litevette

I'm wondering how many "free" horsies I'll get from porting/matching my intake & heads. I know theres a lot of other variables involved, but it's a performer intake and stock heads on a mild cam 350 (300 h.p. when stock) engine. What could I expect? 2 H.P.? 3 H.P.? ?????? :rolleyes:


[Modified by litevette, 9:26 PM 3/10/2003]

litevette

OOOOOPS! Didn't need a poll there!

Shark Racer

Like any engine mod, it all depends on everything else.

You couldn't put 210cc racing heads on a car with a 300HP cam.

But I expect a bit of port-matching and cleaning up would get you a good chunk of hp, and if you go with a slightly more potent cam, and headers, 300+ hp is absolutely no problem!

-Steve

MotorHead

Never hurts to port match intake and heads to gasket. Serious head porting can get you some horsepower but usually you have to be running a high lift cam ( over .500 lift) to see any benefits.

You are probably in the right neighborhood, with 2-5 HP. :D


[Modified by MotorHead, 10:19 PM 3/10/2003]

flynhi

I did just this a few years back with a 355, performer, Crane 272, headers and a q jet.
Portmatching and do it yourself bowl and runner cleanup was necessary to take advantage of the other improvements. This engine dynoed at 305 hp and 325 ft lbs.

litevette

Thanks for the feedback! I hope I did it the right way. I used a air grinder then filed by hand until all ports were extremely smooth.

QuickVet

You may find a few :smash:

B

i don't think you'll get a lot but even if its 1 more thats 1 more than you had before and since its free what do you have to lose.

biggjimm

Hey litevette, If you do it right and have a few other components you will gain quite a bit of power and you can tell it when driving by the way it responds to sudden wide open throttle situations, I like those. If you have a intake a little bit of cam and headers and good exhaust system it will all work good together. An old timer once told me to think of an engine as if it were just a big air pump, which it actually is, but anyway,the faster and the more air you can move in and out, the better your engine will be. And remember it is a system, and you cant just change one part of it and expect results. Sometimes you just hinder yourself. And one more thing, if you are doing this porting yourself, dont take too much out of the bottom of the exhaust ports and dont change the radius of the bottom of the port as you will lose a lot of you low end torgue. good luck. biggjimm

Matt Gruber

the tests i've read over the years show no gain matching to the gasket. sorry

OatBoy

it'd say that depends totally on whoever is porting and how much they know.

litevette

Thank you to all who have replied!

Aaron-74

port matching the intake and heads has a very minimal gain. Bowl porting and such further mods often yeild better gains. Port matching really only comes into play when you're really trying to move a lot of air..IE over .500 lift with decent durration..

Aaron

If you'd like pics of an effectivly ported street head that you can do at home..shoot me an IM..

Aaron :chevy

Wrecked82

Aaron-you're probably right. Remember when this was the "thing to do" on an 82 (hey that rhymes). It was not worth the effort to do, to install, the money to buy the second one, etc. But I did, so there!

Aaron-74

Well, considering the size of the intake ports on the cross-fire. Then, yeah that gains some. But on standard intake ports and heads, it's so minimal that the 2 or 4 CFM difference you make isn't going to help. Besides, if you grind a head too much at the top center, you'll hit the valve cover bolt taps and get a vacuum leak..which no one wants. It's best just to get obstructios out of the airs path so it has one smooth course from carb to cylinder. That helps driveability and might add a little power..

Aaron :smash:

Aaron-74

Larry- Take a look at my stock Air-Gap runners,compaired to a cross-fire intake (i'm sure you have a picture or know from memory)




Porting this part of my head would have given me too small of a gain and possibly aroused more problems if I had hit the valve cover bolt tap. Newer heads are thicker and gernerally are pretty close to being gasket matched..but these older thin heads are too thin to reallllly get tearing into..




[Modified by Aaron-74, 5:49 PM 3/19/2003]

Twin_Turbo

"porting" the port near the manifold where that perimiter bolt hole is does nothing unless you have seriously tackled the rest of the port. On the crappy smog heads the best gain can be had by removing irregularities and casting flash. Also, enlarging the bottle neck just behind the seat is a good thing to work on. As far as porting, there's no room in the thin castings for some serious work and without a real thorough idea of port shape and what flows best you most likely will create a port that will flow worse. This isn't exact science, it's more of an art. If everyone could just copy it out of a vizard book then the quality head porters would be out of business and they aren't. They work on a flow bench and use it to trial and error their way to an effective port shape.

If you want some serious flow, get some new heads.

Oh, and about that perimeter bolt. If you're dead set on grinding there, there's an easy solution. Get some valve cover studs and epoxy them in. Then you can grind all you want there.



[Modified by Twin_Turbo, 6:06 PM 3/19/2003]