bj

Hi All

Anyone know what this value is?

Thanx in advance
90C2
Bill

91C2wrencher

BJ, Don't know exactly what this means but it's from the little spec book I use.

"cylinder head bolts"

1st Stage 15 Nm (11 ft/lb)

2nd Stage 1 Nm (o.73 ft/lb) x 90 deg (plus/minus)2 deg. torque angle

I know that cylinder head bolts on most engines must be tightened in a sequence and in steps, Now if one of the more knowledgable guys can chime in and explain what these ratings mean, we'll all be a little smarter.

bj

Thanks Wrencher

Since I'm doing a valve adjust I thought I might retorque in the hopes it might stop a swetting cylinder number one. First stage I would assume is the value one torques to on the first step and then the second stage one would perform some type of angle torque to strech the stud. All I need is a final torque setting if anyone out there can tell me?

Thanks in advance
90C2
Bill

91C2wrencher

BJ, your a braver man than me! I'd be VERY careful twisting those head nuts. In fact I wouldn't do it at all, but hey thats me and my motor is tight.

bj

Dear Wrencher

Believe me I'll be shaking like a bunny inside if I actually follow through with the retorque. I'll probably apply the minimum torque around the cylinder in question then surrounding cylinders - slowly building up to the specified torque if I'm feeling brave at the time. After all it's just sweating and no real drips are occurring. Just trying to get all my ducks in line before I actually start the job!

Bill
90C2

bj

Dear Wrencher

Believe me I'll be shaking like a bunny inside if I actually follow through with the retorque. I'll probably apply the minimum torque around the cylinder in question then surrounding cylinders - slowly building up to the specified torque if I'm feeling brave at the time. After all it's just sweating and no real drips are occurring. Just trying to get all my ducks in line before I actually start the job!

Bill
90C2

91C2wrencher

BJ, I've got a golden rule, if the "little project" I'm about to do can go from $0 to $mega in a heartbeat, I usually let my pro-wrench have at it. This uaually means I don't fock around with the long block.

Cupcar

What do you mean by a "sweating cylinder #1", if you mean the joint between the camshaft housing and the cylinder head the 6 studs for each cylinder head to camshaft housing have a torque of 18 pound feet.

Sweating of oil does not usually occurr between the head to cylinder joint. Retorqueing these in a 964 is an interesting question. Early Dilavar studded cars were torqued to 29 pound feet, the 964 spec is to lube the threads with Optimoly and first torque to 11 pound feet then turn the nut precisely 90 degrees furthur using a torque angle method. I don't know how to reduplicate this process once the engine is assembled because you certainly don't want to loosen things and start over.

I recently assembled an engine with Dilavar studs and did my initial torque to 11 pound feet then did the second torque cycle to 29 pound feet. Quess what? The second run to 29 pound feet required a turn of around 95 degrees in each case, close to the 90 the torque angle method would have had. So maybe a retorque to 29 for the cylinder heads would be the thing to do. Anyone else have some ideas? <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

Dave R.

BJ,

if the bolts you are planning on retorquing were designed to (non-reversibly) stretch as part of the initial torquing process, then it might be wiser to replace them (and torque anew) than retorque them.

The stretched bolts are not going to act the same way as a new bolt.

-Dave

91C2wrencher

Like I said BJ you're a braver man than me. Cupcar is right on the "camshaft housing to cylinder head" @ 17 0r 18 ft/lb. Both he and Dave are correct in the stretch to torque studs with lube, one time, ons shot deal. I doubt they would torque the same now and remember if it can go from $0 to $mega in a heartbeat.....do you really want to be the one that finds out what happens when....

Cupcar

It should be made clear that none of the studs in discussion here-the camshaft housing to cylinder head and head to crankcase studs- are NOT routinely replaced once torqued. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

bj

Gentlemen

You've provide a lot of great info and thank you for your opinions - I really appreciate it. What I mean my sweating is a darkening of the outer cylinder concentrated around the exhaust port. Either the oil is eminating from the base (i.e. cylinder to crankcase) or from the top (i.e. cylinder to head mating surface or both). I'm not sure which way gravity would cause oil to travel. If it's coming from the head area I might be lucky and a new valve cover gasket will solve the problem. Is there a seal between the camshaft housing and the head? If it's the head to cylinder or head to crankcase then a retorque of the 4 nuts on each cylinder stud set may be attempted. I pointed out the leak to a mechanic who I took the car to for the Hammer who said if I was was serious about fixing it he would first try a retorque before actually machining a groove in the base of the cylinder (i.e. one of the more economical fixes for this type of problem)for an "O" ring seal. I figured I could do the retorque myself. What I might do, is see what torque the other studs are set to by incrementally increasing the torque on the wrench until their torque setting is determined. Then I would incrementally apply this torque on the cylinder in question. If the torque setting I determine is 29 ft-lbs for example (i.e as Cupcar pointed out) and the cylinder studs in question can't even take 20 ft-lbs (i.e. I'm exagerating to make a point) then there definitely is a problem with the torque set on these studs. Of course I expect at most a 10% difference to cause this type of leak. Who knows maybe I'll discover a broken stud - not likely but I don't know unless I try. What I see happening possibly is that I won't even be able to get a torque wrench and socket/extension in there comfortably - in which case this is all a discussion for a time when the engine is dropped for the DMF replacement. What I am going to do before I do the valve adjust is power wash this area and try to remove all the oil stains so it's easier to tell where the oil is actually coming from.

Thank you your opinions are appreciated
90C2
Bill

Cupcar

The seal between the camshaft housing and the cylinder head is metal to metal and sealed with a coat of assembly Loctite 574 at the factory. If it is leaking here a re-torque will probably not solve it but it is worth a try on the 6 nuts.

The seal between the cylinder base and the crankcase is accomplished with an "O" ring that the factory is very careful to tell you that you must not move the cylinder on. If the heads are removed, you are supposed to attach a fixture to the knock bridge to secure the cylinders into the crankcase so they do no move. If they move a leak can develope.

Has your car had the heads off for a reseal of the cylinder heads? If so someone may not have been careful and botched the base "O" ring for you. Just a thought. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

bj

I believe because mine is a 1990 that there is no "O" ring seal between the cylinder and the block. It relies on a surface to surface seal as in the head to camshaft housing (i.e as you explained). I believe your 92 has the "O" ring type seal at the cylinder to block which is more reliable and I've been told can be obtained either by machining the existing cylinders or by new updated cylinders with this "O" ring seal. As far as I know my engine's cylinder heads have never been removed.

Bill
90C2

Fred, Long Island

Any of the moderators available to confirm presence of O rings at cylinder base for the '90 model year?