Setting Timing

[Large Arbor]

Ah, I see. I am a little slowwwww.. I will look for leaks but the TA-31 really sealed things up tight. I will check the carb fittings.

Thanks for the advice gents. I love this site. Learning so much.

Phil

[RACERAL]

If the both rocker arms are in the UP positon and the piston is up. Isn't that TDC on compression.

[1795]

At the end of the exhaust stroke, just prior to the intake valve opening to allow the fuel mixture in both valves will be closed. Otherwise, if the exhaust valve remains open some of the fuel mixture will get sucked out the exhaust lave. In addition, if the exhaust valve were not closed at the end of the exhaust store, Mr. piston says hi to Mr. valve in a very unkind way.

[Large Arbor]

Ok, one more question in this thread. Since setting the timing to38 degrees at 4,000 rpm (it gets to 38 at 3,000 rpm and stays there) it does not seem like the engine de-accelerates very fast. The RPMs seem to stay there even with the throttle released. Accelerating up is no issue, but I would like to tone down the idle a bit and cannot seem to do that. It wants to idle at 1100 RPM. I am using the same size bushings on the distributor as before and the heavy silver springs. Attached below is the MSD chart that shows the settings.

Phil

[blykins]

Make sure you don't have a vacuum leak or the throttle isn't sticking/hanging up.

[Large Arbor]

Thank Brent. I have checked both and cannot find any vacuum leaks or throttle sticking. I can push the throttle all they way back and the RPMs stay up. If I adjust the idle speed down it eventually stalls.

Phil

[Large Arbor]

I have the choke setting wide open. Would that make a difference?

[Bernica]

Originally Posted by blykins

Make sure you don't have a vacuum leak or the throttle isn't sticking/hanging up.

I agree with Brent and know he probably won't agree with the technique I described before, but with everything in running order and at idle, take a can of starter fluid and give short squirts around the carb and manifold. If you hear an RPM change, you have a vacuum leak.
My 2 cents...

[Tom Kirkham]

MSD loads up their distributors with their most conservative advance curve. In a lightweight Cobra you can run a much more aggressive advance curve. If you speed up your advance curve (a factory Ford 427 distributor was all in at 2,400 RPM) and run more base timing at idle, your engine will run a lot better (throttle response, lower under hood temperatures, etc). I have been very happy with running the most aggressive advance curve.

[DanEC]

Originally Posted by Large Arbor

I can push the throttle all they way back and the RPMs stay up. If I adjust the idle speed down it eventually stalls.

Phil

Phil - I'm not sure of what you are saying. Adjust the idle speed down far enough and eventually all engine will stall at some point. What engine speed is your engine stalling at? Even with a pretty aggressive cam it should be able to idle down to about 650 or 700 although it might not be a great idle. I'm guessing somewhere around 900 or maybe a bit more might be in the ballpark for your engine.

Originally Posted by Large Arbor

I have the choke setting wide open. Would that make a difference?

If the engine is warmed up the choke blade should be wide open. That's what you want. It shouldn't cause your engine speed to hang up there. You might check the progressive linkage on the passenger side of the carbs for any binding or hanging.

[Dominik]

Thanks Tom, I liked to add a similar comment:
You want to make sure your engine does not run too retarded at idle, which will cause the headers to glow red in minutes!

Set your total advance first, but use an advance curve which allows around 16 deg at idle, if your starter can manage. I found 16 deg perfect, 20 deg too much (depending on cam).

Then soften the advance springs to get the total advance all in fast. Don't know what fuel you guys can get there and how fast your engine goes through the rpm range (short diff ratio?)

Best you do that on a dyno... This method can cause a piston to hole quickly if you don't know what you are doing!

Above applies for point distributor. I don't know if MSD has programmable ignition curve. I am also a bit concered about the corrosion under your cap...

[Large Arbor]

I have the non-point MSD distributor. Spring choice sets the advance so Mr. Kirkham's comment seems dead on. I think I will start the car up, let it warm up, shut off and switch springs to see how that affects idle. If no effect then I go back to the original springs and go Danno's route. Got lots of things to try that's for sure. Will not likely get to it till this weekend.

Phil

[Jaydee]

Springs aren't going to effect any advance at idle. Springs will only effect how quickly the advance comes in as you increase the rpm. There should be a small hole on the side where you line up a tag which you can bend to limit the amount of advance. The only way to accurately find 0 tdc is with a adapter screwed into the plug hole. It's easy enough to make your own. Take out the center of an old plug and weld in a stud. Screw it into no 1 plug and rotate the engine until it stops, and mark the balancer, rotate engine anti clockwise until it hits the piston, and mark it again. Then exactly halfway between the 2 is tdc..
Then center punch the balancer. Marking the timing marks with a liquid paper correction pen will make it easier to see the marks with a timing light.
JD

[Large Arbor]

I did find a lock washer off the rear quad vacuum pump. I rigged a temporary key up and started it up and things seemed more stable. I am idling between 1000 and 1100 rpm. I will toy with mixtures a little bit as the exhaust is a little eye burning in the garage. Pic is shown below.

Phil

[rodneym]

Large Arbor, any reason why your hairpin cotter is installed like that?

[Bernica]

Originally Posted by rodneym

Large Arbor, any reason why your hairpin cotter is installed like that?

I thought same thing. Maybe use a circlip instead?

[patrickt]

Originally Posted by Bernica

Maybe use a circlip instead?

That's what's on mine. They are very small and EXTREMELY easy to drop and lose. I would bet someone, in a distant past, dropped the original half-moon clip that was originally on there and replaced it with the hairpin.

[rodneym]

At first glance it looks like the crook is in the hole, to me anyways.
E-ring is the way to go.

[rodneym]

How about a double sided hairpin?

[patrickt]

Originally Posted by rodneym

At first glance it looks like the crook is in the hole, to me anyways.
E-ring is the way to go.

There is no hole in that shaft. There's a pic of mine in this thread from two and a half years ago when I put on the adjustable vac secondary gizmo.
Theoretical Vacuum Secondary Question