Milwaukee Midget

[Buickguy3]

  Or, as I have learned by experience: Don't piss the cook off.

    Doug 

[Milwaukee Midget]

  Or, as I have learned by experience: Don't Plymouth the cook off.

    Doug 

Well, I don't know if I Plymouthed off the cook for sure, but I seem to have ingratiated myself to the chef.

Just got off the phone with Kiwi Steve, and my roll cage mods are approved, along with reconfirmation of my blow blanket.

The Midget has been cluttering up Dave's shop for a while now - I know he's been pan caking to get it done.

Spent the down time putting new bearings on the trailer.  When I pulled the old ones, I almost soiled myself.  Cracked inner race in the driver's side - whole thing just fell apart in my hands.

9 months ago, I was dragging it through the Cumberland Gap and through the Smokies.

I think I dodged a bullet on this one.

[Captthundarr]

Wow, Chris. A with only a couple of hundred pounds on the trailer it shouldn't eat up bearings like that.

[Milwaukee Midget]

My latest Moss Motoring column is up.

http://www.mossmotoring.com/to-go-to-show-to-drive-or-tow/

[fordboy628]

Chris,

Nice, well thought out column, as per your usual.
 
Fordboy

[fordboy628]

Camshaft Design Class, continued.......

Midget,

Attached is a copy of the spreadsheet I generated to calculate the maximum valve lift that can currently be accommodated by your build geometry.  This determines the maximum values for ANY cam that might be considered for fitting at various crank angles with the current head/valve/gasket/piston combo and the resultant space available.   This is based on the build geometry changes proposed for your parts in the reply #1238, on page 83 of your build diary.



Most of the information here should be self-explanatory, but then again, I wrote the formulas for the sheet.  The point of the sheet is to calculate how much valve lift can be fit into the engine, WITHOUT valve clash, at any point of crankshaft rotation.   What is particularly significant here are the dimensions for NET inlet valve lift AFTER TDC & NET exhaust valve lift BEFORE TDC.   If I get ambitious, I might add columns for inlet & exhaust flow percentage to the original speadsheet.   Percentage of flow available Vs flow demand would be interesting to know.......although I do not expect a problem with this engine.  The nice thing about the speadsheet is that different values can be plugged in for say valve height or valve to piston clearance, and the spreadsheet then will automatically calculate the new results.

Did I mention how much I love technology?  (Saves wear and tear on the old sliderule......and frees up time for important stuff like sampling microbrew.......)
 
Fordboy

[fordboy628]

Midget,

Here is the graph & table for the cylinder head flow #'s & the calculated percentages.   SOME VALUES HAVE BEEN INTERPOLATED TO FILL OUT THE CHART.   (LIFT OF .05"/.15"/.25"/.35")   If we get a chance to reflow the head on my flowbench prior to B'ville, I can test @ all lift values.



Note the green line: % of average maximum intake flow for intake flow.

It would be interesting to flow the head with differing valve shapes (say 'Rimflo') to check for any significant differences in the flow rates...........

I would also like to see exhaust flow a higher % of intake flow, say more around 80% average, but this is no doubt the result of the very large inlet valve and the smallish exhaust valve.

So much testing & information; so little time........................

 
Fordboy

[wisdonm]

So will this potential flow support enough power to set a record?

[Milwaukee Midget]

So will this potential flow support enough power to set a record?

A fair question, Don.  SCCA Midgets routinely run 120+, but they have no windshields and about 30% more displacement.  But they usually have a birdcage hanging up in the breeze, more rolling resistance and have big fender flares sticking out.  My aero isn't great, but the frontal area is small.  Compared to an F/Prod with flares and an exposed cage, they're probably about the same.  On the other hand, this engine will be peaky, and I'll have a lot more room to give it the go.

I did read a road test that showed that the stock 1275 Sprite was faster with the top up than down.  Hap down at Acme thinks it should go, and Dema seems to think it's realistic.  As for me, I've laid my money down on this combination.

For me, the fun is in the finding out.     

 

[fordboy628]

So will this potential flow support enough power to set a record?

A fair question, Don.  SCCA Midgets routinely run 120+, but they have no windshields and about 30% more displacement.  But they usually have a birdcage hanging up in the breeze, more rolling resistance and have big fender flares sticking out.  My aero isn't great, but the frontal area is small.  Compared to an F/Prod with flares and an exposed cage, they're probably about the same.  On the other hand, this engine will be peaky, and I'll have a lot more room to give it the go.

I did read a road test that showed that the stock 1275 Sprite was faster with the top up than down.  Hap down at Acme thinks it should go, and Dema seems to think it's realistic.  As for me, I've laid my money down on this combination.

For me, the fun is in the finding out.     

 

Midget,

Enclosed with hardtop/soft top up is always better.  Hardtop is most likely better than moving (deformable) soft top.  The real questions are:  "By how much?"   Coastdown testing can help you figure out C(drag) number.   There are accurate formulas for top speed based on Hp/frontal area/C(drag)/etc.   BTW, did some crude C(drag) testing years ago @ Blackhawk Farms Raceway, the drag from roll bars/cages sticking out in the air was substantial.

With/without flared fenders is easier:  Less frontal area is better because it's less.  Just figure how much less the area percentage is and you have your potential improvement.  Think back to the Smokey Yunick 7/8 scale Nascar Chevelle (?).   Nascar outlawed it @ the first outing, NOT because it was SLOW.......
 
Fordboy

[Milwaukee Midget]

I would also like to see exhaust flow a higher % of intake flow, say more around 80% average, but this is no doubt the result of the very large inlet valve and the smallish exhaust valve.

To: Professor Fordboy – Adjunct professor of A-block studies, University of Abingdon, Great Lakes Campus

Both you and Dr. Dema have expressed exhaust flow as a ratio with regard to intake flow.  We've determined that the intake flow on this head is more than generous to the needs of the engine.  Provided we have correct timing events on the exhaust side, will the exhaust flow, in actual flow numbers, not as a percentage of intake, meet the demands of the engine? 

Are the two inextricably linked, or is it simply a function of how big a valve or port a head can accommodate?

[fordboy628]

BMC Block Cleaning:

Midget, et all,

As we discussed during your last foray beneath the Cheddar Curtain, thorough cleaning of BMC blocks is deceptively difficult.

1   Everybody recognizes the neccessity of removing the main oil gallery brass plugs, but ALL the plugs to the various oilways should be removed for cleaning.   I prefer to tap the block for screw-in plugs to make subsequent cleanings easier, but if the engine is not going to be taken apart a lot (say hot street engine Vs race engine) hammer in plugs are OK.

2   The 2 plugs that get overlooked most often are the 2 for the oil pressure relief valve oilways @ the rear of the block below the oil pressure relief plug.   1 plug on the side & 1 on the oil pan rail.   Take a look at the photos below.   A lot of bearing killing crud can be trapped in these 2 passages.





3   I think that everybody removes the oil pressure relief shuttle from under its' threaded cap, (shuttle shown on the left)



but I have found that most people are unaware of the "spool" that the shuttle seats against.  (Spool shown on the right.)  The shuttle seats on the spool, as shown below:



The spool, which is pressed into the block, MUST be removed for thorough cleaning. (Especially if you have done any machining.)  Removing the spool is easier said than done, because of the press fit into the block.   The method I use to remove the spool is to:

A   Tap the spool 3/8 UNC.   You only need to tap 3/4 threads deep.
B   Firmly install a 3/8 UNC bolt into the threads you just cut.
C   Grasp bolt with a slide hammer and gently tap out spool.

There are various other methods that will work to remove the spool, such as "jacking" the spool out with a bolt & washers, etc.

Once you have the spool removed, you may be suprised how much bearing killing crud and/or swarf is in that passage...............

I have often removed the brass cam bearing restrictor from the center main bearing area as well, when I prep for cleaning.  Both the restrictor & the spool need to be cleaned & re-installed for assembly, or new ones fitted.

Note that the inner vertical oil passage of the block, for oil to flow past the relief shuttle, MUST REMAIN OPEN. Plugging this passage will prevent oil relief shuttle oil flow to return to the oil pan and render the oil relief and/or pressure adjustment non-functional.

The BMC race engine oil passage modifications that we talked about & I have been using with good success, I will detail in a subsequent post.
 
Fordboy
 

[fordboy628]

I would also like to see exhaust flow a higher % of intake flow, say more around 80% average, but this is no doubt the result of the very large inlet valve and the smallish exhaust valve.

To: Professor Fordboy – Adjunct professor of A-block studies, University of Abingdon, Great Lakes Campus

Both you and Dr. Dema have expressed exhaust flow as a ratio with regard to intake flow.  We've determined that the intake flow on this head is more than generous to the needs of the engine.  Provided we have correct timing events on the exhaust side, will the exhaust flow, in actual flow numbers, not as a percentage of intake, meet the demands of the engine? 

Are the two inextricably linked, or is it simply a function of how big a valve or port a head can accommodate?

Midget/Grasshopper,

In a word: "Yes."

In 2 words: "It's complicated."

In a few words: "All of the above."

My specific concern is/was that the exhaust/intake ratio dipped into the 69/68% range @ .25"/.30" lift.  I prefer to see the lower #'s for this ratio to be about 75% and the upper #'s about 85%/80%.   Having said that, lower flow capability on exhaust (or intake for that matter) can be helped/fixed with different cam timing/duration.   Your head, with the Longman valve sizes, favors intake flow.   I have always found this to be a good thing for normally aspirated engines.   Because of the physical limitations of the BMC engine's geometry, giant intake valve = smallish exhaust valve, and the two are therefore linked together.

Physical limits of both ports is a function of the casting, controlled by the manufacturer, but again, it's not as simple as bigger port alone = more Hp.  Several things conspire to limit flow: Valve size (dia.)/valve shape/valve angle to bore/port size (volume)/port shape/port angle to bore, etc, etc.  Some of these variables are fixed and some can be changed within some smaller parameters.  And too much flow/port volume/etc. CAN (WILL) make the engine peaky (cam sensitive) and difficult to drive.  Ports that are too big kill Hp thoughout the range, except @ peak power.  It does not do any good to have great peak Hp coupled with LESS area under the Hp curve...........

Having said all that, exhaust flow does not need to match intake flow.  Intake valves on normally aspirated engines only have barometric pressure to "push" air into the cylinders combined with the draw (demand) from the piston going down the bore, away from TDC.  Exhaust valves on the other hand, have high cylinder pressures (many times higher than atmospheric) available to initiate flow when the valve first opens.  And they have the piston going up the bore to "pump" out the remainder.  (Although "pumping" causes losses.)  There is some professional "disagreement" on what the "proper" ratio of intake flow to exhaust flow should be.   The proper cam for the application will take this "flow bias" into account.

The bottom line (for me, anyhow) is: I think your cylinder head exhaust flow is at the lower limit of what is adequate for your engine, and should be OK.  Worst case scenario is: the cam may need to be a dual pattern cam, with additional duration on the exhaust.   Making sure the cam/valve events will physically fit into the space available needs to be determined ahead of time.  This has always been the trick to this pony.

Hope this helped your camshaft/cylinder head migraine.  If you are not completely relieved, my prescription is to take 3/4 PBR's just before bedtime.
 
Fordboy

[Milwaukee Midget]

BMC Block Cleaning:
Removing the spool is easier said than done, because of the press fit into the block.   The method I use to remove the spool is to:

A   Tap the spool 3/8 UNC.   You only need to tap 3/4 threads deep.
B   Firmly install a 3/8 UNC bolt into the threads you just cut.
C   Grasp bolt with a slide hammer and gently tap out spool.

Oh, that's funny.  That's rich, pal.  Ha Ha Ha.

Grasp bolt with a slide hammer and gently tap out spool.

My arms haven't been this sore since before I let my Playboy subscription lapse.



But it is out.

[fordboy628]

With/without flared fenders is easier:  Less frontal area is better because it's less.  Just figure how much less the area percentage is and you have your potential improvement.  Think back to the Smokey Yunick 7/8 scale Nascar Chevelle (?).   Nascar outlawed it @ the first outing, NOT because it was SLOW.......

Submitted for your perusal and amusement, the Yunick 7/8 Chevelle.  Note how small it is compared to the other cars in the pits & on the track...........                                      No advantage there......................

https://www.google.com/search?q=smokey+yunick+7/8+chevelle&hl=en&prmd=imvnso&tbm=isch&tbo=u&source=univ&sa=X&ei=K-UaUOK7IcfDrQGtgoGQBw&sqi=2&ved=0CGkQsAQ&biw=1536&bih=710

 
Fordboy