Time for a rebuild

Well after fighting with the little V6 in my 70 cj6 for a time now I decided to go a little deeper. Last weekend I took off the intake and heads saw no major problems other than some carbon build up.:?Went back out to my shop today to do more looking and saw this:?


the first piston I think is of stock type the other (the only one) is something else.SOOO I start taking her down a little further, pull water pump and timing cover to find out the fuel pump ex centric had been worn way down and instead of buying a new one PO welded it up and put it back in and it had been shaving it back down since(picture later).After finding this I took her all the way down to the block .Found scored bearings(main and rod) pistons with minor scoring and cylinders to match.




Oh and about a half inch of sludge (the glittery type) in the bottom of the pan.

So Know I git to start a rebuild. Thought I would share my joy with you all and let you know the ???? are coming soon.R)

 

The first pic shows a 231 style piston. The 225 style is the second pic....

 

Ok so I have five 231 pistons and one 225 piston good thing to know. Will all be getting replaced but now I know what a stock piston looks like.

 

The 1st pic with the dimple in the middle is a 225 piston (thats what was in my stock motor) the flat dish is a 231 piston.

 

IIRC the 231 piston is 0.050" larger in diameter than the factory 225 piston, but otherwise they should be interchangeable. Have a dial caliper? Measure the diameter of all your pistons - that would be interesting. Why would someone fit just one 225 piston? 50-over is not a common size for replacement pistons. Obviously it's a patch-up job... I presume you've checked the casting numbers and this is really a 225 block.

Also, if the block is already 50 over, and you have bore damage, you might start thinking about finding either another core or a good used engine. Lots of guys are running a 231 from a RWD Buick passenger car...

Oh, reading Mike's comments - if you have one 231 piston, that would be more consistent with a patch-up scenario. One really bad cylinder was bored out 50-thou and a 231 piston fitted.

 

I will be taking my parts to work this week and putting them in the parts washer. Then I'm going to do some measuring and see what I've got.I will post up info as I go so I can get suggestions from the V6 guru's as to where to go with this engine.Oh and I did check the numbers before and came up with a 225 # I might check again numbers much easier to see with the block in the bed of the pick up.

Ok went and rechecked #'s
Block#991503 1967-74
Head# B 1376348 1967-74
Crank#1378351 1975-76

 

Also the picture of the fuel pump ex centric

 

That's interesting. The last 3 231's I pulled apart had the dimple/knob in the middle but my 225's didn't...

 

Pat Ganahls V6 book even makes reference to the fact that the stock 225 pistons look like an ashtray. All the later after market pistons to my knowledge are dished with no dimple in them.

 

I know. I was one of the originals on this site to post the ISBN # for that book. Just making an observation of what I have seen in the motors I've rebuilt or torn apart. I agree, almost all aftermarket pistons will be dished.