I have had this happen 2 times now.

The car has a newly rebuilt 350TPI with ZZ4 Cam and FT Pistons in it. New ACDelco Plugs, MSD Cap, Rotor, Coil and Super Conductor Plug Wires. The car has the original balancer off from my 305 as the guy who built my motor said that shouldnt be a problem as well as the original Distributor with a different gear to mesh properly with the ZZ4 Cam.

The car is a 350 swap from a 305, has a 350 chip in it. Anyway, When we first got the car together everything ran great. Timing was set at 8deg. I drove the car about 200 or so miles on 3 separate occasions, didnt have any problems the first 150 miles. On the way home the last trip the car just started getting super doggy and running rough. I actually ended up having to park it about 12 miles from home.

When I got it home, slapped a timing light on and it was way off. It was off going towards the ground on the drivers side so far that you couldnt see the line on the balancer. So we start hunting around for problems. We found that one of the vacuum lines had a crack and that was causing a big part of the problems too. So we fixed that, got the timing set back at 8deg and all was well.

I drive the car down to the end of the road and back a few times and back and i notice on the last pass that it was losing power. So, I park it, slap the timing light back on, and again, its way off. Went from about 7deg advanced to about 10deg retarded in the matter of 2 miles down the road and back.

I am at a loss as to what the problem is... The dist does not appear to have moved, is it possible i have chewed the teeth up on the dist gear? Bad Rotor? Distributor? Ignition Module? Something Else?

My A/C box is a little melted from too much heat too, it might sound stupid but is it possible that there is some sort of vacuum leak through that box? We sprayed carb cleaner all over looking for vacuum leaks and didnt seem to find any.

It was throwing a code 34, but has since stopped, atm its not throwing any codes.

Im at a loss for whats going on, anyone have any ideas for me? I havnt had a chance to pull the dist and check that. I am assuming its an original, we had to clean up the magnets and stuff when we were putting stuff back together because it was corroded.

I would really appreciate your guys feedback. This is my first time doing anything like this, so Im kinda lost as to where to start.

 

The stock '88 distributor gear (assuming you're talking about a stock '88 engine) would have been fine on the ZZ4 cam. They're the same thing. If you used a brass distributor gear, pull that distributor right now and put the stock gear back on.

There was a thread a while back about this sort of problem. As I recall, the problem turned out to be the trigger wheel slipping on the distributor shaft, or something along that line.

 

5.7 your still the man

Now what exactly is the trigger wheel?

And as far as the gear is concerned, the guy who built the motor for me told me to use the gear he gave me. They looked the same, it wasnt brass colored. When my buddy and I were putting it on we both were wondering why we needed to change it, i guess that would explain it.

I have changed the oil since and I did not notice any brass shavings so I dont think the gear was getting chewed up, but i guess its always a possibility.

 

The factory says to use a "melonized" distributor gear with a factory roller cam. It's just got some kind of surface treatment, from what I understand. They look the same.

The trigger wheel is the part inside the distributor attached to the shaft that provides the pulse that is picked up and sets off the spark sequence. I'm not very familiar with the small cap HEI, so I'm already over my head.

 

Is that something that is repairable or new Distributor Time? And how do I know if its doing it?

 

If I've got the picture right in my head, it's part of the shaft. Easiest would be to put in a new distributor.

 

Thanks for all the help. Any reccomendation on replacement Distributor's?

 

I had a similar problem after a cam swap a few years back. The small cap dist ran fine before the swap but timing was crazy wild afterwards. Figured it must have been near failure before pulling it and the swap killed it. It, too, had corrosion around the reluctor and the insulating material was chiping off. Swapped it out with a rebuilt replacement from AZ for about $99. The rebuilt one has a warranty and if you're not satisfied, take it back. When you go to swap them, you'll have a chance to look at your dist gear and check that, too.

A decent aftermarket replacement runs around $250. I'd stay away from the $150/proform/summit brands. Read bad things about them.

 

If you have a couple bucks to drop you could pick up a new 'ready to run' dizzy from MSD or something.

Or just pick up a dizzy from the junkyard and clean it up...

 

You guys are awesome, thanks for all the help. I will be home for christmas, so that wednesday-friday I will be working on the car. I will let you know how it turns out.

 

Please give update on the problem...Thanks, Tom

 

Is there any major benefit to going with a MSD dist. versus a regular rebuilt one from Autozone?

Should I put a new Ignition Module in at the same time?

 

The rebuilt one from AZ will come with a new ignition control module (although not an AC Delco part). The major benefit from getting the one from AZ (or the equivalent) is you can take it back for a refund if you're not satisfied (or it doesn't fix the problem). The MSD distributor will be prettier and give you that proud "I spent $300 on distributor" feeling but that's about all.

Always save your old ignition control module to keep as a spare. It seems to be the one part that always fails when you're farthest from home.

 

Awesome, Ill just wait and pick one up then when I get back in town.

Car is at my parents house, so thats why I wont get to work on it until next week.

Any issues with running the MSD coil with the stock ignition module?

 

Unless you plan on doing anything too fancy with the motor, no you dont really need anything other than an OEM HEI dizzy. Its more than enough for a stock-mild motor, but they dont do much for the bling factor!

 

i picked up the reman from AZ. Its pretty nice, comes with the Gear as well (wasnt expecting that) I am assuming its the right one and I shouldnt need to swap it?

Anyway, I'll put it in when I get back to my parents at christmas and see if it does the trick or not.

 

Is there supposed to be up and down play in the dist. shaft?

I was talking to a friend of my dads that says that up and down play in the dist. can cause the worm gear to creep up and shift the timing somewhat.

Any truth to this?

going outside to pull the dist. today.

 

Pulled the dist. today... Turns out the pin that holds the gear on the end had slid out so it was only holding on one side and allowing the gear to slide around a whole lot.... consequently chewing the teeth up on the gear.

I have the replacement distributor ready to go in now as the magnets on top of the old one are nasty rusty, so its time to go.

family is over for christmas today, so my buddy is coming over tomorrow to finish putting in the new dist. and getting it timed.

I gotta go down to the store and get a magnetic drain plug and oil and filter to change tomorrow too.