b23ft buildup/2nd os mahles/decking block

RR · 07-29-2004, 12:40 AM

Hey guys,
Yeah, block's at machine shop, bored 2nd oversize, 96.6mm, and was informed that the oem headgasket will still work for 2nd oversize holes.
However, if I deck the block for 'good squish', +.007 to +.015, will the oem headgasket still accept the 96.6 piston? Rephrase...does the headgasket allow the 96.6 to penetrate or will it interfere with the piston coming out of the bore ever so slightly? I guess I could just get the gasket and check it out, but we're about to assemble and measure and start cuttin'. Any one know for sure?
Thanks,
RR

07-29-2004, 01:10 AM

RR,

the Elring HG will fit over the 96.6mm mahles just fine. you are good to go. and shoot for deck height of at least +0.010in. That way, with compressed thickness of 0.047in-0.049in, you'll have squish clearance under 0.040in.

the elring HG would allow a 96.7mm diameter piston to pass through easily; so no need to worry about that, okay? So do the test assembly, get the deck height measured, and deck the block for some very good squish. if you go with the +0.015in, you will be at about 0.032in squish.....OH YEAH!!

[just got my 93 230ET block back: measured and decked for +0.012in deck height.....0.035in squish....YES!!!]

TF

WeezilUSA · 07-29-2004, 04:50 AM

Where'd ya get +2 pistons?

Canuckvolvo · 07-29-2004, 10:49 AM

Just a little testament to stealth's squish ranting (although I'm pretty sure I'm preaching to the converted, RR). Looks like I've (roughly) found the limit of my new engine, on 87 octane. Starts to ping ever so slightly at about 8psi. I'm VERY happy with that, I should be able to run quite a bit more on 92. And so far my mileage looks really good in the city too, haven't taken it on the highway yet. I'll publish some numbers when I get some good data.

This is on k-jet, with 12deg ign advance, 9.1:1 CR, 405 head with polished chambers. My squish ended up around 0.045" so it could have been even better. I should mention I'm at 3500ft as that will have some effect- I'll find out when I'm on the coast next weekend. I'm sure with some minor dizzy mods to pull a little more timing, maybe running a little richer and using some good gas I will quickly find the limits of my M46

Thanks again for the advice Tom and others!

RR · 07-29-2004, 09:01 PM

Thomas,
Thanks for the confirmation about the clearance. I'm gonna shoot for the max, +.012 to +.015, if I can talk my machinist into that. Just kiddin', he's become a friend and concerned about the reuseability/refurbishability of the block if we get too crazy, but I say what the hell. I'm gonna squish those forged pistons like they ought to be. Well, you know what I mean.
Anyway, I got the b23ft forged bullets, 2nd os, from AmBoss in New England for 85.55 ea, which included the rings and pins, plus about 50. shipping from Germany. I'm pleased.
Now just gotta decide which car to put the b23ft into: 83 242glti or the '91 780 w/168k...
Ah, that's easy, the 780 is the best drivin' Volvo I've ever driven.
Thanks all,
RR

07-29-2004, 10:58 PM

RR, you're welcome.

I can understand the concern about taking too much off the deck now so that sometime in the future there would not be any room to take a few thou off the deck to make it flat again.

Because of that, you might want to just go plus ten to plus twelve this time around. Plus ten will put you at about 0.037in squish....within the tight squish area.

In the future, you would then still have a few thou to work with.

Two things that could cause a need to worry about the deck height in the future would be:

....whether or not the main bearing bores would need to be align honed. That usually raises the crank at least two thou.

....whether or not there would be a need to resurface the block to restore flat.

If, in the future, you needed a few thou to resurface with or to align hone the mains, you can compensate for that in the rod C-C length...via resizing the big end and rebushing the pin end and offset honing the pin bores to shorten the C-C length. You can get back a few thou that way [anywhere from about two thou to about six thou]. And in case you're wondering, doing that won't hurt the rod stroke ratio enough to even be concerned; 1.81:1 is plenty enough to start with.

If you go plus ten to plus twelve, you will be good to go squish wise. If your guy align honed the mains this time then you could go plus fifteen [because the crank will have already been raised this time; and it would be rather unlikely to have to do that again]. Talk it over with him.

Doing the test assembly will tell a lot.

good luck

TF

...and yes: Athal is quite correct......squish is good!

which reminds me....Athal, when you go to the coast, you might need to retard the base tiiming while you're down there; and/or you probably will need higher octane down there. What doesn't ping at three thou probably will ping at sea level. Be prepared.

07-29-2004, 12:40 AM	#1
RR Board Member Join Date: May 2003 Location: Back in North Texas	b23ft buildup/2nd os mahles/decking block Hey guys, Yeah, block's at machine shop, bored 2nd oversize, 96.6mm, and was informed that the oem headgasket will still work for 2nd oversize holes. However, if I deck the block for 'good squish', +.007 to +.015, will the oem headgasket still accept the 96.6 piston? Rephrase...does the headgasket allow the 96.6 to penetrate or will it interfere with the piston coming out of the bore ever so slightly? I guess I could just get the gasket and check it out, but we're about to assemble and measure and start cuttin'. Any one know for sure? Thanks, RR

07-29-2004, 04:50 AM	#3
WeezilUSA Fair Enough... Join Date: Nov 2002 Location: Vancouver WA	Where'd ya get +2 pistons? __________________ R-Sport International Customer Service For all RSI related messages, please email me (no PM)... Thanks! ben@r-sport.org

07-29-2004, 10:49 AM	#4
Canuckvolvo Drunk as **** Join Date: Nov 2002 Location: North 604...no 778	Squish = Good Just a little testament to stealth's squish ranting (although I'm pretty sure I'm preaching to the converted, RR). Looks like I've (roughly) found the limit of my new engine, on 87 octane. Starts to ping ever so slightly at about 8psi. I'm VERY happy with that, I should be able to run quite a bit more on 92. And so far my mileage looks really good in the city too, haven't taken it on the highway yet. I'll publish some numbers when I get some good data. This is on k-jet, with 12deg ign advance, 9.1:1 CR, 405 head with polished chambers. My squish ended up around 0.045" so it could have been even better. I should mention I'm at 3500ft as that will have some effect- I'll find out when I'm on the coast next weekend. I'm sure with some minor dizzy mods to pull a little more timing, maybe running a little richer and using some good gas I will quickly find the limits of my M46 Thanks again for the advice Tom and others! __________________ 1995 945Ti, cushy winter ride aka Darth Wagon 2006 Suzuki GSF650 Bandit

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07-29-2004, 01:10 AM	#2
stealthfti Guest	RR, the Elring HG will fit over the 96.6mm mahles just fine. you are good to go. and shoot for deck height of at least +0.010in. That way, with compressed thickness of 0.047in-0.049in, you'll have squish clearance under 0.040in. the elring HG would allow a 96.7mm diameter piston to pass through easily; so no need to worry about that, okay? So do the test assembly, get the deck height measured, and deck the block for some very good squish. if you go with the +0.015in, you will be at about 0.032in squish.....OH YEAH!! [just got my 93 230ET block back: measured and decked for +0.012in deck height.....0.035in squish....YES!!!] TF

07-29-2004, 09:01 PM	#5
RR Board Member Join Date: May 2003 Location: Back in North Texas	Thomas, Thanks for the confirmation about the clearance. I'm gonna shoot for the max, +.012 to +.015, if I can talk my machinist into that. Just kiddin', he's become a friend and concerned about the reuseability/refurbishability of the block if we get too crazy, but I say what the hell. I'm gonna squish those forged pistons like they ought to be. Well, you know what I mean. Anyway, I got the b23ft forged bullets, 2nd os, from AmBoss in New England for 85.55 ea, which included the rings and pins, plus about 50. shipping from Germany. I'm pleased. Now just gotta decide which car to put the b23ft into: 83 242glti or the '91 780 w/168k... Ah, that's easy, the 780 is the best drivin' Volvo I've ever driven. Thanks all, RR

07-29-2004, 10:58 PM	#6
stealthfti Guest	RR, you're welcome. I can understand the concern about taking too much off the deck now so that sometime in the future there would not be any room to take a few thou off the deck to make it flat again. Because of that, you might want to just go plus ten to plus twelve this time around. Plus ten will put you at about 0.037in squish....within the tight squish area. In the future, you would then still have a few thou to work with. Two things that could cause a need to worry about the deck height in the future would be: ....whether or not the main bearing bores would need to be align honed. That usually raises the crank at least two thou. ....whether or not there would be a need to resurface the block to restore flat. If, in the future, you needed a few thou to resurface with or to align hone the mains, you can compensate for that in the rod C-C length...via resizing the big end and rebushing the pin end and offset honing the pin bores to shorten the C-C length. You can get back a few thou that way [anywhere from about two thou to about six thou]. And in case you're wondering, doing that won't hurt the rod stroke ratio enough to even be concerned; 1.81:1 is plenty enough to start with. If you go plus ten to plus twelve, you will be good to go squish wise. If your guy align honed the mains this time then you could go plus fifteen [because the crank will have already been raised this time; and it would be rather unlikely to have to do that again]. Talk it over with him. Doing the test assembly will tell a lot. good luck TF ...and yes: Athal is quite correct......squish is good! which reminds me....Athal, when you go to the coast, you might need to retard the base tiiming while you're down there; and/or you probably will need higher octane down there. What doesn't ping at three thou probably will ping at sea level. Be prepared.