A Tale of Two Gasket Sets

MGB timing gear

Timing chain master linked marked @ 12 o'clock position with a dab of white paint.

When I’m putting an engine together I always snap a picture of the completed timing gear assembly so that I know tab washers have been bent, the tensioner slipper has been released against the chain and that the crankshaft oil slinger is on the right way around.  This one is, but a lot of the time they aren’t, much to their detriment, it chews ’em right up !   No one should make this mistake, it has an “F” on it as in “FRONT”.

Similarly, as components such as main bearing caps and connecting rods are final torqued they get a checkmark with a Sharpie Marker and I take another picture to document this for my piece of mind as well.

Timing chain & tensioner

Timing chain with master link & tensioner

Much of the british engine component aftermarket is now controlled by Federal Mogul, the same people who also bring you Champion Spark Plugs, and both the venerable gasket manufacturer Payen and maker of pistons, valves & bearings, AE, are part of the combine.

This is great news because it means that these components are still in good supply and they’re generally quite well made, but there are a few exceptions.

One of the more notable ones is right here because the Payen lower end (a.k.a. “conversion”) gasket sets for MGB are now made from a single sheet of gasket paper where you the craftsman now get to punch the gaskets out.

Two Payen gasket sets

N.O.S. FK669 full gasket set left, & "modern" EG411 conversion set, right

When we’re dialing in the cam timing on a new engine we like to use a timing chain with a master link as illustrated above.  It has a huge advantage for us because we can strip the chain off the sprockets to make a timing change without needing to break down our measuring gear on each trial.  This saves us time and you money.

The problem has been that the .035″ gasket sheet, while just right for pan gaskets,  far exceeds to original combined thickness of the front bearer plate & tensioner gaskets of .025″ (Remember the new combination adds up to .070″ of total thickness) with the result that the back of the master link hits the plate just visible under the tensioner slipper in the 2nd photo.

3 & 5 main oil pump gaskets

3 & 5 main bearing engine oil pump gaskets

We compensate by cuting a new .010″ tensioner gasket from bulk gasket paper.  The new, new wrinkle we’ve begun to encounter is  we’re now finding that in additon to shimming the crank sprocket for parallel alignment with the cam sprocket, we’re also shimming the cam sprocket for clearance over the camshaft thrust plate… or undercutting the plate.

A last point of commentary here is that for reasons we have never been able to fathom, the Payen 5 main bearing gasket sets have always included  a redundant 3 main bearing oil pump gasket, a situation which appears to have finally caught the attention of Qualiddy Control.  No longer do you get two, but the one you do get is the wrong one, and I can tell you from sad experience that a five main oil pump will not pump when seated on a three main oil pump gasket.

Caveat Emptor to all of you who have recently experienced, or are about to,  difficult MGB engine rebuilds.


The component pictures were taken on our cast iron surface table, which was hand scraped to a tolerance of plus or minus .0002″ (two ten-thousandths  of an inch) at the old Cone Blanchard Plant in Windsor, Vermont.

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