Dizzy Advice needed.......
Thread Starter
Advanced
Joined: Dec 2011
Posts: 62
Likes: 6
From: Columbus Georgia
Dizzy Advice needed.......
First of all, This is the greatest Corvette Forum on the net. Second of all, Thanks to everyone for sharing their knowledge and experiences with everyone here.
Here is my problem-
355 SBC, Moderate cam : unknown durations, Accel HEI.......
I'm experiencing pretty bad break up at WOT sometimes. As in sometimes it does it, sometimes not. I took the vacuum hose off the vacuum advance and it appeared to stop. Engine runs great if I drive it easy. Will it hurt anything if I leave the vacuum advance disconnected? Does it sound like I need a new dizzy? Is this one "rebuildable"?
What do you guys recommend? I'm lost on this one.......
Here is my problem-
355 SBC, Moderate cam : unknown durations, Accel HEI.......
I'm experiencing pretty bad break up at WOT sometimes. As in sometimes it does it, sometimes not. I took the vacuum hose off the vacuum advance and it appeared to stop. Engine runs great if I drive it easy. Will it hurt anything if I leave the vacuum advance disconnected? Does it sound like I need a new dizzy? Is this one "rebuildable"?
What do you guys recommend? I'm lost on this one.......
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
What is your timing set at? Base with no vac advance at idle.
Has it done this since you owned it or is this new? May just be getting too much advance. You could try tuning it out by lowering the initial timing or changing to a vacuum can that advances less.
Has it done this since you owned it or is this new? May just be getting too much advance. You could try tuning it out by lowering the initial timing or changing to a vacuum can that advances less.
Thread Starter
Advanced
Joined: Dec 2011
Posts: 62
Likes: 6
From: Columbus Georgia
It has done it since I bought the car back in September of last year. She had horrendous vacuum leaks from everywhere imaginable, but I have since tracked them all down and fixed them. I can't tell about the timing, the mark on the harmonic balancer can't be seen anywhere near the timing tab with a timing light. I just had to adjust the timing by how the engine sounded. I would advance the timing until it ran like crap, the retard it until it ran bad, then found a happy medium between the two. I think the timing tab is supposed to be on the top of the timing chain cover, but there isn't one there it is on the drivers side.
Drifting
Joined: Jul 2002
Posts: 1,944
Likes: 20
From: The only Corvettes in Highett Victoria
Set the timing properly.
Twisted,
The VERY first thing to do is set the timing accurately. Until you do, you will be chasing your tail. There is a permanent timing thread above, please take your time to look at it thoroughly and learn from it.
It will tell you these basics: set the total or all-in centrifugal timing at about 36 degrees, VACUUM DISCONNECTED. To do this, you must know where TDC is. Either buy a new balancer, preferably one with advance marks up to at least 36* or use the positive stop method to find the right place on your old balancer.
Secondly, make sure the dissy is in good working order. Maybe that should have been the first thing.
When you know that your dissy is working properly and the timing is set correctly, connect the vacuum lead from BELOW the throttle blades, i.e. manifold vacuum.
When you know that all of this has been done correctly, the car should run well. If not, then start looking at other areas.
Regards from Down Under.
aussiejohn
The VERY first thing to do is set the timing accurately. Until you do, you will be chasing your tail. There is a permanent timing thread above, please take your time to look at it thoroughly and learn from it.
It will tell you these basics: set the total or all-in centrifugal timing at about 36 degrees, VACUUM DISCONNECTED. To do this, you must know where TDC is. Either buy a new balancer, preferably one with advance marks up to at least 36* or use the positive stop method to find the right place on your old balancer.
Secondly, make sure the dissy is in good working order. Maybe that should have been the first thing.
When you know that your dissy is working properly and the timing is set correctly, connect the vacuum lead from BELOW the throttle blades, i.e. manifold vacuum.
When you know that all of this has been done correctly, the car should run well. If not, then start looking at other areas.
Regards from Down Under.
aussiejohn
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
No way to know if you need a new distributor. You need to set your timing accurately, adjust your timing curve for your setup and have correct vacumn can for your setup. If your setting timing by ear it is always to far advanced. That will be where it seems the best. It will also cause detonation which will destroy your engine quick. Get this fixed before a minor problem turns into thousands of dollars. Might be as easy as buying a $4 timing tab and setting what you have correctly.
Thread Starter
Advanced
Joined: Dec 2011
Posts: 62
Likes: 6
From: Columbus Georgia
one thing that I forgot to mention about the distributor, 
when the car sits for about a week or so, she won't crank........I have to pop the hood and give the distubutor cap a couple of soft whacks 
then she will fire right up............I'm going to Summit tomorrow to get some "supplies" that were mentioned above, and I'll read the thread again about setting the timing a couple of more times.
when the car sits for about a week or so, she won't crank........I have to pop the hood and give the distubutor cap a couple of soft whacks then she will fire right up............I'm going to Summit tomorrow to get some "supplies" that were mentioned above, and I'll read the thread again about setting the timing a couple of more times.
