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New rings are so tight.

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Rex A Lott Avatar
Rex A Lott Steve Kincaid
Newcastle, WA, USA   USA
1976 Triumph TR6 "Trix"
I guess I should get some feedback from the group before I go much further.

I am in the process of a full engine rebuild after I discovered blast media (glass bead) was left behind during the previous rebuild. So this is engine rebuild version 1.2.

I visually inspected the pistons and rings and re-installed them. Turing the crank seemed unreasonably hard to do with original rings. Then my mind did that neat trick where I over-think sometimes and it started to tell me that maybe the rings were dirty. Maaaaaaaaaaayyyyybe there was grit left in the ring channels of the pistons. I pulled the pistons back out, pulled off the rings, and cleaned the ring channels and there was nothing in there at all.

Of course I broke a ring pulling it off of the piston.

Wellllllll... you can't just replace one ring. So I bit the bullet and bought a ring kit and lovingly replaced all the rings including the oil control rings. Not a hard job. I could not get the pistons into the cylinders, each time getting stuck on the oil control rings. I ended up putting the old oil control rings back on. (Note these oil control rings came with these pistons and piston assemblies only have 100 miles of driving on them. They are like new.) I use assembly lube on bearings but on the pistons and cylinders and rings, I just lube with engine oil. I got the pistons into the cylinders without much drama except that I had to 'tap' them pretty hard down into the cylinder. After each piston is joined to the crank I gave the crank a full rotation using a long handled "breaker bar". After installing the 6th piston, I have to put my full weight - 180# on the breaker bar to turn the crank.

I test fit the crank bearings and they felt smooth and non-binding. Before pistons, the crank with caps and bearings (but no pistons yet) was also smooth and non-binding. I'm pretty sure all of this friction is coming from the drag of the pistons and rings in the cylinders. Lastly, I did gap each and every ring and indeed a couple rings needed light adjustment. I'm confident the rings are gaped correctly. It doesn't seem like one cylinder is binding, but they are all together producing a lot of drag. There is no audible scraping noise from the pistons. It's just stiff.

Is this normal?
Thoughts?

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Krom Avatar
Krom Paul K
San Rafael, CA, USA   USA
Steve-

From the book Tuning Standard Triumphs, by David Vizard, on page 11, comes this quote:

"Before fitting the rings to the pistons, they should be gapped. The 1600 motor should have the gaps on all the rings set at 0.010". The corners of the gap when viewed from above should have a 0.005" - 0.010" radius stoned on to them. The gap on the 2000 and 2500 c.c. engines is best set at 0.012' and again a radius of 5 to 10 thou. should be stoned on to the corners of the gap."

If your gapping of the rings conforms to these standards, the rings ought not to be at fault.

From the same source, the section on assembly addresses your question: "Assembly We should now come to the time when we are able to put the engine together. Assemble the crank, rods and pistons into the block using engine oil on bearing and rubbing surfaces. Having assembled the engine, we now come to the test which will verify your dimensional checking. Rotate the crank assembly about fifty times. Then using a torque wrench, establish the torque required to turn the engine over. The absolute maximum torque required to turn the engines over are 20 lb. ft. for the 2500, 16 lb. ft. for the 2000, and 12 1/2 lb. ft. for the 1600. If the build up has been done carefully, these torque figures can be as much as 30% lower. If the figure is significantly higher, then something is amiss, so you should go through what you have done to locate the cause of stiffness. Excess internal friction in an engine is a sure way to lose power. 5 lb. ft. of frictional torque over and above our minimum will cost us 6.7 b.h.p. at 7000 revs. As you can see, the moral is to build up an engine which is as free as possible whilst still failing in with our component dimensional limits."

If you need to exert body weight to turn the crank after installation of the pistons, something must be amiss. Big end bearings, small end bushes, rod twist or bending. I'm not sure what the issue might be with your motor, but it ought not require substantial effort to turn. Did you really adequately lube the cylinder walls?

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dicta dick Taylor
Downey, Callifornia, USA   USA
In reply to # 1599002 by Rex A Lott I guess I should get some feedback from the group before I go much further.

I am in the process of a full engine rebuild after I discovered blast media (glass bead) was left behind during the previous rebuild. So this is engine rebuild version 1.2.

I visually inspected the pistons and rings and re-installed them. Turing the crank seemed unreasonably hard to do with original rings. Then my mind did that neat trick where I over-think sometimes and it started to tell me that maybe the rings were dirty. Maaaaaaaaaaayyyyybe there was grit left in the ring channels of the pistons. I pulled the pistons back out, pulled off the rings, and cleaned the ring channels and there was nothing in there at all.

Of course I broke a ring pulling it off of the piston.

Wellllllll... you can't just replace one ring. So I bit the bullet and bought a ring kit and lovingly replaced all the rings including the oil control rings. Not a hard job. I could not get the pistons into the cylinders, each time getting stuck on the oil control rings. I ended up putting the old oil control rings back on. (Note these oil control rings came with these pistons and piston assemblies only have 100 miles of driving on them. They are like new.) I use assembly lube on bearings but on the pistons and cylinders and rings, I just lube with engine oil. I got the pistons into the cylinders without much drama except that I had to 'tap' them pretty hard down into the cylinder. After each piston is joined to the crank I gave the crank a full rotation using a long handled "breaker bar". After installing the 6th piston, I have to put my full weight - 180# on the breaker bar to turn the crank.

I test fit the crank bearings and they felt smooth and non-binding. Before pistons, the crank with caps and bearings (but no pistons yet) was also smooth and non-binding. I'm pretty sure all of this friction is coming from the drag of the pistons and rings in the cylinders. Lastly, I did gap each and every ring and indeed a couple rings needed light adjustment. I'm confident the rings are gaped correctly. It doesn't seem like one cylinder is binding, but they are all together producing a lot of drag. There is no audible scraping noise from the pistons. It's just stiff.

Is this normal?
Thoughts?

I'll confirm what you already suspect...having to use this much energy to bar the engine over is "not normal". It sounds like either the pistons are too large for the bore size (was the block rebored?) or the rings are too large for the pistons. Measure the bore diameter and compare it to the diameter of the largest part of each piston. Around + .002 on the bore would be good.

With the pistons out, you should be able to push the rings down inside the ring lands by hand, to see that there's nothing left over.

Using one ring at a time, push each down inside the bore, confirming there is a reasonable gap of at least .010.

Oil rings could overlap, but not cause a "bump" to interfere with them descending down into the bore.

Let us know what you find!

Dick



Finally, be sure that none of the connecting rod caps are marked for the right pistons, and none of the caps are reversed.

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LFMTR4 Avatar
LFMTR4 Lou Mijares
Scottsboro, AL, USA   USA
What Dick said. You should take each ring and push it down the bore and check at top, middle and bottom of the bore with the 0.010 feeler gauge. Use a piston without rings to push the ring down the bore and keep it level for measuring.

You might a few over sized rings. If not it has to be the piston ring grooves or diameter inconsistencies in the bores.

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1599027 by LFMTR4 . Use a piston without rings to push the ring down the bore and keep it level for measuring.

I just wanted to emphasize that point.

The factory calls for .012" to .017" for the top compression ring; .008" to .013" for 2nd compression.

It's quite common for replacement rings to be supplied a bit oversize, in case they are being fitted to slightly oversize bores.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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Hotshoe Avatar
Hotshoe Ken Brinkley
Portland, OR, USA   USA
That’s what she said !

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Hotshoe Avatar
Hotshoe Ken Brinkley
Portland, OR, USA   USA
A little drag yes ,180# not so much .have you checked the cylinders for taper ? I personally would go no further until cylinders were miked and double check the ring set . Best of luck at least it's the dead of winter . Ken PS we have matching colors ,mimosa and black

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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
You OP doesn't make clear if the resistance was progressive as you added more pistons, or was it the last that suddenly increased it? If the second, something is awry with the big end. Or just that piston. Remove, inspect, deal with any probs.

John

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POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
In reply to # 1599136 by tapkaJohnD You OP doesn't make clear if the resistance was progressive as you added more pistons, or was it the last that suddenly increased it? If the second, something is awry with the big end. Or just that piston. Remove, inspect, deal with any probs.

John

Was wondering the same thing. If you are using the 3 piece oil control ring (a waffle like spacer and an upper and lower scraper), it is very possible one of the the scrapers got caught on the way into the bore was forced out of it's groove and now one of it's gap ends is sandwiched between the piston and cylinder wall. - Pete

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Rex A Lott Avatar
Rex A Lott Steve Kincaid
Newcastle, WA, USA   USA
1976 Triumph TR6 "Trix"
Thank you everyone for your thoughts.

I gapped all the rings to 0.012-0.014” measured toward top of the cylinder approx 1/2-1” below the top.

I could easily use ring gap to measure cylinder taper on each cylinder from top to bottom by measuring ring gap at different locations in the cylinder.

I did not press the ring into its channel and carefully check that the ring can sit back flush with the piston sidewall all around. Perhaps these rings are bigger. I will also compare new and old rings more carefully.

I DID check friction after each piston was installed. Friction increased steadily with each piston install. I’m confident the problem is shared across all pistons.

I DID check piston fitment without rings and it seemed correct. Tight fit. No slop. Low friction.

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Rex A Lott Avatar
Rex A Lott Steve Kincaid
Newcastle, WA, USA   USA
1976 Triumph TR6 "Trix"
In reply to a post by TR3driver,1599002
The factory calls for .012" to .017" for the top compression ring; .008" to .013" for 2nd compression.

Top and 2nd ring have a different gap?

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Krom Avatar
Krom Paul K
San Rafael, CA, USA   USA
Yes. According to the TR6 Workshop Manual...


Attachments:
Piston Ring Gap data.JPG    39.3 KB
Piston Ring Gap data.JPG

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tirebiter Avatar
tirebiter Jeff Garber
Dighton, MA, USA   USA
Dry cylinder bore walls would do it. You really need to slather on lot's of oil when installing new rings. Absolute cleanliness is extremely important. Clean and then oil then install one hole at a time.

Make sure the cylinder wall is coated top to bottom with no holidays to start with. The sidewalls of the piston gets coated entirely with oil. Rings should be coated, on the edges. Reclean and then oil up the inside of the ring compressor just prior to installing the piston.

Sometimes it still ends up quite stiff. A real pain but can help is to put in one piston at time all by itself. See if they are all have exactly the same amount of drag. If not, there is possibly a con-rod problem on the stiffer one.

In your present situation, I'd be tempted to try squirting more lube into each hole and seeing if it frees sup with lot's of revolutions. Then wash the cylinder walls down with clean oil and try again.

Initially there will be quite a lot of metal being cut/scraped off from the cylinder walls. Repeated cleaning away the darkened lubricating oil and applying new can help expedite the running-in process. If the cross-hatch angle is to shallow, it can cause the rings to have excess drag, when brand new.

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Rex A Lott Avatar
Rex A Lott Steve Kincaid
Newcastle, WA, USA   USA
1976 Triumph TR6 "Trix"
Solved!

I spent a lovely afternoon debugging my issue and I'm happy to report that I found the cause.

My initial plan was to pull the pistons out despite no particular known problem with the rings. Again I hung my entire body weight on the end of my breaker bar and with a little bouncing I was able to get the crank to turn. Truly I remember the crank getting harder with every piston I added during assembly. As I started to remove the bolts holding the rods, I smartly decided to do an experiment. I just backed each bolt back 1 turn and viola' the entire crank assembly and all six pistons were again easy to turn. Going from 200 ft-lbs of torque down to less than 50 (guessing)! I wrongly thought all the drag was from the rings. After all that was what had changed. The rings were new.

When I assembled the crank I used this product: https://www.permatex.com/products/lubricants/specialty-lubricants/permatex-ultra-slick-engine-assembly-lube/ to lube the main and rod bearings but I used engine oil to lube the pistons in the cylinders. I don't have anything against this product. It's indeed very slick, and also very gummy. This is intentional so that it doesn't "run off" of the surface you apply it to. Somehow this was causing incredible stiction in the crank assembly. With the engine upside down (on an engine stand that rotates) I lubed the cylinders from the bottom. Then I pulled all the bearings on the crank apart and wiped away the assembly lube and re-lubricated with engine oil. Now the engine produces about 50 ft-lbs of resistance with all the caps re-torqued back on. This is reasonable to me and I feel confident in proceeding from here. The reduction in drag was pretty remarkable.

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tirebiter Avatar
tirebiter Jeff Garber
Dighton, MA, USA   USA
Glad you have made progress. I'm wondering how and why Permatex can make such bold claims yet you have discovered what appears to be a definite fault in the product. A real "fly in the ointment" as it were. Stuck in place ??!!!

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