HELP PLEASE! Timing jumps after being set with timing light! Causing Overheating!

[91RS84TA]

Okay so I did a 305 to 350 Swap (Rebuild from 73' chevelle) on my 1991 RS, and were hopefully wraping up the swap. PROBLEM!!! My mechanic keeps setting the proper timing to the car but he says it keeps jumping after being set on its own. We did new plugs, correct firing order with new wires (Accell), and lined up everything with first spark plug and everything. He sets it using the timing light and then it will jump from i believe he said 12 degrees to 20 degrees. Don't quote me on that because im not sure of the exact numbers. Installed a new fan and thermostat yesterday, still climbs to 220 degrees. The coolant is flowing but the reservoir looked like a guyser after driving it for 5 minutes very easy. Maybe my distributor from the 305? Or my module? Maybe both? Help PLease?

[bubba428]

sounds like to hold own bolt is loose...I would start with checking that...

[Pampered-Z]

When you refer to jumping, it it advancing after being set to the initial DGs so that you actually have to move the distributor to retard the timing back repeatedly? Make sure you double check the timing after you tighten down the dist. They can move a bit when you snug them down.

You must disconnect the advance before setting the timing and that should be around 6 DGs BTDC. when you reconnect the wire for the ECM to control the spark advance is should immediately add a few degress of timing. Should be a single wire plug I think along the fire wall by the brake booster?

Make sure when you set the timing you scribe a line to verify the distributor it's moving. If you timing is still changing/advancing then I'm look into the Ign module/pick-up.

Also check that there isn't excessive play in the rotor / distributor that would be a sign of a possible bad cam or dist. gear. Are you running a cam that requires a bronze gear?

Is the idle staying stable?

[91RS84TA]

Well the idle is fine after he moves the distributor to where its not to retard and the motor can turn over with just a click and no hesitation. I guess we need to disconnect the advance. I will also tell him to check to see if there is play in the rotor. Thanks A mill! Going to check on the car on my lunch brake, I'll let you guys know whats going on as soon as i get back.

[91RS84TA]

the hold down bolt is loose? No prob, guess we'll check that too. Thanks

[Pampered-Z]

the hold down bolt is loose? No prob, guess we'll check that too. Thanks


You should not be able to move the dissy once the bolt is tightened down. If the bolt is loose find a new mechanic!

[S.J.SLEEPER]

overheating/boiling over may be that the engine is airbound.
you need to put a coolant funnel on radiator and fill with fluid. let car idle w/ heat blower on high . also if you didn't drill a small hole in thermostat you should. it helps let the air escape and also keeps engine a tad coole by allowing small flow of coolant even when thermo closed.
car should idle at start up. if engine is reved this will not help the air pocket get out, it will make it spit out all over