Distributer Timing way off gm spec
 

1979 Trans Am 301 engine original HEI distributer. note; after purchasing I did a tune and the timing was already set in the below described advanced setting.

have never been here: engine placard calls for 12 deg initial timing. in setting it there it acts severely retarded, runs but chugs. so I advance it on the timing mark
14-16-18-20-24 no to very little improvement. I go back to way advanced off the timing marks (see yellow tape pic) where it was and it runs good. -but- overheats on the highway no doubt due to the advanced timing. runs cool in town.

removed the cap today and the weights and all are crusty as this car sat mostly for 10 years. found the connector to the module barely secured and thought this would be the issue. nope. sprayed some wd40 and cleaned up inside. new cap/rotor/wires/plugs.

using the timing light I noticed it was getting advance but does not appear to be enough as to what im used to. (my 455 with dui has 24 degrees advance at 3,000 rpm.) also when moving the advance weights by hand they seem much stiffer than the dui.

I just installed an oem 4 row copper brass radiator in place of the tiny 301 original radiator that was plugged up. it overheated prior on the highway, the big new radiator is masking the problem and at least maintains 220 on the highway now. cool no issue in town.

tried to lay all the info out there, need some help on where to look with the distributer. oh, I had an old flame thrower module I installed to test. engine would not even start. back to the gm module and started but back to the problem. is the gm module bad? any help greatly appreciated I am very curious as to what the heck this is.

Have you pulled all the spark plugs out and removed the cap such that you can see the rotor move, rocked the balancer back & forth so you can check how much play there is in the timing chain?

If not then that is your next move.

And while your doing that verify that the balancer mark is at TDC when the piston is at the top of the cylinder. It's possible the balancer has spun on the hub. I'd bet It's one of these and that's why the car was parked.

There is nothing to spin on a 301 crank hub.

Order a distributor.

so no slip or spin possible on the 301? glad to hear that.

if the timing chain slipped that much would it still be running as good as it is?

one vote for it being the distributer.

Thank you!

1st see where the #1 cylinder is at TDC, and where the rotor is pointing at?
(should be #1 plug wire)


Are you using #1 plug wire for timing?
(driver side front plug)


:confused:

Did you disconnect the vacuum advance when you set the base timing and verify that that it it’s working?

Remove distributor. Take it completely apart for cleaning and lube. Photo 1--Chevy distributor shown, Pontiac similar.

First Guess: Reluctor/timer core/armature is seizing on the main shaft. Photo 2--Polish shaft, fill groove in main shaft with white grease. Also refresh lube under plastic seal beneath pickup coil, and assure that the distributor housing drilled holes that lube the upper bushing are not plugged with hardened grease.

Verify weights/pivot holes, pivot pins/bushings, springs, and vacuum advance. Many vacuum advance canisters have WAY too much travel, they can be replaced or the existing vacuum advance canister can have it's travel restricted.



Getting the distributor advance to work properly should help.

The GM module may or may not be "bad". If the engine runs with it, it's worth investigating further...AFTER you've fixed the distributor.

If the key shears, the entire hub can spin on the crank snout.

Not at all common...but theoretically possible.

Maybe if you are using a key made of chinesium.

Or the damper/hub bolt isn't properly tightened.

have a new DUI hei from summit on the way. I will be swapping out the 301 this winter with a PONTIAC 350 and wanted it for the new engine. I will be going thru the original distributor as shurkey suggested as I think this is the issue. it feels very gummed up. I want to keep it with the 301 engine. I want to cure this issue before the swap as the 301 runs great and I will be fixing its rear main leak as well. want it in good to go condition while on a stand in storage for the future. 47,000 original miles.

I don't think the 301 has enough grunt to break even a paper hub keyway.

I have had 10 pontiacs, numerous engines and have never ran across this kind of timing issue. yes checking the timing correctly. I did see another distributor post questioning the timing light. I had an electronic one once and it was horrible, really whacky readings. went back to my sears timing light of old and still works great.

I have learned the caveat to a low milage car. this one was drivin 1,000 miles in the last 10 years. zero rust, like new interior, even the t top seals are terrific. but.....when sitting internal corrosion effects a lot of mechanical items. i will post when I drop in the new dist.