I'm still confused, which I6 is this?

[pritch]

I've asked this before, but the answer don't seem to jive with what I've found as I tear down the motor. The casting # is: S48675 and the stamped # is: FO204CJL. The answer I got before was '75 250 1BBL, 105 HP. My book says that the only real difference between the 230 and the 250 is stroke. It says the 230 is 3.250" and the 250 is like 3.580 or something. The book ain't in front of me so I'm guessing on the 250, but it was just over 3 and a half inches. When I measured the stroke on my motor, it was 3.250. It's easy to tell the diff. between 3 and a quarter and 3 and a half. So now I'm really confused because, again according to my book, they didn't make 230's in '75.

It has a broken piston. Looks like a ring came apart and banged around for awile. I think the PO rebuilt this motor (poorly) and broke a ring putting it together or not leaving enough ring gap. I think when the ring broke it took out the head because 1) the head shows no damage what so ever, while the top of the piston is all banged up, and 2) the head is a diff. shade of orange, so it wasn't painted at the same time at least. And 3) about 1/3 of the top ring was gone and 2/3 of the second ring was gone, along with about a nickel-sized chunk of piston from where the rings are. None of this was present inside the motor. I think the PO pulled the head and cleaned out the junk from on top of the piston and not seeing the missing rings or the side of the piston, figured he got away lucky with a new head. Lucky, too, that there don't seem to be any damage at all to the cyl. wall. I just need to come up with a piston. Are they the same for the 250 as the 230?

[Fred T]

From Chevrolet Inline Six-Cylinder Power Manua by Leo Santucci. 348675 shows for a 250, 66-79. The 230 was discontinued in 70.

To date the block, look for the casting date numbers. The should be aft of the casting number. From the rear of the block, first should be a conveyer number, such as CON2. Ahead of that should be the date such as F126, letter is the month A=Jan, L=Dec; first two numbers are date, last number is the last digit of the year. So the F126 would have been cast June 12, either '66, 76 or 86, depending on the casting number date range.

Pistons and rods appear to be the same for the 230 and 250. I can't tell for sure, and don't have access to a catalog right now.

Did you mike the cylinder wall? Thats about the only way to determine if it's damage when no scratches are visible.

[Rod]

Parts book shows 230 and 250 used the same connectiong rod...part number 3788435 from 1963-1972 / 4 cyl, 194, 230, 250 6 cyl.

The pistons show different part numbers. Thats all I got for now.

[pritch]

Thanks, guys. That date stamp on the block is: A 16 5 So that should be Jan. 16, '75? Everything is telling me '75 250, except for the stroke. I wonder if someone put in the wrong crank? The part # on it is:3820618N w/ date stamp J 26 3.

I just want to make sure I get the correct piston. This is just a stop-gap motor until I get the 327 built, but I can't do it just yet. What exactly makes a motor a 250 or a 230-I mean is it just a diff. crank? or do the pistons have a diff. location of wrist pin?

[Tx Firefighter]

Piston wrist pin location should be different between the two different strokes.

You really should do some reading on the forums over at www.inliners.org

Lots of those guys have found out that 307 V8 pistons are exactly the same as 250 I6 pistons, but much cheaper and easier to get.

[pritch]

Thanks, TX. That is an interesting site. I'll do some more research. I'm not really in a hurry, I have all winter to do this.

[jimfulco]

The piston height is different, and the 250 piston is dished. The 230 uses the same flat-topped piston as a 283, and the 250 can use a cheap 307 flat-top (a "rebuilder" piston that's .013-.020" shorter than stock) if you don't want a dished piston.

[Fred T]

Crank shows to be from a 194/230, time frame of 62-65.

I did a little more looking at the block configurations. Differences between the 230 and the 73-79 250 are very minor. Only thing I can see is the dipstick location. Forward (just aft of the fuel pump) is for a 62-67 Nova. Center (just forward of the aft lifter cover center bolt) is 63-67 car & truck. Aft (just aft of the aft lifter cover center bolt) is 68-88 car and truck.

It is entirely possible that someone rebuilt the block as a 230. Why, we will never know. Unless wanting to invest the money for another crank, I would rebuild it as a 230. But that extra stroke for the 250 does help a lot in the power department.

[pritch]

Thanks, guys. I think those are the answers. It's wierd, but it looks like a 230 crank in a 250 block. I will rebuild it as a 230, since I only need one of those pistons. It's not the dished type. I'll go for the flat-top 283 piston and see what happens. And maybe try and move up the time table some on the 327.

Thanks again.