Chassis Dyno results: Comments?
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 3,281
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From: NC USA
Chassis Dyno results: Comments?
Put the car on a chassis dyno this weekend and did 3 pulls. The best pull was the first one with the following results at ~5800RPM:
RWHP=303 :confused: RWT=415ftlbs Fuel mixture=12
The dyno tech told me that I needed a better cam to 'wake up' the 454's hp and told me that the torque would improve also and air/fuel mixture #s were good already. Since this engine is supposed to have 425hp at the flywheel, even allowing ~18% for the driveline/IRS should be about 350hp which is what I expected to see. Why would the hp be so low? My current 'mystery' hydraulic flat tappet cam is mild since it has no lopey sound and idles smoothly at 750rpm
My engine details minus cam info are in my sig.
RWHP=303 :confused: RWT=415ftlbs Fuel mixture=12
The dyno tech told me that I needed a better cam to 'wake up' the 454's hp and told me that the torque would improve also and air/fuel mixture #s were good already. Since this engine is supposed to have 425hp at the flywheel, even allowing ~18% for the driveline/IRS should be about 350hp which is what I expected to see. Why would the hp be so low? My current 'mystery' hydraulic flat tappet cam is mild since it has no lopey sound and idles smoothly at 750rpm
My engine details minus cam info are in my sig.
Melting Slicks
Joined: Apr 2000
Posts: 3,286
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From: San Jose California
Re: Chassis Dyno results: Comments? (Marks69BB)
Sometimes problems can be simple. Are you sure the linkage opened the throttle all the way? I would agree that a cam change would also make a great difference.
Funny how a beautiful and powerful car seems less so when you get actual numbers. Makes you wonder how much fantasy everyone else's numbers must have factored in. I would expect that your honest 303 horse power would still be more than enough to serve up many 450-500 hp cars on a plate!
Chuck
Funny how a beautiful and powerful car seems less so when you get actual numbers. Makes you wonder how much fantasy everyone else's numbers must have factored in. I would expect that your honest 303 horse power would still be more than enough to serve up many 450-500 hp cars on a plate!
Chuck
Pro
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From: Madison AL
Re: Chassis Dyno results: Comments? (Marks69BB)
That does sound low. Sounds like maybe you have a mild truck cam in there. Are those chambered pipes restrictive? Exhaust can make a huge difference on a car too.
Drifting
Joined: Oct 2001
Posts: 1,699
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From: Westampton NJ
Re: Chassis Dyno results: Comments? (69Roadster)
Yeah, that sounds low as that's how much my 350 is putting out RWHP. Of course, from the sound and RPM range of my car...there is a very healthy cam in my car...and probably more internal mods that I don't know about.
Race Director
Joined: Apr 1999
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From: NM
Re: Chassis Dyno results: Comments? (Marks69BB)
Don't forget that 425 hp in '69 was GROSS hp, not the NET hp that is used today. Also crate engines that have HP ratings are rated at GROSS hp. There are several ways to guess the NET output (and I am sure some will post them shortly) but I would guessitmate the NET to be about 350-365. Then looking at 303hp at the rear wheels does not look so bad.
tom...
[Modified by Tom73, 12:27 PM 11/5/2001]
tom...
[Modified by Tom73, 12:27 PM 11/5/2001]
Thread Starter
Melting Slicks
Joined: Jun 2001
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From: NC USA
Re: Chassis Dyno results: Comments? (69Roadster)
Chuck - It's honest but it was somewhat embarassing since mine was the only BB there and all of the C5s (including 2 Z06s) that were there put down more hp but none were close with the torque! I have been thinking about a cam but wanted to dyno it first to see what I've got to start with. BTW, best pull of the day was a modded 01 Z06 with 374hp/368ftlbs!
69Roadster - Yeah, I've been thinking also that the chambered system is hurting me but didn't think that it would be a problem with an engine under 450hp. Anyway, I've got a set of Hooker sidepipes lined up to go on and the chambered system will be history this winter.
Anyone else?
[Modified by Marks69BB, 4:55 PM 11/5/2001]
69Roadster - Yeah, I've been thinking also that the chambered system is hurting me but didn't think that it would be a problem with an engine under 450hp. Anyway, I've got a set of Hooker sidepipes lined up to go on and the chambered system will be history this winter.
Anyone else?
[Modified by Marks69BB, 4:55 PM 11/5/2001]
Team Owner
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Chassis Dyno results: Comments? (Marks69BB)
What intake do you have that matches your big heads. I assume that you went with 2.20+ & 1.88 valves. The only other factors would be the lower compression and mild cam of a crate motor.
Maybe a big block person will chime in, but max hp at 5800 hp sounds high for a mild cam. It might be out of whack because of high flow heads though.
Maybe a big block person will chime in, but max hp at 5800 hp sounds high for a mild cam. It might be out of whack because of high flow heads though.
Burning Brakes
Joined: Dec 1999
Posts: 924
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From: Houston Texas
Re: Chassis Dyno results: Comments? (gkull)
How about this: The tech did not anchored your car properly, and due to the excessive torque of your engine the rear wheels slipped on the drum.....giving you a low reading. After tying down C5's all day with less than 370lbs. of torque....what do you expect? :D :D :D
[Modified by 81vette, 1:05 PM 11/5/2001]
[Modified by 81vette, 1:05 PM 11/5/2001]
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Drifting
Joined: Mar 2001
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From: Indiana
Re: Chassis Dyno results: Comments? (Marks69BB)
The numbers are correct if you calculate the loss correctly. You will lose 15% from gross to net and then you must also subtract the 15-18% for drivetrain loss. Using to these numbers, you should be between 296rwhp(for 15% driveline loss) and 307rwhp(for 18% driveline loss).
[Modified by tsw71, 11:36 AM 11/5/2001]
[Modified by tsw71, 11:36 AM 11/5/2001]
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 3,281
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From: NC USA
Re: Chassis Dyno results: Comments? (gkull)
gkull - I have a factory hi-rise alum intake with rectangular ports that came with the crate engine that the serial # shows was originally made for the 71/72 454/425 Camaro with the ram-air hood.
[Modified by Marks69BB, 4:57 PM 11/5/2001]
[Modified by Marks69BB, 4:57 PM 11/5/2001]
Race Director
Joined: Apr 1999
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From: NM
Re: Chassis Dyno results: Comments? (Marks69BB)
gkull -the crate engine that the serial # shows was originally made for the 71/72 454/425 Camaro with the ram-air hood.
tom...
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From: Reno Nevada
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Re: Chassis Dyno results: Comments? (Marks69BB)
Mark - That is a nice intake. If you have everything else dialed in the cam is the last thing. It's to bad you don't have a spec sheet on the cam. I've figured out a unknown cam before with a dial indicator and it's a PITA to get real numbers .050 not just like the big advertised duration and lift. Nearly every cam has a part number on the front that can be referenced
Thread Starter
Melting Slicks
Joined: Jun 2001
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From: NC USA
Re: Chassis Dyno results: Comments? (Tom73)
Tom73 - The GM serial # on the intake is 6269318 which I posted earlier in Factory Correct forum and was told by the # gurus that it was originally made for the 72 454/425 Camaro engine application.
gkull - Appreciate your comments. It frustrates me that I have all of the other 'good stuff' and am not putting out the hp one would expect with this combination! :confused: Would I just have to replace the cam with a hydraulic or solid roller or would I have to also go to roller rockers? What about valves? Current intake valve size in the heads is 2.19 and exhaust is 1.88; should I have the heads done and go to a larger intake valve size?
71coupe - I have a graph but it is in paper form so I'd have to scan it and don't have a scanner. I'm waiting on the shop to email me an electronic file of it and then I could post it.
[Modified by Marks69BB, 2:59 PM 11/5/2001]
gkull - Appreciate your comments. It frustrates me that I have all of the other 'good stuff' and am not putting out the hp one would expect with this combination! :confused: Would I just have to replace the cam with a hydraulic or solid roller or would I have to also go to roller rockers? What about valves? Current intake valve size in the heads is 2.19 and exhaust is 1.88; should I have the heads done and go to a larger intake valve size?
71coupe - I have a graph but it is in paper form so I'd have to scan it and don't have a scanner. I'm waiting on the shop to email me an electronic file of it and then I could post it.
[Modified by Marks69BB, 2:59 PM 11/5/2001]
Race Director
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From: NM
Re: Chassis Dyno results: Comments? (Marks69BB)
Tom73 - The GM serial # on the intake is 6269318 which I posted earlier in Factory Correct forum and was told by the # gurus that it was originally made for the 72 454/425 Camaro engine application.
tom...
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From: Reno Nevada
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Re: Chassis Dyno results: Comments? (Marks69BB)
Any way you look at it full roller cams are about $1200 Solid flat tappet cams are a good alternative. You can buy hydro flat tappet cams for up to mid grade performance. But IMO hot high revving big duration ones make your car only sound like a race car and have all kinds of drivability issues.
On the question of bigger valves. If your heads are ported and polished for a certian valve size larger valves do not automatically give you more flow. At some point stock rec ports have flow limitations.
On the question of bigger valves. If your heads are ported and polished for a certian valve size larger valves do not automatically give you more flow. At some point stock rec ports have flow limitations.