MTFCA Forum

Bit the bullet the other day and attempted to bore a block for my new Skat crank. The crank that came out of the block was undersized, so I had enough babbitt to bore to 1.250. Making an embarrassing mistake in the cutter setting, I over bored the block resulting in the crank now sitting further up in the block than it should. Since it was oversized, the block journals are a little wider than they should be, but caps now hold the crank from lateral movement.Now at a cross roads in the rebuild. Do I continue even though ultimately the tail shaft would be a little higher into the fourth main assuming every piece is in its proper alignment since the crank sits higher in the block as noted. If so, do I need one of the "wobble" tail shafts I have seen and read about, or do I "just make it fit". Or---do I send block for re-pour and then re-bore with hopefully a correct setting.
In answer to an anticipated question, I have not measured my mistake to see how far I am "off" in the measurements. I will need to check the height of the cutter as used and figure back to 1.250. With that in mind for tomorrows measuring, how many thousands can I "get away with"? Thanks in advance for any comments and cures. Happy T'ing.

The bigger issue will be the center to center between the cam shaft and crankshaft centers. https://www.mtfca.com/discus/messages/8 ... 1255697887

Thanks Mark for the link. I had considered this and had fitted a cam with a standard gear as a trial. It went together---very close, with no lash. Thanks to Ashley and two day delivery I have an undersized gear on my bench and will try it tomorrow. Will also copy the measurements in the link furnished, and I appreciate same. Regards, Tim

If you have the option of doing it right, do it right. Question is how far off.
The 4th main position can easily be centered with some pan adjustment during final assembly. In fact, it was going to need a little adjustment either way. Perfect pan? Rarely.

if you are using a fixture that clamps to the block like gene french makes you are on center putting
the cutter too far out has made your bores oversize. what did you line bore it with? philip

Tim
The “floating transmission shaft “ is not intended as a fix for something like this!
It is my invention.
If it was my engine I would just bite the bullet and repore the babbit.

Another point in re-pouring, you will know what type babbitt was used. Right now, unless you know the history of what is now in the block, you might not know.

I wouldn't "adjust" the pan to correct for this, but I would consider boring the babbitt in the 4th main at an offset to match the main bore error. All depends on just how far off you are.

Actually, if you took a skim cut off of the pan rails you could use a standard 4th main. Again, depends how far off... And, how much you want to bastardize the block...

Mark Gregush wrote: ↑

Tue Nov 16, 2021 12:42 pm

Another point in re-pouring, you will know what type babbitt was used. Right now, unless you know the history of what is now in the block, you might not know.

Good point! How old/used/dirt embedded is it?
Something to strongly consider in the re-do question.

If I'd invested in a new crank I'd want new babbit of known quality and take the opportunity to get the cam/crank spacing correct, full 360 bearing contact, a new thrust face, and so forth. Old babbit may not have good contact with the block, and that could cause problems.

It depends on what you want out of your engine. If you are going to show the car from time to time, you could probably get by, however, if you are planning to tour, you should get everything in top condition. That would include the condition of the pistons, rods and all bearings, as well as perfect alignment of the cam gears. If you change everything else to fit those bearings in the block, you are just asking for further problems. With the winter season, you have plenty of time to fix things right before the summer tour season.
My grandmother used to mend clothes and she had a saying,"A stitch in time, saves nine"
Norm

In answer to Phillips post, I used an original KRW boring jig with false cam and a boring bar I had made some time ago with only one cutter so one does not have to set three cutters as the original. I realized the over cut would widen the journals and thought about correcting this with caps, which is now a moot point. Also today I fitted the undersized cam gear recently received---and there is zero lash. Nada--none--gears fit so closely I could not get a feeler gauge in, although they all turn freely--so I knew this would not work.
In regards to the other posts from my Forum friends, your comments were spot on, and appreciated. it is time for re-pour and rebore to specks. I knew this all along, but just kept hoping there was a cure. For those who do not know me, I have been around T's since 1954 when my 15 came to live with me, and as many, self taught with only the one book back then. We have come a long way as a hobby.
Again, I appreciate all those who took the time to comment, and I will look forward to more posts and comments from others who have concerns and questions.We have the best folks willing to help in so many ways. I am continually impressed with.the knowledge and abilities many of you have.

Yes Les--I follow your posts and knew the shaft was of your design.. Thank you and so many others with the talents you and they have.