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Triumph TR6 - Cam R&R
|This winter's project will be replacement of my cam that has a severely worn #12 lobe and/or lifter (hardly any valve lift; push rod is OK). I've read that this procedure can be carried out with the engine in the car after removing the valence grill. I don't want to pull the engine!|
I'd like to hear your experience doing this.
|Rick-The cam can be removed without removing the engine by removing the grill, radiator, and cross tube. I think the motor mounts had to be unbolted and the engine raised to get the cam through the grill opening. The lifters will not go through the opening in the head. Either the head has to be removed or resort to plan B which involves removing the pan, pushing the lifters up high enough to clear the cam lobes and holding them in place with grease or by slightly "cocking" them in the bores. Another way to hold them in place is use wooden sticks that are a tight fit in the lifter bores and use clothes pins to hold the the sticks. After the mechanical fuel pump is removed (if fitted) the old cam can be withdrawn, the old lifters removed from the bottom, the new lifters inserted, then the new cam. It seems like the lifter opening in the head could be enlarged enough for the lifters to pass through without causing any problems.|
|Berry--I like your idea with the sticks. I'd much rather remove the pan than all the stuff that has to go with the head. Thanks for the suggestion. According to Bentley, only the driver's side engine mount needs to be loosened. With the pan removed, what do you use as the lift point for the engine? The perimeter of the block where the pan attaches?|
|Rick-The engine was lifted near the front on the pan rails with a block of would and a bottle jack, an overhead crane or cherry picker would even be better. Also, the dist. has to be removed.|
|I don't think that using the block sealing surfaces as a lifting point is a good idea. The blocks are not necessarily all that strong in that area, the oil pan adds quite a bit of stiffness and then there is that whole sealing surface bit.|
I would suggest the use of an engine hoist and the lifting eyes, then reattaching the engine mount so you can get the hoist out of the way. Do the rest of what you need to do prior to cam installation, then go back to the hoist when installing the cam. You will want to run a couple of longish bolts into the cam to assist in the installation. It's not that bad until you get to that last journal, then you will be glad that you have a "handle" on it.
As for the stick and pin approach, can't say that I have ever used it. I have only done TRs with the head off and on BMC engines, you can get to the lifters by removing the access covers on the side of the block. Sound like a pretty neat trick if you will not have the head off for some other reason.
|Hi Rick, Dave Johnston here, Seattle, '75TR6,. I've been staring at my #12 Rocker with the same faults/symptoms that you have described. (Pushrod is also straight) I lent my dial indicator to a friend and as soon as I get it back will measure actual amount of valve lift on #12 and compare it to a few other exhausts. Have you done this with your #12 ? |
A general question to all -- Is this a "problem spot" on the TR6 generally ?
And why ? I'll share what I find, I'm removing the head in the next week or so also.
|David--Misery loves company! I haven't measured the lack of lift because it is so visually obvious to me that the movement isn't there. I can see no reason why this would be purposeful design, but am puzzled why just the #12 exhaust is affected. Let me know what your lift measurements are. I don't even want to speculate what would happen should the lift go to zero with the engine running (bent/snapped conrod comes to mind).|
|There is no design difference on lobe lift by the books anyway RickO?|
Not something I have seen yet David as far as common?
But would realy like to know your findings front to back while your there?
Do you guys have the upper lube line mod.?
|Bill--Yup, I have the aux oil line to the rocker shaft, but have observed plenty of oiling on all of the rockers. Think there is some oil starvation going on in the rear?|
No longer worried about zero lift as I had a 'momemtary lapse of reason' thinking that a burnt air/fuel mix is incompressible! Whew.
|Rick - Why the #6 exhaust valve ? Well, it gets hotter that the intakes and #6 gets hotter that any of the others, being at the rear of the engine. By the time the coolant gets there, it's already hot.|
Is it possible that it's not the cam but the cam follower that rides on the cam and lifts the pushrod that gives you "zero lift" ? There were a batch of cam followers that came in "not heat-treated" and they wear out pre-maturely because they are so soft.
Don Elliott, 1958 TR3A
|Rick-I think the cam lobes are lubricated through the magic of splash&mist-oil being thrown around by the crank and rods. The oil from the rockers runs down the pushrods but doesn't contact the cam. |
|Don--Your cooling explanation makes sense, but I don't know that it would increase wear on #12 since that region is oil cooled. I already thought about a worn lifter, but that shouldn't matter since I've got the spec valve tip/rocker clearance. Also, why just #12? Remember, I'm getting some valve lift, just not much. A worn lifter would only affect rocker geometry in my mind. Somehow the eccentricity of the #12 lobe has been severly diminished.|
Anyhow, I'm gearing-up to replace the cam with an Isky Z-19 regrind to bump lift up to around 0.400 inches and will install nitrided lifters. Will pull the head instead of the pan since others have encouraged me to shave the head a bit for CR. May also use 1:1.55 roller rockers if I keep reading about Brent's setup! The shopping list just keeps getting larger.
|Hi again Rick , and Bill - some results--|
Measured rockers 1-11 at an average of .406". #12 measured at .261" or only 65% of average.
(Hi-.418" - low .391" on 1 thru 11) Measured with stock .010" valve clearance and 1.75 to 1 roller rockers and stock cam,'75 model. Rockers have only been on car 125 miles, I had seen the #12 lift deficiency before installation. Thinking that I might have been sent a rogue 1.5 to 1 roller , I switched #12 and #10 rockers (both exhaust) and re-measured -- same result. (This is called grasping at straws, or looking for a fall guy)
So, next pull head, remove cam and lifters,inspect.
...to be continued.
|David--Thanks for the measurements confirming #12 lobe problem. I can't wait to look at my cam next month and compare pics with yours. Better still, looking forward to the improvements brought about by the Isky Z-19, APT lifters, and bumped CR.|
|Update: After pulling head,pan,rods-- a clear view of #12 cam lobe can be seen from below. Terrible. Cam lobe looks to have taken direct hit from howitzer ; appears almost melted down. (To refresh your memory, lift at valve #12 was measured at 65% of average of all other valves. Stock cam '75 US model, same as 125HP PI cam, 66000 miles on engine) New cam time.|
On initial inspection, main and rod bearing journals look fine as do cylinder bores. Out with dial bore guage today along with plasti-guage to verify. Thinking seriously of using external oil line on rebuild after all, as cam is lubricated by rockerbox overflow.
Done any more looking Rick ? Cover your eyes, it's ugly out there.
|Thanks for the update David. I'll probably see a similar wipeout when I get mine out. Is your engine still in the car? What shape were the lifters in? I'll be doing mine once I get all the bits in hand as I want to minimize down time. Waiting for Isky to return the spare cam, got APT nitrided lifters yesterday. Will measure bores and head for a 9.5 CR mill, then figure out how short the pushrods need to be. If I'm lucky, Swarthout's 1:1.55 rockers will be under the tree too.|
|David-In looking at an old block, I noticed that there are drain holes between each lifter and the oil drains onto the cam shaft. However, I don't see how it could lubricate the lobe. From what I have read on other sites about cam lubrication, splash&mist lubricates the lobes and that is why it is recommend to run the engine at 2000-2500 rpm for 20 minutes after installing a new cam, as there is insufficient oil splashed if the engine is allowed to idle. Am I missing something?|
|You are correct. I believe one of the lifter manufacturers (PRI) sells lifters with a tiny hole drilled through the face to drain the oil from the bucket to the lobe.|
|Hi again - Rick, yes engine is still in car,I've been doing a lot of measuring and cleaning --the crank journals, both main and rod are still 'in spec' and the cylinder bores I'll measure later tonight.|
The lifters are still installed as I can't get them out till the cam comes out. Either the bottom of the lifters are mushroomed out or there is a ridge from carbon buildup that solidly stops any attempt to lift the lifters out from above. Does anyone have any suggestions on removal ?
Berry, you're probably right about the drain holes in the block if the oil drops straight down onto the cam, it wouldn't get to the lobes , however, my thinking is that there's a lot of turbulence and motion in the crankcase and the more oil dropping down on to the cam the better - it'll be part of that 'mist and splash' you refer to and will help lubricate the lobes.
Rick,I'm going to contact PRI about the drain hole in the lifter, that sounds promising. Dinner break is over, back to the garage.
|Update again. Cylinder bores are amazingly straight - differences of only 1 to 1.5 thousandths from top to botom , thrust faces or sides. 67,000 miles -- I'm very surprised. But the motor has so much dirt and grime-inside and out , I'm tempted to pull the engine just to hot tank it. I must be getting older. |
Oh, that's another thread.
I think I just had a senior moment --
|David--Check Berry's sticks or grease workaround near the beginning of this thread for removing the cam from below. This sounds like it will work if you can't get the lifters out from above.|
This thread was discussed between 03/11/2003 and 17/11/2003
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