Anyone had a problem due to lack of cam bearings

[TR6oldtimer]

I understand the need to line boring a 6 that has oval or worn cam journals originally bored into the block. I also understand the "good insurance" statements often made when one considers to line bore or not.

I also know that this was originally a 150 hp engine without cam bearings. So has anyone ever experienced a cam failure due to worn journals, or personally known someone who has?

Not to say that I won't bore the cam journals, just wondering.

 

[DrEntropy]

Only TR6 blocks I've come across with cam journal ovality were due to poor maintenance (primarily due to lack of regular interval oil changes).

I'd be for mic-ing what you've got on teardown and proceed as the evidence dictates.

 

[TR6oldtimer]

Only TR6 blocks I've come across with cam journal ovality were due to poor maintenance (primarily due to lack of regular interval oil changes).

<span style="font-weight: bold">I'd be for mic-ing what you've got on teardown </span>and proceed as the evidence dictates.

Yep, was on the list...

 

[TheSearcherMan]

The general line of thinking is this, to the best of my knowledge. The 150 HP cam was longer duration and less lift, to ease valve train stress. The newer design cams, have a higher lift than the original 150 HP cam. I have seen one broken block, cam journal cracked thru, stock cam, maintenance issue as the Dr. said. Not having traditional cam bearings is called, "parent material bearing". I guess when it is all said and done, depends on what cam you are going to use. I have just ordered a 150 HP CP cam, due to an apparent "manufacturing defect" in my present cam, and, that just sucks. You have the original factory testing behind you when you use original design. When you use another design, who's engineering and design do you have? Also, once my investigation is complete, I will post pics showing my present cam, and what is wrong with it, if my suspicions are correct. However, the supplier has already said he is aware of the problem, but offered no resolution. So, we will see.

 

[DrEntropy]

When you stress components past design limits everything along the line is subject to that change. Stronger valve springs for a wilder cam are a big part of that equation in this instance. The more radical cam is being stressed differently, the steel bores of the block will be subject to forces not "designed in" to the original plans. Babbetting would be the wise choice here. Line boring and adding bearings will slow the effects of the different stresses and impact.

 

[tomshobby]

When I purchased our car the fuel pump arm would bind and cause the pump to loosen the mounting stud nuts. I felt the cam bearing surfaces were worn causing the problem. When the engine was torn down there were three badly worn lobes but since the block was to have cam bearings fitted I never checked the bearing surfaces.
There were indications of poor lubrication in several areas.

 

[Brosky]

My engine got new cam bearings as discussed in the past. The shop measured the block and it was marginal as far as the wear from the original cam. Does that mean that the new cam would have been happy in there? I doubt it. Somewhere along the line I would have paid the price for not doing it correctly. You cannot install newly machined parts into worn areas that require a lot of oil pressure/volume and expect them to work out over the long haul.

After reading of the many camshaft issues that seem to have appeared with TR6 engine that did not have cam bearings installed, it made sense to me to do them even though it was an additional $400 in labor.

When I picked a cam, I went with a slightly higher lift, but a longer duration, which to me equates to the same thing (more fuel and air in the engine) but with less strain on the valve train, as Searcher mentions above. I got the matching springs and had them mated to the head with shims and equal heights across the head. That came from the valves all being set in the head at the same height after the valves and seats were ground in properly.

So in the end, as the Doc says, you have to measure the block very carefully to insure that you have a good mating surface for the new cam and that you'll have proper clearance for oil pressure and volume.

For what it's worth, there were NO signs of lack of oil or dirty oil neglect in my engine. Just worn bearing surfaces in the block. The crank and main/rod bearings were fine.

 

[TheSearcherMan]

Brosky, ask your machinist how much he would charge to do it again, I'm curious. Some of us don't have access to the funds, I mean, it has to end somewhere. And I'm not a cheapskate, I have over 30K in my car, and its about to climb thousands higher. 2 years ago, a NOS block was only 350, + freight. If there is any damage to the parent material bearing surface, yes, you got problem. How many people know someone who has had a block failure in a TR6? LOL, the only one I know of is my car, but, it was done before I bought it. You have to put oil in these cars. The engineering is sound. Also, you drive your car more than a taxi, I drive mine maybe 2k a year, at that rate, I will be buried long before I see 50k miles. I am not faulting you for putting them in, just my logic is, well, different.

 

[TR6oldtimer]

The reason I asked the question, is new comers to this hobby (or affliction) when asking about engine re-building are always told to line bore their cam journals. An expense that some cannot easily afford. So the question was presented to separate folklore, or "best engineering" practice, or preference, or "it makes sense to me" from fact or experience.

Knowing that the cam, like the crank, only have the opportunity to touch a bearing is on startup. Once spinning they ride on a wedge of oil, not the bearing surface, apparently to the original builders,it does not matter to the cam what the bearing surface is made of.

So it appears to me, no matter what type of cam or springs you have, if the cam journals are within specs, and in good condition, line boring and installation of cam bearings becomes an option that probably is not needed.

Will I do it? More then likely yes. But then I can afford it, and will not have to explain to a buyer when the car is eventually sold, why I did not.

 

[skikir]

I was planning to install cam bearings. I'm sure my engine was abused and I do drive my car as a second vehicle after my motorcycle and then the truck. My thought was it would help out the oil pressure. The bearings are relatively cheap.

 

[TheSearcherMan]

Whose camshaft you going to use oldtimer?

 

[elysium]

SearcherMAn,
Please check your box for a PM
Elysium

 

[Brosky]

Searcher,

I did ask him that after it was finished and it will never be done again for the price that I paid. He had nearly nine (9) hours of machine time taking .010" per cut on each bearing surface. Once you set up the line boring lathe and start that job, you must finish it, so it's hours of watching a very slow process and moving from journal to journal and back again.

I never said it was for everyone, I only answered what I did and more importantly why I did it. I said to take measurements very carefully to see if the work is needed. Why would someone not do that? If it measures within tolerance, fine, if not, why install a new cam in an area that will ultimately cause it's failure?

And again, I never predicted a block failure, but a worn journal area inside the block that COULD lead to cam failure.

 

[TR3driver]

Seems obvious to me : Check the bores and if they are out of tolerance, either repair them or find another block. The latter option may be more attractive if you're short on funds.

Wonder how hard it would be to build a special-purpose lathe around the engine block, just to line-bore those bearings ? I'll bet it could be done, find a keyed shaft long enough and stiff enough to carry the cutter, then set up bushings outside the block for it to ride in and some way to push it back and forth. ISTR one of the Dave Gingery books shows this method being used to bore the headstock bearings for a "roll yer own" lathe.

 

[TR6oldtimer]

Whose camshaft you going to use oldtimer?

My days of driving all out with the pedal to the metal are past, but I would like a bit more HP then stock, so for now I am not sure. But for sure, nothing real radical and it will be limited by whether I pop to go to triple carbs or not. For now I am just waiting to see how some who are in the process of upgrading their cams turn out.

Wow, 9 hours, that's putting it in the range of $700-800.

 

[RonMacPherson]

Actually find someone who used to line bore the VW air cooled engines, or a truck machine shop. Both should have boring bars that span the block in the 6 engine.

 

[Brosky]

Ray,

I paid $400, but he said, never again.

I really like the TH5 cam from BPNW. Nice idle at 950, great throttle response, great power from low through high RPMS.

If I were doing it over, i would stay with the twin carbs. The triples are great for show, but I'm not really sure how much they bring to the party with all of the other work done, like higher compression, cam, over boring, etc.

I really believe that the monies would be better spent on line boring for cam bearings, reworked distributor, headers, balancing everything and adding a Fidanza aluminum flywheel.

Especially the aluminum flywheel.

Till you get done with everything, triple carbs are very expensive.

But they do look good at shows and garner a great deal of attention and conversations, if you're into that kind of thing..........Oh, and they sound great with the pedal to the metal.

 

[TheSearcherMan]

SearcherMAn,
Please check your box for a PM
Elysium

Ok, let me know if you got my reply and what you think.

 

[TheSearcherMan]

The HP winner will alaways be the one who can get the most air in the cylinders. So, without going to supercharging or Turbo, or Nitrous, the power is in the cylinder head. Porting, polishing, flow testing, larger, or more valves, more lift, more duration, they also get more air in. Air is the key.

 

[DrEntropy]

AKA: "Volumetric Efficiency". :laugh: