head gasket
- Thread starter 88ttsupra
- Start date
what brand is what i mean. Is it an MLS head gasket or what? You need to give us more information so we know what you aret alking about.
88ttsupra;1299462 said:
Basically, the only thing it will do is lower your compression a little bit. Lower is better than higher in a turbocharged engine. It will work just fine, and if you do notice a small performance dropoff, all you have to do is add a tad more boost to compensate. This can be done by shimming the wastegate, or via a boost controller. It will work. Thinking about it, I'm more worried about the overall quality of the gasket, as opposed to the different bore size. Are you using the stock bolts? Are they new, or are you reusing the old ones. Did you completely clean the decks, and clean and chase the bolt holes? Or is this a fast and dirty job just so you can get rid of it?
rayall01;1300230 said:
just my dd cleaned the deck forgot about cleaning the bolt holes will do it soon as i get the head back and im reusing the stock head bolts.not boosting the hell out of her thats for sure! i got a ls1 for that!now i need is torqe specs for the head and cams anyone??thanks guys
88ttsupra;1300504 said:
There's a lot of opinions about headbolt torque for the MKIII, but me personally, I would not go over 75 ft lbs for the stock bolts. They are not sufficiently hardened. I would also use a moly lube on the threads, and on the bolt to washer seat to promote more accurate torque, and follow the retorqueing instructions found here. I saw the thread the other day, though I can't find it right now. The other factory torque specs can be found at this link: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/ It will give you everything else you need to know, including torque patterns and such.
Im wondering about the moly lube thing. Is it really safe to do this? TSRM calls to use engine oil for lube on the threads, and comparing it to arp ( 80ftlbs for moly and 120 ft lbs for oil) it seems like it would drastically change the torque
CyFi6;1301330 said:
Well since the weak link in this equation is low bolt torque, I feel that the higher and more accurate torque distribution of the moly would be beneficial under any circumstances. That's my opinion, based on what I've learned to date about torque lubrication.
Also, if you think about it, what you're saying with those specs, is that the bolts are actually torqued to about 18 ft. lbs. after oil drag differential is applied, with the stock parts and lube. Would you really want your torque value to be forty lbs. less than you set it for?
bolt is like spring
place spring in "tension" by PRE-LOADING
proper pre-load is dictated by bolt tensile
lubricants reduce friction coefficient at differing rates
lower friction means bolt reaches proper pre-load under LESS applied torque value
the "spring" under tension holds the parts in a JOINT with a range of expansion and contraction within which it will still keep the parts in tension. this is the key.
MOLY's can and DO reduce the torque required to achieve a given tension
good lubes can also help the torque applied to pre-load achieved value to be more consistent, therefore target tension more predictable
appropriate adjustment in applied torque is necessary to prevent JOINT FAILURE.
JOINT FAILURE occurs as a by-product of "LOSS OF TENSION", or compromised pre-load
loss of tension can be caused by vibration, expansion/contraction, bed-in or "seating-in" of the fastener flanges-to-parts in joint... or simply, OVER-TORQUE where the tensile of the fastener is EXCEEDED and it stops acting as a SPRING because it has "fatigued"... and is now "over-stretched"
Using low-coefficient lubes with low tensile fasteners and applying increased torque is a recipe for joint failure.
just some thoughts...
-crisp
place spring in "tension" by PRE-LOADING
proper pre-load is dictated by bolt tensile
lubricants reduce friction coefficient at differing rates
lower friction means bolt reaches proper pre-load under LESS applied torque value
the "spring" under tension holds the parts in a JOINT with a range of expansion and contraction within which it will still keep the parts in tension. this is the key.
MOLY's can and DO reduce the torque required to achieve a given tension
good lubes can also help the torque applied to pre-load achieved value to be more consistent, therefore target tension more predictable
appropriate adjustment in applied torque is necessary to prevent JOINT FAILURE.
JOINT FAILURE occurs as a by-product of "LOSS OF TENSION", or compromised pre-load
loss of tension can be caused by vibration, expansion/contraction, bed-in or "seating-in" of the fastener flanges-to-parts in joint... or simply, OVER-TORQUE where the tensile of the fastener is EXCEEDED and it stops acting as a SPRING because it has "fatigued"... and is now "over-stretched"
Using low-coefficient lubes with low tensile fasteners and applying increased torque is a recipe for joint failure.
just some thoughts...
-crisp
So for the non engineer you are saying: Using moly lube with stock bolts but keeping the same torque value is a bad idea
CyFi6;1303238 said:
in layman's terms... I'd not use the stock bolts under ANY circumstances.
to add to my above, a STUD and NUT joint are FAR more linear in their pre-loading of the stud. Simple reason... you are introducing BOTH tension AND twist into a BOLT, and the lack of a hardened washer under the bolt flange further compounds this effect.
yes is a safe answer in MY personal opinion.
G/L
-crisp
What i am really curious about is stock bolts with engine oil compared to stock bolts with moly lube at 72ft lbs. Would the bolt with moly lube not put more tension on the bolt than it was designed for? Thus making it unsafe/risking the integrity of the bolt?