need +.40 over pistons (1 Viewer)

[merbesfield]

The pictured piston is .75mm O/S.

It is a flattop piston for use w/ hi-compression 61040 (8/80 or later) cylinder head.

JimC, so does that mean they will not work for my situation? I have head from a 78-79 2f, block from an 84 fj60. According to the machine shop, the block needs to be bored +.40 and also, the pistons from my original block/head were domed. Someone here said that domed pistons were the performance ones and flats were not, they were incorrect? Thanks

 

[merbesfield]

Mark I got my ITM .040 pistons with rings for 34.80 each. Rings ended up being NPR (Nippon). Which from what Grant says are pretty good.


Bucks Engine Parts Warehouse
864-295-3360

item #
RY6150-040

Marshall, I called Bucks, they have 6 pistons, but he does not know if they are domed or flat toped and has no way of finding out. Do you know? Mark

 

[Degnol]

I have seen that post before but that does not tell me whether or not my pistons need to be domed or not does it? Are all blocks pretty much the same? If so then, logic would tell me that if my pistons were domed, they should stay domed? This is a PIA bc it has gone from a simple crack in the block to getting a new block, but the block is not the same year and needs to be over bored so now I have to trash perfectly good pistons just to get the oversized ones. s***. If I could just find a block from a 78 or 79 like the one I have that has not been over bored, but maybe I am dreaming.

1. Look at the casting number on YOUR head
2. From the number, determine the year(from the posted casting numbers and corresponding year
3. Have the bores of your block measured to see how much overbore you need to make them round
4. Order the correct pistons in the correct over size and give them to the machine shop
5. Let the machine shop do their thing

Not very difficult at all.

Ed

 

[FJ40Jim]

JimC, so does that mean they will not work for my situation? I have head from a 78-79 2f, block from an 84 fj60. According to the machine shop, the block needs to be bored +.40 and also, the pistons from my original block/head were domed. Someone here said that domed pistons were the performance ones and flats were not, they were incorrect? Thanks

The flattops would not be good w/ your 1980-earlier head.

Just call an autoparts vendor and get a set of 1mm O/S, 1975-1980 2F pistons on the way.

Or get a different 2F block that is not so trashed.

 

[merbesfield]

1. Look at the casting number on YOUR head
2. From the number, determine the year(from the posted casting numbers and corresponding year
3. Have the bores of your block measured to see how much overbore you need to make them round
4. Order the correct pistons in the correct over size and give them to the machine shop
5. Let the machine shop do their thing

Not very difficult at all.

Ed

Yes the machine shop measured and said they need to be bored +.30 or more so they said get the .40. I did not know about the head number. I will find the number tomorrow and then look to see which pistons should go with the head. Does the casting number tell me if they were the domed variety?

 

[Degnol]

Yes the machine shop measured and said they need to be bored +.30 or more so they said get the .40. I did not know about the head number. I will find the number tomorrow and then look to see which pistons should go with the head. Does the casting number tell me if they were the domed variety?

The casting number corresponds to a year(s) and the years tell you what pistons. Simple..................see?

Ed

 

[merbesfield]

JimC, Does this sum it up? Quoted from your previous posts:

"He's prolly referring to the 77-80 heads w/ 61031 casting. Slight improvement over 61030, plus it has the extra coolant temp ports cast over (one less crack/leak point).

The 81-87 heads in USA all have same number, 61040, though there are two distinct versions. 81-84 is 2F head, 85-later is 3F head. All 81-newer replacement heads are 3F.

Does this help any? What were we talking about?"

So, based on this and the year of the truck I pulled the motor from, the head number should be 61031. And according to Poser, the flat top pistons started in 8/80. So therefore, I would need domed pistons if this is the case. Have I got it straight?

 

[merbesfield]

Sorry, I missed some of the most recent posts. Ok, I think I need to find another block I guess. Are there negative reasons for using a block that requires over boring of +.40 or so? Or does it not matter from a mechanical reliability issue? Just do the necessary machine work? Just wondering and trying to learn. Is it hard to find a block for a specific year that does not require a lot of over boring? Or just keep looking? I have no idea if these things are easy to find or not?

 

[grant5127]

he does not know if they are domed or flat toped and has no way of finding out. Mark

Hell!..even a blind person could feel the top a piston and distinguish the difference between flat & domed......s***!

whats wrong with your machine shop not supplying the pistons? most do.... they need one before any boring can be done....

 

[grant5127]

there's nothing wrong with 40 over bores......the year of the block makes no difference unless you need holes for P/S mounting........ the piston type has to match the head.... domed piston needs open chamber head... flat needs closed chamber head..... get it?

 

[Degnol]

there's nothing wrong with 40 over bores......the year of the block makes no difference unless you need holes for P/S mounting........ the piston type has to match the head.... domed piston needs open chamber head... flat needs closed chamber head..... get it?

well said, Grant, maybe he will listen to you

ED

 

[merbesfield]

My machine shop says he does not have a source for the pistons so he asked me to get them so he could do the bore. Never done a 2F before. Yea, I know what domed pistons are, that is what mine are now. But a fellow mudder gave me an 84 block and my block was from 78 with factory ps and had the domed pistons. Another mudder had some flat tops but he did not know if they would work for me. yea PIA. What sucks is my f%&&^ing motor was fine except for a tiny hairline crack I found so had to tear the thing apart. I did not do the build, but the internals looked almost new so I had hoped to just find a block of similar year and just put it all back together, but obviously, that is not easy to do. thanks for the help and learning, remember that is what this forum is all about, right? mark

 

[merbesfield]

ps, did i tell you my mother is blind. ;(

 

[Degnol]

ps, did i tell you my mother is blind. ;(

Sorry about your Mom.

If you will just read, you will learn, young Merbesfield

If you don't, you will keep asking the same question over and over.

BTW, do you go to the library and scream questions expecting an answer? The answers are there, just requires some effort on your part.........or in this "library", just listen and read.

Good Luck on you project, dude.

Ed

 

[grant5127]

ps, did i tell you my mother is blind. ;(

Take her over to Bucks and straighten those cats out......

 

[Trollhole]

Mark if you really need a block I have one. No PS though. It's in my 40 and need to be yanked uot. Sorry for not calling today but ring me tomorrow. I'll get you set.

 

[vtcruiser60]

Jim and others.....I think what was stated below is the conventional wisdom.....but....

The flattops would not be good w/ your 1980-earlier head.

Isn't it true that you can deck a pre-80 series 2F head by .050-.090......and make it work just fine? I seem to recall that Mark W. did this with success. Here I am talking about mating the cast number 61031 head on say an 84 2F short block.

 

[grant5127]

Isn't it true that you can deck a pre-80 series 2F head by .050-.090......and make it work just fine? I seem to recall that Mark W. did this with success.

Yeah, Yeah, right......the allowable max limit is .100 then still there issues with alignment dowels and head bolts bottoming out.....why bother ruining a good head for future use when all that is needed is a set of pistons?

 

[vtcruiser60]

Yeah, Yeah, right......the allowable max limit is .100 then still there issues with alignment dowels and head bolts bottoming out.....why bother ruining a good head for future use when all that is needed is a set of pistons?

I am not needling you, just stretching the advice brought to bear here. A set of pistons has to cost more than having a machine shop deck a head + installation. Second, and maybe this is my inexperience, but I have never heard of head bolts bottoming out after decking. Wouldn't that possibly be corrected with washers.

 

[donny paradise]

I am not needling you, just stretching the advice brought to bear here. A set of pistons has to cost more than having a machine shop deck a head + installation. Second, and maybe this is my inexperience, but I have never heard of head bolts bottoming out after decking. Wouldn't that possibly be corrected with washers.

IIrc, Mark A had a post in the 60 forum about the need of thick washers @ .80 and andrewfarmer here on dowel shaving plus someone posted issues with cooperation with their local machine shop on removing more than .050 I dunno I just go for the pistons and be done with it, as in "no worries"