6 cyl casting

[Dude68]

I am getting conflicting info researching casting number 3921968. It looks like an exchange motor that was put in this truck. In a 1968 C10. I have it pulled out, pistons removed. Looking for a head. If it was original motor it is 1968, but since it is not it could be a 230. Any suggestions.

[dmjlambert]

As I have found from researching my 6 cylinder engine 230 and 250 use many of the same parts including block. Are you interested in knowing if it is a 230 or 250? The shape of the top of the pistons is how you tell, dished for 250 and 4 dimples for 230. I have not looked at mine yet, I can't really see much through the spark plug hole. But since you have your pistons out do you still have them to look at? The factory made 230s and 250s in the same years, and put those into different vehicles depending on year and model, there were overlapping years like that.

[RustyPile]

I'm relying on my 60 year old memory of my racing days.. I raced a 250 cid engine only one year, 1972.. If I remember correctly, the 250 and 230 heads are interchangeable.. The 250 pistons are dished to cancel the increased compression ratio of the longer stroke 250 into the same sized combustion chamber. We ran flat top pistons, but I don't remember if they were 230 pistons or aftermarket pieces.

Just a bit of advice: -- don't bother with the integrated head.. It's a very poor design that is prone to cracking..

[Dude68]

Thanks. I will take a look at the pistons Monday. I may be able to post some pics as well.

['68OrangeSunshine]

Originally Posted by Dude68

I am getting conflicting info researching casting number 3921968. It looks like an exchange motor that was put in this truck. In a 1968 C10. I have it pulled out, pistons removed. Looking for a head. If it was original motor it is 1968, but since it is not it could be a 230. Any suggestions.

I looked on the Inliners forum:
www.inlinersinternational.org
#3921968 comes up as a 230/250 block for Chevy/Olds from '64 - '76

So it could be a 1968 250 L6.

Do you have the Dress code numbers stamped on the side tab aft of the Distributor hole?

[Dude68]

I wrote these down a while back, did not look at it after I pulled it yesterday because I had convinced myself that it was a 250 from some misinformation I had received. Anyway, this is what I had written down F1015TCK.

[Dude68]

There is also a tag on the driver side of the motor. I assume it was placed by whoever rebuilt it? I can make out three sets of numbers
010 040 010, assume they have to do with crank turn and cylinder bore.

[dmjlambert]

OK so glancing at the internet it looks like TCK means a truck 250 engine from Flint on 10/15/1970. https://media.lmctruck.com/Catalog_C..._Engine_ID.pdf
Don't know about those 3 sets of numbers on the tag.

['68OrangeSunshine]

F = Flint, Michigan
10 = October
15 = 15th
TCK = 1970 250

This is from the LMC catalog index. TC is also listed as 250 blocks in '67 and '68.

The ''F'' line in Flint was making L6 blocks in this period. The ''V' line at Flint produced blocks for V8s.

Sounds like a 250 to me. What misinformation?

['68OrangeSunshine]

Originally Posted by Dude68

There is also a tag on the driver side of the motor. I assume it was placed by whoever rebuilt it? I can make out three sets of numbers
010 040 010, assume they have to do with crank turn and cylinder bore.

I have heard Mercedes sometimes had dissimilar bores in an L4 engine, but I never heard of GM doing that. Also that's only 3 sets. What about the other 3?
Crazy...

[Dude68]

I found a page somewhere that said it was a 250, according to the casting number. I was doing a little more research for locating a head and came across the 230 or 250 on several other websites.
I appreciate that information. Just want “to know” what I have, the history behind the changes my grandpa made to his truck. I know the heads on 230-250-292 should work, but it’s nice to know what I have. People ask what you have under the hood and you say “I’m not sure if it’s a 230 or a 250” , it makes me feel like I didn’t kno my grandpa or know this truck.

[Dude68]

There are other numbers, I couldn’t make them out. I’ll get it clean and post a pic nxt week.

[geezer#99]

Did you know that you can up the compression ratio on your 230/250/292 by using a 194 head.

[Dude68]

I have seen a few posts referring to this. Is it a head from the earlier 194 L6 motor?

['68OrangeSunshine]

Originally Posted by geezer#99

Did you know that you can up the compression ratio on your 230/250/292 by using a 194 head.

I heard about that when I was rebuilding my first 292 in Yuma, in the Marines, in '77. My buddy said that he'd seen a dragster that had a 194 head on a larger displacement L6, and that, '' It ran like a R***d Ape until it blew up at the end of the track.''

[68bowtie]

If the head is off you could measure the piston stroke. Should be 3.25" for the 230, 3.53" for the 250.

[Dude68]

Here is photo of the engine tag. Another photo of the piston. It is dished. Appreciate all the help.