Bigaaron, those pictures scare me. I can see it now, BigA with a HG keychain! (a really big keychain) I am down for a group buy of bhg keychains.
Anonymous HG Poll
- Thread starter dugums
- Start date
THANK YOU! for posting this. Having built multiple engines with metal headgaskets and having ever had a single problem due to not mirror finishing the block I would love the see the results here.
WOW.
Out of 18 responses for MHG - machine head only, I am the first and only one to report problems. How many times have I heard that you need to do both.
FWIW, my head gasket failure was most likely the result of electrolysis, which ate up to 1/4 inch of the metal around the water jacket openings away in less than a year.
Out of 18 responses for MHG - machine head only, I am the first and only one to report problems. How many times have I heard that you need to do both.
FWIW, my head gasket failure was most likely the result of electrolysis, which ate up to 1/4 inch of the metal around the water jacket openings away in less than a year.
Blackfin said:
Sorry for being so uneducated in this regard, but what conditions set up the possibility for the electrolysis?
Thanks!
The first engine I built for my own car years ago was a HKS stopper mhg, with only the head machined, and it blew in 5k miles. It made so much pressure in the cooling system that my radiator literally blew up.
bigaaron said:
Hey Bigaaron,
Do you have any clues as to what might have caused that condition?
Im asking because while Im new to the 7m, Ive built many 4ag's, and my first impression of the 7m (having only taken one apart) is that it is remarkably similar to the 4ag... only bigger and with 2 more cylinders and not being a square design. Ive blown many headgaskets in my time, but they have all been attributable to something I did... for instance not closing off the rad cap all the way after bleeding the cooling system on my mr2...
I think people tend to jump the gun on the causes fo their BHG.
It was caused by the deck surface not being flat. The only other Toyota engine I know of that was as bad at blowing headgaskets was the 3vze, which had a "service campaign", which should have been a full blown recall along with the 7M. No other engine experience can prepare you for the problems you will go through with a 7M not built correctly. I'm just trying to save people from headaches by posting my experiences.
1 vote for Copper head gasket with o-ringed block..
Dont know if I am going to have any problems yet as the motor is not in the car yet...
Dont know if I am going to have any problems yet as the motor is not in the car yet...
bigaaron said:
Well, there is a difference between no machine work, and no machine work, no prep and no prevention. I did mine with a trust metal gasket, ARP's and a nice surface on the head. I cleaned it up and prepped the surface with some 3m pads then clean clean clean. Then I thoroughly checked the block for straightness and pitting and any problems with coolant passages. Its amazing what you can prevent with something as simple as a straightedge.
Honestly, I have to wonder what it is about the 7M that makes it susceptible to a non flat block. The design is amazingly similar to the 4a, only larger, and the 4a doesnt have any of these issues when changing a head gasket. I can see it happening if the car overheats so severely that it warps the block, but seriously, that would be a severe overheating problem and would likely cause more than a non sealing hg... you know, like warped rings, etc.
for the record, Im not saying that if given the opportunity it is not better to machine the block. obviously it is a good idea.
Lets see here... I've used a composite gasket with no prep, just cleaning. 85 foot pounds of torque. Lasted until I turned the boost up to 20psi on a stock CT. Then I shattered a couple pistons and blew out the headgasket.
I've put in a used HKS gasket, with all the coatings pulled off. Machined head and block, but not to the specified RA. Sprayed the gasket with brake quiet on both sides. Held fine. This was at 90 foot pounds.
My latest is a properly machined head and block, to the specified RA, and a new Cometic gasket with the offending rivets removed. Cranked down to 85 foot pounds, no problems yet.
I've put in a used HKS gasket, with all the coatings pulled off. Machined head and block, but not to the specified RA. Sprayed the gasket with brake quiet on both sides. Held fine. This was at 90 foot pounds.
My latest is a properly machined head and block, to the specified RA, and a new Cometic gasket with the offending rivets removed. Cranked down to 85 foot pounds, no problems yet.
mine all blew due to incorrect torque AND badly made gaskets & trying to run a copper gasket without o-ringing the block, have yet to see how the mhg with all machine work & arps go hehe
dugums said:
I left a gound wire disconnected. A faulty ground and/or old coolant are the usual causes. It's not hard to test for it. See link below:
http://www.drivewerks.com/Newsletter/vol-7.htm
for statistical stats I voted Composite/head prep only/problems - I immediately blew the HG within 10 miles but I know my prep was faulty on the block. There was some bad pitting I hoped I could fill with spray copper ...and I was wrong.
Also you can add one more stat from me on my second go round.
MHG(cometic)/prepped block and head to RA spec/ARP studs to 103/no problems.
(103#'s cause thats what adjuster does, lol)
Also you can add one more stat from me on my second go round.
MHG(cometic)/prepped block and head to RA spec/ARP studs to 103/no problems.
(103#'s cause thats what adjuster does, lol)
Let's give this a little bump - I was hoping to have 150-200 responses with the way it started...
I think bigaaron had at least 87 BHG's in his pictures - c'mon, fess up - who's were they?:evil2:
I think bigaaron had at least 87 BHG's in his pictures - c'mon, fess up - who's were they?:evil2:
i got composite w/ head prep only on stock head bolts at 76 ftlbs holding 13 psi on a 57 trim fairly well, later this summer i'll go for 18 psi a few weeks before im ready to store it for winter again 
americanjebus said:i got composite w/ head prep only on stock head bolts at 76 ftlbs holding 13 psi on a 57 trim fairly well, later this summer i'll go for 18 psi a few weeks before im ready to store it for winter again
Good to know. I plan on running my 57 trim in the same range. Are you using any fuel/tuning for 13 psi? If so, what works well?
americanjebus said:i got composite w/ head prep only on stock head bolts at 76 ftlbs holding 13 psi on a 57 trim fairly well, later this summer i'll go for 18 psi a few weeks before im ready to store it for winter again
americanjebus = super intestinal fortitude
Looks like I'm heading toward a 57 trim later this summer with the same set up, except for about 80 ftlbs on ARP bolts and no way I'm going over 11-12 psi. :icon_razz
well first off, i have been through a few head gaskets my self, i learned very hard. and i would like to applogize for such a lengthy post but i feel this is the best place to tell my story
i would like to say, ij, big A, ideal supra, reign and a few other's are very wise people and usualy dont blow you off with bad information. somes times they;ll perfer you to search then just asking q's??
with that said, i'll let you know how my head gasket trails and tribulations went..
purchased jdm gte and i wanted to pull apart the motor a bit do some cleaning and inspecting, they lost my compression test info and any info about the motor during shipping. also the pan was cracked so i wanted to inspect the oil pick up & pump.
the bottom end looked very clean, and the screen had a small indent in it, which easily was pulled, and the pan was replaced.
when i pulled the head off i inspected the head gasket very carefully, and i noted that the water jackets around cylinder 6 had started to become distorted.
i assumed this was the stock head gasket, and noted it probaly had a over heating issue from air entering the coolant system.
no big deal i thought! and after reading more then my share of post's, i came to the conclusion that the head gasket was not torqued down enough from the factory, and that the head boltsd were no re-usable, i purchased arp studs. and a full gasket set from the parts retailer, it was a rock gasket set.
the gasket appeared to be oem quality.
a little about my car, i was not able to drive her till i finished my mild build, so my car never had stock exhaust, intercooler / & pipes, or ever ran on the stock afm, i had picked up the maft pro from day one. and i have never been able to turn my boost down it's ran 10 psi from day one,
i torqued the hg down to 85ft lbs, and she only lasted a month. well i ofcourse put about 1200 miles on her that month, and brought her to the drag strip a few times, i also lost the heasd gasket at the strip (13.7 @ 103)
@ this time, i choose to rebuild the head, have it surfaced for a mhg, and put in a 1.4mm titain head gasket,
i checked the block to the best of my ablity with a straight edge, and found no reason to have it machined. with all the talk about lapping the block i saught after learning how to do so, after not gather very much information i decided to clean it up the best i could and smooth out the finish using fine wet/dry sand paper, i was able to bring the block surface to a very shinny apearance.
my head was warped less then .003" and my machinest told me i did not have to have it surfaced, and it was in spec. i told him i was changine the hg style and wanted a perfect head, hence why i was having all the worn guids replaced and the valve springs checked, along with a 3 angle grind,
he agreed to do the work and bring the head to an acceptle finish for mls head gaskets, (a finish of that ford and dodge used on their bi metal engines.)
at this point i was satisfied that my preperation was good enough that i was done with head gasket problems.
1 month latter i start having over heating issues...
i tried running new thermostats, no thermostate, different types of coolant ( cheap brand vs expensive, and different store styles aswell)
i then convinced my self that i was unsuccessfull at removing all of the air out of the coolant system after the head gasket replacement & having the head rebuilt,
so i found the steepest slope in town and brought 5 gallons of mixed coolant with me, i know over kill , but i stayed their untill all the bubbles were gone.
no more then a hour latter of driving around, my temp started to raise,
driving me nuts i went to my neibor with questions, he sugested for me to do a block check, @ this point i had already flushed an refilled my radiator before going to his hous and had the car warmed back up, but not driven hard.
block check showed negitive.
in disgust and not knowing what was wrong with the car i pulled out and romped on her down my road, she started to get warm and i turned around and pulled back into my neibors house, let my car sit, then i did another block check, this time it was positive.
conclusion, 5psi or more cylinder pressures were high enough to push past the seal on the block.
upon removal of the head gasket, it was apparnt that it was sealing to the head, and NOT THE BLOCK. the ringland inbetween the cylinders were burnt, and you could see where some of the viton had been blown towards the coolant passages.
at this point i knew there was no short cut, and i must remove the crank and disasemble the motor so the deck could be properly surfaced,
i through in a 2mm titain mls hg and i have never looked back,
check this, after correctly prepping the block and head, i have been able to re-use my 2mm head gasket 3 times.
after i rebuild my motor it got rod knock, and i re-used the mhg,
after i rebuild it from rodknock i had crank work done and had the rod's resized and some more goodies added,
the motor has some noise in her still that sounded very similar to piston slap,
being i re-ringed her 3 times now, i decided it was time for a bore new pistons and what not, but i still through in the cleaned up used mhg,
the motor was rebuild a 3rd time due to the piston slap noise, and the head gasket is still in use today.
and i found my piston slap noise was a loose exhaust manifold bracket that i forgot to tighten down...........
when i built my brothers motor, he had a 2mm mhg that was installed on a machined head, and stock block, it did not appear to have any problems, but since we wanted to keep it that way and he needed a rebuild due to we bought the car knowing it had rod knock, we had the deck surfaced and we re-used his mhg and are not having any problems with either car.
both my brother's car and mine are bpu, full exhaust, maft pro, electric boost control, full rebuild, and have the oil changed when it becomes dirty darker them amber, or 3k miles witch ever comes first,
i forgot to add it in there along the way, but when i had my first block decked my machinest said he needed to remove .009" to make it flat again,
i would have never known this, even being a automotive student, i just dont have the tools nescary to take the measurents with, a feeler gauge and strait edge will work but is very hard to use while the engine is still in the car, it's hard to tell where the low or high spots are.
the warped block was replaced even after the head gasket held on it. the block had a crack running along the water jackets that didn't bother me to much, but when i needed a bore i decided it was the best time to suit for a better block.
i belive that the japense owner of my motor over heated the block enough times to crack it. but it very well could have been a casting defect.
i would like to say, ij, big A, ideal supra, reign and a few other's are very wise people and usualy dont blow you off with bad information. somes times they;ll perfer you to search then just asking q's??
with that said, i'll let you know how my head gasket trails and tribulations went..
purchased jdm gte and i wanted to pull apart the motor a bit do some cleaning and inspecting, they lost my compression test info and any info about the motor during shipping. also the pan was cracked so i wanted to inspect the oil pick up & pump.
the bottom end looked very clean, and the screen had a small indent in it, which easily was pulled, and the pan was replaced.
when i pulled the head off i inspected the head gasket very carefully, and i noted that the water jackets around cylinder 6 had started to become distorted.
i assumed this was the stock head gasket, and noted it probaly had a over heating issue from air entering the coolant system.
no big deal i thought! and after reading more then my share of post's, i came to the conclusion that the head gasket was not torqued down enough from the factory, and that the head boltsd were no re-usable, i purchased arp studs. and a full gasket set from the parts retailer, it was a rock gasket set.
the gasket appeared to be oem quality.
a little about my car, i was not able to drive her till i finished my mild build, so my car never had stock exhaust, intercooler / & pipes, or ever ran on the stock afm, i had picked up the maft pro from day one. and i have never been able to turn my boost down it's ran 10 psi from day one,
i torqued the hg down to 85ft lbs, and she only lasted a month. well i ofcourse put about 1200 miles on her that month, and brought her to the drag strip a few times, i also lost the heasd gasket at the strip (13.7 @ 103)
@ this time, i choose to rebuild the head, have it surfaced for a mhg, and put in a 1.4mm titain head gasket,
i checked the block to the best of my ablity with a straight edge, and found no reason to have it machined. with all the talk about lapping the block i saught after learning how to do so, after not gather very much information i decided to clean it up the best i could and smooth out the finish using fine wet/dry sand paper, i was able to bring the block surface to a very shinny apearance.
my head was warped less then .003" and my machinest told me i did not have to have it surfaced, and it was in spec. i told him i was changine the hg style and wanted a perfect head, hence why i was having all the worn guids replaced and the valve springs checked, along with a 3 angle grind,
he agreed to do the work and bring the head to an acceptle finish for mls head gaskets, (a finish of that ford and dodge used on their bi metal engines.)
at this point i was satisfied that my preperation was good enough that i was done with head gasket problems.
1 month latter i start having over heating issues...
i tried running new thermostats, no thermostate, different types of coolant ( cheap brand vs expensive, and different store styles aswell)
i then convinced my self that i was unsuccessfull at removing all of the air out of the coolant system after the head gasket replacement & having the head rebuilt,
so i found the steepest slope in town and brought 5 gallons of mixed coolant with me, i know over kill , but i stayed their untill all the bubbles were gone.
no more then a hour latter of driving around, my temp started to raise,
driving me nuts i went to my neibor with questions, he sugested for me to do a block check, @ this point i had already flushed an refilled my radiator before going to his hous and had the car warmed back up, but not driven hard.
block check showed negitive.
in disgust and not knowing what was wrong with the car i pulled out and romped on her down my road, she started to get warm and i turned around and pulled back into my neibors house, let my car sit, then i did another block check, this time it was positive.
conclusion, 5psi or more cylinder pressures were high enough to push past the seal on the block.
upon removal of the head gasket, it was apparnt that it was sealing to the head, and NOT THE BLOCK. the ringland inbetween the cylinders were burnt, and you could see where some of the viton had been blown towards the coolant passages.
at this point i knew there was no short cut, and i must remove the crank and disasemble the motor so the deck could be properly surfaced,
i through in a 2mm titain mls hg and i have never looked back,
check this, after correctly prepping the block and head, i have been able to re-use my 2mm head gasket 3 times.
after i rebuild my motor it got rod knock, and i re-used the mhg,
after i rebuild it from rodknock i had crank work done and had the rod's resized and some more goodies added,
the motor has some noise in her still that sounded very similar to piston slap,
being i re-ringed her 3 times now, i decided it was time for a bore new pistons and what not, but i still through in the cleaned up used mhg,
the motor was rebuild a 3rd time due to the piston slap noise, and the head gasket is still in use today.
and i found my piston slap noise was a loose exhaust manifold bracket that i forgot to tighten down...........
when i built my brothers motor, he had a 2mm mhg that was installed on a machined head, and stock block, it did not appear to have any problems, but since we wanted to keep it that way and he needed a rebuild due to we bought the car knowing it had rod knock, we had the deck surfaced and we re-used his mhg and are not having any problems with either car.
both my brother's car and mine are bpu, full exhaust, maft pro, electric boost control, full rebuild, and have the oil changed when it becomes dirty darker them amber, or 3k miles witch ever comes first,
i forgot to add it in there along the way, but when i had my first block decked my machinest said he needed to remove .009" to make it flat again,
i would have never known this, even being a automotive student, i just dont have the tools nescary to take the measurents with, a feeler gauge and strait edge will work but is very hard to use while the engine is still in the car, it's hard to tell where the low or high spots are.
the warped block was replaced even after the head gasket held on it. the block had a crack running along the water jackets that didn't bother me to much, but when i needed a bore i decided it was the best time to suit for a better block.
i belive that the japense owner of my motor over heated the block enough times to crack it. but it very well could have been a casting defect.