I have a bent intake valve on the last cylinder( original straight 6 engine) by the cab. I have it out and am waiting for the new one to come in the mail. before I put the new one in do I need to use a grinding compound on the seat, so that the new valve matches and seals properly. The old valve was only barely noticeably bent when I took it out. the seat area looks very good. I am putting in new springs & guides. 2nd question is there anything else I should be aware of when changing this out.

Any help would be greatly appreciated.

thanks Jagstein

 

Considering the amount of work required just to get to the valve, I would replace the guide as well; just to be safe. Lapping the valves is a good practice, as it creates a perfect seal right off the bat, but it isn't completely necessary for the single valve. Just make sure the guide isn't damaged from the bent valve before going through the trouble of reassembly.

Good luck and post up some pics!

 

As I remember when this happened to me the mechanic who did the job at my house did use a bit of fine paste on the new valve, just to clean up the valve seat, basically. He also checked seal using a bit of white spirit. All was OK after that.

How did you manage to bend the valve in the first place, over-revving ?

 

I think it is due to a misfire/backfire or sitting too long. due to below.
my father had the engine rebuilt,car painted and new interior and gave it to my sister. she put about 10k miles on it then a power steering line went out and she let it sit for about two years. I went and got it for myself replaced the hose and started it, but it sat so long that the head bolts rusted all the way through and water was coming out through the holes at the top of the head . after some drilling and easy outing to replace head bolts, I had trouble starting it again until I got air and fuel injection mixture right.

 

Hi Jagstein

I am pretty sure it was the car standing for two years. In my case I did a head job, and new head gasket, which then promptly blew again, and a chap in the Jag Club told me it would be no good until I had cured the cracks between the bores. So he sold me an uncracked block following which I took engine out and rebuilt it around the new block. I never touched the head because I had just redone it. I then decided to refurbish the car bodywise, so this took about 3 years off the road. I got the bent valve when I restarted the engine, and I assume this was because all the oil in the valve guide had disappeared over the years. I could have cried, I can tell you. Wife could see I was so upset, so she persuaded me to call the chap who sold me the block to come to Crewe to fix it which he did and took about 4 hours in all. (with an assistant). No problems after that.
I think the Series 3 engines are more prone to this because they have bigger inlet valves which are closer to the piston when they are open, so it only takes a lazy valve for the piston to clout it once and its head off time again !! For what its worth, I don't think you need change the valve guide - I didn't and the engine was a 1980 and valve job was done in 1995. Worth checking it out, though.