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Using model 30 Piston in 1935 ES2

Submitted by andrew_jarrett on Tue, 17/05/2016
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Hi All,

I am restoring a 1935 ES2 and have found my bore is at +40 and do not have a suitable piston to suit a re-bore.

I am only going to bore till it is just clean and grind a piston to suit, this is were the question starts I have a spare new Hepolite 500 International piston that is original but not fully machined that will do the job.

What possible issues may I have using this piston, possibly different weight changing balance factor? please let me know if anybody has done this before and if you think there may be a problem.

Thanks in advance for any help

Cheers

Andy

Submitted by paul_gibbons on Wed, 18/05/2016

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Hi Andy

An Inter Piston will fit absolutly fine and should give you no problems. I only question why you want to go down this road. What ever route you take you are going to invest quite a bit of money. If your barrel is already at +40 and requires cleaning up it would seem that your barrel in it's current form is at the end of it's life. It would not be much more expensive to sleeve the barrel and go back to a new std ES2 Piston which are freely available. you could then sell the New Inter piston unmolested to fund the re-sleeve.

Paul G (Surrey Branch)

Submitted by richard_cornish on Wed, 18/05/2016

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Hi Andy,

You say your piston is part machined, but what part is not finished ? The compression height (measured from the centre of thelittle end to the top of the piston)on the ES2 is 1/8th of an inch higher than a Model 30 and the con-rod at the little end is 1/8th inch wider. It will be O.K. to make the con-rod narrower, but if you use the shorter piston this will drop the compression to about 6 to 1. Unfortunately these engines have short studs holding the barrel to the crankcases by just the flange so you should not try shortening it to compensate the difference. The weight should be about the same but it would be best being a bit lighter.

Regards, Richard.

Submitted by andrew_jarrett on Sun, 22/05/2016

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Previously Paul Gibbons wrote:

Hi Andy

An Inter Piston will fit absolutly fine and should give you no problems. I only question why you want to go down this road. What ever route you take you are going to invest quite a bit of money. If your barrel is already at +40 and requires cleaning up it would seem that your barrel in it's current form is at the end of it's life. It would not be much more expensive to sleeve the barrel and go back to a new std ES2 Piston which are freely available. you could then sell the New Inter piston unmolested to fund the re-sleeve.

Paul G (Surrey Branch)

Hi Paul

I wanted to try and keep on the original bore as I have been told that re sleaving can sometimes have issues with hot spots.

I was only going to clean up the bore and have checked with the machines and will clean out to +50 so I will get another rebore if ever required before sleaving, as it turns out I am going to go with the JP piston as they will supply the piston ground to the size I require. I will keep the inter piston for a spare for my inters.

thanks

Andy

Submitted by andrew_jarrett on Sun, 22/05/2016

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Previously Paul Gibbons wrote:

Hi Andy

Paul Norman at Racing Vincent does sell new +60 ES2 pistons, and has them in stock.

Paul G

Hi Paul

Thanks for the advice, I looked at the site and found out he is selling the JP pistons which is handy as I only live 40 minutes from the factory here in Australia. I was trying to use original Hepolite but the JP pistons should be OK as it seems a lot of parts suppliers are using them.

Cheers

Andy

 


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