345 Vibrations

[ffemt_123]

First off I am new to the International/Scout world so take it easy on me.

I bought a 1974 Scout II with the 345 and 3 speed automatic a while back. When I got the truck it was smoking like a freight train so I knew it had to be rebuilt. When checking around for a rebuild kit, a very competent machine shop had a complete engine that was already built. The story on the motor was he built it 4 years previous for a guy that never picked it up and he wanted to get rid of it. He said he went completely through the motor and put all new valvetrain parts, 3 connecting rods, new pistons and turned the crank 10/10. This engine came out of a heavy duty truck with a standard shift behind it. It also included the original balancer that came on the engine with it.

So I installed the engine and the first thing I thought was that the engine was going to shake itself apart. So the set up I had was the original engine balancer and my flexplate from the Scout for the automatic transmission. So a call back to the machine shop and he advised to change the balancer to the one that came on the Scout. So this is what I did and it made absolutely no difference. At this point the machine shop was out of answers.

Does anyone know how International balanced these motors? Was the crank "0" balance and the external parts balanced to each other or was the crank, balancer and flexplate all balanced as a unit?

I have definitely run out of options and really want to keep the original motor but these vibrations have me stumped.

 

[Dealbreaker74]

The balancer on the snout is keyed and can only go one way. But the flywheel (or flexplate in your case) has a circle of bolts and one locating pin. Both the flywheel and flexplates are externally balanced and can be used in other 345s, but the locating pin must be lined up correctly in order for it to do its job.
I once had a flywheel resurfaced, and the monkeys at the machine shop pulled the locating pin so they didn't grind it off. Unfortunately, they didn't put it in the same place, and after I got the trans all hooked back up, I had a situation like yours.
You'll have to pull it all apart and try to id which hole the pin should go in.

 

[Robert Kenney]

Db74 is giving good info. I just want to add some with respect to your question on how these are balanced by IH.

Did you receive the original flywheel that it should have been balanced with? If so install it and start it. Bolt the transmission up, even if you don't have the trans drive shaft coupled. See if it is better.

More on balancing. You must take this next paragraph with a grain of salt, because only IH knows the balancing process used in their plant.
All reciprocating and rotating parts (pistons, rods both ends) are manufactured and kept to weight specifications. In a set of 8 for each engine? I can't say for sure but at least to some published weight specification for that time period.
The crank with Bob weights on the crank rod journals and with the front damper and flywheel or flex plate are spun as an assembly and lightened accordingly to achieve a maximum allowed error of balance.

More.
on your op you wrote that they replaced 3 rods and pistons. What you don't say is if the parts were match balanced. What I mean is that were all 8 of the rods matched end for end. All small and all big ends matched in the set. Was the crank then Bob weighted and balanced with the correct flywheel and balancer?

In the big picture you should be able to replace a damper and or flywheel with service parts and suffer no ill effects that you would notice during normal driving. Awhile the balance May not be perfect, you would not really notice.

In your case, either the flywheel is indexed wrong ( db74 wrote same) or the parts were way off

 

[ffemt_123]

I do not have the original flywheel that came on the engine as this part was not brought to the machine shop by the original owner, so I cant test it this way. The machine shop that I got the engine from did not balance the rotating assembly but did replace the rods with service parts. I am beginning to think that the flexplate is indexed wrong as well, because the vibration does not change with the original balancer that came on the truck or the balancer that came on my Scout. So that kind of points directly to the flex plate. My Dad was helping me assemble the motor and neither one of can remember if there was a pin in the crank for indexing the flexplate. What I can tell you is I will know for sure next week! Ive got the crank that came out of the scouts 345 and the pin is in place, so I can reference this.

 

[Dealbreaker74]

I don't remember if all of the holes in the crank flange are threaded...maybe Robert knows...? Anyway, if one of them isn't that's where the roll pin goes. If they are all threaded, look for one that's had the least wear.
On my deal, I was able to look at the flywheel and see that all but one hole had lots of scar tissue from previous lock washer fastenings. The one that looked like it had only seen a bolt installed once was where the pin went. So I tapped it out of the wrong hole and into that hole. Vibration fixed.
Maybe this pic will help. Its of another 345 I built but has a flexplate like yours. It should give you something to compare.

 

[codeman]

Just wondering, but does the hole on the outer edge of the flex plate, in line with the roll pin,have anything to do with the alignment? Almost looks like the hole is there for that reason.

 

[Robert Kenney]

Might have something to do with fixturing during the mfg process. The real clocking indicator will be the big weight riveted to the outer rim on a perpendicular radial line from the roll pin to the outer diameter. Easy to see in db74's photo. That it the heavy side. If you look at your crank, one hole will not have threads that is the index point for the roll pin to go in. Now assuming (ass-u-me) you have the tf727 trans you will have a spacer that the goes between the crank and the flex plate. You need to index the roll pin to the correct through hole.