7M-GE BHG, how bad can it be?? (calling on experiences)

[o_man_ra23]

That writeup is pretty good supra cam. Well worth the read.

All the experiences shared are being taken on board. Will see what the result is when the head is off and the straightedge is applied.

Cheers, Owen

[amichie]

How much was the head you bought??

$200 from leader spares in tempe. I think they have moved now to Marrickville.

Head was a very low kms unit with very tight original valve guides and the usual wear on cam bearings.

[o_man_ra23]

Righto, well the head is off and the damage is evident. I think the head is a writeoff... there is over .2mm warpage, but there is also deep grooving around the combustion chambers where the head gasket has been. Dont think this is from o-ringing, as its not neat enough.

Cause of the problem was the waterpump was fooked. It was leaking from the telltale... but looked like the gasket was gone. (tried to convince the owner to come around and get the water pump fixed, but he got slack)

Also there is evidence of cross chamber leakage between no. 1 and 2.

So, replace head, VRS kit, and new water pump, and we should be in business. Will post up pics tomorrow.

Cheers, Owen

[3sgte]

Just as The Real Roadrunner said, Check the block!

If the deck of the block is eroded, you need to resurface the block.
The grooves in the block deck surface are from the fire ring of the headgasket (which was loose toward the end of the failure) vibrating and moving every time the engine fired.

If you do not resurface the block you are basically doing a band-aid (temporary) job. I worked at the dealer back when they were in warranty, and I had the honor of doing a few of these... (I don't miss them)

Earliest failure at my dealership was at 12,000 kms.
The typical warranty repair was to deck the block (resurface it) and replace the head (when the deck surface was eroded). Funny thing was that the deck of the block always seemed to have more wear than the soft aluminum head. We wouldn't machine both, as we were concerned about bumping the compression ratio up too high (especially on turbos).

[amichie]

Just as The Real Roadrunner said, Check the block!

If the deck of the block is eroded, you need to resurface the block.
The grooves in the block deck surface are from the fire ring of the headgasket (which was loose toward the end of the failure) vibrating and moving every time the engine fired.

If you do not resurface the block you are basically doing a band-aid (temporary) job. I worked at the dealer back when they were in warranty, and I had the honor of doing a few of these... (I don't miss them)

Earliest failure at my dealership was at 12,000 kms.
The typical warranty repair was to deck the block (resurface it) and replace the head (when the deck surface was eroded). Funny thing was that the deck of the block always seemed to have more wear than the soft aluminum head. We wouldn't machine both, as we were concerned about bumping the compression ratio up too high (especially on turbos).

2 Questions.

1. What did you torque the head when you put it back together.
2. Did any of the BHG repairs come back?

[o_man_ra23]

The block wasnt eroded at all. Just the head. Checked the deck of the block, only my .037mm feeler guage would fit under the straightedge. The .076 didnt even come close to squeezing under, so I think the block is safe.

Cheers, Owen

[3sgte]

2 Questions.

1. What did you torque the head when you put it back together.
2. Did any of the BHG repairs come back?

Generally, we did the work in an equivalent to factory manner (exception of using one MHG), so I am sure that they all eventually failed again. None of them came back <i>quicker</i> than the first time,,,

The one that failed at 12k made it to 72k before failing again. I didn't work on that car though.

We basically torqued the headgaskets to spec., this was relatively early, there was no internet with a consensus citing a higher torque spec. I don't think any of us were brave enough to go all the way to 70 ft-lbs.
One thing is certain, none of the bolts were ever left on the loose side of spec!

We even did one customer pay job using a metal HG and resurfaced head and block. The block was terribly eroded on that one, the main concern was maintaining the factory C/R and avoiding a repeat failure. That was toward the end however...

It has probably been around 8 or 10 years since I had the honor of doing one...

[3sgte]

The block wasnt eroded at all. Just the head. Checked the deck of the block, only my .037mm feeler guage would fit under the straightedge. The .076 didnt even come close to squeezing under, so I think the block is safe.

Cheers, Owen

The deep grooving you described in an earlier post is the erosion that I was referring to.

Can you post a pic?

[o_man_ra23]

Yeah, will post later, dunno how the pic came out, was done with the phone after dark.

Cheers, Owen

[o_man_ra23]

Theres the damage.

Cheers, Owen

[EldarO]

macro function would've been nice

looks nicely f00ked.

unlucky, teh 7M continues phucking people over.

but when they work they're 'ken awesome!

Elmo.

[o_man_ra23]

Using a camera would have been nice too... was done with phone Next time I head up there, I will take a photo or 2 with a real camera.

Cheers, Owen

[3sgte]

If possible, grab a couple of shots of the block as well.

[88SupraGT]

That's still good, what are ya talkin' about! Have you found another yet?