The Ford Barn

classic car repair · 06-28-2023, 07:11 PM

I have a flathead V8, 1938 85 truck, looking for new pistons - STD, piston has 91A on the piston, mic out at 3.06-3.08, I was wrong, they are dome type piston, 3 rings only, having a hard time fine a place to buy them, STD piston, Need stop, if someone can help and tell me who sale them. You can E-Mail me [email protected]
Thank You Lee

Ken/Alabama · 06-28-2023, 08:13 PM

Not sure I’ve seen a 91A piston with a flat top. I thought by 1939 they were all dome top.

Lawson Cox · 06-28-2023, 08:20 PM

I'm with Ken.

Brian · 06-28-2023, 08:50 PM

the above answers are correct, inasmuch as a 1938 engine should be equipped with dome top pistons. Have a look at the cylinder heads- see how they are domed to provide clearance for dome top pistons? Try all the regular suppliers for STD 3 1/16" domed pistons.

Bored&Stroked · 06-29-2023, 06:59 AM

Post a picture of your pistons and heads (the chambers) - and what your block's bores look like.

As others have noted, these engines usually come with domed-top pistons - with heads that match. If the engine had true flat-tops and the heads are domed-top, then you had very little compression and the engine would run very poorly. As Brian noted, if it has the pistons that should be in it, then it is easy to find 3 1/16 pistons (stock Ford 221 cubic inch pistons).

If you have the engine all torn down, the bores need to be measured with an accurate dial-bore gauge to see if it is possible to use STD pistons and re-ring it, or if it really needs to be over-bored for a bigger oversize piston - like .030 over.

I've never taken apart an older engine that didn't need to be over-bored (they ran the heck out of these things before and during WWII), but I'm a bit of a perfectionist. If I see too much piston to bore clearance, taper, out of round, etc - I put new pistons/rings in it.

nickthebandit · 06-29-2023, 07:34 AM

Sponsored Links (Register now to hide all advertisements)

Try Foundry Street classic Parts. 1-413 -283-7620. Brian is there on Fridays and
Saturdays. He has an untold amount of early parts available.

classic car repair · 06-29-2023, 08:24 AM

you are Right and I recheck after I clean the top off, they dome piston

classic car repair · 06-29-2023, 08:25 AM

They are dome top piston, I had to recheck and clean off the top, Sorry, but you are right

classic car repair · 06-29-2023, 08:35 AM

I remic the piston and they are 3.06 but I was wrong on the piston top, I recheck and clean off and they are dome type

classic car repair · 06-29-2023, 08:37 AM

I recheck and I was wrong, they are dome type

Ken/Alabama · 06-29-2023, 01:28 PM

Barnfind08 here on the Ford Barn will probably have them New Old Stock.

06-28-2023, 07:11 PM	#1
classic car repair Junior Member Join Date: Jan 2023 Posts: 15	piston I have a flathead V8, 1938 85 truck, looking for new pistons - STD, piston has 91A on the piston, mic out at 3.06-3.08, I was wrong, they are dome type piston, 3 rings only, having a hard time fine a place to buy them, STD piston, Need stop, if someone can help and tell me who sale them. You can E-Mail me [email protected] Thank You Lee Last edited by classic car repair; 06-29-2023 at 08:23 AM.

06-28-2023, 08:13 PM	#2
Ken/Alabama Senior Member Join Date: May 2010 Location: Alabama Posts: 3,395	Re: piston Not sure I’ve seen a 91A piston with a flat top. I thought by 1939 they were all dome top.

06-28-2023, 08:20 PM	#3
Lawson Cox Senior Member Join Date: May 2010 Location: Above the gnat line in Georgia Posts: 7,082	Re: piston I'm with Ken. __________________ Life is like a roll of toilet paper. The closer to the end, the faster it goes. It is better to be seen, than viewed. "We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm".

06-28-2023, 08:50 PM	#4
Brian Senior Member Join Date: May 2010 Location: Masterton, New Zealand Posts: 3,998	Re: piston the above answers are correct, inasmuch as a 1938 engine should be equipped with dome top pistons. Have a look at the cylinder heads- see how they are domed to provide clearance for dome top pistons? Try all the regular suppliers for STD 3 1/16" domed pistons. __________________ Unfortunately, two half wits don't make a whole wit!

06-29-2023, 06:59 AM	#5
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,723	Re: piston Post a picture of your pistons and heads (the chambers) - and what your block's bores look like. As others have noted, these engines usually come with domed-top pistons - with heads that match. If the engine had true flat-tops and the heads are domed-top, then you had very little compression and the engine would run very poorly. As Brian noted, if it has the pistons that should be in it, then it is easy to find 3 1/16 pistons (stock Ford 221 cubic inch pistons). If you have the engine all torn down, the bores need to be measured with an accurate dial-bore gauge to see if it is possible to use STD pistons and re-ring it, or if it really needs to be over-bored for a bigger oversize piston - like .030 over. I've never taken apart an older engine that didn't need to be over-bored (they ran the heck out of these things before and during WWII), but I'm a bit of a perfectionist. If I see too much piston to bore clearance, taper, out of round, etc - I put new pistons/rings in it.

06-29-2023, 07:34 AM	#6
nickthebandit Senior Member Join Date: May 2010 Location: Shippensburg, pa. Posts: 513	Re: piston Sponsored Links (Register now to hide all advertisements) Try Foundry Street classic Parts. 1-413 -283-7620. Brian is there on Fridays and Saturdays. He has an untold amount of early parts available.

06-29-2023, 08:24 AM	#7
classic car repair Junior Member Join Date: Jan 2023 Posts: 15	Re: piston you are Right and I recheck after I clean the top off, they dome piston

06-29-2023, 08:25 AM	#8
classic car repair Junior Member Join Date: Jan 2023 Posts: 15	Re: piston They are dome top piston, I had to recheck and clean off the top, Sorry, but you are right

06-29-2023, 08:35 AM	#9
classic car repair Junior Member Join Date: Jan 2023 Posts: 15	Re: piston I remic the piston and they are 3.06 but I was wrong on the piston top, I recheck and clean off and they are dome type

06-29-2023, 08:37 AM	#10
classic car repair Junior Member Join Date: Jan 2023 Posts: 15	Re: piston I recheck and I was wrong, they are dome type

06-29-2023, 01:28 PM	#11
Ken/Alabama Senior Member Join Date: May 2010 Location: Alabama Posts: 3,395	Re: piston Barnfind08 here on the Ford Barn will probably have them New Old Stock.