m10 piston & rod alternatives

[Duncan2Turbo]

Hi all.

I've read on e30 tech about using oldsmobile quad 4 pistons and rods in an m10 for better rod ratio as well as a cheaper alternative.

Can anyone confirm this or offer any other suggestions? I'm looking for something in the neighborhood of 8:1 forged for a reasonable price.

If it improved the rod ratio as well that would be perfect. Now I'm not looking to save money on parts just to end up spending it at the machine shop.

Thanks in advance guys!

[skipsfcr]

I've heard others mention using small journal sbc rods...I've never heard of anything that conclusively "works". I'm pretty sure Pat "Turboman" Allen of this forum built one of his turbo M10 engines using Toyota 20R pistons.

[themoose]

I've been contemplating such a thing with SBC small journal rods. If you want, you can page Old Guy and see if you can get him to give up his sources for rods and pistons since he's working on a 16v project using a Ford Mustang head.

[Duncan2Turbo]

Yeah I would be interested in finding something conclusive. I've searched but haven't had any luck.

I can page old guy? How would I go about doing that? You lost me...

Toyota 20R, I will check into that.

Building Japanese race bikes years ago we didn't have all the compression ratios, wrist pin placement, bore sizes we do now. So we had to measure pistons in the parts room and everywhere else we could find something we could use.

I still have a kz 900 with sbc pistons in it. So I'm sure we have alternatives out there. With the internet we shouldn't have to measure hundreds of pistons by hand either.

Thanks,

[PatAllen]

toyota 20r, yes but only for low compression, unless you remove a lot from the block deck.

[themoose]

just post a topic with the title "paging OldGuy" and then ask your question.

[Duncan2Turbo]

yes I am looking for low compression ratio pistons.

I'm building another turbo m10 engine I'm going for some serious boost this go round I've got a gt35r that should get me there.

I really appreciate your help. Are these 20r pistons just a swap or what is invloved?

I was really hoping to find something I can use with a longer rod if possible.

Thanks

[Duncan2Turbo]

Toyota 20r and 22r pistons are the same I believe I think the main difference is the head.

I remember from building a 22r with a 20r head to up compression smaller combustion chamber on the 20r head.

As popular as the 22r is I imagine there must be a multitude of options. Im about to check this out.

Thanks a million.

[PatAllen]

Toyota 20r and 22r pistons are the same I believe I think the main difference is the head.

I remember from building a 22r with a 20r head to up compression smaller combustion chamber on the 20r head.

As popular as the 22r is I imagine there must be a multitude of options. Im about to check this out.

Thanks a million.

nope, the dome is quite different. 22r pistons are almost flat while the 20r got a large crown like BMW M10 1.8i pistons, thus the low compression once the dome is zero deck.

It involve taking 0.040 oversize 20r pistons iirc, and decink the block like 0,060 down. the small end bush needs to be reamed 0,0005 iirc, almost fit.

You can still get a set of theses for 200$ with rings and pins, but i think you should consider IE custom made ones.

[Duncan2Turbo]

nope, the dome is quite different. 22r pistons are almost flat while the 20r got a large crown like BMW M10 1.8i pistons, thus the low compression once the dome is zero deck.

It involve taking 0.040 oversize 20r pistons iirc, and decink the block like 0,060 down. the small end bush needs to be reamed 0,0005 iirc, almost fit.

You can still get a set of theses for 200$ with rings and pins, but i think you should consider IE custom made ones.

Thanks again Pat.

Your suggesting custom pistons? One more question if you don't mind. Any source for longer rods or long rod and piston combos aside from custom. I do have a guy I've been buying custom pistons from for 10+ years but I still don't get much of a better deal than anyone else. I'm just trying to trim my costs as much as I can. I would rather not go the custom route but I will I can't find what I need any other way.

[PatAllen]

You should mention exactly your goal in terms of HP and usage, ie race, street,...how much psi ??

I think you are going the wrong route to try to be cheap on pistons on a turbo set-up. Cheap and turbo are two words that does not go well together, altough it is possible depending on the goal itself.

Why do you want to change the rods ? unless you realy change the rpm usage of that venerable M10, the stock ones can handle a lot.

You can get a set of custom pistons for around 600$. The 20r route will need more machining and at the end you will get close to the same amount.

A bone stock fresh M10 with flat tops could even be used up to 250hp with proper fueling and intercooling.

The turbo alone doesnt dictate the final HP figure. Fuel and thermal management is more important, and a GT35 is quite big imho for a M10, if it where me i would get a smaller one to move the power band 2k-6krpm no more. This way you end up with a more versatile and fun machine rather than a super high revving one that is always near its limit to break and make a fondue in the pan.

What fueling will you use and is a proper intercooler in the equation ?

[TobyB]

OK, get your wuzzles in order and call Ireland Engineering. Insist on takling

to Jeff or Jeremy. Jeff gets Ross to make him pistons for less than you can,

and he's very excited about getting the pin higher in the piston

to get a longer rod (Smokey Yunik's Power Secrets explains it all

very well indeed)

In fact, I had to just about beat him over the head to NOT send me the better

stuff (it's illegal in the class I race) because he was so happy with it.

He's your guy. But if you don't know EXACTLY what you want and

why you want it, Jeff will blow you off. Jeremy's a bit nicer,

but Jeff really gets why it all works. Thus the wuzzles.

You will spend about $1200 for good stuff. You will do it once.

AFAIK, there are no rods that will 'bolt in' to an m10/m30-

everything involves some modification. And at that point,

why not just do it right the first time?

...since you asked....

t

[PatAllen]

hum, from a cost perspective and net results, messing up with the rod ratio is very, well...an uneficient modifcation?

If it where me i would spend my money elsewhere.

Does anybody ever quantified the net gains in terms of performance and longevity on a M10 with longer rod ratios ?

just crank up the boost dude'

[Duncan2Turbo]

You should mention exactly your goal in terms of HP and usage, ie race, street,...how much psi ??

I think you are going the wrong route to try to be cheap on pistons on a turbo set-up. I didn't say cheap just an alternative to custom, cheaper

Why do you want to change the rods ? unless you realy change the rpm usage of that venerable M10.

Yes I plan to have this motor spin very fast

A bone stock fresh M10 with flat tops could even be used up to 250hp with proper fueling and intercooling.

My small turbo running 15psi dyno'd 255 which is essentially a stock balanced m10 with a few changes. I plan to double these numbers, seriously

II've been building race engines for 15+ years, now I am running ITBs and a fairly large air air intercooler the gt35r will work well I believe I will build this one to turn some serious rpms

[Duncan2Turbo]

hum, from a cost perspective and net results, messing up with the rod ratio is very, well...an uneficient modifcation?

Does anybody ever quantified the net gains in terms of performance and longevity on a M10 with longer rod ratios ?

just crank up the boost dude'

Longer rods have proven quite efficient for me over the years. It's rather hard to quantify the net gain from longer rod/rod ratio. It's not something easily changed after a dyno run to measure gains. I'd think it would be rare to find an engine rebuilt with only longer rods just to get an idea of gains. You will always ineveitably change more than just the rods making it hard to measure the gains from that alone.

I know pretty much where I want to go with this engine I just haven't mapped out my route turn by turn yet.

Trust me the boost will be cranked on this one.