So there must be 2 different size pushrods for a 172 motor?

[marlin54]

I am trying to use a 172 motor I just picked up for parts to fix my other 172 motor...I have run into an Issue with pushrods...I need to use the parts from both to get a complete working motor..I need to use a tappet from one and as you can see the thinkness of the part that runs on the lobe is thicker on one ..and also the pushrods are different thickness too,,,I think one is 1/4 inch and the other one is 5/16....and also a piece of the rocker shaft cast piece broke.....I think one motor is newer as 1 has a spin on oil filter and the other not...so I was reading that if you order pushrods you have to also match the adjusting screw to the same so eveidently the thread is the same? Can I mix match these rocker parts and the valve train parts ? I cant remenber as I took one motor apart months ago..and nowmthisone ..but it seems to me the 5/16 bigger pushrod used th thin tappet and the 1/4 inch saller pushrod came with the thicker tappet? So either way if I can mix match the rocker shaft parts ,,and the pushrods and tappets?

 

[marlin54]

I am trying to use a 172 motor I just picked up for parts to fix my other 172 motor...I have run into an Issue with pushrods...I need to use the parts from both to get a complete working motor..I need to use a tappet from one and as you can see the thinkness of the part that runs on the lobe is thicker on one ..and also the pushrods are different thickness too,,,I think one is 1/4 inch and the other one is 5/16....and also a piece of the rocker shaft cast piece broke.....I think one motor is newer as 1 has a spin on oil filter and the other not...so I was reading that if you order pushrods you have to also match the adjusting screw to the same so eveidently the thread is the same? Can I mix match these rocker parts and the valve train parts ? I cant remenber as I took one motor apart months ago..and nowmthisone ..but it seems to me the 5/16 bigger pushrod used th thin tappet and the 1/4 inch saller pushrod came with the thicker tappet? So either way if I can mix match the rocker shaft parts ,,and the pushrods and tappets?

Is it possible that there is only 1 size tappet and the ones on my motor are just all worn down from bad oil ?

 

[shaun wallace]

The small one is solid and the thick one is hollow, the ends are spun welded on.

 

[marlin54]

The small one is solid and the thick one is hollow, the ends are spun welded on.

So I do have 8 of the smaller ones ,,,and so then can I use the smaller ones on either of the 2 rocker shafts? And can I borrow parts of the other rocker shaft to fix mine >

 

[marlin54]

The small one is solid and the thick one is hollow, the ends are spun welded on.

Is there 2 different tappets or the thinner one is just wore down? thanks

 

[JMOR]

I don't have parts in hand, but expect that seats in both rocker arm and tappet are different for large vs small push rods,

 

[John P.]

Here is the note out of the parts catalog:

Notes:
Valve Post;
If replacing a 1/4'' OD push rod, must order push rod P/N C0AE6565C, adjusting screw P/N 87801302 & tappet valve P/N F3JL6500AA.
If replacing a 5/16'' OD push rod, order new push rod P/N C0AE6565C only.
(Prod Date) After 01-Jan-1953

 

[JMOR]

Here is the note out of the parts catalog:

Notes:
Valve Post;
If replacing a 1/4'' OD push rod, must order push rod P/N C0AE6565C, adjusting screw P/N 87801302 & tappet valve P/N F3JL6500AA.
If replacing a 5/16'' OD push rod, order new push rod P/N C0AE6565C only.
(Prod Date) After 01-Jan-1953

Guess I'm kinda slow today, but is this note referring to replacing a 1/4 with 1/4 and 5/16 with 5/16 or replacing 1/4 with 5/16 or replacing 5/16 with 1/4? Seems unclear to me.

 

[John P.]

I read it as the 1/4” was superseded by the 5/16”.

 

[JMOR]

I read it as the 1/4” was superseded by the 5/16”.

OK, makes sense.

 

[John P.]

So if you have to replace the 1/4” pushrod, you now need to buy a 5/16” pushrod, the larger 5/16” rocker arm adjusting screw, and the new larger 5/16” lifter.