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

[o_man_ra23]

Situation, 1991 Cressida MX83 Grande, ran low on water due to water pump leak, boiled and blew the head gasket from the water jacket into the no. 3 combustion chamber.

Now, I do know that Toyota had lower than they should have head bolt torques on 7Ms, which causes BHG in 7M-GTEs. I am thinking this may have saved the head by making the gasket a weak point. I have been quoted good prices on the machine work if its just a matter of re-facing, but if the head has bent badly due to the heat, then its gonna cost a mint to repair.

My query is, who here has done this (or similar) on a 7M-GE (or close enough to), and what was the damage done?? Did you head get bent, or was it just a head gasket blowing?? What is the likelyhood this overheating issue has actually caused major warpage on the head??

All will be found out soon enough when the head goes into the machine shop, but I would like to know the chances of getting out of this reasonably inexpensively. Also, the best price I have gotten so far on a VRS kit is $230 for a dura-pro brand, or $242 for ACL MonoTorque... does this seem a reasonable price?? and has anyone had experience with dura-pro branded gaskets??

Help is appreciated.

Cheers, Owen

[sillycar chick]

Do they have alloy heads or steel? I cant speak from personal experience, ive never had a 7M, but warped heads one any engine are more a matter of individual cases. The only way to know for sure is to take the head off and get it checked (or you can do this at home with a straight edge if you know what to look for). If its very slightly warped but its not too bad, they can skim it and it should be fine, but if its bad they can sometimes reheat it and "un-warp it", but it would probably be cheaper to find another head in most cases and start again. Im a bit sceptical about unwarping a head anyway.

You probably knew all of that anyway hopefully the head isnt too warped and you can get away with a less costly option. God knows you need the money for your '28 project

RAd28 has 2 x 7MGEs for sale, talk to him if you need another head. Good luck Owen!

Edit: Just remembered, my aunty had a 5M in a cressi a while ago and cooked it, dad just offered to get another engine from the wreckers and replace it as he didnt even want to go near the engine she cooked - it was knocking pretty bad. Yours wasnt knocking i take it?

[Screamn_Sleeka]

Do they have alloy heads or steel?

lol.

The only way to know for sure is to have it examined at an engine machine shop.
It probably cheaper just to assume the worst and buy a reco'ed head.

[sillycar chick]

Whoops you know i meant cast iron I think they are alloy though...

[o_man_ra23]

Alloy head, and will definitely be getting a machinist's examination (unless it is obviously farked). I have spoken to RAd28 about his 7Ms already. Engine wasnt knocking, but did flood #3, so may be worth going to the trouble of replacement engine... although I dont have the required lifting equipment.

Cheers, Owen

[sillycar chick]

Hmmm you will need to improvise for some lifting equipment You is an ingineer, surely you could figure something out?

[o_man_ra23]

yeah... fix the head No lifting equipment required then.

Cheers, Owen

[sillycar chick]

See? I told ya you could figure something out!

[schnitzel]

Think you know the answer already, cant tell until you get the head off. Water in #3 shouldn't be a problem as long as the bore stays free of rust. Odds of warped head on these are 50/50 same as most alloy heads. At minimum will need a skim and probably worth checking the valves. Have seen plenty of warped and or cracked heads successfully repaired, also seen plenty that didn't work.

Time to get the tools out and take the head off and check it. Is the only way you'll find out if it is salvageable, and you just know that you want to spend all weekend fixing a car.

[Spectre]

I had a blown head gasket on my 18RGEU. I took the head off and found that it looked like the gasket had blown around the second and third cylinders.

I took the head to a cylinder head shop, where they cleaned the whole thing up, checked for warping or cracking. After it was found that it was ok, they gave the head surface a light skim, and did a full head service (tapets etc).

This cost me $220 and the head looks like new!

I'm putting it back together this weekend.

[o_man_ra23]

After it was found that it was ok, they gave the head surface a light skim, and did a full head service (tapets etc).

How the hell did you shoehorn tappets into an 18RG?? 18RGs are Directly actuated bucket over shim type systems, they have: cam -> bucket -> Shim -> Valve... so do you mean the set the shim thicknesses for you??

Anyways, what I was looking for is people who have had this type of blowout (pressurised water system) to let me know what they were up for. I know there is a chance its farked, and a chance its all good, and I need to get it checked out to find out... but I just want to know what my odds are?? How lucky do I need to feel??

Cheers, Owen

[haison]

Another possibility is if the car had been driven for a long time with a bhg the back of the block/head may be corroded out. I've seen a fair few of em do that.
Once again, dunno till you get the head off.

[brett_celicacoupe]

what id do:

pull the head off and leave both the manifolds on. inspect the headgasket and see if you can identify breach. it would be a 90% chance the headgasket has let go, not the actual alloy head. then get a big metal ruler and some feeler guages and measure the warpage. the maximum allowable warpage should be able to be found on the supra mkIII TSRM (cygnus.net). if it needs a machine, take the manifolds off and have it machined (less then a $50 job). if you have to take the manifolds off then buy a topend gasket set. get some injector o rings while your there.

put the engine back together and tighten the bolts to the higher torque (75 pf?) put it all back together, check the timing and turn the key

Another possibility is if the car had been driven for a long time with a bhg the back of the block/head may be corroded out. I've seen a fair few of em do that.
Once again, dunno till you get the head off.

the motor was mint and rebuilt not that long ago.

[o_man_ra23]

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

[brett_celicacoupe]

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.

faaaark that.

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