Milwaukee Midget

[fordboy628]

Taking this all in over a pint of Ole Speckled Hen.

One quick thought - and this comes back to the old "it's all about compromises" quote.

You and I both know there have been very strong BMC engines that never had a scatter pattern cam, and dozens of very competitive grinds are available.  I've been poking through Dema's catalog and I'm seeing a couple of grinds that could be put on an appropriate LCA and look likely to work.

As you pointed out, the 3 degree spread is what APT and Kent have used on the 2&3 (or at least ADVERTISED as such).  Given the tight tolerances we're chasing, might it be to our advantage to adjust the center lobes 1 1/2 degrees to maintain a better bit of clearance and still take a lesser advantage of the lower cylinder robbing characteristics that the SP cam provides?

Yeah, I know, now we're talking the black art of cam design, but at this point, in for a dime, in for a dollar.

Midget,

Heck yes, in for a dime/dollar/pence/euro/whatever!!    Also, yes, to all of the above suggestions.   The build geometry for your little jewel REQUIRES design parameters "borrowed" from my, & now your, design principle, MAXIMUM CRAM.

1  MOST of the BMC's I've had a hand in did NOT use the scatter pattern, and as you pointed out, they ran very well.   So that's a viable
    option @ some LCA that will fit.
2  Reducing the scatter amount will probably reduce the effect, BUT, should retain some of the effectiveness.
3  Other cams grinds with differing flank rates (lobe lift @ "x" cam degree) on the LCA required, MAY, fit/work better, than the ones that
    you are considering.   You need the displacement values from the other cam grinder(s) to know for sure if other grind(s) could fit.
    You can plug the lift #'s into the formula from my previous post, (Reply #1238) to check if a different grind will fit.
4  As I have said from the beginning: MAXED OUT (whatever that means) racing engines are ALWAYS A COMPROMISE, somewhere in
    their specification.   There is always too much going on in too little space.   You don't have to believe me, but believe the 'Rolling
    Stones';   "Ya can't always get what ya want, but if you try sometimes, ya get what 'cha need."   (I know they aren't Hank Williams,
    but I'm a rocker, buddy.)   Your situation reflects this.   Off the shelf cam Vs. what you need.......   You have to tell the cam guy what
    you need, because how would he know the specifics of YOUR build?
5  Re: MAXED OUT.   I can always find additional ways to slice cheese thinner.   You can, and are, learning how.   Just know this: The
    thinner the cheese, the more expensive it is..........
6  Keep in mind that spreading the LCA over the optimum kills hp quickly.   Having the LCA tighter than optimum makes the engine
    come "on the cam" harder, AND, much less driveable at low rpm's.   And, of greater importance here, lower LCA = LESS VALVE TO
    PISTON CLEARANCE!

And finally, regarding the "black art of cam grinding".   This is what some cam mfg's want you to believe.   It is, of course, baloney.  Cam grinding is simply physics, engineering, metalurgy and dedicated, quality manufacturing.   More difficult than slappin' together a baloney sandwich, ('sammich', here in Chicaga) but there are a lot of excellent cam mfg's out there.   You need one who is willing to make you what you need, rather than having you try to fit something from "off the shelf".
 
Fordboy

[Moxnix]

Leroy start the audio @ Wilmingto this morning, but some glitch in the line, even with two sets of speakers.  Maybe I should take up cam grinding....

[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"

Midget,

After our BS (beer selection) session last evening, went back to review the "DV" advice, included above.

                          SPVP5 (original)                                     SPVP8 or similar (proposed)
Seat Duration:       306 degrees                                           288 degrees
.050" Duration:      264/264                                                 252/252
LCA:                     106I/99I/106E                                        110I/106I/110E  (or 110 all)
Lobe Lift:              .339"/.339"                                             .340"/.340"

These changes are right in line with what "DV" suggested.......
And using the formulas from the "Yellow Pages", gets you to pretty much the same numbers.   As you are checking cam specs, this is the area to concentrate on.

As far as C/R goes, the original ciphered out to 10.48/1.
Milling the head .060"/.065" @ an avg. of .0128"/cc would reduce the volume by: 4.7cc = ~13.2/1  OR  5.1cc = ~13.4/1

I believe this is about the limit of what can be achieved by machining the deck surface of the Longman "big chamber" cylinder head.   I also believe that welding (to reduce chamber volume) on the heavily ported Longman head, is probably a bad idea.

I'm confident that this new combo will be a giant step forward in engine performance.
 
Fordboy, er, Capt. Nemo..............

[Milwaukee Midget]

I've bounced back and forth to that "epistle from on high", myself. 

But I've also taken to heart your thought that a little extra lift/duration on the exhaust side, due to the ~70% proportion of flow is something we need to consider.

That lead me to the MD296 grind - and hey, haven't you mentioned that one before, Fordboy?

290 intake, 300 exhaust  .324 I lift,  .340 E lift.   

 . . . at this point in the post, I was interrupted by a delicious spinach and cheddar omelet by Mrs. Midget, followed by another hilarious conversation with the aforementioned Mr. Fordboy . . .

One last calculation I've asked for from FB is this - take the specs of a punched out 1275 that he's had success with and determine the percentage of distance the piston has travelled down the cylinder on the power stroke before the exhaust valve opens.  From there, I'd like to calculate the corresponding opening point in cam degrees factored into this build.

Information -

Stock 1275 throw  = 3.200

Stock rod length 5.75 = 1.797 R/S ratio
5.875 rod length =        1.836 R/S ratio
6.0 rod length    =        1.875 R/S ratio

My combination 

Throw  2.45   Rod length  6.0

R/S ratio      =   2.449

I'm hoping this might give us an optimum starting point to determine where the grind needs to start opening up on the exhaust valve.

Time to finish painting the interior on the Midget. 

It ain’t all about engines, you know . . .

[Milwaukee Midget]

No motor news – just some grunt work.

The old deck panel was classic ‘70’s fare – cheapo vinyl over cheapo foam adhered to a cheapo piece of Masonite.  I’d milked it for a while, but I wanted something a bit less breezy.



Used it for a pattern, made some cut outs of sheet aluminum, trimmed it up, ripped the ever-loving s#*t out of my hands, and riveted it into place.  Some firestop calk and foam filled the gaps.  A coat of paint –





Ain’t perfect – good enuff . . .

So I’ve put, what, a total of 14 miles on this car?   Why does the engine bay look like I drove it to Ecuador?  HP wash – took off some flakey paint.  I’ll touch it up when it dries.



It’s easier working on a clean car.  I hadn’t really thought about it much until last week when my buddy, Tim brought over his ’69 Firebird 400.  What a throw-back. 

Remember back in the 1970’s when we would get our hands on wrung out, old muscle cars, usually for between 1,500 and 3,000 dollars, and just continued to hammer them into the ground without any thought of “restoration”?  That’s this car - ridden hard, put away wet in 1982, and then cryogenically frozen in that very state until – well, last week.
 
Beyond restoration, but worthy of preservation.  The brake fluid was the color of Wayno’s Porter.  And I was grease and grime from head to toe.
 

[fordboy628]

Not that anybody cares, but, Steve M. of Festus, MO had the correct answer about my vacation roadkill question.   Living in MO probably gave him an "Unfair Advantage" in knowledge of MO & OK roadkill.   It was indeed the smushed armadillo seen most often.   I counted over 200 betwee Ft. Sill, OK & approximately St. Clair, MO.   Sort of confirms an armadillo invasion from the southern states.............

Other smushed species:   Whitetail deer  4
                                      Coyote            3
                                      Raccoon          10
                                      Possum           27
                                      Wild Turkey     2
                                      Canada Goose  2
                             unidentified rodents  15
                             unidentified reptiles   6

Yes, the drive was incredibly boring.....................

My apologies to all for this dumb thread hijack.
 
Fordboy

[Captthundarr]

Now those are numbers I can understand

[fordboy628]

Midget, et all,

OK, ran a simulation of the BMC 1310's I used to build for SCCA F/Prod & Vintage Vs.  your 999.5

Comparative results:

                             1310cc                               999cc
actual hp                130                                    as yet untested
sim. Hp                  130                                    98
rod length              5.75                                   6.00
stroke                    3.20                                   2.45
R/stroke                 1.797/1                             2.449/1
peak flow demand   160.3 cfm @75.8  ATDC      120.4 cfm @79.0  ATDC
sim. flow demand   111.4cfm @ 94.5% V/E       90.3 cfm @ 100% V/E

OK, the question is: What is important about this?

1  The hp#'s for the 1310 are actual results.
2  The peak flow demand is calculated.  I am uncertain that BMC heads are able to flow this amount of air.
3  The simulation flow demand is adjusted to produce simulation hp that equates to actual hp.  BMC heads ARE
    capable of these flow #'s.

By comparison:

4  The 999 has not run on an engine dyno.
5  The simulation hp is based on 100% V/E.
6  The peak flow demand calculated is within the flow capability of the head.
7  Peak flow demand is delayed by 3.2 degrees, as a result of the rod/stroke ratio.
8  The simulation flow demand is well within the ability of the cylinder head.  This is significant.

Because peak flow demand is delayed by comparison on the 999cc, opening the inlet valve later, (to clear the piston around TDC & ATDC) becomes less of an issue.   And the increased piston dwell around BDC, increases the ability to raise dynamic C/R. Closing the inlet valve asap after BDC will raise the dynamic C/R, reducing the overall cam duration.  Probable good choices are (subject to fitting), MD296, VP8, SPVP8, or another short(er) duration, high lift, maximum flank accelleration camshaft, as has been discussed.

By comparison, because BMC heads cannot meet the flow demands of a 1310cc, it is vitally important to open the valve as soon as possible, as far as possible, to allow the maximum flow potential to occur.

There is NO BAD NEWS HERE for you Chris.   The only other important point to make is this:  Engine builders/designers need to run a simulation before deciding on build geometry, especially major components like crank stroke and rod length.  It would be helpful to know what you will have to work around, what you must accept, and where you can help yourself.

For anybody out there who is interested, this is why simulations can be extremely helpful in making choices about engine build specs.  The limiting factor is that you need to know what you are doing with the numbers, as opposed to plugging numbers in to a program until it spits out a result you like.
 
Fordboy

[Geo]

Reply #1252 on: Today at 09:23:48 AM
By comparison, because BMC heads cannot meet the flow demands of a 1310cc, it is vitally important to open the valve as soon as possible, as far as possible, to allow the maximum flow potential to occur.


Reply #1210 on: May 16, 2012, 10:43:19 AM
I had the head flow benched last week.  Here’s a quick rundown – intake, cylinder 1.

Lift   cfm
.100   44.0
.200   87.6
.300   111.7
.4500   124.1
.500   125.6

Mel C&S tested it all the way to .600 (127.9 cfm), but it’s pretty clear that the party is winding down at ~.450, which I believe is well beyond the demands of the cylinder at that point.


My question for today is:
There was discussion about excessive force, strain, wear by opening the valve too far.  Is there a formula to determine how much opening would be needed to fill the chamber.  I know a running engine is different than a pencil and paper computation. Is there a close enough guess and then could the lift maximum be determined.  Why go beyond what is needed and increase the possibility of breakage?  For this 999 cc engine is opening the valve as far as possible not needed as it is for the 1310 cc.

Fordboy, I need to run a better tally of road kill.

Chris, Good work on the car while having nothing else to do. 

Geo

[fordboy628]

My question for today is:
There was discussion about excessive force, strain, wear by opening the valve too far.  Is there a formula to determine how much opening would be needed to fill the chamber.  I know a running engine is different than a pencil and paper computation. Is there a close enough guess and then could the lift maximum be determined.  Why go beyond what is needed and increase the possibility of breakage?  For this 999 cc engine is opening the valve as far as possible not needed as it is for the 1310 cc.

Geo

Geo, Midget, et all,

So many questions.   I'm going to try to give some generalized answers, while saying that it is always better to give specific answers to specific questions about a specific engine @ FIXED build dimensions/geometry.   Since a picture is worth a thousand words, I'm going to try to post up some graphs of Chris' engine later this week or next week, if that's ok with Chris.

But for the time being:

1   Yes, you can open the valve too far, use too much/too little force, strain parts too much, and have accellerated or excessive wear.
     The trick is to strike an effective balance between a complex set of parameters.
2   I'm thinking you meant "fill the cylinder" when you said "fill the chamber"?   There are some formulas of course.  2 Good books for
     reference are:   "Engine Airflow" by Harold Bettes  &  "Performance Automotive Engine Math" by John Baechtel.   The formulas within
     allow you to calculate various parameters for various engine rpm's.   As you are aware, filling the cylinder is a dynamic process in a
     running engine, as opposed to a single rpm related computation.   This reason is why computer model simulations are better than a
     single rpm computation.  (Unless you are solving for the minimum or maximum of something.)
3   There are lots of computer simulation programs out there.  ALL are useful to some degree, depending on the skill & experience of the
     user.   Very generally, the cheaper/simpler programs define limits, the more expensive/complicated ones can usefully model engine
     performance over a range of rpm.   Keep in mind, OEMs spend many millions to model engine performance, so Caveat Emptor.
     I can't state it any better than I did this morning, so:

For anybody out there who is interested, this is why simulations can be extremely helpful in making choices about engine build specs.  The limiting factor is that you need to know what you are doing with the numbers, as opposed to plugging numbers in to a program until it spits out a result you like.
 
Fordboy

4   Guys guess all the time, about all kinds of build specs.   If you are knowledgeable & experienced, this can work out OK.  BUT, if you
     are not, the situation is so complex, it is very easy to make a poor or bad choice, which can have a very negative impact on your
     build.   My question is: Why guess at all?  Go through the math instead of guessing.   Or find/pay someone to help you/do the math
     for you.
5   There are some very generalized, and simple, formulas for max lift required using the number/size of valves/cyl.   They MAY
     or MAY NOT be useful for the engine type you are using.   As I tried to illustrate this morning (reply #1252) the compromise is
     ALWAYS between flow required, (demand) and flow AVAILABLE, REGARDLESS OF THE REASON FOR THE LIMITATION.   Flow required
     is NEVER dependent on (valve) lift alone.
6   There can be several good reasons to lift a valve higher than maximum flow.   If you are trying increase the area under the edges
     of the "flow available" curve/graph, you want to open the valve/port as rapidly as possible.   Slowing the valve train @ a "reasonable
     rate", (so that the spring can 'control' the valve train mass) MAY require "overlifting".   This should be engineered
     or designed to "prevent" valve train destruction.
7   For the 999cc engine, its' advantage is the smaller displacement's airflow requirements CAN be met by cylinder head airflow.   The
     1310cc engine's airflow requirement CAN NOT be met, even at maximum cylinder head flow.
8   I think I've mentioned once or twice that "It's complicated."   My intent is to be humorous, in a sort of perverted way.   I think most
     everybody "gets" the "complicated" part.   And I think everybody wants it to be simple.   Including me.   But that's not the reality.

OK, time for a cold one.   Hope this helps.
 
Fordboy

[SteveM]

I saw half a dozen smooshed armadillos over the weekend, riding my bicycle about 75 miles through east-central Missouri.  Every time I saw one, I thought about your poll question.

Also, I am learning more than I ever knew there was to learn about these little British engines.

Steve.

[Stan Back]

. . . and cam timing in general.  I'm glad Chris is following all this, 'cause it went way over my comprehension days ago.  I know Chris appreciates all this help -- and I would, too, if I followed all of it.

Whatever -- it sound better than 22 MPH.

[Geo]

OK, time for a cold one.   Hope this helps.

Yes! Thank you very much Capt. Nemo! 

I have thoroughly enjoyed the information and am learning something about all engines not just BMC.

better than 22 MPH

Stan, I think we can add at least a hundred to the 22 when Chris finishes this engine!

Geo

[Milwaukee Midget]

OK, time for a cold one.   Hope this helps.

Yes! Thank you very much Capt. Nemo! 

I have thoroughly enjoyed the information and am learning something about all engines not just BMC.

better than 22 MPH

Stan, I think we can add at least a hundred to the 22 when Chris finishes this engine!

Geo

That is, indeed, the target.  The class record is 121.779.  The car remains a brick in the aero department, and the GT class allows me no latitude there.  But there isn't a lot of frontal area to deal with, which is a plus.  For the time being, let's just shoot for "the fastest damned stock bodied, naturally aspirated, five-port, one liter Midget ever to hit the salt."

Problems –

Two years ago, I needed to limit the front end movement by building up the steering stops.  The Midget was never intended to fit 15 inch wheels, and even with fairly narrow drag fronts, as low as it sits, I had a clearance issue with the tire rubbing against the inside of the wheel well.  My solution at the time was to build up a small weld on the stop on the swivel axle.  Yep, the Midget, and the MGB for that matter, used kingpins and swivel axles until their demise in 1979.  To the best of my knowledge, even the Ford F150 had switched over to ball joints by that time.



When I was offloading the Midget at Maxton last year, I was backing it off the trailer and cranked the steering wheel pretty hard, and then I felt something go “ping”.  Sure as shootin’, one of the little welds popped off, and if I had had to crank it hard, it would have rubbed, and maybe cut a tire.

I knew I needed to address this before Bonneville, but I was having trouble coming up with a solid solution that would provide a positive steering stop without having to re-engineer a pair of no-longer-available swivel axles.

The solution came to me when I realized that while the steering was stopped at the wheel on the side with the broken weld, it wasn’t bottoming against the rest of the stop (the weld was actually a pretty clean break).  What was it hitting on, I thought?
 
How about the inside of the steering rack?




Ordered up some 13/16” x 1/2”, two piece shaft collars. 

Placed the Fastenal order tonight – should have this little headache behind me by the weekend.

[Geo]

How about the inside of the steering rack?

That's how Jaguar did it on the '92 XJS-R. 

We should talk more. 

Geo