Have I installed the wrong Headers?

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jim7485

Founding Member

Jan 5, 2002

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Michigan

Oct 12, 2006

#1

• Oct 12, 2006

• #1

66 Mustang with FRPP 302 crate motor w/GT 40 aluminum heads. We installed Hedman shorty headers, part no: 88400. The bolt pattern is fine, but there seems to be a fair amount of overlap, enough that I think flow may be restriced. The engine dude (more of a body man) told me it was normal, but I'm concerned. The car runs fine, but seems to lack power. Wondering if these headers are restrictive due to the overlap. They are correct for a 66-73 302. Question is: are they correct for GT 40 heads? I'm considering a switch to FMS-M-9430-P51 which I know are correct. Any thoughts? http://store.summitracing.com/egnsearch.asp?Ntk=KeywordSearch&DDS=1&N=+115&searchinresults=false&Ntt=FMS%2DM%2D9430%2DP51

Thanks
jim

 

brianj5600

Active Member

Sep 19, 2003

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39

Middle TN

Oct 12, 2006

#2

• Oct 12, 2006

• #2

I would contact Hedman.

 

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88dragtop

Founding Member

Sep 20, 2001

198

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17

Glastonbury,CT

Oct 12, 2006

#3

• Oct 12, 2006

• #3

I assume by overlap you mean the exhaust port on the header flange is smaller than the port on the heads? Even so I wouldn't think it would be as bad as a manifold. Hard to say it's losing power with the butt meter, dyno or 1/4 times would give you a better idea. Those FMS are late model headers and won't fit the early engine bay.

 

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truck90278

New Member

Jun 4, 2006

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Redondo Beach, CA

Oct 12, 2006

#4

• Oct 12, 2006

• #4

We're running the Hedman Elite with no problems. We initially had the GT 40 Aluminum heads and switched to Edelbrock Performer heads - no problems either way - no lack of power

 

Reactions: Metalgearmoogle

BullittStangV8

Founding Member

Oct 5, 2002

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NJ

Oct 12, 2006

#5

• Oct 12, 2006

• #5

Is it casting flash that could be ground down? Or simply the ports dont match up with eachother? (meaing part of the head port is covered, and the header tube extends part the port in the head)

 

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jim7485

Founding Member

Jan 5, 2002

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Michigan

Oct 12, 2006

#6

• Oct 12, 2006

• #6

More info....

A bit of clarification: The bolt pattern is perfect but the header flange holes do not match the ports. They are roughly the same size, but offset somewhat, perhaps 1/3 of each port is covered by the flange. Can I get some confirmation on an additional issue? Will the FMS-M-9430-P51 headers (which I know are correct for the GT 40 heads) fit between the shock towers?

Thanks
jim

 

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The Dan

New Member

Jul 16, 2003

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Orange County, CA

Oct 13, 2006

#7

• Oct 13, 2006

• #7

Is the flange covering the exhaust port from the bottom, or sides? You may have headers desiged for heads with raised exhaust ports???

 

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jim7485

Founding Member

Jan 5, 2002

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Michigan

Oct 13, 2006

#8

• Oct 13, 2006

• #8

Now that's a great question. As I recall, the overlap was on the sides. If anyone else is using the crate motor with GT40 heads, which shorty headers are you using?

Thanks
jim

 

J

jim7485

Founding Member

Jan 5, 2002

64

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Michigan

Oct 13, 2006

#9

• Oct 13, 2006

• #9

The correct answer

Here's the correct answer right from Hedman tech: Thank you for using Hedman Products. Part# 88400 is designed for a stock application. These hedders will choke the motor. So they will come off. I'll measure the clearance this weekend to see if the FMS hedders will fit between the shock towers. Obviously some cutting/welding on the H pipe will be in order too.

Thanks
jim

 

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The Dan

New Member

Jul 16, 2003

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Orange County, CA

Oct 13, 2006

#10

• Oct 13, 2006

• #10

Glad you got it figured out. Headers always seem to be a problem for people, myself included. Sometimes wonder if they're worth the problems....ya, I guess they are

Good luck.