2F head advice

Joined
May 19, 2021
Messages
22
Location
Boise, ID, USA
Hi all!

I'm beginning a rebuild on a casting #61010 2F block, serial 05331 presumably from '75. It has flat-top pistons that I would have to assume were put in by PO, most likely all going to be replaced...

Heres the question. In the purchase of this block (and 2 others) I was given 2 cylinder heads. One of which casting 61030, other 61031 and from what I can read NEITHER of them belong on a block with flat top pistons. However I can definitely tell that the 61030 was on this block previously.

Should I put in the effort to find a closed chamber head? (61010 or 61040 I think?) Assuming that the head(s) I have are in rebuildable state, should I just find some domed pistons and go that route? I understand they're pretty hard to find.

Thanks
 

Dizzy

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Joined
Feb 5, 2018
Messages
2,331
Location
Santa Fe, New Mexico
I thought that you had to go .020 over to get an OEM flat topped piston. Otherwise, aftermarket were available, for either configuration, domed or flat, last that I checked.

I'd get the head professionally checked for cracks, before putting much money into it.

If I ever have valve guides done, I'd make them be positive-type (press-on) valve stem seals, on an early 2F or F.
 
Joined
May 19, 2021
Messages
22
Location
Boise, ID, USA
Better make sure the PO hasn't already shaved this head to match the flat tops.
Not sure how you could tell by looking at it sorry.
I'll have to check... No idea either. To be frank, not even sure what a head being "shaved" implies. Research time ;)

edit: that was simple enough and I shouldve just googled it before posting this. Hah
 
Joined
Nov 25, 2014
Messages
843
Location
Western victoria Australia
I think if the flat tops are standard size, and the open chamber head is untouched the compression ratio will be only around 6 to 1.
The head will need a couple of mm [total guess] machined off it to bring up the compression ratio to where it should be. Calculating the exact amount to machine is the tricky part. Maybe the machine shop might have an idea?
 
Joined
May 19, 2021
Messages
22
Location
Boise, ID, USA
I think if the flat tops are standard size, and the open chamber head is untouched the compression ratio will be only around 6 to 1.
The head will need a couple of mm [total guess] machined off it to bring up the compression ratio to where it should be. Calculating the exact amount to machine is the tricky part. Maybe the machine shop might have an idea?
Mmmm I think I'm starting to understand! I'll have to do some measuring, or let the machine shop do it, and see where the cc's would be at with the 61030 or 61031 to achieve a 7.8:1 CR. Thanks for the patience
 

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