Hey Geo ( 4 webbers ),
I know there are roller tip rockers out there that will fit under stock big block valve covers but I forget who the heck makes them. Do you know who makes them? Also, if the car is basically an under 5500 engine, will the roller tips actually do any good or should I just go to a higher ratio? Alas, yet another question. I have asked this to about 6 people and got 9 different answers....a street driven vehicle with power steering, air conditioning, etc etc and a 4 speed with say a 450 gross hp engine in it....what SHOULD it dyno at the rear wheels? My stock 390 gross dynos 245 rear wheel ( that has got to be low ) and drops from 460 gross to 350 foot lbs of torque. What is your best guess as to what it actually should be? I guess a better way to put the question is this...what percentage of power should be lost from gross to net to rear wheels?
Thanks.

Glenns,
The number that everyone seems to use is 18% for manual and 20% for auto. I don't beleive that I have ever seen a number for Gross Vs. Net. My guess would be another 5%.
There is alot of controversity concerning how accurate the Chassis Dyno's really are. I had some acticles on this subject, buy deleted them form my favorites. If I remember the biggest flaw discussed was on the numbers they use doing the coast down. Don't get overly concerned about the low numbers. Most people are using the Dyno to evaluate changes they make to their Cars.
I noticed that we are located very close to each other. Which Dyno did you use? I have made several runs in Pottstown at High Street Speed. My numbers for my SB were 265hp, which seemed low for my engine combination and how the Car performs.
I thought about using Second Street Speed to compare the numbers to each other for curiously.
Dutch

Hiya Dutch,
The only time the car has been dynoed was last year at Carlisle. I have no idea what brand name it was. All I know is that it was a chassis dyno and my HP numbers sucked ! What I keep hearing is you lose 15-20 % from gross to net and another 15-20 % from net to the rear wheels. I am actually losing about 35% total off the rated gross.

|UPDATED|6/11/2002 10:07:46 PM|/UPDATED|

Let's see, that means that out of your gross of 390 HP, you have approximately 253.5 rear wheel hp. My vette is supposed to be rated on rear wheel HP. The factory specs are 195 HP. It doesn't seem right , does it? I have no Idea what the dyno would say.


|QUOTE|glenns said: Hiya Dutch,
The only time the car has been dynoed was last year at Carlisle. I have no idea what brand name it was. All I know is that it was a chassis dyno and my HP numbers sucked ! What I keep hearing is you lose 15-20 % from gross to net and another 15-20 % from net to the rear wheels. I am actually losing about 35% total off the rated gross.


|/QUOTE|

blk,
To the best of my knowledge I don't know of any Car thats Horse Power is rated at the rear wheels.
There is just too many variables to do it. Auto Vs. Manual, Ac equipped or gears ratios,etc.
The difference between your 79 and glenns car is his was gross rated and your is brake rated both at the flywheel.
Your hp numbers are what the engine will produce in a normall equipped car.
I had some Web sites that would explain the difference far better than i ever could. I will see if I can find them again and post them. I do know that I have learned a ton of knowledge at http://www.chevytalk.com/
Dutch

Glen,
You math is pretty good. I dynoed at 245 hp and 350 torque. Personally i would think it should be around 300 to 310 hp but who am I? My new engine BETTER do between 380-410 rear wheel hp with about 400 torque or I am wasting a bunch of bucks.

Guys,
I like many was under the impression that Chassis Dynos test results were the final reality check on rear HP & torque cor your car. I am now not so sure. read the articles at the below sites and tell us what you think!
Dutch
http://www.sdsefi.com/techdyno.htm
http://www.pumaracing.co.uk/power3.htm

This may be better veiwed as a new post.

|UPDATED|6/19/2002 6:29:43 PM|/UPDATED|