Polish your head???

[lshobie]

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

[dazzler66]

All good stuff to do if you know what you are doing.

The best thing IMO for a non performance head builder (thats most of us I think) is to smooth the flow where the exhaust and inlet manifold meet the head. There is always a step or some misalignement where thes meet.

When disassembled bolt them back on bare and then drill through some meaty spots on the manifold and head the same size as a small rollpin (3mmish). The roll pins ensure alignment when you bolt back up each time.

Then blue up the faces and bolt back on.

Once dry it will show up where the overlap. Out with the die grinder and smooth it all off.

There is also differing opinions amongst the racing crews re polishing. Some say that the important thing is flow not polish and that the time must be spent redesigning the head to get the flow correctly. This is obviously very expensive and a lot of trial and error hence expense.

The other issue is that some say that if its too higly polished then the fuel mix can 'bead' and not remain atomised (not an issue in a diesel though) and a smooth but not polished surface is fine.

My 2c though is a diesel isnt flowing enough air to make much benefit of anothing other than cleaning up the surfaces.

good luck

[dhc4ever]

Ive been looking into this and have basically come to the same conclusions as dazzler66.
Cleanup the dags and joint misalignments and smooth this out, polishing may be of some MINOR help to a diesel as all this part of the engine is in contact with is air only, unlike a petrol which seems to need some turbulance to help mix the fuel.
Cost and performance wize you'll probably get better results from a bigger dump pipe, free flowing 3 in exhaust and an getting the pump and injectors set up to suit.
But hey if the head HAS to come off it might get a small improvement if you match port and flow it, just probably not really worth it on its own, when you look at the time involved and the cost of gaskets, headbolts etc.
Bigger valves eh, interesting concept on a TD diesel. Wont be cheap, it would be worth talking to the professionals on this as diesel valves and seat cop a canning at 18:1 compression + boost. Give westend or berrima diesel a ring if any one knows it would be these guys.
Good luck with it.

[lshobie]

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"

[dazzler66]

Interesting, you live and learn. Wonder what makes the exhaust gases run cooler ??

[lshobie]

Not sure, a big thing around here is ceramic coating of diesel turbo housings, manifolds etc, improves mileage and lowers egts.

[beast2h]

turbulance from the rough edges probley makes the heat!

[bmatthewtaylor]

Anyone got estimates of prices to do some of this work? I'm guessing it wont be cheap. As a general rule bangs/$ tends to decrease the more you spend.

porting/polishing sounds like a good way to pass a few cold winters nights tho. :)

[dhc4ever]

Interesting, you live and learn. Wonder what makes the exhaust gases run cooler ??

I'd guess the simple fact that more air is getting into the cylinder and as the fuel is a preset amount injected after the valves are closed its running leaner, which in a diesel means cooler.

You live and learn indeed.
It would be interesting to put a STD diesel head on a flow bench and see what flow it has and then just clean up the manifold joins, dedag and polish and see what improvements that would make.

Any one know what it costs to get a petrol head flowed?