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PRH
Well-Known Member
A suggestion I’d make is.......
It sounds like the car is running and the OP has driven it around already.
I’d do the basic easy stuff first.
Make sure the timing, jetting, lifter preload is all correct.
Do a compression test on a couple cylinders.
Then before tearing anything apart....... get it on a chassis dyno, or take it to the track for some numbers so you can establish a real “baseline”.
Most chassis dyno shops will have some sort of “no tuning” deal where they’ll strap the car on and make 2-3 pulls for $100.
That’s a good place to start.
I’d suggest a place with a dyno jet, since there are tons of runs to look at from that type of dyno, and they seem to have less variation from dyno jet to dyno jet.
It sounds like the car is running and the OP has driven it around already.
I’d do the basic easy stuff first.
Make sure the timing, jetting, lifter preload is all correct.
Do a compression test on a couple cylinders.
Then before tearing anything apart....... get it on a chassis dyno, or take it to the track for some numbers so you can establish a real “baseline”.
Most chassis dyno shops will have some sort of “no tuning” deal where they’ll strap the car on and make 2-3 pulls for $100.
That’s a good place to start.
I’d suggest a place with a dyno jet, since there are tons of runs to look at from that type of dyno, and they seem to have less variation from dyno jet to dyno jet.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I got about the same engine except it's a 3.58 stroke. She went 93 in the Eighth at 3467 pounds and at 900 ft elevation, and on 87E10.............. with 3.55s.
My ace in the hole is the 3.09 low gear that adds 16% TM (TorqueMultiplication) over the 2.66 factory gear, turning the 3.55s into 4.12s. If you have a 2.47 low-gear box, yur toast with 3.73s, cuz 2.47x3.73=9.21 versus my 3.09x3.55=10.97
My combo is happy with 3.23x3.09=9.98.
But your 340 with that cam is torque-challenged, so I would stick with a starter gear of ~11/1 which calls for 11/2.66=4.14s, or 11/2.47=4.45, making the average dead on 4.30s....... just like YR said.
If you go 4.30s , that will increase your launch-TM by 4.3/3.73=plus 23%, so your engine will sorta feel 23% bigger. If your engine currently feels like a 273 at launch, now it will feel like a 340,lol.
But there's more; all your shifts will come sooner in mph, so you will be putting down more average horsepower over distance, and that is what you are not feeling.
If you're not willing to go into the 4.xx ratios, then you have two options; 1) a bigger engine, or 2) an engine that thinks it's bigger at normal street speeds. And the latter usually means an earlier closing intake valve to trap more cylinder pressure. There are a few ways to do that... a hydro cam with faster ramps,a smaller hydro cam, or a fast-ramp solid-lifter cam.
93 in the Eighth, Mr. Wallace translates to 115 in the quarter, which could be just into the 11s.
I hear the guys harping on degreeing the cam, and they are NOT wrong.
But my experience, as a streeter, with the three cams I have moved around, is this; with street gears and street tires and a manual trans; it makes almost no difference where the centerline is, within +/- 4*. With 3.73s your 340 should burn right thru first gear to over 50 mph, and second will take you to 70@6000. So you have a window of opportunity to time the improvement of 20 mph, which is less than 2 seconds. You'll never see that accurately repeatable on a stopwatch.
I said almost no difference because; even if you were out by 4 degrees, the pressure difference is a tic over 4 psi on the cranking cylinder pressure, and the power peak might move 50 rpm. So, because you burned right thru first gear, who cares if the cam is out. And in second gear, who cares about cylinder pressure in a streeter, with 3.73s cuz;50mph is ~4300rpm, right on or near the torque-peak and your butt dyno cannot feel a 4ftlb difference. So that just leaves the run from 50 to 70, and the 50 rpm change is only gonna make a few hp difference at peak on a combo like yours; you won't feel that either.
The only way to measure an improvement is to track test it, with a timer, and minimal tirespin.
And besides; changing the cam-timing just trades high-rpm power, for low-rpm power. and vice versa. It ain't much, and with a clutch, you can compensate for the loss on the start-line.
What you can't compensate for is lack of cylinder pressure and lack of TM, at low speed, around town. Here, torque is King, and the right starter gear makes all the difference.
Ok but having said that, if you installed the timing gearset with just one tooth out, yeah you'll feel that lol. But I've never heard of anybody doing that....... besides me,lol.
You can check the cam installed centerline without removing the entire front end, but it's nearly as much work on a SBM. You can check the Split-Overlap at the lifters. It's not as accurate,maybe, but it will put you very close. Close enough to prove the dots were dot-to-dot.....or not,lol.
A 4* lack of ignition timing can lose more power than 4 degrees of cam advance lost. And too much timing, causing detonation will kill power too...... so prove your timing.
FYI;
My combo has a 230/237/110 cam. And yes, I feel it is bigger than I need. But it is so much fun. My previous cam was a 223/230/110 and I liked it better. The 3.55s were the gear of choice with both, buut; recall my trans has the 3.09 Commando gearset. The gears are all different except the M/S first, so you can't just swap the gears;you need a set.
The ratios are:
3.09-1.92-1.40-1.00; versus
2.66-1.91-1.39-1.00; versus
2.47-1.77-1.34-1.00
My ace in the hole is the 3.09 low gear that adds 16% TM (TorqueMultiplication) over the 2.66 factory gear, turning the 3.55s into 4.12s. If you have a 2.47 low-gear box, yur toast with 3.73s, cuz 2.47x3.73=9.21 versus my 3.09x3.55=10.97
My combo is happy with 3.23x3.09=9.98.
But your 340 with that cam is torque-challenged, so I would stick with a starter gear of ~11/1 which calls for 11/2.66=4.14s, or 11/2.47=4.45, making the average dead on 4.30s....... just like YR said.
If you go 4.30s , that will increase your launch-TM by 4.3/3.73=plus 23%, so your engine will sorta feel 23% bigger. If your engine currently feels like a 273 at launch, now it will feel like a 340,lol.
But there's more; all your shifts will come sooner in mph, so you will be putting down more average horsepower over distance, and that is what you are not feeling.
If you're not willing to go into the 4.xx ratios, then you have two options; 1) a bigger engine, or 2) an engine that thinks it's bigger at normal street speeds. And the latter usually means an earlier closing intake valve to trap more cylinder pressure. There are a few ways to do that... a hydro cam with faster ramps,a smaller hydro cam, or a fast-ramp solid-lifter cam.
93 in the Eighth, Mr. Wallace translates to 115 in the quarter, which could be just into the 11s.
I hear the guys harping on degreeing the cam, and they are NOT wrong.
But my experience, as a streeter, with the three cams I have moved around, is this; with street gears and street tires and a manual trans; it makes almost no difference where the centerline is, within +/- 4*. With 3.73s your 340 should burn right thru first gear to over 50 mph, and second will take you to 70@6000. So you have a window of opportunity to time the improvement of 20 mph, which is less than 2 seconds. You'll never see that accurately repeatable on a stopwatch.
I said almost no difference because; even if you were out by 4 degrees, the pressure difference is a tic over 4 psi on the cranking cylinder pressure, and the power peak might move 50 rpm. So, because you burned right thru first gear, who cares if the cam is out. And in second gear, who cares about cylinder pressure in a streeter, with 3.73s cuz;50mph is ~4300rpm, right on or near the torque-peak and your butt dyno cannot feel a 4ftlb difference. So that just leaves the run from 50 to 70, and the 50 rpm change is only gonna make a few hp difference at peak on a combo like yours; you won't feel that either.
The only way to measure an improvement is to track test it, with a timer, and minimal tirespin.
And besides; changing the cam-timing just trades high-rpm power, for low-rpm power. and vice versa. It ain't much, and with a clutch, you can compensate for the loss on the start-line.
What you can't compensate for is lack of cylinder pressure and lack of TM, at low speed, around town. Here, torque is King, and the right starter gear makes all the difference.
Ok but having said that, if you installed the timing gearset with just one tooth out, yeah you'll feel that lol. But I've never heard of anybody doing that....... besides me,lol.
You can check the cam installed centerline without removing the entire front end, but it's nearly as much work on a SBM. You can check the Split-Overlap at the lifters. It's not as accurate,maybe, but it will put you very close. Close enough to prove the dots were dot-to-dot.....or not,lol.
A 4* lack of ignition timing can lose more power than 4 degrees of cam advance lost. And too much timing, causing detonation will kill power too...... so prove your timing.
FYI;
My combo has a 230/237/110 cam. And yes, I feel it is bigger than I need. But it is so much fun. My previous cam was a 223/230/110 and I liked it better. The 3.55s were the gear of choice with both, buut; recall my trans has the 3.09 Commando gearset. The gears are all different except the M/S first, so you can't just swap the gears;you need a set.
The ratios are:
3.09-1.92-1.40-1.00; versus
2.66-1.91-1.39-1.00; versus
2.47-1.77-1.34-1.00
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OP, that cam, [email protected] should work in the 2-6 / 2200/6200 rpm range. With the 340 & rpm heads and intake, power should hold on passed 6K for sure.
Degree the cam, it is important.
Degree the cam, it is important.
3406pk
Well-Known Member
Hughes usually provides instructions to degree tne cam with every cam they sell. I bought 2 cams and instruction came with. It is explained really well , but you will need timing chain set that has advance and retard keyways if it needs changing. How much preload did you set for lifters, did you follow Hughes recommendation?
disco
Daddy Dave
Thanks again everyone, it's very interesting reading your thoughts on this, the cam was installed at the machine shop and I'm not sure if he degreed it, the springs and lifters were what was required by the cam card, because I used the Hughes 1.6 roller rockers the machine shop had to measure and send Hughes the numbers to make the pushrods.
disco
Daddy Dave
Could someone tell me what OP means lol
Original Poster..........as in the person who started the thread
disco
Daddy Dave
Thanks
nm9stheham
Well-Known Member
FWIW, it looks like this is the OP's cam:
Hughes SEH3236AL-8
Hughes Engines
2800+ recommended stall on the TC
Hughes recommended valve spring is their 1129 on their cam card. Dual coils, no damper, taller to be used with Edelbrock heads. So that basically sounds in line. Seems like it ought to go well past 6000 with this. (Can't recall if the Edelbrock spring seats meet this requirement noted for these springs but probably does. "Note: Spring base must be machined flat on OEM heads. Both springs must set on the same surface." )
Hughes SEH3236AL-8
Hughes Engines
2800+ recommended stall on the TC
Hughes recommended valve spring is their 1129 on their cam card. Dual coils, no damper, taller to be used with Edelbrock heads. So that basically sounds in line. Seems like it ought to go well past 6000 with this. (Can't recall if the Edelbrock spring seats meet this requirement noted for these springs but probably does. "Note: Spring base must be machined flat on OEM heads. Both springs must set on the same surface." )
yellow rose
Overnight Sensation
If the machine shop didn't degree the cam, I'd never set foot in there again.
You'd be surprised how many shops I've dealt with who can't degree a cam. I know this because their junk came through my shop and the cam timing would be off. Never trust a shop that doesn't itemize the assembly bill. I always gave a total (which started at a grand and went up from there depending on how big a PITA it was) and then called out what it cost to degree the cam, how many times I had to do a mock assembly, what the EXACT, MEASURED compression ratio is, what the exact, measured piston to valve clearance is and last but not least, where the intake lobe was center lined. Then there is no question about if the cam was degreed or not. Every single engine I assemble get the cam degreed. It's not a option. The customer has no say.
Wyrmrider
Well-Known Member
and degreeing asymmetrical cams- several vendors do it different
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
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I have the HFT version HE3037AL, 230/237/110 lifts of .549/.571 with 1.6 arms. Great cam. I shift it at 7000 all the time with those 1129s on my Eddies, but with a lifter preload of just 1/2 turn, and all the oiling mods save for the crossover.
As a streeter, the 295 BFGs never stop spinning below the speed limit so... I can't tell where the power peaks exactly. So because it pulls the way it does, I just let her buck. With 3.55s, 65 mph is 5500 in second gear, and the tires are still spinning, so I really don't care where the power peak is,lol. Not bragging on the combo; jus saying, at 180psi or more cranking cylinder pressure, that's a great tire-frying cam.
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