Extrude Honing

[mbrunson427]

I decided to run a set of exhaust manifolds on my 428 project instead of headers. Standard bore and standard stroke 428, BBM heads, hydraulic roller cam, C7ZX 2x4 intake, going in a '67 Mustang. Just bought a set of CJ exhaust manifolds for it and I'm tossing around the idea of extrude honing. Has anyone here ever done it? Is it worth it? Not shooting for any land speed records here, just trying to build a good looking and above average performing engine to replace the 390.

If anyone has any experience, let me know you opinion. If you've got a positive opinion, let me know who you sent them to. Thanks,

Mike

[jayb]

I have a friend who extrude honed a set of 428CJ exhaust manifolds for his mostly stock engine.  Said it made no difference in power.

[Joe-JDC]

All extrude hone does is polish the surface.  It will not effectively port the manifolds for you.  It will make them modestly larger IF THEY run the putty through several times.  They charge accordingly, and will not guarantee against holes if they do that.  If you are serious, you need to take a carbide or stone and round out the sharp edges as far into the manifolds as you can get, and open up the flange at the exhaust pipe to 2.5" or so, and then send them for extruding.  I have had to hand port several intakes after the extrude did not increase the flow like the customer was expecting.  Joe-JDC

[mbrunson427]

In that case, I'll clean them up with my die grinder and call it good. Thank you guys for all the help.

[Rory428]

Just curious as to why you would spend some much $$$$ on good pieces, only to choke it all up with exhaust manifolds? With aluminum heads and a 2x4 setup, you obviously are not going for a stock look, just curious why you would throw so much power away?

[Joe-JDC]

Extrude hone is Extrude Hone.  They usually charge a minimum of $350.00 per piece, and for additional removal they charge more.  Easily cost you $1,000.00 plus shipping each way.  Intake manifolds ~$700.00 up.   Joe-JDC

[mbrunson427]

Just curious as to why you would spend some much $$$$ on good pieces, only to choke it all up with exhaust manifolds? With aluminum heads and a 2x4 setup, you obviously are not going for a stock look, just curious why you would throw so much power away?

This car isn't meant to be a wild street car......my grandpa bought the car in 1972 when he was building NORAD, got the Mustang for a daily driver to drive up the hill and take the corners. It's kind of the family heirloom. We aren't interested in keeping it bone stock, because my grandpa toyed with everything and it was probably only ever stock for the first day he owned it. Trying to use parts that he could have gone and bought from Ford at the time (minus the BBM heads). When it's done I want it to be something that you may have seen in 1972 with the speed parts available at the time. I had bought a set of REF headers for it, and decided that they didn't fit the criteria. If this motor makes 450hp, it'd be plenty. If there were dramatic gains to be seen from extrude honing, i'd go for it. From Joe and Jay's responses above, I'm going to punt on that one.

I've got another Mustang project that is meant for speed parts....heads coming from Blair soon. REF headers are going on that.

[Autoholic]

It sounds like your grandpa is the kind of guy who would have wound up putting headers on his DD. He wouldn't have done it just for a small power increase, but a better exhaust note too. Headers were around back in the the 60's and 70's, Gary Hooker started in the 60's in Hot Rod heaven, SoCal. So if you want to keep it era appropriate, buy a set of Hooker headers. If you're worried that they won't fit in with the look of the engine in the engine bay, you could have the chrome stripped and painted with a matte black ceramic coating.

[FElony]

15 or more years ago one of the Mopar ragazines discovered the same thing. They tested extrude-honed 440 HP exhaust manifolds back-to-back on the dyno, and discovered very little improvement. Something like 4 or 5 horsepower for several hundred dollars spent. For the money, I'd look at aftermarket stainless shorties first.

[Autoholic]

I'd imagine extrude honing would be more effective on cylinder heads and intake manifolds. Engine Masters did some tests on headers that was very interesting. At one point, they banged the hell out of the headers and the engine still made roughly the same amount of power.

https://www.youtube.com/watch?v=azPKIjxmmdU

They've also done manifold vs mid length headers vs long tube headers

https://www.youtube.com/watch?v=Y7_lSU3D0jw

[Joe-JDC]

Ford used extrude honing process on their Contour SVTs to increase the performance.  They extruded the intake, intake port of the heads, and the throttle body and attachment.  Supposedly went from 180hp to 202hp with heads, intake, and throttle body.  I had one of them for a few years, and it ran great, was just too stealthy for its own good.  Trucks kept trying to run over me like I was invisible.    Joe-JDC