M42 stroker build begins

[i8ur911]

Sooooooooo, I'm building an M42 stroker. Picked up a used M42 in good shape with trans, ecu and harness for $150

Plans are to use M44 crank, stock rods and S52B32 pistons (we have some at work dirt cheap). The head will get new valve guides, seats and better springs. Valve job and slight porting. Cams will be VAC "hot" cams (I'll get lift and duration and post shortly). Not changing valve size.

Question....I suck at math.....what do I have to do to make those pistons work? Warsteiner, your help would be much appreciated.

I'd love to run itb's, but its not in the budget right now. I have an extremely good tuner that will dyno tune the car when finished so that is not an issue.

I am also doing the M20 single mass flywheel conversion using M20 flywheel and starter with M42 clutch kit and M42 flywheel "spacer".

Any advice would be greatly appreciated

[Warsteiner]

I have not done any work with the M44 crank. I know it can work but others on the list might be able to help you a bit more with all the cam sensor and crank sensor locations. I'm not familiar with the M44 locations. I will repost here what I did with my car and transfer it to an M44 crank.... so you can get an idea of what needs to be done. I do suggest that you get someone who knows a good computer calculation program for compression to make sure you're spot on to where you want to be. I did to make absolutely sure I was in the range of my target compression.


No matter what, all need to be decked and pocketed for the valves as well as dished for desired compression.

I think the M44 head gasket will allow for the 86.4mm piston.

Desired Compression Height = Block height - (Stroke/2) - rod length -piston protrusion out of block
Using stock rods and M44 crank:
DCH= 212-(83.5/2) - 140 -.15
DCH= 212-(41.75)-140-.15
DCH=30.1mm

So you can use any piston of your choice as long as you make the CH 30.1mm So if you go with the US 3.2L 31mm/CH 86.4mm piston you only need to shave off .9mm, then dish it and cut the pockets for the valves. Simple!

Just to give you an idea....for my stroker I used 3.0L US pistons and 138mm rods. I spoke with TEP racing when I was considering going with JE pistons and they said that even a 28.15mm CH was ok. NOW that is with a custom piston and stock rods at 140mm on a M47 crank. It all depends on how much meat you have at the top of the piston.

Compression Height of Stock S50 Piston is 32.8mm with Honda 1.8L VTEC B18C (GSR) 138mm rod

Desired Compression Height = Block height - (Stroke/2) - rod length
Desired Compression Height =212mm - (88mm/2) - ((138mm[Honda rod] - .15mm{protruding out of block}))
Desired Compression Height =212mm - 44mm - 137.85mm
Desired Compression Height =*30.15mm
The DCH is a desirable height.
30.15mm = 212mm - (88mm/2) - 138mm -.15mm*
This tells you that your target compression height is 30.15mm and we have enough meat to shave off 2.65mm from the 32.8mm :-P
Rod needs small end bushing to be drilled to fit 22mm S50 pin.

Again.....do all your math first and then buy your parts. Or use what you have and make it work. BUT I would never deck the head to make up any kind of distance when you have so many other variables such as the HG and pistons and rods. Just my .02


I also did the M20 LWF (11 or 12lbs) with M42 ring gear and kept the original M42 starter. It might be a little bit of work but can be done pretty easily.

HTH

Cheers,
~Ralph

[i8ur911]

Ralph, what do you think of just boring the block for larger pistons with an 11:1 compression ratio? My power goals are 170hp. Is this possible without stroking the motor? I have found an m44 crank, but in all honesty it scares me when thinking about machine work, not being able to explain it correctly to the machine shop, screwing up the data and having the incorrect clearances machined.....costing lots of extra money. I was hoping to build this whole set up (without itb's) for around $2000-$2500. I can get great deals on parts as I work at Turner Motorsport, but don't want to screw up the machine work. And no, no one at work cares about me building an M42. They thinks its dumb, so no help there

[fumstoo]

If I remember right you can bore up to 89mm before you have to worry about anything. Ill give it a quick search to see if I can find proof. And that sucks about the guys at your shop..  They should help regardless. Shit, I helped my little brother turbo his honda and i definitely didnt approve of that.

[wazzu70]

87mm is the biggest most go.

[i8ur911]

The guys at the shop would. They all just give me shit. I'd rather build it "myself" and be able to tell them to suck it, than ask for their help and always here about it. They're all good guys, but I don't want them staying late all the time for a project that isn't theirs and they're not passionate about.

[i8ur911]

Will I see a good power increase with just boring to 86.4mm pistons with 11:1 compression?

[mabeer]

^^^In for this answer as well^^^

[wazzu70]

Raising the compression would add more power, but you would have to make sure you had proper size valve reliefs to avoid contact. Also, you would need to retune your timing map for the higher compression to avoid issues.

[i8ur911]

Ordered my valve springs from Supertech today. Ordering my cams from VAC tomorrow. Should be dropping off head and M20 single mass flywheel at machine shop next week.

I'm going to build the head first, install it on stock bottom end, DIY port and polish intake manifold (upper and lower), port throttle body a bit and then dyno tune to see what power I can get.

Then I'll save some money and do more research for bottom end. I'd really like to go M44 or even M47 crank with custom pistons, 11:1 compression and megasquirt standalone. I like the idea of dbilas itb's too as there is no additional fab work needed to fit and it is a new kit.

[wazzu70]

Thats a nice valvetrain. Curious what numbers you put down!

[Warsteiner]

Just boring the block for bigger pistons will yield more power. Not sure how much, but it will. Be careful with your cam choice....If you go too aggressive with lift and duration and don't have the ummpf of the bottom end as far as torque, then you will be falling flat on your face. You may have better power up top say around 5K and above, but is that really where your normal daily driving is? Just remember to have a game plan for your end result and make sure it makes sense for air in and air out. I'm not really sure where the line is drawn for what the stock exhaust system can handle.

Wazzu70 is right, you will definitely need to retune. You should actually retune after every change to the engine since the parameters have changed and there is definitely more power to be found.

Yes you will gain HP from bigger pistons and cams, but will the torque be able to keep up as well is the question. Supertech stuff is great. I have their valve springs in my S14. Getting some bottom end work with ITB's and megasquirt is a great idea and then you will start seeing some power gains. Again...the power is in the head, so when you port it, make sure that the changes to the rest of the engine match it because too much porting can also make it worse for you as far as torque is concerned.
Doing the flywheel is the biggest bang for the buck in my opinion without tearing the engine apart. They really do make the M42 come alive a bit.

Everything you do to the engine will in some way benefit you in the long run because you know that you will always be on that power quest!! WE all do it in one way or another. Just have a game plan so that your parts that you're getting now will be used later as your engine  develops.

Cheers,
~Ralph

[i8ur911]

Ralph, thanks for the input. I've wondered if the 280/274 cams would be too agressive , but knowing that I'm going to build the bottom end really makes me think that these are the correct ones (for the future worse case scenario). I'm also ordering the vw lifters to lighten up the valve train.

I've read about the harmonic balancer being a problem with higher revving engines. I'd like to be able to rev to 7500rpm. Is this possible? If not, how can I make it possible?

What is the limitation on the exhaust side? I'm thinking maybe custom header; 4 into 1??? I just installed a Supersprint catback.

Any other thoughts?

[wazzu70]

I think the 269/269 would be a better all around setup. It has nothing to do with the bottom end and everything to do with the usable rev band. The catcams grind (VAC cams) is a really aggressive ramp profile so keep that in mind.

The damper does not seem to be a problem. I4 engines are much softer on
The torsion damper than the long I6 cranks at high RPM.

Supersprint makes a header for the M42, ebay has knockoff copies. The M42 manifold is OK stock, but with better cams a longer tube proper header is nice.

Just my thoughts

[Warsteiner]

When dealing with cam choice you have to look at all aspects of the engine. Where is the most time spent in the rev range, what kind of power are you trying to achieve etc... Having said that, too big of a lift and too long of a duration on an otherwise stock motor is not a good a idea. The car will fall on its face in the low end range and probably scream up top in a very small rpm range. Cams do have an effect on bleeding off compression so the bottom end choice with cam choice is kind of important. You can have a high static compression and put big cams in and bring down the dynamic compression considerably. It all needs to be worked out before you build the engine

I have seen M42's run 7500rpm all day long on the stock balancer. I don't like internet myths....

I really don't know what the limitations are on the stock exhaust. I would say that the headers are probably good for a reasonable HP gain without choking off the engine. See if MM changes their headers when they do their 2.1L strokers. I'm thinking the choke point is after the header and possibly even after the cat.

Cheers,
~Ralph