Holley expert needed?
I have a 4780-2 800 cfm carb; It always ran well and I have an AFR and have had it tuned for cruise of about 14.8-15.1:1 for at least the past year. I drove the car about a 6 six weeks ago and it ran very strong as usual and hadn't driven it until last last weekend: and started acting a little funny and lean at idle intermitently 15:1( usually 13.5:1) etc seemed off.
8 months ago started to notice a lean spike on the AFR 17:1 intermitently and thought it was the gauge and ended up replacing the o2 sensor. it still did it infrequently but couldn't really feel a surge. Last weekend I could feel it when the gauge was whacking out and noticed it was harder than normal to get to idle when warming up and was going lean.
I pulled the carb today and found some gasket debris in one of the IFRs and ended up replacing base gaskets and throttle body gasket. I noticed the inner TB screws between the throttle blades were deleted but I believe they have always been that way in effort to avoid falling into the intake. If I had lost them both in the intake I think it would been catastrophic ...
Anyway, put it back together and it wouldn't idle was going totally lean, checked and double checked vac lines etc etc.
Ended up throwing another metering block on thinking something was blocking something and it started fine, ran smooth and idled for about 30 secs and then same thing. I was thinking it maybe was an intake man gasket going bad but the Metering block switch changed my mind. It acts as if it has a huge vac leak or something (WON't IDLE)..actually just dies and quick, I was thinking needle and seat but usually it will dump fuel and bowls will overflow; but it is not rich but lean?
checked the site plugs both looked fine, I am not sure what to do but it is acting majorly weird and I was planning to race this weekend and now I am not sure WTH is wrong with it.
fuel pressure seems fine, only thing I did different was got gas before I put it away; it has basically a 7/8 of tank.
the carb has been modded years ago, no choke horn, smooth bored, typical tricks and has always ran well, it does seem like a progressive problem since it ran a little funny and surged with the gauge spike 17+:1 AFR LEAN! and has been getting harder to get to idle when cold, when it used to idle cold after a short time.
I am baffled, and could use some help badly, thanks SS.
406, TKO 600 and 12 bolt posi.
Last edited by railing68; Apr 28th, 11 at 11:03 PM.