Carbon clogged C3 Intake Manifold

[Greg Metzler]

OK... my '68s carb and ignition system are running the way they were designed...

However, the intake manifold is completely gunked up with carbon. Any suggestions on how to remove it?

[Joe L.]

Re: Carbon clogged C3 Intake Manifold

Greg-----

If you're talking about the carb heat groove in the front of the carb flange being "gunked up with carbon", that's a GOOD thing. However, in that case I recommend that you drill the carbon out of the 2 holes on either end of the groove and install soft (cup) plugs or pipe plugs to eliminate this carb-destroyer for good.

If you're talking about carbonized oil on the bottom of the intake, you need to remove the manifold oil shield by prying out the 4 drive rivets that retain it to the manifold. Then, you can chip away all of the carbon with a hammer and chisel (carefully, of course). If you wish to get it completely clean, you can then take it down to the local machine shop for a hot tank (best, if they still have it) or high temperature oven cleaning.

To replace the shield, either use new drive rivets (GM #10229247) or drill and tap the holes for machine screws, installed with Lock-Tite. I do the latter.