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I would like to be able to reuse my rod bolts which were used in a serial no. CT6646E block. The rod bolts did not have any tab washers present. Moss Catalogue part # 320-440 shows that self locking bolts without tab washers were used after CT3407IE. Rodger Williams in his TR3 restoration book refers to these as stretch bolts and should not be reused. Are self locking bolts same as stretch bolts and can these be reused? If I can reuse these would you recommend the use of red Loctite? Thanks in advance. I plan on keeping engine stock.
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TR2/3/3A TR3-4 Rod Bolts
- Thread starter GerryL
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TR3driver
Great Pumpkin - R.I.P
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With respect to Mr. Williams, I don't believe that Triumph ever used "stretch" bolts. However, if they are permanently stretched, the threads will be distorted just outside of where they enter the threaded portion of the rod. Get a new nut in the proper thread and spin it down. If it goes all the way up against the unthreaded portion, the threads (and hence the bolt) are not permanently distorted.
There is a special "Oil resistant" Loctite that is recommended for use inside engines. I forget the product number offhand, but that is what I use. As I recall, the color is pastel blue.
There is a special "Oil resistant" Loctite that is recommended for use inside engines. I forget the product number offhand, but that is what I use. As I recall, the color is pastel blue.
Darrell_Walker
Jedi Knight
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Note that technically, you will have to have the big ends resized if you use ARP fasteners (and the higher torque they specify).
TR3driver
Great Pumpkin - R.I.P
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Just curious, has anyone ever seen one of the factory bolts fail? When Dad's TR3A engine swallowed a valve, the rod got bent to almost 90 degrees, but the bolts were fine.
I put some 200,000 miles on the engine that was in my TR3A (originally from an early 56 TR3); changed the bearings several times (ISTR the Haynes recommends it every 30,000 miles). Never had a problem with the rod bolts (although I did learn not to try to reuse locktabs after one broke and got sucked into the oil pump).
An earlier TR engine had a 3/4 race cam & header, etc.; giving it a tendency to break the tires loose when it came "on cam" in 1st gear. I broke lots of other things, never had a problem with rod bolts.
I put some 200,000 miles on the engine that was in my TR3A (originally from an early 56 TR3); changed the bearings several times (ISTR the Haynes recommends it every 30,000 miles). Never had a problem with the rod bolts (although I did learn not to try to reuse locktabs after one broke and got sucked into the oil pump).
An earlier TR engine had a 3/4 race cam & header, etc.; giving it a tendency to break the tires loose when it came "on cam" in 1st gear. I broke lots of other things, never had a problem with rod bolts.
D
DougF
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Out of curiosity, I have a Skidmore tester and will have test a stock capscrew.
The guy I worked for eons ago was a tool and die maker and always used aircraft engine bolts. His big concern was stripping the threads out of the rods, but he used slightly higher torques with no tabs. 7200 was his limit with the factory crankshaft, but a lot of people used the stock bolts. Can't remember any bolt failures. A test would be very interesting. We always wondered/worried how much elastic stretch might occur at those rpm's.
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I don't think there is a relationship between the lack of tabs and stretch bolts. The use of lock tabs, once common, is a rarity today. The same seems true with lock washers, nylock and trilock nuts and even flat washers in favor of flange nuts and bolts. Unless you are tightening the bolts with something more accurate than a torque wrench, e.g. toque angle or better yet, actually measuring bolt elongation, you are not using stretch bolt technology.
Oil resistant Loctite is 243 I think. I like the stuff but built several engines long ago without it and had no loose fastener issues. As I recall it was standard practice to re-use all fasteners that did not show viable damage and, like Randall, I don't remember a rod bolt failure.
Tom
TR3driver
Great Pumpkin - R.I.P
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The bolts did change and the locktabs were deleted. But I still don't believe they were a "torque to yield" design. Instead, the bolts were coated with a locking compound, and the factory recommendation was to replace the bolts every time because there was no good way to replace the locking compound back then. But today, we have user-applied Loctite, so the locking compound is easily replaced and there is no longer any reason not to reuse the bolts.
BTW, Kas Kastner and others suggest deleting the locktabs on earlier engines as well. Under extreme use, the relatively soft metal of the locktab can deform under the bolt head and actually cause the bolt to loosen without turning! Carroll Smith mentioned the same problem in "Screw to Win". But if you do that, it is important to check that the bolt does not bottom in the threads in the rod. The non-locktab bolts were slightly shorter as well.
PS, all bolts actually stretch slightly when properly installed. But normally the joint is designed such that the bolt remains within its "elastic range", meaning it returns to the original length when removed. See for example https://www.fastenal.com/content/feds/pdf/Article - Bolted Joint Design.pdf
I notice that Randall has changed rod bearings several times. I believe I need to change the rod bearings in my TR3 with a TR4 engine. Is there a good article anywhere that describes step by step how to do nothing more than change the rod bearings?
I have Haynes, Bentley, TR4 Service Manual, and Moss articles but they all contain so much information on rebuilding the entire engine that it gets confusing on ONLY changing the rod bearings and nothing more. I appreciate the help! Thanks!
Regards, Bob
I have Haynes, Bentley, TR4 Service Manual, and Moss articles but they all contain so much information on rebuilding the entire engine that it gets confusing on ONLY changing the rod bearings and nothing more. I appreciate the help! Thanks!
Regards, Bob
TR3driver
Great Pumpkin - R.I.P
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Best writeup I know of is in the Haynes. Chapter 1, section 18, steps 2 through 7.
But in a nutshell, you remove the pan (leaving the clutch slave hanging on it's hose and being careful not to snag the oil pickup screen as you lower the pan) and rod by rod undo the bolts, replace the bearings, install and torque the bolts. You'll have to turn the crank to get access to all of them but it's best to not turn it while you have a rod cap loose.
Probably best to inspect the oil pump screen and the pump itself while you're in there. (I've been known to change the main bearing inserts as well, but apparently that may not be possible with the later flywheel. There's also a gasket that gets torn and has to be replaced with RTV, so maybe it's best if you not disturb the mains.)
When you get ready to install the pan, check the flange for distortion around the bolt holes and beat it back flat if necessary. Also worth double-checking the bolt lengths. There is a special 5/8" long bolt that goes at the front center, and two extra long ones (1-1/4) that go at the clip for the road draft tube and the slave cylinder support. All the rest should be 3/4". When TS13571L came to me, almost every bolt was the wrong length, some too short and some too long; and many of the holes were damaged from the wrong bolts and/or overtightening. (Some of the extra-long bolts were probably to try to grab the last few undamaged threads in the block, but they were bottoming in the block instead of clamping the pan. I had to order more Helicoil inserts!)
All new gaskets & lockwashers, obviously.
But in a nutshell, you remove the pan (leaving the clutch slave hanging on it's hose and being careful not to snag the oil pickup screen as you lower the pan) and rod by rod undo the bolts, replace the bearings, install and torque the bolts. You'll have to turn the crank to get access to all of them but it's best to not turn it while you have a rod cap loose.
Probably best to inspect the oil pump screen and the pump itself while you're in there. (I've been known to change the main bearing inserts as well, but apparently that may not be possible with the later flywheel. There's also a gasket that gets torn and has to be replaced with RTV, so maybe it's best if you not disturb the mains.)
When you get ready to install the pan, check the flange for distortion around the bolt holes and beat it back flat if necessary. Also worth double-checking the bolt lengths. There is a special 5/8" long bolt that goes at the front center, and two extra long ones (1-1/4) that go at the clip for the road draft tube and the slave cylinder support. All the rest should be 3/4". When TS13571L came to me, almost every bolt was the wrong length, some too short and some too long; and many of the holes were damaged from the wrong bolts and/or overtightening. (Some of the extra-long bolts were probably to try to grab the last few undamaged threads in the block, but they were bottoming in the block instead of clamping the pan. I had to order more Helicoil inserts!)
All new gaskets & lockwashers, obviously.
Great! Thanks Randall! How do I know what "size" bearings to order? Moss lists: standard, .010, .020, .030, and .040. Also one article mentions using plastigauge procedure, but did not explain the procedure for rod bearings well enough for me to understand it. Also thanks for explaining about the rod bolts and the correct lengths? I'll be sure to check those.
p.s. GerryL thanks for letting me use your thread!
Regards,
Bob
p.s. GerryL thanks for letting me use your thread!
Regards,
Bob
bgbassplyr
Darth Vader
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Check the thrust bearings while you're there.
TR3driver
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Unless you already know, there is no way to tell before you remove them. Almost always, the undersize (if any) will be marked on the back of the insert. Eg, a .010" undersize will have the legend "010". If not, then you'll need to measure the journal with calipers or a micrometer. (Normally a micrometer would be required to check for wear, but in this case calipers would do since you're only trying to distinguish .010" steps.)
Plastigage is only good for very small gaps, it won't be helpful for deciding which inserts to order. If you want, you can use Plastigage once you've selected the bearings, as a double check that the clearance is correct. To use it, get everything clean and dry, then lay a piece across the bearing (the short way), install the cap and torque it to spec. Then remove it again. The plastigage will be crushed flat, and the flatter (wider) it is, the smaller the gap was. So compare the width of the crushed area against the markings on the paper. Also look to see that it is reasonably even across the width of the bearing. If it tapers from side to side, you may have a bent rod or incorrectly machined crankshaft. But since the engine was already running successfully, those things are not likely.
BTW, each rod cap is matched to its rod (they are machined together), so it's important to keep the caps in the same order. That's another advantage of doing them one at a time.
poolboy
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I might add that if the bearings are the ones original to the engine, there won't be a size or even an "STD" indication...just a bunch of numbers indicating the part number.
Probably be best to let us know what you find in that regard..also a picture of the inner surface of the bearings might indicate to a trained eye if a simple replacement would be sufficient.
Probably be best to let us know what you find in that regard..also a picture of the inner surface of the bearings might indicate to a trained eye if a simple replacement would be sufficient.
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Geo Hahn
Yoda
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You may find that the caps and rods have numbers stamped on them (1,2,3,4) but don't count on that and (as Randall notes) keep them in order.
I find it easier to remove the oil pump screen for better access to #1.
I don't recall having to let the clutch slave dangle by its hose -- I think I left it (and its bracket) attached by one bolt and only removed the other bolt which is actually the support rod.