I have been trying to set my timing to the performance specs and something is just not right with my setup. My distributor is a billet ProForm HEI unit that is about a year/1000 miles old. In trying to get the 36 degree before 3000rpm setting, I have to have my initial timing set at almost 20 degrees and it causes all kinds of hot start issues. I changed out the springs to the lightest springs in the Mr. Gasket kit and still get almost no advance when spooling the rpms up. Is there anything I can do/change/adjust on this unit to make it have more centrifugal advance? Also, I am getting 5-6 degrees of timing scatter with this unit, I have shimmed the distributor to .008 endplay and still get lots of scatter. I am starting to suspect the timing chain, but the engine only has 5000 miles on it total since the last rebuild, is it possible the chain has stretched in this amount of time?

Thanks,
Chris

 

Timing chain shouldn't have stretched much at all with that little run in, unless it was a POS to start with. It sounds like you need to do some more work on the distributor. Are you sure the advance mechanism is working? Doesn't sound like it. It should do better than 16*

 

It seems like it is working, it moves freely by hand when I have the cap off and snaps right back when I let go of it.

 

Take the springs completely off and set your total....then work backwards for your curve.

 

I'm not familiar with your distributor but did you leave the stock weights in or did you use the ones from the Mr Gasket kit?If you used the Gasket weights they might be limiting your timing.

 

I kept the weights in the distributor that came with it. They are the larger weights and are like the originals. I tossed the Mr. gasket ones as they didnt appear to be as beefy as the ones that were currently in the distributor. I have been messing with it more this afternoon. I am getting LOTS of timing scatter when trying to adjust the timing, so I am not even sure what number I am getting anymore.

 

Scatter meaning timing mark bouncing around?Wonder if the combination of the stock weights and light springs could be allowing the timing to bounce.Have you tried the Gasket weights and springs?Just a thought.Also is there a limit bushing in your dist.?

 

Yep, it bounces around like crazy, I switched the springs back out and put the springs that came with the distributor back in it, they are a little more stiff than the lightest springs in the Mr. Gasket kit, this allows my initial timing to come down a little, so I guess even at 800 rpm the light Mr. gasket springs are advancing. Revving the engine with the vac. advance unplugged shows to be shifting back and forth about 3-4 degrees, then with the advance plugged in, it shifts back and forth about 5-6 degrees. I isolated my #1 wire away from all the other wires and make sure the clamp on my timing gun was facing the plug correctly and I am still having the issue. Im stumped, is there a way to tell if the timing chain is loose without pulling the front cover?

 

No EASY way I know of to check the chain.I would imagine that would be tough to get an accurate check.Have you checked to see that the dist gear is not worn or the gear is loose on the shaft?Some cams take a special gear.

 

PUll the dizzy, note the roll pin and position of dimple on gear, with ralationship to the rotor button, knock out the roll pin, and take dizzy shaft outta housing....maybe have to knock it out with a hammer due to crap on the shaft....
clean everything up, I soak in gasoline, then spary with carb cleaner, make damn sure everyone is clean and happy, including removal of the vac advance plate and canister....make sure canister is fresh....

lube up nicely, plenty of engine oil into the top bearing lube cloth there seen when you pop off the advance plate....get all the dried grease outta there....

Bet odds you have a plastic bushing around the limit tab (s) on the centrifugal advance mechanism....install those two top sections together, and play with it to make sure they are all nice and free working....a dap of WD40 up there make them happy for years....

re assemble with particular attention to end play, shim with washers on bottom as necessary, you want it to be about ten-20 mils....plenty at that, no more.....

pay attention to the gear orientation again obviously, and then slip that puppy back in there with one light spring, one heavy spring...near stock, maybe a bit lighter....and leave the vac advance line off/disconnected....
set idle for desired speed ~800 rpm or so....set advance to 36 @3000 rpm, check idle advance, should be around ten or so....no more than 12 or your hot start will suck donkey nutz.....

the above fixes every one I have ever worked on....YMMV....

 

To check for worn chain.

Take dist cap off.
Rotate engine a little by hand with 5/8" ratchet or wrench in counterclockwise direction.
Now rotate engine the other way.
Note if there is any delay in the rotor turning vs the crank.
If there is a delay, you have a loose timing chain.

 

I used to have some issues like that and I decided to do something about it. I switched to MSD. I can tailor my exact timing with the included bushings and springs,(how much and how fast) very easily and have great spark to boot!!!.It is idiot proof for us that are more into the body work aspect of things,and not so much into reinventing the theory of relativity