I rebuilt my 350 a couple of months ago and after a few days I notices that the center portion of my intake manifold's paint was getting burned off, my mnaifold is a caligornia egr model and it has the thermostatic rod for the carb choke.. I BELIEVE THAT MY PRIMARY ROD AND JETS ARE TOO LEAN FOR MY CONFIGURATION. MY CAR IS ALL STOCK, BUT THE PISTONS ARE BORED 0.040". WOULD THE BORING OF THE PISTONS CAUSE THE LEAN CONDITION. i ALSO RUN ON A STOCK(REBUILT BY ME) ROCHESTER QUADRAjet any sugestions on rod/jet size? I have no idea what size I have in the carb right now. Thanks ou:
I had that problem. It was the paint....not high enough heat rating. Mine was good up to 500 degrees...so it said. But after less than a month, it burned up on the center section. That's where the heat passage is on the intake and it gets quite hot there. Next time I paint my motor, I'm going with Dupli-Color High Temperature Red, #1608. It says that it's good up to 1200 degrees.
Next time have the block powdercoated for a life long finish and shine. Creamic coat it and the block will never get above 60f to the touch, even when "hot". Matt
I'd rather pay $10 for a couple cans of paint. I'm not rally into spending G's on engine paint and finish.
To check your air/fuel mixture, start by looking at your plugs. Go from there. The only place you will lose a little paint in proper tune in most cases, is around the exhaust port area of the head. It will discolor a little and sometimes burn off. The intake manifold shouldn't be that hot. Did you block off your heatrisers? Even if they're not block off your intake manifold shouldn't get that hot. Check your plugs. Maybe some one else can shed some light on this too. John
I have a '71 GS 350 and it too burns the paint in this area. It is totally stock and well maintained, and I have no reason to believe the mixture is excessively lean. I even noticed a couple of days ago that even when the engine was not fully warmed up, this portion of the manifold was much hotter than the rest. I could hold my hand on all areas but this one, which was quite hot. This area is directly connected to the exhaust ports and has exhaust gas passing through it. This is normal and should be no cause for concern.
Hi Chief, If you give us the numbers off the carb, I might be able to tell you how it is jetted now. Then you will have a baseline. With a stock engine, you shouldn't need to rejet. If you added headers and a manifold and cam, you would. With Q-jets, the rule is for every 3 jet sizes you go up, you go up 1 size in primary rod. If you have say 68 jets and 44B primary rod, you could go up to 71 jets with 45B rods. This preserves your cruise mixture, but also gives more fuel when you are havin fun:Brow:
I agree 100%. "Reading" intake-manifold-paint-burn is far less accurate than reading the spark plugs!
