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914World.com _ 914World Garage _ How much variation in Deck Height

Posted by: nebreitling Mar 10 2005, 05:06 PM

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 (!)....

Posted by: Demick Mar 10 2005, 05:16 PM

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

Posted by: MecGen Mar 10 2005, 05:16 PM

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

Posted by: Demick Mar 10 2005, 05:18 PM

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

Posted by: bondo Mar 10 2005, 05:33 PM

Hmm, what if he didn't miss a decimal place but has the wrong pistons or rods? That would be quite a shim!

Posted by: Britain Smith Mar 10 2005, 06:06 PM

Well, my engine called for a 0.09 shim but I am running 7.4:1 compression. Can you say BOOST!

-Britain

Posted by: nebreitling Mar 10 2005, 06:23 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)

Posted by: lapuwali Mar 10 2005, 06:28 PM

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)

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.

Posted by: nebreitling Mar 10 2005, 06:39 PM

yup, all checked. it's the wrong pistons... i'll get this bitch put together some day....

Posted by: redshift Mar 10 2005, 07:05 PM

Nathan... I am sorry, buddy.

Never helpful, always empathetic..

M

Posted by: MecGen Mar 10 2005, 07:13 PM

Cool
Better now than later $$$
At least its gonna be rite

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

Posted by: nebreitling Mar 10 2005, 07:32 PM

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.

Posted by: Jake Raby Mar 10 2005, 09:07 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.

Posted by: Mueller Mar 10 2005, 09:09 PM

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

Posted by: MattR Mar 10 2005, 09:10 PM

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!

Posted by: nebreitling Mar 10 2005, 11:11 PM

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!

Posted by: Jake Raby Mar 10 2005, 11:12 PM

Mueller...
Your stuff is all done and shipping tomorrow...

Came out really sweet!

Posted by: Demick Mar 10 2005, 11:34 PM

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

Posted by: nebreitling Mar 10 2005, 11:58 PM

i agree! i assume he meant 002...

still, it doesn't take an enormous effort to spec these things out to the thousanth...

Posted by: MarkV Mar 11 2005, 04:44 PM

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.

Posted by: MarkV Mar 11 2005, 04:48 PM

I should expain that the one 59cc combustion chamber is different than the other three because it has been repaired & welded by the PO.

Posted by: MecGen Mar 11 2005, 04:58 PM

Ummm
My way is to always match head CCs first and formost.
Don't f**k with barrel spacers when you have a CC difference in the combustion chambers.
Check it out, its a can doityourselfer, but gotta read about it first, theres a rite and wrong ways.
Have fun
Cheers
Joe

Posted by: MarkV Mar 11 2005, 05:03 PM

When I took it apart the PO had installed head gaskets on the three 57cc cylinders. No head gasket on the 59cc cylinder. It didn't show any sign of leakage & the head gaskets are .030 thick.

Posted by: MecGen Mar 11 2005, 05:12 PM

I don't know....
I really wouldn't do it like that...
Cheers
Joe

Posted by: fiid Mar 11 2005, 05:13 PM

Basically - as long as your BBQ has brakes on the wheels, your deck can slope quite a bit. If your deck slopes a lot though - you might find that your drunk guests fall over more easily.

Posted by: MarkV Mar 11 2005, 05:18 PM

QUOTE (JoeSpark @ Mar 11 2005, 03:12 PM)
I don't know....
I really wouldn't do it like that...
Cheers
Joe

Me either.

Posted by: bondo Mar 11 2005, 05:27 PM

I'd get that head repaired right, or replace it. Anyone that repairs a head without making sure the volume was unchanged shouldn't be welding heads Chances are they didn't do a very good job aside from that problem.