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Drifting
Joined: Nov 2004
Posts: 1,971
Likes: 7
From: Longwood Florida
A few things to consider. I ran a rather large solid roller cam on my old camaro. I did not have the same heads. I ran Dart sportsman IIs with 64cc with small dome piston block was not decked. Should have been about 11.1
BUT
The cam was large enough that it had overlap that bled off the compression. Lots of duration and short lope seperation will do this.
ALSO... something that nobody has mentioned is the type of dyno you used? Mustang or Dyno jet? They do vary about 10%
And the TYPE OF TRANNY YOU HAVE.
**Notice** Motor Head runs a manual Trans....He will dyno more than you if you run a auto with a stall converter? Not to mention he does have a slightly larger motor.
Hey the car runs a good times at 12.4 that is a great for a street car! Your 60ft is awesome 1.6 ? thats with slicks or drag radials I am guessing.
BUT
The cam was large enough that it had overlap that bled off the compression. Lots of duration and short lope seperation will do this.
ALSO... something that nobody has mentioned is the type of dyno you used? Mustang or Dyno jet? They do vary about 10%
And the TYPE OF TRANNY YOU HAVE.
**Notice** Motor Head runs a manual Trans....He will dyno more than you if you run a auto with a stall converter? Not to mention he does have a slightly larger motor.
Hey the car runs a good times at 12.4 that is a great for a street car! Your 60ft is awesome 1.6 ? thats with slicks or drag radials I am guessing.
Team Owner
Joined: May 2001
Posts: 29,745
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Originally Posted by big_G
Opinions on poor dyno performance...388, 6 in. rods, 10.3 cr., Edelbrock race heads, BG race demon 850, Edelbrock Super Victor intake, Aeromotive 140 g.p.h. pump thru 1/2 in. line, 2.5 in. duals with flowmasters, Hooker Supercomp. headers, Richmond 5 speed, Crane hi-6 ignition, 36 deg. total in by 2500rpm. I am expecting 400+hp, 400+lb/ft.
http://photobucket.com/albums/b156/b...t=scan0001.jpg
http://photobucket.com/albums/b156/b...t=scan0001.jpg
You have a HUGE carb - and a big single plane intake and big open headers but then you are dumping into 2 1/2 exhaust ??? That should be a 3" minimum.
Also, you went BIG with this engine. Big "race heads" - probably 210 - 220 CC intake runners. A carb and intake that are more suited for a 502 than a 383. Compression is good, but what cam are you running?? With this combo I would expect a solid lifter "bracket race" cam that didn't make power until 3500 and had a 7500 RPM red line. Or a roller cam with the same specs.
What is the cam that you are using? My guess is that all your components are WAY TOO BIG for street use. You can keep all the above and if you have the right cam and fix the exhaust you should be in the 500 HP+ range --- at the track. If it's street driving you want, go down to a 650 CFM carb, dual plane intake, heads with a 195 - 200 CC intake and step the headers down to 1 5/8" runners.
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Cam is the following: Level 2 street/strip solid roller, 7,500 redline. http://photobucket.com/albums/b156/b...t=scan0001.jpg
Team Owner
Joined: May 2001
Posts: 29,745
Likes: 3
From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
I still think 2 1/2" exhaust on this is a choker above 4500 RPM. Should be 3" or better. Try a dyno run with the exhaust unhooked from the headers.
You get this tuned right and it should be a screamer on the strip. I don't think it will be much fun to drive in stop and go traffic, but on the track it will be a monster.
I hope you have plans for a stronger rear end and getting some drag radials.
You get this tuned right and it should be a screamer on the strip. I don't think it will be much fun to drive in stop and go traffic, but on the track it will be a monster.
I hope you have plans for a stronger rear end and getting some drag radials.
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
You can't race dynos, go run the car at the strip and come back with some real world numbers to go by. I still say heads are WAY TOO BIG for a 383 combination that needs a wide powerband. AFR 190cc heads would have been better to use, did you pick out combination? or did machine shop help? The one "quick fix" would be a RPM air-gap if your motor is "soft" in the 2500-4000RPM range. Many here are "experts" on motor design, I only know what works for me after spending some time in a machine shop and building Chevy motors for over 25 years and I say your heads are too big. Here is a Chevy High Perfirmance magazine article of a 180cc intake runner 406cu/in Chevy that made about 500HP with "small port heads" Big ports are great for Drag racing, Nextel Cup restrictor plate engines and other applications but, NOT! for all around good performance in a "street/strip" automobile. Here is a link: http://chevyhiperformance.com/techar.../148_0401_imp/
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
First off the bat: this is a purpose built STRIP engine. Second:The parts selected for this build were based on conversations with the machine shop I use, Edelbrock and Crower tech. departments. . They are all better at selecting parts than I am. If the heads were too big, why then the power drop-off at 5,200 rpm? BTW, if you look at the dyno chart on the Chevy performance link, you will see that the H.P. is on the way down at 5800 rpm, possibly indicating the limits of the heads. I figure with a 383, some benefit can be obtained with a larger intake port. Keep in mind these are UNPORTED heads...
Last edited by big_G; Jul 22, 2005 at 01:38 PM.
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Originally Posted by big_G
First off the bat: this is a purpose built STRIP engine.
And this all goes back to my original question: Why are you running low compression on a strip motor? Once you get into big runners, single planes and long duration cams you NEED compression to make it work. This combo would scream at 11.5-12 CR. Yes you'd need race gas but it's not much of a street combo anyway.
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Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
So, I am losing 100HP by giving up 1 compression point? Sorry I did not mention that earlier. This was a strip car that I will be using occasionally on the street!...lol
Last edited by big_G; Jul 22, 2005 at 01:41 PM.
Advanced
Joined: Mar 2002
Posts: 60
Likes: 0
From: Ashburn VA
I think your combo is fine, more compression would help make some more power, but not the problem being so far down on power. Have you run the Pressure test yet? that's a great test to check for compression, bent valves, etc.. Also is the balancer new? If not check and make sure the timing groove has not shifted. Im thinking you have 2-3 areas that are leaving 20-30 hp each on the table and adding up.
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 will support 575-600HP or into the 450RWHP range out of the box, if those heads are the part number you posted, looking at the the dyno chart you would think heads might be the problem but not with those heads. Do they have "Edelbrock VIc Jr" stamped on the front of them ? Something else is making the power drop off 
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
The balancer is fine. I spoke with my machinist this morning, he said my cranking compression (160-170) is appropriate for my cam's profile. He also mentioned that my rich (11:1) fuel mix is costing me some...
Team Owner
Joined: Jul 2001
Posts: 182,997
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From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
Originally Posted by lars
If those are chassis dyno numbers (330 hp), you're getting 400 net horsepower, in spite of your rich mixture. 400 net is about 450 - 460 gross. I don't think you're doing too bad.
I've never seen such low loss, except for engines rated for a specific car and that were on the engine dyno WITH accessories hooked up.. Most crate engines are not dynoed with accessories..The accessory and exhaust loss alond is very likely over 10% and then additional 15 - 20% loss through the drivetrain... I can't see how the total accessory and drivetrain loss would be below 25% unless all electrical accessories are used...
IMHO - 400 RWHP translates to about 530 flywheel HP with MT and 540+ HP with AT...
Last edited by GrandSportC3; Jul 22, 2005 at 02:43 PM.
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
I think that the 2.5 inch exhaust is too small for that kind of setup..
Running open headers should make a huge difference..
Running open headers should make a huge difference..
Drifting
Joined: Nov 2004
Posts: 1,971
Likes: 7
From: Longwood Florida
5 things to TRY! in this order.
1. Pull valve covers and check push rods and rockers (valve lash for your solid cam is ?)
2. check compression on each piston (within 5-10%)
3. re-dyno with open headers.
4. re-dyno with open headers and 750 carb... try and get fuel mixture to 13-14.7 (if no 750 go down in jets from 80s to 72 front and 76 rears)
5. re-dyno with timing light and vaacum gauge.
You should come up in power 10% that is about 30hp. That dyno time may be expensive but it will help find you problems.
**Other things to spend money on is shave the heads and mild port job. That should give you about 25-30HP. If you are doing the strip thing you need to go 3.73 or 4.11 on the gears.
1. Pull valve covers and check push rods and rockers (valve lash for your solid cam is ?)
2. check compression on each piston (within 5-10%)
3. re-dyno with open headers.
4. re-dyno with open headers and 750 carb... try and get fuel mixture to 13-14.7 (if no 750 go down in jets from 80s to 72 front and 76 rears)
5. re-dyno with timing light and vaacum gauge.
You should come up in power 10% that is about 30hp. That dyno time may be expensive but it will help find you problems.
**Other things to spend money on is shave the heads and mild port job. That should give you about 25-30HP. If you are doing the strip thing you need to go 3.73 or 4.11 on the gears.
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
another thing.. Check if you are actually getting WOT... It's a common problem with the stock throttle and gas pedal assemblies that there's a chance that you are not getting WOT...
Thread Starter
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
1: Lash and compression #'s fine
2: Tried dyno runs with both a 750DP and B/G 825 Race Demon, B/G was 10hp. better
3: I am running Richmond 5 speed, dyno pull is in 4th gear (Math equates to 4:56 final drive in 4th)
4: I plan on re-jetting, along with open-headers next trip to dyno...
2: Tried dyno runs with both a 750DP and B/G 825 Race Demon, B/G was 10hp. better
3: I am running Richmond 5 speed, dyno pull is in 4th gear (Math equates to 4:56 final drive in 4th)
4: I plan on re-jetting, along with open-headers next trip to dyno...
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
Are you running a mechanical fan??
If you do, that's 10+ RWHP right there..
It gained about 12 RWHP when I took the mech. fan off..
If you do, that's 10+ RWHP right there..
It gained about 12 RWHP when I took the mech. fan off..