After running the engine to operating temp, not overheating in any way. The primary jets start to drip fuel after about 5 mins. Meaning a hot start is sometimes a challenge.

I made sure the accelerator pump arm is not touching the throttle linkage.

Car runs very well, and I still have the exhaust valve installed on the passenger side.

Does anyone know (or have tried) a 1" carb riser?

 

Welcome to the Forums, You can use a 1in spacer if you have the space under the hood to do so. One way to check that, if you have anything like playdough make a ball the size of a golf ball, place in on the top front of the air cleaner and close the hood and that will tell you how much space you have with that air cleaner. The spacer should help with manifold heat and add 2 to 3 HP. Is the exhaust valve opening properly? It should open after a few minutes of warm up. If not check the vacuum components, servo-lines and vacuum thermatic valve. I believe you have a Q-jet carburator if it's stock. You might want to check the float level in the carb, making sure it's not set to high (around 3/8 of an in.) and making sure the float is not saturated and the needle and seat are working properly. If the rubber tip on the needle gets hard it will raise the fuel level. I would check and see when the carburator is removed that the fuel well plugs on the bottom of the full bowl have been epoxyed. If they leak that doesen't help with hot starts. The 3/8in spacer between the manifold and carburator on Q-jets are usually sufficient most of the time for heat transfer to the carb. Good Luck.

 

Welcome to the forum.
I agree with everything that Thomas said. If it is in fact still a Quadrajet carburetor then you might as well go ahead and do a complete rebuild. It's relatively easy and inexpensive. If the engine is stock, then I don't think the spacer would be required.

 

First thank you.

The carb is stock and is a Holley Vac Sec 780cfm.
The carb was rebuilt but talking with some other guys, its seems the 396 runs hot.

I was just hoping someone would know if a 1" spacer would work.

Any suggestions on a good 1" spacer?

 

There are many 1in spacers made. If you are worried about heat transfer, I would suggest a Plastic or a Fiber spacer that won't transfer heat like a aluminum does. Summit racing, Jeggs and Amazon are a good source of spacers. The only time I had a BB run hot was because I was trying to use a Old small block Brass radiator. Once I went to a thick aluminum radiator there was never a heating issue, even on 100 degree days the temp gauge never moved even with A/C on.

 

What is the engine water temperature when fully warmed up before you shut it off?

 

The temp gauge gets to just below 215. It never goes above and it has the larger factory radiator.

 

You might be battling a few issues here. It needs more thermo insulation under the carburator, have the base gaskets and plates been altered? This engine and carburator was not designed for Ethanol blended fuels, making the fuel easier to boil. Unethanol fuel might help. You might want to consider pulling the intake manifold and blocking the exhaust crossover under the carburator to reduce the carb. base temperature. Or you can try locking the exhaust riser in the open position, might help with some of the heat. It might take some work to fit a 1" spacer under the carb base. I noticed Amazon had a wide variety of spacers.

 

Lower your float level a little.

 

Tested all week and while it has not been “summer” hot, the car did not have vapor lock after the carb was rebuilt.

so I’ll keep testing.