MTFCA Forum

Hi

I'm replacting 2 con rods at the moment & I have a few questions that someone might help me with.
I have the Model T "Bible" but cant find it at the moment.

I got the flexi gauge, wondering what the clearance should be between the con rods & crank shaft. Is it necessary to fully clean the flexi gauge from the rods & shafts as it left a residue after I tried it.
How tight should I torque the con rod bolts to the crank shaft & piston.
How tight should I torque the head

Thanks in advance
Noel

yes, clean the residue off.
torque is 'very tight'.
head torque is also 'very tight'. Once you have run the engine a bit more, then tighten them again.

.0015" clearance.

I wouldn't go above 50 ft/lbs on the head bolts. I would also carefully inspect the bolts before reinstalling them. Unless you are installing new bolts, the ones that you have are (or are over) 100 years of age.

Yellow Timsaver will get the clearance right, and no mess with plastigage and scraping babbit.

I skip using any kind of spreading type of test strip such as Plastiguge. It was made for harder shell type bearings and have found over the years it just does not spread like it should and seems to embed some in the babbitt more then spread.
I use the aluminum foil method. A piece of standard kitchen foil about 1x2 inches folded in half should be around .0015 thick. lay the foil in your cap, install the cap torqued to about 30-35FPs. If the crank turns easily, remove cap and shim repeat process till crank just wants to turn but doesn't. Reinstall the cap and check.
Under the car or rebuild, that is how I check. While some people say no, I use the alternating removal of shims. Once I get close, both shim packs the same thickness, I remove a shim leaf from one side, check fit then if not there yet, remove a shim leaf from the other side till I get the fit I am looking for.
In any case, fitting babbitt, you need to fit the rod to the crank. Which under the car, is a lot of getting out then getting back under.

Thanks for replies,
The Plastiguague was very difficult to remove after use so probably wont use it again,

Regards

Noel

Plastigage is removed quite easily with Brakleen or solvent & your finger nail ! I've used it regularly for years and not had it imbed in the caps - it always stuck to the crank journal.

Been using it for more than 50 years, the trick is for a good even reading and easy removal is to oil the cap and crank.

A little light oil on the journal will prevent sticking. It doesn't take much. Marvel Mystery Oil would be ideal. Keep everything clean and lint-free for accurate readings.

I have another question, seeing as I have 2 of the pistons out I was wondering if I should replace the rings. What is the method for checking if the are worn.
Thanks for all the advice

Noel

As inexpensive as rings are, I'd be inclined to replace them. Do all four cylinders. The rings can both wear and lose tension. Piston ring grooves can also wear. It's important that the rings fit the ring grooves correctly and that the end gap is correct. New rings will not perform well in worn ring grooves and they will wear rapidly. No use putting new rings or worn or poorly-fit pistons. New pistons are also cheap. Cylinders need a light honing in order for rings to seat. Used rings put back in an engine may not seat well. Any used parts put back in the engine need to be put back exactly where they were originally. That can be very difficult in the case of rings. Use caution when tightening rod clamp bolts at the piston pin. It's easy to twist the rods. Cylinders need to be in good condition. Egged, scored, or tapered cylinders will not perform correctly and will cause rapid piston and ring wear.

I agree that you should install new rings. After i installed new rings without reboring or new pistons, the compression went from 50 pai to 62 psi. The pistons or the head are not the high compression type.

Art Mirtes

corkmodelt wrote: ↑

Sun Sep 18, 2022 10:16 am

I have another question, seeing as I have 2 of the pistons out I was wondering if I should replace the rings. What is the method for checking if the are worn.
Thanks for all the advice

Noel

Look @ the ring gap. It should be around .018. You can see the top ring gap without pulling the pistons. With a piston out, carefully remove the top ring @ put back into the cylinder. Square it up in the bore with the lower piston skirt. Check the ring gap with a feeler gauge. Check the gap top, middle & bottom of the bore. Same gap? Yes rings are cheap. If your bores are still straight but worn, you can 'FIT" .010 oversize to your "bores" by filing ring gaps to get the optimal ring gap. If you are going to all the trouble, hone the cylinders to deglaze before putting new rings in..

Honing the cylinders will also show up any serious irregularities and uneven wear. The pattern left in the cylinder when the honing job is done needs to be correct for best results. Use of correct stones is also important. New pistons will give new rings the best chance of giving long service with good compression and minimal oil consumption. The bottom end needs to be in good condition also. Loose rods, wrist pins, and main bearings hammer pistons and rings needlessly. Rod alignment needs to be within specification. Irregular wear on pistons or cylinder bores may point to misaligned rods.

Thanks for all the replies

Noel

Hi Folks,

Sorry for bothering you again, but I'm just getting back to my T engine. It looks like that I'll have to get a con rod. I measured the crankshaft & I'm getting 31.26mm or 1240th. How would I know what size to get, standard or 10 or 20 oversize.
Has anybody an easy way of splitting the shims from Langs. I think they come in bundles of 10, but 10 is too big for me?
I plan to take out a piston tomorrow & take off a ring 7 put it in the cylinder. What gap should I have in the ring?

Thanks

Noel

A lighter on the edge of the stack works for me. Other May have better ways.

Hi JTT3,

Lighter worked great thanks

Noel