Milwaukee Midget

[fordboy628]

Courtesy of a fellow member who is in contact with David Vizard -

Regarding my build -

"There are some compounded problems with this engine spec. Firstly the cams LCA is too tight at 104. It needs to be at about 110 to 111. Also the duration is such that it will exaggerate the cylinder robbing from outer cylinders to inner ones so duration needs to be cut by about 10-12 degrees. Third the CR is way too low at 11/1 for this combo. To make the top end for outright speed we need to have about 14/1. This will be much more doable if the LCA is spread and the duration reduced. Also read what I say about valve cutouts in the big yellow book. The best cutouts are also the easiest to do so don't scare yourself off doing this to achieve that. MUST HAVE CR!

DV"

I'm trying to find a cam with a Lobe Center Angle that wide that isn't intended for a Morris Minor Panel Van with an automatic.  Seems awfully wide - the Leyland street grinds are all at 107.5, their race stuff tightens up to 102.5.  Mine, being a scatter pattern, is 105.5 for pistons 1 and 4, and 102.5 for pistons 2 and 3.

I guess I need to find out if this is even an option, short of a custom grind.  I'll be out in the woods with my flashlight . . .

FB - when I get those numbers, I'll forward them to you for modeling.

Andy - good hearing from you again.  It's getting interesting over here.

Midget,

Like I've been saying all along: "It's complicated."   DV recognizes this, better than you & I, and his advice is right on. (Spot on? for Brits, etc.)   Anytime you put together a 'unique' build, you have to be prepared to have 'unique' parts, to tune the combination for what YOU need.  

Now before you lose your enthusiasm, thinking that you are lost without direction, stop for a moment and consider where you are.   You are not lost out on the ocean without a compass.   It's more like you are in the forest without a compass, but you have a few things that are tools to help you find your way out.    The first step is to figure out exactly where you are, and then determine the direction to proceed in.

That process will begin in earnest today, sorting the useable from the unuseable, AND, determining the direction(s) with the most potential.    Another favorite quote of mine is: "Think first."   I'll see you later today.   
 
And: DV is right on about C/R!   EVERY SMALL DISPLACEMENT BMC I EVER ENGINEERED RESPONDED FAVORABLY TO HIGHER C/R, EVEN AT THE EXPENSE OF CAM!   And I know just who to ring up for a trick cam, PLUS, I've got a core I'll donate.   My only condition:   "Think first, THEN the beer."

BTW, the majority of your build choices have been excellent.   Remember, NOBODY bats 1000.

Fordboy

[protype]

Based on the looks of the tops of the pistons there is some indication that there is some uneven distribution from the intake.  This can be cam, intake or header design, or a combination of more than one.  A picture of the head and combustion chamber burn pattern would also give some additional indications. 

[Milwaukee Midget]

Thanks for the vote of confidence.  You're right - and that seems to be a trend with you, FB. 

And yes - truth be told, I need to recall that I've had what I consider to be a degree of success at Maxton.  92 mph in third gear for a stock bodied Midget running 21% less capacity than a standard engine?  I don't know anybody else who has done that.

But yeah, a lot trees out here.

We'll see you this afternoon.

"Think first, THEN the beer."

We'll think quickly.

Based on the looks of the tops of the pistons there is some indication that there is some uneven distribution from the intake.  This can be cam, intake or header design, or a combination of more than one.  A picture of the head and combustion chamber burn pattern would also give some additional indications. 

Likely a combination, exaggerated by the scatter pattern cam.  To indicate how rich it was running, that was after two passes at Maxton and 3 dyno pulls.  It got gunked up pretty quickly, but it cleaned up with a paper towel and WD40. 

[Milwaukee Midget]

Just a quick post - Fordboy stopped by this afternoon.  He did some serious number crunching and will be modeling a few ideas shortly.  We'll share that.

The consensus tonight is that to dyno next weekend would be folly.  Instead, it seems likely I'll be pulling the engine.

Long day - early day tomorrow. 

We're going to get this right.

Forboy -  - to you, my friend.

[Andy Cooke]

I'm sure that DV had an example 1000cc screamer build in the first edition of his A series book, mine dissapeared long ago, so maybe this is a false memory?

By spreading the lobe centre and redusing the duration he suggesting keeping the exhaust opening, and inlet closing flanks roughly where you have them now, but taking out a lot of overlap.  I've done much the same on my latest turbo cam, but I'm out at 118deg LCA  .  This wins you a lot of valve to piston clearance, so should make finding the extra CR easier.  I'm not sure how you work out how to time the various lobes on a scatter cam though.

I've not looked to see which profiles have the reduced duration, but there will be one.  It shouldn't be a problem to get the lobes ground at different centres, normally it's just a case of asking.

With the engine simulation work I've seen the results are a bit iffy when it comes to looking at overlap and reversion, it'll get you a long way there, but I've seen some big power losses from totally simulated engines (much like I've seen big aero losses from pure CFD designs).  We still run simulations, but it is just a tool.

Andy

[fordboy628]

Now that some serious measurement & number crunching has been done, it will take some time to determine what is the best path to resolve the issues.  This is going to require some research and some more evaluation, probably some flow testing, etc, etc.

Need to go though both of DV's BMC books for any useful info.   I, personally, am not interested in 'reinventing the wheel'.      DV has done all the heavy lifting on this already.

Engine simulations are just that: simulations.   Depending on the skill & experience level of the person choosing the input data, the results can be 'golden' or 'gigo'.  (garbage in/garbage out)   My experience is that ACCURATE simulations, and measurements, can be helpful in choosing combinations, as opposed to cutting & trying dozens/hundreds of permutations.   AND, I have been able to reduce development time and cost by pursuing the combination with the best 'potential'.   I know that sounds non-specific & a bit hazy, that's just the stage it's at right now.    But, as Andy correctly points out, simulations, modeling and data crunching are just more tools.   In the finish, hp needs to be verified on the dyno.............

Lots of trees in the forest get chopped down by big Vikings with axes.   I am willing to use a chainsaw if I have it.

If anybody out there knows of a engine shop in the Chicago/Milwaukee/Madison/Rockford vicinity with a computerized brake and BMC adaptors, please let Midget know about it.

Fordboy

[Milwaukee Midget]

Informative day, yesterday.   Fordboy made his way across “the Cheddar Curtain” into the land of milk and honeyweiss, and spent about 6 hours taking measurements, gathering facts, asking questions, and chuckling at the SCTA rulebook.  A true fact finding mission, and I’m grateful for the help. 

What has become clear is that my hope of not having to pull the engine has evaporated, and for reasons above and beyond just getting the compression ratio up.

1 - We’re going to adapt a Saab throw out bearing assembly to replace the stock external slave, which will -
   A – Make bleeding the clutch much easier, and . . .
   B – Make enough room in the chassis to build an actual blow shield.
2 – While the block is out, I’ll retap the oil system for a larger diameter oil line.
3 – I’ll cut a slot in the bell housing and set up the flywheel with a degree indicator to consistently find TDC – which has been an on-going problem with the marks underneath the engine that were shrouded by the front frame crossmember.
4 – Notch the front crossmember to accept a longer pulley system which may include a Gilmer drive setup, and hopefully provide sufficient room to put a degree wheel on the front of the engine to change cam timing without having to pull the engine every single time.  This modification also makes taking the engine out a lot easier.

Yesterday was a game changer, and in a very good way.  It has provided for me a focus and a clear cut path toward finishing the car up, and and while we're not sure at this point what we'll be doing precisely with the engine, it's still early enough in the season that this shouldn’t result in a “thrash” in August. 

And with the engine out of the car, I’ll be able to finish some chassis details that I’ve let slide.  Make hay while the sun shines.

The grand experiment continues . . .

[fordboy628]

Midget,

Whilst rooting through the giant dustbin that is my parts stash, I have found what appears to be a Saab to Midget trans t/o brg mount/adaptor.   If memory serves me correctly, there are 2 BMC transmissions (rib case/smooth case) with minor t/o brg differences.   You'll need to take some measurements or I'll need to make another 'pilgramage'.   Also need to know clutch release finger ht., from block face to where t/o brg. contacts fingers.

Have sawsall for chassis mods (or brain surgery) if you need one.   Awaiting arrival of "yellow pages".   Will correct data input for sims sometime this weekend.   PM me about your Iowa request from Binnie's, soon to sortie there.   Ta ta for now.

F/B

[Milwaukee Midget]

Rib case - I have one I field stripped in the basement.

Also need to know clutch release finger ht., from block face to where t/o brg. contacts fingers.

Looks Like I'm pulling that engine sooner than I thought . . . 

Didn't really want to mow the lawn, anyway . . .

 

[charlie101]

I've been searching like mad for the input I based my reply on, but starting to suspect I remembered wrong name alias on that forum, sorry. However hydrolastic do race BMC's but isn't the man I was thinking of. I'll get back when I find it.

Yep, got it all wrong. The guy from Raleigh, NC races Fiats on a very high tech level and has got a lot of resources. His webpage may be fun to look through. Might be of some value.

http://www.scuderiatopolino.com/index.php

[Milwaukee Midget]

Charlie - Thanks for that info - and yes, a cool site.

Seems North Carolina is a hotbed of Fiat and Abarth activity - the car I'm gunning for in I/GT was also out of North Carolina - an Abarth.  The record is 20 years old, and it's stiff for a 1 litre production bodied car.

I have a picture of it on my dart board. 

[Stainless1]

... I/GT was also out of North Carolina - an Abarth.  The record is 20 years old, and it's stiff for a 1 litre production bodied car.

I have a picture of it on my dart board. 

Thank God it isn't this one.... the previous Abarth record holder at 120.872.....
Been thinking about taking it out of mothballs

[Milwaukee Midget]

Stainless, I/GT has been slow these last few years - very few entrants.  Dust it off, bring it out. 

Fordboy, here’s a pic of the inside of the bell housing of my spare ribcage transmission.  While I haven’t pulled the engine and tranny from the car yet, the depth from the engine plate to the stud flats of the front transmission cover is 6”.



Until I pull the transmission, I won't know the depth to the fingers, but I can get you some measurements of bolt centers.  Moss lists the same gasket for the front covers of both transmissions, but the covers are different.

[38flattie]

Minor setback Chris- afterall, getting this far has been a journay!

Keep chugging away!

[Milwaukee Midget]

Setback? Nahhh. Course adjustment would be the term I'd use.

Had I pushed forward, I would have gone into the dyno, done a few decent pulls, and likely have straightened out the problems I had last time. It would have made a killer sound, probably would have thrown up some respectable numbers - but would they have been sufficient?

After my visit with Fordboy last week, and the correspondence with Vizard, the shortcomings of the combination are in sharp relief. In the back of my mind, they were always there, but for lack of better information - Andy Cooke's early critique an exception - I was intent to press forward.

But earlier in this build, I stated that the only possibility of being successful would be to wring every last ounce of power out of this combination. To do that, I have to hold myself to that goal. And I really don’t think I’m so far off the path that it can't be corrected.

By the way – KILLER NUMBERS ON THE FLATCAD!