Filled exhaust crossover

Discussion of the 331-354-392 HEMIs.

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NE57
Posts: 192
Joined: Fri Mar 27, 2009 12:54 pm

Filled exhaust crossover

Post by NE57 »

My heads, which I bought finished up, have the crossovers filled with what looks like a grout/mortar type stuff. Since this will be a street motor, I'm looking for pros/cons of leaving it as is or removing it.

Obviously cold driving would be better with them cleaned out but is there a possibility of some of the fill finding its way into a cylinder, whether left intact or cleaned out?

Anyone have an idea as to what ambient temp it becomes necessary to have the heated intake manifold? Indeed, would the exhaust even go thru the intake manifold without a heat riser on the exhaust manifold/headers?

Thanks
George
Posts: 694
Joined: Wed Aug 25, 2004 4:12 pm
Location: Fl

Re: Filled exhaust crossover

Post by George »

I installed an Edelbrock performer on a 302 Cleveland that someone had filled the crossover in the intake, so far no problems.
oldngood
Posts: 121
Joined: Thu Mar 13, 2008 5:14 pm

Re: Filled exhaust crossover

Post by oldngood »

The filled x-over will run just fine in hot weather, actually you won't even notice the difference, or the car will run better- the intake will definitely run cooler without the x-over heat.

In cold weather the car will take a very long time to run smoothly.

Use a block off type intake gasket to complete block the hole between the head and intake, or cut a small square piece of steel shim plate and sandwich it between intake gasket and head, and block the hole- this way you can block intake heat without filling it, if you wish.

of course this method doesn't improve the exhaust flow, because the center 2 exhaust ports empty into a common large chamber on the hemi heads. One purpose of filling them is to keep the exhaust port flow of the 2 center ports separated and to contour the port to flow better.
392heminut
Posts: 488
Joined: Sat Nov 30, 2002 2:16 pm

Re: Filled exhaust crossover

Post by 392heminut »

I ran my 392 with the Hot Heads dual plane intake, which has no crossover, with no problems. The carb I ran didn't even have a choke on it, it was a Holley 750 vac. sec. carb with a Proform body. Of course, we're only talking in the 30's here in the mornings during the winter (southwest New Mexico). I only had to stay on the throttle a few minutes to get it to a driveable condition and only a few more minutes of driving to be able to idle at stops. I'm using the same carb with a Mopar Performance intake manifold on the 5.7 hemi that's in the car now. The 5.7 has no provisions in the heads for a crossover to heat the intake. I have the same driveability conditions with it that I had with the 392 on cold mornings.
Owner of the Poor Man's Hemi Cuda
NE57
Posts: 192
Joined: Fri Mar 27, 2009 12:54 pm

Re: Filled exhaust crossover

Post by NE57 »

Grat! I won't worry about it then.

Thanks guys.
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