Milwaukee Midget

[fordboy628]

Chris,

Enjoyed the MG articles.   Thanks for making the effort to document your efforts.   I'm sure many others will benefit from your journey.

See, you already have command of the language!

Fordboy

[fordboy628]

Some quick thoughts on your disassembly photos:

1   Steel cam + steel thrust plate = non-compatibility.   Probably need a bronze or silicon aluminum bronze thrust plate to bear against
     the steel cam thrust face.    How much end play did the cam have on build-up?   (should be .003"/.005")   These types of material
     compatibility problems are common when "upgrading" parts.   Guys put titanium valves in cast iron guides & then wonder why the
     valves seize in the guides, regardless of clearance.   Does APT have a non-steel cam thrust plate?   Now you know how steel friction
     welding works.

Midget,

Had a additional thought on the cam thrust plate.   Because of all the differences between BMC oil pump drive types, I have had problems when changing from one drive type/cam style to another.   The problem was the oil pump drive shaft "bottomed" in the cam, and forced the cam forward and into the thrust plate.   This was discovered during build-up so no damage occured.    I think you should check this carefully.   After the cam is installed and the endplay checked, the oil pump should be installed and the cam endplay should be checked again to verify that the cam is not being forced forward into the thrust plate.   I ended up having to shorten the oil pump drive shaft to regain cam end play.   I understand that some oil pump changes require a spacer plate between the block and the oil pump.

Consider creating a build sheet/checklist to use when assembling your engines.   It will give you something to refer back to when questions arise.

 
Fordboy

[fordboy628]

Midget, et all,

Does paying attention to all the little details matter?   I dunno, but I think you should ask the guy who finishes second.....

http://www.popularmechanics.com/cars/news/vintage-speed/the-spring-that-revolutionized-nascar-6643778

Here is something to make you think.
 
Fordboy

[Milwaukee Midget]

1   Steel cam + steel thrust plate = non-compatibility.   Probably need a bronze or silicon aluminum bronze thrust plate to bear against
     the steel cam thrust face.    How much end play did the cam have on build-up?   (should be .003"/.005")   These types of material
     compatibility problems are common when "upgrading" parts.   Guys put titanium valves in cast iron guides & then wonder why the
     valves seize in the guides, regardless of clearance.   Does APT have a non-steel cam thrust plate?   Now you know how steel friction
     welding works.

Just got off of the phone with Phil at APT - It appears as though they're still available for the MGB, but not for the A-series.  That said, he's going to dig around the shop and see if he can come up with an older bronze take-out.

Also dropped off the cam at C&S.  I'll have profiles to throw into the equation by Friday night, and according to Mel, port flow figures.

I finished stripping the block last night.  The oil pump is A1 - no issues or problems there.  At least something came out of this unscathed. 

Of course, I just dropped the cam off, so I can't check the fit of the oil pump drive to it, but I'm wondering if the oil pressure in the pump might be driving the cam forward . . .

[Geo]

Chris,

I have been thinking about the findings on teardown.  And the past engines I've worked on.  The memory is dark however the light is getting brighter.

I would have to see the gear relationship to see which way the force is applied.  Towards the thrust face, so then it's too much force.  Caused by what?  You thought on the oil pump is in the right area.  You also need to check the force needed to turn the distributor.  If the distributor is tight when clamped in the block the same problem will occur.  I would assemble things an item at a time and turn them by hand to be sure they are free. 

Install the distributor and clamp it down.  Any end play?   Spin freely?  Put the pump in and tighten it down.  Any end play?  Spin freely?  Put the pump and distributor in the block.  Any end play?  Spin freely?  Put the cam in the block. Any end play?  Put all three in the block.  Any end play?  All three spin freely as a team?

Fordboy I liked the valve spring article.

Geo

[Milwaukee Midget]

Geo - good hearing from a BL Certified Jag guy.

What would you say if I said I'm running a crank trigger and no distributor?  I'd ask, does the dizzy drive help locate the cam fore and aft?

?

I guess I don't know for sure - I'd assume little or no difference, but I guess I'm done assuming anything at this point.

 

Cheers, brother!

[Geo]

Chris,

How is your oil pump driven?

Geo

[Jack Gifford]

... What would you say if I said I'm running a crank trigger and no distributor?...

I would have to ask: how are the crank-triggered sparks distributed to the individual sparkplugs?

Last engine I built has crank-triggered ignition, but retains the "distribution" function of the distributor. I'm interested to hear about other schemes.

[Milwaukee Midget]

Geo, that would be off of the back of the cam - back of the engine, direct drive slotted shaft arrangement.  My thought is that oil pressure builds up in the pump and forces the shaft forward toward its total clearance, taking up any clearance at the sprocket end of the cam.

Jack, it's the toothed wheel at the front with a sensor - Electromotive system - two coil pacs - ECU - wasted spark - no distributor - reads off of the 11th tooth, but can be programmed to run just about any way you want.  It has a lot more functions than I really need.  I set mine up for a knock sensor to prevent me from blowing it up - at least blowing it up THAT way . . .

It's pretty slick.

http://www.electromotive-inc.com/products/xdi2.php

[fordboy628]

Midget,

Because of all the differences between BMC oil pump drive types, I have had problems when changing from one drive type/cam style to another.   The problem was the oil pump drive shaft "bottomed" in the cam, and forced the cam forward and into the thrust plate.

Std BMC oil pump is a lobe & rotor style pump, so the only movement lengthwise is the lobe/shaft end play in the housing, probably .003" or less.   Probably not an issue, unless as above, the pump is "bottoming" in the rear cam journal/oil pump drive slot/star/pin.   This is another quirk of the BMC design, be happy your chosen powerplant is not a V-12 RR Merlyn Aero......    The cam installation and checking procedure suggested by Geo appears to be a thorough and sensible way to check everything on build-up.   Driving helically cut distributor drive gears probably imparts a small force on the cam, whether forward or backward I do not know.   But, I doubt that it is essential to preventing cam thrust wear, just doesn't make sense.

Aero engines and Nascar Cup engines have engine assembly checklists that are multi-page "booklets", where the person performing a task, "signs off" that a procedure is finished to "spec".   I'd be happy to suggest items you should check & record for an engine assembly record, each time you build/assemble the little "time bomb".   When working on a build spec as orphan as yours, you really can't make ANY assumptions about anything.   "Remember the Maine, er, thrust washers!"   Custom parts create issues that do not exist with a stock engine build.   And then they require additional steps and/or creative solutions for all the bits to function properly together.  And the need to check "everything" because your little jewel requires a level of tolerancing & precision above the standard for a racing V-8.   Your getting into an F-1 level precision requirement because of the small displacement of your engine and the bhp/litre required.

Judging by the number of "orphan" powerplants on this site, it appears that utilizing an "orphan" powerplant is a huge part of the "fun" factor for LSR racers.   Or perhaps LSR racers are the untapped reserve of non-conformists with an additional masochistic disorder?   I am unable to judge because I'm not a psychiatrist, AND, I realize I'm similarly afflicted with an affection for the "orphan".   Or maybe as a child my mom just told me "You can't do that!" too many times.   I don't know and I'm old enough to not care anymore.   There doesn't appear to be any other sensible explanation and remember Occam's Razor: "The simplest explanation is usually the right one."   That applies to your engine as well.

Captain Nemo

PS, Research I did yesterday supports previous info that MOST Longman "Big Valve" racing heads were supplied at 21.4cc's chamber volume.
http://www.somerfordmini.co.uk/eshop/index.php?main_page=page&id=206&chapter=20

Geo, makes you wonder what they don't talk about in big money racing, ie: superlight carbon fiber or unobtanium parts, etc............

[Milwaukee Midget]

. . . be happy your chosen powerplant is not a V-12 RR Merlyn Aero......    

That would put me in AA/GMS, AA/FMS, AA/BGMS or AA/BLMS, depending on which fuel I'd run, and if I wanted to supercharge it.

I've got enough on my plate without trying to determine where to sit . . . 

 

[fordboy628]

. . . be happy your chosen powerplant is not a V-12 RR Merlyn Aero......   

That would put me in AA/GMS, AA/FMS, AA/BGMS or AA/BLMS, depending on which fuel I'd run, and if I wanted to supercharge it.

I've got enough on my plate without trying to determine where to sit . . . 

 

Ummm, ahhh,  Rolls Royce Merlyn Aero is the 1600 cubic inch, 1600 HP, centrifically supercharged (with 2 supercharger speeds no less) powerplant for the Supermarine Spitfire, P51 Mustang and other WWII warbirds as well.   Possibly, a bit too large for the Midget....................

For anything powered by a Merlyn, methinks thine posterior would be placed in the "cockpit".   Use of 'chute optional...............
 
Capt Nemo

[Milwaukee Midget]

Ummm, ahhh,  Rolls Royce Merlyn Aero is the 1600 cubic inch, 1600 HP, centrifically supercharged (with 2 supercharger speeds no less) powerplant for the Supermarine Spitfire, P51 Mustang and other WWII warbirds as well.   Possibly, a bit too large for the Midget....................

Captain Nemo, you need to stop pumping out your basement and read that rule book I left you.   

Okay, so that narrows it down to AA/BGMS ot AA/BLMS.

Might take a little bit of tinsmithing - it's been done -

http://www.landracing.com/forum/index.php/topic,7226.0.html

http://www.landracing.com/forum/index.php/topic,7295.0.html

http://www.landracing.com/forum/index.php/topic,10112.0.html

That would be a great BIG orphan engine!

[Geo]

OK, enough dreaming.  Back to work. 

Chris, two things: Pump to cam drive contact and/or cam walk.

Pump to Cam drive contact: If it is the pump then the drive and the cam will have wear on the tip of the pump drive and the bottom of the cam bore/slot.  Not the edge of the drive but the end and bottom in line with the shaft.  Take a good look Chris it may be hard to see.

spade drive, pin derive or star drive.
http://www.minisport.com.au/category22_1.htm

http://www.calverst.com/articles/Eng-Lubrication-Oil_pumps.htm
Especially do not fit the pump until the cam timing has been done.

And for those who do not understand why us British car owners drink...

Another area of complication.
There are three types of oil pump drive: pin, spider and slot.
There are two pump shaft lengths, short for 850 & 998 and long for 1275.
There are 2-bolt, 3-bolt and 4-bolt pumps.
Early engines have 3-bolt. The later engines went to 4-bolt, but now the pumps most commonly available for 1275 engines are 2-bolt.
Now, you can fit a 2-bolt pump to an engine drilled for 4-bolts so long as the 4th bolt hole has not been drilled through into a waterway which, if the engine is an early 3-bolt type modified to take a 4-bolt later pump, it may well have been. If a threaded bolt hole has gone into a waterway and a 2-bolt pump is to be fitted it is vital to either drill out the pump casing to take the 4th bolt, or blank off the redundant hole in the block. If you don't you may get what I got on my Cooper 'S', 2 pints of Valvoline oil in the water!
Now I check each time before I fit an oil pump.
Also, the AP technical spec sheet lists the same pump for a pin-drive 998 as it does for a 1275. Whatever you do don't fit the 998 pump to the 1275 if you have a pin drive cam as it only engages on the pin by about 1/16" and will probably snap off with loss of all oil pressure.

There are two pump shaft lengths, short for 850 & 998 and 1100
 and long for 1275 and the 970 and 1071 blocks

its a common mistake for people to stick a 850 pump into a s block (due to old cam drives and what not) and have problems with the drive shearing off. sometimes (dependant on the drive) the pump and the cam will 'just' mate so you thing its all ok, then when the timing gear starts to pull the cam back and forth in use it will drop out of drive and thats no oil pressure.

thats why i always advise to upgrade to a modern metro 'spade' drive cam and pump. then its easy, one cam, one pump either long or short nosed.

the trouble with the modern '2 bolt' pumps is that in stuff like old s blocks with 3 or 4 bolt fitting is that you will (or may) need to re drill and tap the block to accept the new pump. if you do this its important to cap the old unused bolt holes with cap head screws (as pete found out....)

as the old pumps go nla (like the cooper s one) is proably best to prep blocks to suit the metro spade pump whilst the engines in bits, as its solves any problems years down the line.

http://www.hi-flow.com/HP012cVT.html

Interesting to read about installing different pumps and creating leaks between oil and cooling systems.


Cam Walk: How are the lobes tapered on your cam? like the GM forcing the cam to the rear?

A flat tappet cam having tapered lobes force the cam to the rear (GM 60 degree V6)

Your cam is moving to the front leading me to think the cam is walking even though it's not supposed to happen with a flat tappet cam.

Cam walk and a test.  http://www.iskycams.com/pdfcatalog/2004-05/page192.pdf

Hope this helps.

Geo

[fordboy628]

Geo, Midget,

Like I keep saying, "It's complicated."   And with BMC's perhaps unnecessarily so.   So many oil pumps, so little time..............

Illustration 3 of the Isky article shows the taper ground cam lobe and radiused "flat" tappet relationship.   Midget's cam is ground with the taper toward the rear (front of the lobe high) which should walk the cam forward into the thrust plate, if no other machining errors exist.   Still, steel billet cam + steel thrust plate = friction weld.   It's why Chevy's with billet steel cams run bronze distributor drive gears and roller thrust bearings.   Cam/cam gear/thrust plate/oil pump need to be trial fitted as you suggested, while checking for proper cam end play throughout the oil pump fitting process, a BMC quirk.   If you are going to race a BMC powered vehicle, I agree with you that a person needs to develop a tolerance for and familiarity with spirits.   I would also humbly suggest that fitment for a cranial C-clamp and a tendancy toward masochism would also probably be helpful.  Does this explain the British obsession with bloodsports such as rugby, cricket and darts?

Thanks for all the research.
 
Capt. Nemo here, until Mrs. Fordboy is parboiling away in the repaired hot tub..................now where did I leave my all weather pvc glue?