71 Cutlass

MSD distributor, no box, just "ready to run" for Oldsmobile. I decided to remove the dist. in order to get at the stop bushing. The standard stop bushing has 21 degrees (approx) of centrifugal advance. There is a larger bushing , which I installed, that allows for 18 degrees of advance.With 10.5:1 compression I'm running just about 15 degrees initial. I thought I could add a degree or two of initial since the overall timing would be lowered after switching the bushing, and gain a little HP without adding to my pinging problem from high CR and pump gas. The exact opposite occured. Car went slower off the line and seem to have less torque. I am clueless as to why. So I lowered the initial back from 17 to 15. Car went faster. Lowered it to 13, car went even faster. Lowered it to 11, car goes even faster. Haven't lowered it less yet b/c I'm sick of working on both cars all day and yard work. This is totally odd to me. If I had just gone out and only retarded the timing on the car 4 degrees to 11 and done nothing else, it would go slower, yet somehow after all of this, and running 11 degrees of initial and less centrifugal advance it runs about the same before I did anything to the car. Can anyone explain this?

MDchanic

So you're saying that you went from 36° total (15° + 21°) to 29° total (11° + 18°), and retarding it those 7° made it go faster?

Have you measured your totals with a timing light?

Could you be doing something backwards (stop bushing in wrong, etc.)?

- Eric

71 Cutlass

Yep, 36 to 29. It's virtually impossible to put a stop bushing in wrong...one comes off another goes on. Timing light (Now reading 29-30) told the tale after several "runs" around the block.. I simply do not understand the results, other than the fact higher compression likes less timing, but that has typically not been the tale of my car.

ah64pilot

I don't think your compression is as high as you think it is. What are you basing your number off of?

71 Cutlass

Typical procedure, already knew bore & stroke, what pistons were being used,etc. and other variables, just waited for headwork to be totally finished and did the "math." Even without the standard porcedures it's obvious based on the engine's behavior that the engine is over 10:1. I've since turned the timing back up to 15 initial and left the mech. advance at 18. For whatever reason car runs fine now.