machining 3.5 cylinderhead, need professional advise

[werminghausen]

I have found one potential machine shop in Oman for renovation of my cylinder heads. 2 intake guides are loose. These were the original guides.
Now the shop want me to order the repair guides, they don't want to do this. Oh well now the risk is on me...

Question for the ones who know:
Would you use the first oversize for ALL valve guides 116 050 36 24 (intake OD= 14.042-14.050mm)
and 116 050 41 24 (exhaust OD= 15.042-15.050mm )

Or would you say for the 2 loose ones (the loose intake guide measures 13.95-13.98mm ) I'd need the repair stage 2 ...116 050 49 24 with OD = 14.20mm...meaning I'd have a mix of different intake valves?

What about the valve seat: are they typically okay and the old ones can be cut or is there a chance that they need to be replaced?

I want to have the heads planed and pressure tested. Is there a test to see if the job has been done correctly?

What is the most important points I'd need to find out if the shop is okay or not?


Happy New Year , Martin

[Mike D]

It's tough to answer all your questions without being able to actually see the heads. I'll give it a go with some generic answers. I am not an expert on the 3.5 engines but hopefully some one with more experience on those engines will chime in.

#1. Need to measure the guide sockets of the two loose guides to determine which size you'll need. If the remainder of the guides are tight no need to go larger than standard replacement.

#2. You wouldn't have a different mix of guides where it counts, internally. Normal to replace only the bad guides which can lead to having a mix of different sizes (i.e. "oversize") in the head. Has no effect on the engine.

#3. The seats are pretty robust but without seeing them there's no way to tell.

#4. Do NOT have the heads surfaced unless absolutely needed. Most shops automatically shave the heads because it's easier and cheaper for them to do it than to take the time to strip and clean them. Reducing the thickness of the heads results in higher compression and engine temperatures. Seems to me you've got enough troubles with engines overheating, yes?

#5. As with any place of business, go talk to people who have had work done at the shop.

[werminghausen]

Originally Posted by Mike D

It's tough to answer all your questions without being able to actually see the heads. I'll give it a go with some generic answers. I am not an expert on the 3.5 engines but hopefully some one with more experience on those engines will chime in.

#1. Need to measure the guide sockets of the two loose guides to determine which size you'll need. If the remainder of the guides are tight no need to go larger than standard replacement.

#2. You wouldn't have a different mix of guides where it counts, internally. Normal to replace only the bad guides which can lead to having a mix of different sizes (i.e. "oversize") in the head. Has no effect on the engine.

#3. The seats are pretty robust but without seeing them there's no way to tell.

#4. Do NOT have the heads surfaced unless absolutely needed. Most shops automatically shave the heads because it's easier and cheaper for them to do it than to take the time to strip and clean them. Reducing the thickness of the heads results in higher compression and engine temperatures. Seems to me you've got enough troubles with engines overheating, yes?

#5. As with any place of business, go talk to people who have had work done at the shop.

Thanks Mike,
Very helpful comments. So you are saying use standard repair guides and do only the loose ones with oversize guides.
Would you recommend a pressure test? How about the valve seats?
Martin

[Tony H]

I am on the verge of having some 3.5 heads rebuilt for my project (this would apply to any head) and I know all the guides need to be replaced so I am looking at some of the same questions. Is there a downside to just installing all oversize guides? I think the amount of pressure needed to press out the old guide partially determines if OS guides are needed. My car will never be driven enough to require the guides to be replaced again so I'm not concerned about that.
FYI I think the seats pretty much last forever as long as they are not messed up by an incompetent machine shop.

[Mike D]

No real downside to having all the guides bored out to accept 1st oversize. The extra cost is a consideration and of course should you ever need to replace a guide in the future you would probably have to go to 2nd oversize. Are you going to repeat the process?

[werminghausen]

Originally Posted by Mike D

No real downside to having all the guides bored out to accept 1st oversize. The extra cost is a consideration and of course should you ever need to replace a guide in the future you would probably have to go to 2nd oversize. Are you going to repeat the process?

I was ordering now 2 sets of repair guides 116 050 01 67 (rel. cheap) plus
- 2x 116 050 37 24 (oversize guides for replacing the 2 loose intake guide) this number was replaced by 116 050 4924+A110 053 02 58

I agree with the information that the valve seats should be fine.

Would someone recommend a pressure test. ..or any other test to make sure the heads are find and ready to go.
Martin

[werminghausen]

Originally Posted by Tony H

I am on the verge of having some 3.5 heads rebuilt for my project (this would apply to any head) and I know all the guides need to be replaced so I am looking at some of the same questions. Is there a downside to just installing all oversize guides? I think the amount of pressure needed to press out the old guide partially determines if OS guides are needed. My car will never be driven enough to require the guides to be replaced again so I'm not concerned about that.
FYI I think the seats pretty much last forever as long as they are not messed up by an incompetent machine shop.

Thanks Tony