Valve guide damage

[Andrew]

I think I f---ed up. While lapping the valves in my head, I managed to pull a burred valve through one of the guides. (actually I tapped through with a screwdriver and hammer because it was stuck)- dumb move I know but its done. Now I have a valve guide with a staight full length scratch that looks about as wide as if it had been done with a sheetrock knife. The seals are new. What should I do???

 

[daredevil]

have a machine shop knurl it and ream it back to size or install a new guide. A straight groove will leak oil down the stem. Not worth a gamble with the head already off. jmo buckneccid may be right but i,m not a gambler.

 

[69HEMICORONETR/TCONV]

Install a new guide, ...the engine already down, ...it's not worth the risk.

 

[Andrew]

Is there any risk in installing new guides in aluminum heads? Is there any benefit in installing oversized valves instead?

 

[69HEMICORONETR/TCONV]

Is there any risk in installing new guides in aluminum heads? Is there any benefit in installing oversized valves instead?

A good Machine Shop should be able to handle this task easily, and a good Machine will have plenty of experience in doing so,

What size valves are you running ? and what Head are you running them in ? ,

I know you really didn't want to hear the news on the valve guide, but it's what I would do if it were mine, ...it's always better to be Safe, than Sorry..........plus I would be pissed if I had to tear it back down to do what I should have done the first time.

 

[Andrew]

The heads are Edlebrock RPM Performer and the valves I believe are 2.14 and 1.81. They are about 10 years old, but don't show much wear. I checked the guides again and the one I mentioned is the worst but there are at least 2 others that I scratched. I am going to take your advice and bring it to a machine shop to have any damaged guides replaced.

When I asked about oversized valves, I meant oversized stems. I have heard that I could have the guide bored and buy a new valve to match. I don't know which is the preferred method, but I will do whichever is better.

Thanks.

 

[Meep-Meep]

I wouldn't worry about a little scratch especially if you have the PC seals, but a big gouge might cause problems in the long run. What's the stem to guide clearance? You might be too loose there and have to replace them anyway. I don't like knurling guides because it cuts about 50% of the surface area out of the guide. You will need to do a valve job after the guides are replaced.

 

[Andrew]

Decided to take them in for honing and valve job. should I re-lap when I get them back?

 

[Meep-Meep]

Depends on your head guy. If the surface finish is shiny and smooth then should be fine as is. I have nothing against lapping, but if you don't need to......

Most shops will vacuum check the port with the valve in - no spring - to make sure it doesn't pass too much air past the seat or through the guide. The slower the rate of rise (longer it holds vacuum without pumping on it) the better the seal.

 

[scotts74birds]

If you really feel the need to lap them, then a little machinists blue dye, and a light, quick spin with just a TAD of FINE lapping compound should tell you all you need to know. The slightest flaw will stand out like dogs-balls. All the old-timers I've met do it by hand with the stick with two suction cups on it. I'd be afraid of using a drill, things could go tits-up very quickly.

 

[69HEMICORONETR/TCONV]

If you really feel the need to lap them, then a little machinists blue dye, and a light, quick spin with just a TAD of FINE lapping compound should tell you all you need to know. The slightest flaw will stand out like dogs-balls. All the old-timers I've met do it by hand with the stick with two suction cups on it. I'd be afraid of using a drill, things could go tits-up very quickly.

I'm not a fan of the drill method either, you can remove too much too quick,.......not good.

 

[Andrew]

Yeah thats what got me in trouble the first time around. Lesson learned.

 

[69HEMICORONETR/TCONV]

Yeah thats what got me in trouble the first time around. Lesson learned.

Chalk it up as a lesson learned,... It's water under the bridge now, ...Just never forget it,............Experience has been a Teacher at the school of Hard Knocks to a lot of us older Guys, and some times she's been a Bitch. :grin: