Milwaukee Midget

[Speed Limit 1000]

Some of us break a record amount of parts
G

Stainless resembles that remark

[wheelrdealer]

Chris:

I guess you can say the Midget is now "in the record book"! Well, the picture of the Midget representing the class is. To be followed this summer is that one little line of text that makes you immortal to all in the LSR Community.

BR

[Milwaukee Midget]

I had been tipped off to that a while back. 

Just received my book yesterday.  Seems the powers that be chose the Midget as the representative picture for the GT class, and I'm very grateful Goggs bullyragged me into painting it a few years back!

As to immortality, I also have a copy of the 1993 rule book.  In the GT class, every single record has been bumped - EXCEPT Mr. Thomas' I/GT record, set in 1992.

That record has become seemingly immortal.

I know Tom is looking at punching up the SAAB Sonnet to run in I - he was knocking on the I record door with his J motor in 2013.  There have been hints of an Abarth return by friends of the forum, and rumors of a Honda entry.

So be it.  It may well take 4 individual efforts to change that number.

But change is coming. 

[Milwaukee Midget]

Dyno - prep.

One of the things I'm looking to accomplish is ringing every last ounce out of the Grenade this year. 

Last year, we experimented with manifolds, carburetion and headers.  We left ignition timing pretty much unchanged and ran with the Elgin recommendation as far as cam timing.

But this year, I've opted for a belt drive setup for the cam timing, which will let us change that up without having to remove half of the front of the engine to get at it.  No oily mess, and the whole procedure can be handled with Allens wrenches.

Rather than pull out the cam wheel every time we want to change cam timing, I took the time to scratch out 3 timing marks on the arbor and wheel of the cam drive.  108 is what is recommended, 111 and 105 are marked - we probably wouldn't want to go any further, due to potential valve issues.



And that was a wacky deal.  Most A-series cams run between 100 and 106 degrees, Elgin's recommendation is 108, so the timing marks wound up being at the very end of the slotted adjustment.  Each adjustment slot gives you 18 degrees of variance at the crank - the equivalent of 1 tooth on a forty tooth cam drive.  Moving the gear one tooth on the belt simply bumped the problem to the other end of the slot.  I'm tearing my hair out, thinking I'll need to have longer slots cut in it, when I realized that the adjusting screws were set on 60 degree centerlines. I reset the arbor and wound up smack dab in the middle of the slots, with room to advance or retard the cam.

Wednesday, I'll check valve to piston clearance.

Shooting for May 21st for dyno day.

Should we ask Slim if he'd like to see another Dynothon?  I've got a crank scraper on the way, new exhaust valves, a different header, an electric water pump drive.  We made 95.1 last year - I'm thinking 100 might actually be doable this time.

Chris

[grumm441]

Yep 108° is where I would go
G

[fordboy628]

Dyno - prep.

One of the things I'm looking to accomplish is ringing every last ounce out of the Grenade this year.  

And that was a wacky deal.  Most A-series cams run between 100 and 106 degrees, Elgin's recommendation is 108, so the timing marks wound up being at the very end of the slotted adjustment.  Each adjustment slot gives you 18 degrees of variance at the crank - the equivalent of 1 tooth on a forty tooth cam drive.  Moving the gear one tooth on the belt simply bumped the problem to the other end of the slot.  I'm tearing my hair out, thinking I'll need to have longer slots cut in it, when I realized that the adjusting screws were set on 60 degree centerlines. I reset the arbor and wound up smack dab in the middle of the slots, with room to advance or retard the cam.

Wednesday, I'll check valve to piston clearance.

Shooting for May 21st for dyno day.

Should we ask Slim if he'd like to see another Dynothon?  I've got a crank scraper on the way, new exhaust valves, a different header, an electric water pump drive.  We made 95.1 last year - I'm thinking 100 might actually be doable this time.

Chris

Yep 108° is where I would go
G

midget,

Elgin wanted you to run a cam with tighter LCA, something in the 102/104 degree range.   Problem was, that a conventional cam grind like that simply will not fit in a 999cc BMC short stroke race engine.     Vizard recommended 111/113 LCA, which would have given more valve to piston clearance, but nobody wanted to grind a cam with that wide an LCA, including APT.    Too "unconventional" . . . . . .       (Like a BMC for I/GT was a "conventional" idea . . . . . .   )

Last year during "Dynothon", most of the time was spent making sure:

A/   Various bits were working or modified properly, (ie: the valve-train . . . . ),
2/   The "inherent" self-destruction tendencies of BMC's was under control,
d/   Substituting parts to get the bhp curve up into the minimum range needed for competitive speeds in I/GT.

There is no question that 2013 was your best year to date . . . . .  that wasn't luck, it was the result of a LOT of hard work, testing & preparation.

2 things are going to determine where the cam timing and valve lash end up:

1/    Workable valve to piston clearance.   You (we) were already pushing the limit . . . . .
2/    Shape of the torque & bhp curves.   I want to see the torque curve pushed up and to the right on the output graphs.   It is unlikely that the torque will go up more than a
       ft/lb or two, because the specification (and CR) is "about" the same.    Later intake valve closing, (retarding the cam from where it was @ 105.? degrees) and the bigger
       exhaust header are two things that will accomplish this goal.

These things will also "probably" narrow the rpm band between peak torque and peak bhp, limiting the useful rpm range and "possibly" making the beast more difficult to drive.    We will see.    The biggest tuning issue here is that the "Grenade" has not responded to tuning changes in the ways usually predicted by BMC "Experts" for 970S variants.    The results obtained have followed the path typically seen from "big valve/big bore/big displacement" engines.

But it is also time to go for broke . . . . .    and to that end, I've heard a rumor you will be importing a "professional axe man".    I'm unsure how he will react to all the "room" in the "Milwaukee Midget" . . . . . . .     or the abundance of beer . . . . . .    

BTW, the best thing about "Krover", NO HARLAN SHARP ROCKERS NEEDED!!  
 
4valveboy

[Geo]

4valveboy - my kind of expert!   

Looking forward to both the Grenade this year and the K-dog next. Can hardly wait and to keep out of trouble in my excitement I am hunting for approprate craft beers to enjoy along with the continuing tale.

What will happen as Fordboy moves into the bi-world?  Two cams, two intakes, two exhausts... I doubt it will be too much. 

Geo

[Milwaukee Midget]

What will happen as Fordboy moves into the bi-world?  Two cams, two intakes, two exhausts... I doubt it will be too much. 

Geo

Given the Jag head, the Lotus heads and the Cosworth parts he has lying around in his garage, I expect this project may well be moving right into his wheelhouse.

Geo, how's that hardtop?

[Seldom Seen Slim]

Dynothon

So, girls and boys -- do you like the idea of another Dynothon?  I'll be happy to do it again. 

Here's what we'll do:

First, let Chris set the target hp for the engine's max output.  Once he's put forth a number we'll start taking guesses and donations.  I'll look back to get the previous dynothon's numbers and such and set up the ones for this event.

I see Chris has a tentative date for Dyno Day - 21 May - so that means we've got about a month to do all of this.

Over to you, Chris.  Thanks for bringing the idea back to the forefront.

[Geo]

Geo, how's that hardtop?

Well, since no one wants to package and ship one they are occasionally up as "Local Pick up Only". Well your neck of the woods is local to me.    It's 17 hours and 1050 miles all in one trip. Very nice factory piece.

Given the Jag head... he has lying around in his garage,

I like Mark even more! I have Jag parts too if anything is needed.

Geo

[Milwaukee Midget]

I have Jag parts too if anything is needed.

Geo

My observation is this - If you have ANY British sports car, you also have parts. 

The big problem is keeping them screwed to the car.   

[jacksoni]

4Valveboy:

"1/    Workable valve to piston clearance.   You (we) were already pushing the limit . . . . .
2/    Shape of the torque & bhp curves.   I want to see the torque curve pushed up and to the right on the output graphs.   It is unlikely that the torque will go up more than a
       ft/lb or two, because the specification (and CR) is "about" the same.    Later intake valve closing, (retarding the cam from where it was @ 105.? degrees) and the bigger
       exhaust header are two things that will accomplish this goal."

Recognizing your (preferred) CR limitations and the balance of what is going in and when it stops going in (Air+fuel) wouldn't you want to close the intake as early as possible when "it" stops going in to maximize your dynamic CR? You are suggesting retarding the cam rather than advancing it. I have seen suggested that advancing tends to help low end and retarding, relatively speaking, helps the top end as you are suggesting above but all this is dependent on basically when intake flow to the cylinder stops-then slam the valve shut. The difficulty being, of course, determining when that happens. The circumstance where port pressure sensors would help figure more easily than dyno time and many cams plus intake/exhaust changes.

[jacksoni]

or do I have it "bass-ackwards" and yah, "it's complicated" 

[Milwaukee Midget]

Jack, I've been studying David Vizard's book on the A series for years.  His opinion is that it's possible to pick up a pony or two on the top end by retarding the cam, and this almost always comes at the expense of low end.

In the case of the Grenade, there is no low end, so we might as well go for the top end.

Mark more succinctly notes that we would be "rocking the curve" on the torque, in an attempt to move peak torque up a few hundred RPM, which should translate to more power when it's multiplied by the engine speed.

But one of the complications that I have built into this thing is, once again, the unusually large rod to stroke ratio - it's 2.45:1.

On a normal 1275, it's about 1.8:1.

And this is, INDEED, where it gets complicated.

Part of dialing in a cam is getting the valve closing points right.  It's generally done as a function of degrees of rotation, but realistically, the effect on dynamic compression ratio is a function of the volume of air being compressed, which is a function of piston travel in a sealed cylinder.

The valve events and crank degrees remain constant, but the longer R/S ratio changes the distance the piston has traveled from TDC to the point of occurrence in a non-liner fashion.

At any given point on the stroke, the cam position with respect to the overall relative travel of the piston between the two ratios do not correspond anywhere on the arc except at TDC, BDC, and 90 degrees ATDC and BTDC. 

In short, in a "normal" R/S ratio engine, the events, measured by degrees in rotation, do not produce the same linear result of piston travel in the bore as they would in a longer R/S ratio.

So yes, it IS complicated!

Clear as mud, too.


But the point I'm making is that a change in timing events may not have as big an impact on torque and power production with this combination as it might with an engine with a more traditional R/S ratio.

[Harold Bettes]

Gentlemen of the Midget Motor,

You might well heed what Dema has suggested as there are a few rules of bruised thumbs to consider.
A) Tighter lobe center separation is a good band-aid for not enough cylinder head flow configuration
B) The tighter LSA will yield more lattitude for moving the cam toward the retarded mode as it gives more valve to piston as the piston chases the exhaust valve closing event.
C) A bit of consideration on the exhaust side via some different pipe lengths and diameters as the camshaft chosen might provide a bit different requirements.

As you know, dyno tuning will either support or refute this drivel. So best of luck with whatever you go to the dynamometer with.  

Regards to All that like this kind of stuff,
HB2