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MG MGA - Valve stem seals

I bought some Sealed Power ST2001 seals. Not very satisfied with them. Key concern is that the spring clip is only about 60 thou engaged on the valve guide, not very encouraging. See sketch. It should be longer, there is room. It is also not easy to manipulate into place, either the TFE insert catching on the stem, and the clips too tight for the soft rubber, etc.
Has anyone had better luck with an alternate type, such as FelPro 70373 ?



Art Pearse

Art,

The best thing is to have a groove on guide, to have a snug fit. I experienced Fel-pro on my B-GT, a fine set-up. But for single spring valvetrain, not duals.

JG
Jean Guy Catford

JG, that is exactly my plan. Since I discovered the PO had had the guides knurled, I decided to replace them, so ordered bronze guides. I will cut a small groove at the position of the spring clip. Which FelPro did you use, the SS 70373?
I may also cut a 1/16 off the end of the guide to let the clip seat further down the guide.
Art Pearse

I put bronze guides on the engine I'm rebuilding and fitted the ST2001 seals. I used a short bit of a drinking straw from McD's, split down the length, wrapped around the stem, then lubed with motor oil. The seals slipped on without too much trouble and seemed to seat quite securely on the end of the guides. My guides don't seem to be as tappered at the end as the drawing you posted.



Andy Bounsall

That's interesting Andy. Could it be that mine are in upside down? Or yours? I don't see the need for such a long taper at either end. I will still cut the shallow groove.
Art Pearse

Some valve seal sets are supplied with a thin plastic tube to help slip the parts past the keeper groove. This is especially important for the rubber seals with the small teflon insert ring (seal #3 in attached picture).

If you wanted to fiddle with it you could grind a bit off the top end of the guide to reduce the chamfer, and let the umbrella seal sit a little lower.



Barney Gaylord

Hello Art,

Yes indeed it is SS70373, but I discovered Viton type by Sealed power MV1888C, which could be a better choice.

JG
Jean Guy Catford

Barney, your image shows a valve inserted in the guide, with the chamfered end of the guide pointing towards the valve head. Does this mean that this is the correct way of assembly?
JG, I've ordered 4 MV1888C to have a look! Thanks, Art
Art Pearse

No. It's just a picture intended to show the plastic assembly tool. The official Workshop Manual specifically shows the guide to be assembled with the chamfer on top.

However, it is likely that the chamfer was originally intended to shed oil in conjunction with use of the original shroud (and the small o-ring packing ring for the split cotters). When you toss out the shroud in interest of installing umbrella seals the chamfer becomes a mute point.

Also during porting and polishing a head for improved performance it is common to cut or chamfer or otherwise reduce protrusion of the bottom end of the guide in the air flow ports. As such, I am perfectly happy with intentionally installing the valve guide upside down to have the chamfer on the bottom for better air flow while making the top end more friendly to installation of umbrella seals.

How's that for being two-faced?
Barney Gaylord

My engine guy just installed the Viton seals on my head, says they work very well.
Mark J Michalak

This thread was discussed between 07/04/2009 and 14/04/2009

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