Expert: Dan Liddy - 4/20/2009

Question
i wrote and asked you a question about my motor not pulling vacuum would a ported and polished intake make a difference. also would a freshly built motor that hasnr run very long pull vacuum it has only run long enough to break in the cam......we were adjusting the timing and the oil pressure dropped to 5 lbs.... im really frustrated now can you help me?

Answer
Hi again Damon;

Oil pressure though, depends upon RPM, if it was idling at say 600 RPM , 5 Lbs. of OP isn't all that far off, I'd rather see 10 but - - - However, if the OP drops to 5 PSI when running at 2000 or 3000 RPM< that's different, and it indicates that there's an internal problem.
I'm sorry to say this , but it sounds like you have some major problems.  A new motor that loses oil pressure is BAD- -  take it apart and find out why, before running it any more- - you run the chance of destroying a new crankshaft and the rest of it.  The crank assembly (rods bearings , mains and the crank itself)  need to be measured by a machinist for proper clearances.

Porting and polishing make no difference in the amount of vacuum it will pull. Leakage around the piston rings and/or the valves will. Also poorly fit gaskets below the carburetor and intake manifolds.

The disassembly will also give you the opportunity to find why you're not getting vacuum.

What kind of racing are you trying to do with this anyway ?, it would help me to know that.

Good luck

Dan Liddy
Sarasota, Florida