YJ engine code?

hunterdan

hunterdan

Well-Known Member
Joined
Apr 13, 2009
Location
Morganton,NC
I have a 87 YJ with a straight six. Bought oil filter for it and it does not fit. I think it should be M20x1.5. Turned out to be 11/16" I believe. Block stamp reads 307C21
Any idea what engine it is/ year...
Someone installed a Edelbrock 1406 4 barrel with offenhauser intake and a header
 

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What engine lookup did you use, and/or what filter did you end up with?

I'd expect that to be a 4.2/258 motor, which I don't believe had metric threads.
 
grapehead said:
What engine lookup did you use, and/or what filter did you end up with?

I'd expect that to be a 4.2/258 motor, which I don't believe had metric threads.
Click to expand...
I got filter at Napa based on what I thought was the original motor, 258/4.2. 87 yj. It did not fit. I believe filter # was 1620. From what I read 87 was year they switched to M20x1.5. Napa guy said when he worked for jeep back then that early in the year ones had 11/16 and later had M20x1.5. I ended up needing the 11/16 one #1626. After more reading about engine block codes...
My numbers on machined block area passenger side are 307C21
I think first digit is year so maybe 83 or 93?
07 might be month
C = 258
21 is day of month
*****Not sure about any of this and hoping someone can clarify.
 
Oh true, 87 was a transition year. Could be that someone blew the original motor in your jeep and swapped in an earlier block if that 83 year is correct
 
grapehead said:
Oh true, 87 was a transition year. Could be that someone blew the original motor in your jeep and swapped in an earlier block if that 83 year is correct
Click to expand...
Yep maybe. I just talked to a few keep dealers and guess what? They know nothing about anything. They can't even tell me how to figure out what !!!!!!! Engine I have. Someone has to know how to decipher the block code 307C21. Any ideas y'all? How the !!!! Would anyone rebuild an engine? This is deja Vu. I'm remembering all the !!!!!!! Problems I had with my last one nowšŸ˜¬šŸ˜”šŸ˜–
 
Thanks for the link, Turns out my engine is definitely a 61,70,79,83 or 93
It also says I need to find some other numbers that are cast into block to figure out which of the above years it is. It's almost like a treasure hunt:bounce2:
 
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