Last weekend a fresh rebuild short block arrived together with a lot of parts to build a Model T engine.
Before starting the assembly I check the short-block. It is tied but turn over but every other turn there was a little knock.
Here is what I found.
one of the bolts of the second rod near to the camshaft knocked the shaft every other turn.
I took all the rod bolts at the camshaft out and grind the heads.
Now knock is gone.
Your next knock is going to be, not if but when a small end breaks, the con rods are fitted backwards.
Is the crankshaft standard or long stroke? Normally, the rods should not hit the camshaft.
However on the bolts I've seen one side of the head is ground flat to fit toward the rod and the opposite side is tapered, presumably to keep from hitting the camshaft. If you grind those bolts be sure to weigh each one so that it doesn't throw the engine out of balance. They should all weigh the same amount.
Yes the rods are backward. The bolt at the small end should face the camshaft. However, that would not cause the rod to hit the camshaft. In order to fit correctly, the pistons should be removed and the small end turned around because the slot in the piston should face away from the camshaft and the bolt on the same side with the camshaft. If you do this, be sure to support the wrist pin while you loosen or tighten the bolt. I use a large phillips screwdriver and lay on the bench then tightening the bolt so there is no twist on the rod itself.
There is something really odd going on here.
Why does the Babbitt in the rods appear to be so thick?
Also,these appear to me to be the heavier early style rods.
If I'm right,who rebabitts those?Are you sure those are Ford rods?
Who assembled the short block?
I didn't see this. The rods are backwards, as you said.
The crankshaft should be stock and no I don't know who did the Babitt or who did the rebuild but I will take it apart again, check it and correct all this.
The block is sleeved and have ally standard pistons with rebuild rods and new rod bolts and nuts.
Thanks again for watching it.
Makes no difference which way the pinch bolts point Andre, as long as they are all the same.
The reason the bolt heads hit Andre, is they are not Model T bolts.
I was thinking that too because of there length. All the cotter pin holes are to high on the bolts and don't fit the castle nuts.
I will take it all apart and rebuild it as it should be.
Found some other issues, camshaft gear 180° turned, damage to the camshaft nut by not using the right tool ...
WOW!! Herm, After all these years of nothing but facts in regard to rod fitting presented to you, you are still adamant that Ford and engine design engineers have it wrong. good on ya!!
In the first picture the sleeve looks like it goes all the way to the bottom of the hole, with no lip to set on. I thought that standard practice was to leave 3/16-1/4 of lip, in the bottom of the cylinder, for the sleeve to rest on, to insure that the sleeve never drops into the crank. Is this a concern?
The claim that the small end of a rod could break if the rod is turned the wrong direction is interesting - has anyone ever seen any such break occur in the small end?
I’m trying to understand the statement about the cam gear being out 180 degrees. Just like the orientation of the pinch bolts being the source of the interference. After 45 years of building T engines I’m sure I can still learn something
by turning the gear 180° the ignition will be turned 180°.
Cylinder 1 will be 4, 2 will be 3, 3 will be 2 and 4 will be 1. The spark wires must be connected this way.
As you know it will be no problem but when some one else is working on the engine it will take him a while to find it.
This was not really my problem. My problem was more the way the gear and the nut was put on the engine, it should all be new.
Give the crankshaft one more turn and I bet you will find the cam gear to be correctly indexed.
As for getting a re- built short block back with the rod bolts hitting the cam... The price you paid probably bought the rebuilder a new pair of clown shoes...
I beg to differ. Either way #1 piston is at the top for every 1/2 rotation of the camshaft. The spark timing is determined by camshaft. Therefore, no problem
I’ll admit that the cam nut installation is a bit “brutal “!!!
I would be inclined to remove, dress it with a file, and reinstall. While I had it off I would make sure the surface where the modern lip type seal runs was in first class condition!! That would be my grounds for replacement
and right about now, Andre is slapping his forehead...
we've all been there!
A photo of a broken paw.
Back in 2013 Herm even had one of his rebuilt engines at 600 miles pop 2 pinch bolts from the rods
but of cause he blamed the bolts.
Andre, try to find Ford bolts, they will miss the cam.
We have always used New lock washers on the pinch bolts, Cotter pins will never hold the bolt safely.
Frankie, It has nothing to do with engine design. You just seen the picture in the book with them pointing to the cam, which is all right also, but has nothing to do with any weakness. With all the engines we have built, I never have pointed them to the cam, and with well over 33,000 spun poured before we no longer kept records, I have never even seen a broken small end in any of the cores we got in. I know you came up with that being a problem, but you can just leave something like that to the big Boys down at the Tavern.
I just replaced the gear nut and turned the camshaft 180°, all the posts about the timing gear made me thinking and you are all right. It make no difference, just the marking points need to be in line.
I will change the bolts on the rods and leave the rods as they are.
That's is right Frankie, and the repro bolts did break, and they were not hardened right, and two shattered, and the other two snapped off when we took them out to replace with Ford bolts.
It also was not my idea to use them in the first place, the customer bought them, and brought them to me.
Looks to me Frankie that the broken rod you are showing is an after market, with a thin wrist pin wall. I have seen many of those, they are junk and go to the iron pile.
Try again Frankie, you haven't sunk my ship yet!
Your rebuild left your shop with the rods the way you fit them, backwards, pinch bolts tensioned to your satisfaction, for a bolt to fail it has to endure extra stress, if the bolt was of a lighter grade and broke 600 miles or several months later, it couldn't handle the extra strain you imposed on it the way you fitted them.
It's simple engineering Herm.
That 2 wrongs don't make a right!
As for that rod, it's still hanging on my shed wall and is a Ford rod.
Even a kid in first year of high school geometry can see that if you flip a rod that the stress would now be on the paw clamp pinch bolt!
The right way to minimise the stress on the small end
Sorry, but I have to disagree.
All the best
Regardless of orientation of the wrist pin bolt. I fail to see how breakage on a small end could be any more than fatigue of 90 year old parts, or over torque from a mis-calibrated wrench. I would love to see actual engineering on this issue (not old books, “I’ve always done it that way” statements, or other armchair-engineering)!
However, I have always installed wrist pin bolts according to the Ford manual.