Need some assistance with ZZ4 crate motor

[Jetdriver]

Have a ZZ4 crate motor in the 56 and have had nothing but issues with it since we got it fired up. Currently it runs well but doesnt seem to produce the power I feel it should have. It also diesels on shutdown at times. We had a hotrod builder go over it and he ended up replacing the demon carb with a holley and he replaced the distributer with a new msd model. Still runs weird. He stated to me that he had a hard time timing the motor and could only get a few degrees of adjustment out of it before it ran like total shit. At this point I need someone that knows motors and hotrods to take a look at this.

Thanks for the help,
Shawn

 

[obnoxious001]

I guess it might be worth having someone double check what's previously been done. How much timing are you running? Anyone check or adjust the valves? What about putting a degree wheel on the balancer and check cam timing? By "crate engine" I assume it was factory assembled? If the ignition and carb have been both checked and replaced,, makes me wonder a bit if the cam is in wrong?

 

[Jetdriver]

motor is a GM Performance crate motor bought direct from the GM dealership in Palmdale many years ago. I have wondered if the cam wasnt a tooth off or something. Is there anyone here that can look at it?

 

[rivermobster]

Look'n at it is one thing. Getting it fixed is another.

This guy specializes in GM crate motors. Ask for Bruce, tell him Joe/rivermobster sent you.

http://www.cbfunforyou.com/

 

[Gelcoater]

just a thought, [and im no engine guru] check to see that the coils negative terminal is connected to the distributor,and pos. conn.to ignition source. iv read that if its connected backwards of this it will run,but not deliver full spark energy. good luck with this and however you get it fixed,report back, i for one would like to know what it was

 

[Dave Wettlaufer]

Ok, the problem is that that engine is all alphanumerical! Awwright, I could not resist...LOL

So this engine was new and you have had problems from the beginning?
If so, I would do a static valve adjustment first off. By static adjustment I mean with the engine not running. Remove one valve cover at a time and turn the engine over manually. When the intake just opens, adjust the exhaust. When the exhaust closes, adjust the intake. This works on every 4 stroke engine. You want a quarter turn tight on both.

I have no idea why he went nuts with ignition and carb and I'm thinkin he's wondering the same thing!

Did you replace the distributor? Is the timing chain ok? What do you have for timing? Initial at idle? 2500 rpm? 3500 rpm? Is the spark steady?
This is what you need to know.

 

[Jetdriver]

Ok, the problem is that that engine is all alphanumerical! Awwright, I could not resist...LOL

So this engine was new and you have had problems from the beginning?
If so, I would do a static valve adjustment first off. By static adjustment I mean with the engine not running. Remove one valve cover at a time and turn the engine over manually. When the intake just opens, adjust the exhaust. When the exhaust closes, adjust the intake. This works on every 4 stroke engine. You want a quarter turn tight on both.

I have no idea why he went nuts with ignition and carb and I'm thinkin he's wondering the same thing!

Did you replace the distributor? Is the timing chain ok? What do you have for timing? Initial at idle? 2500 rpm? 3500 rpm? Is the spark steady?
This is what you need to know.

I wish I could answer all your questions but I can't. The truck was built by two different builders. The first guy stole parts and money and screwed my mom over big time, this is when i got involved. The truck went to the second builder and was taken to 90% and at that point I brought it home and finished it up. Again, this is a truck built for my mom I have just been lending a hand. I wish I knew what all happened to the motor. I do know that it was new direct from GM. I was there when it was delivered and unpacked.

 

[DaveH]

just a thought, [and im no engine guru] check to see that the coils negative terminal is connected to the distributor,and pos. conn.to ignition source. iv read that if its connected backwards of this it will run,but not deliver full spark energy. good luck with this and however you get it fixed,report back, i for one would like to know what it was

what you may be refering to and i have witnessed before is getting the wirring backwards on a MSD Distributor. this will casue unstable/erratic timing and the timing at RPM to be very over advanced.

the dieseling is from overly rich mixtures "wetting" the intake ports, and then being pulled into the cylinder after shutdown and lighting off.

get the car to a dyno for a real tune.

 

[Jetdriver]

what you may be refering to and i have witnessed before is getting the wirring backwards on a MSD Distributor. this will casue unstable/erratic timing and the timing at RPM to be very over advanced.

the dieseling is from overly rich mixtures "wetting" the intake ports, and then being pulled into the cylinder after shutdown and lighting off.

get the car to a dyno for a real tune.

Thats what Im lookin to do. Hope to find a chassis dyno soon.

 

[obnoxious001]

what you may be refering to and i have witnessed before is getting the wirring backwards on a MSD Distributor. this will casue unstable/erratic timing and the timing at RPM to be very over advanced.

the dieseling is from overly rich mixtures "wetting" the intake ports, and then being pulled into the cylinder after shutdown and lighting off.

get the car to a dyno for a real tune.

I was thinking it did the same thing with two entirely different ignition systems(1MSD, and 1 not?), by what I had read.

Something funky,, wish I had time and space to look at it for him.

 

[obnoxious001]

Thats what Im lookin to do. Hope to find a chassis dyno soon.

You might try Performance Associates in San Dimas, owned by Randy Ritchey. http://www.pahorsepower.com/

My dad knew his dad. He has been at it a long time, is highly respected and should be able to sort it out for you.

 

[Jetdriver]

Talked to Bruce yesterday and met with him today at CBM motorsports. The truck will be trailered down to him in a week and we will start the process of figuring out what the hell is wrong with this beast.

Thanks for the info on Bruce Joe!

 

[Jetdriver]

Spent the day on the dyno at CBM. The guys reset the timing to 8 degrees advanced for a base. had to completely readjust the carb. Finally got it to run and idle with out preignition after shutdown. 2 runs on the dyno and then changed the jets on the carb up 2 sizes. Another run and we were on our way back home. The dyno they use is geared for tuning more than just getting HP numbers. I guess they had it set conservative, saw 202hp at the rear wheel on our last pull. Truck runs exactly as we thought it should now.

Thanks to the guys at CBM

 

[Gelcoater]

Spent the day on the dyno at CBM. The guys reset the timing to 8 degrees advanced for a base. had to completely readjust the carb. Finally got it to run and idle with out preignition after shutdown. 2 runs on the dyno and then changed the jets on the carb up 2 sizes. Another run and we were on our way back home. The dyno they use is geared for tuning more than just getting HP numbers. I guess they had it set conservative, saw 202hp at the rear wheel on our last pull. Truck runs exactly as we thought it should now.

Thanks to the guys at CBM

cool you got it running:thumbsup

 

[rivermobster]

Talked to Bruce yesterday and met with him today at CBM motorsports. The truck will be trailered down to him in a week and we will start the process of figuring out what the hell is wrong with this beast.

Thanks for the info on Bruce Joe!

Bruce is a great guy. Glad this worked out for you!

:thumbsup

 

[rivermobster]

fyi...

he builds some pretty sweet boat motors too!

 

[racerden]

Have a ZZ4 crate motor in the 56 and have had nothing but issues with it since we got it fired up. Currently it runs well but doesnt seem to produce the power I feel it should have. It also diesels on shutdown at times. We had a hotrod builder go over it and he ended up replacing the demon carb with a holley and he replaced the distributer with a new msd model. Still runs weird. He stated to me that he had a hard time timing the motor and could only get a few degrees of adjustment out of it before it ran like total shit. At this point I need someone that knows motors and hotrods to take a look at this.

Thanks for the help,
Shawn

I have lots of experience w/the ZZ4. 1st and foremost, don't over carb it; a nice 650 will do fine. Many go out and hang a 750 or bigger and expect a fire breathing small block. The hydraulic cam and cylinder heads are not designed for large CFM's if the engine remains in stock trim. Timing is a bit tricky due to regional blends; try a total of 34-35 degrees if you run pump gas and see if any pinging is produced.
Lastly if it diesels and the timing is relatively close to what it should be, it's a combo of a too rich idle mixture and too high of a idle speed. With the proper carb, the ZZ4 will easily idle down to 550-600 RPM in gear.
Hope it helps,
Denny
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