Dreamtuning: max stroke crankshaft that it will fit...

[nuvolarossa]

Hi, I need to have an answer to my frequent dream, so that it will stop coming in my mind:D

Ignoring the friction, the undersquare thing, the rod lenght, piston velocity and overall money....

what is the crankshaft with bigger stroke that will fit without hit the bottom part of the block(without mods to the block)?

There is the clearence to go over 90mm of stroke? something near 99mm without modify the block?

Or who have a oilpan removed or engine dismantled, can measure how much clearence there is when the rod, as the crank turn, go near the block?

What's the Block Deck Height (This is the distance from the centerline of the crankshaft to the top of the block) on M42, and on M44?

[nickmpower]

you wonld want to go much higher then the m47, becuae of how much the pistons will stick out the bottom of the bores at BDC

[strypt]

I believe Hartge did a 2.3L M44 with 99.6 mm stroke? I would guess this is about max possible stroke on these engines ;) Dunno about modifications to those blocks.

Deck height is the same on M42 and M44 but I don't know the actual dimension.

[RouteZeroDesign]

Yeah, im fairly certain that the Hartge 2.3 kit is the max you can go with block modification.

DO you guys know what the maximum bore is, before the cylinder walls start getting too thin?

[CePa318IS]

can you use the m42 forged rods with the m47 crank without modification?

that m47 crank is 88mm correct? I have been thinking of stroking mine, but havent dug into the research yet.

[RouteZeroDesign]

CePa318IS
It would be great if you could do that, but you'd end up putting the stock piston through the head on the first turn over.

If you're using the stock pistons you would have to get rods that are 3.5mm smaller (I think the m42 crank is 81mm but i cant remember)
or
If you're using the stock rods, you would have to get pistons with a 3.5mm lower compression height (compression height=vertical distance between center of wrist pin and the top of the piston, excluding the dome)
The first option is better, because taller compression height is better for Forced induction...thats the route your going, right?

With a 88mm stroke and a rod length of 136.5mm (is standard 140mm?) the rod ratio would be 1.549:1
Whereas with the 88mm stroke and 140mm rod length the rod ratio is 1.590:1

Increasing the rod ratio reduces rod angularity, which reduces the side loading of the piston against the cylinder wall thrust surfaces.

As you can see its not really an easy choice to make, and the best solution is to go for aftermarket pistons and rods, that way you can have your cake and eat it!

Hope that helps :)

Paul

[strypt]

M42 crank is 81 mm - correct but rod length should be 3.5 mm shorter than stock, if original compression height is retained. Half the stroke is "positive" and the other half is "negative". I hope you understand what I mean ;) english is not my native languange.

[RouteZeroDesign]

lol, i cant believe i did that.
My mistake, thanks for pointing that out.

In my defense, it was 1:13AM.....i was very tired :)

Okay, its fixed now, just so nobody picks up false information ;)