Low miles heads found on CL

[tanman_2006]

I found a set of heads on local Craigs List with 28K on them! They are off of a 93 Chevy 6.5 TD.

I know some heads have different precups and what not so what precups are good for performance oriented engines?

IIRC diamond is a good precup any others?

I am getting parts around to potentialy over haul my 95 with some 18:1 slugs. An extra set of heads never hurts anyways.

[Robyn]

The DIAMOND cups are the last word in development as far as I know.

The size of the port is as large as they come with the diamond cup.

Another good cup to use is the "T" cup. These have a large T on them. The port size is nearly the same as the diamond cups.

Looking at the entire picture though there are many subtle differences in these two cups.

The inside contours apear the same but actually are slightly different.

The "T" Cups were used in the 92-93 6.5 TD engines and are a great cup to use if you can find them.

I too found a used set of heads back last summer when I was rebuilding my 95 3500 Dually.

The heads had been worked on but the whole story was as usual Vague at best.

Right off I spotted the fact that each head had a different marking on the cups.

These all need to match for things to work well.

The LARGE port cups lend themselves to more power and the ones with tiny little ports are great for mileage.

The T cups should be a great cup for power and will likely show little "seat of the pants" difference from the diamond cups.

Just make sure that whatever you use that they seat in properly and are from flush with the deck to no more than about .002" above the deck.

Do not use a cup that seats below the head surface. *****

DONT surface the heads with the cups in the head.

The cups don't fit all that tight and could dislodge during machining and become a missile !!


Have fun and good luck with your new heads.


Robyn

[tanman_2006]

Thanks Robyn, that was basically the advise I was looking for. The guy bought a crate engine a few years back for his travel trailer tow rig and the broke the crank, his loss sounds like my gain! Hoping there is little warping and no cracks.

[phantom309]

would a N/A van engine have small or large pre cups? would it be different than a turbo motor?

nick

[tanman_2006]

I would imagine they would be smaller. NA engines dont get as much air, it wouldnt need as much fuel.

[tanman_2006]

Ok, I got a chance to check out the heads today. One side has square precups and the other is diamond.

He said that he broke the crank shaft after 30K miles, I told him 2 different precups COULD cause a problem like that.

He bought the engine as a rebuild from a shop called Turbo Diesel in Oklahoma City. The heads were supposedly new not remans. The precups are flush with the rest of the head. I'm going to gueas he got screwed over on the deal. The prcups looked new and it looks like they were out during machining.

Other wise crack free heads

[tanman_2006]

Anyone know the difference between square and diamond precups? Is it hard to change out precups/how much will ne precups cost if i got the heads?

[tanman_2006]

Anyone, know what the difference is?