Outer Limits 4x4 Board

Hi all,

I wonder if anyone has tried porting and polishing their heads? Make a big difference?

I have an HZJ79 with 1HZ turbo and might take the head off this winter and polish it up.. Suggestions?

I have also heard of guys putting bigger valves in ther heads for bettter air flow - anyone try that?

Regards,

Louis

Here is a post from the IH8MUD.com board, Peter has built some pretty amazing trucks and knows his stuff. Check it out:

"All you no-polish nay-sayers are WAY wrong.

Marc Ritchie polished the head in his 3B turbo'd rig. He pushed 38" boots at 75mph pushing 17lbs of boost to the Rubicon and back in the heat of June in the Nevada Desert. 2.5" straight pipe. No Problem. No overheating. TONS of power.

Polishing in the Cummins world is very common. EGT's go down by almost 200 degrees. On the new 24V common rail engines, you can gain 100hp.

Herb has a polished 1HZ head on in his turbo'd 80 series. He cannot make over 1000 EGT's while accelerating up hills at full power.

I will polish every turbo project I do again in the future. In fact, polishing is probably the thing I would do immediately after an upgraded exhaust and fitting a turbo. Polishing is what I recommend to those that are fighting with overheating issues.

Everyone with a turbo diesel should be polishing their head. Polish your head.

Peter Straub"

And,

"I did a 1HZ head (that's in Herb's 80) and Marc did a 3B head.
I didn't remove any material from the 1HZ. just polished it.
First, I strip the head bare. remove valves, guides, etc.
Then start with a die grinder with a burr bit, and grind down all the casting marks through the chambers.
the 1HZ head is well engineered, with no need to take significant material out to make a nice straight port. It was basically straight already. I took a tiny amount out on the inside radius of the turn down to the piston. Then I found a flapper wheel of the right size, and plunged that into the round holes. It works lesser good on the oval ports and in the valve chamber.
I bought a head polishing kit, which consists of a number of sand paper bits and a sand paper holder. Go from rough to smooth. I actually finished the head with 1500, 2000, and 5000 grit to get a mirror finish. Polishing a diesel head is a bit different than a gasser - in a gasser, small amounts of roughness on the intake side is required to provide a bit of turbulance to keep the fuel in suspension. In a diesel, smooth like a mirror is best.
Then, slowly, excruciatingly, do each cylendar. I think I did one per night, 2-4 hours each night. You're air compressor isn't going to like you very much.
One thing I bought was an extension for the die grinder. Kind of a 1/4" extension about 6" long. very nice.
Peter Straub"

in regards to outright flow, shape is more important the surface finish.

petrol engine don't like a polished intake ports because they have wet flow.

deisel on the other hand has dry flow (in comparison to a petrol engine)
and the small gain for little effort would be worth it, IF you already had the head off.

i wouldn't take a head off just to polish it, but if you had it off for other reasons then yeah it's be worth the time and effort to do.

highly polished port also resist carbon build up.

Whenever i have a head off anything i get the die grinder out and give the ports a clean up, never polish them but get them pretty smooth and using the gaskets match them to the manifolds.

I've been polishing the combustion chamber of cast iron heads for years, petrol engines love it as more heat is reflected into the combustion process and less absobed into the head, this improved efficiency, keeps the head temperature down and cleans up emissions. I have taken to HPC though.

Cheers

Joel

Loanrangie wrote:Whenever i have a head off anything i get the die grinder out and give the ports a clean up, never polish them but get them pretty smooth and using the gaskets match them to the manifolds.

x 2 and polish them up a bit aswell.