Milwaukee Midget

[fordboy628]

Here we go,
specially for Fb and MM

Ford Sierra P100 pickup (same basic body as your Merkur ?)
Drop the Cosworth 2 litre lump in and get a bigger turbo, then 500 HP easy 

Yeah Baby!!  Just weird enough for me.  Can we get Mistress Helga to drive it??  Gotta do something about the pickup bed though..........

F/B

[fordboy628]

Midget,

Due to the magic of FedEx, new 25ml (cc) burette & stand in hand.   New toys, oh boy, oh boy...................
Whoa!! WE COULD TITRATE BEER WITH THIS!!     Oh wait, 25ml is a pretty small serving..............
 
Fordboy

[fordboy628]

Midget,

Just curious, what type of spark plug wires are you using?

F/B

[Milwaukee Midget]

Midget,

Just curious, what type of spark plug wires are you using?

F/B

MSD 8 mm Street Fires - 500 ohms/foot.  Needed a supression cable for wasted spark.

[fordboy628]

MSD 8 mm Street Fires - 500 ohms/foot.  Needed a supression cable for wasted spark.

Yeah, non-suppression wires will play hell with the ignition computer.   Thanks.

Fordboy

[38flattie]

Chris, sorry I was side tracked and missed this:

HAPPY BIRTHDAY!

[Milwaukee Midget]

Chris, sorry I was side tracked and missed this:

HAPPY BIRTHDAY!

The best birthday gift would be seeing that antique of yours push past 500 hp.

Thanks, for the wishes - now get back to work! 

[Tman]

Happy Bday!

[Andy Cooke]

Come dyno day, we'll see if indeed I might have too much lift.

Midget, et all,

I know this is hard to visualize without a graph or chart, but please read along and I can answer anyone's specific question in a later post.  In a phrase, "It is more complicated than that."   And what I mean by that is, that changes in the rocker ratio change more than just the lift curve.  Although 'overlifting' valves is related, the other change is to the EFFECTIVE duration of valve timing events.  Because higher ratio rocker arms increase the valve displacement at EVERY POINT on the valve displacement curve, they also have the NET effect of increasing the EFFECTIVE duration of ANY cam used.  Now we could argue all day about what net valve lift value constitues "EFFECTIVE" camshaft duration, but I'm going to get all passive/aggresive on you guys by saying: "The only valve event I care about on this engine @ this time is: 'EFFECTIVE' inlet valve closing".   And I reserve the right to change my opinion, at any time, without notice.

IF, substituting a lower ratio rocker arm assembly produces more torque at a given rpm, (& therefore more hp) the inference is that the valve events are too "long", ie, too much duration,
OR, the inlet valve 'effective' closing point is too late for the engine's combination of build geometry & gasflow,
OR, the engine does not have enough compression ratio to take advantage of 'long' duration valve events,
OR, a combination of the above,
AND/OR, other build geometry/gasflow factors I did not include, etc, etc, etc.
Also a factor here is that the smaller the displacement of an engine's cylinders (and this is different from TOTAL engine displacement) the more 'sensitive' it is to 'effective' valve timing events.

The risk of this test is that peak hp MAY be compromised by the gasflow loss at net total valve lift at, and around, full open intake/exhaust valve events.  However, an increase in peak torque, even coupled with a loss of peak hp, (subject to analysis) would typically indicate the engine needs 'less' cam duration and/or more compression ratio.  These types of tests are part of the engineering/tuning process.  I am expecting to see a rise in peak torque AND, a slight loss in peak hp, and analysis of the data generated will indicate what other changes (if any) should be made.  I am particularly interested in seeing what sort of BMEP this engine produces, regardless of rocker ratio.   See how simple that was........

Kind of like a chess game, lots of pieces, lots of moves, net result: It's complicated.  Lots of guys smarter than I am spend endless amounts of time debating about this stuff.  As for me I'm simple, all I care about is: net results.
 
Fordboy

I'm really pleased to see you showing an interest in this build, I'm sure that this engine is going to be a good step better for it.

I stopped playing with A series engines before I got into the habit of plotting every cam that came my way, so can't help with your valve accelerations, but I suspect it'll be the maximum you can get from the follower diameter.  I can't disagree with your comments about inlet valve closing time (I don't have anything like your knowledge on this), but I was coming at the 1.25 rockers from a different direction, that of reducing overlap (measure that how you prefer).  To me the magic happens during overlap, and equally it's the phase where things go wrong if you don't have the acoustics right.  It's unlikely that this engine will have the right lengths and diameters without a lot of dyno time, so mine was a suggestion that less may be more.  I'm a simple soul, and like to keep my theories simple

With regard to optimising inlet valve closing time and compression ratio; will that still be correct in the ~85% atmosphere at 4000ft?  I have no experience of this as 400ft is high around here, but I suspect that an engine that's fussy in this respect will struggle at Bonneville.  I throw this out there as I'm interested in the answer.

go fast
Andy

[fordboy628]

Midget,

Happy Belated Birthday!!  As if anyone our age wants to acknowledge another one.......though I guess it beats the alternative!!

Best,
MB

[fordboy628]

Come dyno day, we'll see if indeed I might have too much lift.

I'm really pleased to see you showing an interest in this build, I'm sure that this engine is going to be a good step better for it.

I stopped playing with A series engines before I got into the habit of plotting every cam that came my way, so can't help with your valve accelerations, but I suspect it'll be the maximum you can get from the follower diameter.  I can't disagree with your comments about inlet valve closing time (I don't have anything like your knowledge on this), but I was coming at the 1.25 rockers from a different direction, that of reducing overlap (measure that how you prefer).  To me the magic happens during overlap, and equally it's the phase where things go wrong if you don't have the acoustics right.  It's unlikely that this engine will have the right lengths and diameters without a lot of dyno time, so mine was a suggestion that less may be more.  I'm a simple soul, and like to keep my theories simple

With regard to optimising inlet valve closing time and compression ratio; will that still be correct in the ~85% atmosphere at 4000ft?  I have no experience of this as 400ft is high around here, but I suspect that an engine that's fussy in this respect will struggle at Bonneville.  I throw this out there as I'm interested in the answer.

go fast
Andy

Thanks for the confidence factor.   I also suspect that the flank accelerations of this camshaft are @ or near the maximum for the follower diameter.   Whether that is good or not depends mainly on whether the valve is open enough, Vs TOO MUCH, for the port to be able to flow enough to meet the peak demands of the cylinder ATDC, @ SOME SENSIBLE GAS SPEED.   This can be calculated and I've started doing some of these, but I am hung up @ the moment from lack of dimensions/airflow numbers of cyl head/exact cam profile/etc, etc.   Pipe sizes and lengths can be calculated & modeled, & again I need more information about other engine build specs.   Yes, it can be done with LOTS of dyno testing, but that is expensive and will use up a "test mule".   My experience is that modeling & simulations can save time & cut cost, AS LONG AS THE CONCLUSIONS ARE CONFIRMED ON THE DYNO.   I have some good experience doing this, on both BMC & Ford/Lotus/Cosworth 4 cyl engines, and trust me, going to the trouble of figuring things out ahead of time is the way to go.   No more cut & try for Fordboy!!

I am going to presume that by acoustics you are talking about wave tuning of the inlet/exhaust systems.   In terms of valve events, the effective inlet closing point is the most important, because it directly impacts DYNAMIC compression ratio.   Your STATIC compression ratio is what you calculate in terms of displacement differential, but your running engine doesn't care about that.   And even if your static C/R is 13/1, if your volumetric efficiency is 110%, then 13x110% = 14.3/1 at that V/E!!   You might want to know that, if only for the additional stresses on the parts.   However, no BMC I ever dynoed made over about 90/95% V/E, because of the 5 port head.   Now some BMC's don't get to 90% V/E, because with their limited airflow, they are sensitive to "build combinations".   Your decision to be conservative on parts is a sensible one, because as the output is raised the engine becomes more "sensitive" to parts combinations, AND, there are MORE OPPORTUNITIES TO BE WRONG.   Think about that, like I said, it's complicated.   Now I want to qualify my experience with BMC's and defer to those with more & longer experience in building race combinations, some have probably exceeded 100% V/E, I just don't know about them.   But back to the example 13/1 C/R @ 90% V/E = 11.7/1 C/R.   Hence, my issue with wanting to know the BMEP of this particular BMC engine combination.   Peak BMEP of well thrashed combos SHOULD be around 220/225psi.   Lower numbers indicate room for improvement, REGARDLESS of where the improvement comes from.

Valve events at overlap present some opportunities for impressive wave tuning or massive reversion.   In any racing engine, the returning exhaust pressure wave can & does create inlet tract pulses that exceed peak cylinder demand EARLIER than peak cylinder demand is typically encountered @75/80 degrees ATDC.   The trick is to tune the combination to take maximum advantage of this.   Again, simulations & modeling can help here.   Reducing the overlap, anyway you can, helps alleviate a bad reversion condition.    On hot street/street engines, prevention of reversion should be the focus.

There will be some small effect from the thinner atmosphere of high altitude, mostly lessening the V/E of the engine, perhaps some effects on the gas speeds.   That is why lots of land speed vehicles are blown or turboed.   But if you are running naturally aspirated, the air is the air, and you can't do much about it, EXCEPT, plan for it, AND, take advantage of the lower V/E.   Rejetting the carb will be essential.   Static C/R will of course, remain the same, regardless of altitude.   BUT, Dynamic C/R can be manipulated to take advantage of the lowered V/E.   85% density x 90% V/E x 13/1 C/R = 9.945/1...................     Stay tuned, I intend to model this.   Whether Midget's engine can take advantage of any changes the modeling suggests, remains to be seen.  However, I believe that right now, there is room to improve engine performance significantly, and have an engine that will work in Utah & North Carolina.   Like I said, stay tuned........

Best regards & 
MB

[Milwaukee Midget]

FB - and all -

Okay, I'll post them here so we'll have a permenant record of the numbers -
Spring sets - post juggling -

open - seat
272 - 88
275 - 90
275 - 91
270 - 86
278 - 91
270 - 89
270 - 85
274 - 90

The open is actual pairs @ .960 + .075 retainer height - checked with retainer in place.
Seat is calculated by adding sum of pairs - time constraints forced that one.
Inner springs calculated at inner keeper height - 1.41 - .91

Still a couple of outliers, but gut level, I'm thinking they're usable.

Mocked up the valves in the head with the old inner springs.

Received the 1.25 rockers today - putting them to soak overnight.  Tips are a little worn, but then so am I.   

[fordboy628]

Midget,

Very useable & huge improvement over previous valve springs.   I'll see you tomorrow.

F/B

[Milwaukee Midget]

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"

I'm trying to find a cam with a Lobe Center Angle that wide that isn't intended for a Morris Minor Panel Van with an automatic.  Seems awfully wide - the Leyland street grinds are all at 107.5, their race stuff tightens up to 102.5.  Mine, being a scatter pattern, is 105.5 for pistons 1 and 4, and 102.5 for pistons 2 and 3.

I guess I need to find out if this is even an option, short of a custom grind.  I'll be out in the woods with my flashlight . . .

FB - when I get those numbers, I'll forward them to you for modeling.

Andy - good hearing from you again.  It's getting interesting over here. 

[Milwaukee Midget]

We set 21 class records with 2 EXP/LN7 based cars and were sandbagging about 10%.

I remember reading the article in Car and Driver on the EXP.  I seem to recall Fiat connecting rods, and a slew of other whacky parts change outs in that engine.  Good to see it continued to be competitive.