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 5Likes
09-08-2022, 07:13 AM
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CC Member
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Join Date: Jun 2022
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Upgrade Headers
Hi All,
Currently running an era correct 289, looking to get into a 351W stroked out to a 427. My concerns are the headers that I have today may not be a match for my next generation build. I also looked at building a 302 stroked to a 347 and still feel the headers may be to small. Any suggestions on finding replacement headers? I also have a picture of the header size as an example.
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09-08-2022, 08:13 PM
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Join Date: Feb 2021
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wow, those flanges look thin. I saw somewhere in a past thread that there is a company that you can mock up your headers with a pvc kit and send it back and they make your header up.
https://www.gpheaders.com/products/custom-headers/ |
09-09-2022, 03:37 AM
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Since you are planning to change displacement,
This handy calculator can provide a starting point
for best header tube diameter and length considerations.
Primary Header Tube Length and Diameter Calculator |
09-09-2022, 03:39 AM
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And yes, those flanges look pretty thin.
Last edited by Unique427; 09-09-2022 at 03:46 AM..
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09-09-2022, 06:43 AM
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Senior Club Cobra Member
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Join Date: May 2007
Location: Longview,
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Cobra Make, Engine: Classic Roadster, 408 LSX
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Also remember if you go to a 351 block, the exhaust ports are a little higher and a little wider. Might or might not matter.
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09-09-2022, 06:56 AM
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Join Date: Aug 2000
Location: Pinellas Park,
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One thing to consider is that the firing order on the old 289 is different, meaning the pairing of cylinders on the left side of the engine is different for the new firing order which the 351 has making the headers different. With the 347 this same thing applies, the new firing order, if used in the 347 requires different header parings. This does not mean you can not use the old style headers with the new firing order, but it will not make as much HP and does change the sound slightly of the exhaust.
Bill K
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09-09-2022, 06:58 AM
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If you are running all four into one collector it doesn't matter.
Bill K
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09-09-2022, 08:23 PM
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Thanks!
I was thinking of going with 500 HP 347 Ford Small Block Stroker from PM.
Wanted to make sure the headers would not be an issue? I attached the link to the actual crate motor.
https://www.prestigemoto.com/custom-...347-hr-c3.html |
09-10-2022, 11:04 AM
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Cobra Make, Engine: Classic Roadsters 427, 5.0
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Those are thin flanges! What year was your CRII made? Mine is a 1990 kit (CRI) and not nearly as thin as yours. If you do go to a 351 block, it will lift the header exit mount and the opening at the bottom of the body will not align by about 3/4".
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09-10-2022, 11:25 AM
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The view of the flange is blocked by the valve cover. They are 5/16” thick flange, Classic Roadsters header.
They are to small for what you want.
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Last edited by sunman; 09-11-2022 at 08:40 AM..
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09-10-2022, 07:53 PM
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So basically I’m better of with staying with a 289 or 302?
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09-10-2022, 10:50 PM
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 A 331 and 347 stroker use the same block as the 302. Your choice of heads can vary between Windsor, Cleveland, or after market combination and cc. Your choice which direction you go, but improving the exhaust headers will benefit you in squeezing all you can from your chosen platform.
I had mine custom made to benefit my motor.
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Last edited by markantioch; 09-10-2022 at 10:54 PM..
Reason: picture
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09-11-2022, 02:46 AM
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Who did the headers for you?
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09-11-2022, 03:35 AM
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Who did the headers for you?
I still am trying to figure out if I buy a 302 crate motor will the headers on the car fit? I was going to go with a 347 striker but it sounds like the headers will not fit so I’m down sizing to a 302.
https://www.westcoastengines.com/302-engine |
09-11-2022, 04:54 AM
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In my opinion go with the 347, the headers should fit [b]Period[/B unless the heads are something really weird, a FORD crate 347 with Ford 304 heads should be a bolt in. You get into trouble when you use the 351W block because of the increased deck height.]
Bill K
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09-11-2022, 05:54 AM
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They were fabricated in Ohio, and the drivers side modified in Houston cus it was a lil to long. Material cost I don't remember, but the labor cost to build them was $400 back in 2015.
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09-11-2022, 07:14 AM
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Thanks Bill K!
Really want the 347 FORD SMALL BLOCK STROKER CRATE ENGINE: F347-HR-C3. I hope the existing headers don’t restrict the HP to much.
https://www.prestigemoto.com/custom-...347-hr-c3.html |
09-11-2022, 07:18 AM
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Thanks everyone for your advice! All good stuff!
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09-11-2022, 08:08 AM
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This is what you have.
The flange is 5/16”. The tubes are 1 5/8”.
The outside of the tubes are not welded and you can weld outside and enlarge the tube inside.
That’s good for the 302 but small for 500 HP tho.
If you go 347 maybe send them to someone to be duplicated in 1 3/4” tubes.
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Last edited by sunman; 09-11-2022 at 09:06 AM..
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09-11-2022, 01:26 PM
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Thanks!
Now you got me thinking, maybe I send my headers to a fab shop for fit with 1 3/4 across the board. Anyone know a good custom header shop?
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