Milwaukee Midget

[Milwaukee Midget]

BTW- How are you going to get out of the car once you stuff yourself in that thing? An ejection air bag?

I thought about retrofitting the Aston Martin MI6 option package, but it interferes with the Hans device.   

I'm still in good enough shape to make it work, although I know I have a good solid afternoon of practice in front of me for bail-out procedure.  It's comfy enough for a few trips down the salt.  15 laps at Road America would probably cripple me.

Good hearing from you, Harold.  Read your Dyno book cover-to-cover - a must read for the serious.

http://books.google.com/books/about/Dyno_Testing_and_Tuning.html?id=orzY7AeaDQsC

[fordboy628]

The head came back today after a .060 haircut.  The head skim was a bit harrowing.  When you slice cheese this thin, you sometimes discover Swiss cheese –



It’s just the water jacket on the face, which both Mel and Fordboy agree should not be an issue.  A dab of HT silicone against the face and against the gasket should keep it from leaking, but this is an indication of just how extreme this combination is being stretched.  Part of the issue is the lack of cylinder capacity with respect to chamber capacity.  In order to get a CR that will produce power, the chamber needs to be as small as possible, so pushing things to the limit – and in this case, a tad beyond - is what needed to be done.

I’ll be scrubbing up the castings this evening, and next week, I’ll meet up with Fordboy, he'll cc the chambers and we’ll see what out final CR is going to clock in at.

Midget, et all,

Completely ignoring the risk to self brought about by a foray into the Land of Lincoln whilst driving a cheddar plated vehicle, Chris appeared on the doorstep of the ranch/dungeon with the 'Swiss cheese' (cylinder) head.  Got out the trusty burette for the cc'ing process to determine final static compression ratio.   Followers of Midget's diary may recall that the original static c/r was 10.48/1 when the #1 combustion chamber measured out @ 22.5 cc's.  Not quite enough for full race.  Some specification changes were proposed, with the goal being to achieve as close to 14/1 static c/r as possible, given the physical limitations of the bits.

Post machine shop haircut, the head measured out at:

#1   17.3 cc's
#2   17.2 cc's
#3   17.4 cc's
#4   17.3 cc's    for an average of 17.3 cc's per combustion chamber.

Anytime the tolerance is +/- .1 cc ALL of the machine work has been very well done.  The valve heights are very even, denoting attention to detail in the valve & seat work.  And the chamber heights are even as well, meaning that attention & precision were in evidence for the milling/skimming process as well.   Kudos to all whose hands massaged this head.  The calculation on skimming the head .060" was for a minimum 4.5 cc to 5.0 cc volume reduction.  A 5.2 cc reduction was achieved due to the chamber edges being angled outward to improve flow, which gives an irregular volume/shape ratio.

Combining the reduction in head cc's with the block milling (piston height going from -.004" to +.008", which will be confirmed on build-up) the resulting static compression ratio works out to be: 13.56/1, which given the resultant 'Swiss cheesyness' ( ) of the casting, is the limit of what can be achieved with this particular head casting.



Standby for the 'Frankenstein mods' to the cylinder block, in the next post.
 
FrankenFordboy

[Tman]

Looks good.

[scrapiron aka Park Olson]

When I was running SCCA H & G prod., 950/1100, you would expect to get into the oil passage to the rockers when milling,,grind it out, lay in a tube, braze it up,,,good to go,,,

[fordboy628]

When I was running SCCA H & G prod., 950/1100, you would expect to get into the oil passage to the rockers when milling,,grind it out, lay in a tube, braze it up,,,good to go,,,

Decades ago (?), when I was prepping 12G295 heads for the above, that was the accepted modification to raise the compression ratio.  Then somebody clever (?) came up with the "intruder" piston idea..............

 
Fordboy, formerly FrankenBMCboy   

[Milwaukee Midget]

When I was running SCCA H & G prod., 950/1100, you would expect to get into the oil passage to the rockers when milling,,grind it out, lay in a tube, braze it up,,,good to go,,,

You were likely running the earlier 12G295 or 12G206 castings, which would have put the oil passage much closer to the face - and that's a good fix for those.  This is a later 12G940 casting, and while I didn't get into the oil passage, I will need to line up the oiling hole a bit.  It's drilled at an angle toward the pillar, and we took enough off of the face to offset the alignment to the oil feed from the block.

Welcome to the forum, Scrapiron!

[fordboy628]

Midget, et all,

Early BMC head castings have the rocker shaft/cylinder head oil feed cross passage drilled horizontally and near to the cyl head gasket surface.  Any extreme milling of the head face to raise compression, broke into that passage, requiring a fix of some sort.  Most fixes work out OK, but the one I liked the least was the external oil feed pipe: a bent copper tube with single flaring & fittings @ both ends.  When the pipe cracks or is damaged, it creates an impressive oil leak.   If this leak occurs during the heat of battle, bye bye bottom end!

At the request of the works race team's engine builders, the factory engineers & designers moved the horizontal drilling for that oil feed passage up to the top of the cyl head on the later model heads.  Solving that one problem anyway.
 
FrankenFord/BMCboy

[grumm441]

so, i guess you saw this

http://www.nzherald.co.nz/motoring/news/article.cfm?c_id=9&objectid=10828009


G

[WOODY@DDLLC]

Those guys were having waaaaay too much fun! 
But they were using "hybrid" technology: Hyabusa cylinder head! 

[Milwaukee Midget]

Actually, Woody, that's a BMW head.  Graham and I have been watching this one bubble up for almost a year. 

Here's what kind of shocked me on that one.  I was looking at pictures, and it appears that they are using the stock oil pump, which means they had to have a jack shaft or something running from the front.  Rather convoluted, but it worked.
 
They're also claiming ~ 280 HP - perhaps - a 3 main BMC block at 9G under boost?  That sounds like a potential shrapnel pile, but damn, it stayed glued together!

Nevertheless, it does prove one aspect for me - an under square A block can set records.

It's ALL good news.  Congrats to the Kiwis!
    

 

[WOODY@DDLLC]

Chris, there were about 15~20 guys on the team. I was told 'Busa but did not see the head or the engine! The crank was in SLC getting reground - oiling issues! 

[Milwaukee Midget]

Fordboy, Graham,

Okay, putting the block back to rights.  I installed the center oil restrictor on the 2nd main with no difficulty, but the bypass spool has given me pause for thought.

It’s in, it’s bottomed against the machined ridge in the bore that leads to the pressure relief valve, but I don’t know if it’s supposed to be centered in the bore between the long gallery and the rear main.  It’s clearly not, and I’m not sure if this is the way it’s supposed to be, or if the block was improperly machined at the factory.

Using the bore scope and a .017 guitar string, looking up through the rear oil passage from the rear main bearing, note that the string cannot pass on the left side of the spindle –



Yet it passes through on the right side . . .



The ultimate question is, is there sufficient flow?

[38flattie]

Chris, can you do a little 'touch up', so that the passage flows better? I'm pretty sure more oil would be better than less!

You guys often times lose me with some of your tech jargon, but I still love this build!

[Milwaukee Midget]

Here’s the deal.  There are two oil passages that intersect in the A block – one is right off of the pump and goes to the pressure valve, and the other is from the gallery to the rear main bearing.  In this passage, BMC installed a spool, which looks like this –



It lets oil pass through one circuit by diverting the oil around the outside, while also permitting oil to pass through the center.  I don't think there is enough meat on it to turn it down - it needs to be press fitted, and it would likely collapse if it were thinner.

You can ask “Well, why didn’t they . . .” all day long, but in the end, this is what I’m working with.  I think of it as an elegant solution to a problem that should never have existed.

[Dr Goggles]

"I think of it as an elegant solution to a problem that should never have existed."

That, right there, is I think part of the Pommy car mentality that traps you guys, or at least causes you to fall in love...... the million bolts, the weird measurements, the abject refusal to copy better ideas...... It leaves us who mess with the utilitarian, the commonplace, at a loss and those (you)who'd never stoop to those depths grinning to themselves......

yeah, I know , I'm supposed to be writing other stuff, not watching this......11.40am and I haven't started proper yet.