Valve cover grommets Q

[icey756]

Well i think its overdue that i get my own torque wrench anyway so I'll do some more research. When I got the studs thats what they said to torque to i think. Maybe it is a typo but i would have to double check. Pretty sure i made 3 passes of 30, 60 and then 90

[cre]

Originally Posted by icey756

When I got the studs thats what they said to torque to i think. Maybe it is a typo but i would have to double check. Pretty sure i made 3 passes of 30, 60 and then 90

We've covered this. There IS a difference depending on whether you installed studs or bolts just as the type of lube makes a difference. If you installed studs and used the supplied moly grease then you've done well and need not worry... Bolts on the other hand you would only torque to 90 if you used motor oil in lieu of a good moly lube. Follow?

[icey756]

yes i follow. And sorry i mean i have bolts not studs. We just used the stuff they gave us and torqued them to 90. No oil involved. Why is that a big deal?

[cre]

Google fasteners and yield strength. The head isn't designed for that level of torque (hell, your rims aren't and they have a beefier cross section) and the fasteners are designed to remain within a certain margin to maintain a specific level of elasticity.... Who told you to just "go ahead"? If it was in a thread on here let me know so I can remove it. If Toyota designed for using torque to yield fasteners (aka TTY) you'd be in real deep shit.


EDIT: On second thought don't Google it, you'll find all the bad info first. Go buy some mechanical engineering texts and start studying.... or read the directions next time (they're not included because the manufacturer is bored).

I posted a little more on this here: http://www.toyota-supra.info/forums/...ad-gasket.html ...and a lot more on the subject in the past.

[icey756]

what do u suggest i do then? Loosen them or what?

[cre]

Either way it's a gamble now. Compromised head or compromised HG either way if it fails you're going to have to redo the job. I'd also be disinclined to reuse those bolts in the future whether they measure to spec or not. Loosening the fasteners that much is sure to compromise the HG's seal.

Myself, I'd redo the job but then I can get through it quickly. You can try and just ride it out a few people have done so without issue... and some have the head crack on them the head. Your odds are still better than those who toss a MHG on an unmachined block (although that's not saying much as that fails 90% of the time and you've probably got better than a 50/50 shot of things working out fine). You're not going to lose much if you try to ride it out and you can get a replacement head from a GE for little money; You'll need to re-shim the lifters when you swap over the intake cam but you should do those on both sides anyway.

Did you use moly when installing the bolts? Did you chase the threads in the block as directed? If you answer no to either of these well you may be in good shape but in bad shape for another reason.

Why don't people read the manual? These aren't made of Legos and nothing close to as simple as hanging drywall.

[cre]

I'm not trying to present an overly grim picture for you... but I'm definitely not going to portray it as something which is just fine and dandy... it's not and something may go wrong and cost you a good amount of time and money (and no one but you will be the least bit surprised).

[icey756]

When i took my head to the machine shop he told me he had to take off almost all that was allowed in order to get it right. He had some book that told him how much he could take off i guess. But i could see that if he took off more he would be cutting into something on the side. I wouldn't mind redoing the job but then again to me it would be a waste of time. Later on I want to bore the cylinders and have forged internals. Thats the point at which i would put in studs, get a new head, rebuild the engine, and get a better clutch. If by moly you mean the grease like stuff that came with the bolts then yes we did. If by chasing the threads you mean cleaning them out then yes we did. I'm not quite sure as to what manual you are referring to as far as "reading the manual" goes. To me i would rather have it over tight then not tight enough.

[cre]

Originally Posted by icey756

To me i would rather have it over tight then not tight enough.

And that is where you've gone grievously wrong. Trust me, 99.999% of the time, the engineers who wrote the book (and in some cases helped design the parts/engine/car/whatever) know a LOT more than you. Heads warp or crack from this kind of mentality... So do rims and brake components; Fuel systems develop cracks, leak and start fires. I don't care if you strip a bolt that's holding in your stereo, but if you're putting 50lbs on a caliper glide bolt which is spec'd for 27 just because you think it's a good idea then you're asking for a fool's end.... I REALLY hope you took greater care when reinstalling your fuel components and lines.

I asked about the lube because different types of lube perform differently. Torquing head bolts to 90ft lbs when using regular 30 weight oil is close to torquing to only 75ft lbs using moly (because moly is a much more efficient lubricant). The torque isn't really the pressure you're aiming for, what you're aiming for is the axial load or clamping force (radial stresses are another concern). Torque offers a simpler way of getting a fastener to within a desired load range. As long the factors involved are as consistent as possible the load on each fastener is more likely to be uniform with those neighboring it and thus less likely to cause undo and uneven stress. One of the biggest factors is friction: threads, cap and washers and lubricants used. Some fasteners actually are hollow so you can measure just how much it has stretched as it is tightened and calculate the clamping force that's been reached... Naturally there are other requirements which render them an impractical solution for your average job. There is a crazy amount of physics behind things as simple as a bolt; I can't say I really understand all of it myself.

Just so you and anyone else reading understands how big of a difference this really is; If assembled dry at 90ft lbs you've got about 11500 lbs of force on each bolt (this doesn't even include the radial stresses). It's supposed to have only around 9500 lbs. Allowing for variances in each fastener, the threads and other point of friction these numbers will vary a bit from one bolt to the next and with the molybdenum lubricant it's significantly higher. So does 2000 POUNDS of pressure past the bolts rated ability still make you feel better? You couldn't get me to jump out of a plane with a parachute that's rated for even one ounce less than I weight...

Chasing threads (with a thread chase sometimes called a "cleaning chase") is when you use a thread chase to redefine/restore the threads; It's not just about cleaning but it does that too. Lacking a chase you may use a tap but it's not the best as it always removes additional material and can easily ruin good threads and weaken the overall assembly if not started with care. Think of a thread chase as a gentle and slightly rounded tap.

At this point I would probably take more of a "fuck it" attitude... It's not a customer's car, right? If the head hasn't been retorqued yet I might go ahead and back off each fastener 1/4 turn and then one more 1/4 turn. From there I'd measure each with a beam torque wrench, in order, until the tightest one was identified. Torque the others (again in order) until they all meet that one and then give it one more pass and tighten each just 4 or 5 ft lbs to try to ensure uniformity. Run it for a few heat cycles (drive it for a week) and torque a final time to make sure they're all even (back them 1/8 turn or so and then torque back to whatever level you settled on). If you've already re-torqued the bolts and put several hundred miles on it I wouldn't really try much beyond backing them off 1/4 turn (if even that).

Did you have the block resurfaced? If not did you measure it and make sure it is straight?

[icey756]

Thanks for the info cre it gave me a better idea. We didnt shave the block but it was fine. We used a stock head gasket because we didnt shave the block.