so this was my second blown h.g. since ive had the car. i made a couple of mistakes the first time... using the same headbolts and not plaining the head. but this time i got new head bolts and im plaining the head... but mainly i have the post because im wanting to shave the head alot so i can have alot higher compression. my head was high in the middle by .009, and im just wanting shave alot off prety much until its before the piston hits, so im not sure how much to shave, and i know higher compression ill need higher octane fuel so it wont diesel, but im really wanting to know how much i should really take off so i dont fuck it up or anything and what kinda power increase i should expect. after all this is done this time, im planning on having a full cold air intake, 2.5 inch cat back exhaust, with the higher compression. so if anyone could give me some estimants thanks, and sorry bout this being so long
another blown head gasket
- Thread starter big idealist
- Start date
If you plan on increasing compression by milling a ton off the head/block you are asking for problems.
You dont want to take off too much because just like Sl1dewaysSupra said you are just asking for problems. If I were you I would just try and stay within the stock compression. Are you planning on putting a stock HG or a metal HG?
LOL Idealist.
These guys are answering you short because you want to play with the combustion in what would seem to be a design flaw in the mkIII. I hate to be cliche, but your'e playing with fire. We all know that we are facing potential problems with head gaskets. There are many other things on the car you can tinker with that don't really contribute to shortening of the auto's life span. Still getting you that little bit extra every time. The HG area should be off limits in your head for tweaking.
These guys are answering you short because you want to play with the combustion in what would seem to be a design flaw in the mkIII. I hate to be cliche, but your'e playing with fire. We all know that we are facing potential problems with head gaskets. There are many other things on the car you can tinker with that don't really contribute to shortening of the auto's life span. Still getting you that little bit extra every time. The HG area should be off limits in your head for tweaking.
thx for the info guys, but its prolly to late to do anyting because i already had it sent off, i guess we'll see what happens... but let me just ask... what would i need for doing this? would just a performance mhg do the job? or would i need more? cuz i would really like to have 11.5:1 or close to that...
The only way you will get that kind of compression would be high comp pistions. This link should help answer some questions.http://www.supramania.com/forums/showthread.php?t=26190&highlight=More+rebuild+questions
Consult the machinist to figure compression. I don't think you can get 11.5:1 from just decking. Higher compression pistons would also be needed.
The block and head must both be flat, not just the head.
The block and head must both be flat, not just the head.
11.5:1 compression is to much for pump gas, or right at the limit, iirc. You'd have to start running 110 octane from the track. No, I wouldn't use the head to do it. What if you ovrheat it and warp it again? Then you have to get a new head. Use the Felpro head gasket kit; its cheaper than Toyota's, and just as good. Torque those head bolts to 65, then check them after 1000 mi., and retorque them to 70. If you want power, turbo it, or get NOS. NOS is easier, and cheaper in the short term, but it puts alot of stress on the motor. Turbo is harder and more expensive in the short term, but not as hard on the motor in the long run.
I'm sorry cuel but I just don't agree with your head gasket philosophy. No disrespect. But I can't see why you would wait 1000 miles before retorquing the head bolts. I think you should shoot for 75lbs of pressure and then just keep it there. I think you should check the bolts after every heat cycle until they are done moving. So atleast once a day. Some may say this is overkill.
But I want this to be my first and inevitabley my LAST BHG. Felpro.... Who told you this crapolla???? the people at toyota?? Those are the only people who have ever recomended felpro to me. HKS stopper. BABY.
You want the mama of metal head gaskets. You want the 1 that the people using nos and turbo's are using. The theory behind this is there is no possible way for an NA to ever blow one provided the install is done correctly.
These are just opinions and there is a reason they are free.
But I want this to be my first and inevitabley my LAST BHG. Felpro.... Who told you this crapolla???? the people at toyota?? Those are the only people who have ever recomended felpro to me. HKS stopper. BABY.
You want the mama of metal head gaskets. You want the 1 that the people using nos and turbo's are using. The theory behind this is there is no possible way for an NA to ever blow one provided the install is done correctly.
These are just opinions and there is a reason they are free.
You want high compression? Do this: Call up you machinist, tell him to take off as little material as possible to get the head straight, have him do this on a CBN machine and get RA spec down to at least 20. Give him your block and have him do the exact same thing. Throw out those bolts you got and get ARP studs, torque to around 85 ft./lbs using moly lube. Get an HKS Stopper gasket, and AFPR with either cleaned and flow matched turbo injectors, or RC 550's or equivilant brand (PTE), Walbro fuel pump, and a good straight through 2.5" exhaust system, turbo TB, and start shopping for a place that will make some high comp. pistons for you 
.
.
Adjuster
Supramania Contributor
I'm guessing a few things here and there, but let me make sure I have this straight.
1) You want higher compression in a NA 7MGE.
2) Your goal was to use a stock composite head gasket and bolts.
There are problems/challenges galore with this, so bear with me.
The 7M has a pretty good combustion chamber design, but if you machine it down very much, your going to change the shape of the "squish" areas, and that might cause detonation problems, especially with the CR your shooting for.
As noted by someone else, you will not get that CR with a milled head alone, domed custom pistons would be needed to achieve it, and race fuel would be your engine's only diet thereafter.
You can also affect your cam timing, so adjustable cam sprockets might be needed to get the right timing back. There are many variables here depending on how much material is removed.
Here is what I'd reccomend.
Have your machine shop measure the head first. Check it for warping, and have it straightened if it's warped. (Takes a special oven, but it can be done, and done right.)
This will keep your cam journals in the right line. (If your head is warped, and you mill the deck flat, your cams are now warped.... not a great deal, and it could lead to early failure in that area.)
Now, with a flat head, mill it to the finest RA the shop can produce. (15ra is a good goal.) I would not lap the head unless they have a microflat lapping table, and lap on that table by moving the head, not moving the lapping block.
Replace your valve seals. Only have a 3 angle valve job done if there was a leak, in my experiance, the 7M head has few valve seat problems.
I'd reccomend replacing your valve springs with Comp Cams inner Big Block Chevy ones. (They are like 70.00 total, and a great upgrade to your tired old valve springs. These springs have slightly higher seat and open pressures, and also a better bind height, so if you want to run a higher lift cam in the future, they will accomodate that too.) Do a quick search, (The part number is 975 per the note below.(REVISED to correct my prior wrong number.)
Now comes the head gasket. Please do not put a stock type head gasket on your performance motor. They suck ass. There is no nice way to candy coat this people.
Also a good metal head gasket will allow you to fix what you screwed up by milling the head. Have your machinist figure out how much material was taken away, and get a MHG that is almost as thick as that amount please. Depending on the MHG, there are a few things you can do to help it seal up.
If it's coated with a thin hylomar or rubber, just install it dry, and you should be fine. If it's a bare metal gasket like the Greddy, I reccomend coating the gasket with brake quiet. (Do a quick search, there are tons of posts on this, and somewhere a write up on how to do it right in my opinion.)
I have the same Greddy MHG on my stroker 7MGTE 3.24L 10:1 CR and it works fine. (It has been on 4 engines, and did not leak on any of them.) Never use a gasket scraper on a MHG. Clean it up with brake cleaner, and a soft rag.
Now comes the fasteners. Save yourself time and money and just buy the ARP studs right now. Don't screw with stock bolts, or even the ARP ones. You want the studs if you want to never have to remove your head again.
Here is how to put it back on.
1) Clean everything, then clean it again.
2) DO not put the studs in first.
3) Assuming your block is flat, and has not been lapped in the car, a sure way to fuck up an engine if there ever was one, clean the block deck with a soft rag and brake cleaner. There should be no oil or dirt on the head gasket surface at all.
4) Using "The right Stuff" put down two beads of sealant about 1.5" long over the juction between the block and the front cover. This will seal up the joint there. Forget this step, and you will have oil leaks forever. Oil from the head drains down between the front cover and the engine block from the head.
5) Now, either with your brand new rubber coated MHG, or your brake quiet coated bare MHG, carefully lay the gasket in place. Do not slide it around. Do not slap it into place. Also make sure you have it lined up right, so it just locates onto the pins, and is perfectly lined up with the bores and other holes on your block. (This is especially true if you coated it with brake quiet. You get one chance to lay it down right, or you get to remove it, clean it and the block of brake quiet and start over again.)
6) Now with a friend, very carefully set the head down, again making sure you do not slide it around, but set it gently down over the alignment pins into place.
7) Now you install the studs. No need for loctite. Just use the Moly lube ARP provides. I found if you snip the end of the tube, you can wipe small amounts right on the stud threads, so it goes quite a long way. Put a small amount of moly lube onto the end that goes into the block side, and get your washer ready. Lube BOTH sides of the washer face, and using the stud as a guide, you slide the washer down into place as you put the stud into the hole in the head. (If you try and do this the other way, your washers will not all fit, and your pulling the studs to get them into place.. don't ask me how I found this out, the method I'm telling you is the fastest way to do this.)
Put the studs in finger tight. I did use a allen wrench to help do this, but DO NOT TOURQE the studs into place, Just finger tight/snug is all you want.
All your studs should be in the head at the same height. You will have moly lubed the threads, and both sides of the washers.
Now you put on the nuts. I like to smear moly lube onto the stud thread ends first, then put some on the face of the nut where it contacts the washer. The stud threads will lubricate the nut as you tourqe it down.
Put all your nuts on first just finger tight again.
Now wipe up all the moly lube and wash your hands.
Using a good quality click type tourqe wrench, your going to get this done right the first time.
Set the tourqe reading to 50 lbs and lock the collar. I like to use a short extension and a deep thinwalled socket works best for me. You can do this with the cams in place, but you will need to rotate the cams, so a large wrench to turn the cams will be needed.
Ok, start in the middle and work your way outwards in a X pattern. (See the TSRM for exact details.)
Your first pass goes from the middle out at 50lbs. This sets the head in place. You need to complete ALL of your tourqe passes at the same time. Don't start this unless you have time to go from setting the head to final tourqe figures.
Next pass is 60lbs. Change the setting on the tourqe wrench, and starting in the middle, tourqe them all to 60lbs.
Now change up to 70lbs. Repeat.
80lbs.
90lbs.
Now comes the final pass. I reccomend 100lbs for ARP studs on a MHG. It is not too much, or too little. My current engine has them at 103... why? I'm strange that's why.
I would not reccomend more than 110.
A key to getting the right tourqe reading is knowing how to use a tourqe wrench.
Practice some if you have never used one. (Your going to get lots of practice putting this head on, since your going to tourqe studs at 50, 60, 70, 80 and 90 lbs before your final pass at 100, so don't sweat this too much.)
The wrench has to be moving when it clicks to get an accurate read on tourqe. If you just put it on and click, you have shit for a reading. The fastener HAS TO BE MOVING to read tourqe. If it does not move, your reading friction.
After you do this for awhile, you will be able to gauge the click just before it happens, and you need to keep your movement smooth and even and then STOP when the wrench clicks. Some people like to double click, I think it makes no difference. (But I will double click anyway... LOL) BUT I don't move the wrench any further after it clicks. (There are some who say turn it 1/4 turn more... that's how fasteners get really screwed up in a hurry, so don't go there.)
Good luck on your head, and I hope your block is in good condition. If your block is screwed up, and someone has either lapped it in the car, or if it's warped past what the TSRM reccomends is allowed, your going to need to pull the motor, and have the block machined to fix it. No amount of gasket tricks will stop problems if the foundation is not flat.
1) You want higher compression in a NA 7MGE.
2) Your goal was to use a stock composite head gasket and bolts.
There are problems/challenges galore with this, so bear with me.
The 7M has a pretty good combustion chamber design, but if you machine it down very much, your going to change the shape of the "squish" areas, and that might cause detonation problems, especially with the CR your shooting for.
As noted by someone else, you will not get that CR with a milled head alone, domed custom pistons would be needed to achieve it, and race fuel would be your engine's only diet thereafter.
You can also affect your cam timing, so adjustable cam sprockets might be needed to get the right timing back. There are many variables here depending on how much material is removed.
Here is what I'd reccomend.
Have your machine shop measure the head first. Check it for warping, and have it straightened if it's warped. (Takes a special oven, but it can be done, and done right.)
This will keep your cam journals in the right line. (If your head is warped, and you mill the deck flat, your cams are now warped.... not a great deal, and it could lead to early failure in that area.)
Now, with a flat head, mill it to the finest RA the shop can produce. (15ra is a good goal.) I would not lap the head unless they have a microflat lapping table, and lap on that table by moving the head, not moving the lapping block.
Replace your valve seals. Only have a 3 angle valve job done if there was a leak, in my experiance, the 7M head has few valve seat problems.
I'd reccomend replacing your valve springs with Comp Cams inner Big Block Chevy ones. (They are like 70.00 total, and a great upgrade to your tired old valve springs. These springs have slightly higher seat and open pressures, and also a better bind height, so if you want to run a higher lift cam in the future, they will accomodate that too.) Do a quick search, (The part number is 975 per the note below.(REVISED to correct my prior wrong number.)
Now comes the head gasket. Please do not put a stock type head gasket on your performance motor. They suck ass. There is no nice way to candy coat this people.
Also a good metal head gasket will allow you to fix what you screwed up by milling the head. Have your machinist figure out how much material was taken away, and get a MHG that is almost as thick as that amount please. Depending on the MHG, there are a few things you can do to help it seal up.
If it's coated with a thin hylomar or rubber, just install it dry, and you should be fine. If it's a bare metal gasket like the Greddy, I reccomend coating the gasket with brake quiet. (Do a quick search, there are tons of posts on this, and somewhere a write up on how to do it right in my opinion.)
I have the same Greddy MHG on my stroker 7MGTE 3.24L 10:1 CR and it works fine. (It has been on 4 engines, and did not leak on any of them.) Never use a gasket scraper on a MHG. Clean it up with brake cleaner, and a soft rag.
Now comes the fasteners. Save yourself time and money and just buy the ARP studs right now. Don't screw with stock bolts, or even the ARP ones. You want the studs if you want to never have to remove your head again.
Here is how to put it back on.
1) Clean everything, then clean it again.
2) DO not put the studs in first.
3) Assuming your block is flat, and has not been lapped in the car, a sure way to fuck up an engine if there ever was one, clean the block deck with a soft rag and brake cleaner. There should be no oil or dirt on the head gasket surface at all.
4) Using "The right Stuff" put down two beads of sealant about 1.5" long over the juction between the block and the front cover. This will seal up the joint there. Forget this step, and you will have oil leaks forever. Oil from the head drains down between the front cover and the engine block from the head.
5) Now, either with your brand new rubber coated MHG, or your brake quiet coated bare MHG, carefully lay the gasket in place. Do not slide it around. Do not slap it into place. Also make sure you have it lined up right, so it just locates onto the pins, and is perfectly lined up with the bores and other holes on your block. (This is especially true if you coated it with brake quiet. You get one chance to lay it down right, or you get to remove it, clean it and the block of brake quiet and start over again.)
6) Now with a friend, very carefully set the head down, again making sure you do not slide it around, but set it gently down over the alignment pins into place.
7) Now you install the studs. No need for loctite. Just use the Moly lube ARP provides. I found if you snip the end of the tube, you can wipe small amounts right on the stud threads, so it goes quite a long way. Put a small amount of moly lube onto the end that goes into the block side, and get your washer ready. Lube BOTH sides of the washer face, and using the stud as a guide, you slide the washer down into place as you put the stud into the hole in the head. (If you try and do this the other way, your washers will not all fit, and your pulling the studs to get them into place.. don't ask me how I found this out, the method I'm telling you is the fastest way to do this.)
Put the studs in finger tight. I did use a allen wrench to help do this, but DO NOT TOURQE the studs into place, Just finger tight/snug is all you want.
All your studs should be in the head at the same height. You will have moly lubed the threads, and both sides of the washers.
Now you put on the nuts. I like to smear moly lube onto the stud thread ends first, then put some on the face of the nut where it contacts the washer. The stud threads will lubricate the nut as you tourqe it down.
Put all your nuts on first just finger tight again.
Now wipe up all the moly lube and wash your hands.
Using a good quality click type tourqe wrench, your going to get this done right the first time.
Set the tourqe reading to 50 lbs and lock the collar. I like to use a short extension and a deep thinwalled socket works best for me. You can do this with the cams in place, but you will need to rotate the cams, so a large wrench to turn the cams will be needed.
Ok, start in the middle and work your way outwards in a X pattern. (See the TSRM for exact details.)
Your first pass goes from the middle out at 50lbs. This sets the head in place. You need to complete ALL of your tourqe passes at the same time. Don't start this unless you have time to go from setting the head to final tourqe figures.
Next pass is 60lbs. Change the setting on the tourqe wrench, and starting in the middle, tourqe them all to 60lbs.
Now change up to 70lbs. Repeat.
80lbs.
90lbs.
Now comes the final pass. I reccomend 100lbs for ARP studs on a MHG. It is not too much, or too little. My current engine has them at 103... why? I'm strange that's why.
I would not reccomend more than 110.
A key to getting the right tourqe reading is knowing how to use a tourqe wrench.
Practice some if you have never used one. (Your going to get lots of practice putting this head on, since your going to tourqe studs at 50, 60, 70, 80 and 90 lbs before your final pass at 100, so don't sweat this too much.)
The wrench has to be moving when it clicks to get an accurate read on tourqe. If you just put it on and click, you have shit for a reading. The fastener HAS TO BE MOVING to read tourqe. If it does not move, your reading friction.
After you do this for awhile, you will be able to gauge the click just before it happens, and you need to keep your movement smooth and even and then STOP when the wrench clicks. Some people like to double click, I think it makes no difference. (But I will double click anyway... LOL) BUT I don't move the wrench any further after it clicks. (There are some who say turn it 1/4 turn more... that's how fasteners get really screwed up in a hurry, so don't go there.)
Good luck on your head, and I hope your block is in good condition. If your block is screwed up, and someone has either lapped it in the car, or if it's warped past what the TSRM reccomends is allowed, your going to need to pull the motor, and have the block machined to fix it. No amount of gasket tricks will stop problems if the foundation is not flat.
for anyone interested in the cheap upgraded valve springs, here's the info:
http://www.mkiiitech.com/forums/viewtopic.php?t=359
-shaeff
http://www.mkiiitech.com/forums/viewtopic.php?t=359
drjonez said:
-shaeff
Supramacist, you can get a "BHG" on a properly prepared engine with a metal head gasket.
Often it is the symptom of another problem. Overheating the engine will seperate the head from a block. The head and block are dissimilar metals. It is just like an old turn signal.
I know of at least one other Fel-Pro where the user blew the piston apart, and stock style composite gasket held together, at 500rwhp. Now this is rare, and I don't know why the piston failed before the gasket but it did. And it showed the importance of head and block preparation on any headgasket job. Half assing it is not the way. Which I think is agreed upon.
Often it is the symptom of another problem. Overheating the engine will seperate the head from a block. The head and block are dissimilar metals. It is just like an old turn signal.
I know of at least one other Fel-Pro where the user blew the piston apart, and stock style composite gasket held together, at 500rwhp. Now this is rare, and I don't know why the piston failed before the gasket but it did. And it showed the importance of head and block preparation on any headgasket job. Half assing it is not the way. Which I think is agreed upon.
We certainly agree on that. I keep finding with all of the time that I spend on these sites, everyone has their own way of doing things and that doesn't really make it right or wrong. I personally just try to do the best on everything I do to this engine all the while hoping and praying that after I get it back together it runs right and doesn't have new problems.
This is the last time I will rebuild this car. If it craps out afterward..., I am pulling the plate and walking away. The city can have it. I'll obviously work on it to some extent but after all of this shit....., I am going back to nissan and will never buy another toyota. This car has been a nightmare.
This is the last time I will rebuild this car. If it craps out afterward..., I am pulling the plate and walking away. The city can have it. I'll obviously work on it to some extent but after all of this shit....., I am going back to nissan and will never buy another toyota. This car has been a nightmare.
shaeff said:
So those springs are a true bolt on affair, no other prepping/modding is needed to make them work?
Adjuster
Supramania Contributor
I'm running them, no problems.
They are slightly tight when I was installing them, the stock ones are slightly smaller outside diameter v/s these, but it's so close, the springs fully seat just by installing the locks, and I don't see any future wear issues between the head and the spring. (The softer alloy in the head would just burnish smooth, and the spring would be un-affected.)
The really nice part of this mod is they are very low cost, very high quality, and the higher pressures would give anyone who plans on running the engine at high rpm confidence there would be no valve train problems. (Besides, your old springs are well worn out after 100,000miles or more.)
I would do this on every single re-build, or any time you do the head on a 7M engine.
They are slightly tight when I was installing them, the stock ones are slightly smaller outside diameter v/s these, but it's so close, the springs fully seat just by installing the locks, and I don't see any future wear issues between the head and the spring. (The softer alloy in the head would just burnish smooth, and the spring would be un-affected.)
The really nice part of this mod is they are very low cost, very high quality, and the higher pressures would give anyone who plans on running the engine at high rpm confidence there would be no valve train problems. (Besides, your old springs are well worn out after 100,000miles or more.)
I would do this on every single re-build, or any time you do the head on a 7M engine.
lol Supramacist, I never said Felpro was the best, just as good as Toyota's stock gasket at a better price. The Felpro will last just as long as the metal gasket: right to the point where you over heat the motor again. As far as you not agreeing with how I retorque heads: You're right. What would I know? I've only been a full time mechanic for almost 10 years... By the way, I used a Felpro kit to do the head gasket when I bought my n/a Supra almost two years ago. Stock bolts to. Even a cheap Gates timing belt. Most of my driving time is highway, and I'm already at 70+ when I hit the on ramp. Love the way it shifts 1st through 3rd at over 6k. My car lives at over 3k rpm's(came with the 4.3 LSD and w58), if it isn't stopped or parked. I torqued the head bolts as I described. Recently, outta curiosity, I checked the torque on the head bolts. They were all torqued to 70, right where I set them. Mods: OBX header, test pipe, my own exhaust, cold air kit(made by me to), MSD Blaster ss coil and 8.8 mm wires with Bosch plat. +4 plugs and short shifter. Cams and adjustable gears are next. The local Honda racers get a good view of my tail lights, and I have yet to run across another n/a 7m that can even hope to hang with me. When I get around to porting the head, over sized pistons, and maybe a turbo kit on my other motor, I'll do it the way people like Adjuster recommend.