Technical 350 timing walking

Hello all my new crate engine is giving me the blues yet again. I'm having a terrible time getting it to idle it will rev nicely but sounds like its choking on deceleration i had a brand new holley 570 street avenger on it but I figured the idle quality was the carbs fault so I put on my old holley 500 that worked great and had the same issue but the more alarming problem this engine is having is that the timing is walking several degrees back and forth on the balancer. I have a cheap summit hei on it right now but having eliminated the carb almost 100% as a factor I'm guessing the dizzy could be to blame for the walk??? Also the balancer is brand new to the engine along with everything else. The dizzy gear had some up and down play when I installed it but I ***umed this was normal play with an hei(this is my first one)engine will hardly start without a shot of starting fluid. I have 60psi on cold start with 30 in the engine timed to 12 btdc on the msd timing tape on 6.75 inch balancer I have the distributor almost pointing at the number 3 or 5 cylinder could being off a tooth make it walk or wouldn't it just be made up in the mechanical advance??? All testing was done with vacuum advance unhooked... can anyone help me solve this problem so I can finally drive it instead of rev it in the driveway lol thanks in advance!!

 

I think you just need to go forward with your hunch and see what happens.

 

I don't understand what you mean choking on deceleration. Lippy

 

Yeah I'm thinking of just ordering up a Petronix or delco hei and hope for the best I've just never seen this happen before.thanks!

 

I mean it almost has a stumble on deceleration and starts running rough as it comes back down the rpm range but seems to rev up in rpm okay

 

Do you have an old set up that you know works that you can try before spending more money?

 

Been worried about you, Chevy Guy.
Dare I ask, what kind of springs and weights are on the mech. advance. Probably seeing some of that.
You need to total time it. Also have to ask if you have a dial back timing light? Might get by with your timing tape.

 

No unfortunately this is the only distributor I have for a chevy engine im trying to find out what else can cause this besides the dizzy but I'm running low on possibilities here

 

Hey mark! Thanks for the concern haha I need all I can get! And its the standard advance weights that came on the summit hei but I've heard some issues with these units being cheaply made and having some potential issues out of the Chinese box and as for the timing light I have a regular light without a dial function.

 

Saw one like this, once. The centrifugal advance weights were flopping all around at idle. Someone had put a recurve kit in the distributor and used the lightest springs and the heaviest weights. The weights could also be sticking, so you don't know where the advance is at when you set the initial timing.

That would be the first thing I would check.

Next would be timing chain. With the timing light, set to your 12 degrees, rev the engine slowly to about 3000 - 3500 rpm. The timing should advance quite a bit. (like 1 1/2" past the timing tab). Then let the throttle snap back closed. The timing should not retard beyond the 12 degrees you set it at. If it does, you probably have a stretched chain and/or worn sprockets.

BTW, I think your initial timing would probably be better closer to 8 degrees.

 

That come to mind but the word "cheap" had me stay away from trying to monkey with that distributor. Should run fine out of the box with no issue's other than to fine tune where one want's they're timing to be within the unit.

 

I had a similiar problem that came down to...

the cheap-a$$ chinese chrome hotrod distributor clamp (installed by prior owner) wouldn't hold it's shape, and would... soften... allowing the distributor to move. A standard steel GM distributor clamp fixed it. I will say this for the chrome one... it made a very pleasing 'TING!' sound as it entered my garage trash can.

 

I'm kinda with gearheads, I'd back that timing down a bit and see how it acts. Possibly another way to check the timing chain and gears without tearing into it might be to remove the dist cap and put a socket on the crank and slowly rock the crank back and forth and note the slop before the rotor moves in relation to the crank. Jut an idea. If it is excessive it may warrant having a look inside the timing cover. Lippy

 

Gh , This is a new hecho in mehico crate engine, but anything is possible, I suppose.

 

Thanks for that ill check that for sure in the morning I hope the timing chain would be good on a crate engine but I know it's possible!! I'm not very savvy in the internals of distributors so I may do the checks you mentioned if all else fails try a better distributor...and ill check that hold down clamp I didn't think of that although it was tight last I checked and I'm using the clamp from a pontiac block so stock gm hold down 60s era.

 

Cool that's a great check thanks for that ,id really like to rule that out as being an issue ill be doing that for sure

 

Does anyone know what the proper dizzy gear end play should be?

 

I think I see the problem, your distributor is dizzy, a common problem when a distributor gets it's sea legs on a slow boat from China!
It needs time to acclimate to the dry land in Texas!
KK

 

Haha sounds right to me its too dry here for the poor thing! I had a small regret after buying it and saving 60 bucks but the whole install I thought this thing is kinda cheesy for my car....

 

^^^^THIS!

 

If the mechanical side(springs, weights, bushings, clamp) of the distributor is fine and the timing chain is not sloppy, I would also look at the HEI module, pickup coil, and ignition coil. Sometimes the S***mit parts are cheap Chinese bits. Find a shop that can properly test these. They will have to leave the module on the tester for a while so it actually heats up. Just popping it on the tester and verifying it works is not going to confirm the module is going bad due to heatsoak.
I've used the Accel Blueprint series in the past, but I don't think those are available anymore. Also verify that your Tach is not doing anything goofy. A faulty Tach can goof with the HEI as well.

 

Didn't know that about the tach ill look at it and make sure everything is good to go there...and yeah that's what i was worried about was inferior parts in there moving around out of spec. I've heard some pretty good stuff about Petronix us made coil and module and quality parts should be better then the s***mit unit! I've heard that delco hei are made in Taiwan

 

I'd start with Lippy's suggestion of checking the timing chain. That doesn't cost anything except five minutes if it is good and a new chain if it has slack but then you can mark that one off the list.
If I knew someone with a scope to hook it up to I think that is what I would do beyond that rather than piss in the wind and hope that I could get it right.

 

I usually get them as close as I can to .020”. Too much and the spark ****ters like you’re describing but too little and you’ll bind everything when that long aluminum housing heats up. Learned that one the hard way.
Stock cam? I only ask because if you have a cast cam and a bronze gear, the cam will eat the gear. If you have a steel gear on a roller cam (steel cam) the gear will eat the cam. Either situation causes a bunch of backlash right before it fails and thus spark ****ter just like you mentioned. GM also recommends a melonized gear if your crate engine has one of their factory hyd roller cams. Just a few things to check.

 

That's exactly where I'm going to start thanks again for all the great replies everyone. And fmstruck it has a flat tappet cam that comes on the 260hp 350 crate its the old 327 300hp cam.. After checking that timing chain and a few other things ill pull the distributor and take a look at the end play.

 

Hold on here. Let's back up.
Say that again.
3 and 5 are nowhere near #1.

 

That's how much I had to advance it to get even close to 10- 12 btdc

 

I had basically the same problem you are describing except on a 302 Ford with a cheap HEI . The timing was all over the place checked by my timing light.
Replaced it with a new distributor and it straightened right out. Seems that they can't get those cheap HEI's to have a decent curve.

 

Pull the stock distributor out of a running engine and try it.