Pocket Porting
 

Having a set of heads rebuilt and do not have money to have them professionally ported. Couple of questions maybe you guys could help me with and keep me going in the right directions.

502 with stock rect port heads fitted with 2.25 intake and 1.89 exhaust valves. Is it worth it for a home builder to pocket port and do some blending to help flow. I thinking minor work here nothing major from what I have read. Sometimes less is better than more.

I am also looking for all the information I can get on exactly what and what NOT to do. I have some information but more is better. Pictures are worth a thousand words as someone once said. Thanks if you can help.
:drink:

Re: Pocket Porting
 

I have rect. heads on my Gen 6 502's as well. Most of the articles I have read on rect. heads mention to clean up the exhaust side and leave the intake runners alone. When I took my heads off to have a valve job, I noticed alot of rough casting inside the exhaust bowl that could stand to be cleaned up which had the potential to create turbulence. Also, the exhaust pocket I expanded out to allow more flow of the exhaust gases. You can also clean up the short side radius and blend in as well. Easy - but be carefull that you blend and not gouge out too much. I wouldn't do anything to the intake runners. Gary

Re: Pocket Porting
 

If you are talented with a die grinder it is beneficial to do bowl port work. You can mildly clean up the intake bowl under the seat area. I would suggest positioning your seat with layout fluid so you do not get into it. Have you machine shop set the heads up so you know what not to grind. Keep a .030-.050 margin away from the 45 seat. Basically you want to remove excess material and shape bowl short turn. The exhaust pocket with net the most gain. The short turn side of the ex.bowl is very peaky. This side needs to be formed into a radius . Keeping consitricity and shape are very important. If done wrong you can actually go backwards. Do not touch intake runners at all.

Dean Gellner

Re: Pocket Porting
 

Thanks for the replies. You have confirmed my other research and confirmed my less is more comment. I am handy with a die grinder. I was thinking of just some cleaning up and work some on short turn radius but I do not want to get carried away and remove too much and hurt the flow. I have a couple of books that show some pictures and describe in some detail what you are supposed to do.

Recommendations on chambers other than stay away from spark plug holes - threads and valve seats? Thinking of de-burring - polish and cc them while I have heads a part.

Re: Pocket Porting
 

There are some picks on my thread.
http://www.offshoreonly.com/forums/s...t=500efi+build

Re: Pocket Porting
 

I have done a couple of sets myself on BBC. Look at the Standard Abrasives website, they have some good tips and you can buy their kit through Summit. I start by Gasket matching the Intake with the Heads and then work my way back not removing more metal than needed.

tptools.com has some nice long-reach burrs and other abrasives. Good pricing too.

Who has the long reach die grinders?

Heres the grinder I used ,its cheap but works
http://www.harborfreight.com/cpi/cta...emnumber=93621

http://store.summitracing.com/partde...5&autoview=sku

this should work for you . it's the mandrel length , this kit has a 4" which should work ok..
you can also buy the cone shaped abrasives at summit too...

UUUHHH... Make sure your heads don't have any defects or cracks before you spend all that time on them. ( Don't ask how I know)

Yeah to what he says! Not sure exactly what heads you have but what Kennyo says is especially true if they're the GM cast iron rectangle port heads. They have a tendency to crack between the seats. USED GM rectangle port heads are becoming easier to get because of all the other head casting options available from aftermarket manufacture's these days, but there is always the random risk of the GM rect heads cracking. I have seen it many times in Marine applications since the early 1980's. Some guys spend a lot of time/money on porting/preping the GM rects only to have them crack....but some guys are very lucky. It's a roll of the dice. If your wallet allows it try and buy an aftermarket casting like an Iron Eagle 308cc or something similar.

Ive seen and had the cracked head in the seat area before, They drill it out and put some kind of plug in it. I havent had a prob , But I guess it depends how big it is?

The "feel" of the exhaust port short radius surface is more reliable than visual do to location. Just rub your finger across it in the direction of the air flow and you will be surprised how sensitive that can be it finding non uniform spots to blend.

Thanks!!