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

[o_man_ra23]

Id take all those parts over 2 BHGs

Cheers, Owen

[MZ20_drifter]

faaaark that.

24valves, 24 buckets, 24 shims, 48 collets, 2 cams, 14 cam bearing caps..... thats a shit load of parts

= busy person

[crowncustom]

I was thinking get it skimmed and VRS for the sake of it... best not to try your luck on these things. Plus I have a set of valve lappers and lapping paste, so not a hard job to give the seats a quick touch up.

Haison, Brett is right, this thing had a BHG for about 20 secs (or less) before it stalled... it filled up with water pretty quick, wasnt a slow leak.

Anyone whos blown a gasket like this want to confirm Bretts theory and my hope that its most likely just blown a hole in the gasket and not warped the thing??

Cheers, Owen

By the sounds of it,its just blown a hole in the HG.I had an XF Falcon yrs ago(no flaming plz )that blew a HG and I thought the worst like you have but I just went out and bought just a HG and was lucky when the head was pulled there was no probs with the head at all.
So you may be lucky just to get away with a HG and nothing else.
Cheers Brett.

[o_man_ra23]

heres hopin, must hold my tongue to the left I guess.

Cheers, Owen

[88SupraGT]

Max warpage for a 7M head is 0.10mm. I had a blown head gasket on my 7M-GTE and I drove it for about 5 minutes after, I got home but the head was severely warped. Don't know if 20 seconds driving will do any damage, but good luck to you!

[EldarO]

mine was freshly rebuilt, blew after 8000k's.

drove it around for ages with it blown, slowly got worse and worse, until i couldnt drive down the road till it overheated.

pulled it off, and it was dead flat.

so i guess it depends on the condition it was in when it was put on.

head shop should be able to tell you what condition its in within a few secs, they've got various straight edges that they use...

oh, and one last thing.

if your only replacing the head gasket, and getting the head machined flat.

DONT TAKE THE CAMS OUT(speaking from GTE experience).

Elmo.

[AeRoKaBn]

mine was freshly rebuilt, blew after 8000k's.

drove it around for ages with it blown, slowly got worse and worse, until i couldnt drive down the road till it overheated.

pulled it off, and it was dead flat.

so i guess it depends on the condition it was in when it was put on.

head shop should be able to tell you what condition its in within a few secs, they've got various straight edges that they use...

oh, and one last thing.

if your only replacing the head gasket, and getting the head machined flat.

DONT TAKE THE CAMS OUT(speaking from GTE experience).

Elmo.

when i blew my 7m the head warped quite a fair bit and i was told my cams needed to be removed and reset.

Apparently (makes sense) when ur head warps it puts strain on the cams and especially the cam bearings causing them to wear out quite quickly

[EldarO]

im talking in my experience, which ive outlined to be the head not being warped..

should've made it a bit clearer though, my bad, dont take the cams out unless you have to

ive seen a few people take their cams out, then gone in, having their head checked out nice and flat, only to have it resurfaced very slightly, and have to put it all back together again.

dont make work for yourself

Elmo.

[AeRoKaBn]

yeah for sure... no use taking them out if u dont need to

[amichie]

I removed my head after a blown head gasket and found that there was so much corrosion that the head was not worth fixing.

Bought a head off an inport engine. Pulled it apart, lapped all valves by hand, had the head skimmed/faced for $65 and put it back together. Reset valve clearances using a handy bucket of shims. Put it back together using an ACL VRS kit for $200. Paid another $200 for an ARP head stud kit and never had a problem since.

Things to watch out for.
1. If the head has been machined a few times measure the depth of the dowel pin holes and then measure the height of the pins in the block. Mine needded to be filed down about 3mm.
2. Watch out for pitting on the block. It can be cleaned up and filled up with some of that epoxy metal filler and then sanded back for a good finish.
3. Only use a full metal head gasket if you intend to have the block properly prepared.
4. Get your radiator cleaned out profressionally for about $100 its worth it.
5.Check for leaking welsh plugs. Any sign of corrosion or leaking coolant then change them. They are not that hard to change while the head is off.

[o_man_ra23]

Thanks for the input from those with experiences.

Will check the welch plugs, but pretty sure they have been recently changed. Already know about copper head gasket pitfalls... but good to remind people. How much was the head you bought??

Will most likely be pulling the head off next weekend, so will let all know what it looks like.

Cheers, Owen

[The Real Roadrunner]

i have seen a 7m block that was sagged in the guts by 45thou not good so check block face with a straight edge.
if you have a head that needs to be machined and has already been done before its a good idea to pul the cams and check the tunnels are straight as the more times you deck the head the more the tunnels could be misaligned and it will chew cams.

just some more food for thought

[Bowlsclubboy]

Just finished the BHG repair on my gfs MA70. It had gotten that hot on the street that the engine started to labour and just about sieze while it was running. It had also done a full lap of winton with no water at all after that stupid hose under the thermostat housing blew. Poor thing, I took the head in to have it done and he threw the straight edge on it and it looked to be warped (i shit you not) about 1.5mm - .060"

Should have had the block done as the head had twisted to the side and the fire rings had left impressions in the block and head on one side only. Couldnt visibly find where the leak was in the head, although one of the pistons, number 3 i think was spotless while all the others had carbon. Could still see home marks in the bores which makes me think it has been rebuilt somewhere in teh 160,000km.
Are 7mgte pistons factory fly cut? Cuz these are.

Cost $117 landed for a full gasket kit from ebay US and the engine builder had a recently rebuilt 7mge head there from a car that developed a knock, The head was still all nice and clean so it wasnt too old. He skimmed it and i handed over $380.

Got the arsehole car fully finished today and i will never buy another 7m car. The other cressy in my driveway doesnt count cuz i already own it

[supra_cam]

Had a bhg a couple of months ago. Luckily it didn't do too much damage, had the head skimmed for $70. The person who did it reckons its been skimmed before but he was still able to take a bit more off. Wasn't sure how long the timing belt had been on so I replaced that while I was at it for peace of mind. Probably the hardest part of it was putting all the different hoses back on it got pretty confusing! Done a bit over 2000k's and so far so good. Tigtened the head bolts to about 70-75 pounds, i can't remember. The head gasket packet said 50 something which didn't seem like much.

[supra_cam]

just found this:
http://www.mkiiitech.com/forums/viewtopic.php?t=15