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Hepolite P21253 Pistons And Forced Induction


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#1 JonnyAlpha

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Posted 18 December 2021 - 10:43 PM

I am building a 1310 road engine for the odd track day maybe.
A+ 1275
Hepolite P21253 +40 Pistons
4.5 thou Deck Height
AC RS Cam
MED ST1 Lightened Flywheel and Performance Road Clutch Kit
AC 1.3 Rockers (Not yet purchased)
3.44 Diff
Metro Electronic Dizzy (to be re-curved) - will be swapped out for a non dizzy Megajolt or equivalent trigger wheel setup hopefully before recurving the Metro Dizzy

Now contemplating a Supercharger (subject of many other threads and posts on FB etc looking for info).

The idea is to finish building the engine up but ensure that when fitting the SC it will just be a head off and external modification, with all the internal parts sufficient for the additional torque.

Current build has a MED ST1 Clutch and Lightened Flywheel along with a 3.44 Single Molybendium Pin Diff (Built by John Guess), but I am changing this to a 3.1 Cross Pin and Upgrading the clutch.

Question:
Anyone else running Forced Induction with these pistons, will they be ok with the added boost.
I will be aiming for 8.5 CR and 10PSI boost. This will be a weekend fun car, maybe the odd track day or hill climb for fun.

#2 nicklouse

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Posted 18 December 2021 - 10:52 PM

Noting to say about the pistons but don’t bother hillclimbing it as you will be way out of class.  you will be classed as an 1800cc car.



#3 JonnyAlpha

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Posted 18 December 2021 - 10:55 PM

Noting to say about the pistons but don’t bother hillclimbing it as you will be way out of class. you will be classed as an 1800cc car.

I live in Devon, we hill climb whenever we go for a drive 😂😂🤣 seriously though, didn’t know that thanks

#4 Ethel

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Posted 19 December 2021 - 12:54 AM

Pistons will be up to the job, but watch your compression ratio.



#5 nicklouse

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Posted 19 December 2021 - 01:20 AM

 

Noting to say about the pistons but don’t bother hillclimbing it as you will be way out of class. you will be classed as an 1800cc car.

I live in Devon, we hill climb whenever we go for a drive seriously though, didn’t know that thanks

 

There is a multiplier for forced induction,  normally 1.4 but for certain classes it is 1.7 but that is for standard cars that have turbos already.



#6 Steve220

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Posted 19 December 2021 - 11:34 AM

You don't mention which cylinder head you're using? The chambers will have to be huge with your current spec. I, sadly, haven't had good results with standard cast pistons as detonation destroyed the ringlands.



#7 Steve220

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Posted 19 December 2021 - 11:35 AM

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#8 JonnyAlpha

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Posted 19 December 2021 - 02:37 PM

You don't mention which cylinder head you're using? The chambers will have to be huge with your current spec. I, sadly, haven't had good results with standard cast pistons as detonation destroyed the ringlands.


12G940 Head, porting and chamber work being done by me. Aiming for 9.75 CR by increasing the chamber size. But will decrease this to 8.5 by using a Decompression plate from Vmaxcart.




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