69 BB HP loss

[Paul K.]

How much horsepower would be lost from 2 1/2" exhaust verses a 2" exhaust,

Trying to decide if i should go to the 2" stock on my restoration or the 2 1/2"


Paul klemetson

[Russ S.]

Re: 69 BB HP loss

I don't know 69s real well but I believe I am correct in saying 2-1/2 is the stock exhaust on a BB

[Graeme B.]

Re: 69 BB HP loss

'69's used 2"

[Clem Z.]

Re: 69 BB HP loss

depends on the HP as i had a corvette buddy with a 67 435HP that replaced his GM side exhaust with after market and it killed the power where you could feel it at the higher RPMs.

[Joe C.]

Re: 69 BB HP loss

If it's a hydraulic cammed engine, I wouldn't worry about it. It's probably in the neighborhood of 7 -10 per cent when turning over 5000 RPM's. More important is what mufflers are on the car now, and what you're replacing them with.

[Dick W.]

Re: 69 BB HP loss

I cannot tell you, but when I removed the GM headers and 4" side exhaust from my L/88, it felt like I was dragging a ships anchor.

[Duke W.]

Re: 69 BB HP loss

The L-88 cam has extreme overlap and was specifically designed for headers and open exhaust, but Chevrolet left that up to the owner/racer. They had to install an exhaust system to drive it off the line and get it to the dealer.

That amount of overlap killed output with the OE exhaust, and it is my hunch that if you did a chassis dyno test of an OE as delivered L-71/72 and L-88 you would find that the former makes more torque/power over most of the rev range with the L-88 having only a very slight advantage over 5000 to 5500 RPM, but not much.

Now put headers and open exhaust on the L-88 and it will make over 100 more at the top end. The same racing exhaust system on the L-72/71 will narrow the difference to about 50.

Duke