Curious about the XS1500 J block, like the meaning it and etc..

[Robby321]

OK we all know all about the Merc XS1500 IL6 Stack "J" block, but do any have any knowledge then of why the "J", stamped, cast, upright, sideways, etc.?

Little bit info why as owned a few, and oh well..on my last thing in the bucket "list" still a wondering? Couple pix.

[MN4V]

Could be that J was the destination in the APBA OPC class that the motor ran in. Family J and Sport J classes.
Mark N

[Robby321]

Could be that J was the destination in the APBA OPC class that the motor ran in. Family J and Sport J classes.
Mark N

I'm clueless that as then just a dumbazz kid then having fun! But some one here should/might know more?

[MN4V]

Don't know, is the 850 XS stamped G?
Mark N

[milkdud]

The 850xs block is a stock block, not need to mark it.

J stamp indicated slightly higher porting of the 1500xs type blocks, to differentiate them from a stock 1500 block.

I can only assume the J was in reference to the J class racing that was running these motors at the time.

The J stamp started before the 1976 1500xs's introduction. 1974 sometime they came out.

HERE IS MY OPINION:

My opinion is the early J blocks were hand picked off the line. The ones on the assembly line that measured out higher ports were pulled aside and stamped with a J, destined for the short shaft motors.

Later they may have set up special runs for the J blocks where the ports were specifically different and when they did this they had the J cast into the block.

C

[sharpeye Mike]

As for the upside down, sideways J, I think they are just flops. If you ever used a letter or a number punch set repeatedly you tend to make mistakes if you're not careful, I know I have.

[Robby321]

As for the upside down, sideways J, I think they are just flops. If you ever used a letter or a number punch set repeatedly you tend to make mistakes if you're not careful, I know I have.

YEP! Been there done that too! Makes sense for "J" class running also!

[bernie]

Pretty sure that the "J" blocks were probably ported as a special lot - it would not take much of a tool reset to make exhaust ports .020" higher, and then that operator would be stamping the "J". Nothing was ever measured on the assembly lines. The cylinders liners were all cast in without ports and then ports were machined in later prior to boring if I remember right. The boring/ honing would push the remaining porting metal chips out of the bore areas - we were quite adamant about deburring ports.

[FUJIMO]

Oh, what would "you" know Bergen. lol... Happy Holidays everyone...

[bernie]

Well, like Marschall Grant's book "I was there when it happened", There are very few of us around anymore that were there when it happened. By the way FUJIMO, who the hell are you? JFL and I want to kick your ass just for something to do (lol).

[mr fun]

[QUOTE=bernie;2716219]Well, like Marschall Grant's book "I was there when it happened", There are very few of us around anymore that were there when it happened. By the way FUJIMO, who the hell are you? JFL and I want to kick your ass just for something to do (lol).[/QUOTE,

locker room humor, love it

[milkdud]

Pretty sure that the "J" blocks were probably ported as a special lot - it would not take much of a tool reset to make exhaust ports .020" higher, and then that operator would be stamping the "J". Nothing was ever measured on the assembly lines. The cylinders liners were all cast in without ports and then ports were machined in later prior to boring if I remember right. The boring/ honing would push the remaining porting metal chips out of the bore areas - we were quite adamant about deburring ports.

Sounds good


Did the early J class racing allow for deliberate manufacturing differences in porting from a standard 1500 powerhead? I assumed they didn't allow that... This was why I thought they may have cherry picked the early J blocks off the line and marked a J onto the ones that happen to be taller ports due to normal manufacturing deviations.

Once 1976 came along the 1500xs was in the books as a production motor, and creating a lot of higher ports would not be illegal, since they all would be the same.

I know this may be more questions than answers.
c

[Mark75H]

I think the +/- was something closer to .010" ... a .020" higher block would have been illegal.

The XS was allowed because there was paperwork submitted with its specs and it was certified to be in production and advertised for sale to the general public. The ads weren't just for sales, they were part of the process for allowing the motors in the racing class, its part of the rules.

Pre-XS louvered cowl J appearing motors may or may not have actually been raced. If they were there may have been paperwork submitted on them as higher +/- motors, but all that paperwork is lost to history at this point. A special allowed motor or new +/- spec would be noted in an issue of the APBA newsletter.

[milkdud]

If the Pre 1976 J block motors were just hand picked off the line and only .010+ then they would not need to have special allowance. I realize even this is a guess, but educated guessing is all we are left to when nobody has first hand info.

I would think if they went to the trouble to find/make the Pre-1976 J block motors they would have been raced. If the rules did say +or- .010 tolerance, then it would not be surprising to me if Mercury pushed it to the limits, or at least cherry picked the ones closer to the limit.

This bring my next question. I wonder if the 1976 and newer J block had even taller ports then the pre 1976 J block. Since it was a new production motor on the books it did not have to worry about the tolerances allowed for the standard 1500.

C

[bernie]

The XS designation might have been for marketing use - the lower water pickups, louvered cowl, decals, and perhaps nothing was said about the block. I wonder unless it was a National event how many motors were ever torn down for inspection anyway? It was the only engine running in SJ, and they all ran very close as I remember - it was the driver/ propeller that made the difference. Unless there was a protest, very little inspection was done, seems reed stop height was a big concern.