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6.2 & 6.5 cylinder heads

3500GMC

3500GMC

What T F, over
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I've read through the tech library for this stuff, found very little.

Cylinder head talk. Flow, pre cups, casting numbers, porting etc... Doubt that anybody has bolted the variations of these heads to a real flow bench, but you never know..

We know all the different precups in the N/A and turbo engines. But what about the actual head casting? There are a few aftermarket heads out there that have been put to work with good success. How about GM castings?

A question to get things started, how does a 90-92 J code 6.2 head compare with a '93 turbo 6.5 'F' head? Pre cups are different but what about the casting?

Intake manifold bolting surface angles? Center mount turbo? Van heads? On and on.
 
I can post up the intake/exhaust/prechamber/cylinder head cc's, won't be until the weekend, I'm kind of sick.

I am getting stock heads bench flowed, then ported and polished (along with other mods) but not until I get a steady source of income.

I still have to cut one of my cylinder heads in half, but again that is all on the back-burner right now. If someone else wants to do and post up the results that would be great (saves me the money).
 
Drink some Nyquil and get to work...:D

That would be some good info to have up here.

I have a local machine shop with a pair of the 90-92 J code 6.2 heads. I will get the casting numbers and take photos. They are machined and ready to go with Felpro bolts and gaskets. My have to adopt them.
 
One nice thing about the 6.2 heads were larger valves. But was the injector angle different?

Are you putting those heads on a 6.5? I wondered if that was possible or desirable?

I thought the 6.5 heads would flow better for the turbo, but who knows.
 
You are kind of reading my mind. We know the 6.2/6.5 ports and valve sizes are nothing but 'holes that air goes through' as far as comparing them with the very WORST of race heads. From a CFM standpoint, bigger valves from the 6.2 can't hurt... And if you can *massage* the ports, blend the bowls, increase the short side radius, port match, polish, then unshroud the valves, piston side... On and on...

The scary part would be the bigger valves are closer together. Cooling that spot would be a challenge. Maybe that's why GM opted to downsize the valves on the turbo 6.5..

Taking the time to get the ports/heads flowing is FREE horsepower. :thumbsup:

Injector wise, the angles, I do not know yet. The injector lines can bend to fit I think, that is if they are in fact different...
 
I do not remember what the difference was but when I swapped the 6.2 for the year 2000 6.5 crate engine I bought new IP lines because the other lines would not work.
 
I thought I remember reading somewhere that the diff between the 2 sets was the diameter of the tubing. Not sure why that would make any diff tho.
 
Late model 6.2 heads used the same injectors as the 6.5, those would be the ones easily interchanged.
 
i was told to never bend the inj lines they have some sort of coating on the inside that could flake off and messup the injectors
 
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