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What pre-cups do I have

6.5L

6.5L

Old Iron Runner
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Location
Northwest Wyoming
I bought a motor from Teds Truck a while ago. Got it in. Great motor. Packaged amazing. Some rust material inside the block but after flushing it 2-3 times it cleared up just fine. The block itself is a 506 block. Apparentley made by International. I was just wondering what style pre-cups this motor has, if anybody knows that off the top of their head.
 
I wouldnt port them. I am not gonna take the heads off just to port the pre-cups. I am happy with with mine.
 
As I have gone through some military engines...
I would pull the heads, re-ring the engine standard size, and glaze break the cylinders. Also use ARP head studs for the heads. This will cut your blowby to new engine levels of near none. I find these engines sit so long that you get rust in some of the cylinders that can remove the crosshatch. They will run fine without the above, but for top performance freshen it up a little. Rings are cheap unless you go gapless and those are in a class of their own for clean crankcase oil.
 
WarWagon said:
As I have gone through some military engines...
I would pull the heads, re-ring the engine standard size, and glaze break the cylinders. Also use ARP head studs for the heads. This will cut your blowby to new engine levels of near none. I find these engines sit so long that you get rust in some of the cylinders that can remove the crosshatch. They will run fine without the above, but for top performance freshen it up a little. Rings are cheap unless you go gapless and those are in a class of their own for clean crankcase oil.
Click to expand...

These Navistar 506 long blocks have very little run time. My engine has very little blowby and there was no rust whatsoever in the cylinders.

Also, my motor did not have diamond precups. It had square precups. I replaced them with a set of T precups and have been very happy with the performance.

SquarePrecup2.jpg
 
Hmmm, so now people are saying I have Square cups. and I would have love to tear the block apart to check everything but by the tme I got all the parts I needed and everything I had very little time to get it in before I left for college. I just needed a running vehicle. and the motor runs real strong so I can't be unhappy about it.
 
You might have diamonds. I'm just saying that just because you have a navistar casting doesn't mean you have diamond precups.
 
If it was a Military surplus, they are probably square. The NA engines had square precups and the oil squirters are blocked off, except for 7 & 8. If it was a turbo, then it probably has the diamond precups. If you can pull the oil pan, see if its a standard or high capacity oil pump. If standard, it was probably an NA, high capacity probably turbo. Another tip off me be if it has a shield over the upper timing chain, then probably a NA engine. I wouldn't say any of these will tell you 100% what precups you have, but short of a teardown, probably as close as you can get. One other thing to keep in mind, on the NA engine I had the pistons did not appear to be anodized. Not sure if that makes any real difference, but the replacement pistons were anodized on the piston heads. I guess what I'm saying, if it was an NA, I wouldn't use high boost pressure without the oil squirters and with NA pistons.
 
How did I know if it was a high flow oil pump or not? I know that when we were swapping things over, that we had to change the oil pickup tube or whatever it was because it was a different style. Are they all like that with the military surplus engine becasue of the different style oil pan or what?
 
This is the standard oil pump
GEPOilPump1.jpg

The hi flow one has a spacer between the cover and body, as it has longer gears.
You probably had a pickup like this one because the Hummer uses a different oil pan.
The truck oil pan requires a different oil pickup.
 
so now I am confused,I have square pre cups and had high flow oil pump?? it definately had a spacer between the pump and pick up with a long set of Gears...HHHMMMM????
 
I seriously wish there was just an easy way to tell, like a stamp on a head or something that said weather it was a N/A or Turbo with whatever pre-cups. Would save some of us the hassle or confusion haha
 
Big Bertha said:
so now I am confused,I have square pre cups and had high flow oil pump?? it definately had a spacer between the pump and pick up with a long set of Gears...HHHMMMM????
Click to expand...

First let me say I'm just going by what I found on my Military surplus GEP engine and talking to others that should know (Peninsular, Diesel Depot, and a rebuilder for the Military). But, I'm not saying its 100% that if you have a standard oil pump you will have square precups. First, lots of these got rebuilt. While most got done to a certain spec, its possible some were ordered to a different specification. Its also possible someone changed it at a later date. I would also guess that if the rebuilders was out of a certain part, they substituted something else. Say maybe the standard oil pumps were back ordered, maybe some got built with hi flow pumps. From what I have been able to determine, the usual NA spec is: Oil squirters on 7 & 8 only, standard oil pump, non anodized pistons and heads with square precups. However, the Military may change spec from time to time, so who really knows?

More speculation here, but the reason Military Surplus engines are usually NA engines is because the turbos are destined for Hummers and they have center turbos. Center turbos use different heads, so those engines won't work with side turbo manifolds. The NA's use regular heads, so are a direct fit for our trucks. When I talked to the rebuilder for the Military, he referred to them as "turbo" and "NA". To him, a turbo is a center turbo and the NA uses standard heads. When I ordered a set of heads from them, they had to special order them. He said they don't use that style of head (side turbo with diamond precups). So from that I guessed on all the engines they rebuild, the turbos are all center mount. I don't think they did side mount turbo engines. He did tell me on most of the engines that came in the block was reused, but virtually all got new heads. He indicated the cost to rework the heads was about what they could get new for, so it was easier to install new heads.
 
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