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panteradave

V12 Cam Lobe Wear?

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I am a relatively new owner of a 1948 Lincoln Continental Coupe and am currently working though some smoking issues with the supposedly newly rebuilt V12.  One thing has led to another and I am now in the midst of complete top-end engine tear down.  I have discovered a number of problems, the most serious being what appears to be wear on the base of the  lifter bodies (where the lifter and cam lobe touch).  A couple of the lifter bodies are wear marked indicating poor rotation within in the lifter bores.  I am concerned about the possibility of resulting wear on the cam lobes. 

 

So, I have systematically measured cam lobe lift with an accurate dial indicator and have cam lobe heights that vary from 0.292" to 0.285" (the valve lift spec for this engine is 0.292").  There does not seem to be any relationship between the locations of the shorter cam lobes and the non-rotating lifter bodies.  My question is - what is the acceptable variation range for cam lobe height?  Is the measured range of 0.007" within tolerance or does the cam need to come out for a regrind?

 

Any advice would be greatly appreciated.

 

Dave

 

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Dave,

          The smoking issue could be the rings are not "seated" in yet. The V12 blocks were said to be a harder cast iron than the 

Ford/ Merc flat heads.

            A new valve lifter body has about.005 crown to help it rotate. It also meets the cam lobe off center , this helps also.

Under sources above , some of these vendors can reface these lifters. On the V12 rebuilds I have done , the only adjust I

did was  a .050- .070  gap between a DRY lifter and the valve stem. Adjust was a slight grind on stem. This was after the 

valve itself was grounded in. The hydraulic design took up any slack with  O   gap. Quiet-- no click.  The cams I used were

hyd. stock grinds , no chips or  discolored lobe faces. On these V12  rebuilds, there are no short cuts!  Good Luck!   Larry 

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Just to add a little more info to a very frustrating experience....

 

As background - I am an experienced mechanic and currently maintain all the mechanicals on my vintage Lola T-342 Formula Ford race car and a couple of other high performance street vehicles.  The race engine currently in the Lola FF is one that I built to the exact specifications of my race class.  I also have the hand tools (including precision micrometers and dial indicators) required to build and QC an engine.  I do all my own mechanical work, other than the machine shop work which I hire out done to my specifications.   Having said that I am clearly a novice with the Lincoln's L-head V12 and I am learning on the fly.

 

At time of purchase, the Lincoln included documentation for an engine-out rebuild of the V12 that was done as part of a gradual but complete body-off restoration that was accomplished over roughly a 15 year period.  The running gear, body, paint, interior, chrome and stainless trim, electrics, etc. are extremely well done. This Lincoln is beautiful.  Unfortunately I've concluded that the engine "rebuild" either didn't really happen at all (in spite of $10k worth of engine rebuild receipts), or the engine was just slapped together by incompetents. 

 

I began the Lincoln engine project with a simple plan to merely replace the intake manifold gasket, but every disassembly step has pushed me in a little deeper.  To list just a few issues, the intake manifold gasket was torn and hanging out the front of the manifold, at least half of the intake manifold bolts were only finger tight, one valve guide retainer was broken off and laying loose in the intake valley allowing one half of the split valve guide to move up and down with the valve, two of the exhaust valve guides were broken in half horizontally (in 4 pieces instead of the normal 2), all 24 lifter bodies are worn flat on the base (absolutely no crown left), 7 or 8 inches of metal wire was found and removed from the water jacket of one head, etc.  Cam lobe height measurements that I made indicate that 5 of the 24 intake and exhaust cam lobes are up to 0.010" too low, suggesting cam lobe wear probably related to the wear patterns present on some of the lifter bodies. The measured variation in cam lift was what sparked my previous question of what is the acceptable range in cam lobe height. 

 

On the plus side, It does appear that all 24 hydraulic lifter inserts are in good shape and hold pressure nicely.  Also, new aluminum pistons were apparently installed, though the cylinder bore has been greatly enlarged to 3.06", vs the stock 292 cu in 2.875" bore.  The condition of the rings and rod and main bearing inserts are unknown at this point.

 

At a minimum the cam now needs to be removed and probably reground.  However, given the identified errors and complete lack of attention to detail in the previous rebuild, I am now questioning the rest of the engine assembly as well.  So the original plan to change out the intake manifold gasket has somehow seems to be morphing into an engine-out total disassembly and likely rebuild of the rebuild.

 

Does anyone know of a reputable Lincoln V12 cam grinder?

 

Thanks in advance for any advice,

 

Dave

 

 
 

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Dave:

Hard to tell what some previous re-builder has done.  I'd think anyone who grinds flathead cams could do the job.  Tell him you if you want to keep hydraulic or convert to solid lifters.  I used Oregon Camshaft in Vancouver, WA.  The hot tip here is to use the 8BA Ford one piece valve guides and valves, retainers, etc.  Much less chance of blow-by, combustion products in the oil, and stink out the vent pipe. 

You can pick up a few HP by using solid, adjustable lifters and a flathead performance grind.  Need to plug  rear oil gallery and drill 1/16 holes in the front gallery and in the front to oil timing gear.  You can adjust out the typical flathead lifter chatter.  Adding a PCV valve helps with vapor control also. 

Abe

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You may have a bored out 1942 or early 1946 block. I do not know of any special design feature to identify these engines. Ford went back to the smaller bore due to problems with thin cylinder walls.

I would recommend a sonic test on the cylinder walls as the first step. If it fails the test, you will have to either sleeve the block back to a standard oversize or find another block. The camshaft in the replacement engine may be in good shape and you will not have to have it ground.

 

https://www.revolvy.com/main/index.php?s=Lincoln-Zephyr V12 engine

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