Ohh, you are not having a good time this summer.

<img src="/forums/images/graemlins/lol.gif" alt="" /> Nope <img src="/forums/images/graemlins/lol.gif" alt="" /> But I'm learning a lot of 6G72 secrets - particularly wrt parts selection - even if the hard way.

I'm still leaning toward a failed oil pump relief valve, but trying to eliminate any other things that could have contributed - such as:

1) Originally, I ran the CCV hose from the passenger side valve cover to forward of the throttle valve as with the OE setup. This caused some oil vapor ingestion at the intake (I assume due to blower ring bypass sump pressure), so this time I installed a can-type semi-clear plastic fuel filter to the CCV hose and left the other end open to atmosphere temporarily until I could figure out what to do for filtration..... the filter shows no oil and passes air freely in either direction.

2) On the initial drive, I forgot to hook up the blower bypass valve which starves the engine for air under high rpms.

I'm wondering if somehow one or the other created a sump vacuum that would air lock the pump. I don't think either would, but strange things sometimes happen.

Frank

Nope can not be an issue. The higher the vacuum you can pull on the sump the better.
You are working with a positive displacement pump that is drawing from the same reservoir as it is pumping back into.
The vacuum helps with ring seal and reduces what the pistons need to pump in the bottom end.
I would say a stuck relief valve and I am glad you look up in there. I guess you did say the sump was full of metal so you had to look.

Yes, that's my belief as well - just trying to sort through all the possibilities.



Yep - the first thing I saw when I pulled the pan was a clump of oil - stuck my finger in it and found large metal particles...... and as you know, I couldn't stop until I found the source.... wasn't too hard to find.

I haven't looked at a rod bearing - no need - it'll have to come out to repolish the crank if it's salvageable.... looks pretty bad from underneath in poor light. I just hope the cam bores and cams are ok.... cylinders and rings should be fine, but I'll see soon enough.

Next time's the charm..... I've now installed all the goodies I can find and there are no more variables to try. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Frank

David Reher doesn't agree with us:



Article from National Dragster

I can see that positive sump pressure helps the oil pickup and less than atmospheric pressure would fight it - but maybe the combination of sump vacuum and the dry oil cooler was an issue. I don't like the fact that there's no anti-drainback valve in the OE oil cooler.

Frank

I think Mr. Reher is not considering all the variables. As Charlie says, the pump is sucking from the same reservoir it's pumping to. The oil is being sucked from the mains/rods/cam bearings by the same "vacuum" as the pump pickup sees. PCV valve will mod this some, but a GOOD manifold vac is under 20", and only applied at idle, when the lube requirements are at minimum. I think you'd have to have one heck of a vac on the sump to pull a vacuum bubble in the pickup, and I LIKE a good ring seal...

Above 5-7" of vacuum your crank seals leak vacuum on both the damper and the output side... That makes it hard to get to the vacuum needed to cavitate the pump.

The suction side of the pump can cavitate, but I dont think thats what happened.

That looks like some serion starvation, most likely the crank is toasted and has heat dammage.

The block may not look very happy either if it looks like the saddle.

Kevin

Kevin -

From underneath, the block looks ok in the bores - nice and shiny.... but I haven't yet seen the area around the main bores... you may be right.

We're having construction delays getting the local yard open, but I should start buying cars within 30 days. I may just grab another SOHC Diamante block and DOHC crankshaft once something comes into the yard. I get the parts so cheap, it almost makes sense to start fresh.

Frank

I agree, Frank. I sure miss working at the yard & all the parts.

Ed

I finally found enough interest to pull the engine, and I found the ugly mess I was expecting:

1) Crank's ruined
2) Girdle's ruined
3) Rods are ruined - too much heat at both ends
4) One piston apparently seized at some point, so the whole custom set is shot.
4) One cylinder wall scored from piston seizure and...
5) The block is worthless anyway since the girdle is no good.

I haven't yet torn down the heads, but I suspect the cams and heads may be gone since they would have been oil starved as well.

The water pump, timing belt, tensioner, flex plate, valve covers, engine mounts, balancer and manifolds should be ok. <img src="/forums/images/graemlins/lol.gif" alt="" />

I've been waiting for another Diamante SOHC block, thinking I would put the rods/pistons into it, but I haven't yet found one nearby and I now see there's not much to salvage from the last engine.

Also, after promising reimbursement for the last rebuild necessitated by blower failure, no check has been forthcoming from Magnacharger despite 3 months of "reminder" phone calls and further promises. My last call to the "promisor" was on Friday and I gave him 2 weeks to make good on his promise. If there's no satisfaction by then, I suppose I'll escalate the issue and post the results here.

Meanwhile, I'm tired of seeing the truck on the perch and want to put it back on the road. I still have the original Montero block w/pistons, rods and crank that I rebuilt. It has about 7,000 miles on it and has been sitting on a stand since I yanked it when it blew a head gasket from detonation when I was trying to use the rising rate regulator and OE ECU. I think I'll put that engine in it and see if it'll stand up to the blower now that I can control fuel and spark more safely. The only real issue is the cast pistons, but they "should" hold 7 psi OK. Also, the deck could use a light milling, but I don't think it contributed to the blown gasket - more likely the cause was detonation.... so in order to keep from disassembling the block, I'll hope the ARP head studs will provide a good enough seal with the OE composition gasket and keep my fingers crossed.

Anyway, that should buy some time to find another block and build another "better" <img src="/forums/images/graemlins/wink.gif" alt="" /> engine.

Frank