So, I put a 5.5 head on my stock 1929 Model A 4 banger. Then I started to get some knocking - ok, I see people shaking their head yep. I assume the bottom end could not handle the higher compression. Correct me if I am wrong. But if that is the case, can I order a set of babbitts, or do they need to be "custom fit" - meaning I will need to pull the rods and have someone make babbitts to fit, then reinstall?
Can Rod Babbitts be ordered
- Thread starter Dkrahn
- Start date
Y-Blockhead
Well-known member
You sure you are not hearing "pinging" (detonation?)? With a higher compression, you don't need as much spark advance. Try backing off your timing. Your engine should be able to handle 5.5 compression ratio.
Then if you still have a knock, try adjusting your bearing clearance by removing shims.
Engine will have to be disassembled and babbitt will have to be poured if removing shims doesn't work. Babbitt can not just be replaced like modern insert bearings.
Then if you still have a knock, try adjusting your bearing clearance by removing shims.
Engine will have to be disassembled and babbitt will have to be poured if removing shims doesn't work. Babbitt can not just be replaced like modern insert bearings.
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Gene F
Well-known member
Snyders sells rods. You need a micrometer, because you need to pull your pan, and head so you can measure before ordering. I had an engine once I did this to. Checked the shims/fit of the main journals., Reused the pistons and rings. Had a local machine shop hone and slip the piston pins in, then aligned the rings and slipped the assemblies back in. Gotta be the right kinda machine shop that doesn't mind taking in something different, and listening. Whatever you do don't start out asking how much $.
The rule of thumb is that the rods wear twice as fast as the mains, due to surface area size.
And now all the people on here will start hollerin' !!!
The rule of thumb is that the rods wear twice as fast as the mains, due to surface area size.
And now all the people on here will start hollerin' !!!
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ModelA29
Well-known member
Babbit bearings are poured in place then machined. Think of them like solder applied and stuck to the metal. You can get rods but need to have a bare block sent out and have the babbit installed and machined. The center main seems to go first. I would suggest inserts for the mains if they need to be redone. The block still has to be disassembled and machined but in the future you can swap the insert bearings without additional block work.
David in San Antonio
Well-known member
If the engine is pinging, you might try higher octane gasoline (in addition to checking the timing). My engine with 6.5:1 head does not ping or knock even when the timing is fully advanced, as long as the engine is not lugging.
P.S. Murphy gas stations (Walmart brand) has 90 octane non-ethanol fuel here in San Antonio. Not sure if that’s at every Walmart gas station.
P.S. Murphy gas stations (Walmart brand) has 90 octane non-ethanol fuel here in San Antonio. Not sure if that’s at every Walmart gas station.
Joe K
Well-known member
Vince Falter discusses technically the "timing" of the Model A engine. Vince's opinion is that the Model A design was faulty in allowing too much "span" at the extremes of the spark adjust lever which has inherent about 40 degrees adjustment. An excess that was corrected in the Model B centrifugal advance distributor.
Timing is discussed at https://www.fordgarage.com/pages/timingiseverything.htm including a video reference worth watching.
The ever important "front cover" variations - and discussion of the "blank" cover which could be drilled and tapped for engine of destination is at https://www.fordgarage.com/pages/timingcovers.htm
Joe K
Timing is discussed at https://www.fordgarage.com/pages/timingiseverything.htm including a video reference worth watching.
The ever important "front cover" variations - and discussion of the "blank" cover which could be drilled and tapped for engine of destination is at https://www.fordgarage.com/pages/timingcovers.htm
Joe K
nkaminar
Well-known member
If you run the engine with the timing too advanced you will get the pinging, but eventually that will lead to the rod bearings breaking or the clearance being too great (rod knock). A higher compression head will require less ignition advance.
Here is how to set your advance when driving the car: You want to discover the knee, where an increase in one click of advance will not cause the engine to run faster and a retard of one click will cause the engine to slow down a bit. Pick your favorite test grade and with the transmission in high gear and the throttle open, starting with the lever near the top, advance the timing one click at a time until another click will not improve engine performance. Then retard one click. That is the knee and where you should be running most of the time. You can advance one click when cruising down a level road at a constant speed. Or you may want to retard one click if putting a heavy load on the engine at a low rpm.
Here is how to set your advance when driving the car: You want to discover the knee, where an increase in one click of advance will not cause the engine to run faster and a retard of one click will cause the engine to slow down a bit. Pick your favorite test grade and with the transmission in high gear and the throttle open, starting with the lever near the top, advance the timing one click at a time until another click will not improve engine performance. Then retard one click. That is the knee and where you should be running most of the time. You can advance one click when cruising down a level road at a constant speed. Or you may want to retard one click if putting a heavy load on the engine at a low rpm.
rotorwrench
Well-known member
If you have a rod bearing that is too loose, you first have to find out the surface condition and the size of the worn journal. If it's smooth and still concentric that's only half the battle. Rods come in specific sizes so a person either matches a size for a .0015 clearance fit or they have to use an undersize that can be machined to a .0015" fit with shims installed. Moving shims on an unworn size affects concentricity of the babbitt.
The great thing about the rods is that they can be tinned before the pouring of new babbitt. The babbitt sticks better to a tinned surface making them easier to get good results when align boring the bearing surface.
Flathead engines require less advancement of the spark timing than OHV engines due to the turbulence in the cylinders. Ford's owner instruction manuals have a good procedure for operating the spark control. Since it's not automatic, the operator has to fully retard the spark for starting then advance it about half way in the quadrant. For lower speed driving, the spark advance can be increased a little but the only time an operator may need full advance with with higher than normal speeds such as passing a car. For load control such as pulling up a hill, the spark will need only to be retarded enough to eliminate spark knock or the pinging of detonation.
The great thing about the rods is that they can be tinned before the pouring of new babbitt. The babbitt sticks better to a tinned surface making them easier to get good results when align boring the bearing surface.
Flathead engines require less advancement of the spark timing than OHV engines due to the turbulence in the cylinders. Ford's owner instruction manuals have a good procedure for operating the spark control. Since it's not automatic, the operator has to fully retard the spark for starting then advance it about half way in the quadrant. For lower speed driving, the spark advance can be increased a little but the only time an operator may need full advance with with higher than normal speeds such as passing a car. For load control such as pulling up a hill, the spark will need only to be retarded enough to eliminate spark knock or the pinging of detonation.
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NOTICE: about buying refurbished rods:
The "correct" way to size Babbitt bearings is to use .010 .020 .030 .040 etc. under sizes.
That way you can order a refurbished rod in correct size.
In the past not every rebuilder followed this convention. Some only removed enough metal to "clean up" the journal.
As a result #1 rod might be .008, # 2 .017 etc. (this also affects engine balance)
When they do this it makes it more difficult to find correctly sized rods. You then have to special order custom sized rods.
Main bearings are poured and machined as part of the block so ordering main bearings is not possible!
The "correct" way to size Babbitt bearings is to use .010 .020 .030 .040 etc. under sizes.
That way you can order a refurbished rod in correct size.
In the past not every rebuilder followed this convention. Some only removed enough metal to "clean up" the journal.
As a result #1 rod might be .008, # 2 .017 etc. (this also affects engine balance)
When they do this it makes it more difficult to find correctly sized rods. You then have to special order custom sized rods.
Main bearings are poured and machined as part of the block so ordering main bearings is not possible!
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Osage Orange
Senior Member
When I rebuilt my '29 standard coupe's engine in 1968 I ordered four re-babbitted rods from J.C. Whitney after taking the block to be re-babbitted after it was heated up so that a crack in the water jacket could be brazed and sealed. The rods were .010 under and each had a little babbitt material on the big end for the express purpose to remove material from the heaviest ones to match the lightest one, which I did. The block was already .060 over so I asked the machinist to remove the wear lip at the top of the cylinders and lightly bar-hone each cylinder and measure. The bores were still just a little over .060 so I stuck with the same pistons. Ran like a top, lots of power, reliable as a Swiss watch.