Ok so the saga continues..
Heres the history..
ZZ4 Crate engine.. about 7k miles on it, Barry Grant ZZ4 crate demon carb. Stock ignition (hei) etc.
So I had some initial issues setting the timing but got it set to 12 degrees btdc at around 800rpm with the vacuum advanced disconnected and plugged.
Ive got the carb butterflies closed as far as they can, ie idle screw all the way and the secondary butterfly's stop all the way out.
So after setting the initial timing and plugging the vacuum advance back in to the manifold vacuum port the advance jumps up (as its supposed to) but as a result of that the RPM also increased. So the RPM jumps to around 1200-1300 and I cant get it down any further. I can get the RPMs down by screwing in the idle mixture screws but I have a feeling thats not the right way to do it.
As a temporary fix Ive connected the distributor vacuum advance to the ported vacuum port. This removes the advance at idle and as a result a slower speed. Im experiencing some 'tip in' pinging on light part throttle acceleration and have a feeling its a result of the ported vacuum advance. Im running 92 octane guess fyi.
So I know that roughly 80% of the people are saying the full manifold vacuum is the way to go but for what ever reason I just cant get it to work..
So my questions are:
1. ***!!!! why cant I get the RPM down? Ive never not been able to lower the rpm of a carb
2. Is 12 degrees btdc optimal? I can drop it down to help lower the RPM maybe put it at 8? what would that do to the engine and its performance
3. The base advance is set as 12 with the vacuum advance disconnected, with it connected it jumps up to about 25! Is that right? It seems really high to me, like the vacuum can is putting too much advance in.
Thanks guys for looking and helping!
Joe
Heres the history..
ZZ4 Crate engine.. about 7k miles on it, Barry Grant ZZ4 crate demon carb. Stock ignition (hei) etc.
So I had some initial issues setting the timing but got it set to 12 degrees btdc at around 800rpm with the vacuum advanced disconnected and plugged.
Ive got the carb butterflies closed as far as they can, ie idle screw all the way and the secondary butterfly's stop all the way out.
So after setting the initial timing and plugging the vacuum advance back in to the manifold vacuum port the advance jumps up (as its supposed to) but as a result of that the RPM also increased. So the RPM jumps to around 1200-1300 and I cant get it down any further. I can get the RPMs down by screwing in the idle mixture screws but I have a feeling thats not the right way to do it.
As a temporary fix Ive connected the distributor vacuum advance to the ported vacuum port. This removes the advance at idle and as a result a slower speed. Im experiencing some 'tip in' pinging on light part throttle acceleration and have a feeling its a result of the ported vacuum advance. Im running 92 octane guess fyi.
So I know that roughly 80% of the people are saying the full manifold vacuum is the way to go but for what ever reason I just cant get it to work..
So my questions are:
1. ***!!!! why cant I get the RPM down? Ive never not been able to lower the rpm of a carb
2. Is 12 degrees btdc optimal? I can drop it down to help lower the RPM maybe put it at 8? what would that do to the engine and its performance
3. The base advance is set as 12 with the vacuum advance disconnected, with it connected it jumps up to about 25! Is that right? It seems really high to me, like the vacuum can is putting too much advance in.
Thanks guys for looking and helping!
Joe