Difference in cylinder head from 1966 Hornet to 1967 model.

[boriscross]

I'm re building a 1966 A65 H Hornet. I think this has had a later head fitted (bigger valves and shorter valve springs). Is there a way to confirm this? I assume the casting number would be different? Anybody got any other ideas of how to identify what cylinder head I have on this?

[JulianS]

What casting number do you have?

[idie]

I think the A65 had large valves for 1966 only.

[Bess]

Hi,
     I believe:

The hornet in 1965 had head part number 68-0465 fitted with a inlet valve 68-0156 diameter of 1.410" 3.557" long, exhaust valve 68-0157 1.415" diameter 3.555" long.

1966 onwards it had head 68-0834 with a inlet valve 68-0665 diameter of 1.600", 3.600" long, exhaust valve 68-663 1.410" diameter 3.555" long.

Best wishes...

[JulianS]

Early 1967 season head was modified when the rear 2 cylinder head bolts were increased in diameter from 5/16 inch to 3/8 inch. The first 1967 season twins left the factory in July 1966.

New head part 68 879 (parts service bulletin GA12 August 1966)

Earlier heads (and barrels) may have been modified to accept these larger bolts by owners/dealers.

[Bess]

Hi,
     If you have head Pt no. 68-0879.

The valves are the same as 1966 onwards. Inlet valve 68-0665 diameter of 1.600", 3.600" long, exhaust valve 68-663 1.410" diameter 3.555" long.

Best wishes...

[boriscross]

Sorry about the time to get an answer on the casting number the head has been away. The casting number is 68-701.