352 carb popping and spitting

[oddball]

Im having an ongoing problem with my 352 backfiring through the carb. When the engine is cold it starts fine. It wont idle at all though and after a minute or so it misses, and backfires real bad no matter what I do. I tried adjusting the carb, swapping the points distributor for one with pertronix, redid the timing 20,000 times, checked the timing chain, etc. I dont know what else to do, Im ready to look for another motor. Im pretty sure the timing is ok, as I cant get the distributor to fit in any other way so it will run. Ive searched quite a bit and Ive checked everything I could think of

[oddball]

I wanted to elaborate that when I install the distributor it SEEMS to point to number one on the cap, and I cant get it to fit onto the oil pump drive shaft in any other position. Also would a intake manifold leak cause this? I took it off before and used the right stuff gasket maker instead of regular gaskets.

[kaptnkaos]

Hey oddball

I don't know anything else that that will make a carb pop and backfire other than valve timing or something in the primary ignition system. (points, cap, rotor, burnt valves, timing chain, vacum advance, etc) and yes, a leaky intake will cause it as well.
Did you swap intakes?
Did you have problems with it before pulling the dizzy?
The dizzy has to fit in other postitions as well... it could just be one tooth off.
I'd pull the number one plug and make sure it is at TDC, by measuring it with a piece of wooden dowel.
Then I'd stab the dizzy, making sure that the rotor is pointing to the number plug wire.
At this point, it will either be pretty close or 180 out.
Did you happen to scribe a line up mark on the dizzy and intake before pulling the dizzy???
To get the timing closest to being spot on without it running, set the crank and dizzy at TDC, take a feeler gauge and stick it between the point contacts and advance the dizzy just until it releases the feeler gauge. That should put you at about 6 degrees before TDC.

Hope that helps...

KaptnKA S

[fordman]

i was goign to say last night that it sounded like a vacuum leak with the non idle issuse. but it also sounds like a timing problem. now that you mention the intake gasket thing. i want to say vacuum again. surely your not 180 out. or it woudlnt run at all i wouldnt think. ive never had one run at 180 out.

[oddball]

The truck ran great before but had a bad exhaust leak, I pulled the intake and heads to repair the leaks. It was ok for a bit but got progressivley worse, that was 8 months ago. Ive been trying to figure it out on and off ever since. I used that right stuff sealer because I went through three intake gaskets and it kept leaking water into the oil. There is no fluid leaking now but I might pull it again and start over. Is it true vacuum leaks at the manifold are hard to detect? There never was any whistiling noise.

[kaptnkaos]

Yes, Oddball... vacuum leaks can be difficult to trace down.. now that we have a little more info, it might be a little easier to figure out.

You can spray a little bit of starting fluid around the contact surfaces, if the engine rpms increase, then you have a vacuum leak.

The fact that you are getting water in your oil sounds like it might be a leaky head gasket. I had one go out on me on my '68.
No water leak, but I had one heck of an exhaust leak. It blew to the outside... and sounded like a tractor. I thought it was the header gasket, but it wasn't.
Are you trying to seal a stock steel or aluminum intake??
You might wanna use a cherry picker to set the intake in place, especially if it's a steel one. ALl it takes is one little slip to knock the gasket out of alignment.
I know this is gonna be expensive but I would pull the heads and have them checked out... they might be warped 'causing them not to seal properly.

KaptnKA S

[montana_hiboy]

Backfiring (popping) throught the carb is often indicative of a lean condition (assuming your timing is right) a vacuum leak will lean out your air/fuel mixture, i'd check the intake gasket for leaks as mentioned above, lower your idle speed when spraying for leaks so you can hear the slightest increase in rpms.

[cdeal28078]

Seeing as how you used gasket maker instead of an intake gasket I think that is your problem. Probably leaking causing a very lean condition which would cause the popping.
It could also cause water to get into the oil by leaking around the water ports.
clint

[oddball]

Thanks to everyone for there help, I went ahead and got a new intake gasket, Ill change it out this weekend