Piston type advise- any VW guys on here?

[waferman]

Hey all, I would like to stroke my engine from 1.8-2.0L, but I cant get over the price of custom pistons to go with the 1.8L head. A friend of mine mentioned that aircooled VW pistons are a fraction of the cost of BMW pistons, and Malhe makes them; he bought a set last year for like $179. Does anyone know of VW pistons that will fit a stock bore, or a first oversize for our bimmer mills (89.xmm)?

Thanks,
waferman
83 320iS project

[kdanielson]

I have also thought of this... VW air cooled pistons come in two compression heights-"A" for stock stroke and "B" for stroker motors-the thing is, I don't know what the compression height is on those two types. I think they come in dia from 85mm up to 94mm. If you are going to bore it you might as well go to 92mm (or at least 90.5mm, another common overbore) the machine shop will charge the same.

Try the shoptalkforums.com, someone on there should be able to tell you. Go to the the type 1 performance forum-that's where the stroker guys hang out.

ken

[DJProfessor]

I have also thought of this... VW air cooled pistons come in two compression heights-"A" for stock stroke and "B" for stroker motors-the thing is, I don't know what the compression height is on those two types. I think they come in dia from 85mm up to 94mm. If you are going to bore it you might as well go to 92mm (or at least 90.5mm, another common overbore) the machine shop will charge the same.

Try the shoptalkforums.com, someone on there should be able to tell you. Go to the the type 1 performance forum-that's where the stroker guys hang out.

ken

you are talking about aircooled, my old bread and butter......honestly the pistions don't come in two different "heights" what they come in is two different forms, forged and cast.....your compression ratio gets set by shiming the cylinders. anything bigger than 87 slip ins you have to bore......however the 90.5 and 92's will fit in the same size hole....but think about that for a minute. they make the cylinder walls much thinner on the 92's, and thereby have problems with cooling. 90's are the widely accepted size for durablitiy and longevity over 92's which tend to have warpage problems and other issues.....now 94's you have to bore bigger than the 90/92 and it is a common misconception that they run hotter than 92's, they don't.

also keep in mind anything bigger than 74 stroke you have to clearance your case and anything bigger than 87 jugs you have to punch out both your case and your heads.......now you can make a lovely stroker 1776 by running the 74 stroke crank and 87 slip ins and be good to go however....

any other questions hit it up.....

[DJProfessor]

and i totally missed the boat on your question......you have to pay to play with bmw and i know of no one that makes uber cheap air cooled priced pistions for our boats.........

[greggearhead]

you are talking about aircooled, my old bread and butter......honestly the pistions don't come in two different "heights" what they come in is two different forms, forged and cast.....your compression ratio gets set by shiming the cylinders.

Um, you are totally wrong and Ken is right. Scary you call it your bread and butter and don't realize there are A & B piston sets for different compression heights. Compression *can* be fine tuned with shims. Not the only way to "set" it.





anything bigger than 87 slip ins you have to bore......however the 90.5 and 92's will fit in the same size hole.


No, you don't bore - you have to machine the cases and heads for clearance on an air-cooled VW, but he was asking about just using the pistons, not the cylinders anyway, so it doesn't matter. I won't get into the whole thick-wall/thin-wall air cooled argument.

Waferman, see if you can check all the specs on the pistons to see if they will work dimensionally, and then talk to your machine shop to see if they would be up for it. Heck, one of the old-school VW guys used Datsun pistons in a Scirocco because it was cheaper. Worked, too, but he really knew his stuff. Too often, it will require a custom rod, or some more custom machining that makes it not worth it in the long run, but it is free to research.

[DJProfessor]

Um, you are totally wrong and Ken is right. Scary you call it your bread and butter and don't realize there are A & B piston sets for different compression heights. Compression *can* be fine tuned with shims. Not the only way to "set" it.

never seen the "A & B" sets for larger aircooled pistons in all my years of dubbing, always was the compression set with shims for type I motors when going stroker.....however yes they did make two different compression ratio pistons for the stock 85.5 bore. but personally never saw it for 87 and up....


No, you don't bore - you have to machine the cases and heads for clearance on an air-cooled VW, but he was asking about just using the pistons, not the cylinders anyway, so it doesn't matter. I won't get into the whole thick-wall/thin-wall air cooled argument.

indeed you are correct, my terminology is a bit off. "bore" is the aircooled slag that i am use to tossing out. you don't "bore" out the cylinders in the traditional watercooled motor sense, you "bore" out the head and the case to accept the larger cylinders/pistons of the aircooled motor.......yes i do know the diffference, just please excuse my air cooled slang.......and yes the thick wall/thin wall arguement is about as dead as a dead horse and i have friends that ran 92's with no problems and an equal number of friends that ran them with problems......i prefer to stay on the side of the fence and just site the reputable sources (Berg for one) that make the thin wall/thick wall debate
........

[greggearhead]

I think you are misunderstanding the term "compression height" - that doesn't mean setting the compression ratio or anything. It is a term for the wrist pin height. You don't use an A or a B set for setting compression ratio. You use one or the other depending on your stroke and rod length.

[DJProfessor]

I think you are misunderstanding the term "compression height" - that doesn't mean setting the compression ratio or anything. It is a term for the wrist pin height. You don't use an A or a B set for setting compression ratio. You use one or the other depending on your stroke and rod length.

wait a minute you lost me......if you vary the wrist pin height you are changing the compression ratio.....basically it would be doing the exact same thing that adding/subtracting shims would do on a stroker motor.....

when i went 2110 i had to shim out my cylinders to get the desired lower compression....if they made (so ok, maybe they do now, a bit rusty i will glady admit....and on two hours sleep right now) the 90's with offset wrist pin heights i wouldn't have had to shim as much or at all depending on the offset......

[waferman]

OOOOOOOOOOOKayy.....so it looks like there are no 'it wont work at all' comments, so all I need to do is try to match up wrist-pin hight? Which is 'compression hight'?

Thanks for the dialog guys; I knew there was some dubbya guys here !(Vdubbya not George dubbya:stickoutt )

waferman

[DJProfessor]

have you seen pistons with dish and those without? that 'dish' affects compression ratio, as does the height of the piston in the bore at TDC.....so yes for water pumpers you would have to be weary of the height in the bore as well as any dish/notches in the piston......they sell kits you can use to calculate the compression ratio when getting custom.........likewise your head also effects compression ratio and the headgasket spacing, deckheight.....blah blah blah......

[Jmabarone]

if those pistons are indeed as cheap as you saw them, then that sounds like an interesting proposition.

not trying to thread jack, but I saw a set of M10 2.0l pistons on ebay and was wondering how they'd work. 2.0l, 89mm bore flat top Nural pistons. I want to build an engine for my car and 90 buxs shipped is fairly cheap for pistons IMO.
Jake

[greggearhead]

wait a minute you lost me......if you vary the wrist pin height you are changing the compression ratio.....basically it would be doing the exact same thing that adding/subtracting shims would do on a stroker motor.....

when i went 2110 i had to shim out my cylinders to get the desired lower compression....if they made (so ok, maybe they do now, a bit rusty i will glady admit....and on two hours sleep right now) the 90's with offset wrist pin heights i wouldn't have had to shim as much or at all depending on the offset......


OK, sorry to go so far off thread topic, but...

Shims for varying compression ratio are in thicknesses of .010", .020" etc. The difference in pin height on a set of A vs. B pistons for a Type I is around 1/2", .500" or somewhere therebouts (Ken - help me out it has been a too long). Using a B piston in place of an A piston would mean your piston would go into the heads aroudn 1/2" - you don't use different compression heights to set compression. (there are always exceptions and if you wanted a custom rod length or special length cylinders, etc. - but funky custom engine stuff is always out there, I am trying to explain the basics.) I don't think you want to use 10-25 shims to try and make up the difference of the wrist pin height.

[DJProfessor]

you don't use different compression heights to set compression. (there are always exceptions and if you wanted a custom rod length or special length cylinders, etc. - but funky custom engine stuff is always out there, I am trying to explain the basics.) I don't think you want to use 10-25 shims to try and make up the difference of the wrist pin height.

you do use different wrist pin heights on pistons to set compression, more so with the watercooled crowd than anything. i mean go read up on the stroker m20 2.7/3.0 thing with mix matching the super eta stuff with the I stuff, M stuff, etc, etc....a piston with a dish is no different than say a piston with a slightly lower wrist pin height. both will lower the compression. and there are companies out there making custom pistons for this popular swap with custom heights for certain compression ratios. making a piston with a lower/higher wrist pin height is far cheaper than making dish pistons when it comes to custom work.

[kdanielson]

Well, Here's what I know from modern engine building...

Yes, lowering your piston in the bore WILL lower your compression ratio BUT it is absolutly not the best way to do it... Once your piston gets much more than .060" (including the compressed gasket) from the cylinder head you loose all benifit of turbulance in the A/F mixture generated as the piston reaches TDC and the A/F mixture is "squished" between the piston top and the "quench pads" on the head- This is what makes the Chevy Vortec and MOPAR "High Swirl" heads work so well. Without that turbulance your engine will tend to run rich and be hard to tune due to the less complete combustion. If your combustion chamber volume generates too high of compression with flat top pistons, a dish machined in the mirror image of the chamber is the best way to lower it. Yes, it cost's $$ to make pistons like that but it's the smart way to lower your compression ratio and still maintain good combustion.

State of the art engine builders set the piston deck height for .035"-.045" including the compressed gasket, this often requires maching the block deck. State of the art aircooled VW engine builders are using different pin heights, rod lengths, and shims to get their deck height in the same range- they don't use head gaskets-they lap the cylinders to the head sealing surface and run it metal to metal.

There is ALWAYS more than one way to build an engine but there is usually a single BEST way to do it.

I have a long term aircooled VW project but it uses the type4 engine used in buses and the Porsche 914/4. It's a 72mm stroke with 94mm bore for 1999cc. I used to frequent Shoptalkforums.com frequently-lots of great tech stuff going on over there.

Now, this thread has me thinking... Good light weight forged rods in various lengths are available at reasonable prices for aircooled VW's-if the rod width is compatable with our cranks this could make building a radical engine a little more cost effective. Rod bearing dia. is very easy to modify if the VW rods use a smaller dia bearing (opens the option of offset griding the crank for increased stroke) and more expensive but possible if the bearings are larger dia.

Someday, when I have the time and ambition I will get all the dimensions of availabe pistons and rods and see what is workable... too much work and too many projects right now so if someone wants to do some reasearch you could be the savior of the M10 performance builders... but then agian, maybe NOTHNG is compatable, who knows until it's looked into.

ken

[waferman]

So, at the end of the day Im still at a loss as to what to do here! Good info though. Thanks for your input, Ken, your name shows up in every 3rd search I do on engine rebuilding or 'stroker m10'. I wish I could understand more of it:(

waferman

[Jmabarone]

wafer, that set of pistons I was talking about is on ebay, just type in 'bmw m10' and I'm sure you're bound to find them. $89.99 shipped.
Jake

[waferman]

Thanks for the heads up, but those wont do any good with my 1.8L head; my compression would be way low. Its the offbeat piston options I need...Non JE or MM. However, did you see that individual throttle body setup? WOW!

waferman

[greggearhead]

http://cgi.ebay.com/ebaymotors/BMW-M10-40mm-Fuel-Injection-Throttle-Bodies-High-Flow_W0QQitemZ8026496506QQcategoryZ36474QQssPageNa meZWDVWQQrdZ1QQcmdZViewItem

These throttle bodies? Hey Ken, these look like SPICA Alfa units, don't they?

[Jmabarone]

Alfa Romeo 40mm throttle bodies.
they are.
Jake
P.S. couldn't you use those pistons with a 2.0l crank and rods and a 1.8l block?

[jrcook320]

P.S. couldn't you use those pistons with a 2.0l crank and rods and a 1.8l block?
Yeah, thats what I did, but your CR will be around 8:1.

[Jmabarone]

8:1 CR is what a 1.8 is, correct? 2.0l is 8.5:1 I believe.
Jake

[waferman]

:( No. The 1.8L has an 8.8:1 CR to make up for the shorter throw crank. The pistons when combined with a 2.0L crank will hit the 1.8L head.

I just got an answer back from the 02 forum about using tii pistons. Lots of guys, or at least a few there have gone to a 1.8i head and FI while keeping the 2.0L bottom end. Tii pistons of any year will not work; one guy tried it. It seems like custom pistons would be my only option. No plug and play action here:(

JRCrook, are you happy with your 8.0:1, or do you wish that you hadn't used the flat tops?

waferman

[Yonkers320is]

the 8.0:1 or 8.1:1 will work great with a big turbo.....

[waferman]

Ok, here is what I found. The 92mm VW pistons have the same wrist-pin hight as the BMW pistons, Malhe makes em, and they are inexpensive. Not going to go there though. Thanks for your help!

waferman

[Helmetboy]

http://venolia.com/imports.html

Try these guys, I've seen their pistons and they look great, plus they are not that expensive.

[waferman]

No prices on thier web page + No return policy+ no 1-800 number = $$$ and too much trouble. Thanks though. Besides, they only list the 1600, 2002 and 6cyl applications.