87mm conrod help

[whipsey]

i've ot a set of m20 conrods here 87mm in length what can these be used in ?

[whipsey]

anyone?

[maggspower]

I think you need a new ruler

m20 conrods are 135mm for the 325i, and 130mm for the 320i

[maggspower]

that measurement is from the centre of each bore

[Jhonno]

I think you need a new ruler

m20 conrods are 135mm for the 325i, and 130mm for the 320i

[whipsey]

i think you may be right lol they are from a 320i was under the impression they could be used in some sort of stroker engine

[Jhonno]

2.8 stroker iirc

[maggspower]

Yes 2.8 or a 2.7

[whipsey]

with what pistons? iv'e got a 731 head here already for a 2.7 what exactly is a stroker engine?

[maggspower]

can open, worms everywhere

If you are using the 731 head you got to use the ETA pistons.

Its best to look at Andyboy's 2.7 thread, it is a sticky at the top of this section

[whipsey]

lol so what exactly is a stroker engine?

[Jhonno]

an engine which is stroked out..

[maggspower]

The bore of the engine is the diameter of the piston, the stroke is the distance that this piston travels up and down the bore. When people talk of creating a "stroker" engine, what they mean is they will be increasing the amount of travel of the piston within the cylinder bore.

For example the ETA or 324td crank(used for 2.7 conversions) has a longer stroke than the standard 325i crank by 6mm, 75mm for the 325i and 81mm for the ETA ect. Added up over the 6 cylinders this is where we get the extra 200cc to make 2700cc. The m52 crank has a longer stroke again hence 2.8.........

[whipsey]

so the m20 2.0 conrods are longer then i'm sure they measured 87mm

[maggspower]

No m20b20 con rods are 5mm shorter. With the 81mm stroke crank you get an extra 6mm stroke, 3mm at bottom dead centre (BDC) and 3mm at top dead centre (TDC), so if you used the normal m20b25 rods (135mm) they would stick out the top of the bore 3mm too much, not good as they would hit the head.

So to combat this we use the shorter rods of the m20b20 (130mm) this means that they sit about 2mm down the bore, a quick skim off the block, about 1.5mm to get the compression ratio back. Job done.

or you could just use the ETA crank, rods and pistons, to make it easy.

Next

[whipsey]

so it would be easier then to just get a eta block etc ad bolt the 731 head to it? would it be worth selling the m20b20 conrods?

[Jhonno]

better off bolting an 885 head on.. better flow

[whipsey]

i've already got the 731 head sitting here so i'm tryin to use up as many spare bits i have rather than buying extra saying that my mate is breaking an 88 325 touring

[maggspower]

Much easier, if you can find one, but you need the crank anyway if you want a 2.7. Im sure somone on here has one stuck in the back of their shed, stick a wanted up. Then just a case of bolting them together, 325i cam, bit of spannering here and there, and your ready to go! I may have glossed over some bits there

What condition are the rods in, how much you want for them? Please bear in mind you have been frying my brain for the last hour

Only kiddin' cheers maggs

[whipsey]

Much easier, if you can find one, but you need the crank anyway if you want a 2.7. Im sure somone on here has one stuck in the back of their shed, stick a wanted up. Then just a case of bolting them together, 325i cam, bit of spannering here and there, and your ready to go! I may have glossed over some bits there

What condition are the rods in, how much you want for them? Please bear in mind you have been frying my brain for the last hour

Only kiddin' cheers maggs

pm sent

[maggspower]

You could use the 885 head, but the compression will be lower on the ETA block. Granted the 731 head will probably have given its best by 5500rpm, but the low down torque would be some thing m50 owners have wet dreams about

[whipsey]

this is what i was thinking anything over 100mph can't really be used on the roads any way i would prefer the acceleration over top end

[maggspower]

Got your pm, will let you know asap.

That sort of spec is great for real world driving, loads of people think they want huge bhp numbers, when they really want torque. And thats what you'll get.

[whipsey]

that sounds like the plan then so i now have two builds and two conversion's on the go should keep me busy through the winter

[Jhonno]

but the low down torque would be some thing m50 owners have wet dreams about

sadly I doubt that.. Esp on a VANOS engine.. Mine pulls cleanly and well from 800rpm in 5th

[maggspower]

I was only winding you up, looks like it worked too I know thats what you got.
Seriously though anywhere above 4000rpm a 2 valve per cylinder engine is going to have its ass handed to it by an equaly sized 4 valver, its also more economic with the development of inlet port and combustion chamber design, and it has a much higher potential for tuning, no questions its a better engine.

BUT, when it comes to low speed torque a well built m20b27 is going to have more than a m50b25, please it's all us 12 valver historians have got to live for, that and the noise

Didn't mean to get your back up.

cheers maggs

[Jhonno]

My back isn't up at all fella..

[maggspower]

[Jhonno]

Just the advantage of VANOS is torque everywhere and power at the top end also..

Be interesting to see some comparative dyno plots..

[maggspower]

Thats true the vanos is a great feat of engineering which alters the valve timing throughout the rev range. One of those having your cake and eat it moments All engines are compremises the vanos takes away one of these factors. The advantage the 2v per cylinder has is port air speed, in simple terms a higher air speed in the port means better air and fuel mixing, better cyilnder filling, more turbulance, leading to a better burn. This increases up to a point where you cant fit any more air down the port, the 4v per cylinder will come in to its own now.

But yes your right I too would like to see some dyno plots

[GrindCulture]

Bit O/T here, but the M20 can be stroked to 2.8 by using the M52 crank and to over 3L using an M54 crank right? Can the M50 be stroked to about 3L with an M54 crank?

[maggspower]

Good question I dont know. First the bearing journals would have to line up with the corresponding cylinders and bearings, and the counterweights miss the block internals. But if the m54 crank can be made to go in the m20, then there must be a good chance with a bit of jiggery pokery the m54 will go in the m50. I say the m50 as i'm sure the m52 gubbins will go in it to make it an iron block 2.8, much better than, the alu block imo

[Jhonno]

Yes it can