So I went to adjust my newly rebuilt weber 40's and it was backfiring at anything close to idle. Then I saw some leaves and dust fly around right when it backfired.. So I look down and see a backfire, through a gap in the intake manifold gasket!

It appears that the gasket was made out of a phenolic sort of spacer, with a paper gasket on each side. Well there were several spots where the paper had completely blown out. It's amazing it ran at all!

So anyways, I am getting new gaskets tomorrow, and I ran the intakes on a belt sander to get them flat (they weren't even close).

The question is, did the vacuum leak cause the backfires I saw, or do I have a timing/valvetrain/ignition problem to deal with? (the engine never got a chance to warm up, just a couple minutes of running poorly)

I would say yes. The air leaks caused the backfiring. All the air needs to be metered by the carb or you'll get some strange things happening.

P

QUOTE (URY914 @ Oct 19 2005, 05:09 AM)

I would say yes. The air leaks caused the backfiring. All the air needs to be metered by the carb or you'll get some strange things happening. P

Phew! Good to know. Hopefully by then end of the day I'll finally have a running 914 again!

RTV will seal a lot of vacuum leaks..................and fill in "less than perfect" sealing surfaces.

QUOTE (SLITS @ Oct 19 2005, 07:31 AM)

RTV will seal a lot of vacuum leaks..................and fill in "less than perfect" sealing surfaces.

I thought a certain club member said that if you use RTV on a 914, the brakes will fail and you will die.


Andrew

Leaks on the intake side will let air in after the carburetor at low vacuum and lean the mixture, which will cause it to pop back out the intake.

with Paul!

QUOTE (phantom914 @ Oct 19 2005, 09:47 AM)

I thought a certain club member said that if you use RTV on a 914, the brakes will fail and you will die. Andrew