I just switched my intake manifold over from a 2 barrel to a eddlebrock perfomer 4 barrel. I just also bought a 4 barrel eddlebrock carb. It didn't come with a spacer and I wasn't sure if I needed one?

 

If you have heat soak problems, perhaps a thin phenolic spacer, but otherwise, no.

 

Did your intake manifold gasket block exhaust cross over passage?

 

I have not installed it yet. The motor has not been fired sense being rebuilt so I don't know if it will have heat soak problems yet.

 

Good.
Make sure intake manifold exhaust crossover passage is blocked by intake manifold gasket.
I prefer as much spacer as hood clearance allows; for performance as well as heat insulator purposes.
Spacer is easy to install and remove so it can be done anytime.

 

See if you can find some exhaust crossover passage restrictors. They aren't much more than pieces of sheetmetal with a small hole, maybe between 1/8" and 3/16".

The idea is to restrict the amount of exhaust gas that passes through the intake manifold without blocking it off entirely. Idle and off-idle behavior in cold weather and during warmup any time is improved when you heat the intake manifold at least a little.

Keep in mind also that if you are using headers or have removed any valve on one manifold that there isn't going to be much exhaust flowing through the crossover anyway. No pressure difference between exhaust banks = almost no flow.

If you use a spacer, you might end up rejetting or otherwise reworking the carb, and what you have to do will depend on the kind of spacer used (open, 4-hole, tapered).


Norm

 

If you run into a fuel boiling issue, you will seek every trick in the book to cool under hood temps and carb.

I've read the exhaust crossover will improve extreme cold weather reliability and mileage. Does not help initial cold start. Will help idle smooth out quicker from what I understand. Interesting that my OEM 65 w/ cast iron intake manifold exhaust passage is more cold natured than my HP 67 w/ blocked exhaust passage aluminum intake manifold.

I haven't had any issues driving in 20F temps once warmed up w/ blocked exhaust crossover.

Couldn't comment about sub 20F driving.

I'm interested in more exhaust crossover data and info.

I did not have to rejet my carb when I installed 1/2" spacer.

 

When you do get a spacer buy a phenolic. Not aluminum

 

Roger that.

 

I am probably picking up this spacer as my next Mustang purchase.
http://www.summitracing.com/parts/SUM-G1404/?rtype=10

Sounds like it may be what you need also.