Adam C

So the question arises, what is the thinnest cylinder wall acceptable?

What is Mark A running - deck or no deck? That's all I want to know.

BC

You're right Adam. I just assumed wrongly that you would try and keep your bore. I see now after reading more thuroughly that you would do as I plan for my second block with the GTS crank, which is to plate, then nikasil for JE pistons.

heinrich

I think it's safe to say you should not go for it. I'd call Marc and hear what he can do for you, but I also know that that route often leads to severe cost. Were it I, I would call this one a coffee table and obtain another block.

Vilhuer

Would filling up lowest 1/3 of water area around cylinders with block cement help to make thinner than .250 wall usable? I would think filler and deck plate together should have some meaningful effect in strenght.

heinrich

Didn't I read about a cylinder strap somewhere too?

blau928

What about just sleeving it instead..?

FlyingDog

Erkka, that's exactly what I was going to suggest.

Mark Anderson

When I did my first stroker I used a 104.5 pistons and my walls were as thin as .220. I was told by many that it would never work but I tried it anyway. I've also never tried any kind of deck plate or reinforcement but so far it has not been a problem. For some this is all about an engineering excercise. Bob Devore (founder of Devek) seemed happiest when things broke. It gave him a chance to improve on things. He told me that every weekend he did not race gave him more funds to spend working on the car. That's what made him happy. For me it's the opposite. I just want to race. My current motor ingested some debris over 1 year ago and as a result I have one cylinder with only 80 lbs. It has not gotten any worse and it keeps running just fine. Could it be better? Sure but I'd rather be racing.

heinrich

... eighty pounds ... that is a testimony tothe engine if I've ever seen one.

Adam C

Hah! there you have it. Thanks Mark.

What else is there to talk about?

BTW, Adam B - I'll sell you the block out of my '87S4 as soon as it comes out, if you are interested.

rob rossitto

punched mine out to 104mm, left with about .235" (85 block), but w/the .010" nicom coating, it's almost like having a sleeve, cause the nicom is so hard (ie has to be finished honed w/a diamond bit)...

was thinking about a blower too, but getting a 6.4L compression under 11.3:1 was an exercise in itself, since you simply run out of room on the piston to make enough volume w/out trashing the quench, moving the oil ring into the pin area, etc...

think I ended up w/about 35cc dish volume w/a custom set of JE's, and that was pushing it... also had a nick on a cylinder that requried knocking off about .010" extra off the surface, so my original 968 copies were .025" out of the hole... when lowering comp ht, the dish goes away, so you have to start digging to make more volume...

IIRC, mark runs a pretty high compression w/alusil bores, so if you're going NA under 11.3:1 or so, I suspect your walls are fine, especially w/nicom... just my .0002cents...

Adam C

Interesting, Rob. I was also thinkingof a blower in the future. I am not technically profficient enough to know why you need a lower compression motor for a forced induction application - could you enlighten?

blau928

Adam C,

I'm not Rob, but I will say that it has to do with pressure, and heat... The word Detonation does come to mind, the evil enemy of any engine...

The mean cylinder pressure ahs to be controlled.. If you simply turn up the pressure, things get very hot very quickly, and your engine will be toast..

A static CR of 11.3 : 1 will have a hotter charge with forced induction of similar air mass... In addition, the volume of the chamber will be affected by the static CR... Lower Static CR will allow the cylinder to be filled with more air, fuel, and that is where the power comes from..

If you fill the greater mass of air and fuel into a smaller volume cylinder, it will get warped very quickly..

I could run throught the science and many equations, but it has been done many many times before on this forum... I'm sure if you search, you'll find a lot of info..

In any event, if you have 11.3 : 1 Compression, and crank up the "boost" you will have a melted piston really quickly... Oh, and more "boost" does not necessarily mean more power... As always, "It depends...."

Regards,

rob rossitto

yeah, what richard said, he-he,he-he..... seriously though - I'm probably one of the last guys here to ask (not a guru by any stretch), but there is a TON of rennlist/928 stuff on the issue...

but since you did ask(uh oh) - IIRC, around 7:1 and up to about 9.5:1 seems to be what most of the boostards agree is the optimal range, depending on how much boost you're going to cram in there... think that's one reason brendanC/tim m. and others decided not to use so much stroke w/blower motors (also less rod angle, etc)

FWIW, if you stroke and blow (easy now), IIRC the centrifical units seem to be in vogue (ie ck out shaark89's blown 6.0L track monster, tim M's new blower motors), as they don't come on as fast on the bottom end as the twin screw/roots stuff, so your drive train stands a chance... of course, pulleys are everything in that regard, so I suspect you can do whatever to a point as long as it's designed accordingly...

that said, I'm exploring NOS w/my stroker(50-75hp only), as I've been told by many "pros" it's just fine w/higher compression motors, and it does eliminate some stress/heat when you don't feel the need for tire melting in 3rd/4th/etc... relatively inexpensive if you're not on the bottle all the time too (rather have a bottle in front of me than a frontal lobotomy)...

IMO, blower motors really are a breed/design unto themselves vs NA stuff, so you gotta decide up front what it's going to be when it grows up... (unlike me - who hasn't grown up or decided - ha!)

hope this helps...

BC

...I heard my name. I can't speak to actually having a running, stroked, SCed engine - but I sure have spoken to ALOT of people about pistons, rods, custom versions of each, etc.

Its funny that the word "digging" came up on the compression issue. I have been trying to figure that out myself for the second engine I am acquiring parts for (first engine for 89 will be stock everything except for heavy temp coating on the piston crown and a cometic gasket) - I'll have a slightly bored engine (hopefully deckplated - hi Dave at Motorsport) - but I have been well warned by JE to watch HOW much I'm gonna bore - as it will change where I can put the rings and compression level when combined with custom rods and the GTS crank I got from Ebay (poor man's stroker) ... It was way beyond me but Gary at JE also mentioned a year or more ago something about the flame propagation of a VERY LARGE and wide piston.

This all means nothing to the stroker NA engine that this thread is about however, except that I still say deck it if it can be done and cement the bottom of the block. A nice 6psi intercooled on Forged pistons and 11:1 compression won't hurt that engine TOO much, as long as there is proper control of the fuel and spark with knock sensors and maybe some exhaust temp readers.

Tim's engines are at 101 I think - only a small increase in bore size combined with a stroker crank - but not 95.25 as the devek and 928intl batch cranks are. I think its a moderaly lesser measurement then that. Exactly what I have no idea - ask Lag, Murph, or Z. - Hey where has Z been by the way?