I am tightening up the rod bearings on my engine as they have not been checked for a while and found that Rod 1 and 3 have .030 side clearance not the .012 listed spec.
I ordered new rods and found that they are .002-.003 narrower than the ones I have.
1. Is there a spec. on how wide a rod should be?
2. Other than a noise is there any issues having .030 side clearance.
3. I there a spec. on journal width.
Thanks as always, Steve
A Model T rod should be 1.500 wide.
Model T connecting rods are 1.480" to 1.490" wide according to the T-487B Ford Print.
Final grind of the rod journals of the crank shaft were specified at 1.495" to 1.505" BUT... Acceptable finished width upon inspection of the rod journals of the crank shaft per the T-498-B Ford Print was 1.494" to 1.514"
So... This means that a .005" to .025" "side play" was what they were shooting for, but it was possible that they could still send one out the door with up to .034" if the crank journal was at its maximum and the rod was at its minimum.
Using the median values from the crank and rod prints, you can roughly figure that rods were intended at 1.485" and crank shaft journals at 1.500", therefore an "intended side-play" of .015" is probably what was intended.
Among many of the people who build a fair amount of engines per year, it has been known for several years that many of the repro rods have "issues". (off center, bent, twisted, narrow faces, improper radius).
Adam, those figures are bogus in reality.
I have never found a Model T crank that a Model T rod cut to 1.500 would not fit.
Those I have measured are from 1.505 to 1.510 and some 1.505+.020.
In the 51 years we have been babbitting, and in excess of 30,000 Spun Poured Model T rods sold, no one has ever said that they couldn't get a rod to install on a Model T crank because it was to wide.
We pour every kind of rod and insert out of every kind of motor there is, and all spec's call for never under .003 thousandths, and never over .012 thousandths, in which after that you will have greater chances of blowing thrust off the rod, and in turn takes the main part of the Babbitt in the rod.
The ideal thrust clearance being .003 to .008 thousandths.
When I get a chance to check rods from other companies, the thrust varies from over 1.500 to .030 thousandths under that, and all in the same set of rods that were sent.
When you have .020 plus side play, you can hear it in the running, not even counting alignment, in which you can always hear.
Herm, trying to learn something here, can you comment on the consequences of having excessive rod side play on a Model T?
I have heard that excessive rod side clearance on more modern, pressure oil system engines can result in excess oil being thrown around and resulting low oil pressure, but what about a splash system?
Imho 0.030" side play in a Model T rod won't hurt a thing.
Mark, it wouldn't hurt the oiling part, but the excessive clearance of .030 thousandths like Ted talks about, as if like he knew something about it, will beat the Babbitt flange to death, even worse if the rod is out of alignment, and as it breaks up, it fractures the Babbitt on the inside of the rod where it runs on the crank pin.
It is even worse when you get a set of rods these days and the flange is just laying on the side of the rod where it will eventually give up.
I have heard that excessive rod side clearance on more modern, pressure oil system engines can result in excess oil being thrown around and resulting low oil pressure, but what about a splash system? "END QUOTE"
You are very right Mark, loose bearings will also make an oil burner out of it.
Here is a good flange, and a bad flange.