5/19/03

QUESTION 1

Scott,

I am running a 454 with a solid roller cam. I am looking for any type of secret valve lash techniques which may help me. The compression has been knocked down to about 9.5:1 to 1:1. I am running a tunnel ram with a single 750 Speed Demon, which I am looking to swap to a 815 Mighty Demon. For now, I am running a 3.5:1 ring and a 28-inch tire. I am also looking to swap in its place a set of 4.3:1 gears. Any tuning tips would be appreciated.

Rat Pack

Dear Rat Pack,

I always start with the manufacturer's recommended valve lash settings and tune from there. Increasing the lash increases bottom end power, and decreasing the lash increases top end power.

Your compression ratio may be hurting your tunnel ram's efficiency. Remember that a tunnel ram likes higher rpm, so the gear swap will be good. The bigger carb will help, too.

Scott

QUESTION 2

Scott,

I am running a Chevy 355 with World Products heads, 2.02 valves, 200 runners, 58 cc chambers, a Comp Cam 12-614-5, .585 lift intake, .588 exhaust, and flat top JE pistons with 6-inch Oliver rods. I'm also using a Weiand X-cellerator intake and Holley 750 carb.

ADVERTISEMENT

For some reason, I cannot get more than 6500 rpm out of the engine. Once it gets to 6500, it won't climb any more.

I'm running 5:13 gears with 32-inch slicks. I'm trying to get into the 10.90 class, but can't get better than 11.75.

I need all the help I can get.

Thanks.

Bill

Dear Bill,

Lack of rpm is usually related to one of two areas: induction or valve train. I am quite familiar with the 10.90 class using a 355 engine. Here are my recommendations.

Your 750 cfm carb will work just fine and your solid lifter cam will also do the job. The X-cellerator manifold is rated for 2000-6500 rpm -- you need more.

A Weiand Team "G" #7531 or GM Bowtie will work great. Use a 2-inch spacer between the carb and the manifold.

You need to check your valve spring pressures. A solid lifter cam like yours works well with 150-165 lbs. seat psi and 450-500 lbs. at max lift.

I hope this helps.

Scott

 

To contact Scott Walker write morehorses@racingnetsource.com