Stupid question: Line boring 32V cam bearings
#1
Rennlist Member
Thread Starter
Stupid question: Line boring 32V cam bearings
Hello Gentlemen,
I have a random, stupid question: Is it cost effective (relatively speaking) to line bore the cam bearings on a 32V 928 cylinder head?
I have been paying attention to the threads on how bad cylinder heads are getting in terms of deck erosion from coolant. Take away is great effort is being expended some times to save cylinder heads.
End of 2017, I bought a set of early S3 heads because the deck surfaces were not terribly eroded. Too bad I missed that the engine had suffered oil loss and run dry. The cam bearing surfaces look terrible. Would it be worth even thinking about line boring the cam bearings? I ask because the supply of S3 heads is very finite. I have had the heads for the Red Witch overhauled, but another set of heads is not necessarily a bad thing.
Or, am I full of fecal matter and these early S3 heads are door stops...
Thanks for your time and advice!
I have a random, stupid question: Is it cost effective (relatively speaking) to line bore the cam bearings on a 32V 928 cylinder head?
I have been paying attention to the threads on how bad cylinder heads are getting in terms of deck erosion from coolant. Take away is great effort is being expended some times to save cylinder heads.
End of 2017, I bought a set of early S3 heads because the deck surfaces were not terribly eroded. Too bad I missed that the engine had suffered oil loss and run dry. The cam bearing surfaces look terrible. Would it be worth even thinking about line boring the cam bearings? I ask because the supply of S3 heads is very finite. I have had the heads for the Red Witch overhauled, but another set of heads is not necessarily a bad thing.
Or, am I full of fecal matter and these early S3 heads are door stops...
Thanks for your time and advice!
#2
Drifting
I would not spend the money on them unless it was absolutely necessary - use/save that money for something with a higher priority.
#3
Rennlist Member
Thread Starter
Hello Swaybar, thanks for replying!
I am not actually doing this. Sorry for not wording my question correctly. I should have asked something to the effect of, “Is it reasonable to think I could save these heads by line boring the cam bearings?”
I have the heads, but don’t need them. I already have a bitchin’ set of heads waiting to go back on the short block for the Red Witch. Those cost me enough. I am not spending money on these other heads. I was just curious if they are salvageable or bonafide door stops.
Thanks!
I am not actually doing this. Sorry for not wording my question correctly. I should have asked something to the effect of, “Is it reasonable to think I could save these heads by line boring the cam bearings?”
I have the heads, but don’t need them. I already have a bitchin’ set of heads waiting to go back on the short block for the Red Witch. Those cost me enough. I am not spending money on these other heads. I was just curious if they are salvageable or bonafide door stops.
Thanks!
#4
Hello Swaybar, thanks for replying!
I am not actually doing this. Sorry for not wording my question correctly. I should have asked something to the effect of, “Is it reasonable to think I could save these heads by line boring the cam bearings?”
I have the heads, but don’t need them. I already have a bitchin’ set of heads waiting to go back on the short block for the Red Witch. Those cost me enough. I am not spending money on these other heads. I was just curious if they are salvageable or bonafide door stops.
Thanks!
I am not actually doing this. Sorry for not wording my question correctly. I should have asked something to the effect of, “Is it reasonable to think I could save these heads by line boring the cam bearings?”
I have the heads, but don’t need them. I already have a bitchin’ set of heads waiting to go back on the short block for the Red Witch. Those cost me enough. I am not spending money on these other heads. I was just curious if they are salvageable or bonafide door stops.
Thanks!
#5
Drifting
#7
Rennlist
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If you get "hurting" for room....strip the heads. Save the valves, since they are NLA and valuable. Save the lower spring seats, the shims, the retainers, the keepers, and the springs.
Recycle the aluminum head....it's junk.
Recycle the aluminum head....it's junk.
__________________
greg brown
714 879 9072
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
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#8
Rennlist Member
Thread Starter
S3 cylinder heads in question are here in this thread, starting at Post #42, going to Post #52.
https://rennlist.com/forums/928-foru...e-heads-3.html
https://rennlist.com/forums/928-foru...e-heads-3.html
#9
Banned
Hmm, maybe someone needs to make the heads as well as the block as well.
As to your question of boring, most well equipped automotive machine shops that have Rottler cam boring machines can do them, but the question is what do you do with an overbore cam journal afterwards. There's no provision in the 928 world to accommodate this since the cams don't use bearing inserts. Now you're talking custom cams or bearing inserts.....not worth it on that motor.
As to your question of boring, most well equipped automotive machine shops that have Rottler cam boring machines can do them, but the question is what do you do with an overbore cam journal afterwards. There's no provision in the 928 world to accommodate this since the cams don't use bearing inserts. Now you're talking custom cams or bearing inserts.....not worth it on that motor.
#11
Rennlist Member
Thread Starter
Catorce, thanks. However, I am a gearhead and not a machinist, so work with me. I should have said 'align boring' instead of 'line boring.' I am envisioning what is done when align boring main caps for the crankshaft on an engine. The faces of the caps are machined, then the caps are bolted and torqued down. The main bearing bores are no longer round. The boring bar then makes them perfectly round again. Granted, the centerline of the crankshaft is now moved X number of thousandths of an inch up into the crankcase. In the case of the S3 cylinder heads, I would think it would be possible to machine the cam bearings to the proper surface finish as they were. The slight movement of the cam shaft centerlines down into the head could be dealt with by the chain tensioners and the belt tensioner. I think.
Strosek Ultra, Thank You! That is pretty much what I had in mind.
Strosek Ultra, Thank You! That is pretty much what I had in mind.
#12
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#13
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Thanks for all of your advice on this issue that may never get taken care of. It is good to know, though!
#14
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I’d never thought about it until my local head guy schooled me a bit.