alien object - your guess is maybe better than mine!

[SJ Lambert]

Always happy to provide motivation for unpacking!!!!


Is using a piece of 5 mil thick perspex with a "liquid in" and "air out" hole as a "fill to" plate a good idea??

[rgh0]

Sorry forgot to pick it up yesterday - I will do in the next couple of days.

I used to use a glass plate sealed with grease and with a hole that I positioned at the high point for fill and air removal but found getting the air bubbles out was difficult as they never wanted to go where the hole was unless the head was on a bit of an angle and then I had leakage problems around the plate. I now just support the block or cylinder head upside down and horizontal and then fill till the liquid just reaches the rim, no need for the plate I find.

cheers
Rohan

[rgh0]

James
A picture of the pipette I use. it is 25ml with 0.1 ml graduations. The red rubber sucker enables you to pull up fluid in a controlled way and let it out again in a controlled way by squeezing the valves

Got it from "Crown Scientific" 1300 727 696

[SJ Lambert]

Thanks Rohan, it looks pretty good, about as user friendly as it gets, will chase one up tomorrow.

[SJ Lambert]

Got one from Blackwoods today. Gave up on Crown Scientific in the end.

Will have a go with some kerosene soon.

[SJ Lambert]

Here goes nothing!

I may have gone with too much grease between the rings.

[SJ Lambert]

Bad 10 mm high intruder!!!

Rough sums suggest compression ratio is too high, better too high than too low!

I guess I should shave 'em to something that's closer to being in the ballpark & re test!

[oldchieft]

Interesting progress, I like the photo record.

I will be going the same route next winter with the Accralite x/flow block replacement pistons that Burton sell.

They are 83.5mn with the 4mm/6.6cc intruder and 44.75 compression hight.

The stated compression is 11.6, but like you I am likely to be in the 20's due to the longer stroke crank.

What crank are you running?

Regarding the machining of the crown I asked for guidance from Omega/Accralite, and got this reply.


Quote
Good morning Jonathan,

The intruder can be completely removed if required, still leaving enough
crown thickness and thus maintaining the integrity of the piston.

The crown thickness of this piston including the intruder is 13.25mm,
the intruder is 4mm. So by removing the intruder, the thickness will be
9.25mm. We recommend thicknesses as small as 5mm, and this has not
proved to be detrimental in any way.
Un-Quote.


I did think that it might be possible to take metal from the cutouts first to the point were you could have a engine that would be proof against valve to piston contact even at full lift and piston TDC.

Has anyone done this in the past?

Jon the Chief

[SJ Lambert]

Crank's a narrow pin steel one with standard throw.

I wonder whether trimming the intruder height to the maximum amount possible to still maintain one's desired compression ration would maintain fuel/air mix efficiency & flow?

[rgh0]

I did think that it might be possible to take metal from the cutouts first to the point were you could have a engine that would be proof against valve to piston contact even at full lift and piston TDC.

Has anyone done this in the past?

Jon the Chief

Hi Jon
I don't know anyone who has tried it

You would have to make the cut- outs about 10 mm deeper and as they go into the crown of a standard piston a couple of mm already you will probably end up with holes in the top of the piston unless you got special pistons with a thick enough top. You will also end up with a pretty poor combustion chamber shape with 2 big holes holding the mixture affecting the burn time and pressure rise. You also will end up with a pretty low compression ratio even with the biggest possible intruder to compensate. All told probably not worth the effect to get a non interference engine

cheers
Rohan

[el-saturn]

just to add my personal answer with two pictures (this is a street engine though) - we (I) wanted the
111 or 1:11 using aan ajusa gasket. more to follow - the onlypart not on the engine yet is the oilpump.
next week i outta be back on the road - x-massy easter greetings sandy 36/4982 (now with my
old 701block!!)

[SJ Lambert]

Just doing my sums now. Am I correct in calculating that a gasket compressed to 1mm will give just over 5cc per cylinder?

What volume figure should be use for top ring to "compression height" / piston top?

[SJ Lambert]

With approximate figures as follows:

Combustion chamber volume 40.5cc

Intruder displacement 15.19cc

Gasket volume. 5.2cc

Cylinder Swept Volume 379.5cc

I get a compression ratio of 13.44 : 1

So, not as far off as I thought at first blush, unless I've blown it with my figures!

[SJ Lambert]

I suppose taking 1mm off the intruders at a time and re-testing would be prudent?

[rgh0]

Yes much easier to take off a little more than add any back!!! what compression ratio are you aiming for?

cheers
Rohan