Can I use 78mm crank in stock 1600 engine?

[jeff01]

What would be the static CR without cylinder spacers?
I would like to get some more RPM with cheapest way. I thaught that maybe the 78 chinese crank should be OK. I would like to use std pistons because I have new ones and displacement should be under 1800cc this and next year....and in future I would use 94´s

Why I´m asking CRis is because I have turbocharged engine and exhaust is already done and it doesn´t fit when I use spacers.......Not a big problem to make it fit but I´m still asking it.

What else I should change if I want to spin it 7000 RPM
I have red that stock rod-s could survive that.
I think I need double valve springs too. Anything else?

How much more power would NA 78x85,5 make than 69x85,5 when it spins 2000 rpm more ? (5000 vs 7000) .......when I double this nr. It should be te effect of my engine with 15 PSI

Thank you all

[Matthew]

The simple answer is no. You have to build the whole engine around the 78mm crank. With std pistons and 78 stroke, the pistons will come out the top of the cylinders. You would need spacers 4.5mm thick to get back to the original deck height.
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1965 Beetle sedan
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[bartman]

Not necessarily.
With a 78mm crank, stock rods, and A pistons I have just under .1" of negative deck.
This combo with B pistons gave me about .1" positive deck.
This is on a new case that's never been decked or anything.

[modok]

That's about right, 78 stroke and a 34mm pin height should be right around .100" deck.
Surface case .040"-.050 and there you go, or live with the loose deck.
I believe ACN's 85.5 b are 34mm pin height.
I'd do it, I'd also make sure you have at least .0022" rod bearing clearance.

[jeff01]

So with cylinder spacers I can anyway do it right?
Are there any point why I shouldn´t do that?
What would be the weakest part when I want to spin it up to 7000 rpm?

How much more power it could produce? ( Maybe nothing with stock heads and NA engine ? but with turbo the heads shouldn´t be the problem)

I have another case and a-lot of used stock parts.
My Idea was that I need only new crank, valve springs and camshaft for more power and higher redline (Ofcourse gaskets and bearings too) ....is it wrong?


Would it be more or less powerful than 1915 low rpm engine?

[modok]

With stock pistons you will need .177" (5.5mm) spacers. You will have to have these made custom probably. Rimco can make them. That's a lot of spacer though, your exhaust won't stretch that much!

Weak link? More like the whole chain will wear out pretty fast at 7000 rpm, but i don't think anything's gonna explode. Stock pistons aren't made to go that fast! But 15 psi might hold them together!! Yee haw!

Balance crank and flywheel, set bearing clearances, this is important no matter if you use stock or fancy parts.

[jeff01]

Thanks for your help.

I´ll cut exhaust and weld it back together....not a problem.
I would like to use it 3-4 times a year on quarter mile events and maybe on summer sundays on streets. When it lasts 2-3 years of that then its enouh for me.

Could you help me with cam selecting too? Can I use stock rockers with some cam or not? I cant use large overlap I think

do I need straight cut gears ?

[Matthew]

I have a 1600 that's all stock except for the 78mm crank, I beam rods, web 86A cam, 90.5 jugs, hand ported 40x35.5 heads, 1.5" exhaust, and dual 40 dellortos.

If you want to be happy design the whole engine as a system.
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1965 Beetle sedan
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