Dyno GURUS- performance analysis questions/comments please!!
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
Dyno GURUS- performance analysis questions/comments please!!
After doing some analysis on the dyno run this past Sat, I know that there is some work to do on the motor. The PEAK hp of 348 was achieved at 4800 rpm's... power dropped big time after 4800.
This motor, dynoed in a couple articles (March 2000 Chevy High Performance and another one) with the same camshaft had PEAK power at 5400 rpms...
I think the module in the HEI unit needs to be switched out with the performance one that I have (the Proform HEI that I bought initially).
Aren't stock HEI modules good only to 4500 rpms?? That's what might be in there considering how it performed.
Also, Keith stated that he "may" have heard valve float (over 5500rpms) which tells me that I probably should have gone with the stronger springs from Comp Cams... He also mentioned that I should check the rocker arm adjustments as well...
The cam's power range- 1800-6000. See signature for cam specs...
When I bought the cam, I went with the "standard" 924 valve springs. In the Comp Cams catalog, the "premium" choice were the 930 springs with a significantly higher spring rate. That said, does anyone think I should switch to the higher rate springs??
I would appreciate any comments/ideas/advice!!!!
Bob
This motor, dynoed in a couple articles (March 2000 Chevy High Performance and another one) with the same camshaft had PEAK power at 5400 rpms...
I think the module in the HEI unit needs to be switched out with the performance one that I have (the Proform HEI that I bought initially).
Aren't stock HEI modules good only to 4500 rpms?? That's what might be in there considering how it performed.
Also, Keith stated that he "may" have heard valve float (over 5500rpms) which tells me that I probably should have gone with the stronger springs from Comp Cams... He also mentioned that I should check the rocker arm adjustments as well...
The cam's power range- 1800-6000. See signature for cam specs...
When I bought the cam, I went with the "standard" 924 valve springs. In the Comp Cams catalog, the "premium" choice were the 930 springs with a significantly higher spring rate. That said, does anyone think I should switch to the higher rate springs??
I would appreciate any comments/ideas/advice!!!!
Bob
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
The 4500 rpm limit for the HEI is a myth. A stock HEI in good condition will have no problem firing upto 6000.
I need to see the dyno sheet in order to give suggestions. Valve float is often easy to spot on the dyno curve.
I need to see the dyno sheet in order to give suggestions. Valve float is often easy to spot on the dyno curve.
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
Originally Posted by lostpatrolman
Do you have the dynosheet? If so, post it up!
I do have the dyno files- I had to download software from www.dynojet.com
There must be a way to post it up as a jpeg with all the runs together....
I will work on it!
Bob
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Can you post a graph with your best run power, torque and AFR (if you have it)?
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
Originally Posted by zwede
Can you post a graph with your best run power, torque and AFR (if you have it)?
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
Check this link out. I will try to get the conditions on there.... It was probably 90 degrees, 10% humidty or so....
http://www.geocities.com/bobt1974/Dy...?1116427646894
Thanks.
Bob
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Bob, I was trying to research your motor parts. I could not find your manifold type. The 850 carb, heads, and exhaust system is not holding you back. I tried to also look up your 924 springs on the comp cams page. I could not find any info on them. I’ve seen some late model Vettes on dyno runs and because they were using Hydroroller cams. You would see an abrupt drop off when they went into valve float in the 6300-6500 rpm range. What are your spring specs?
Unless the HEI cap coil is old and going into breakdown. HEI’s with new plugs and wires are good to sub 6500.
Unless the HEI cap coil is old and going into breakdown. HEI’s with new plugs and wires are good to sub 6500.
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
Originally Posted by zwede
Can you post a graph with your best run power, torque and AFR (if you have it)?
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
Originally Posted by zwede
Can you post a graph with your best run power, torque and AFR (if you have it)?
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
Last run is interesting. Doesn't quite look like valve float although that is a possibility. Looks kind of like it ran out of fuel. But the AFR data would tell us real quick.
To see the KEY (dyno run color chart) see:
http://www.geocities.com/bobt1974/Dy...?1116444786213
Last edited by Bob Turner; May 18, 2005 at 03:31 PM.
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Can you tell us what was done between the runs? AFR is different between them and you gained 100 hp so what all was done?
Doesn't look like fuel starvation. Valve float is a possibility. AFR curve is pretty bumpy. I'm used to seeing them smoother than this.
Doesn't look like fuel starvation. Valve float is a possibility. AFR curve is pretty bumpy. I'm used to seeing them smoother than this.