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Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
T/Y Lars..and SolidLT1...But FWIW, desktop dyno, my machine shop, and I think I should have no problem making 500/500 at the crank with this combo. Hell, LS1 intake ports are over 200cc...lol, as well vortec ports are over 170cc...
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Heads are OK I have them on mine only the 64cc version, cam should peak in the 6500 RPM range and heads will support that. Big problem is the compression ratio as I see it should be at least 11:1 you could be less than 10:1. Race Demons also don't come in 850 CFM size to my knowlegde sure it's not a 950 ?
Properly set up you should be pulling near 400RWHP no problems, here's my dyno graph when I first dropped the 406ci in with no tuning, my old 2.5 in exhaust and the Holley 750DP on it, I only took it to 5000RPM's and only one pull just for fun as I had just dropped a replacement Super T10 in after I blew the original the first day with the new motor. With the 3 inch exhaust, new tranny, 825 Race Demon and some tuning I am looking for 450RWHP next time. Your dyno graph should look similar to this
Properly set up you should be pulling near 400RWHP no problems, here's my dyno graph when I first dropped the 406ci in with no tuning, my old 2.5 in exhaust and the Holley 750DP on it, I only took it to 5000RPM's and only one pull just for fun as I had just dropped a replacement Super T10 in after I blew the original the first day with the new motor. With the 3 inch exhaust, new tranny, 825 Race Demon and some tuning I am looking for 450RWHP next time. Your dyno graph should look similar to this
Last edited by MotorHead; Jul 21, 2005 at 02:21 PM.
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
I know the C/R is over 10:1...and the carb. may be an 825cfm. ...I respetfully disagree on the cam, as I spent alot of time with Crower on the selection....the specs aren't that radical.
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
Do you have the actual valve spring specs? Didn't see them on the webpage you posted.
What has me confused is the cam card lists a flat tappet spring. 140/340 lbs is not a high rpm roller spring. Why did crower put a flat tappet spring recommendation on a roller cam card?
What has me confused is the cam card lists a flat tappet spring. 140/340 lbs is not a high rpm roller spring. Why did crower put a flat tappet spring recommendation on a roller cam card?
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Couple of things, what is your jetting ? and 825 a wetflows something like 975CFM according to the boys an Barry Grant just FYI.
A quick way to see if you are in the ballpark is a sompression test you should be in the 200psi range if you are below 180psi you might want to look at boosting your compression. Also you stated you talked in length with Crower tech ? Did they mention a compression ratio for that cam ?
Just noticed about the springs too, I took the springs off that cam with my heads and got comp cams springs matched to my cam. The ones that came with heads for roller cams were in the 200# closed and 500# open range
A quick way to see if you are in the ballpark is a sompression test you should be in the 200psi range if you are below 180psi you might want to look at boosting your compression. Also you stated you talked in length with Crower tech ? Did they mention a compression ratio for that cam ?
Just noticed about the springs too, I took the springs off that cam with my heads and got comp cams springs matched to my cam. The ones that came with heads for roller cams were in the 200# closed and 500# open range
Last edited by MotorHead; Jul 21, 2005 at 02:53 PM.
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
I placed a call to Crower and Edelbrock...the valve springs are 210lb. on seat, 490lb. open...no answer from Crower yet on why the spring rate error on their cam card. BTW, I had dynoe'd the motor with my Holley 750 d/p'er and about the same numbers,(315hp.), so the B/G was an improvement.
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Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
210/490 sounds like a good spring for that cam.
Did you degree the cam when you installed it? Curious if the cam matches the card.
Compression test as mentioned above is a good suggestion. Also do a leak down to make sure everything is sealing.
Did you degree the cam when you installed it? Curious if the cam matches the card.
Compression test as mentioned above is a good suggestion. Also do a leak down to make sure everything is sealing.
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
I had it degreed by the machine shop, per cam grinders spec, (cloyes adjustable gearset). I remember getting about 160 psi cranking compression, with a gear reduction starter..(dry, no injected oil in cylinders)...I talked to Edelbrock today about my combo, they say I am at 10.2 c/r minimum. Still waiting for Crowers return call. I also faxed Edelbrock my dyno sheet. Their tech dept. will review it and advise me...
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
IN my humble opinion 160psi is no where near high enough for a high performance, high revving roller motor. You have all the parts there that some would drool over at a dragstrip, but someone did not do their homework when building the motor.
You have to match parts and while the springs will work they are probably a little stiff for that cam and will wear the valve train more than the correct springs. If that cam is a "street roller" then you can get away with much less spring pressure, but these things should be taken care of long before the motor is fired, sorry don't mean to be hard on you but you are asking for help here
You have to match parts and while the springs will work they are probably a little stiff for that cam and will wear the valve train more than the correct springs. If that cam is a "street roller" then you can get away with much less spring pressure, but these things should be taken care of long before the motor is fired, sorry don't mean to be hard on you but you are asking for help here
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
This engine was modeled after a build-up in Hot-Rod magazine. The cam and c/r are the same. I only deviated on the heads and intake..I will re-check the cranking compression tonight..The engine was set up for nominal rev limit of around 6200rpm.
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Nothing wrong with building a motor from magazines etc. They gave me good idea of what I wanted to build. 
You basically want cylinder pressure, it is a good thing in a hi-po motor, the more the better, the only limiting factor is the detonation/pinging point and the gas you can get to avoid the pinging. The bigger the cam the higher the initial compression ratio has to be to keep this cylinder pressure up because some pressure is lost in valve overlap.
My old 355ci was 230-235psi across the board, I am not sure what my 406ci is at, can't find my pressure tester at the moment
You basically want cylinder pressure, it is a good thing in a hi-po motor, the more the better, the only limiting factor is the detonation/pinging point and the gas you can get to avoid the pinging. The bigger the cam the higher the initial compression ratio has to be to keep this cylinder pressure up because some pressure is lost in valve overlap.
My old 355ci was 230-235psi across the board, I am not sure what my 406ci is at, can't find my pressure tester at the moment
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Ok, just got off the phone with David @Crower Cams....he sees NOTHING wrong with my parts mix, except he feels that the valve springs are too stiff for street use (I agree). The spring listed on the cam card y'all saw were for STREET driven cars. Ah Ha! Now, he thinks my cranking compression is too low....guess who's gonna pull a head and cc it? 
While I'm at it, I'll cc the piston surface. Crower feels I am at 10.2:1 now.
I still think I can get 420 rwhp with 10:1........the mystery continues.....
I found this interesting: http://www.pumaracing.co.uk/comp.htm
While I'm at it, I'll cc the piston surface. Crower feels I am at 10.2:1 now.
I still think I can get 420 rwhp with 10:1........the mystery continues.....
I found this interesting: http://www.pumaracing.co.uk/comp.htm
Last edited by big_G; Jul 21, 2005 at 09:03 PM.
Burning Brakes
Joined: Jul 2000
Posts: 1,118
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big G
FYI... The 3 chamber '50 series' mufflers flow more than the 40 series, 2 chamber variety. Doesn't matter a great deal, though, since neither one flows all that well anyway. Compare the specs to Dynomax Ultra Flo or some of the other straight pipe 'fiber packed' mufflers and the difference is significant. It made a noticeable difference on mine at higher rpm's, but went back to the 40's... just for the sound. The 40's seemed to make a seat-of-the-pants improvement at lower rpms (or was it just an extra 30 lbs/ft worth of noise?
). I'd be curious to know the difference with the system uncorked, as suggested.
http://www.dynomax.com/ultrafloweld.stm
FYI... The 3 chamber '50 series' mufflers flow more than the 40 series, 2 chamber variety. Doesn't matter a great deal, though, since neither one flows all that well anyway. Compare the specs to Dynomax Ultra Flo or some of the other straight pipe 'fiber packed' mufflers and the difference is significant. It made a noticeable difference on mine at higher rpm's, but went back to the 40's... just for the sound. The 40's seemed to make a seat-of-the-pants improvement at lower rpms (or was it just an extra 30 lbs/ft worth of noise?
). I'd be curious to know the difference with the system uncorked, as suggested. http://www.dynomax.com/ultrafloweld.stm
Safety Car
Joined: Jul 2002
Posts: 3,770
Likes: 3
From: St Louis MO
Originally Posted by big_G
Are there any nasty resonances?
Brett