Milesmor Ford Timing Unit

[Lynn Eades]

Tony, that was a very interesting post.
I think the timing jig is as much to set the dwell of the two sets of points as it is to time the dizzy, but as you say (once the dwell is sorted) then a timing light would be best. I have a timing jig but have not yet put it to use.
The only way to sort out TDC is to measure a given piston height before TDC and the same after TDC, marking both accurately and dividing it.
Dodge put a screw in plug in the cylinder head, so that you could put a rod down to the piston. Henry didn't feel the need.
My son in law has built a couple of Megasquirts. These fine bits of technology allow you to control all manner of engine functions by dialing up what is required on your laptop as you drive along.
It allows you to map the timing the fuel mix, max revs,close it down if it overheats, idle up, anything you can think of, in much the same way as F1 (well maybe a few years behind)
Anyhow it allows you to set up an advance curve which is controlled by the Megasquirt essentially deleting the need for a mechanical centrifugal advance mechanism.
It is aimed at a fuel injection set up, but could run just the spark side of things.
Just imagine running your flathead V8 with fuel injection via an injector/ sparkplug, using the carb for the control of airflow only.

[Tony Wheeler]

Originally Posted by Lynn Eades

The only way to sort out TDC is to measure a given piston height before TDC and the same after TDC, marking both accurately and dividing it.
Dodge put a screw in plug in the cylinder head, so that you could put a rod down to the piston. Henry didn't feel the need.

Yes that's certainly the ideal method Lynn, but Henry made things difficult for us in more ways than one! Not only did he give us no access plug like the far more considerate Dodge brothers, he also offset the crankshaft! One of the peculiarities of the flathead is that the crankshaft is not directly in line with the cylinder bores, it's offset towards the right bank by about 1/4". It's a clever idea which effectively increases the stroke momentarily when it's most useful, ie. during the power stroke to generate more torque, while at the same time reducing piston sidewall force when it's at its greatest. Of course, just like a stroked motor it can only be taken so far, before the conrods start hitting the bottom of the cylinder wall. What this offset crank means for us is that the piston height differs between the upstroke and the downstroke, for example it's almost 1/4" lower at 90 degrees BTDC than it is at 90 degrees ATDC. Which means that when we mark the crankshaft pulley with the piston at the same height before and after TDC, then bisect the two marks, we end up with a false TDC. Once again this is something all the so called flathead experts never bother to warn us about! Fortunately it's quite easily compensated for, by simply moving the TDC mark 1.5 degrees clockwise.

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Funny you should mention the access plug in the Dodge head Lynn, it's something I gave serious consideration to on one of my tired old flatheads. The plan was to drill a 1/8" hole through the head, missing the water jacket of course, so I could use a bit of 1/8" high tensile rod to gauge piston height. It's a highly accurate method when used around 90 degrees from TDC, because the piston moves 66 thou per degree either side. That's about 1/16" which is easily detectable by eye, which means that when you factor in the 1.5 degree offset your TDC mark will be accurate to well within one degree. The next step was to correlate TDC with the timing gear marks, so I wouldn't have to drill holes in all my motors! The guinea pig motor could then be plugged with a bit of oversize rod hammered in the head, which could be weld repaired if the motor ever got rebuilt. In the end though I thought I'd try the volumetric method first, and it proved to be highly accurate, although quite tricky to use. The problem is you have to work near TDC itself, where the piston only moves 1 thou per degree either side, and only 4 thou at 2 degrees, and 8 thou at 3 degrees. It's easy enough to detect with this method, because it amplifies piston movement by a factor of nearly 200, but there's a "dead spot" either side of TDC where the piston doesn't move at all for several degrees, owing to crankpin and piston pin clearance. That means you have to turn the crank incrementally both ways to mark the dead spot and then bisect the two marks. There's gotta be an easier way!

[Tony Wheeler]

Originally Posted by Lynn Eades

I think the timing jig is as much to set the dwell of the two sets of points as it is to time the dizzy, but as you say (once the dwell is sorted) then a timing light would be best. I have a timing jig but have not yet put it to use.

Yes I believe you can read the dwell on the timing jig Lynn, but it's determined by the points gap, so if you set them to the recommended 14-16 thou the dwell will be correct. In practice however the dwell is not that critical, esp. with a modern coil. The old coils weren't nearly as efficient, and the idea of the twin point dizzy was to maximize dwell to improve coil performance. Basically it gives the coil a bit longer to charge up between sparks. Evidently coil technology had improved by '49 because the 8BA ran a single point dizzy, which by definition provides much shorter dwell.

Something else they did on the 8BA dizzy was get rid of the centrifugal advance system and replace it with a vacuum advance system, and quite an ingenious one at that. Gone are the flyweights used in the old dizzy, to be replaced by a vacuum diaphragm which runs off not one but two vacuum lines. One supplies manifold vacuum which advances the timing when the manifold pressure drops as the revs increase, while a separate line supplies venturi vacuum for load compensation. The two work together to provide a smooth graduated timing advance which is highly responsive to throttle changes throughout the full rpm range. As opposed to the old flyweights, which appear to be fully advanced at only 1500 rpm or thereabouts, as seen under the timing light, and the ON/OFF vacuum piston brake which only kicks in under load, and only retards the timing by about 5 degrees. It's far from ideal, and while it may only cost a few horsepower under full load, it would certainly cost in fuel efficiency at less than full load. There may well be a couple of mpg to be gained simply through improved spark timing, which is where your mapping idea becomes rather interesting Lynn. Or you could go the whole hog as you say and stick some injector plugs in, or even just a single point system in the throttle body, either of which would be quite easy and wouldn't detract drastically from original appearance. Who knows, we could be getting 15 mpg on the highway! When you consider the phenomenal improvement in fuel efficiency achieved in cars over the past 50 years, it's not entirely inconceivable.

[Lynn Eades]

Hi Tony, I did not take on board the significance of what Henry had done with his offset, until you pointed it out. You are obviously a clever bugger.
I have though, only ever heard bad stuff about the 8BA dizzy. It was probably related to the dwell/soak time required by the old coils (another thing that I had no idea about) You have shed a different light on a few areas.
I do still like the idea of being able to bypass the mechanical advance mechanism. My carrier will likely not look 100% correct under the covers.

[Tony Wheeler]

Lynn, I believe most if not all 8BA dizzy complaints arise from having changed the carby, or fitted multiple carbies. This eliminates the venturi vacuum system which is built into the original carby, leaving only manifold vacuum to control the diaphragm. The two systems were designed to work in tandem, so if the venturi vacuum is disconnected, or split across more than one carby, the dizzy needs to be completely recalibrated. I suspect this is not well understood amongst rodders and often gets overlooked, so the dizzy itself gets blamed. Which is hardly surprising as it's radically different from the earlier vaccum system on the crab, which can be disconnected without noticeable effect.

[Grant Bowker]

A Milesmor timing setup has appeared on ebay, see the for sale list area. http://www.mapleleafup.net/forums/sh...253#post193253

[barrie edge]

i am no judge but there could be some imfo here http://www.flatheadv8.org/rumblest/ignition.pdf comes from here http://www.flatheadv8.org/rumblest/intro.htm bj

[Lynn Eades]

Tony W. in post #7 you talked about the difficulty of finding TDC because of the offset of the crank. It seems that what you do is put pistons #2 and #3, exactly the same distance (up or down) their bores and you are right on TDC, #1. (and for no reason that is important here,#4 cyl. happens to be at BDC) (from page 204 of Pages book, Ford V8 Cars and Trucks 1952) A very good old book.
This just saves you having to work out the 1.5 degrees on the pulley.

I have made a bracket that straddles the two lower timing cover bolts from light angle iron. Unfortunately I did this without reading your post #7, and will have to revisit the marking of TDC.
Fortunately I have not yet fitted the heads.