Rod bolts, run original or buy new?

[Paperman]

Going through my 27 T. Bolts look good, reuse or replace? Going to aluminum pistons, overbored, new babbitt and ground crankshaft.

[Norman Kling]

If the threads are good and the nuts fit well, you can use the originals, but if they are stretched out, it is best to use replacement bolts. You must find bolts with the right type heads because one side is ground to fit against the rod and the other side is ground to avoid hitting other engine parts when it rotates.
Norm

[JTT3]

Hi Robert, welcome to the hobby, good advice from the other posters. Are you rebuilding your engine or having someone professionally & familiar with model T’s doing the work? I ask because you want the best possible outcome from the rebuild. You especially need to know who did the regrind on your crankshaft & their knowledge concerning the correct method. If they don’t have that experience it could be a bad experience. The stone used has to be specifically dressed for a T model crankshaft in addition to knowing how to capture the crank for a regrind. Hopefully you’re in a good situation with all of that.

[Paperman]

Thanks for the welcome. I’m doing the work myself other than the crank grind and valve seats/guides for the newer larger valves. I’ve build many engines and have a lots of machines for making chips.

On the crank I’m having a typical automotive engine shop do the grinding. I asked them to copy the radius that is on the journals as they are and to touch/square up the thrust pads on the rear main. Is there more they need to know?

Im a maintenance supervisor at a large papermill and an aircraft mechanic by trade. I’ll change bolts if needed, just don’t see the sense in changing them if experience shows they don’t need it.

[BobShirleyAtlantaTx]

Small block Chevy are hard to beat. Cheap and fit well.

[JTT3]

Good tip Bob Shirley! Robert a T crank should first be checked to see if it is crack free & straight. It can’t just be chucked up to a crank grinder. The crank as you can see is spindly and if the the jaws are put on with pressure you can bend the crank and then the grind may look good but will actually have been ground off centerline. Good idea about just touching to clean up the journals. You can bore the rods to each size for each journal. It will be more labor intensive but you will have more meat on the bone instead of going a standard size across the crank. I know folks that will grind to 30 under but I don’t like to go past 20 if possible. Hopefully your crank is an EE style. You’ll find those markings cast into the crankshaft. Are you pouring your own babbitt? Check your rods for bend & twist too.

[Paperman]

Plan is to pour my own. How do I know the style of crankshaft? I assume it is cast into it or has a feature that is prominent. It appears to have had some pretty healthy grinding on the throws for balance.

I can magnaflux the crank if that is the preferred method. I’m hoping to only grind .005 off but the grinder will make that call. 2 rods are .0025 out of round the mains look good and have done shim left but the thrust surface is opened up to .030 so I figured if I’m grinding and pouring rods, mighta a well jump in the deep end and do it all.

[Craig Leach]

Hi Robert,
If the mains are in spec. and the Babbitt looks good consider just replacing the main caps or even just the 3rd for end play repair
I use Magnaflux myself but many prefer dye penetrant because of the irregular shape of the crank makes it so hard to Mag. test.
When you get the crank back make sure it isn't bent. Everyone I have had done has come back bent. If it has to be straightened
make sure to check the flange runout or you will have 4th main issues. Finding someone that has a pan anvil is a major plus.
Craig.

[Allan]

If your crankshaft will clean up at .005"you are very lucky. Most cranks have wound up more than that. The grinder has two components to deal with, wear on the journals and wind-up/twisting, after it has been checked for being straight. By doing the babbit work yourself you are in the best position to grind for minimum removal, and match your babbit machining to it.

Allan from down under.

[TXGOAT2]

Does it actually need grinding? If it doesn't, don't.

[Norman Kling]

I had a good crankshaft ruined by a machine shop. It didn't need grinding, but the babbitt man I use asked if I had magnafluxed it. I said no and took it to the machinist who said it is not cracked but it is crooked. I asked if he had the equipment to straighten it. He said yes. When it came back the rods were 30 thousandths under size. I think all he had done was to grind everything till they were aligned. That was when I installed a SKAT standard stroke crankshaft. So if your crank is crooked, straighten it do not grind to alignment!
Norm

[Original Smith]

I believe the castle nuts are 11/32". I doubt if you will find any of those easily!

[Allan]

Original, 11/32" is way under !/2". Did you mistype 21/32". That puts it near the %/8" i have found on our Canadian sourced cars. I do believe these are not available either, so re-using the originals is likely the only option if one wants to stay with them.

Allan from down under.

[NoelChico]

I second the suggestion of Bob Shirley regarding using small block Chevy rod bolts. They have a knurled shaft that must be ground down a bit to slide into a model T rod but that is easy with a file and a drill press. The heads have a flat side that fits the T rod well. BUT they don't weigh the same. A T bolt and nut weighs 41.3 gm and a SB Chevy weighs 38.7 gm. I made the mistake of replacing 2 partially stripped stock ones with Chevy ones 15 years ago and recently, while replacing a rod, noted my #2 and #3 rods had the Chevy bolts. I suspect the weight difference "may" have contributed to a vibration I had at over 37 mph. Maybe that small a difference means nothing in a Model T. I'll find out this spring when the engine is back in the car and it's warmer. They torque at about 44 ft-lbs. and don't need cotter pins.

[Allan]

There are times when a lighter con rod bolt helps when balancing the big end. Less material to remove from the cap and rod.

Allan from down under.