Milwaukee Midget

[Milwaukee Midget]

And jdincau, too. 

I'd like to thank the acadamy . . . 

[38flattie]

Chris, when I was younger, I took a block in to get decked. When I was asked if I would have a clearance problem, I told him no. Well, I did! I had to use a gasket almost twice what I had (don't remember the thickness), and I didn't have any issues.

If you're ok with the new compression numbers, I'd pose that question to the gasket maker.

Good luck!

[Anvil*]

Everything I've read tells me .080 clearance on the intakes, .100 on the exhaust.  The valves are completely vertical to the pistons, the rods are steel, and the valve train is very stable. 
Chris

Well, I only know three ways to get a fairly exact answer. Calculations with the cam profile, component inertias, and such, using a Spintron, or running the combination.

APT has dyno run data, they might have recorded clearances. You should try to have your valve, cam follower, and spring retainer weights and your spring, rocker, and pushrod data handy. The card says if you have questions call, so I'd start here.

Sadly, I don't have a current Email for Mr Vizard or know of a blog where he checks in from time to time. His shop is in Charlotte, NC these days. He does tend to answer questions, so I think that's why he keeps his profile much lower these days (wouldn't get anything done otherwise).

Oh, one potential hiccup, the Cooper S has shorter valve stems (lighter valves) so you would need a shade more clearance than a Cooper S with the same cam lobe to play safe (unless you swapped to lighter valves).

The one good thing is you have time to apply a little discipline, to pace your shifts and roll the throttle on a bit before going to full throttle. You shouldn't find yourself out of gear with you foot mashed down. 

[Milwaukee Midget]

One more time on a recheck - this time doing it by the book as per jdincau's suggestion. 

I'm spot on with number one, and PJ, I will check the other three.  To your point, yes the events are different between the center cylinders and the outside, but all it takes is an accidental bump of the cam grinder, and I'm sifting shrapnel from my sump, and I don't want to do that - EVER.

Just got off the phone with David Anton at APT - and just a quick comment here - if you're building a Mini or a Midget motor, they're willingness to help after the sale is first rate.  They also do Triumph and MGB parts.  aptfast.com

Not cheap, but they know their stuff.

He agrees that .080 is where you want to be on the intake, .100 on the exhaust, and I might be able to squeak by with it as tight as .065 - but again, my aversion to shrapnel sifting has already been stated.

His first recommendation is to cut a slot in the piston - not a circle, a slot, full width - but that I could get by with a thicker gasket.

I've already got a custom Cometic MLS gasket - .029 - (Yeah, Buddy - I've got spare gaskets, too! ) they were able to whip it up in less than a week, and can make one any reasonable thickness I would need. 

The last tune and test night at Great Lakes Dragaway is mid October.  While I don't want to rush this, I would like the opportunity to get a test session in and prove the combination before I do something that might not be reversable.

I guess I'm leaning toward the gasket.

Back to the build room.

[Andy Cooke]

That's a lot of cam for a small engine, I ran a megadyne 310 in a 1293; below 4K it ran like 3 leads were unplugged and came on like a switch.  It revved plenty, but I'm pretty sure a milder cam would have made more power.  You might find you make more power with standard ratio rockers?  Anyway, good luck with it all, I'm looking forward to seeing the results
Andy

[Milwaukee Midget]

That's a lot of cam for a small engine, I ran a megadyne 310 in a 1293; below 4K it ran like 3 leads were unplugged and came on like a switch.  It revved plenty, but I'm pretty sure a milder cam would have made more power.  You might find you make more power with standard ratio rockers?  Anyway, good luck with it all, I'm looking forward to seeing the results
Andy

We share common doubts, and it's a thoughtful critique.  I questioned it, too, and it wasn't my first choice - the SPVP3-BK was.  My nature is to go conservative, and for precisely the reasons you stated - crummy idle, peaky output.  And I'm the first to admit that I'm in uncharted territory.  While the factory supported the 970 in the Mini for a couple of years, and produced a few Formula Junior engines to approximately this spec, they built less than 1000 970's, and there is virtually zero information on setting them up compared to the long stroke A-blocks. 

But Dave Anton at APT has built a few 970's, and after spelling out the objectives, the consensus was the SPVP5-BK was the best bet.

Here are the driving forces in my decision making -

The goal is 123 on the salt.  I'm running 23" tires and 4.22 gears - hardly a traditional LSR setup, but that puts me wanting peak power at ~7500 and 8000 RPM.

The valve sizes are virtually ideal for this combination, and I didn't have to offset the exhaust valves to do it.

I'll be running standard ratios in the transmission, so to fall back on the power band, I'll need to be able to rev past peak in 3rd.  The billet crank, Saenz rods and J&E pistons should be up to the task - this cam should go there.

If I were doing ANY OTHER type of racing, this combination wouldn't receive a second thought.  Part of the trouble I've had sussing out information is that when people talk Sprites/Midgets/Minis, they're almost always talking road racing, hill climbing or rally - poked and stroked up to 1500 cc's - and with good reason - that's where the racing history and engineering of this engine has been grounded for better than 50 years. 

With this application, my only concern is that the power band needs to occur on the east end of the tach, and that it can live there for a few minutes.

The die is cast, and I'll keep you posted!

Cheers, Mate!   

[Dr Goggles]

If I were doing ANY OTHER type of racing, this combination wouldn't receive a second thought.  Part of the trouble I've had sussing out information is that when people talk Sprites/Midgets/Minis, they're almost always talking road racing, hill climbing or rally - poked and stroked up to 1500 cc's - and with good reason - that's where the racing history and engineering of this engine has been grounded for better than 50 years.
Cheers, Mate!   

  , ,


Yep, you could have built one of those motors, and we would have thought less of you. You're building a landspeed motor, and that will put you out of reach of anyone who takes their midget out there to "just see what it'll do".

Cut your own path.

[4-barrel Mike]

Just caught a reference on turboford.com to the David Vizard video series on turboford.com    Since the V4F Ford has siamesed ports, I went looking.

Pretty interesting man.  Here's his video on Mini cams: http://www.youtube.com/watch?v=8NXl6dJBWaM

Mike

[Milwaukee Midget]

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[Milwaukee Midget]

Last night, about 11:30, I couldn’t get to sleep, so I went ahead and cut some angle aluminum for radiator brackets for my auxiliary radiator.  This is a trick they use on Minis to keep the back of the head from overheating, although generally they simply bolt the old heater core to the firewall or wheel arch and call it a day.  It doesn’t have to dissipate a lot of heat, just knock it back a tad.  I already had a 4” hole behind the grill for the heater, and since I had my “mystery radiator” re plumbed, I figured, what the heck. 



The hole had a flange stamped to accommodate the old heater duct, and I needed to remove that.  I’m sure the neighbors just love the sound of an industrial sized dentist bit whirring away at 12:30 in the morning, but tit-for-tat, baby – turn down your stereo on school nights . . .



Ugly, but effective.  Or as my paining buddy, Joe Phillips puts it - "A blind man on a fast horse will never know the difference".

If it isn’t one thing, it’s another.  In my attempt to button up the bottom end and shim the crank sprocket, I found the darned thing hanging out on the snout too far to even get close to an aligned timing chain.  Seems Greg put a very nice 1/8” radius on the snout, too.  No complaint there, but now the sprocket is sitting at the machine shop waiting for a somewhat more generous chamfer.  I’m constantly being reminded that  I’m not playing with Legos. 



I had C&S do a touch-up valve job.  After a bit of juggling, they’re now indexed, and I probably picked up an extra thousandth on the previous clearance issue.

[Rex Schimmer]

Thanks 4-Barrel Mike,
If you happen to have time go on the link that Mike provided and watch all of the Dave Vizard videos on the Mini engine. So much of what he is talking about applies to all engines. I have always liked Vizard's writing but to listen to him and his level of knowledge and common sense is very enlightening.  Time well spent.

Rex

[Milwaukee Midget]

Thanks 4-Barrel Mike,
If you happen to have time go on the link that Mike provided and watch all of the Dave Vizard videos on the Mini engine. So much of what he is talking about applies to all engines. I have always liked Vizard's writing but to listen to him and his level of knowledge and common sense is very enlightening.  Time well spent.

Rex

Hey, Rex -

The video series which you mentioned, and Mike posted, is a presentation using David Vizard's book, "Tuning the A Series Engine" as a framework - a book I have all but torn the spine off of, lo these past few years.

I stumbled across that very video series about 6 months ago, and it helped clarify for me a number of the points he makes in the book.  And I've got to believe that quite a bit of what he's discovered is completely applicable to any number of vintage, shared-port engine configurations.

[grumm441]

The video series which you mentioned, and Mike posted, is a presentation using David Vizard's book, "Tuning the A Series Engine" as a framework - a book I have all but torn the spine off of, lo these past few years.

I had two well dressed young men at my door asking if I was familiar with the Bible and in particular the book of Mormon

I began to tell them about Tuning for Speed by A.Graham Bell. They left?
G

[Milwaukee Midget]

The video series which you mentioned, and Mike posted, is a presentation using David Vizard's book, "Tuning the A Series Engine" as a framework - a book I have all but torn the spine off of, lo these past few years.

I had two well dressed young men at my door asking if I was familiar with the Bible and in particular the book of Mormon

I began to tell them about Tuning for Speed by A.Graham Bell. They left?
G

Faith and truth have a head-on collision at Grummy's doorstep. 

To avoid accidents, I disconnected my doorbell.

[grumm441]

Around here , you see someone on your doorstep, you lock and load
G