The guys at the college are going to rebuild my 6.2 injectors. They're popping about 500 lbs low. I'm told they are supposed to go at 2000. Can stock injectors be rebuilt to high-pop specs? Where do high-pops open at? Can these low injection pressures cause a knock?

Stock pressure for a 6.2 is about 1800+-. I would advise against raising the pop off pressure because it puts more strain on the injection pump. If your pump is a little weak you will be creating problems.

If you have these volunteers willing to do work for you, I would have them pull the cylinder head on the side where your knock is and find the problem.

Can a head be pulled without pulling the engine? Will a low injector pressure cause a knock if the fuel isn't atomizing well enough?

Yes, a head can be pulled from a pickup truck without pulling the engine. It is easier to remove the head with the engine out, but removing the engine results in a lot more work!!! The head is heavy so just be careful.

Got a call on a used engine with 20K. Guy wants 600 for it. Might go ahead and do that.

not a bad idea ww then you can check out the knock and have a spare or just get nuts and build a monster outta the old one :)

I will play devil's advocate. How do you know it only has 20,000 miles? Can the engine be started for you? If the glow plugs are bad, I would remove them all before committing to be sure you can get them out, or you might be pulling a head anyway. I would preffer a compression test to know the engine is sound or to hear it run. Your other engine is also an 82, right. 82 is the only year (red engine) that used coarse threaded injectors. The heads also had some issues with external water leakage due to a casting hole that was changed in 84. 82's did seem to have a high nickle content in the block and I have seen many of them last a very long time. Low miles doesn't always mean great deal however. I would look it over very closely. Check coolant passages for rust, condition of oil etc. Good luck.:lol:

All GM injectors use a Zero degree spray angle. The pattern does not change with pressure increases. The Zero angle means it sprays straight out from the nozzle whereas some spray out at a slight angle, like an inverted cone. The naturally aspirated engines pop at 126bar./1827 PSI. The turbo injectors pop at 142bar/2060 PSI. The pressure is adjusted by adding or subtracting shims. A shim thickness of about 0.002" equals ~100 PSI.

Early 6.2's O SD248 nozzle 126 bar.

Short Body 6.2's OSD253 nozzle 126bar.

All 6.5's OSD304 nozzle 126bar. (turbo popped at 142 bar)

Higher pressure does not equate to more fuel. Actually put out less at much higher pressures.

Is 82 the only year that's painted red? I was told different. My suburban's an 82 but it had a new GM Goodwrench put in it sometime in the late 90's. Need to buy a shim kit so I can get the injectors rebuilt. What is one worth? Where should I get it from? Not sure what year the used engine I found is. I just know it's red. 20K miles sounded a little funny to me too. That's under 1000 miles/year. It did originaly come out of a wreck. If I'm lukey it might be a hell of a find. The question is will the injectors out of the GM Goodwrench that are being rebuilt fit in the engine that I might buy?

I would have those injectors rebuilt to specification, not the higher PSI you were quoting or your injection pump will be failing next. I would be very skeptical of the guy that has an engine with "only 20K" miles on it. A true 20K engine would be worth a lot more unless it has some major problem and then I would not be buying it. The heads, injection pump, and injectors (as a group) are worth more than $600 if they are good and they should be with 20K miles. Once you put down your $600 then it is yours!!!!!

All '82 and some early production '83's were red. The early engines were good for a lot of miles when properly maintained. The problems were no greater than the later engines including some of the 6.5's. Follow Camerelli's advice and check it out before you buy it. It will be worth your time.

Sorry that I mixed up your posts. I was replying to your engine post, but I did it on your injector post. If your sub has a late model engine it will have fine thread injectors. Depending on how late model the gm goodwrench engine is it could also have some other minor differences. Most of the changes are in the heads, with the exception of 6.2's built after 92 were based on 6.5 blocks and under bored, and have a one piece rear main seal. If the engine you are looking at is red it is probably an 82 model engine. I have owned 6, 83 models and they were all black engines and every 82 that I have bought or worked on was red. Biggest difference it the injector threads and style of nozzle. To be sure, pull an injector off of the red motor. The blocks are totally interchangeable. Check to see if the injection pump has been rebuilt. Usually the rebuilts have some pink or red fingernail polish on one of the top pump screws. Early pumps had short lifespans due to sub par internals.

The red engines had the short-thread head bolts as well. Not a big issue, just that the later engines had the "new and improved" bolts. Some '82's suffered head gasket failure due to the bolt stretch. The later style bolts were the recommended replacement, along with the angle-torque method of tightening. This was on an early TSB on the 6.2's.

Looked at engine. Lookes good. Need to get bolt for starter so I can hear it run.