Intake and exhaust porting

[Olie's87XJ]

Havent been here in a while, but I am still working on the ol' heep a lot.

As she sits, its an 87 renix 2 door. the engine is from a 96 HO YJ. the block has been bored .030" over, and it has a mid range cam. I'm running the '99+ intake and throttle body with the renix fuel rail and mustang 5.0L injectors. It has an APN header and 2.5" exhaust.

right now i am changing the head gasket, and was wondering if while it was apart, if i "gasket matched" or "port matched" the head and intake/exhaust manifold/header if it would be worth the work? has anyone had any experience with this? it seems the intake manifold could be opened up quite a bit, but will thinning it out cause heat issues being so close to the header? the exhaust ports on the head are also considerably smaller than what is allowed by the gasket. would it hurt to open them up too?

Thanks all!

[Stevew3]

I matched ported the exhaust and intake, and debured the block and head. Made a little more power.

[Cheromaniac]

right now i am changing the head gasket, and was wondering if while it was apart, if i "gasket matched" or "port matched" the head and intake/exhaust manifold/header if it would be worth the work? has anyone had any experience with this? it seems the intake manifold could be opened up quite a bit, but will thinning it out cause heat issues being so close to the header? the exhaust ports on the head are also considerably smaller than what is allowed by the gasket. would it hurt to open them up too?

I've home ported two 4.0L heads (including the one that's on my 4.6 stroker) so I can speak from first hand experience.
DO NOT gasket match the exhaust ports as hogging them out could cause reversion of exhaust gases back into the combustion chambers and a loss of performance.
You can port match the intake manifold runners and the intake ports in the head but don't go wild on the intake runners. It doesn't matter if the ports in the head are slightly bigger but you don't want the reverse. Even then the power gain will be minimal.
The REAL performance gain comes from pocket porting the valve bowls/throats by removing excess casting flash and ridges, trimming the valve guide bosses to a teardrop shape, and smoothening the short side radii so there's a nice even curve without ridges or steps.
I recommend that you read a few online DIY head porting articles and practice on a junk head before you start working on your own.

http://www.pirate4x4.com/tech/billavista/PDFs/Head%20Porting%20DIY%20by%20Standard%20Abrasives.p df

[Stevew3]

I did a lot of research and basically just cleaned everything up .

[NW99XJ]

I've home ported two 4.0L heads (including the one that's on my 4.6 stroker) so I can speak from first hand experience.
DO NOT gasket match the exhaust ports as hogging them out could cause reversion of exhaust gases back into the combustion chambers and a loss of performance.
You can port match the intake manifold runners and the intake ports in the head but don't go wild on the intake runners. It doesn't matter if the ports in the head are slightly bigger but you don't want the reverse. Even then the power gain will be minimal.
The REAL performance gain comes from pocket porting the valve bowls/throats by removing excess casting flash and ridges, trimming the valve guide bosses to a teardrop shape, and smoothening the short side radii so there's a nice even curve without ridges or steps.
I recommend that you read a few online DIY head porting articles and practice on a junk head before you start working on your own.

http://www.pirate4x4.com/tech/billavista/PDFs/Head%20Porting%20DIY%20by%20Standard%20Abrasives.p df

I know there are a lot of people that would be interested in seeing some pictures of this, and possibly even a write up if you are ever so inclined to do a tutorial for the masses..... :patriot:

[Cheromaniac]

I'm not expert enough to give a tutorial but this is the write-up on my site:

http://www.jeep4.0performance.4mg.com/head.html

Here are more useful articles:

http://www.popularhotrodding.com/enginemasters/articles/hardcore/0412em_porting_cylinder_heads/viewall.html
http://www.superchevy.com/how-to/95518-small-block-cylinder-head-porting/
http://www.diyporting.com/

[Olie's87XJ]

thanks everyone for the responses and links. unfortunately i recieved a terrible phone call today...

the machine shop i sent the head to to be resurfaced said it was cracked on #2 and #6 exhaust valves. its a boat anchor. guess that puts this little project on hold.:bang:

[KMW-NWXJ]

Sounds like you have a head to practice on now!

[4.3LXJ]

I agree, practicer on the boat anchor

[NW99XJ]

I'm not expert enough to give a tutorial but this is the write-up on my site:
http://www.jeep4.0performance.4mg.com/head.html
Thanks Dino! Good stuff right there!


thanks everyone for the responses and links. unfortunately i received a terrible phone call today...

the machine shop i sent the head to to be resurfaced said it was cracked on #2 and #6 exhaust valves. its a boat anchor. guess that puts this little project on hold.:bang:
LAAAAAAAAME!!!! :bang: sorry man.
Buuuttt......

Sounds like you have a head to practice on now!
^THIS!!!! :thumbsup:
There's a silver lining to every dark cloud.
;)

[Cheromaniac]

the machine shop i sent the head to to be resurfaced said it was cracked on #2 and #6 exhaust valves. its a boat anchor.

As the others have said, you now have a practice head to work on.
Cracking of the exhaust valve seats is typically the result of overheating.