I have a "popping" in the passenger side sidepipe under partial throttle (goes away under hard acceleration). Now I am running a multi carb set up and I know my vacuum flow is the same through all 4 venturi's.
I am thnking maybe a vacuum leak or maybe dirt in one of the carbs...anybody have ideas?


Nick

 

"popping" sounds like raw gas igniting in your hot pipe. Too rich? What carburetor(s) are you running?

 

Leaking exhaust gasket sucking in air.

 

I am running 4 Del'lortos (4 x 2 barrels)
The funny thing is that it was doing this when I first finished the 396 build and was using Pro Topline heads, I swapped them out for the AFR's last Spring and its doing the same thing. I changed the exhaust gaskets for the soft aluminum ones and they seal perfect. I am beginning to think its on the intake somewhere, maybe as the intake is in 5 parts (base and then 4 "runners") that maybe one of the runners on the passenger side isnt flat...might try and mist some water around there and see if it gets sucked in.

 

Popping in the pipes is usually lean out.

I'd look for a vacuum leak first.

 

How did your set-up your vac adv?

cardo0

 

 

well..i posted this earlier on

I posted yesterday that I was getting a "lean" pop in the passenger side sidepipe on my car. I am running 4 x 2 barrels (Del'lorto's) and disassembled the 2 passenger side carbs last night looking for dirt/broken o-rings etc. Didnt find anything on the carb, but I did find that someone had drilled a 3/8" hole through the wall of the intake runners (the intake is in 5 pieces, a base and then 4 "Y" runners that bolt to the base. Basically giving one barrel, one runner per intake valve).

Anyway my theory is that as I can't see any visible leaks, that because of this hole I am pulling air not only through the carb venturi, but maybe through the next cylinder aswell, say on an intake/exhaust valve overlap. So my question is, on a "intake" cycle for cylinders 2, 4, 6 and 8 are the intake/exhaust valves of the next cylinder open?

Having said this, the holes are being closed as we speak.

a little more info....... I have a Comp Cams solid roller, 248 duration intake, 254 exhaust (at .050") so I dont know if that is enough over lap to have the intake and exhaust open when the adjascent cylinder is on an intake cycle. (by my calculations when #2 is on intake, #4 is on exhaust (possibility of overlap???) could that be creating my lean condition????

Nick

 

Hi Nick are you running a crossram ?

Geo

 

No, running a vintage Mckay downdraft intake. Will be replaced over the winter with a wilson sheet metal one i am working on.

Nick

 

Have you balanced them using a manometer ? The dcoe has a port that allows vac checks in each IR . I have no knowledge of the model you are using .


GEO