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Triumph TR6 - Could use some advice on examining my stock cam


I'm in the process of rebuilding the engine in my 73 TR6. I'm trying to deterimine if I can use my original cam as is. By eye, the cam looks very good. No scores or scratches just nice and shiney. The lifters look nice as well. They look to be very flat on the lobe rubbing surfaces with no scoring. One lifter however has some pretty bad Pitting on the lobe rubbing surface. The lobe that the pitted lifter rides on looks fine. I numbered all of the lifters indicating where they go back in.

I'm basically restoring the engine. The car is a "top down" weekend cruiser. I'm not looking for any extra performance.

I would rather not spend the money on a new cam if I don't have to. It appears that both reconditioned and new cams are expensive

Niether the Hanes or Bently manuals have any info on checking the cam for wear. So, I guess I can mic. the lobes and see if they are all approximately the same.

If I can determine that the cam is okay I might buy a full set of new lifters. At minimum I could just replace the pitted lifter and be done with it.

I did search the archives and didn't find much about this subject with the stock cam.

Any help is appreciated.

Thanks
Henry
HP Henry Patterson

I would be very suspicious of the lobe that had the bad lifter...check it carefully with a mic and a magnifying glass...if you've made it this far then I would put a little better cam in it anyway and make sure that you get good hardened lifters....try Ken Gilanders at BFE or Richard Good...you may also want to put cam bearings in the block...good luck...Chip
Chip Collingwood

Try the flotation test: take all the parts you suspect might not be good and throw them into a deep body of water such as a lake. The parts that float are good to reuse!

Seriously, it could end up costing you more in the long run; at least get it measured with a micrometer and tested for hardness by a cam expert.

(The test I described is not my own invention, it was taken from a book by Carroll Smith, "Prepare to Win".)
Simon. WOFTAM Racing.
Simon Rasmussen


Yeah I know. Like every thing else I do I look for the least costly way first and then end up shelling out the cash.

I'm going to mic it myself and if it looks good I'm still going to take to the engine shop that did my block and crank work and let them make the call. Among other things they also make cams for auto industry prototypes and race engines. I'll trust what they tell me.

Thanks,
HP
HP Henry Patterson

You'd need to mic the lift on each lobe. IMHO, it isn't worth it. That shop can regrind it and maybe get you a bit hotter cam since smog isn't an issue for a '73 - at least it isn't in California.

Tim
Tim Brand


I'm now leaning toward just sucking it up and paying out the money for a new cam and lifters. The cost of regrinding and hardening of the old one approaches the cost of a new one. The "flotation test" is probably right on!

Do I need to replace the push rod's too?

I assume when I put the new cam in I will use engine assembly lube (same stuff I used on main and rod bearings) on the cam bearing surfaces and then use that cam lube grease on the lobes and bottom of the lifters. apparently the cam lube has some properties specific to seating in the lobes and lifters. If I have that wrong please let me know.

Thanks
Henry
HP Henry Patterson

Your pushrods are probably ok, but if your grinding the head (to raise compression), you may need shorter ones. Your rocker arms and the shaft are likely shot and need replacement by the way. What kind of valve guides are they installing - bronze?

You're right about the cam lube. You can just slobber it all over the cam journals and lobes - you don't need to use assy. lube.

When you open up a motor, you really do open up a can of worms - pardon the pun!


Tim
Tim Brand


Thanks Tim,

I had the engine shop look over the head and they confirmed what I thought. It had been rebuilt not too long ago. All of the valve components are fine.

As far as the rockers I still have to give them a look.

The reason I decided to do the rebuild was because of very low oil pressure. Other than that the engine ran fine...no oil burning etc.. From there it just "snowballed".

At first I thought I might just drop the pan and replace the rod bearings. But I found the original bearings worn into the copper with grooves on both the bearing and crank pins. So, once the engine cam out and the engine shop got it...well you know. They let me know everything that should be done since the engine is apart.

I continue on....

Henry
HP Henry Patterson

Henry--Put the cam back in and worry no longer. I would, however, seriously consider new HARDENED lifters (about $100 from APRt or PRI) ) as they are more important than the cam itself. If you go that route, be sure to observe the proper bedding-in procedure when you start up (2500 rpm for 20 minutes ONLY).

Rick O.
'72 TR6
Rick Orthen



Rick,

Upon closer inspection (measuring) I found the lobe that the pitted lifter runs on is .015" shorter than all the others. The lobe also has some pitting on the tip. I'm not too experienced with cams so I'm not sure what I can get away with. I'm afraid that the pitting on the now shorter lobe will grind into the new lifter. What do you think?

As far as the bedding in procedure, Is it true that I need a special cam lube rather than using the same engine assembly lube that I used on the main and rod bearings? I had heard somewhere that the cam lube has some material that helps bed in the lifters.

Thanks,
Henry

HP Henry Patterson

Henry you have pretty much answered all of your own ?'s...you need to replace the cam!!!...either upgrade to a better grid or go stock and replace the lifters(hardened)...that bad cam lobe will wear out any new lifter in no time and the cam will wear out as well...and where do you think all that metal is going anyway?...I can tell you that it isn't all caught by the filter...do the right thing and stop the bleeding before it gets worse...if you need any help or advise please send an email
Chip Collingwood

Henry--If you are going with a new cam, seriously consider the Isky Z-19. It's a drop in mild performance cam that I installed. Very nice, and the price is not much more than a stocker. As others have said, if you shave the head, you really should get shortened pushrods. And bed the whole thing in properly (see the Isky website for the procedure).

Rick
Rick Orthen


Thanks all,

I bought a new cam and lifters today from BP Northwest. (before I read your recent posts) It should be shipped soon. I still have time.....remember I'm in Michigan. I also had time to over anylize this thing as I always do.

I didn't shave the head. There was no problem with leaks or anything head related. I have the more expensive "Payen" head gasket so it should seal up nicely.

I'm not going for any extra performane with this build. I'm just restoring it. Although the .030 bore I had to go to may give me a little extra "oomph" anyway.

Henry
HP Henry Patterson

This thread was discussed between 27/01/2005 and 01/02/2005

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