Ported and or extrude honed HP exhaust manifolds

[Stephen Richins]

I am wondering if anyone on here has had or know anyone that have had their HP exhaust manifolds ported and or extrude honed and if so do you feel like you gained anything? I am going to be rebuilding the 440 in my Imperial & when I do I am going to do a few things to build more power id like to get to the 450-500 hp range but I will definitely not be doing headers I just don't want the hassle of headers

 

[CBODY67]

For a vehicle that heavy, think TORQUE rather than horsepower. It's torque that cooks the tires, not 5000rpm+ horsepower. Build an engine that makes great low-mid-range torque but also will easily hit 5000rpm. That torque will make things happen in the normal driving rpm ranges.

Once the torque is there, use a 2.5" exhaust system to ease the flow THROUGH the engine. Extrude Hone is the better way to do things, no matter what.

CBODY67

 

[Davea Lux]

If you have had port work done on the heads as part of the build, the exhaust manifolds should be port mated to the heads to cut down on turbulence. The high performance manifolds flow better once you get to about 4k rpms, you won't notice much difference below that. You are going to need an aftermarket cam to get to 450-500hp and that will also mean high tensile valve springs such as the dampered springs run on stock high performance mopars. You are also going to need a torque convertor with a higher stall speed than the stock unit. Probably somewhere in the 2500 rpm range and a set of 3.23 or 3.55 gears to get the beast to move. As noted, you have a very heavy car and the engine needs to be a torque monster, not a race engine. You might also want to consider a 490 stroker kit with a milder cam to accomplish torque aspects of the build.

Dave

 

[Carmine]

If you're talking about extrude honing, I would think you're familiar with the FAST racing series? Those guys aren't exactly giving up all their secrets, but occasionally you can find the details of their builds. That's the direction I would take if you want a boost over stock. You're obviously not looking for a 10 second 1/4 mile, so you can dial back some of those builds and keep costs reasonable and drivablity good.

 

[Stephen Richins]

If you have had port work done on the heads as part of the build, the exhaust manifolds should be port mated to the heads to cut down on turbulence. The high performance manifolds flow better once you get to about 4k rpms, you won't notice much difference below that. You are going to need an aftermarket cam to get to 450-500hp and that will also mean high tensile valve springs such as the dampered springs run on stock high performance mopars. You are also going to need a torque convertor with a higher stall speed than the stock unit. Probably somewhere in the 2500 rpm range and a set of 3.23 or 3.55 gears to get the beast to move. As noted, you have a very heavy car and the engine needs to be a torque monster, not a race engine. You might also want to consider a 490 stroker kit with a milder cam to accomplish torque aspects of the build.

Dave

yeah thats pretty much where I'm headed with the build was thinking of doing a 440 source stroker kit to put it somewhere around 500 CID & possibly a gear vender if I feel it needs it after going to lower gears and probably a Holley Sniper EFI setup

 

[Turboomni]

I researched this possibility of extrude honing HP's. Didn't hear much improvement in performance. Extrude honing is indiscriminate and just bulldozes through any obstuction [or tries to]. Some guys reported their HP manifolds cracked as they became weaker as a result. Also extrude honing is expensive. I would think a better way if you know what your doing is porting them by hand.

 

[stubs300]

Not a V8, but still! Read: Exhaust Manifold Mod

 

[MAGNUM77]

I know one of the Mopar Magazines did a article on this years ago. And there were some gains but not much on the dyno from what I remember and it’s expensive to have it done.

 

[Stephen Richins]

I know one of the Mopar Magazines did a article on this years ago. And there were some gains but not much on the dyno from what I remember and it’s expensive to have it done.

Extrude Hone AFM quoted me $800 & if it works well in my opinion it is money well spent cause I just plain hate the constant maintenance of headers but obviously if there isn't really any gain then why bother

 

[Turboomni]

@MEV ran mid 12's in his 4 door 3700 pound NewYorker with HP's and I don't believe the manifolds were ported. What I have read on FBBO 500 hp is very doable but higher 500 hp and 600 and up is tough with HP manifolds.

 

[MAGNUM77]

I believe this is referring to the article I was talking about Anybody remember Extrude Honing?
I will over the next few days try to find the article I believe it was 10 hp gain but don’t hold me to that.

 

[furious70]

Extrude Hone AFM quoted me $800 & if it works well in my opinion it is money well spent cause I just plain hate the constant maintenance of headers but obviously if there isn't really any gain then why bother

If your headers require constant maintenance you're doing something wrong.
$800 for 2-10hp is not very cost effective for the average Joe build. It would buy you a set of headers that wouldn't require any maintenance and would improve performance everywhere. And that's been Dyno proven.

 

[Stephen Richins]

If your headers require constant maintenance you're doing something wrong.
$800 for 2-10hp is not very cost effective for the average Joe build. It would buy you a set of headers that wouldn't require any maintenance and would improve performance everywhere. And that's been Dyno proven.

Well maybe you can enlighten me on the brand to purchase I have had headers from numerous different manufacturers & used numerous different gaskets some have worked better than others but the end result has been the same tick tick, tick tick so if you have any wizardry skills please fill me in

 

[Alchemi]

Easy, spend the $800 on custom built headers at a reputable shop.
If it goes tic tic tic afterwards, they will have to fix it.

 

[furious70]

I've used $50 swap meet headers to brand new ones. Your heads needs to be flat, the headers need to be true, then anything works. I've used oem manifold gaskets or the more expensive graphite impregnated gaskets. Put some copper rtv on both sides. No ticking.

 

[twostick]

Well maybe you can enlighten me on the brand to purchase I have had headers from numerous different manufacturers & used numerous different gaskets some have worked better than others but the end result has been the same tick tick, tick tick so if you have any wizardry skills please fill me in

Tti.

https://www.ttiexhaust.com/TTiC6573-440178.htm

Kevin

 

[Toolmanmike]

No doubt smoothing the ports will help flow but at what cost per horsepower gained? Along with the extrude honing the ports will be enlarged which makes more horsepower than the smoothing but how much material can you take out of a small port. You can't take more material than the design allows. Here's a center port of a small block manifold that has been extruded.

 

[BigblueC]

View attachment 459440

Was that one extruded? It looks a little too smooth to be a hand port.

 

[70bigblockdodge]

Don't tighten the hell out of the collectors, and use the factory studs and don't overtighten them either.
I know your not overtightening them, so only tighten half of your "not overtightening".
If your headers are leaking you did it wrong......period.
Extrude hone is good money after bad.
Manifolds suck.

 

[stubs300]

Not a V8, but still! Read: Exhaust Manifold Mod

Hey douchebag: Did you even read read what I posted? Evidently NOT!