A race bmw 316, m10, s14, m20, turbo, na, its been the lot!

[Roadsport]

Re: A race bmw 316, now S14 powered again!

If you need to have the rods custom made would it not be worth while to source a desent block and go for the longer rods. Instead of paying the price for only half the benefit. Could reduse the polish on the bores too if that polished bit is on the thrust side. Send the scrap block back to the fellar you bought it from and source another one.

[Graham]

Re: A race bmw 316, now S14 powered again!

im looking for a block, but they dont come up often as just blocks and command serious money in engine form!

[david_white]

Re: A race bmw 316, now S14 powered again!

Thats a real shame about the cracked block, did you return it?
What sort of cc will 2 or 4mm on the rods give you?

[Roadsport]

Re: A race bmw 316, now S14 powered again!

Thats a real shame about the cracked block, did you return it?
What sort of cc will 2 or 4mm on the rods give you?

The displacement is determined by the stroke and the bore. Rod lenght does not affect the cc. It only improves the rod ratio, and helps the engine rev more freely. may hense up the power a bit.
In my opinion this engine may well benefit from longer rods. The 1.8 - 1.9:1 is considdered the optimum rod ratio. Grahams engine now has 1.58:1 and the extra 4mm would make it 1.62:1

[Graham]

Re: A race bmw 316, now S14 powered again!

still got the cracked block, im in two minds as as to whether to attempt to repair it by grinding the crack out to a slot and weld it back up again.

the rod difference wont effect the engine cc, but in this case with the pistons well down the bores has a hell of an effect on the compression ratio. dont remember the figures but im around a whole ratio lower than i wanted to be, and if i do the intended cam swapping i need even more compression

[Roadsport]

Re: A race bmw 316, now S14 powered again!

Any idea what caused it to crack? If you torque the cap down where does it take the crack?

[Graham]

Re: A race bmw 316, now S14 powered again!

In my opinion this engine may well benefit from longer rods. The 1.8 - 1.9:1 is considdered the optimum rod ratio. Grahams engine now has 1.58:1 and the extra 4mm would make it 1.62:1

bmw certainly thought longer rods would be ideal,

2.0 m10 and 3.0 m30 were 134mm/80mm stroke = 1.675
when they turned it into the s14, they went to 144/84 giving the best ratio they used of 1.714
2.5 s14 wasnt as good at 1.655.

[Graham]

Re: A race bmw 316, now S14 powered again!

Any idea what caused it to crack? If you torque the cap down where does it take the crack?

dunno what caused it, if it is genuinely ex dtm and it must of come from something special as its been stress relieved internally has lost of non std drilling to oil ways and these huge screw in alloy cor plugs, you can bet you bottom dollar it failed at very high revs, they used to rev them to 10k. one of the bores has very slight damage, my guess is it threw a rod or broke a crank at a billion revs.

torquing the bots up doesnt effect the crack, and a bearing fits properly, although the housing is a couple of thou egg shaped, with the crack running upwards at about 10.30 i dont see it being a major concern unless it spreads far enough to reach the water jacket because most of the load from the crank is carried into the block walls, i think i'd chance it in a road car, BUT im looking to push the revs higher, im already using 8200, with hotter cams i expect it will be going to 8500 or even 9, if something lets go at those revs you usually just end up with a very expensive pile of scrap

[Graham]

Re: A race bmw 316, now S14 powered again!

its looking like i've found another block another bucket of cash needed!

current line of thought is wondering whether to be greedy on rod length by going to 149, though i probably wont because that will mean i have to machine down piston crowns

[Roadsport]

Re: A race bmw 316, now S14 powered again!

Nice! Lets hope this one gets the thumbs up. I can feel your pain on the rod lenght issue. Any thoughts on what will the dynamic compression be like with the 148(?)mm rods?

[caprimentle]

Re: A race bmw 316, now S14 powered again!

though i probably wont because that will mean i have to machine down piston crowns

lighter pistons though , good news on finding a block G

[Roadsport]

Re: A race bmw 316, now S14 powered again!

lighter pistons though , good news on finding a block G

Those pistons look well thought out, and as such I'm thinking is there any escess material to remove without compromising the strenght?

[Graham]

Re: A race bmw 316, now S14 powered again!

Those pistons look well thought out, and as such I'm thinking is there any escess material to remove without compromising the strenght?

your right im i shall have the rods made to 148, @148 i still may need to trim a fraction off the pistons anyway, so i might be chancing my arm if i go greedy.

as an aside whilst scanning german ebay i found 98mm stroker cranks
up until now i was lead to believe 94mm was the max that would fit giving me the possibility of a 2.7 engine,

a 98mm stroke with a max poss bore of 95.8 would give 2826cc

[Roadsport]

Re: A race bmw 316, now S14 powered again!

How much do the custom rods cost? I'm having a set made that sets me back 900€ / £730

And naturally it comes to mind that these mega cc bits could be used with the current rods once you mill a one mm off the pistons. And you save the £ and trouble of having new rods made , it would be stupid NOT to buy the new crank and pistons =)

[Graham]

Re: A race bmw 316, now S14 powered again!

How much do the custom rods cost? I'm having a set made that sets me back 900€ / £730

thats what fardon charge, though i think theres vat on top.

with those megga strokes of 94 and 98mm, i think you'd have have pistons with proper skirts or rod angles will create serious sideloading on the bores, and they will rubbish the rod/stroke ratio again, current pistons only have a 25mm compression height so there really isnt room to get them much shorter.

my 91mm crank leaves a mere 2mm clearance between big end bolts and crankcase walls, so 98mm must mean grinding the sides of the block away.

for the moment its going to be same crank, same pistons in new block and longer rods