82TA

Would the improper intake gaskets make the carb percolate?? If so, which gaskets should I use? 305H lg4 stock rebuild.

Apeiron

The regular thin carb gaskets don't offer much in the way of insulation. Look for a quarter-inch thick gasket with metal bushings in the mounting holes. I don't have part numbers handy, but Mr. Gasket has them, as do other manufacturers.

82TA

I was refering to the heat cross over passages, i think mine are open, was wondering if different gaskets would help.

Bunker82

Actually the proper gaskets might since it will allow the exhaust to heat the intake. Changing the gaskets to ones without holes (non stock) may help, but I think you are not attacking the problem. I believe (don't quote me on this) that stock engines normally don't have percolation issues if everything is working properly. If this is a bone stock engine, and you have the standard Q-Jet gasket that is like 1/8" - 1/4" thick, and timing, etc. is all ok you shouldn't have a problem. I think I have heard someone mention on the boards that a dealer option existed that they would install a small fan near the carb to keep it cooler. But I really think if this is a stock engine, you shouldn't have issues and therefore you'd want to check other causes first (if you haven't already done so). To me the pros and cons of blocking that passage still keep me from deciding one way or another as to which is best. I hear that for anything but an all out race engine, leaving that crossover is a good thing. Gets the engine up to temp faster, atomizes the fuel better giving better economy and longer ring life, etc. Anyway, food for thought.

PS If you have an aluminum intake (my LG4 did) even with those passages blocked it is gonna get hot. The intake will absorb heat from the coolant crossing over in front, and the thirdgen underhood oven.

82TA

Thankyou for the thoughtful reply. Yes the rebuild was a stock. .030 over, slight upgrade with comp cams cam,but very close to stock. Timing is at 8 btdc, fresh ignition, low resistance wires, accel coil, etc.When cold, it fires right up and goes on fast idle, comes off when warm like it should, everything is fine accept starting it after its been driven and shut off for a bit.Yes it does have alum. intake,even thought of using a high grade 7 ply plywood 1/2" spacer between the carb and manifold to stop the heat transfer. I know alot of bracket racers that use that to keep the fuel charge cooler. Temp guage doesnt get over 180 or so this time of the year. I dont think that there is excessive heat during operation, just seems to head soak when shut off. My car is '82, so no electric themo fans to kick in to cool it down.Could the float level bet set too high?

Dens71TA

iTrader: (5)

The carb'ed 3rd-gens have always had a problem with heat soak. I think it has a lot to do with the itty bitty engine compartment.

The 5.0L HO cars especially had problems. There were TSBs that added a special carb spacer with a big metal heat shield to shield the carb from the intake, a little fan to blow air on the carb, and a low pressure fuel pump in the tank. I don't know if any of these parts are still available from GM but you may luck out and find something in the junkyard.

How hard to start is your car after its been warmed up and shut off for a while? My '84 LG4 will boil out the fuel during hot summer days but during the winter months it will usually start after cranking for 3-5 seconds when the engine is warm.