The Small Questions Thread

[Janch]

Hey guys i really need your advice.

its about head gasket thickness.

Head has been machined 0,2mm and block 0,5mm !!!! so total of 0,7mm. i have in mind using cometic head gasket and i think its 1,3mm.... i know there is some reserve that can be machined while still using stock head gasket. is it OK tu use it? should get answer ASAP.

 

[chevyguyjoe]

Sounds like you need a 2.0mm head gasket. Id use the cometic 0.080" thickness if you intend to keep stock compression. http://www.shopengineparts.com/prod...us&model=7M-GTE+3.0L+87-92+2054cc&type=engine

 

[rhs]

I know little about ECUs, but will be in the market soon. I've seen the Power FC thrown around in lots of forums. Finding a 1JZ specific one is hard, but 240sx ones are pretty cheap and readily available on eBay. Minus making a patch harness, is there a glaring issue with an 240sx specific ecu?

They do make a Chaser specific Power FC, which is the 1JZ I have, but if I can save $600...although I have a non-vvti and the power FC says for vvti.

 

[Janch]

Hey i know i asked head gasket thickness question but ill ask it again differently.

Can i still use stock thickness head gasket if head + block are machined 0.7mm. i know about higher compression - im not planning to run more than 15psi in any near future but im just anxious about valves hitting pistons. i have 1.3mm cometic HG i really would like not to buy new one if possible.

Is it OK?

 

[Grandavi]

15 psi on what turbo.
What engine? I'm assuming 7m and if so you have a bit of learning to do. 15 psi requires some thought if your running ct26

 

[Janch]

I know grandavi ive learned a lot and know all supporting mods and upgrades needed to run past fuel cut.

yes its 7m and yes its ct26 and yes i know stock ct26 doesnt like more than 12ish psi. for more than half year it will stay no more than 10psi anyways plus i have to break in the engine after rebuild.

 

[Grandavi]

I'm just saying that your talking about a non standard setup which can lead to other complications. I've run a 57 and 60-1 trim on my 7m at 10-12-14-16 psi and the turbo doesn't flow very well for anything over 14. 12 is the best area but it will run out of breath up top.

I would use standard head gasket sizing (taking into account the machining) simply because your stressing an older engine design that suffers from cooling issues near cylinder 5-6. If your going to go non standard, there should be sound reasoning and planning involved.

I'm not sure at what number the valves would touch the piston, though so can't help you there, but there is a write up I will try to find for you where that happened. That may contain the answer your looking for

 

[Janch]

thank you im looking forward to that write up

yeah with CT26 is same like with 14b on my GS-T eclipse. hates top end even on stock boost.

 

[MK3pizzadriver]

Why is it that every middle tail piece I see still has the molding attached to the bottom? Does anyone know if it's possible to remove just the molding from the car without having to remove the whole piece?

-edit- Nevermind, took the piece off and figured it out. I though the side moldings were a more durable plastic or hard rubber, but I guess their the same plastic as the license plate surround, as it's all one piece back there. I guess on the '89+ moldings, they expect the little insert on the bottom of the moldings to do all the protecting lol.

 

[Grandavi]

thank you im looking forward to that write up

yeah with CT26 is same like with 14b on my GS-T eclipse. hates top end even on stock boost.

Some links as I search:

http://www.supramania.com/forums/showthread.php?97203-Head-Gasket-thickness-selection

Read post 2 (not specifically answered, but excellent info)
http://www.supramania.com/forums/showthread.php?276-Specific-7mgte-Rebuild-Tips

The following is from Toyota Nation (the last part is the answer):


i am getting my block machined and it is being decked. i measured the piston to deck clearance and it has .006" above the deck of the block already. i was wondering what the spec is for piston to valve clearance? since it doesn't seem like there is a spec for piston to deck clearance? also what is the stock headgasket thickness. Thanks


Guyana00
May 15, 2009 - #2

You have to measure the total height of the block and head. Subtract those from the stock height and that is the total amount remove from both the block and head. Make it up wit different thicknesses of metal headgaskets.


UNATUL APIRTED
May 18, 2009 - #3

that just doesn't seem like an easy way to find your headgasket thickness. there should be a spec for at least piston to valve clearance and thats really all i need to know what size headgasket to use after the machining has been done


SupraTuned
May 18, 2009 - #4

Its alright my friend! Go with Cometic! They are a great company, they have all of the specs for our cars, and they will custom make the size you need, with all appropriate tolerances. All you need to do is add together the amount taken off of your block (don't forget the timing plate on the front of the engine like I did!), the amount (if any) taken off of your head, convert it to mm, and add 1mm for stock thickness and tell them that is what you need when compressed. Price is a about 60 more, but well worth the exact match. I didn't really know what to do either when I had to do mine.


Guyana00
May 18, 2009 - #5

First off, it is very damn easy. Two measurements. Even if for some reason you're going to struggle, get the machine shop to measure it more accurately than you would and there, no work involed. Work a few number assuming you know how you add or use a calculator and you have your gasket thickness. Even if it weren't that easy, when you're doing the headgasket, especially on them 7M you need to do it right or don't bother or you'll be back in this position or worse in short time. Make sure the front plate is machined along with the block as mentioned, depending on what mhg you go with make sure the RA is within spec for that HG. When it's done right you'll be glad, you can turn up the boost, abuse your engine and never turn back.


UNATUL APIRTED
May 19, 2009 - #6

yeah i will know how much is taken off of the block but i am buyin a re-man head because my cam journals are scored...so i have to replace it. so i guess unless i have a spec for the head height or whatever i will not know... is there really not a spec for piston to valve clearance or is that just not the way to go on the 7mgte engine??


Guyana00
May 19, 2009 - #7

Here are some number that will help you determine the correct headgaket thickness. Valve clearance will be stock or within spec as long as this formula is followed. ----------------------------------------------------------------- Stock head height = 116mm deck to valve cover surface Stock block height = 198.5mm deck to main crank saddle ----------------------------------------------------------------- Next, measure you head and block height, from the same spots, get your machine shop to do it if you cant and tell them where to measure from. Then, subtract is from the stock heights. Add those together, add 1.37mm for stock HG thickness when compressed. Buy the appropriate headgasket, if there isn;t one close enough, for about the same price comeitc will make one for you. While you're at it see if your cylinders are going to be bored. This will be an important part of choosing the headgasket, stock bored is 83mm, even if it's not going to be bored, get your machine shop to check it in case it was previously done. EXAMPLE: ----------- Your block height AFTER machining and RA spec is met is 198.00mm (don't forget the timing plate. You head height AFTER machining is 115.37mm 198.5 - 198.00 = 0.50mm 116.0 - 115.37 = 0.63mm Stock HG = 1.37mm ------------------------------ Total = 2.5mm Consider your cylinder bore as you need cylinder bore AND thickness when consider gasket size. As I said, if there is no appropriate pre-made gasket for you, get one made. You do it like this and the head and block are within the RA spec, install it properly and you never need to look back.

 

[AaronB]

http://thumbs.ebaystatic.com/images/g/6OgAAOSwstxVdQtB/s-l225.jpg

Anyone know what rear bumper this is? I can't seem to find any info or any reason to move the plate from the factory location.

 

[IchibanEye]

Here is the current run down. I've checked all hoses, all grounds. The engine does not hesitate nor are any odd sounds heard. The car had only around 4000 miles o.k. basically a complete rebuilt. Suspension motor and the like. Issues currently are: When dipping around a corner at speed this warning light has started illuminating during hard cornering. It is to the left of my temperature gauge all my itself. It looks like a circus tent when it lights up. What is it? I've looked for it in my manuals and factory books. Nothing. My guess was fluid level. But fluid is fine currently. Please hit me with your thoughts on this. O.k. the second issue is this: When I start breaking at a high rate of speed my engine light illuminates. Keep in mind I'm not slamming on the breaks and I'm using medium breaking force. Any ideas on this would be appreciated also. Thank you.

 

[cinderMK3]

that light is the birdcage Low coolant

Edit - I had this once I completely emptied out the front reservoir after a rebuild and forgot to put a little in it.

I've heard horrible things when that light comes on BHG being the main cause, not saying that's whats up, just the usual culprite

 

[IchibanEye]

Id'e see other indicators out the tail-pipe. Im not a true noob. That head has been addressed correctly before hand. I'll check the levels again

 

[Grandavi]

Not true. My headgasket was leaking only under full boost and it was only pushing out coolant. That's a rare situation mind you. Generally speaking it could be a whole raft of things but if that light comes on its because your driving and the coolant is low (nine times out of ten). It could be a pinhole leak in a line, or radiator leak, etc. not always headgasket. However, headgasket S on a 7m usually let out slowly at first and then really quick when it gives out fully. Commonly on the 5-6 piston area. You won't see it at the tail pipe until it starts letting through a lot of coolant.

I find the best test initially is a exhaust gas test in the rad. A kit costs about 65.00 on Amazon and can be used a lot of times. I test all my used cars with it as I have found it to be a great early indicator.

Another little problem I have found with an older 7m... Those that don't use correct coolant maintenance and have an older 7m can have a rusted block heater (if it has one) that can cause issues.

 

[IchibanEye]

Not true. My headgasket was leaking only under full boost and it was only pushing out coolant. That's a rare situation mind you. Generally speaking it could be a whole raft of things but if that light comes on its because your driving and the coolant is low (nine times out of ten). It could be a pinhole leak in a line, or radiator leak, etc. not always headgasket. However, headgasket S on a 7m usually let out slowly at first and then really quick when it gives out fully. Commonly on the 5-6 piston area. You won't see it at the tail pipe until it starts letting through a lot of coolant.

I find the best test initially is a exhaust gas test in the rad. A kit costs about 65.00 on Amazon and can be used a lot of times. I test all my used cars with it as I have found it to be a great early indicator.

Another little problem I have found with an older 7m... Those that don't use correct coolant maintenance and have an older 7m can have a rusted block heater (if it has one) that can cause issues.

Thank you for the ideas. The whole motor was rebuilt and done correctly too. So...if its the HG it's a freak thing this time around. Which would be a real kick in the sack after 15k in replaced and new parts. I'm going to get that radiator exhaust gas test kit. Do you have any thoughts on the engine light only illuminating when apply the breaks at high speed? Thank you for chiming in. I also wanted to add not everything will be visual out the exhaust sometimes smell can tell you things too. I'm sure you know this, I just wanted to clarify. Cheers!

 

[rhs]

Does anyone know what studs to get for the differential to half-shaft hub? They look similar to an M10 wheel stud. I got some jacked up threads on a couple.

 

[te72]

Does anyone know what studs to get for the differential to half-shaft hub? They look similar to an M10 wheel stud. I got some jacked up threads on a couple.

I think this might be helpful, although whether or not you can get your hands on some of these parts these days...

http://www.cygnusx1.net/Supra/Library/EPC/291410/catalog.aspx?F=4101&P=1

There are six of them on all Supras I've been underneath, but I believe the diagram # you are after is 41334A, which has two part numbers from Toyota: 90114-10003 and 90114-10028. I could be mistaken, so take a closer look for yourself, but I do believe those are the axle studs... but it is late. Good luck!

 

[rhs]

I think this might be helpful, although whether or not you can get your hands on some of these parts these days...

http://www.cygnusx1.net/Supra/Library/EPC/291410/catalog.aspx?F=4101&P=1

There are six of them on all Supras I've been underneath, but I believe the diagram # you are after is 41334A, which has two part numbers from Toyota: 90114-10003 and 90114-10028. I could be mistaken, so take a closer look for yourself, but I do believe those are the axle studs... but it is late. Good luck!

Thanks, I'll see if I can track those down. I'd like to get it in this weekend though, so I may have to run 4 nuts for the time being...

 

[Janch]

Guys is there anything else besides cracked head, block, bhg that could cause high pressure in cooling system. Also i noticed a bit of somekinda smoke when removing oil cap.