Drilling block to 11 studs from 9

[Bruce_B]

Since my new cylinder head is 11 studs I need to have the machine shop drill the extra 2 holes.

Question - Do they get drilled a different size? I don't have the ARP bolts yet do I'm not sure what to tell the shop. Seems to be I've seen some articles that mention a different torque setting for the 2 additional bolts.

Also a bit nervous - mentioned this to the machine shop and he had never heard of it before...I'll have to bring the cylinder head and a gasket over. Is it important for them to have an ll stud gasket or can they drill right through the 9 stud gasket?

Thanks,

 

[racingenglishcars]

Yeah. Different size.
From what I remember, the standard head bolts are 3/8 and the two extra are normally drilled to 5/16 but sometimes oversized to 3/8 if a repair is needed. But then they don't fit past the rocker shaft or something. I really should check the Vizard books though.
Donn.

 

[Hap Waldrop]

The two extra studs are the same size as the other ones and take the same torque. I have a vintage engine I take care for the customer which is 11 stud. I know you are doing this because of your head, but here's my advice to anyone thinking of doing this, this is not allowed in SCCA racing and that is where the highest compression ratios are being run, so if a SCCA 1275 race motor can live at 15 to 1 compression ratio with 9 studs, what condition would warrant 11 studs, if this did not.

 

[racingenglishcars]

One more thing.
They should use the head as a template, not the gasket.

I think it's only the valve cover that causes problems with the larger bolts. The gasket becomes very thin where you must grind a little from the valve cover flange.

It is understandable that they have never heard of it before. These engines haven't been produced in years and nearly all the high performance stuff has been done for all the racers out there that need it. Anybody that specializes in A-series engines knows about this mod.

Cheers, Donn.

 

[racingenglishcars]

This was a factory deal on some engines, I think it was the 1300 GT and later Cooper S, just not the Sprite or Midget. My old FP car had this, but that was back in the 80s. SCCA probably no longer accepts this because it didn't come on the spridget, but they have to accept if someone were racing the proper type Mini.
Donn.