Head Porting question

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Badart

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Would it be worth it to port or at least gasket match a set of 318 LA heads (675 castings, small valves, no smog ports)?
The bottom end of the motor is a bone stock fresh rebuild. Comp cams XE256 cam, lifters and springs. Performer intake. Holley 600 carb. Hooker competition headers. 3" dual exhaust with flowmasters. I am going to have the heads milled .060 and going with a .028 head gasket to bump up the compression ratio a little.
Magnum heads or 302 castings are out of the question. These heads are fresh and don't want to waste them.
Would it be a waste of time? I plan on at least cleaning up the runners a little. Thanks
 
I will be straight forward.....get some 302' casting heads, and gasket match them, and plug/weld the smog ports....then it will be worth it
power-wise and you won't have to cut .060 off the decks.

and I can make it even easier, I'll sell you a bone stock set for $150 + shipping....I checked shipping recently for a set of 360 heads to Illinois....$65 each.

I have a 88' 5th avenue I can pull them off of
*just re-read your post....nevermind.
 
Prine said:
I will be straight forward.....get some 302' casting heads, and gasket match them, and plug/weld the smog ports....then it will be worth it
power-wise and you won't have to cut .060 off the decks.

and I can make it even easier, I'll sell you a bone stock set for $150 + shipping....I checked shipping recently for a set of 360 heads to Illinois....$65 each.

I have a 88' 5th avenue I can pull them off of
*just re-read your post....forget my offer.
Click to expand...

Thanks Prine. Sorry I edited my post while you were replying. These heads only have about 5k miles and I would like to use them.
 
Its worth it. If you port them yourself, you will learn a lot for your next heads!And, you dont really have to worry about messing up because they can be easily replaced.

You will pick up a little flow and a lot of experience; Worth it!
 
No problem, I didn't mean to sound crass....I could've swore you didn't mention the solid intent to keep those heads....and saw it after I typed out a reply.

I agree with Grinder....it is worth it, maybe 5-10hp to gasket match and clean up the ports....and the experience you gain from doing stuff like this yourself is irreplaceable.

You'll also gain alot of understanding of what goes into a fully ported and polished heads (not CNC ported). It is not uncommon to have 25+ hours into a set of heads, and there are only 16 ports to do.

Make sure not to burr/dink the valve seats...or a valve job will have to be redone.

On the intake side it is important to not polish the walls/floors/roof like to a mirror smooth finish, and leave it semi-rough so the intake charge stays in a atomized state....and does not puddle and run and drag through the port.

On the exhaust side the finish is not so important, but I always just do both sides the same..I use a variety of carbide cutters with a die grinder and finish with the disposable abrasive polishing rolls you get with a porting/polishing kit.

Good luck....:rock:
 
I dont think you'll notice much, and if the heads are assembled you have to take them apart to clean.
 
id say any porting on them heads is worth it, follow up with hand lapping the valves and if you can have them milled,
 
The most gains are to be found in the area just below the valve seat. Open them up to the valve seat width, then gasket match (it's not crucial that it be exact here) and open the pushrod pinch as much as possible with out going through the wall. If you do just JB weld or epoxy it back it up, it will be fine. If you really want to get fancy smooth the guide protrusion and give it a tear drop shape.
 
I think the experience would be good, if nothing else. When I get new heads, I plan on experimenting with the heads that are on it, which are 302's.
 
boy if I knew how to port, I could make a crap load of money off my friends haha
 
Thanks alot guys for the input. I figured since I have to tear down the heads anyway to have them milled I should clean them up and help them flow a little better. This will be my first attempt at porting and will not get too carried away.
 
I looking at building a flow bench to port a set of 302 heads when I get the cash....I have book at the house called practical gas flow, it is a short in depth look at home porting any set of heads and has plans on building a simple yet effective flow bench out of common household stuff....
 
hi, do most the work in the bowls, blend the sharp edges, taper top of guides some.do not gasket match! port match is way better. reason is, if you open up the port at flange, it creates a big bulge in the air flow path. the air has to fill it before it can move on, this causes slowing of the air movement, lose of port velocity! port velocity is what fills the cylinders. anything you can do to raise port velocity is helpful. do not grind out the bowls, keep a venturi shape near the seat area, this helps to speed air back up after going around the corner. which relates to velocity. BTW , this is from super flow, they don't sell heads!! just food for thought.
 
perfacar said:
hi, do most the work in the bowls, blend the sharp edges, taper top of guides some.do not gasket match! port match is way better. reason is, if you open up the port at flange, it creates a big bulge in the air flow path. the air has to fill it before it can move on, this causes slowing of the air movement, lose of port velocity! port velocity is what fills the cylinders. anything you can do to raise port velocity is helpful. do not grind out the bowls, keep a venturi shape near the seat area, this helps to speed air back up after going around the corner. which relates to velocity. BTW , this is from super flow, they don't sell heads!! just food for thought.
Click to expand...

Good to know. Thanks.
 
I was just reading the gasket match part... You can get power with the right porting. If you've never done it, less is more! It's the right shape, not the size that counts, so when you find yourself wanting to make every surface shiney and as big as you can, you are screwing it up...lol.
 
I have weighed all of the pros and cons of porting the heads and I have contacted a machine shop down the road and he said that magnum heads are the only way to go and that he would help me out with doing a valve job on the cheap if I could find a set. This guy works out of his shop at home and doesn't even advertise. After calling about 5 wrecking yards I found two sets that I could pull for $75 per set. I think I will pick up both sets and do some trading. Thanks guys.
 
If your goal is magnums, you may spend twice that to find out they are cracked. You might look into the Engine Quest magnums. You can get them new, stock, assembled for something like $600pr if you look around. You will have close to of more than that in magnufluxing, initial cost, and parts in yours quickly. Assuming you find a non carcked set. Just a thought...
 
Yes, Watch out with used magnum heads... they are very commonly cracked. If you do decide to port your old heads you will what to do it before you have the valve job. that way if you screw up and nick a seat... the valve job will clean it up.
 
IMO a gasket match alone is kinda not worth it unless they are way off.

I recommend that if you do gasket match to leave it just a hair smaller then the gasket unless you are pinning the manifold/head/gasket to keep it stationary, oh and don't gasket match the intake manifold bigger than the head ports.

If you do decide to disassemble the 302's and gasket match you may as well
raise the roof .030 blending it to the bowl roof 'don't raise the roof above the valve at this level' and profile all the int guides long and skinny, I wouldn't touch the short turn 'just off the seat' area till you read up and or look at some detailed pictures of how to properly do it.

oh and I think it's something like for every 5cfm=10hp
good luck!
 
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