6.2 turbo heads?

[Project G3]

I'm building a turbo 6.2 for My 86 K2500 and need advice on what heads to use. I have two sets of heads that I can have rebuilt. Should I use the smaller valve C series 14077162 heads or the large valve J J series 10137567 heads?

Thanks,
Garrett

 

[Twisted Steel Performance]

The larger if they aren't cracked..

 

[3500GMC]

Other differences could be injector angle and injector body thread pitch. It could affect fitment depending on what lines, manifolds etc you want to run.

 

[MrMarty51]

I wonder if there are threaded adapters to take the injectors from the larger thread size to the 10mm size.

 

[WarWagon]

Depending of the turbo used the 6.2 precups can choke you up. GMx turbos are so restrictive the 6.2 NA precups don't matter. More fuel and a big ATT (A Team Turbo) the small precups spin the mix above the piston so fast it centrifugally separates and can't burn. In short more fuel and big turbo makes smoke on small precups.

I am not clear if the 6.2 precups are a different size than 6.5 turbo precups. I recall reading there was a diameter difference. If so you can have the 6.2 precup opening machined larger: good luck finding a machine shop to handle the inconel they are made of.

 

[3500GMC]

On my 6.2 big valve heads the tang that locates the pre cups in the head pockets were on the opposite sides compared to my 93 6.5 heads with the T pre cups.

I kinda milled the 6.2 n/a cups to my *spec*. And felt great doing so.

 

[Project G3]

Dropped off the heads yesterday. Going with the larger valve heads and having them install diamond precups. Any other work I should have done?

 

[3500GMC]

Valve job? Check for pitting/erosion on the port side of the exhaust valves. Check for cracks between the In/Ex valves. Guides hold up pretty well but worth a check also. Strait edge the decks check for warpage. Usually they're pretty sound if they lived life on a n/a motor.

 

[WarWagon]

I would make sure the precups are installed correctly - do NOT grind the head with them installed or they will suck into the grinding wheel, leave a low spot, and blow the HG around the precup area.

This topic was covered with pictures of precup differences awhile ago on here:

http://www.thetruckstop.us/forum/threads/6-2s-or-6-5s.45549/#post-524277