Milwaukee Midget

[Rex Schimmer]

Chris,
My vote is for the studs, I think your concern regarding screwing the long bolt in and out of the oil ladder a number of times can only be asking for trouble with the aluminum threads. If you go with the new oil ladder I would also "bin" the gasket and O ring all of the holes that the oil goes through. A much better seal and then the gasket material is not in the stack to potentially be a preload problem when tightening the studs.

Rex

[wisdonm]

Have you considered using Time-Sert s to cure some of those problems. Much better than Thread-Sert s.

[Milwaukee Midget]

Have you considered using Time-Sert s to cure some of those problems. Much better than Thread-Sert s.

Let's put that on the table.

By the way, Don - I'm picking up a disassembled Bugeye on Saturday.

[Jack Gifford]

... if these were two abutted 12 inch solid billets... difference between the two at 220 degrees to be about .020 [inches]...

What length of adjoining metals (steel/aluminum) are you trying to compare for thermal expansion? I assumed 12". But we're not even close on our results.

Engineering ballpark numbers are 6 x 10 ^ (-6) for steel and 1.2 x 10 ^ (-5) for aluminum (and for common alloys of each). That's per degree F. It's a 'pure' number (inches/inch, etc.).

[gkabbt]

.....I'm picking up a disassembled Bugeye on Saturday.

And we're going to do what with said Bugeye?   Another racecar.....COOL!   Modified Sports for FordBoy with the Grenade engine?   
The more the merrier.....LOL!  

Gregg

[Interested Observer]

Working towards getting a handle on the “stock” clamp load, using the bolt measurements Midget provided, the effective spring constant of the stock bolt is 171,333 lb/in or 6,745 lb/mm.  Applying a half-turn of 1.25mm pitch thread would then produce a bolt load of 4,216 lb with a stress in the smaller diameter section of 53,000 psi.  This, assuming a stiff gasket and column of aluminum in the stack.  In reality, the numbers would be somewhat smaller.  Assuming a peak cylinder pressure of 150 bar or 2200 psi, the endload on a 75mm bore would be 15,070 lb.  Then, assuming about a 180 degree F temperature rise, the stress and load would likely increase about 20-25%.  The question then being, how stiff is the gasket?  Does the temperature increase induced load increase further compress the gasket, leading to reduced clamping force upon cooling? 

Given these numbers, it would seem that there isn’t a lot of margin provided on the clamp load.  The stress level seems reasonable and the need for a stiff gasket is apparent.  However, the half-turn of the bolt seems too simplistic.  Is that turn predicated on a preliminary draw-up?  Something like “Torque it to XX to stack things together, THEN apply the half-turn”.  That would gain some margin in clamp force.  Midget--is there anything like this in the assembly manual?  Also, do they say anything about re-torqueing?

In light of this, the ARP 50 lb-ft spec, resulting in almost 12,000 lb of bolt load seems quite excessive.  It is not clear how much consideration they may have given the system into which their part is fitted.  It looks like they just specified a torque that gave their preferred 75% of yield on the stud.  That much load might wreak havoc on the engine parts.  Using a stud does have the advantage of possibly being able to pull the head without undoing the rest of the engine.

As regards the Rover edict to change the ladder along with the gasket type--this just doesn’t seem to make any sense.  The materials are essentially the same and the minimal added stiffness borders on inconsequential.  Sounds to me like “As long as you have it apart to change the gasket, might as well put in the “new” ladder”.  The only other thing would be the possibility of their having made some oiling changes in the ladder, but this seems unlikely.

[Milwaukee Midget]

Given these numbers, it would seem that there isn’t a lot of margin provided on the clamp load.  The stress level seems reasonable and the need for a stiff gasket is apparent.  However, the half-turn of the bolt seems too simplistic.  Is that turn predicated on a preliminary draw-up?  Something like “Torque it to XX to stack things together, THEN apply the half-turn”.  That would gain some margin in clamp force.  Midget--is there anything like this in the assembly manual?  Also, do they say anything about re-torqueing?

Yes, and I clearly misled on this one.  Laziness in presenting the facts.

The initial pull up is 20 nm - ~15 ft lb.  After that point, one then proceeds to the additional turns.

The factory manual says two 180 degree turns.

Other sources I've been reading say two 90 degree turns. 

I didn't pay a lot of attention to the difference in the two sources in light of the fact that I wasn't even considering the stock bolts as an option.

My mistake there - I appreciate the mathematical exercise you're going through, and I fed you bad information.

Regarding re torquing, the manual specifically says not to.

I've got some queries out to a service manager/writer in Great Britain and a fellow who races the K in his MG TF in Great Britain regarding what they've used/recommend, and what issues they've encountered or overcame. 

And we're going to do what with said Bugeye?   

Think along the lines of a cartoonish little British Rat Rod . . .

[4-barrel Mike]

And we're going to do what with said Bugeye?   

Think along the lines of a cartoonish little British Rat Rod . . .

Start with:



End up with:



or



Cool!   

Mike

[BHR301]

Just a suggestion. 

Bill

[Interested Observer]

OK, now we’re looking a bit more realistic.
The 20nm torque would produce 3400 lb tension at about 43,000 psi shank stress--and probably take the best part of the squeeze out of the MLS gasket.
Then, superimposing the half-turn, we total up to about 7,600 lb bolt load and 96,000 psi shank stress--or somewhat less due to further compression of the gasket and all the aluminum in the stack.  We can approximate that later.

The 2 x 180 degree turns would be about 11,800 lb and 149,000 psi which seems like a lot.  Perhaps this was the spec for the early versions with a presumably composition (more compressive) head gasket, which would not result in reaching these numbers.

So, looking at the 96,000 number, if you ever get a reply on the material, it will probably be reasonably high strength--110-120ksi.   And this does not include the added stress of the differential thermal expansion which is probably good for 20-25% increase.

Again the unknown--how does the gasket behave?

Are there ports in the head and girdle to let the oil return flow through the bolt channels?

[Milwaukee Midget]

Start with:

Yeah, that's just about where I'm starting . . .

End up with:

Uhhh . . . I like the color . . .

or

Moon discs - yes - Moon shot . . . 

Keep in mind, I may drive it to Wendover next summer . . .

[Captthundarr]

You could start with is and get it out of my way before I drop a blown sbc in it.

[gkabbt]

Keep in mind, I may drive it to Wendover next summer . . .

Let's see.....You're five-foot-seventeen tall, have a size 15 foot and Wendover is a LONG way from Beerhaven in a tiny car.      
Leads me to ask: Where will Mrs. Midget sit and what about luggage for you two for a week?          


As for the Moon Shot Bugeye, I LOVE IT!
Two things it NEEDS.....A (real) straight front axle and Hilborn injector stacks poking through the bonnet instead of the 3x2's!

Don't know if you have this bookmarked but here is the link to BritishV8.org that has some engine conversion ideas:

http://www.britishv8.org/Photos-Austin-Healey-Conversions.htm

Gregg

[gkabbt]

You could start with is and get it out of my way before I drop a blown sbc in it.

Frank, Don't know if you have this but here is the britishv8.org link for MG conversions:

http://www.britishv8.org/Photos-MG-Conversions.htm

Gregg

[Captthundarr]

 :-Ds