[sheetmetal]

383 with a hydroroller, "NEW" (about 20 runs) MSD pro billet dist. locked out timing and digital 6 box. new crane billet timing set with edelbrock cast thick alluminum cover. cam button, build sheet says its set at .006. stock GM large internal balancer. at idle the timing moves about 2* back and forth. at 3000+ the mark advances 2* and jumps back and forth so quickly i cant really tell where my timing is set. could be anywhere from 36* to 39*. with the dist cap off, i can rotate the rotor almost 1/4" back and forth. im thinking this is just the clearance in the gears. the black finish on the dist. gear is just starting to rub the black finish off. any ideas whats going on and what do i need to do to get rock solid timing? thanks Dave

 

[SS_Dave]

I have read that the oil pump can cause a harmonic in the rotor of the distributor causing spark scatter. There are grooves you can grind in the internals of the pump to stop it.
I don't know exactly where, but maybe someone else will know. Thats the only think I can think of it could be.

Nice ETs BTW.

 

[slpin]

i think if you run 10s, its doing fine!!!

 

[hoffbug]

How is the contact pattern on your distributor gear? Did you have the collar machined off the distributor and a slip collar installed? This is sometimes necessary to get the proper engagement of the distributor and cam gears when there has been decking of the block and milling of the cylinder heads.

 

[kjett]

Are you running a bronze distributor gear? If so, check the gear for wear. Other things that might cause this are excessive chain stretch and excessive camshaft endplay. I've also noticed that higher spring pressures seem to affect the timing readings at lower RPMs. Does the timing still jump around at say 5k?

 

[Nickel333]

I had a similar problem a while back, its fixed now, but i cant remember exactly what caused it. I think it was somthing to do with my Mallory dist....give me a little while and it will come to me.

 

[pcs0snq]

Originally posted by sheetmetal:
383 with a hydroroller, "NEW" (about 20 runs) MSD pro billet dist. locked out timing and digital 6 box. new crane billet timing set with edelbrock cast thick alluminum cover. cam button, build sheet says its set at .006. stock GM large internal balancer. at idle the timing moves about 2* back and forth. at 3000+ the mark advances 2* and jumps back and forth so quickly i cant really tell where my timing is set. could be anywhere from 36* to 39*. with the dist cap off, i can rotate the rotor almost 1/4" back and forth. im thinking this is just the clearance in the gears. the black finish on the dist. gear is just starting to rub the black finish off. any ideas whats going on and what do i need to do to get rock solid timing? thanks Dave

Try a different timing light. A simple one like the Sears brand. I have a high dollar snap on and have the same issue with my MSD stuff. It may have something to do with the multiple spark feature

 

[sheetmetal]

the timing light is a sears NON dial back light. the dist. is a msd with the slip collar already machined for the slip collar. the contact patch looks good to me but what do i know. i called a dist. guru here in houston and will take him the dist. and see if he sees any thing. also MSD recommended the triger wire that comes out of the dist. not be near any high voltage wires. this i have done. keep the ideas coming guys. Thanks Dave

 

[Ron454]

Sounds like it's time to switch to a crank trigger set-up since you are running locked advance anyway.
I guess I wonder if after all the monkey motion of the timing chain and distributor gear movement you can ever get the timing rock solid.
Ron

 

[DragRacer]

Dave,

I had that same problem with my old large cap HEI. Timing would swing 4-6 degrees. When I switched to a MSD Pro Billet distributor the problem went away. In fact, timing was so steady I could set timing in 1/2 degree increments. I ran locked timing in both. This was on my old solid roller combo with decent spring pressure and a small base circle cam.

One thing to check is make sure you are not binding up the distributor shaft. In other words make sure your slip collar is adjusted properly and you are binding the cam gear into the oil pump when you tighten down the distributor.

Does your distributor rotate freely and not "catch" when you spin it 360 degrees?

 

[thrasher]

Damn these guys are good
Not a lot to add.

Good stuff guys

Probably not a factor but distributor shaft play

Should be .010-.015

 

[sheetmetal]

heres how i set the dist. up. I dropped the dist. in with the collar loose and no gasket till it bottomed out, then tightend the collar. removed the dist. and lowered the collar .020 and tighten the collar and added the gasket. im not sure how to check for binding. do i need to pull the dist out and check or is there some way to check binding with it in the engine? im checking into a crank trigger but not sure this will fix the problem if the problem is a binding issue or a tolarance problem.

 

[baddbob71]

You might be too tight with .020 considering what most gasket thicknesses are. The oil pump only has about .003 gear clearance and if any pressure is there it may be causing more cavitation? Just guessing but I wouldn't want any down pressure on the pump gear. Maybe add another gasket and verify that isn't the problem.

 

[ddeennis]

msd.......3 sparks under 3000 rpms and one single long spark in the upper rpms......hhhmmmmmm wonder if that has anything to do with it.....

 

[Motor Martyr]

dave here is a picture of the regulator line routing for your regulator.
The left rubber hose is "in" the braided is "out" and the bottom is the return.

Thats my friend larry's car.

this car is going 10.70's now on this setup.