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Old 12-05-2014, 12:33 PM
86911TLCAB 86911TLCAB is offline
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Default BMW e30 Cylinder Head rebuild

So I am taking the plunge and attempting to rebuild a cylinder head. have a couple of questions:

1. Valves--I have 5 bent exhaust valves and 1 bent intake valve. the valves are obviously bent at the head of the valve, but the stems seem ok. when I put a good valve into the same cylinder there is little to no play (equal to the valves that are not bent). i am presuming there isn't an absolute need to change out the valve guides as long as there is no play. True...or false?

2. Some of the videos i have watched show each valves spring/keepers/etc being kept together. Does this make any difference?

3. I have some very slight scoring on one of the camshaft journals (proper terminology). can this be removed with light polishing with 220 or higher sandpaper?

4. The head i was given (thank you Jeff/Hoophead) is really clean and looks great. I will likely take it to a machine shop just to verify it isn't warped and press on to put it back together. Is there a benefit to having it chemically cleaned?

am sure there will be other questions and any assistance is always appreciated.
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  #2  
Old 12-05-2014, 12:37 PM
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I would have the machine shop clean it up do a valve job and then bolt it in and go.
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Old 12-05-2014, 07:29 PM
86911TLCAB 86911TLCAB is offline
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got that...but the fun part for me is learning how to take it apart, have it checked and put it back together..might mess it up, but then thats all about learning how to do it...i am not up for throwing 300 bucks at this only to bolt it back in...

So I have the head completely disassembled and will take it to a machine shop to verify it is not warped...and then need to buy some valves...and put it all back together...

still interested in any thoughts on the valve guides and the light scoring...the journal that is scored, has matching scoring on the race...i have read that some light scoring is not going to hurt anything...suppose the machine shop can help answer that also??

Is this what is referred to as doing the "top end"?

thanks...
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Old 12-05-2014, 08:04 PM
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Chemical cleaning prolly not necessary
Quote:
Originally Posted by 86911TLCAB View Post
got that...but the fun part for me is learning how to take it apart, have it checked and put it back together..might mess it up, but then thats all about learning how to do it...i am not up for throwing 300 bucks at this only to bolt it back in...

So I have the head completely disassembled and will take it to a machine shop to verify it is not warped...and then need to buy some valves...and put it all back together...

still interested in any thoughts on the valve guides and the light scoring...the journal that is scored, has matching scoring on the race...i have read that some light scoring is not going to hurt anything...suppose the machine shop can help answer that also??

Is this what is referred to as doing the "top end"?

thanks...
Light scoring is normal (cold start ups) but bent valves could also be culprit. I suggest having it checked for cracks (don't recall name but 3 cocktails to thee wind). I bent some valves on a 3.2 motor and they hairline cracked 2 of the heads. Lots of good books and interweb articles on do'n the "top end"
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Old 12-05-2014, 08:58 PM
HughA44s HughA44s is offline
 
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Had a timing belt break on a 944 years ago and went through this process. I was told that anytime you replace a valve they need to grind the valve seat to match the new valve which needs to be done to a bear head. On one of the heads I had done the play was acceptable on the intake and only needed to replace the exhaust side guides which were out of spec. It is really a case of having it looked at. Also, I have had issues getting an Al head (and head-gasket) to seal with the block without having it fly-cut even though the head was not warped. At issue is the ability of the head-gasket to compensate for the ripple or waviness of the head surface. I had to pull the head back off and pull the motor, have the block and head surfaced before I could get a good seal. I did a 944 head gasket replacement for a friend of mine's 944 and we had the head fly cut and had good results on the re-install. So I am with CMartin - Take the head to a machine shop and bring home a bolt on ready head. Good luck with this rebuild.
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Old 12-05-2014, 09:23 PM
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Quote:
Originally Posted by HughA44s View Post
Had a timing belt break on a 944 years ago and went through this process. I was told that anytime you replace a valve they need to grind the valve seat to match the new valve which needs to be done to a bear head...
Disagree! on reasonably low mileage engines you don't need to recut the valve seats. Unless doing a 3 angle or performance rebuild.

BUT you do need/should lap your valves so they mate up to the seats anytime you have the head off. And don't forget the have the valve spring tension checked along with 10 dozen other things. More $$$ but my own experience w/Porsche AC engines is the rockers should be replaced so bet BMW has similar weak links Did you get Dempsey's BMW book?
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Old 12-06-2014, 09:30 AM
HughA44s HughA44s is offline
 
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Dave,

Point taken - If I replace the word grind with lap I think we are in agreement. Also, I did a 3-angle on the head each time I had heads rebuilt. Also agree with the valve spring tension check.
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Old 12-06-2014, 11:59 AM
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Cool, and as you obviously know the valve seats are replaceable on most engines. Re cutting every time just means more work in fitting valves and eventually requires them to be replaced ($$$). Overall valve lengths should be check anyway as part of any rebuild and cutting the seat just means more may have to be taken off stem to keep everything in spec.
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  #9  
Old 12-06-2014, 12:33 PM
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Quote:
Originally Posted by 86911TLCAB View Post
So I am taking the plunge and attempting to rebuild a cylinder head. have a couple of questions:

4. The head i was given (thank you Jeff/Hoophead) is really clean and looks great. I will likely take it to a machine shop just to verify it isn't warped and press on to put it back together. Is there a benefit to having it chemically cleaned?

am sure there will be other questions and any assistance is always appreciated.
Tito,

You should have the head both pressure & checked for warpage..

You may want to talk/take it to Pete @ J & F Motors.. 703-671-7757
4064 S. Four Mile Run Drive, Arlington, VA

I have used him for all my BMW machine work as well as some Porsche head work, case cleaning etc.. Just finishing-up 3.5 engine re-furb for and old Racing Dynamics car.. Pete did all the machine work, including the head except the port work.

Paul-
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  #10  
Old 12-06-2014, 12:35 PM
86911TLCAB 86911TLCAB is offline
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All information appreciated....my plan is to take the head to the machine shop and verify it is not warped and the clean up job is sufficient to mate to the engine block.

then will bring it home and lap the valves and put it all back together. Would appreciate anyone who might be willing to look at the final product and make sure i didnt do anything wrong.

I suppose the machine ship can check spring tension, but is there a tool for doing that which is easily available or best to just ask the shop to verify.

getting this far has been quite interesting...after this still have to do the timing belt...so much work ahead.

Just bought a 94 E36 single owner car with 130k on it...something new to play with after this gets done...
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