My 1995 Caterham S3 X-Flow Emotional Support Vehicle "Beater" refresh and other journeys down the rabbit hole

[MV8]

Might be a good time to check the vac adv for leaks and hand pump to see how far it rotates the breaker plate on the base plate, clean and lube the fly weights and springs, then checking how far it is set to rotate and how easily against spring pressure. Note, the degrees of movement at the distributor will be half the degrees at the crank. A protractor and divider are handy for checking.

 

I'm thinking this is a pre-ported vac design ignition so full manifold vacuum, pinched off for setting initial timing, fly weight tension enough to stay pulled in fully at idle but however far they are pulled in, rotation of the distributor compensates at the expense of total timing (inital plus fly weights only. Vac is it's own system).

 

These electronic systems are no replacement for vac adv unless they have a map sensor and a shunt to lock it out like older oem efi systems.

Edited September 22, 2022 by MV8

[IamScotticus]

On 9/18/2022 at 7:58 PM, ashyers said:

 it screws up the jetting.

Yea  you're right.  the jetting is based on the chokes in place and working.  If Im a carb guru swapping tubes and jets, etc, I could dial it in.  Which I still may need to do with my A2 cam profile. 

[IamScotticus]

Steve,

sage dizzy advice that will gi into my dizzy notes.

But looking for the context here...🤔

Are you saying that I need to go back to points & vac with this carb?  My current dizzy is an Aldon setup for DCOE 40s and A2 cam, no vac.

A detail I hadn't noticed till now, the manifold the carb was attached to, for a Cortina GT/E, doesn't have a vacuum nipple, or an obvious port on the carb.

🧐

Edited September 22, 2022 by IamScotticus

[MV8]

No, I'm saying it is better for an ignition system to include manifold pressure when adjusting timing, just like oem efi  and carb systems. Most stand-alone ignitions do not. It's just another thing to consider.

Some electronic ignition systems are a drop in replacement for the points but still a fly weight and vac adv (if installed) system.

Some lock the flyweight and vac adv or use a distributor from an efi application that has no fly weights or vac adv, set the total timing by rotating the distributor body, then retard electronically based on rpm input.

The mid-60s and older vac adv used manifold vacuum, which could be a port (not "ported" vac but full vac at idle) on the carb or directly on the manifold. Closed throttle=max vac adv, full throttle= zero. Completely separate system from the fly weights. Fly wts act on the shaft. Vac adv acts on the breaker plate.

[MV8]

A pretty good explanation imho: https://www.motortrend.com/how-to/1607-tune-your-vacuum-advance-for-better-drivability/

[IamScotticus]

Steve, youre about to make me a points man.  I'll never touch a data cable again.🤓

My last laptop was 2004.

But youre right, separating ignition curve from actual curve can be problematic.

Someone has the clever idea of relocating the condenser back to the scuttle for swapping out different values.

[MV8]

I'm definitely not a points man. I was a diehard XP fan until it was total incompatible for web use.

I prefer an oem type distributor with vac and fly wt. If there is no direct fit oem electronic application to retrofit, I would use a drop in point conversion retaining the fly and vac. Here is a pic of the internals on my chinese mopar distributor. The china vac adv was junk/leaking, breaker plate clip broken in three pieces, with rust everywhere and no grease (mostly cleaned up in pic for clear coat and grease). My point in sharing is the simplicity. I used a $10, 70's chevy HEI distributor internal 4 pin module/amplifier on a chunk of aluminum as a heat sink.

If I were trying to make the most of sidedraught with no common manifold across the cylinders to provide vacuum, I'd drill the boss built into each carb manifold to press in a 1/8 brass or steel tube for a vacuum port, tee them together and connect to the vac adv. I've not seen any lotus dual sidedraught intakes that did not have the prevision cast into the manifold on one runner of each manifold. The vacuum tubes are available with a bead from companies that repair carburetors (see link) or one could buy tube stock from a company like mcmaster and turn as needed for a light press fit based on the hole made by the drill size and/or use a retaining compound (maybe have a machine shop do it). Rotary file the inside of the runner if the tube protrudes.

Another option would be a 1/4 thick shim base for the carbs that has a port, so no mods but the carbs would stick out another 1/4 inch plus an extra gasket.

One could completely hide the ports by drilling the bottom but then fuel could leak into the vac adv when not running.

[IamScotticus]

I will be starting from scratch on sourcing an Xflow dizzy.  Lucas and Bosch seem to be most common.   And one might think between the two, the Prince of Darkness would get the pass, but then maybe not.  I now have to take Dizzy 101 and see what the Formula Ford and Escort boys are using.

Im already setting rocker gaps  I might as well set points gaps too.

I will have a E-bomb proof car for sure.

[SENC]

Give Martin Jay at Distributor Doctor a call, I'll bet he can build one up to the spec you need.  Then keep a couple extra sets of good points, condensers, and rotors and you're set.  They really don't fail often with good parts, and are so much simpler to dx and rx problems.  Build up a backup dizzy to have in your travel kit and if you have an issue you can swap quickly and save evaluation and points/condenser replacement for the bench.

[NSXguy]

i just installed a new petronix system on my car, set timing, with new gapped plugs, retuned carbs and my car has never ran stronger. Even better than when i purchased it. 

The petronix is pretty straight forward to install from Pegasus racing. 

 

Edited September 24, 2022 by NSXguy

[IamScotticus]

Im wondering if the Aldon I have now will play well with a downdraught carb?

Perhaps the Aldon is something I should try before committing to a vac dizzy?

[MV8]

The carb type is not a factor. The right answer is whatever you want to do. Good enough is just that. This is not a race.

[SENC]

Agree.  Also not sure why a vacuum dizzy is of interest, unless you're going for fuel economy or focused on meeting certain emissions objectives.

[MV8]

If you'd like more info, check out the motortrend link posted above.

I don't think ford originally installed vac adv on the kent for emissions or mpg. Chapman decided not to connect it for whatever reason. Ported vacuum instead of full manifold vacuum to a vac adv is the result of emissions compliance. Running more advance (without pinging) is a driveability improvement up to a point.

[IamScotticus]

My sluthing today pretty much confirmed that the Aldon and Petronix "are" the same company.  Same tech, same failures.  Still looking into it.

Still very interested in learning my way around a points dizzy.

It just seems like it's something a guy should be able to do. 

So, what's your dwell angle?

Edited September 27, 2022 by IamScotticus

[MV8]

Dwell is how long the points can stay closed to charge the coil primary. With a fixed cam and point design, the dwell is determined by the point gap setting. The feeler should barely drag when perfectly square to the point surfaces and the points transfer material from each other in use that can be filed off and the gap reset for more life.

 

 

[SENC]

Good article, MV8 - it still looks to me to be mostly an efficiency/fuel saving device though I can see that there could be some performance gains in engines with long duration cams.  You have more experience and knowledge about these than I do - as cams get "wilder" don't we lose vacuum, so counteracting that benefit a bit?  Or am I misunderstanding?

 

@IamScotticus you can find meters that just measure dwell, or many multimeters either measure dwell or its inverse - so if you have a good MM check it for function before buying a new tool.  I find it extremely useful.  As MV8 said, using the feeler gauge and getting a prescribed gap should cause the right dwell to result - but checking dwell directly is confirmation.  Surely user-error, but I often find I get close but sometimes just outside the desired dwell range with my feeler gauge - so with a meter I can adjust and get it right.  This can affect performance - to short a dwell and the coil doesn't get full charge, too long a dwell and you've impacted timing.  As I recall my twin cam and pre-crossflow engines both want 60 degrees of dwell, plus or minus 3 degrees, so suspect crossflow is similar if not the same.

[IamScotticus]

one of the complaints I read about the electronic hall efect  dizzys, like the Aldon, is that the rotor can stop at a trigger position thus sending a continuous charge to the coil, until the engine is turned.

Is this a situation a mechanical points can have also?

[MV8]

7 hours ago, SENC said:

Good article, MV8 - it still looks to me to be mostly an efficiency/fuel saving device though I can see that there could be some performance gains in engines with long duration cams.  You have more experience and knowledge about these than I do - as cams get "wilder" don't we lose vacuum, so counteracting that benefit a bit?  Or am I misunderstanding?

 

@IamScotticus you can find meters that just measure dwell, or many multimeters either measure dwell or its inverse - so if you have a good MM check it for function before buying a new tool.  I find it extremely useful.  As MV8 said, using the feeler gauge and getting a prescribed gap should cause the right dwell to result - but checking dwell directly is confirmation.  Surely user-error, but I often find I get close but sometimes just outside the desired dwell range with my feeler gauge - so with a meter I can adjust and get it right.  This can affect performance - to short a dwell and the coil doesn't get full charge, too long a dwell and you've impacted timing.  As I recall my twin cam and pre-crossflow engines both want 60 degrees of dwell, plus or minus 3 degrees, so suspect crossflow is similar if not the same.

Cams with more overlap (where intake and exhaust valves are partially open) have numerically lower manifold vacuum at idle with the same compression ratio. Timing advance increases vacuum for any cam spec. Too much advance and the engine will stall with any load, surge, or ping so like any timing curve, it is something that needs to be dialed in by controlling the total (limiting the travel at the plate or the can) and adjusting the preload to control at what level of vac it starts.

 

More vac, more port velocity is available, carbs are more responsive, etc.

 

 

[MV8]

1 hour ago, IamScotticus said:

one of the complaints I read about the electronic hall efect  dizzys, like the Aldon, is that the rotor can stop at a trigger position thus sending a continuous charge to the coil, until the engine is turned.

Is this a situation a mechanical points can have also?

The same could be said of any ignition system that is left connected to the battery. Power should always be controlled by the key for the coil and the trigger. If it were not, the engine would never stop. Alternators that have been mis-wired can back feed the system so when the key is off, the engine continues to run off alternator output.