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ESP Man
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Discussion Starter · #1 ·
I am putting my 351 + 30th motor back to near std but my cast 2V closed chamber heads with 4V valves are 61cc (just had them cc'd) and with std flat top pistons the comp ratio is up around 10.5. I know everyone says don't put 4V valves in 2V heads but they were already done when I bought the motor and the valve seats have been hardened so prefer to stick with these heads so I can run with ordinary unleaded

I can get a ACL 22cc dished piston but this drops the comp to around 8.5 which is too low

I am aiming for around 9.5 so I need about a 10cc dish

Anyone know of a piston that would suit.

Alternatively I also have a set of the longer 302 rods which I could use in combo with some other piston if anyone has any alternatives
 

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shaynet said:
I am putting my 351 + 30th motor back to near std but my cast 2V closed chamber heads with 4V valves are 61cc (just had them cc'd) and with std flat top pistons the comp ratio is up around 10.5. I know everyone says don't put 4V valves in 2V heads but they were already done when I bought the motor and the valve seats have been hardened so prefer to stick with these heads so I can run with ordinary unleaded

I can get a ACL 22cc dished piston but this drops the comp to around 8.5 which is too low

I am aiming for around 9.5 so I need about a 10cc dish

Anyone know of a piston that would suit.

Alternatively I also have a set of the longer 302 rods which I could use in combo with some other piston if anyone has any alternatives
WHy not clean the chambers with a little polish and grind ?
then cc them
 

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ESP Man
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904 Posts
Discussion Starter · #3 ·
atec77 said:
WHy not clean the chambers with a little polish and grind ?
then cc them
Lot of work in that trying to match all the chambers

I could get the heads shaved to reduce the combustion chamber by 12cc and use the ACL's with the 22cc dish but it would be easier to just find a piston with about a 10cc dish.

Std flat tops only have 2cc for the valve relief
 

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There must be several aftermarket dish top pistons available in Australia. 351C came with dish tops as standard in some USA motors so the aftermarket will have them. I've got a set in my workshop right now that has about a 10cc dish. Phone around some speed shops and I'm sure you'll get a few to choose from. Brands like Hypertech, Badger, JCC, TRW, Speedpro should have something.

Good luck
 

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ESP Man
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Discussion Starter · #5 ·
Thanks for the replys

I have decided to just get the std flat tops and have the tops machined off them to get the 9.5. Cost is $70 for machining
 

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Nothing beats a V8
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y shouldnt people run 4V valves in 2V heads?
 

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ESP Man
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Discussion Starter · #8 ·
XTREME said:
y shouldnt people run 4V valves in 2V heads?
I believe the theory is that it will slow the airspeed down and not be as efficient.

Its the old bigger is not always better argument
 

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I am putting my 351 + 30th motor back to near std but my cast 2V closed chamber heads with 4V valves are 61cc (just had them cc'd) and with std flat top pistons the comp ratio is up around 10.5. I know everyone says don't put 4V valves in 2V heads but they were already done when I bought the motor and the valve seats have been hardened so prefer to stick with these heads so I can run with ordinary unleaded

I can get a ACL 22cc dished piston but this drops the comp to around 8.5 which is too low

I am aiming for around 9.5 so I need about a 10cc dish

Anyone know of a piston that would suit.

Alternatively I also have a set of the longer 302 rods which I could use in combo with some other piston if anyone has any alternatives
Looking for one 30th 351c dished piston used, if u are changing your pistons out. Thanks mick. [email protected]
 
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