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MG TD TF 1500 - Valve wear question 51TD

I'm finishing up degreasing and cleaning the valves and springs. I noticed a couple of things. It looks to me like the #2 valve (exhaust) is newer than the rest, it has a much thicker head, suggesting less wear. Is there a minimum thickness to the head on the edge at which point it is recommended to replace the valve? The picture shows #2 on the left and #3 on the right, both exhaust valves.

Geoffrey M Baker

The thicker the better; when that thin, I would recommend replacing them. At $10 each, it's cheap insurance. Have your valve springs tested also, and replace them with the 125# springs if they are off.

Tom Lange
MGT Repair
t lange

Tom, I appreciate your suggestion and you are undoubtedly correct.
However, I'm focusing my time and money on the camshaft, cam bearings, piston rings, conrod bearings, main bearings and whatever else (including, very likely, a new camshaft and tappets) is wrong down below... including of course the cost of cleaning and measuring it all...

My budget may not include anything but a decoking of the head right now.
But rest assured, once this is all back together, if I haven't had the money for a new set of valves and springs... it will be the very next item on my checklist, and I will get to it within a year...
Geoffrey M Baker

One dropped or broken valve can do many thousands of dollars in damage, not a place to scrimp. If truly can't afford now, wait until you can before you crank it up. George
George Butz

I wonder if that valve on the left is ground on a 45 degree angle like most.
The valve on the right appears to be cut shallower, 30 degrees, as our engines call for.
You might study it closer or have your machinist look at it. He can cut it to 30 easily. There's plenty of meat.
JRN JIM

Jim - not apropos Geoffrey's situation, but I do my three-angle valves at 15-30-45 degrees, and have found that they seem to flow better.

I reiterate what I said above, I would recommend replacing a thin valve like that (those?). To paraphrase George, a dropped valve can ruin your whole day. Imagine ruining a piston, a valve, a cylinder head and an engine block - all at the same time, with one dropped valve head rattling around in the engine, before you can stop the thing....

Don't be penny wise and pound foolish.

Tom Lange
MGT Repair
t lange

OK, I promise - new valves before the engine starts...
Geoffrey M Baker

The reason I am so adamant is that I was in the same place as you many years ago in College, and scrimped on valves during a TF1500 rebuild. I lost a valve head in less than 2,000 miles going 65 on the highway, and ruined the head and the piston before I got it shut down.

You may go 30,000 miles with thin valves, or you may go 500 - it's completely up to the fates. But this forum is filled with "collective wisdom" based on many years of personal experience, so I tend to listen when someone suggests something...

Tom Lange
t lange

I'm listening :)
That's what I love about this forum: my complete knowledge of MGs derives from my experience with this one 51 MGTD. It's great to get input from people like you, Tom, who have worked on many!
Geoffrey M Baker

Make sure you know the sizes before ordering. You probably have the older/smaller 31/33 set, but doublecheck to save a lot of aggravation later returning the wrong ones.

New valves are a thing of beauty! I went so far as to polish these to near mirror finish to attenuate carbon buildup since these will work with a supercharger. High temps and hot spots can lead to detonation, which must be avoided at all costs (just short of spending extra for premium).

JRN JIM

This thread was discussed between 25/03/2015 and 27/03/2015

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