Author Topic: HHC?  (Read 3627 times)

Online RichardL

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Offline snowbeard

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Re: HHC?
« Reply #16 on: 20.03. 2009 18:40 »
aha! well those certainly look the part, I guess there's a decent chance I still have the higher compression!

I did put an email in to SRM to inquire after the reasoning behind 35 degrees, we'll see what they say I guess!

at this point I'm second guessing having the head redone at all, but I have it off, I may as well press on!!  it's only money, eh?! 

thanks for the link!
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\'57 BSA A-10 Spitfire Scrambler
Spitfire Starting Video
\1960 Super Rocket (basket)
\1981 Suzi GS650
\1988 BMW K100LT in Lisbon!!

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Offline trevinoz

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Re: HHC?
« Reply #17 on: 21.03. 2009 21:41 »
Looking at those pistons, I would say they are 8.75:1 or commonly known as 9:1.
Check the numbers in the parts book.
Trev.

Online RichardL

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Re: HHC?
« Reply #18 on: 22.03. 2009 00:18 »
Trev,

It wouldn't surprise me if you knew more than the folks at British Only Austria, but the pistons they show as "8.25:1" are almost certainly the same top geometry as Snowbeard's. My own pistons are full domed, which I am fairly certain are the 9:1 variety. Please, just correct me if I am off the mark.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline snowbeard

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Re: HHC?
« Reply #19 on: 22.03. 2009 05:31 »
sorry, but I haven't got a parts book yet. I haven't had enough confidence that the spitfire specific models will be accurately listed in a non specific parts book from the range of dates I've seen so far.

I did find a site that has listed these part numbers as A10 pistons, 0.060 over, but if the 1 M/M OS means millimeter, that would be 0.040 over...


 67-1601 Piston A-10 STD 9-1 pair 2 $177.50

 67-1603 Piston A-10 +.020 9:1 pair 4 $180.25

 67-1605 Piston A-10 + .040 9:1 pair 4 $160.60

 67-1606 Piston A-10 + .060 pair 2 $160.60

 67-1607 Piston A-10 + .02 pair 4 $150.00

looked at the bores again today with a little more time, they may need to be cleaned up after all.  so how much material does a honing remove vs a rebore?
__________________
\'57 BSA A-10 Spitfire Scrambler
Spitfire Starting Video
\1960 Super Rocket (basket)
\1981 Suzi GS650
\1988 BMW K100LT in Lisbon!!

=

Offline trevinoz

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Re: HHC?
« Reply #20 on: 22.03. 2009 20:57 »
Richard L, the original 8.75:1 pistons fitted to A10s were as pictured, as were the 8.25 type. I don't have a 8.75 to hand to measure the difference in height, but I will see if a mate has one handy to check.
I have seen the domed type, the dome rising like a pimple from the centre of the piston with a flat area around it. The set I saw many years ago were in a Hepolite box and marked "Ariel Huntmaster".
  Trev.