engine and drivetrain How many of you are running 91mm Pistons or larger?

[burndog]

I am interested in building a big bore, 10:1, high-rev', big cam, ITB / EFI motor, as a backup to the turbo motor. I would love to read running examples of of such combinations and recommendations of what works and what doesn't. The suggestions don't have to be EFI specific, as I am proficient with that at this point.

 

Thanks in advance,

 

BURNDOG

[Russell74Fjord]

and what will you use for a head gasket, that might prove to be a weak point,

[kbmb02]

Something to consider: cylinder wall thickness. Engine builders* who bore to 91mm plus typically have the cylinder wall thickness measured to confirm there's enough 'meat'  in the casting to prevent cylinder distortion, failure, etc. *Personally, I don't build beyond 90mm - have seen M10's have hard-to-keep-cool issues at larger sizes.

 

If you do go that route, I believe Cometic can build you a custom head gasket. -KB

[burndog]

I only use Cometic gaskets and ARP head studs... Keep it tight!!!

[FB73tii]

10 hours ago, burndog said:

I am interested in building a big bore, 10:1, high-rev', big cam, ITB / EFI motor, as a backup to the turbo motor.

 

I looked into maximum bore for an M10 a few years ago, input from trusted FAQ members below. Can you give more information on what your application is? Are you building a race motor with refresh lifetime on the order of 100 hours, or something that you want to last longer? When I see high rev and big cam I think 8,000+ RPM and a 316 or 336 cam. But those cams are going to need much higher compression than 10:1 and race gas to be utilized properly. What is your budget -- $10K, $20K or higher? There are folks working to make an M10 live at 10K RPM, that will be very high maintenance ($$$) engine. In any event, suggest oversize valves and at least mild porting to improve head flow.

 

M10 Block Bore Limit?
Started by FB73tii, Oct 10 2013 03:03 PM
"http://www.bmw2002faq.com/forums/topic/146114-m10-block-bore-limit/"

 

For race engine builders--how far would you feel comfortable boring out an M10 block without sonic testing it first? If sonic tested, what is minimum safe cylinder wall thickness to look for?

 

[M10 Block Bore Limit?: post #2] My M10 block has 92mm pistons.  Unfortunately, I don't know what testing Eric Kerman performed on the block during the build, as I bought the motor used.  I've heard of folks running 93+ mm pistons, but haven't seen them with my own eyes.

 

#3 [M10 Block Bore Limit?: post #3] Information what I have gathered is that 92mm is too much for high powered turbo application but should still be ok for N/A engine. 91mm I would consider safe without ultrasonic testing. This applies only to old 2 liter m10 block from 2002 or NK. Late blocks like something from e30 are weaker.

 

#4 [M10 Block Bore Limit?: post #4] Yeah, the odd  thing is that it depends on what you start with.  The E30 blocks are much more consistent, but there's a lot less metal there overall.  The E21 blocks have a bit less metal- but less potential core shift, so at 91mm, you'd probably be ok. An early 2002 block certainly has enough wall thickness- it's just, is it all where it's supposed to be? If 91mm pistons aren't exorbitant, I'd try it.

 

#5 [M10 Block Bore Limit?: post #5] I measured a typical minimum of .160" (4mm) cylinder wall thickness with an ultrasonic gauge and a mechanical gauge where possible, on a stock-bore (89mm) 1979 E21 block, with a variation on the plus side of up to .030". My block had a moderate amount of rust in it before cleaning. I think 91mm is OK and 92mm is really pushing it.

 

#6 [M10 Block Bore Limit?: post #6] I have never found a block that was not safe at 91mm even for a 13:1+ compression ratio race engine.  I have sonic checked a couple that I was not comfortable going to 92mm with but most have been safe.

 

#8 [M10 Block Bore Limit?: post #8] I've been running a stroker M10 for about 10 years now with a 92 MM Bore. Have a set of CP 12.5 C/R pistons on order so we'll see what a 2313 CC N/A M10 will do on race gas. 

[TobyB]

Turbo.

 

There's no replacement for plumbing nightmares!

 

t

because adding 5% hardly seems worth the effort

[tzei]

I had in my turbo motor 92 mm bore and it didn't go well. Went to 90.5 mm bore and it was ok and i used Eldring gasket (nail type?).

[burndog]

Thanks team,

 

I have a stock bottom end running 8.5:1 under 18psi and it is a Barn fire hoot! I have a ton of parts that will allow me to build a 91mm bore fuel injected monster, but before I did I wanted to know what my limitations were. I can sell the pistons and go bigger or just run what I brung... The reason I said 10:1 is due to living in California with shitty gas no better than 91 octane. So, I thought a 10:1 torque / thumper motor would be a shit ton of fun! I have the block, the head, the pistons and the crank. Just need to determine the Cam with my ITB / Fuel injection...

 

Thoughts?

[tzei]

From Schrick 292 or 304, i wouldn't go higher. And then Catcams turbo version would be nice to try http://www.catcams.com/engines/camshaft-setup.aspx

Also KM cams stage 2 might be an option? If you don't want to go custom cam...

 

[AlanM]

My current "good" engine runs a 92.5mm bore in an E30 318i block with a 2.3 S14 crank.  It is an engine I bought cheaply, but I would only have gone to 91mm.  Runs 10.6 to 1 with Motec and quad throttle body injection, with 165Hp at 6600 rpm at the wheels on 98 RON pump fuel.  Has a custom thin 40 thou standard type head gasket.  No problems so far, but I have seen bore walls that you could flex with your hand at 92mm in other M10 blocks. Maybe mine was sonically tested OK beforehand.

[eurotrash]

Look at doing an S14 block and crank.  You won't get an 8k redline with an 8 valve head, but torque for days at 2.3L or better.  You can do up to 95mm bore.. (93.4 naturally)

[Preyupy]

The standard M10 blocks seem to be good to 91mm and can go to 92mm if you sonic check the wall thickness ( I have only found a couple that had enough core shift in the casting that I would not have bored them that big)  The S14 blocks are cast with a thicker cylinder wall because they started with a bigger bore to begin with.  The biggest problem I see with big bore Turbo engines and S14 blocks is the headgasket sealing between the cylinders.  With a 93mm bore and the bore centerlines in the block at 100mm that means you only have 7mm of headgasket between them.  The gasket WILL move and you WILL have to replace it more often.  On the 3.5 liter M30 and M49 race engines (93.5 mm bore= 6.5mm headgasket width between bores) we get about 18-20 hours between headgasket changes and we use Cometic MLS gaskets.  Be careful if you are using ARP head studs, the ARP torque value is based on the strength of the fastener (90 ft/lb torque with lubrication on a fine thread) This equates to around 180,000 psi PER STUD!!!  This load WILL distort the block so you need to bore and hone the block with a torque plate!  The biggest problem is it WILL DISTORT THE HEAD and you will loose some clamping force at the half way point between the studs, this turns out to be at EXACTLY the same point on the headgasket that it is thinnest between the cylinders and also right under the exhaust ports between the cylinder wall and the water jacket.  At 60 ft/lb torque on the ARP fine threaded studs you are at almost 200% of the clamping force per fastener of the stock course head bolts.  THIS IS MORE THAN ENOUGH!!!!

[burndog]

6 hours ago, Preyupy said:

The standard M10 blocks seem to be good to 91mm and can go to 92mm if you sonic check the wall thickness ( I have only found a couple that had enough core shift in the casting that I would not have bored them that big)  The S14 blocks are cast with a thicker cylinder wall because they started with a bigger bore to begin with.  The biggest problem I see with big bore Turbo engines and S14 blocks is the headgasket sealing between the cylinders.  With a 93mm bore and the bore centerlines in the block at 100mm that means you only have 7mm of headgasket between them.  The gasket WILL move and you WILL have to replace it more often.  On the 3.5 liter M30 and M49 race engines (93.5 mm bore= 6.5mm headgasket width between bores) we get about 18-20 hours between headgasket changes and we use Cometic MLS gaskets.  Be careful if you are using ARP head studs, the ARP torque value is based on the strength of the fastener (90 ft/lb torque with lubrication on a fine thread) This equates to around 180,000 psi PER STUD!!!  This load WILL distort the block so you need to bore and hone the block with a torque plate!  The biggest problem is it WILL DISTORT THE HEAD and you will loose some clamping force at the half way point between the studs, this turns out to be at EXACTLY the same point on the headgasket that it is thinnest between the cylinders and also right under the exhaust ports between the cylinder wall and the water jacket.  At 60 ft/lb torque on the ARP fine threaded studs you are at almost 200% of the clamping force per fastener of the stock course head bolts.  THIS IS MORE THAN ENOUGH!!!!

Thanks for the info Preyupy,

 

I actually used 60 FtLb on my current turbo setup. NO WAY I was going to use the recommended ARP torque of 80!

[kaptanoglu]

Digging up an old thread -

 

If you are doing sonic testing of the wall thickness (for 92mm+ pistons), what findings would be acceptable?

 

TIA

 

(...and yes, this means Sputter had an issue.  We will have to punch out the block to 92mm to keep the original block)

[jimk]

i sleeved a M10 with no issues.  Must have been cut a bunch for the sleeve to fit.  Sleeves were finished to std bore.