Thread: Problem with new ZZ4 350 Motor

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Keith,

I thought those threads I posted answered the questions . . . but here goes.

1. Yes, you can get the 50 degrees you talk about, and no, it is not good. That's why your engine is acting up.

2. The HEI that is shipped with the ZZ4 has a crappy vacuum canister on it. It's not broken, but Chevy made a poor choice by using that part. It puts in too much vacuum too fast - as you have found out.

Here are three courses of action:

1. Disconnect the vacuum advance and plug it. Set your timing at 36 deg. at 4000. Run it that way. If it pings, drop the timing a degree at at time. You may get less gas mileage than with a vacuum advance.

2. Get GM part #1973681 and replace the stock vacuum canister. This canister puts in 10 deg of vacuum instead of 20 and has a stiffer spring. Use ported vacuum. Set initial at 12 deg. See how it runs. If it pings, drop it a degree at a time.

The part is available from http://www.gmpartsdirect.com for $22.81, including shipping.

3. Take your distributor to a good shop, tell them your application, and have them recurve the distributor.

No matter which route you take, you need to play around with your timing, moving it several degrees both ways and noting any change in power or pinging.

Hope that helps.