Type 4 rebuild - deck height and compression ratio

So I have 55cc + 2.4cc = 57.4cc
I need 63cc
So I need to find another 5.6cc in each combustion chamber

Then I need to shim to set the deck height (1.5 - 0.8) 0.7mm from the mating surface of the barrel

Would it be worth polishing out the casting marks within the combustion chamber to see how much that gives me?

 

No, not worth polishing.
Probably why VW made 2l with dished pistons...and why everyone switches to cams with more duration if they not only up the capacity but are faced with flat top pistons to do so. None of this market is aimed at us poor saps in buses. Madness IMO.

 

I make that 8.5 CR.....

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With the standard combustion chamber volume yes. If I can increase it to 63cc total - grinding another 5.6cc out of the head, I should be on 8:1 compression

Is that feasible?

 

5.6cc is a fair bit of metal... I managed about 2.5 (just checked.. just over 4 by the end), but mine were 1800 heads.. down each side of the spark plug has a fair depth to go at..
3cc should get you to about 8.2 at a guess think you get about .1 per cc on a 2056 from memory


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Would it be simpler to get a set of standard dished pistons? Stateside tuning seem to stock them

 

If he does have 96's.. might be ..if you don't want to grind a lump or two out of the head.. wouldn't really believe the website don't think he's updated it since it was set up... check those camshaft prices!...

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94s are available in a few places (Cool Air, Heritage, JK), dished as per original. I think I'd be saving myself a lot of pain.

Anyone want a set of 96mm pistons?
(It's too late to return them)

 

Or a cam with more overlap...prob easier and cheaper to drop to stock.. or take a dremel to those heads... cheaper still..

Or how bad would 8.5 actually be?.. plenty run higher..

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With super unleaded you would probably be ok at 8.5 trouble is you can’t always get super and of course there’s the extra cost over time.
Cheapest would be to take your heads to an engine shop for reworking. They could mill them out to give you the extra cc’s without you worrying about doing them wrong.
Otherwise go with the dished pistons but that’s going to cost.
I think you can get a set of dished from AA, it’s just a waiting game for them to arrive though.
Pity you couldn’t have ordered earlier in the month, they had an independence day sale on with 20% off.

 

You're not the Norris selling the 2.4 type 4 stuff on Facebook then?

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No, not me

 

Most of the sets I've been looking at have been AA. If you can believe their website, some people have them in stock

I think I'll get a dished set. I only want to do this once

 

Check out brickwerks.
Kolbenschmidt

decent quality

https://www.brickwerks.co.uk/barrel-and-piston-set-t3-2-0-aircooled-oem.html

 

AA pistons may not be so good but use what you have. No problem at all to take the combustion chambers out to 63cc but don't use a very low CR, the pic are 62cc chambers – without a step. Remove the casting roughness but don’t polish the chambers or ports, especially the inlets.

 

Those head chambers above are a very similar shape to mine, I got mine to measure 63cc in each chamber, took ages to do, as your doing it 4 times.
I dare not say what my deck is set at. you wouldn't believe me.

 

Thanks everyone for your help so far

I've decided to get some standard 94mm dished pistons. I'm looking at these - https://aapistons.com/collections/v...-2-0-type-4-pistons-cylinders-bus-porsche-914

According to the website the dishes are 10cc. That would give me total 65cc combustion, with a 1mm deck height, to give 7.8:1 compression ratio

 

Might make it cheaper without import fees but check on VAT situation.. there's pots to match..

https://www.design911.com/Piston-set--Dished-94x71mm-Porsche-914/prod137058

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They are rather cheap - £150 including VAT and delivery

Are they any good?

 

From the part no.. they're AA ones you were looking at from the states .. but give them a ring just in case .. and it is just pistons ..

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