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MG TD TF 1500 - valve guides & magnafluxing

Should valve guides be removed before having a head magnafluxed?
Geoffrey M Baker

No.

Tom Lange
t lange

I should add that I have removed the valves and rockers and apart from a lot of coke, everything looks good. I'm thinking that the head just needs cleaning and reassembling, no other work needed.
Geoffrey M Baker

Magnetic particle testing the head is a bit overkill (and I certified American Society for NonDestructive Testing Leve lll). About the only place I'd worry about crack would be between each valve pair, and you can see that well enough with a flashlight.

I'd focus on that suspect valve guide. Slip another valve in it and all the others to compare how free the valve slides. If they were replaced 3000 miles ago, they ought to be go to go, but that one might stand a reamer. The ends can crush in a touch on installation and it may have needed reaming or chamfering way back when.

Make sure that small hole in the top banjo bolt isn't plugging up and choking off lubrication to the rocker shaft and hence, valves.

If the valves were ground 3000 miles ago, they should be go to go.

What I often do, is slip the valves in with a dab of valve grinding compound, attach an electric drill to the stem and spin it for a few seconds on the seat. Brightens and cleans both surfaces nicely. You always see this done with a suction cup on a stick, but ever since I was a kick, I was too lazy and used an electric drill.

If you don't have grinding compound, a light abrasive cleanser will do in a pinch, but wash it off thoroughly so you don't have chlorine sitting between the seats for a while. You don't want crevice corrosion blemishing your new mating surfaces.
JRN JIM

Chuck Schmidt agrees with lapping valves in (from your other post)...
"I always compound the valves in and look at the pattern on the contact surface, which will show up most seating problems."
JRN JIM

Jim, there are no suspect guide valves. Everything looks excellent, apart from plenty of carbonization. I plan on doing as you say, and the electric drill sounds good to me too :)
Geoffrey M Baker

Sorry Geof, I keep mixing your rebuild up with the burned valve problem in another thread. When you started talking valve guides....
JRN JIM

This thread was discussed on 24/03/2015

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