Discussion
I have been having a lot of problems with stalling on my 535 hp AS engine when up to temp, more or less from day one.
I have a high overlap cam so I am not expecting a smooth idle, but whenever I stop at traffic lights or a roundabout it invariably stalls.
I took it to the factory a few weeks ago where they messed about with it for couple of hours, but it has not improved.
The idle screws are having no effect and it was impossible to increase idle speed.
I then read in the Holley book I have, the following which interested me:
"When a high-overlap cam is used it may be necessary to drill holes in the throttle plates to increase airflow at idle. This allows the throttle plates to remain properly positioned with relation to the transfer slot, improving idle characteristics and reducing plug fowling"
So that is what I have done. 3/32" hole in the primary plates.
This appears to have helped a bit, although idle speed when cold has increased a lot.
It still stumbles when pulling away but am imformed that this is due to the accelerator pump nozzle.
Any thoughts on this?
It's not much fun to drive at the moment!
Gary
I have a high overlap cam so I am not expecting a smooth idle, but whenever I stop at traffic lights or a roundabout it invariably stalls.
I took it to the factory a few weeks ago where they messed about with it for couple of hours, but it has not improved.
The idle screws are having no effect and it was impossible to increase idle speed.
I then read in the Holley book I have, the following which interested me:
"When a high-overlap cam is used it may be necessary to drill holes in the throttle plates to increase airflow at idle. This allows the throttle plates to remain properly positioned with relation to the transfer slot, improving idle characteristics and reducing plug fowling"
So that is what I have done. 3/32" hole in the primary plates.
This appears to have helped a bit, although idle speed when cold has increased a lot.
It still stumbles when pulling away but am imformed that this is due to the accelerator pump nozzle.
Any thoughts on this?
It's not much fun to drive at the moment!
Gary
hi gary nice to see you on sunday car looked great!!good tip on drilling butterflys,do you know what static timing you are running?could try tweeking it a small bit !also spray some wd40 around inlet manifold and carb to check that you have no air leaks any where engine note will rise if there is .simon
I had similar problems with my Standard Holley, I never managed to get it right even with the help of a Lamba sensor kit to tell me what was happening with the mixture. In the end I changed the Carb for a Modified version. I bought a Chuck Nyton 750 DP it ran perfect out of the box. That was my solution anway...
Simon,
nice to see you too last sunday.
Hope to see your canam on the next meeting!
I think I will see if I can get my carb professionally tuned before I start playing around with the timing. I would have thought it would be spot on when it was run up on the dyno, can't see it being altered in any way?
Clive,
As a matter of interest where did you get your replacement carb from?
Gary
nice to see you too last sunday.
Hope to see your canam on the next meeting!
I think I will see if I can get my carb professionally tuned before I start playing around with the timing. I would have thought it would be spot on when it was run up on the dyno, can't see it being altered in any way?
Clive,
As a matter of interest where did you get your replacement carb from?
Gary
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