85 Blazer with 6.2l diesel

#16

Despite the smallish batteries, this thing actually starts pretty well. I think I've got at least one dead plug though. There is a noticeable miss when it first starts.

#17

Al,

When you get a chance, could you look up the torque spec for the rearmost main bearing cap on the 6.2? Tightening sequence too if they recommend one. (4 bolt bearing cap.) My intermittent searching on Ebay hasn't netted me a manual yet.

This engine was apparently built with a rope RMS. When I got in there it was totally gone. Some little bits of nasty fuzz on the outside of that cap were all that I found. The internet makes this sound fairly common on 6.2 motors this age. Darn weird to me.

When I removed the oil pump I noticed a tan colored plastic sleeve where the pump drive shaft entered the pump. It appeared to have a fresh crack down the side of it so, naturally, I proceeded to mess with it.

It was very brittle and broke into a dozen pieces. What the heck was it? My best guess is that it is a retainer to keep the shaft in the oil pump if the vac pump drive is pulled from the topside. Supporting the retainer theory is that the part had a raised ring in two places on the ID which matched grooves in the pump and shaft. I'm thinking I won't miss it unless I pull the vac pump drive at some later date and loose the shaft down into the oil pan?

#18

goglio704 wrote:When you get a chance, could you look up the torque spec for the rearmost main bearing cap on the 6.2? Tightening sequence too if they recommend one. (4 bolt bearing cap.)

Figures. I'd just this week put that FSM up in the "attic".

Got it down, it's for 1983.

FSM says:

Main Brg Cap Bolts
Inner = 94-105 ft/lbs
Outer = 59-74 ft/lbs

No specific tightening sequence is mentioned. However, there is a paragraph on the RMS:

Apply a drop of sealer to bearing cap and cylinder and case groove prior to installing rope seal.
Install rear main oil seal in cylinder block and rear main cap. Seal must be firmly installed in place, in cylinder and case and bearing cap completely filling groove. End of seal must be cut clean and flush with cylinder case and bearing cap mounting surface.
Install main bearings in cylinder block and main bearing caps.
Torque all except rear main bearing cap bolts to specifications. Torque rear main cap to 10-12 in/lbs then tap end of crankshaft, first rearward then forward with lead hammer. This will line up rear main bearing and crankshaft thrust surface.
Install connecting rod bearings.
Reverse removal procedures.

Presumably, you torque up the rear main cap to proper spec. after all that.

Reading back a few pages, they have a half-page of instructions on properly installing the rope RMS, with two illustrations, utilizing a special tool of course -- which looks like a semicircle with a pole to tap, and which may even have a groove.

You really should get a FSM.

My intermittent searching on Ebay hasn't netted me a manual yet.

Funny, there were a couple of sets available when I bought this one. And, right after I bought a four-manual set for 1999 GM fullsize truck last month (for $60 shipped, to get GM PS EVO wiring diagrams and other info), an identical set sold for $17 (arrrrrrgh!).

This engine was apparently built with a rope RMS.

The 6.2l has a rope RMS through I think 1991.

When I got in there it was totally gone. Some little bits of nasty fuzz on the outside of that cap were all that I found. The internet makes this sound fairly common on 6.2 motors this age. Darn weird to me.

I'll repeat what I've said before: My '83 6.2 was not dripping at 180k miles when I sold it, and the crank had (AFAICR) never been touched. Synthetic oil for the last 78k I had it.

But others have had the rope seal fail. I have assumed it had something to do with a peculiar lubrication requirement, but I really have no idea.

When I removed the oil pump I noticed a tan colored plastic sleeve where the pump drive shaft entered the pump. It appeared to have a fresh crack down the side of it so, naturally, I proceeded to mess with it. It was very brittle and broke into a dozen pieces. What the heck was it? My best guess is that it is a retainer to keep the shaft in the oil pump if the vac pump drive is pulled from the topside. Supporting the retainer theory is that the part had a raised ring in two places on the ID which matched grooves in the pump and shaft. I'm thinking I won't miss it unless I pull the vac pump drive at some later date and loose the shaft down into the oil pan?

The FSM does not mention it at all in the Oil Pump section, nor in the Vacuum Pump chapter, but I've seen what you're describing. I believe it is an assembly aid. Yes, they get brittle and break. I would be sorely tempted to leave it out.

#19

Al,

Thanks for the attic trip and resulting info. I'll be replacing the rear main with a two piece rubber unit from Felpro, and will avoid the rope seal entirely. I've tried to fish those darn things in before.

"Apply a drop of sealer to bearing cap and cylinder and case groove prior to installing rope seal." IIRC, that usually means a drop of loctite that seals the parting line between the block and cap?

I'll keep looking for a manual. There's one on Ebay now. It would be about $70 shipped. Kinda steep for a single manual.

#20

I don't know about using Loctite for sealing in that area. You might research that further.

$70 is quite a bit for one of these. Or, maybe, I just got exceptionally lucky for a change.

#21

Q for anybody who knows:

I had an '83 G30 (1T van). It had a GVW of over 8500 lbs which made it emissions-exempt in that year. It had no EGR for that reason.

When shopping for rebuilt IPs for the 6.2l, same price but different IPs are listed for "light duty" and "heavy duty" applications.

The Q is: For the 6.2l, is the difference between the "light duty" (VIN 'C') and the "heavy duty" (VIN 'J') only in the emissions calibration of the IP + EGR?

A half-hour with Google didn't reveal the answer.

#22

To me, the definitive answer to that question would come from a Stanadyne injection shop. I had read that it was only a difference in calibration, but I read a lot of things.

#23

asavage wrote:I don't know about using Loctite for sealing in that area. You might research that further.

$70 is quite a bit for one of these. Or, maybe, I just got exceptionally lucky for a change.

I found a reference in a Chilton's manual that calls for Loctite 496 for the bearing cap mating surface. As for the manual, I was wrong. It is $70 plus shipping. When I get this RMS mess fixed, I get a chance to drive this thing. If I decide to keep it, I'll bite the bullet and spend the money for a manual. Maybe they'll be cheaper then. Probably like Maxima manuals, they get progressively cheaper as I get more of them.

#24

goglio704 wrote:I found a reference in a Chilton's manual that calls for Loctite 496 for the bearing cap mating surface.

I'm not familiar with that particular number, but a cure rate that has full cure strength in forty seconds! (at 20% relative humidity, which is neverland here in the Great Pacific NorthWet) is startling.

#25

Technology: Cyanoacrylate
Chemical Type: Methyl cyanoacrylate

That explains it: cyanoacrylate is "super glue".

Application: Bonding
Key Substrates: Metals, Rubbers and Plastics

LOCTITE® 496™ is a general purpose adhesive and is
particularly suited to bonding of metal substrates.

Directions for use
1. For best performance bond surfaces should be clean and
free from grease.
2. This product performs best in thin bond gaps (0.05 mm).
3. Excess adhesive can be dissolved with Loctite cleanup
solvents, nitromethane or acetone.

#26

The instructions that come with the Felpro RMS call for RTV on the bearing cap. RTV is kinda thick for that application to my way of thinking. I guess if used very sparingly...

#27

RTV should almost always be used sparingly. It is commonly overused.

The nice thing about RTV is that it remains flexible, yet watertight.

#28

I finally finished the rear main seal project this evening. Looks to be a success, and I'm glad to have it done. For about the first six weeks after I took the pan off, it rained every weekend and the project got pushed to the back burner since it was outside.

The little bit of pressure washing I got to do before starting the project was not nearly enough. I would have done more, but the leak was so bad I didn't want to drive it to the carwash. Suffice it to say it was a really nasty project. If you told me there was 50 gallons of oil coating the underside of that truck, I wouldn't argue. Now that it can be driven, there is a lot of pressure washing in this truck's future.

I took the time to clean, prime, and paint the oil pan while I had it off. The fresh Chevrolet orange does look good under there.

There is plenty wrong with the truck I'm sure, but there must be a few things right with it too. The batteries are too small, but it starts very well despite the low cranking speed. I've never seen a diesel so tolerant of low cranking speed.

#29

If I had to pick one thing I miss on my diesel Maximas, versus my '83 G30 6.2l, it's hot start.

When the engine is warm, I could literally TAP the key to the Start position and it would be running. It did not have to be audibly cranked, it was just TAP and boom, it was running.

The Maxima, OTOH, needs a good three-to-five revs to fire off warm or hot.

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