427/425 flooding

[Walter R.]

Engine starts up great when cold. After running and shutting down engine is hard to start and appears to be flodding. Engine running very cool with ambiant tempertures in 70's but have a suspicion that the gas is boiling in carb causing hard start. I don't see an insulator listed for this enginein the AIM manual. Any suggestions?

[Joe R.]

Re: 427/425 flooding

Walter,

Is this a bone stock L72 engine? I seem to remember that you had a later block in the car at one point. Then you were looking for a period correct block, but I don't remember if you bought one or not.

Joe

[Clem Z.]

Re: 427/425 flooding

Engine starts up great when cold. After running and shutting down engine is hard to start and appears to be flodding. Engine running very cool with ambiant tempertures in 70's but have a suspicion that the gas is boiling in carb causing hard start. I don't see an insulator listed for this enginein the AIM manual. Any suggestions?

block the exhaust heat riser crossover in the intake manifold

[Walter R.]

Re: 427/425 flooding

Same 1972 block and I am still looking for correct replacement

[Joe R.]

Re: 427/425 flooding

block the exhaust heat riser crossover in the intake manifold

Clem,

I plan to do that, too. To expand on your suggestion, wire the heat riser open and only block the driver's side. That way a little heat gets to the carb when starting cold. But since there is no air flow, less heat is transferred to the carb. Which makes more horsepower and helps keep the carb cooler for hot start issues.

Joe

[Clem Z.]

Re: 427/425 flooding

Clem,

I plan to do that, too. To expand on your suggestion, wire the heat riser open and only block the driver's side. That way a little heat gets to the carb when starting cold. But since there is no air flow, less heat is transferred to the carb. Which makes more horsepower and helps keep the carb cooler for hot start issues.

Joe

chevy blocked both sides on the L-88 with a special intake gasket using stainless steel inserts. i blocked lots of them by just draining down the rad and slipping in .005 thick stainless steel shim stock after loosening the manifold bolts

[John H.]

Re: 427/425 flooding

Remember that your choke is operated by a remote thermostatic coil mounted on the intake manifold; if you block the heat riser passages on both sides, it'll take a LONG time for the choke to open, if it ever opens fully at all. If you only block the one on the driver's side, you should get enough heat to the choke thermo coil to fully open it, but it'll take longer than normal. In either case, you can wire the heat riser valve open.

[Wayne W.]

Re: 427/425 flooding

Probably has typical Holleyitis, dripping into the rear barrels when shut off.

[Clem Z.]

Re: 427/425 flooding

i ran all my HP chevys with the heat risers blocked both sides and even in Pa. winters. i just disconnected the choke and gave the engine a couple of pumps to the gas pedal,waited 10/15 seconds for the gas to vaporize and fired it up.