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MGB MGB Valves

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Dave_W

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I'm in the process of rebuilding my 70 MGB engine. Do I need to do anything special to the valves to deal with the non-leaded gas that we have these days?
 
Dave, welcome to the forum! To answer your question, if the head is stock and has never been rebuilt, then I would send it out and have hard valve seats installed. Your head, if original, has soft seats. Now, lets take it a bit farther and that is if you are not going to make this car a daily driver and just use it part time, you know, weekends and shows, then the original soft seats will probably give you years of trouble free service. JMHO. PJ
 
That's what I was thinking. The head is original, about 70,000 miles, never been off the engine until now. I anticipate about 3-4000 miles a year pleasure driving locally, so not a lot of daily use. I think a simple regrind will do it.

Thanks for the quick reply.
 
Dave, If your going to have the head off anyway, You should check on the extra cost to have new valve seats put in. If you are ever going to sell the car it would make it a little more attractive. Are you going to have the head checked for flattness, or cracks?
BarryE
 
Often times hardened exhasst valve seats were recommend for receeding exhaust valves, while this can happen from years fo running hotter burning unleaded fuel that these heads were never designed to run, the more common problem is poor valve seal. We first discovered this on a race engine, it's pretty common for us to do a leak down test after every race weekend, on fresh prepared race head, running on leaded race gas we started to notice that #2 and # cylinder leak downs were terrible after one weekend, reading as much 25% leakage, after they had been checked at 1-2% leakage before the weekend. At first I thought, well I just lap or cut the valves again, well guess what it happen again after the next race weekend. What was happening is the metal in the exahsut seat area of the head was pitting in the 45 degree seat area, and would do this only after a few hours of operation and valve seal would go out the door. I rebuild alot of MG heads and I often see the pitting on the exhaust valve seat in this area, and I always replace the the exhaust seats with hardened seats. So what we found out thru leak down testing on both street and race heads, is once the metal is compromised by using unleaded fuels, the only fix for extended valve seal is hardened seats. It's not terribly expensive to put exhaust seats in one of these heads, and new vlave, guides and valve spring are pretty cheap for these heads as well, so in short I'd fix it right or do nothing because a vlave job without hardened seats seat IMHO is futile effort.
 
Well now you've got me thinking. I supppose the best would be to get it done if only for peace of mind. I see that Victoria British sells a kit for just over $300 with valves, seats, gaskets, etc. I'll have to check on local machine shops. If I'm going to have them ground anyway, maybe I'd best have them do it all.
 
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