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> How much variation in Deck Height, do you tolerate?
nebreitling
post Mar 10 2005, 05:06 PM
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title says it all. How much variation between cylinders in Deck Height do you builders tolerate? i'm shooting for no more than .001, but i'm curious how steadfast i need to be in this...

damn KB 96's stick out of the jugs, mmm, just a little bit...

current deck height:

#1 -.204
#2 -.203
#3 -.215
#4 -.214

Desired deck height:

055-056

off to have the machinist whittle out some .25 cylinder spacers (!)....

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Demick
post Mar 10 2005, 05:16 PM
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I assume you missed a decimal place in those numbers, and meant:

#1 -.0204
#2 -.0203
#3 -.0215
#4 -.0214

But I don't know how you measured deck height to the nearest 10 thousands of an inch.

So you really need .035" shims.

Just be sure and tell your machinist to make some .035" shims - not .25 (he is not likely to read your mind and know you missed a decimal point).

Demick
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MecGen
post Mar 10 2005, 05:16 PM
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Hi Dude
Both motors I did, stuck to the 001 - 002.
But neither needed spacers machined, Its been a long time, 10 years, but I remember finding spacers locally.
I think you might have a spacer issue, but maybe double check the piston hieght to make sure its not a "machinist" error. Take your time here, very important to check/fix deck hieghts, makes it very reliable.
Maybe some engine guru gonna help... maybe even by the time I post...
Thumbs up
Cheers

Joe


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Demick
post Mar 10 2005, 05:18 PM
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Hold on a sec. If the KB's stick out of the barrels, then you have negative deck height. Your shims would need to be .020+.055=.075" thick.

Demick
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bondo
post Mar 10 2005, 05:33 PM
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Hmm, what if he didn't miss a decimal place but has the wrong pistons or rods? That would be quite a shim!
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Britain Smith
post Mar 10 2005, 06:06 PM
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Well, my engine called for a 0.09 shim but I am running 7.4:1 compression. Can you say BOOST!

-Britain
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nebreitling
post Mar 10 2005, 06:23 PM
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well, it would appear that i may have the wrong pistons....

yes, they stick out of the jugs about .200 (yes, nearly 1/4 inch)

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lapuwali
post Mar 10 2005, 06:28 PM
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QUOTE (nebreitling @ Mar 10 2005, 04:23 PM)
well, it would appear that i may have the wrong pistons....

yes, they stick out of the jugs about .200 (yes, nearly 1/4 inch)

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As I recall, the pistons you seek have the wristpin bosses located much closer to the crown. It's also possible you have the wrong rods. Insert the usual "combo" comment here.
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nebreitling
post Mar 10 2005, 06:39 PM
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yup, all checked. it's the wrong pistons... (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) i'll get this bitch put together some day....
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redshift
post Mar 10 2005, 07:05 PM
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Nathan... I am sorry, buddy.

Never helpful, always empathetic..



M
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MecGen
post Mar 10 2005, 07:13 PM
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Cool
Better now than later $$$
At least its gonna be rite
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Its a burn when you get f**ked by new parts, the first one I did, I took telephone advice and ended up building a completely mixmatched bullshit motor, my loss = 1500$
Glad you didn't go my way
cheers
Joe

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nebreitling
post Mar 10 2005, 07:32 PM
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thanks guys. the vendor is making good on this, so that's as good as the situation can get. what's another weekend, really? i should recieve the new pistons saturday. back to the machine shop on monday for balancing..,. and then,,,, whenever i have the damn time, put it together.

should be a fun little 2056 at 9.5:1 compression, mildish cam and carbs.
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Jake Raby
post Mar 10 2005, 09:07 PM
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My tolerance is .004 between ALL cylinders and .001 between cylinders on the same bank.... More than that and you are asking for a head leak.
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Mueller
post Mar 10 2005, 09:09 PM
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QUOTE (Jake Raby @ Mar 10 2005, 08:07 PM)
My tolerance is .004 between ALL cylinders and .001 between cylinders on the same bank.... More than that and you are asking for a head leak.

hopefully I'll be doing this testing very soon...I noticed my credit card has been charged so that is a good sign that my 78mm crank and other goodies are on the way (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/smash.gif)
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MattR
post Mar 10 2005, 09:10 PM
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I had the same problem with my KB cylinders. The supplier sent me the wrong cylinders. No package... I had to figure out the hard way that they were the wrong offset pistons. I got new pistons, a little work to trim the piston to get the desired cr, and i was good to go!
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nebreitling
post Mar 10 2005, 11:11 PM
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QUOTE (Jake Raby @ Mar 10 2005, 07:07 PM)
My tolerance is .004 between ALL cylinders and .001 between cylinders on the same bank.... More than that and you are asking for a head leak.

i can do that. thanks, everyone, for the input!
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Jake Raby
post Mar 10 2005, 11:12 PM
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Mueller...
Your stuff is all done and shipping tomorrow...

Came out really sweet!
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Demick
post Mar 10 2005, 11:34 PM
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QUOTE (Sammy @ Mar 10 2005, 06:56 PM)

.020 variation means nothing IMO except maybe for bragging rights.

.020 variation translates to about 1/2 point of compression. That's an awful lot! That's kind of like installing USA pistons on 2 cylinders and Euro pistons on the other two. I wouldn't build my engine like that.

Demick
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nebreitling
post Mar 10 2005, 11:58 PM
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i agree! i assume he meant 002...

still, it doesn't take an enormous effort to spec these things out to the thousanth...
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MarkV
post Mar 11 2005, 04:44 PM
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Question?

I measured my deck height and it is .013 to .014 on all 4 cylinders. Going to run .040 spacers to give me a deck height of .053 to .054. The problem is that one of the combustion chambers measures 59cc's and the other 3 measure 57cc's. Can I make up the difference by running bigger spacers on the 3 - 57cc cylinders? Won't that cause a leak in the 4th cylinder? If I just put it together with the .040 spacers I will have one cylinder that is 8.7 to 1 compression and three that are 8.5 to 1. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)
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