Re-torqueing heads

The torque figures given by the VW factory, are for new studs and nuts, lubricated with a bit of oil, so tightening to 75% is not required cause of the lubricating properties of the antiseize. This is the first time I've heard something like that for a VW.

Anyway, the major reason for retorquing the heads on a VW engine, is because when the heads or the case are new, they will give a little in the begining. The cylinders will sink a bit on the heads and on the case, the studs will pull out a bit. So, the tightening force holding the heads decreases, initially with a high rate. As the engine ages and sees many heating - cooling cycles, the tightening force is decreased but in a much slower rate.

Your engine was not new, so if you had torqued it to factory specs, there wouldn't be any reason for a retorque now. I don't think that it is imperative to drop the engine imediatelly just to retorque the heads, unless you bellieve that a head rattles loose... You can wait a bit, until you also have some other reason to drop the engine, or till you won't see it as a stupid boring task, but as pleasure and a chance to practice on R&R your engine ;-)

Bill, '67 Bug.

File /me/ in the "There's A First Time For Everything, Dept."

Gotcha.

Thanks for advice. I seem to see some upcoming reasons to drop Mr. Engine, so I'll check Ye Head Torque (mine) at that time.

I don't think there is any reason to retorque VW heads, as long as they were properly torqued in the first place. Retorquing is (was) more common on older cars with head gaskets which crushed and relaxed, thus requiring some "freshening."

To be fair, crummy rebuilds may leave uneven surfaces in the heads and on the case where the cylinders seat. These might well crush a bit when new, but a good rebuild will clean up all of those surfaces and they won't give measurably in the next 20k miles.

Why would anyone recommend that you torque to less than full torque? Proper torque requires and assumes lubricated (not dry) threads. I doubt if the kind of lubrication matters much, and anti-seize here might promote loosening later on. It happens often enough anyway.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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This would be my own "smarts" at work. Note the quotes. When I was removing the head nuts, the ones not in the valve covers were all kind of seized and rusty. Poking around the 'net I stumbled upon that page where a fellow was putting together that Corvair engine. He mentioned "Bob" a couple of times. This appears to be the esteemed Mr. Hoover, who as we all know, knows his onions. The engine guy used anti-seize on the head bolts.

Thought I (with all of my cylinders firing), "seems to be a respectable idea." Did I post this thought on RAMVA for discussion, debate, opinions and derision? Nay, I did not -- I threw myself on this grenade alone. A fellow needs to try to think independently once in a while, make his own darn mistakes, and take his lumps. If I can avoid turning the Wonderbus into the Blunderbus, make it better, learn a few things and have some fun on the way, I'm happy.

Now, if it was a bad idea, then I'd like to know about it. Take a look at

and see if that fellow seems clueless, or if the engine he's working on is sufficiently different from my 1776 that what I did is a Bad Thing.

HMMMMM INTERESTING PROBLEM , I SUGGEST YOU FIND YERSELF A TRUSTWORTHY AND COMPETENT MECHANIC, IF THAT DOESNT WORK, I SUGGEST YOU INSURE THE CAR FOR TWICE ITS REAL VALUE AND ARRANGE FOR A COMPETENT AND TRUSTWORTHY CAR THIEF TO ARRANGE THE THEFT OF YOUR VEHICLE AND THE SUBSEQUENT ARSON OF SAME. THANK YOU FOR YOUR TIME SIR.

I already did, and I found it interesting, since I know nothing about the inside of a Corvair engine. While most of what he said seemed to make sense to me, I still can't see any reason to undertorque your head studs.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Loctite's anti-seize catalog at

http://c Torque guide Proper clamp load is an essential part of any bolted assembly for trouble-free operations. Torquing either nut or bolt creates the clamp load. Anti-Seize lubricant used on a bolt helps to develop greater clamp load for the same torque compared to an unlubricated bolt. An additional benefit is greater uniformity in clamp load among a series of bolts.

The relationship between torque and clamp load is expressed in the following equation:

T = KFD

Where: T = Torque (in-lb, ft-lb, N-m) F = Clamp Load (lb, N) D = Nominal diameter of bolt (in, ft, m) K = Torque coefficient or nut factor, determined experimentally

K Factors: K factors are obtained on Grade 8, 1/2?? steel bolts and grade 5 nuts by a test procedure which measures torque tension properties. Lubricant was applied to the bolt threads and both faces of the washer.

***************

SAF-T-EZE's brochure says, "SAF-T-EZE® Anti-Seize compounds provide maximum bolt tension from minimum wrench torque. In fact, at least 20% less torque is required to get the prescribed tension than to get the prescribed tension than with dry parts. With either Regular, Copper or Nickel Anti-Seize, you get uniform bolt tension and substantial release torque time after time that must be overcome for parts to be disassembled."

BUT (this just in) from

: "I've spoken with Rich L., Application Engineer with Loctite (he will send me some bolt tension charts (NLA) for the graphite containing formulations of C5A, Silver, and Nickel AS products, which relate the dry torques to the lubed torques...I'll evaluate this when I get it and put something together for SwEm site Service Notes page) but he confirmed the following: For headbolts, for which fastening torques are specified for oiled bolts, it is NOT necessary to adjust (decrease) the dry torquespec given, since `lubed by oil' can pretty much be, for the purpose of this discussion, considered to be equal to, `lubed by AS'. Soooooooo, torque away...to the numbers given!"

So maybe I undertorqued four of the bolts. The ones, of course, that cannot be reached w/o removing the engine.

Darn.

I would suggest to drive the engine gently, for short daily itineraries, because the uneven stress on the heads could cause damage if you get them very hot. Or you could loosen a bit the lower nuts to the same torque as the top nuts, until you can remove the engine and torque them properly. If you decide to do this, you must be careful not to loosen completely the lower nuts before retightening. Loosen just a bit, one by one, and immediately tighten, until the torque wrench clicks. If it clicks without the nut rotating, you got to loosen a bit more. First do the 2 center nuts, then the two outer nuts.

Bill, '67 Bug.

Thank-ee, Bill.

I'm afraid so. The key here, as you've probably noticed, is that all the quotes mention "as compared to a dry thread", but torques are never specified for dry threads. While there is probably some small difference in friction between threads lubed with different lubricants, the difference is slight compared to that between lubed and dry.

I suggest you figure out a way to bring up the torque on your head bolts. Since you said this was just 4 bolts, I suspect you can do this without pulling the engine. Loosen all 8 of them JUST ENOUGH that they can each be driven forward some at the proper torque.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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(In Johnny Carson voice): I did not know that.

Even I have noticed a difference between dry and lubed . . . and in threads, too.

I'll stare at the engine for a while to see if I can figure out how to get the upper cylinder tins off while the engine is in the bus. I don't remember where all the bolts are. Hard to stuff new info into a 54 year-old brain.