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MG MGB Technical - Valve cover

Is there a torque spec. on valve cover bolts??? Thanks,Rich O
Rich Osterhout

Rich. Nor torque specification. Tighten them finger tight, then just a little more. If you over tighten the special nuts, the valve cover can deform and leak.

Les
Les Bengtson

Thanks Les.How is everything going? Rich O
Rich Osterhout

I think this depends on the engine. 18V engines have shouldered studs and deep nuts, which tighten down onto the shoulders and so limit how much force can be applied to the cover, that is why they tighten up so suddenly. There is a rubber compression washer under the domed metal cap under the nuts, and it is really only this that applies the pressure to the cover gasket to seal it to the head. Once this hardens with age it applies no pressure, which is why you can get leaks with a new gasket. I also think the cork gaskets aren't as thick as they were. Even glueing the gasket into the cover, and using Hermetite Red between gasket and head and new compression washers I still got some seepage, until I added some shims made out of gasket card to the compression washers.
Paul Hunt 2

If you've got an alloy cover be careful! the new gaskets are thinner, I tightened up the bolts when I had an oil leak, and the rockers started knocking on the cover. I had to superglue a new gasket onto the box and used a sealer on the head side.
c cummins

Rich-
4 Ft-Lbs should do it if, as Paul so rightly points out, the compression washers under the nuts are good. As for today's rocker arm cover gaskets being made a bit on the thin side, yes, not all rocker arm cover gaskets are equal. They differ in both design and in the quality of materials. Irregularities in some cork gaskets can provide a ready path for oil leaks. There is a happy exception: Compare cork-rubber gaskets from Fel-Pro to those of other manufacturers, and you will discover a notable difference in both their grain size and uniformity, the result of Fel-Pro using quality materials and carefully controlled production processes. As a result, the uniform, consistent grain pattern in Fel-Pro gaskets makes for superior leakage resistance. In addition, in order to increase its crush resistance, their cylinder head gasket (Fel-Pro Part # VS21509-1) is reinforced with a binder of Viton, a synthetic rubber-like material that resists temperatures of up to 450° Fahrenheit. I use this gasket and have no seepage stains on my engine, much less a problem with leakage.
Steve S.

Steve,who handles Fel-Pro?Does NAPA,MURRAYS,AUTOZONE?
Rich Osterhout

All engines are the same. Some have studs on the top end of the special nuts, but that is irrelevant.

If the shouldered nuts bottom out, the cover is already collapsed. Even with bad grommets and no gasket, a straight cover will tighten up before the nuts bottom, if all the pieces are present.

The assembly is: cover, grommet. cup washer, 1/8" spacer washer, tube nut. Very common for the grommets to be DOA and the 1/8 spacers missing.

The covers are definitely convex on top if not collapsed. A straight edge from front to back (with a notch for the filler) will contact the cover over the full length of the top. Badly collapsed ones will have a noticeable buckle in the gutter that goes down from the grommet hole, just where the top radius blends into the vertical side.

I've hammered hundreds of these things straight. It's not critical, as there is plenty of take-up available with new grommets, gasket, and all parts in place. Once a cover has been collapsed. it is noticeably weaker than it started, so overtightening straightened ones is not on. Tighten just enough to overcome the friction of the nut in the grommet. Retighten after a bit as the main gasket settles.

FRM
FR Millmore


Has anyone used the silicone valve cover/side cover gaskets that are being advertised (MOSS P/N 296-425)? Are the Pro-Fel cork gaskets available at NAPA/Auto Zone and the other usual retail auto parts outlets?

Dave
Dave Kalp

"A straight edge from front to back (with a notch for the filler) will contact the cover over the full length of the top"

Look at Clausager. Every single cover from 62 to 77 shows a distinct recess for the nut, extended across the cover and down both sides nearly to the flange, but tapering out before it gets there. That's exactly what mine is like, with the two holes and four grooves being symetrical, which isn't something I'd expect to see if the cover were distorted. I submit that the whole point of the shouldered studs and sleeved nuts (of the 18V engines at least) is to prevent overtightening, it's other changes in consumable parts that lead to lack of clamping of the gaskets.
Paul Hunt 2

I have a set of the silicone Valve/side cover gaskets on my car. They work very well, no leaks and they are reusable. I got mine from an outfit called Roadster Gaskets (if I recall correctly). They are not cheap, but I have been using the offcuts to make other gaskets so that makes them more cost effective!

Cheers,
Rich
Rich McKIe

Paul-
Yes, OK, I figured that the exception of the clearly defined recess was obvious. Covers are commonly distorted such that the extreme ends are higher than the center, and the area around the nut recess & hole is pulled down so it makes a sort of dish (instead of the notable convexity) of the area above the recess. It comes of tightening the nuts down until the shoulder makes contact. Frequently people then add washers where the 1/8 spacers go, so that it will tighten against the gasket, but they then screw them down to the shoulder again - that's when the sides buckle.

FRM
FR Millmore

If the question of where to get Fel-Pro gaskets has not been answered, the answer is at any good auto parts store. I have been able to order both the full gasket sets and individual gaskets through my local BAP store. Checker has also been able to provide such service in the past.

Les
Les Bengtson

Mine is square and symetrical, but once the cover nut has taken up all the free play between it and the domed washer it can only be tighted one more turn before it contacts the rocker gear nut, and that gives nowhere near enough pressure on the rubber washers and gasket. Given the material of the rocker cover I can't see it deforming, giving a good seal, but when the nuts are undone there is no spring-back and when refitted with new rubber washers and gasket it then doesn't seal because of distortion/insufficient pressure. Mine *could* have had thicker washers under the cover nut at one time, which *might* have distorted the cover, but *I* didn't remove them, it *was* sealed without being bonded when I got it, but now weeps with new rubber washers and cork gasket, glued into the cover and with Hermetite Red onto the head. Adding gasket card under the domed washers gives more pressure, and does stop the leaks, whereas if the cover were distorted then applying more pressure this way should distort it even more and so make the leaks worse. But then I only have a sample of one. And above all I just can't see why the cover nuts have such a deep cylindrical section if they weren't designed to bottom on the rocker gear nuts and so *prevent* cover distortion through overtightening.
Paul Hunt 2

Paul-
It's times like this that make me crazy about my no-work digital camera!

If you can send a pic of your cover as installed, maybe I can explain this to you. Low angle showing the top and side from the front corner.

The nuts are the depth they are precisely to allow the threads to engage when all parts are in position and new = undamaged, uncollapsed or undistorted; AND, to still allow enough depth in the nut that they will continue to tighten up with sufficient gasket pressure BEFORE bottoming when things have gotten squished - from used up parts OR overtightening in the past.

My sample number is in the several thousand range.

FRM
FR Millmore

I've already posted some at http://www.mgb-stuff.org.uk.rockercover.htm. I'd like to see some pictures from other cars of the head stud without the rocker cover nut and washers fitted, also the cover nut assembled with spacer, cup washer and rubber washer as well as the photo you mention.
Paul Hunt 2

Ooops:

http://www.mgb-stuff.org.uk/rockercover.htm
Paul Hunt 2

Great picture you sent Paul......Thanks,Rich Osterhout
Rich Osterhout

Paul-
That is a badly crushed cover, at least 1/2". Back off a bit so we can see the complete vertical extent of the cover, from fill cap to head surface; the buckles in the side should be apparent. The section between the recess for the fixing and the filler cap should be shaped as the front top peak is, though even that is somewhat bent in the picture.

A well used good cover in my possession, with a correct gasket that has been under compression since 1967, has the top of the rocker arm pillar stud just even with the surface of the cover around the hole edge. New parts will have the stud noticeably just below the surface, with a correct gasket.

In the Magnette manual, there are splendid cross-section drawings (complete engine on two axes) that show it perfectly. The thick spacer is to replace the engine lifting brackets shown in that drawing. I believe these drawings are also in the mga book, but mine has gone missing.

My computer that operates the scanner is dead, sorry. Perhaps somebody with a scanner and an early book get copy it for you.

FRM
FR Millmore

In fact they were the wrong photos, I'd taken some better quality ones but forgotten to upload them. I've also added some general views of the cover:

http://www.mgb-stuff.org.uk/rockercover.htm

I'm certainly not going to try and 'uncrush' this cover as that would almost certainly wreck it, but see if I can find elsewhere and how they shape up.
Paul Hunt 2

Paul-
That's as badly crushed as a cover can be. Your interpretation of "slight" bowing(s) is way past "horrid" to me. You will note that the lateral bow/kink at the lower end of the grooves extends diagonally toward the corners of the cover, and that there is a bow all around the cover just above the flange. Looking at the flat areas for the nameplates, they are supposed to be flat and straight, and at a slight angle to each other, constant over the length. Compare the plane of these near the filler cap to whats happening near the rear stud. The sides of the cover should be dead flat. And the flange itself looks to be bent upward from the excessive pressure at the gasket. I have successfully straightened such covers.

It also appears that the sleeve nuts are flared out at the ends - not sure how that can be, since the only way to do that is to screw them down on an unthreaded section of stud, which you haven't got in this location.

While it has been a very long time since I saw a totally unmolested cover, I recall that as new, with factory bits, the studs were about 1/4" BELOW the cover grommet seat. The whole affair is designed to allow for great variance in gasket (seen them from 1/8 to 3/8 thick) and grommet thickness, some distortion, and always acts as a spring to maintain constant pressure on the gasket.

Bottom line: NEVER tighten until the nut bottoms! The nuts only need to be tightened enough to overcome the friction in the grommets, plus a little. They could and should really be knurled hand nuts.

Note that similar ideas apply to the tappet chest side covers - they are always distorted from overtightening too.

FRM
FR Millmore

The cover nuts have flared out because they have bottomed, I would say, it being the result of being forced against the rocker gear nut, rather than forced over an unthreaded portion. That must have been before my ownership as I'm sure I haven't put that much force on them - reasoning that once they have bottomed, any force beyond a 'locking' force isn't going to add much pressure to the gasket.

As I say on the web page the photos make things look much worse than they actually are. The cover near the flange is square and flat, or it wouldn't seal now. There is a slight bow of about 1/8" on top, and bulges a little more than that at the bottom of each groove. I've been to get some bits today but unfortunately they didn't have any covers for me to look at. However the chappie behind the counter (who also works on the cars) ventured the opinion without any prompting that it was today's cork gaskets that are a large part of the problem! As I say with a couple of thicknesses of gasket card under the cup washers it seals, and as the nuts are bottoming on the rocker gear nuts I won't be able to overtighten it any more! One thing I have already found by only tightening the nuts to the recommended 4 ft lb is that unless you tighten the heater return pipes to *less* than that, or have a very thin spanner, you can't hold the rocker cover nuts still while you tighten/loosen the heater pipe nuts unless you add more spacers under the heater pipe flanges.
Paul Hunt 2

Look at any of the drawings of the cover in any B (or A) series shop manual - the difference between what you have and what it is supposed to look like is about as obvious as the difference between a TR3 and an MGA; 0ne's squashed and ugly, while the other is smooth and nice.

If you had the correct flat washer and spring washer on the heater pipe, that problem would go away too - it's caused by the nut jamming on the thread runout at the bottom of the stud shoulder. I've never had to use a thin wrench on one with the washers, but have had to several times if the washers were missing. Not that there's any point in tightening the heater pipe more than 4 lbft anyhow.

FRM
FR Millmore

The problem is that the heater pipe brackets (rather than flange) are wider than the cover nuts are across the flats, so they would need to be raised up off the cover nut with a spacer that is no more than the width of the cover nut across the flats to get a standard spanner on the cover nut. It's a replacement heater pipe, and the brackets are completely wrong anyway, having a 1/2" hole in them for a 1/4" stud. And maybe that's because they couldn't trust themselves to get the bracket positioning correct!
Paul Hunt 2

I know all that, my point is that if you have the washers on top of the heater pipe bracket, the 1/2" nut won't stick on the 5/16" stud, and you then need no spanner to hold the 5/8" cover nut. If you do, then threads are damaged, which certainly would not surprise me on a car showing such evidence of heavy handedness. All the more if the hole in the pipe bracket is too large.

The heater pipe bracket acts as a friction holder for the cover nut, until the small nut is loose.

FRM
FR Millmore

This thread was discussed between 31/08/2007 and 15/09/2007

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