-town driving. And if you install the 3.91s, then hi-way driving will very quickly also become intolerable. That is to say, with 26.7" tires and 3.91s; 65=3200. But maybe your tolerance level is higher than mine,lol.
And for me, having such a BB type VP of 163, there is no way I would go back to a VP of something less than 135. No way at all.
Do you have to run a VP of greater than 135?
No, I have to.... cuz for me, 135 is already pretty soft.
If you are used to sub 120 numbers I suppose it's all relative.
A final point is this; If yur not gonna get into cranking cylinder pressures over 160, then honestly, iron heads will do an excellent job at up to ~165 on pumpgas. So you couldda saved a wheel-barrow of money by slapping on a set of Magnums or any big-port, small-chamber ,iron heads.
Happy HotRodding
Last edited:
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,898
- Reaction score
- 12,251
M/S is mainshaft
Cmanhattan
Member
Wow AJ, schooling me here. I’ll hit the books here and figure what I’m looking for with what I do have now. Love this site, thanks for all the help gents. Prob PM ya AJ with some questions. Sounds like I’ll steer toward a solid but what I’m needing isn’t off the shelf and need a custom grind.
AJ is pretty good. He can school ya hood & will help you out really well in the right direction. You’ll also be surprised what is on the shelf from “Other” cam grinders.
aaronk785
Well-Known Member
Howard’s makes solid rollers as small as 229 at .050. After lash even smaller than the hr at 224 at . 050
I do not believe that to be accurate. You would need to contact the company on where the measurements are taken and if the lash is included and/or accounted for.
Edited for grammar and spelling
Last edited:
aaronk785
Well-Known Member
Could be. It would still be a good cam.
Cmanhattan
Member
Will look into. I’m guessing the LSA is still higher though unless it’s a custom grind. I understand what these gentlemen are saying about closing that angle to get more cylinder pressure. Is that not what they do with making rattler, thumpr and whiplash cams for low compression stock bottom ends?
Yes
aaronk785
Well-Known Member
Also look at the smallest lunati voodoo solid roller. Can’t beat the cam and lifter price.
-
