View Full Version : TR6 Fresh TR-6 Engine Rebuild, Blue Smoke.......

05-31-2005, 10:40 PM
I just finished a frame off resto project on my 70 TR-6, including a rebuild on the engine. New parts included main and rod bearings, new thrust washers, new oil pump, new timing chain and follower, new rings (std size), and new exhaust valves. We miked the cylinders and the wear was minimal, so went with std rings. Engine fires right up and runs fine, but smokes like an insect fogger. We used plenty of rebuild oil when reassenmbling, and the engine has zero miles on it other than running for 15 min or so in the garage. My question is: did we screw something up, or will this go away eventually when the oil rings seat? Compression is OK across the board. I pulled the plugs and several have oil on them, not alot, but some. Thanks for any insight,


05-31-2005, 11:11 PM
It's not uncommon for a high-mileage or worn-out engine to have lots of slap in the cylinders/cylinder. Could it be possible that a 20 over bore might have been in order? Helluva time to mention that now. On a more positive note, after rebuilding mine, the iron rings would never seat so I broke it down again and went with Deves stainless rings and solved the problem. Let's hope that yours is just a messy breakin.


05-31-2005, 11:34 PM
You didn't mention any refurbishing to the head. If you neglected the valve guides & they are worn , you would create a similar "blue smoke" symtom. If your using an auxiliary oil feed line an excesive smoke & oil consumption situation may occur as well.

Your compression numbers may not be accurate until the rings seat. This may take at least a few hundred miles. If your compression numbers are anywhere normal now my attention would go to the head. As much as either of these repairs suck after doing so much work already, the head is the easier repair.

Dave Russell
05-31-2005, 11:36 PM
Did you hone/deglaze the cylinders before assembly. If not, it might take a long time for new rings to seat.

05-31-2005, 11:59 PM
We did dehone the cylinders, but didn't do anything to the head other than exhaust valves. I'll get it on the road and drive it for awhile before I guess I'll know if this is a break-in problem, or if I get to try and not destroy a pristine engine compartment as I dismantle the motor once again. Live and learn I guess..thanks for the advice,


06-01-2005, 12:01 AM
What I meant to say is that we honed/deglazed the cylinders. I guess rebuilding the head would be much easier than tearing out the bottom end of the motor again....


06-01-2005, 12:24 AM
When you assembled the engine, what did the ring gaps look like? And, did you check the clearances between the valves and guides?

06-01-2005, 09:31 AM
Sounds like valve guides to me but it is too soon to tell. If you installed the conventional rings a few miles should seat them since you honed; if you put in the space age rings, it occasionally requires many miles to seat. Since you have good compression, it sounds like your compression rings have seated ok. Assuming the oil ring was installed properly, and since you have oil on the plugs, I would suspect the valve guides need replaceing. All of that considered, I would still put a few miles on it before I took anything major apart.

Simon TR4a
06-01-2005, 09:59 AM
Agree with the above, don't panic yet!
When you measured for bore wear did you measure several places? The reason I ask is that there is often more wear on the "thrust" side of the cylinder, or at the bottom of the stroke than the top, because of the angle of the connecting rod. You likely thought of this, though.
Good luck, Simon.

06-01-2005, 10:14 AM
I'm on the boat with the guys saying valve guides. Shouldn't be that big of a deal, an hour to pull, about four hours to tear down the head, and press in new guides, and about an hour to get back on the road after that. Easy as pie.

06-01-2005, 11:05 PM

Thanks for the advice. The majority of folks in the MG Car Club here in Rochester agree its probablly valve guides as well. The compression values ranged from 145 to 155, and the only other sources of oil entering the crankcase (breather, bad brake servo check valve) have been eliminated as well. I really need to have the whole head gone thru, as the rocker shaft isn't that great either. My 84 year old father in law helped me rebuilt the motor, and his depression era fixes eliminate the "preventative replacement" of parts. Ha! Live and learn, and now I'll know how to rebuild a head myself, right? As for bad oil rings, is it possible to have great compression and still have enough blow by to have that much smoke if for some reason we screwed up installing the oil rings? Just curious....

Thanks again,


06-01-2005, 11:08 PM

I let the car run for 20 minutes at 2000 RPM, since I don't have the seats in the car yet. One of my neighbors came by to see if our house was on fire!!! Ha! The smoke didn't let up, so I think tomorrow its head rebuilding project time!


Geo Hahn
06-01-2005, 11:40 PM
My (admittedly limited) experience with this is that worn valve guides will usually give you blue smoke at start up but not a lot after that. To me your situation points to the oil control rings. I would give them a chance to seat unless I thought I hadn't done enough to roughen the cylinder walls. I assume the oil rings were the usual 3-piece arrangement: 2 rings and a wiggly bit sandwiched between them?

06-02-2005, 12:09 AM
/ubbthreads/images/graemlins/iagree.gif Thats been my experience with worn valve guides too. It sounds an awful lot like oil rings not seating or not properly placed on the piston. You didn't put the oil ring gaps in line, did you? It might even be a combination of all of the above. Could the engine have put a lot of oil in the exhaust before the rebuild? Maybe it just needs to burn off. Oh well, just a little food for thought. /ubbthreads/images/graemlins/grin.gif

06-02-2005, 10:29 AM
You remind me of any Olympian, they make every thing they do LOOK so easy. It took me a week and a mile of rope to get the head off. If some good sole from BCF had not mentioned the rope, I think I would have said "calf rope" and got some body else to remove the head. On the other hand, since it is a new rebuild, it should be a lot easer than pulling the head off an old tired motor with cruded studs. I wish you lived close to the Atlanta, GA area; it would be refreshing and educational to watch a person work when they have those Olypian skills.

06-02-2005, 12:22 PM
While reading about your delima, I remembered the first engine I rebuilt. 1948 Ford flat-head V8, great motor, reliable and all that, but when you install the oil rings upside down, it imitates a fogger. This is a little more than the 'blue-smoke' definition you used.

Webb Sledge
06-02-2005, 09:58 PM
I recently rebuilt my engine as well, and like has been mentioned, your rings most likely just need some time to re-seat. My car only has about 400 miles on the new engine, and it still will let out a wisp of blue smoke occasionaly.

06-02-2005, 11:21 PM
The latest news....pulled the head today and rebuilt the rocker assembly, shaft was badly worn and thanks to Mark at British Auto, I now have a like new rocker assembly. Next was to take out the pistons. I dropped the pan and other than snapping off one pan bolt, the piston removal went fine. I FOUND THE PROBLEM!! The oil ring was actually flush with the piston wall on all 6 pistons. There is no spring tension on the ring assembly, it just sits flush in the groove and hence no wiping action. Either we installed them wrong or they are defective. I'm going to let Mark decide that tomorrow. I'm almost certain that they were protruding as the compression rings were when we put the ring compressor on to reinstall them. Puzzling. He'll also look at the guides and see if they need renewing at the same time. I was pretty happy to have completely dismantled the motor in one day, find out why it was smoking so badly, and haven't disturbed anything that I'll need to repaint in the engine compartment (yet). Thanks for all the advice guys, I really appreciate the wealth of knowledge on this forum.

Mark /ubbthreads/images/graemlins/cheers.gif