Cylinder Heads - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 02-28-2016, 12:35 AM Thread Starter
 
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Cylinder Heads

Looking for heads found a set of 7M5 heads was told they're ram air IV but can only find that they are 250 hp heads from a 455 and will they even work on a 400
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post #2 of 6 (permalink) Old 03-04-2016, 08:00 PM
 
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They are NOT RA IV heads. They are 455CI heads, 250HP, 114CC chambers. Not any good for a 400 unless you want around a 7.3 compression.
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post #3 of 6 (permalink) Old 03-04-2016, 08:06 PM
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What the man done said.

You really have to be careful out there. These days there are tons more original Ram Air IV parts available for sale than Pontiac ever actually made.....

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post #4 of 6 (permalink) Old 03-06-2016, 01:09 PM
 
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Have yet to run across anyone offering (mis advertising) garden variety DPort heads as Ram Air 4's or other factory round port heads. Have pulled and bought, easily a dump truck load of Pontiac heads over the last 30 years...mainly 6X's.

Over the last decade, have ran across a few !diots referring to the 6X heads on their freshly bought driver GTO's, as RAM AIR heads...thought that was funny
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post #5 of 6 (permalink) Old 03-06-2016, 03:52 PM
 
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Are there any viable options for running Ram Air heads on a stock 400? I found some "ram air" exhaust manifolds on fleabay and was wondering what good they may do and if they have to be put on "ram air" heads or what? I'm going to build my 400 (or actually have it built) to around a street 400hp motor. Suggestions for my builder? I'm using Grose Racing out of Lodi CA for the build. I've been told they are the best local guys for Pontiac motors.
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post #6 of 6 (permalink) Old 03-06-2016, 06:48 PM
 
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Yeah, the Ram Air 3 D-port manifolds will bolt up to most D-port heads.

The easiest way to make 400hp is to put a 4.25 stroker assembly, into your 400 block(most any 400 block except those with a casting number ending in 557). Butler sells a balanced cast crank assembly for about $1600 or a little more shipped.

Butler Performance - Pontiac Engine & Rotating Assembly Combinations - Featuring Eagle Pontiac Kits

If you have a few hundred more to spend on the shortblock, you can get the stroker assembly with a forged crank, H-beam rods, and even Ross pistons. And by going with a forged crank, you can also go with a 4.21" 455 stroke, and Pontiac length 6.625 rods.

With this stroker shortblock you can use the 6x heads, and RA3 manifolds. The RA3 mainifolds are not quite as good as open headers. But, if you're gonna run a full exhaust system, the manifolds will be almost as good as headers.

There are several sources for the RA3 manifolds. RARE is one source. They are not cheap. Painted headers are much cheaper.

Pontiac Ram Air Manifolds

Max/Pypes also sell the manifolds.

http://pypesexhaust.com/i-22645243-6...5-rpe652h.html

" Are there any viable options for running Ram Air heads on a stock 400?..."

The round port RA heads cost too much. The D-port RA heads are cheaper, but still cost more than the 6x heads. Plus, they give a 400 too much compression for pump gas, unless you run dish pistons. So, for the price of the RA heads and dish pistons, you might as well add just a little more to it and go with a stroker and 6x heads. IMO
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Last edited by oldskool; 03-06-2016 at 08:13 PM.
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