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Cam shaft areas

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Rick Heighway

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Hey Guy's, this is my first post,hope you can help. I am rebuilding a 73 TR6 engine,I took it to be boiled out, but they said thats old technology and it cost to much to get rid of old chemicals. So they put it through what is called a "steelabrator", small metal balls bombard the block in a cabinet, its clean as a whistle, however the cam riding areas ("journals"?)are no longer polished looking. Should I hone these areas like the cylinder bores,or just use lots of cam lube and let her fly? Everything is within spec so I could hone a little to clean up. How's that for starters?
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Rick--Absolutely you should pay the extra $$ to have the block "bearings" line-bored and honed at the machine shop. This is an often overlooked operation in rebuilds. If you feel rich and are thinking of eventually upgrading to a high-lift cam, bore out to accept the Spitfire cam bearings.

Rick O.
 
Hello, Rick, and welcome to the Forum.

Be VERY sure that all the passages are COMPLETELY free of any material after such a cleaning. My TR3 engine was similarly cleaned without the machine shop's informing the mechanic who was doing the rebuild for me. When I went to start up my beautifully rebuilt engine, several of the little "BB's" had lodged themselves in some of the oil passages. When the oil pressure built up, they were dislodged and seized the main bearings. Luckily, there was minor damage, as RPM were low, but it still called for a complete rebuild. Not something you want to happen!

Mickey
 
OK thanks, but is there any way to clean these oil passages, short of the pressure washing I've done already, and blown out with air hose? Also upon inspection of the cam I notice small flat spots on the longest lobes, I supect where the cam followers contact,is this a major problem or normal wear?
 
I would think that pressure washing and several good blasts from an air hose would take care of any debris that might have been left in there.

As for the cam lobes, some shiny spots might be acceptable, but flat spots sound more serious. If I found them on mine, I'd probably replace the cam.

Mickey
 
I would think that pressure washing and several good blasts from an air hose would take care of any debris that might have been left in there.

As for the cam lobes, some shiny spots might be acceptable, but flat spots sound more serious. If I found them on mine, I'd probably replace the cam.

Mickey
 
Rick--Any material removed from the cam ("flat spot") is not a good indication. Take a look at the matching lifter faces too and see if there is any indentation or scoring. TR6 lifter quality has been a weak spot historically and you may have some of the bad ones. Recommend you consider investing in a reputable set of hardened lifters (from APT or PRI) and having your cam looked at by a machinist. [I just recovered from bad lifter damage that completely wiped 2 lobes on my stock cam. The good thing is it prompted me to upgrade the cam to a warmer variety; the performance improvement has been wonderful.]

Rick O.
 
If you have flat spots on your cam, its a good bet you have some wear on your lifters. If you do, I suggest replacing both, because either can get your valve timing off a little. Oh yeah Welcome aboard.

Cheers,
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Walter
 
Rick had the right idea, but I will restate. The "cleaning process" has badly damaged your cam bearing surfaces. I would strongly suggest that the machine shop is some what liable and should help you with the cost of the line bore and cam bearings. Just my opinion, but I think that the lack of bearings was allways a weak spot, and this beating the block clean has now made this much worse.
MD(mad dog
 
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