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HP Gain After Port-n-Polish Head?

37K views 14 replies 8 participants last post by  DEFIANT_7M 
#1 ·
Does anyone know what a realistic horsepower gain I can expect from porting and polishing the 7MGTE head? I have a BHG and am considering PnP the head while it is out. A local performance shop said between a 45 and 75hp gain. Anyone with experience in this department? (I didn't see any hp results in the searches I performed.)

Thanks!
 
G
#3 ·
The problem is, there is no clear definition of "port and polish". It is a catch phrase thrown around without much merit.

Polishing alone is usually less than 2% improvement in flow. But it sure looks pretty, and most shops will call this "port and polish". Porting depends greatly what exactly is done. Some porting jobs take 20 minutes, some will take weeks or even months backed by flow testing, replacing valve seats, using larger valves etc etc.

All in all, spend your money elsewhere. You already have a 4 valve pent-roof cylinder head, most domestic pushrod engine owners would kill for.

Just get a good valve job done and take care of everything else that needs doing. That alone will cost plenty of money to do, and will provide huge performance increase over your old worn out engine.

Some more information if you're interested:
http://www.highperformancepontiac.com/tech/0210hpp_flow/
 
#4 ·
I was leary about those kind of gains... hence my post. The person this shop contracts out to port heads worked for Lozano Brothers for 9 years. The shop has two display heads (from Eclipse's) showing three different stages of work. This guy does a good job: he enlarges the intake and exhaust sides and smoothes and streamlines the pathways. He also includes before-and-after flow testing measurements.

The display Eclipse head looked like a fairly significant improvement-- larger, wider, smoother-- and the increased flow was supposedly equivalent to an upgraded cam. I searched Supraforums and found posts showing increased flow, but nothing about horsepower gains. If anyone has had a good port job done, I'd be curious what gains they saw. Otherwise, I'll put the money down on a hot date and partial payment for a Lexus AFM.
 
#6 ·
opening up your head isnt going to give you a clear gain either way. The gain you see will be dependent on how much hp you expect to run. Sure, 500 hp is attainable with a stock head, but with it cleaned up nicely with quality valves - it wouldnt be difficult to see 525 with the same inputs.... Also to consider, the hp gains they talk about are seen on NA engines, which play by a different set of rules.
 
#7 ·
I would deal with the stock IC piping, and routing (i.e. mk4 style...), more then some port and polish job, by billy joe...
 
#10 ·
Heck, 8hp could just be a different barometric pressure from one day to another. (Or air temp changes etc.)
I'd have to think larger valves, and porting to clean up any sharp edges near the seats, and casting joints should prove to be plenty. However, Defiant's porting guy has manged to get some very respectable flow numbers from the 7M head. It will be interesting to see if the 750.00 spent porting this head is worth the money in the end. (IF there is 75hp to be found, say from 3500rpm to redline, then I say it is. If not, I'll spend money on something else.)
 
#11 ·
well my brother had his ported and it was a great boost in power. Im guessing that you wont ntoice a difference. You might though. It all depends on how much work your engine has had and if you have a free flowing exaust. I hope i have had any help to your question.
 
G
#12 · (Edited)
adjuster said:
Heck, 8hp could just be a different barometric pressure from one day to another. (Or air temp changes etc.)
I'd have to think larger valves, and porting to clean up any sharp edges near the seats, and casting joints should prove to be plenty. However, Defiant's porting guy has manged to get some very respectable flow numbers from the 7M head. It will be interesting to see if the 750.00 spent porting this head is worth the money in the end. (IF there is 75hp to be found, say from 3500rpm to redline, then I say it is. If not, I'll spend money on something else.)
How are we going to figure what the head makes? So many things will be different and in place ie: compression change, stroke being the the two biggest other than the head work. We got stock numbers then this "INSANE" creation of mine. $750 is for the street port. Call me crazy I had a full race port/polish done, I'm in 1K^ land



Allan
 
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