Cam Suggested Compression Ratios..

[F-BIRD'88]

I agree... Something does not add up and he is looking for someone to agree with his ill fated plan.

I agree on the pistons and new AFR heads too. It will not be a bolt on.

[Stan Weiss]

F-Bird, I clearly understand what he wrote. I am asking him, the topic starter why he would do this or settle for this. I've read through his posts, not interested in anyone elses posts. I would like to hear this from him, rather than others taking pop shots at what might be going on in his own mind.

The situation is about that simple.. I have a 454 that has 12:1 with a pair of Edelbrock heads that I have somewhat "outgrown" or so it seams. I won't go into details but discussions with Larry Meaux raised a few clues from his formula and my real dyno sheets (BSFC in particular) that suggests that this was the case. Those Edelbrock heads have ~106cc chambers after 0.043" milling, and I feel thiat milling them was a mistake. I really don't want to mill the new heads.
The new heads, AFRs that I am looking at buying have 113cc chambers. If I simply bolt these new heads on, I will go from 12 to 11.15:1 and am concerned that power may be (overly) adversely affected. I am well aware of the advantages of a high comp ratio, which is why I want to maintain the 12:1 I built into this engine in the first place.
My question is how much the lower ratio will hurt that cam's ability to make it's intended power and will if hurt that cams ability and do more harm than simply expect 3% less from the missing point..
The car is a street car on pump gas (and water injection) that would probably be happier with the lower comp from a "streetable" point of view.. As mentioned, the superior flow of these new heads should (should!) make up that 3% and then some, or of course, I'd be wasting my time.
If I need to maintain the 12:1, that's fine, but it means a new set of custom pistons and down where I am, that's easily $1500 plus rings and balancing etc on top of the head swap.

I tried a DCR formula on Wallace Racing's website but there is no input for LSA. http://www.wallaceracing.com/dynamic-cr.php
Slightly more to the story is I have gone from a Crane 138101 with a 110° LSA to their 138801 that has a 106° LSA to help move this heavy car. (The previous 138101 was damaged when a roller lifter failed, and thought this was a good time to reconsider my cam choice.)
Comparing those two cams is almost no different in the Dynamic results as their LSAs are not considered.
http://www.compcams.com/Technical/FAQ/LSAproperties.asp
Is there a more detailed calculator out there?

What would LSA be needed to calculate DCR?

Stan

[Stan Weiss]

1. PG shows a tenth quicker than a TH400 on Maxracesoftware ET Analyst. See quotes below, we've already covered this in another thread..
2. Those heads do not flow as much as required, hense the swap.
3. Given the weight of the car, gearing and intended max rpm, that cam was chosen. This stock LS7 bottom end is not going to 8000.
4. Yes, I am well aware that it is below it's potential, see #2.
5. Air con, power steering, power windows, full interior, plenty of sound deadening/insulation, all steel, me (170lbs), fuel.

@ 4000lbs the power glide is killing you.
You are really doing it the hard way by ignoreing that and chasing power to reduce the ET.
You need leverlage to get 4000 lbs moving. The 1.76 gear is not enough of a lever.
Get a th 350 or th 400 trans..
The heads you have can be improved with some work.
If your car was 2300lbs the glide would work. But its not. It is leaving like a snale
with that trans. And its still going to leave like a snail even if you improve the heads flow.
Get a 3 speed or loose 1000++lbs.

Using the existing 570hp540tq engine, PG (1.76/1:1), 5200 converter, 4.56 gears, tire dia and 4000lb race weight..
60ft 1.631. 10.90/125.57.
No changes except for the addition of a TH400 (2.48/1.48/1:1), same shift points launch rpms, weight and so on.
60ft 1.617 10.988 / 125.39
Better 60fts but nearly a tenth slower overall.
Edit: numerically lower rear gear to ~3.9 results in quicker 10.916 than the 4.56 gears, but at a slower 124.85 ..and still slower than the 'Glide on both.
That's on Larry's MaxRaceSoftware ET Analyst program.

So unless I see real gains and not actually going backwards, I'm not going the effort and expense on a TH400..

Not sure of the parameters that you use with Larry's software. What was the weather / DA used?

Stan

[BlackoutSteve]

Well, let's see if this answers your questions.. My convoluted story is as follows..
(Bear in mind that the opening post of this thread simply asks about cam recomended comp ratios, and can the 138801 cam work with one point less than suggested..
The rest of this story has been asked for, or bits and pieces required if felt relevant, and I very much appreciate your interest and help. I am certainly not here to waste my time or yours by spinning BS for who knows what reason. I will however, answer the questions as best I can in order to receive the help I obviously need, and I do sincerely appreciate it. )

The car went from 3660lbs to 4000lbs during a 9 year restoration where several things were added to the car. A/C and sound deadening for example.
During that restoration, I removed the 134781 flat tappet and fitted the 138101 roller, recomended by Crane as a replacement, in hope for what they suggested would be an additional 40-60hp more.
While the car was being restored, the engine was dynoed with the roller and produced the dyno sheet previously posted. Yes, that's the pull that yielded the best results with the best tune. As already stated, I was disappointed with the results and I was told tat that time that the heads were assumed to be the reason.
The water injection system had not been installed or even purchased at that time. In fact, at that time, I had only just decided that I couldn't be bothered with the high octane carry and mixing as I had done for years before, With some enquiring, I found that the H2O was a better choice (especially finacially) than swapping to low-comp/pump-friendly pistons and then the domino effect of having to change cam, converter, gears etc as a result.. Like I said, the H2O works and call it a Band-Aid if you want to. I guess it is.

The pre-restoration results of 122 mph and 3660lbs had an et of 11.49, about 1/2 a second off what the 122 deserved I guess. The 60fts were lame and I put that down to the 3500 converter as it never felt strong off the line. Sure, a 2.48:1 low gear would help, but, post engine dyno, a 5200 converter was suggested by several which confirmed what I thought about the 3500 being the reason and not so much the trans..
I had always thought and expected that a TH400 would be a better choice after going with the 'Glide near 20 years ago. I had seen heavy BB cars at the track and most/all with TH400s.. So, during the resoration, I reconsidered my transmission choice and the said program showed me that the results were roughly on par with each other and not worth the trouble/effort or expense, so the 'Glide stayed. Yes, the results surprised me, but who was I to disaggree?

[BlackoutSteve]

The motor never got damaged. There is nothing wrong with the engine apart from a poor combination of recomended parts. It's currently out and all apart and just about everything can go straight back in. It cranked 225psi and I remember leak down also being very good.

The Edelbrock 60459 heads are out of the box with the exception of the said milling and the spring seats were cut to accept larger diameter Isky ToolRoom springs.
For example, those heads' flow numbers at 0.400" and 0.600" are 250 and 309 cfm. The highly recomended AFR's with the same sized port (290cc) flow 294 and 361 at those same valve lifts. (Yes, I'm considering the yet to be released 300cc Magnums which flow just slightly more.)
So, does that point to the Edelbrock Performer RPMs being the cause of not getting the reasonable power expectations of 630-650 @ 6500? http://www.edelbrock.com/automotive_new ... sion.shtml
I bought those heads over 15 years ago and they were a reasonable choice given what was out there at the time. No regrets.

I have found out that the "Edelbrock domes" can work with open chamber heads-including AFR's, but not the other way around ie: an open chamber dome in those Edelbrock heads.
So, IF the lower 11.15 comp ratio will be OK, then the pistons can stay. Yes, I am reluctant in swapping cams after recently buying a replacement 138101, then taking it back to swap for a 138801 after it was suggested for the tight LSA.
Perhaps I will talk to the recomended cam guy and see what his suggestion is. It will be interesting to see how different/what differences the "right" cam will be to what I have in hand.

Q: Why would LSA be needed to calculate DCR?
A: I just expected that the LSA would have an effect on DCR because it changes cylinder pressure which is what the compression does also..?
The weather perameters were the same for both trans comparisons. Probably 600ft, 29.92, 80°F and 60% hum.. The program's defailt I think.

Hope that story doesn't ask more questions that it answers.

[Strange Magic]

The *Edelbrock Performer line of products in my opinion is geared or target marketed for the street enthusiast who wants some bling first and foremost and who might want to replace his old school oem items with some new items in aluminum. On a secondary note, some will take advantage of slight performance gains as is and some might not take advantage of any gains other than weight reduction. Dependant on the application.

With this said above, your cylinder to cylinder head testing, with all things equal, should give you sizable gains.

To re-instate or re-assure your thought about moving LSA from 112 to 110 is a move in the correct direction and in my opinion that 112 should have never been in there in the first place, even with one point higher compression than what your new build will be with the AFR's.

Just a suggestion: DO NOT TAKE ANYONES WORD ON WEATHER A DOME WILL FIT PROPERLY WHEN MAKING A SWITCH FROM HEAD TO HEAD. YOU HAVE THE ADVANTAGE TO PHISICALLY CHECK THIS BECAUSE YOUR ENGINE IS APART AS MENTIONED.

* In the right hands, much of the Performer line of cylinder heads can be re-worked in all areas whereas the gains are substantial.

[pdq67]

Dodge,

They still do sell race fuel here in cental MO at the pumps.

It's called E85!

pdq67

[Stan Weiss]

Q: Why would LSA be needed to calculate DCR?
A: I just expected that the LSA would have an effect on DCR because it changes cylinder pressure which is what the compression does also..?
The weather perameters were the same for both trans comparisons. Probably 600ft, 29.92, 80°F and 60% hum.. The program's defailt I think.

Hope that story doesn't ask more questions that it answers.

LSA could have an effect in that it changes ICL which changes IVC. That is why I ask for seat-to-seat IVC. If I have the same lobes changed from a 106 LSA to a 113 LSA and advance the 113 LSA cam 7 degrees my ICL and IVC are the same as the 106 LSA installed at 106 ICL and so is my DCR>

Stan

COMPGAUG.GIF

[F-BIRD'88]

You need to rebuild this motor @10.50:1 so it will run on pump gas.

The AFR heads will likely work great. Reguardless.

Get a th-350 th-400 and a different camshaft. The 12:1 cr is not doing anything good for you.

You could have a PUMP GAS 11.00 high 10's street car with the right rework. But not with the PG.

I see a minimum of 4/10th improvement just by swapping trans. I prefer a th350.
But since you added 400 LBS to the car, you will be lucky to even run the same as before.

as you turned the 11.49 ET into 12.00 or slower, with the added weight.

Plus a bit of street/track chassis tuning magic. It will never leave hard with a glide.
Do not expect change, without changing any thing. To go fast, you might consider that.
Other than that, you'll need a ton more horsepower and a big pot of money.

Like said, the AFRs will not be a bolt on.
Like said the Edelbrocks can be improved a lot, in the right hands.
(were those flow numbers yours or advertized?) Is there any thing funky about the marine versions? (valve job etc)

Adding 400lbs to the car will cost you 4/10th ET. You are obviously not serious about going fast.

You had and still have a very convoluted plan with some very bad engineering and conflicting goals.
But nitrous will fix anything.

[Stan Weiss]

At 4000 lbs. with below - Green HP - blue torque from dyno sheet. Red HP - Yellow Torque based on weather and altitude used for acceleration simulation.

Stan

PG
60 Foot ET = 1.66
330 Foot ET = 4.62
1/8 Mile ET = 7.15
1/8 Mile MPH = 97.46
1000 Foot ET = 9.32
1/4 Mile ET = 11.13
1/4 Mile MPH = 124.99

T400
60 Foot ET = 1.47
330 Foot ET = 4.35
1/8 Mile ET = 6.82
1/8 Mile MPH = 99.10
1000 Foot ET = 8.96
1/4 Mile ET = 10.76
1/4 Mile MPH = 125.88

T400 - Limited traction
60 Foot ET = 1.65
330 Foot ET = 4.57
1/8 Mile ET = 7.05
1/8 Mile MPH = 98.80
1000 Foot ET = 9.20
1/4 Mile ET = 11.00
1/4 Mile MPH = 125.72

ab-BlackoutSteve-HP-TQ.gif

[Strange Magic]

Stan, are those your time slips from a turbo 400 to powerglide test?

[BlackoutSteve]

Thanks Stan, those are the results I expected to see..
The 'Glide will stay for the moment.. The TH400 will most likely come with the time and cash.

F-Bird, The car is an additional 300lbs and like I said, it's a street car. My partner is partially disabled. She comes with me on many road trips and cruises and I am serious about keeping her a bit more comfortable for hours on end than worring too much about 3 tenths of a second that the weight from A/C and sound deadening would have added.
Larry's maxracesoftware must have a lot of explaining to do if my car in now a high 11/low 12 as you suggest.
The 'Glide now has 4.56 over 4.11s and a 5200 converter over a 3500, so there will be improvements in that lame 11.49 ET. ..and don't worry, the TH400 will come.

I dummy assemble the engine at least once and will plasticine the chambers. (but I still haven't made a piston decision yet)
(The cam was a 110° and is now a 106°.)

No E85 down here.

[Stan Weiss]

At 4000 lbs. with below - Green HP - blue torque from dyno sheet. Red HP - Yellow Torque based on weather and altitude used for acceleration simulation.

Stan

Stan, are those your time slips from a turbo 400 to powerglide test?

Those are from computer simulations. It would be interesting if someone had real time slips.

Stan

[BlackoutSteve]

Those are from computer simulations. It would be interesting if someone had real time slips.

Stan

Maybe I might. ...soon.

[Strange Magic]

I just wasn't sure if they where actual time slips or we where just playing footsie.