Recommendations, boring, ballancing

[Mekanix]

Use an O-ring with a slightly larger ID than the OD of your oil passage. Use an O-ring slightly thicker then the gasket that it is going in. Enlarge the hole in the gasket for the oil passage the fit the O-ring. Install gasket and O-ring. The O-ring must not block the oil passage.

Sounds good. I just need 4 high temp O-rings. ID 13mm, OD >1.5mm(shim)
Shim oil passage diameter should be >16mm (13mm+ 2x1.5mm)

ID 13 OD 17

[GregT]

Normal Viton O rings will be OK

[Mekanix]

Thanks, I'll get some.


I've been trying to do the math to find out what I need to do to achieve a 12.5:1 compression ratio but its getting the best of me lately.

here's what I know

bore 78mm
stroke 56.6mm
base shim 0.5 up to 3mm
with no base shim or gasket the piston should be 0.8mm above deck
Combustion chamber per cylinder is 15cc's measured
Head gasket ~1.5mm

Intended compression ratio 12.5:1



Originally

bore 67mm
stroke 56.6mm
head gasket 1.5mm
base gasket 0.5mm
with base gasket the piston is 0.3mm below deck
compression ratio is 10.5:1

[GregT]

Do it the accurate old fashioned way...trial assembly and a burette.
Just put a wipe of grease around the edge of the piston at TDC then you can use water as your measuring fluid.
CR is then cylinder swept volume plus measured volume at TDC divided by measured volume at TDC.
Any adjustments needed are easy as the volume calculations are just pieces of a parallel cylinder.
I'd mock it up with the base gasket which gives you around .040inch piston to head clearance.
Been through this many times but it doesn't get easier or quicker....

[Mekanix]

Sounds good GregT that's what I'll do.


I've been wondering what to do in order to fit the cylinder block onto the base.

The sleeves are slightly too wide to drop into the case.


Should I leave the engine in the frame and file down the sleeves ?

That might be a problem if I want to bore larger later on.
It might have an effect on dissipating heat or affect the strength of the bore in those places.

How much room should there be between the sleeve and the case ?


I think taking the case apart and filing the case to match the sleeve is the best scenario.

I don't feel right filing anything on the base while its intact either. I don't think its worth being lazy on. ( and I've thought, I could just tape everything off and be careful and vacume as I go...)


I acknowledge that this is a one-of modification but the base is still stock and I will still have all the stock parts in the end.

Should I be concerned with keeping a stock unmodified base and simply keep modifying the block I have been modifying ?

[Nessism]

Then the GS1100 guys go way overbore like you are they bore the cases to accept the larger sleeves.

[GregT]

Then the GS1100 guys go way overbore like you are they bore the cases to accept the larger sleeves.

Correct - this is the correct way to do it but if you've got nothing else, filing will work with patience....I wouldn't reduce the sleeve diameter as it would be easy to create a stress raiser where it changes.
You're looking for some clearance - .006 - .010 inch area but it's not critical. The sleeves don't locate the barrel - the dowels do.
As it's a plain bearing motor cleanliness is paramount after enlarging the case bores.....

[Mekanix]

As it's a plain bearing motor cleanliness is paramount after enlarging the case bores.....

I hear ya, the last time I had it apart was to powder-coat it. That took a long time to get perfectly clean!

I wash several times, clean and rinse, run air and cleaning brushes through everything,

As a side note: A co-worker said to me one day, why not just put it in the dishwasher?
I never thought of it the whole time I rebuilt it the first time


Anyways its settled, I'll pull the base apart and file just the case top to accept the block the way it is.

I'm looking at 0.040" in the front and back on both sides and half of that for the left to right on each side but there is lots of meat there.

[Graham]

A pen grinder could save some time over a file on the case bores.

Something to help with your compression ratio. It's VW but it works the same.

http://www.msgulfcoastvwclub.org/TechPages/Tech10.html

http://www.vdubn.com/sandrailing/engine/deck_height.htm

[rustybronco]

Can you find a metal hole saw in the proper diameter? you could chuck it up in a drill press and center the case half under it.

[Mekanix]

Sorry its been a while since I've had the chance to get back to this project.

I'm involved in Oval track racing in the thunder devision and they call me "The Doc" for these cars :P (88-91 civics).

http://www.scotiaspeedworld.ca/weeklyracing.html

Its been taking up all of my free time.

But when I had the chance I've been making base shims and cutting out paper gaskets.

I've finally found the right piece of aluminum I want to make the head gasket out of and its just a mater of getting time to cut it out with a friends scroll saw.

Something to help with your compression ratio. It's VW but it works the same.
http://www.msgulfcoastvwclub.org/TechPages/Tech10.html

Graham I was looking at that site again and it finally made more sense.

I took the stock measurements

67 bore
56.6 stroke
deck height .5 (piston is .5mm below top of deck with stock base gasket.
combustion chamber 19cc's ( this is the head and the head gasket that makes the combustion chamber)
comp ratio 10.5


new using calculator

78mm bore
56.6 stroke
combustion chamber 21cc's
comp ratio 12.5
deck height 0.5mm

[pete]

Still busy racing or have you had a chance to do some more? Curious to see how this turns out...

[Mekanix]

I'm done with the racing thing for a while Pete. Now its just a matter of getting motivated to get out in the cold and strip the bike down.

I spent 4 hours tonight taking the engine out of the frame and getting it ready for disassembly.

To do:
1 split the case
2 remove the studs
3 enlarge the case to fit the cylinders.
4 reassemble
5 shim for cp ratio
6 check piston to valve clearance and adjust valve relief
7 order proper base gasket
8 slot cam sprocket's slightly
9 determine best cam timing.
10 assemble engine
11 install, start, cross fingers


I have a scrap case that I tried to mill by hand to fit the cylinder block but I think its better to just take the case to a machine shop and have it bored precisely to match the cylinders. $30 why not, no guess work.


I'll use washers for the base shim until I get the proper height and then either make one or order one that would be the right thickness.




I'm going to try and add pictures as things progress, but I get carried away sometimes and do 10 steps and then take one picture

[pete]

Sounds like you got it all planned out! Nice

For $30 I'd get it done professionally too...

Pic's are always good, but I understand on the 10 steps/1 pic thing

[platinum2]

hey i have some pop up pistons that will make it scream if your going 67mm 4valve piston buy the kit wayy cheaper than wiseco, then sell the other 2 ,would make a crazy fast bobber or cafe ect...