How much HP do i have

[Steven A.]

I have talked with the previous owner of my car. When it was totally body-off restored and the 396 rebuilt; it was fitted with hardened seats and quote, "the compression was lowered from 11:1 to about 9.5:1" in order to run pump gas. Everything else remains factory stock. It is obvious from the way it runs and sounds that it still has a performance cam, solid lifters, etc. Given his statement is accurate; what has that done to my horsepower?

Steve Allison
50236

[Bill B.]

Re: How much HP do i have

Steven - I have found on Comp Cams website CamQuench 6 its a free 2 minute download you can put in all your engines information and by changing the compression instantly you can see the peak horsepower and peak torque change. Just a suggestion and a good learning tool.

Good luck,
Bill

1961 Black/Silver/Red Int. 283/315 FI
power windows. Frame off 65% completed.
1989 hard top daily driver 165,000 miles

[Bill M.]

Re: How much HP do i have

Steve:

When GM dropped the compression ratio in the LT-1 from 11.0 to 9.0, the gross went from 370 to 330, about 11%. Lets use 3/4 of 11% for 9.5. 425 - 8% = 391.

[Joe R.]

Re: How much HP do i have

Steve,

Why not run the car on a chassis dyno to see how much rear wheel horsepower (RWHP) you really have? From that you can estimate what the engine hp is. I don't remember the factor offhand, but I've seen it here. I can dig it up if you're interested.

Joe

[Joe C.]

Re: How much HP do i have

I have talked with the previous owner of my car. When it was totally body-off restored and the 396 rebuilt; it was fitted with hardened seats and quote, "the compression was lowered from 11:1 to about 9.5:1" in order to run pump gas. Everything else remains factory stock. It is obvious from the way it runs and sounds that it still has a performance cam, solid lifters, etc. Given his statement is accurate; what has that done to my horsepower?

Steve Allison
50236

Bill is right. In addition, keep in mind that the old fashioned horsepower numbers, prior to 1972 were inflated (gross). If you want to correlate your pre 1972 engine's horsepower figures to modern standards (ie 638 GM estimate 2009 ZR1), then you would deduct an additional 12 per cent, to end up with 344 net HP. Keep in mind that this number is not fixed, but tied to the point where torque dropoff begins to exceed RPM rise. What it means is that across the board, you should expect an average 11 per cent torque deficit with the lowered SCR.

[Ken A.]

Re: How much HP do i have

I have talked with the previous owner of my car. When it was totally body-off restored and the 396 rebuilt; it was fitted with hardened seats and quote, "the compression was lowered from 11:1 to about 9.5:1" in order to run pump gas. Everything else remains factory stock. It is obvious from the way it runs and sounds that it still has a performance cam, solid lifters, etc. Given his statement is accurate; what has that done to my horsepower?

Steve Allison
50236

Never enough!