Has anyone head their heads ported/polished? If so, what what gains were made and where at in the RPM range. Also, if anyone has any information on the best angles for cut on the valve seats when porting/polishing this would also be appreciated.
If no one has done it yet, I will probably guinea pig it and see how it goes (will probably use the guys at DPR here in town).
Well, in your quest for more power, you are certainly headed in the right direction (no pun intended!) Porting and polishing heads, excuse me, head (I'm a V-8 guy) will most likely give you a little extra oommpphh. The downside to this, would be voiding your engine warranty (if you still have it, that is.) In my experience, along with port and polish, truing the deck, a three angle valve cut was pretty standard. I then upgraded to screw in studs, stiffer springs, higher ratio rocker arms (roller of course), new seals, and having the intake ports gasket matched. Half of this stuff probably doesn't exist on my Spec V head, so I won't try to come off like I know everything. I do know that there is always power to be made in the heads. If and when someone ever comes out with aftermarket cams, you will have much more to gain from this than someone with stock heads. If you can find someone who really knows what they are doing, and has a flow bench to test before and after, definately go for it!!!
Originally posted by olsaltybastard Well, in your quest for more power, you are certainly headed in the right direction (no pun intended!) Porting and polishing heads, excuse me, head (I'm a V-8 guy) will most likely give you a little extra oommpphh. The downside to this, would be voiding your engine warranty (if you still have it, that is.) In my experience, along with port and polish, truing the deck, a three angle valve cut was pretty standard. I then upgraded to screw in studs, stiffer springs, higher ratio rocker arms (roller of course), new seals, and having the intake ports gasket matched. Half of this stuff probably doesn't exist on my Spec V head, so I won't try to come off like I know everything. I do know that there is always power to be made in the heads. If and when someone ever comes out with aftermarket cams, you will have much more to gain from this than someone with stock heads. If you can find someone who really knows what they are doing, and has a flow bench to test before and after, definately go for it!!!
sorry, man. i hate to call you on this one, i'm a bit of a V8 man myself, but i don't think comparing a high-tech 4-banger with an old-skool V8 is a good idea. Automotive technology has come a pretty long way in the last 10 years. I don't know which v8s you're referring to, but most of the v8s i think of are carburated, OHV, 2-valve per cylinder, wedge-headed, square-ported, massive blocks of iron. unless you're dealing with aurora v8s, ford 4-cam v8s, infinity v8s, or other high-tech OHC v8s, i don't believe your experience will necessarily transfer. the effects of a port/polish would be less noticable on a well-designed modern engine such as the QR25...
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Lazarus has a good point that you will not gain as much as the ol pushrod 2 valve V-8. I can vouch that my ol E7 casted heads were junk but a well designed head doesnt need much work if almost any to improve it.
I'd say if you have the money go for it. But please be sure to get before and after results.
We'd appreciate seeing CFM flow before an after intake and exhaust side. Velocity is everything !!
Dyno the ride before and after to really see if the flow numbers make a difference.
And if you plan on doing full exhaust with other mods I am sure that the better flowing head will help. After all the engine is just a big air pump.
I've seen up to seven angle valve jobs. I believe there are even more angles than that.
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