I have just removed the head on my 1979 Triumph Bonneville Special to replace the seals in the Push Rod Cover Tubes. I have read the many posts on this subject but was surprised at how tight the tubes were in the head. I expected the tubes to slide up the cylinder barrel but this was not the case. There is not enough clearance. I had to make a stepped plug to drive them out of the head. Getting to my question. Should I replace the "O" rings on the Tappet Guide Blocks. Are there any precautions to be taken when removing the Tappet Guide Blocks?
By all means you should replace the the frt tappet block oring, there is no oring in the rear one so leave that one alone. In changing the oring remove the sharpe edge at the barrel entry area if you don't the oring may get damaged. Clean the the area well around the block and the barrel were the block sits,place a little sealer at the very top of the block so when its set down its like a secondary seal. Lub the seal and block and install. Go to a oring seal store and match the lower white 1/8 sealing washer with black quad orings ,install the quad orings dry and replace the pushrod tube seals with viton seals use a little oring lub reinstall the head. Stay away from a lot of silicone sealers around the push rod tubes themselves ,the oil pressure is in the tappet block, have a look at the repair manual to confirm. Good luck Its a big job taking off the head and barrels but its the only way for success
Originally posted by Jim H: By all means you should replace the front tappet block o-ring...
You may be forking with stuff that's about to bite your arse. Although the design is very simple, that does not mean it's easy to do, quickly implemented, or inexpensive. Please read all you can before going any further. And buy at least 2 workshop manuals since no one manual gives even 50% of what you'll need to know.
Jim H has the correct answer. 90% of what people call "PRT oil leaks" are actually coming from the tappet blocks. And usually it's the exhaust tappet block, since it sees the same oil pressure as the rod bearings. However, Blapper is also correct, each tappet block has its own o-ring.
Removal and installation of the tappet blocks requires a special tool and lots of practice. I would therefore advise you to send your cylinder to an authorized Triumph repair depot for this work.
There are also many, many special pieces of knowledge concerning reassembly of the PRTs and their gasketry. Chief among these is the head gasket clearance which MUST be observed.
In the end, I bet you'll be kicking yourself for not simply pouring in more oil and looking the other way.
Originally posted by RF Whatley: However, Blapper is also correct, each tappet block has its own o-ring.
Not necessarily correct for 1980 according to the parts list?
As only one tappet block O-ring (70-7563) is specified for the 1980 models according to the 1980 parts list? Both tappet blocks (and push rod tube/seal assemblies) being new for that year, the new inlet tappet block being part number (71-7194) and the new exhaust tappet block (71-7195).
No tappet block O-rings are listed for 1981 but reappear for 1982 as "not illustrated" items?
Pressure-fed exhaust tappets ceased to be used from engine number EDA30000 (1982) as a result of that, the exhaust tappet block was replaced by a second inlet 71-7194 item, if the parts lists are to be believed?
I must apologize gentlemen for saying there was only 1 o-ring on the tappet blocks. I have replaced only the front exhaust tappet oring on the 2 T140,s I've owned ,I removed the rear blocks and found neither one had a oring in place and "thought" that since it was not there and never leaked and no oil pressure to the rear tappet block, only the oil draining back it was not required. Goes to show it does not pay to "think" and not go by the repair manual. I have never had a rear push rod tube leak yet:::: Maybe Lady luck was on my side.
No they can't, and as RFW hints at, it is a job that is MUCH easier to cock-up than get right. Mine was done by a pro and screwed up, and I suspect you aren't close to that standard yet (no offense meant). One little part of the problem is getting the right size 'O'ring in there. One gasket set I bought had the most useless collection of 'O'rings in that I've ever seen. Some people who know tend to buy them individually.
You must remove the barrels ,remove the little set screws and use the tool. Don't forget to put a bit of gas line tube over the lifters to hold them in place, you don't want them to drop into the bottom end. Take special attention to the way the front lifters go, it shows their direction in the manual. Once the barrel is off remove the lifters. Turn the barrel over insert the drift tool and knock the blocks out,do not mix them up maybe do one at a time.Clean the area around the barrel and block replace the oring. Before installing the lifter block remove the shape edge from the barrel entry ,a little Dremel or a piece of sand paper will work,it doesn't take much this will prevent cutting the oring when installing it, grease the block and barrel area add a tiny amouny of sealent at the very top of the lifter were it meets the barrel.Install the lifter blocks put the lifters back in ,holding them in place with the hoses Replace the gasket put on the ring clamps and put the barrels back on.Put new viton orings in the lower tube and in the head area ,not on the upper tube. Put on the sealing ring and the wedding ring install the tube over the block ,they do angle in towards the head make sure you feel and good tight fit onto the block ,gease the upper ring and carefully lower the head onto the tube you will see the tube coming through the oring. check for a small gap between the head gasket and head If all looks well put in the bolts and tighten and torgue as the manual states. Its just that easy.
Re: Tappet Guide Block "O" Ring#139790 04/23/082:29 am04/23/082:29 am
BTW, I just did a TOTAL top end. It was NOT a hard job, but did require a LOT of homework, about 50/50... half here on the forum researching old posts and dropping questions on the forum, and half in the manuals. So far it has worked out GREAT. I'm at about 450 miles, and thinking about dropping the 30 wt. non detergent oil, and running my usual. Unfortunately, I DO HAVE AN OIL LEAK! Poopy! The seals are leaking in a couple of places now at the bottom of the rocker cases, which were installed dry, and I THOUGHT were going to be fine. Ahhh... YAMABOND next. LOL.
Re: Tappet Guide Block "O" Ring#139791 04/23/086:24 am04/23/086:24 am
Nobody has mentioned that the guide blocks are easier to get in on the piss that straight. There is no orientation guide other than the hole for the hex screw and that is not enough. The screw can still be put in, but the (soft) nose of the screw gets deformed. If you get the guide block in turned around a little, there is not enough movement in the extensions that protrude each side of the follower to allow the followers to rotate enough to establish the correct relationship to the cam and the line contact which isn't a contact - it's held apart by your oil film strength becomes a point contact that the oil film strength cannot hold apart.
My engine had been rebuilt like that after a bore and it sees off a set of cams and followers pretty damn quick. It is too difficult to do 'by eye' as the barrel casting is a low tech sand casting and the bottom of the bores are different thicknesses from side to side. You need to use something perfectly parallel and come off the head studs to establish the centre line of the bores of the followers are parallel to the centre line of the bores of the cylinders.
As Blapper mentioend the tappet block must be aligned. If you get the bright idea to use a parallel and the adjacent stud holes in the cylinder flange for reference, remember one stud hole is larger to provide room for the alignment dowel on that stud. John
My original intent when I started this project was to replace the push rod tube seals. Then I got lead to thinking I should replace the the tappet block "O"rings by reading other posts. When I removed the push rod tubes there were "O rings on bottom the tubes but there was no white sealing ring. The sleeve that I think is referred to as a wedding band was filled with silicon sealer. Now I don't know if I should attempt to replace the tappet block "O" rings. I have not removed the cylinder block. What do you folks think? Thanks for all the responses so far.
Gtroms if you do not address the problem of the lifter block oring which is under pressure ,not the PRT you are doomed to failure. As several of the guys said in earlier replies. It is a little more work ,but is nothing worse than putting the motor back together and finding out the leak is still there. There is no short cut. Place a scribe mark on the block and the barrel to confirm the location when you reinstall the block. You need the tool ,its a lot easier. After reading the little bit of info from the workshop manual I'm even thinking maybe a flatrate mechanic could tap the lifter out enough to remove and replace a new oring??? if he was worried about the aligment. The problem with that method is the sharpe edge on the barrel might cut the oring when installed. Good luck. Reread the repies and take a look a the engine lubrication diagram for the direct of the oil travel and pressure
He hasn't complained about a leak from the guide blocks, only the prt's.
I have never had or seen a tappet block fail in normal service, I've only seen them leaking after being 'fixed'!
My thinking is that in the face of such a hideous bodge in the base of the prt's another leak from the tappet guide blocks is unlikely to be contributing. Driving the blocks out part way is no proof of them not turning during that process IMHO.
Hi Blapper, I agree you are 100% right on the fact the gentleman wasn't complaining about a leak from the guide blocks he was interested in the PRT leak. I was sincerely tring to help this fellow from making the same mistakes I have made in the past. See RF Whatley comment. Again I apologize if I have offended anyone. I sure don't know it all but I have had the good fortune of knowing and having had a lot of help from some excellent British M/C mechanics ,was only tring to pass along my experience Cheers Jim
No sweat Jim. No offense taken at all, no need to apologise.
A slightly turned guide block is an insidious thing, slowly destroying previously good cams. My thinking was that even if there was a weep from there after the prt's are done, it isn't the end of the world.
Originally posted by Blapper: Nobody has mentioned that the guide blocks are easier to get in on the piss that straight. There is no orientation guide other than the hole for the hex screw and that is not enough.
What I did when I put them in recently, was to take a dark, thin permanent majic marker, and draw a line with a ruler on the tappet block. This line ran from the center of the hole in the tappet block to the top of the block that you first insert. Then, I made sure that the line "matched" up with the hole in the base of the cylinder head as I started to drive the block using my fancy tool, and as the block was driven home, I made sure the line was indeed still in the center of the hole through the base of the cylinder head. When I was done, the two holes were exactly aligned. This was not my idea, btw, think I read it here on the forum.
Wow lots of opinions. I really don't know if the tappet blocks were leaking. I do know that there was always oil leaking from the bottom of the PRT.Is there a way to tell if the tappet blocks are leaking? I just thought it would be a good idea to replace the tappet block "O" rings. Now I am having a real tough time making a decision. Leaning towards leaving the tappet blocks alone because of finding that there was no sealing ring only the "O" ring and silicon at the bottom of the PRT. Thanks for all the opinions.
Referencing the old tappet guide block with scribe lines or magic marker assumes that it was installed properly by the last mechanic. It also assumes that the holes in the cylinder casting and tappet guide blocks are in the correct place. Having manufacturerd several thousand tappet guide blocks in the 1970's, we discovered some interesting things about factory tappet guide blocks. One of them is not to assume the factory got it right all of the time. I am sure we didn't get it right all the time either, as there is a lot of handling envolved in making these things.
If you are going to use the scribe, magic marker or hole alignment be sure to check the alignment before removal. If wrong, you can correct it when re-installing the guide block.
Having seen many dissapointed customers that did not replace the tappet guide block "O" ring when they thought the oil leak was the coming from the push rod tubes, for me it is a no brainer.
One of the arguments I often hear is: "it is the rear push rod tube that is leaking, it can't be the tappet guide "O" ring as the rear one is not under any pressure." They forget that there are open passages in the casting between the cylinders from front to back where oil can migrate to the back of the cylinder. It's one of those Triumph gotcha's.
As an aside, its amazing how much guide block miss-alignment the cams and tappet/lifters can tolerate and still survive. Most people who assemble these neither have the tools or expertise to do the job right. With the factory tool it is a fairly straight forward job. Just a bit fussy to get right.
Oh, when you "drive" the tappet guide block home listen carefully. When the note from the hammer blow changes STOP! Do not hit it again as you are liable to crack the guide block. And don't try it without the factory tool or a reasonable copy. It is very easy to break the tappet guide block! Just my opinion! John