What vacuum can for ZZ4
Thread Starter
Intermediate
Joined: May 2005
Posts: 43
Likes: 0
From: KS
What vacuum can for ZZ4
I have a stock GM Performance ZZ4 with the MSD tach drive distributor and 6AL box. I can't get the vacuum can that came with the MSD distributor to work with the ZZ4. I have the 21 degree stop bushing installed with 15 degree initial timing. The 2 light blue springs are installed to get the total in by 3,000 RPM. If the vacuum can is hooked up the motor will ping under load, if the can is unhooked there is no problem anywhere. I know that the stock MSD vacuum can must be wrong for the ZZ4, but I have know idea what can to use. I am hoping that someone on the forum has gone through this and can tell me what vacuum can is a good match for the ZZ4 with the MSD disributor.
Racer
Joined: Apr 2006
Posts: 477
Likes: 43
From: Millbrae California
i have and use on most motors i tune a vacc can that i limit the travel to .120" to give 10 degrees of vac advance and this solves the vac advance ping problem for me. no one i know of sells a 10 degree vac advance off the shelf. you could try a adjustable unit but i don't trust that the adjustment will not move with time.
I have "talked" to Lars about this but he does not know of a 10 degree vac can and he says he has not seen a engine that will ping with 16 degrees of advance from the vacuum advance when you have a total of 36 degrees (initial and mechanical) plus vacuum advance.
I have "talked" to Lars about this but he does not know of a 10 degree vac can and he says he has not seen a engine that will ping with 16 degrees of advance from the vacuum advance when you have a total of 36 degrees (initial and mechanical) plus vacuum advance.
Team Owner
Joined: Jun 2001
Posts: 23,359
Likes: 1,058
From: Virginia USA
Are you using ported or manifold vacuum as a source. I am using ported because when you stomp on it or are sitting at idle it takes the vacuum advance out of the equation. I have the same setup as you but I can't remember what springs and stop bushing I installed. I have 10 initial, 36 degrees coming all in by 2800 rpm. I have no ping unless the gas I get is Shi$&y which is hardly ever.
This may help too:
https://www.corvetteforum.com/techti...=115&TopicID=3
This may help too:
https://www.corvetteforum.com/techti...=115&TopicID=3
