Lets Start a Custom Pistons Specs thread for Different Stroker Combos

[digger]

Old a dead thread but I have a question hopfully some one can answer it for me....?

Can I sub the crank for the above builds with a M54B30 Crank
it has the same stroke 89.6mm??

I've also heard they are one in the same? Is this also true...?


thanks

yes, i am pretty sure mine was a M54B30

[tinkwithanr]

Yes you can, I'm using the M54B30 crank in my 3.15L build. I'm also hoping to not need to cut down the counterweights much, the M54/S52 weights are a lot shorter than the m52 ones, and my CP pistons are very low profile.

You will need an oil seal spacer for the crank also.

[MonkeyMadness]

Cool thanks guys just double checking.. I was thinking pretty much what you guys said.... :up:

[F34R]

I am going to source parts to build my 3.0 this coming fall. My question is what would be better for a long term boosted m20? I have the 288 already and I think the best route is to resolve the low CR.

I am planning on the s50 crank and rods with custom Ross pistons to raise the CR to make use of the 288 Schrick cam.

I just don't know if I should do the s52 crank and s50 rods with custom Ross pistons. It would save on block machine work. I have everything to prep the block at my shop.

I also want to Oring the block, so that would leave more room on the block surface to groove.

[MonkeyMadness]

I am going to source parts to build my 3.0 this coming fall. My question is what would be better for a long term boosted m20? I have the 288 already and I think the best route is to resolve the low CR.

I am planning on the s50 crank and rods with custom Ross pistons to raise the CR to make use of the 288 Schrick cam.

I just don't know if I should do the s52 crank and s50 rods with custom Ross pistons. It would save on block machine work. I have everything to prep the block at my shop.

I also want to Oring the block, so that would leave more room on the block surface to groove.

I would go with the s50 crank this will keep your bore x Stroke closer to square.
Your going to have to machine the block to O-ring any way so the added cost of the extra bore will be a mute issue.
You also mentioned boosted but in the next paragraph you wanted raised CR. Whats your plan Booster or N/A?
Remember when dealing with boost your CR is raised for ever lbs of boost the cylinder see. For example your at see level and you have 8.8:1 Cr N/A then you add 10lbs boost your Cr jumps while under load and boost to 14.79:1. You have to take this added stress on the motor into account.
At this point less stroke and more bore will help you save the motor.
Less distance and speed the piston has to travel.

Also if your at 3.0 lowering the Cr wont be as noticeable while off boost as a 2.5 due to the add Cubic Inches.
So if this is going to be street driven as well a beaten on the track~ then driven home afterwords I would go for a less stress inducing Cr, S50 crank,
O-ring block, MS, 288 cam.. And when we Order the Pistons we can give them all this motor info an have them build in the wanted Cr, Even with an O-ringed block/head

http://www.rbracing-rsr.com/compression.htm

[F34R]

Thanks for chiming in buddy, that is the info I was looking to get. I did not know adding boost would raise the ratio that much.

Plans: I have not bought anything but the 288 as you know from our long facebook chats.

I just want to get more low end to help the 288 not be dead flat on the bottom. I love SCCA and built the car for that. So a dead spot in a must need area for low end grunt is not good for setting quick times.

I was looking to trade for a 272 like most mentioned, but the issue with the 288 is the CR. I thought doing a fresh proper 3.0 build would be perfect. Then do MS2 or 3 and get the car in perfect NA order for move onto some FI.

For now I want a proper NA stroker that can make use of that awesome cam. But in the long run also work with the bottom end to put down some fun power. I would love to get around 350ish to the wheels. I daily the car as of now, so I want something that can put my wide tires to work and be fun on the road too.

I am not apposed to staying with the SETA crank and doing custom pistons if that will give a better end result. I have a spare b27 block saved for this.

Long term the car WILL see a snail, you know that already. So I am open to any combo if it will work hand in hand in the end.

[digger]

there is no rational argument against using a S52 crank over a S50 one where there are no rules to limit cc's, all you'll end up is less power at low and mid rpms if you use a shorter crank. The peak hp will be governed by other things but on the street as big as you can go without detriment to reliability is the way to go IMO

[MonkeyMan]

here's mine..
pistons: stock M20B25 (84.5mm)
rods: S50 (135mm)
crank: euro M20B23 (76.8mm)
an MLS head gasket is necessary for proper clearance (can't remember the spec)..

This is the previous owner's build, and I don't think the slight increase in stroke (1.8mm) is worth the worry of using an MLS head gasket. Especially since there's not a significant increase in c/r. I've had some motor issues lately, so I'll be doing another teardown, this time utilizing a stock B25 crank and my existing pistons so I don't have to machine the block and I'll be able to use a stock head gasket.

[digger]

here's mine..
pistons: stock M20B25 (84.5mm)
rods: S50 (135mm)
crank: euro M20B23 (76.8mm)
an MLS head gasket is necessary for proper clearance (can't remember the spec)..

This is the previous owner's build, and I don't think the slight increase in stroke (1.8mm) is worth the worry of using an MLS head gasket. Especially since there's not a significant increase in c/r. I've had some motor issues lately, so I'll be doing another teardown, this time utilizing a stock B25 crank and my existing pistons so I don't have to machine the block and I'll be able to use a stock head gasket.

a thicker gasket than stock will kill the squish that makes the B25 piston and 885 head work so well and this is important for a naturally aspirated engine, usually the squish needs to be tightened a bit on the stock engines to work best. no use in making one component better by making another worse.

it comes down to cost, a S52 crank is no more than a S50 one nor are the custom pistons. if you compare a S52-obd1 to an equivalent S50 in an E36 you will get an idea of the difference that the extra stroke brings to the table it is not insignificant at low and mid rpms.

[SeatTime]

Comments on squish: Mostly related to emissions. Two ideas, very little squish volume (pressed tight) and there's nothing to burn in it (mixture) or don't press it tight and it's easier to burn. You'd have to run on a dyno to figure out if either was helping or hurting, but given other things staying the same I guess tightening it up would be recommendation too.

I would also suggest that in the world of modern engines 1.8mm is A REALLY BIG DEAL!

[SeatTime]

Also, what is the wrist pin diameter?

[digger]

i should correct my statement above as i was in lala land, using the 76.8mm crank the piston would rise 0.9mm further up the bore and you could use a thicker gasket to maintain the stock squish and chamber volume.

[MonkeyMan]

i should correct my statement above as i was in lala land, using the 76.8mm crank the piston would rise 0.9mm further up the bore and you could use a thicker gasket to maintain the stock squish and chamber volume.

Now with the fact in mind that a stock M20B25 engine has an 8.5:1 c/r, does this mean that there is quite a bit of piston/valve clearance and theoretically you have some room to play around with decking the block for a higher c/r?

I know I probably need to consider the dome shape of a stock B25 piston (which I am using) and how it might contact the head in an area other than the valve reliefs, but is it possible to deck a stock block with stock pistons to raise the c/r?

And with this said, would it be possible to not machine the block, keep my existing combo with the 76.8mm crank (seeing as it's only 0.9mm higher in the bore), and get away with using a stock head gasket?

[digger]

Now with the fact in mind that a stock M20B25 engine has an 8.5:1 c/r, does this mean that there is quite a bit of piston/valve clearance and theoretically you have some room to play around with decking the block for a higher c/r?

I know I probably need to consider the dome shape of a stock B25 piston (which I am using) and how it might contact the head in an area other than the valve reliefs, but is it possible to deck a stock block with stock pistons to raise the c/r?

And with this said, would it be possible to not machine the block, keep my existing combo with the 76.8mm crank (seeing as it's only 0.9mm higher in the bore), and get away with using a stock head gasket?

on a 100% stock M20b25 you can deck the block a little or the head or both but you need to measure how much is safe and whether the increased CR is worth it. you need to check piston to head and piston to valve clearances etc

if you did nothing with your existing combo you would need to verify both piston to head clearance and piston to valve clearance when using a stock gasket.