4K Dizzy Questions

[brownevan]

hey everybody;

 

I have a starlet kp61 here in the states with the 4k-c motor; and the previous owner sent me a broken electric dizzy (the aluminum mounting plate is snapped). i was wondering if i could run the electronic dizzy guts in my stock 4k distributor; as my 4k has the vaccum lines plugged and it's cammed.

 

i'm getting what i believe to be some pretty retarded timing below 3000rpm. i've heard the electric dizzy will smooth these 4k's out quite a bit, and i'd love to make use of the ever hard to find electric dizzy guts here in the usa. thanks!

[altezzaclub]

I fitted an electronic one (also had a broken clamp) and found the advance curve was very slow under 3000rpm. I eventually found springs to give a decent avance under thse revs and it is great. That was off a 5K, so your KP61 dizzy might be much better or you might have to recurve it too. There might be mechanical problems inside your current one, it should advance well.

 

I don't think the vac lines will do anything for your motor, its an emissions control thing, providing you can pass any emission tests you have to.

 

As far as I know the housings are interchangeable, its mentioned in there, but nothing else is. The only way to see what you're getting is to generate an advance curve with a timing light and compare your mechanical one to the electronic one.

 

http://www.rollaclub.com/board/topic/42407-the-girls-ke70/

[rian]

I've have had the 5K electronic distributor that Altezzclub mentioned, the 4K-U electronic distributor that you have Evan, and the standard 4K-C points distributor all in the same 4K at different times.

The 5K electronic distributor is absolute rubbish in a 4K, you're much better off with the original 4K-C distributor unless you do what Altezzaclub did and recurve it.

The 4K-U electronic distributor is good, I can't tell if the engine is running better or not but it is great to never have to adjust the points. Plus you can run a 12 volt coil and ditch the stock 6 volt/9 volt/whatever coil and shitty ballast resistor.

As for putting the electronic distributor internals in a points distributor casing, I never tried. But I think my points distributor was a Bosch unit and the electronic one was a Nippon Denso so it probably wouldn't have worked anyway.

[brownevan]

So I got my car back from the shop and they had ran a vaccum line to the side port on the dizzy from the carb; but i was doing some investigating and realized there was very, very little vaccum from the carb, and barely any change in idle when i pulled it. I was investigating the vaccum ports on the intake manifold, and the one on the upper left of the three was providing tons of vaccum, so i plugged it into the dizzy (same side hole on the dizzy) and it began to idle smoother immediately. i noticed a much higher level of smoothness when driving under 3k, and lots more coast when i let my foot off the gas in the low rpm range.

 

is it possible that I advanced the timing curve too much by doing this and not re-setting the timing? last thing i want is detonation on a new top end rebuild; and the car doesn't shut off quite as happily as it did before i did this.

 

thoughts?

Edited January 28, 2013 by brownevan

[altezzaclub]

If you haven't got a timing light, go buy one. You'll need it all your life. Set idle timing to 10deg and generate an advance curve as I did.

 

They connected it to 'ported' vacuum, which is non-existent at idle, and you connected it to manifold vacuum, which is at its maximum at idle. They react differently to throttle position and engine speed, but I don't know which is better.

 

Manifold vac will add something like 10deg of advance at idle, so you're idling at 18deg advance, which should have increased the idle speed noticeably, but as it collapses the moment you open the throttle it won't cause pre-ignition. You should hear it detonating under power anyway.

 

I'm sure you're using 95 or 98 octane fuel...

[brownevan]

i figured as much; that the advance change wouldn't cause preignition due to being overridden by the mechanical advance when the engine's really working.

 

I have heard of 4k owners using the ported vaccum, the manifold vaccum, k series electric dizzy, and no advance whatsoever; I still haven't really discovered the tried and true way to set the ignition without breaking the bank.

 

It appears that my starlet prefers the manifold vaccum for whatever reason; the idle lumpier when it's ran from the carb, but also well below 1000 rpm off the manifold, and the advance curve just feels more stable and less restricted when run off the manifold.

 

so it did boost the idle a fair bit; my engine is cammed and I usually run premium octane (highest octane fuel available at the pump here in the usa), not sure of the exact rating. i'll catch that the next time i fill up.

 

that sort of leads me into the next question; I just had a 1500$ top end rebuild done on my engine (burned valve), and when i get the car back, i'm getting some quiet but audible tappet noise if i give it hard throttle. were the mechanics just lazy in doing an adjustment? I'm no 4k expert (my corolla has a 2tc, and this is my first k motor), but I'm figuring that can be adjusted out somehow, and how will the ITB's i've got hidden away at home interact with the dizzy, and tappet noise?

 

One other thing: does the port which you run the vaccum to on the dizzy matter? the mechanic told me that it was advancing too far through the outer port; but that seems to be the preferred one, and he advised me to use the side port and plug the other.

Edited January 28, 2013 by brownevan

[altezzaclub]

i'm getting some quiet but audible tappet noise if i give it hard throttle.

 

If it is tappet noise it should be audible at idle. If it is pinking from pre-ignition it will be audible under hard acceleration, especially at low revs. It will vanish the moment you ease up on the accelerator. So if you can't hear the tappet at idle or maybe 1000-1500 revs in neutral, maybe it is advancing too fast and pinking.

 

I have a noisy tappet, not loud but annoying, and I've tried all sorts to get rid of it. I'm sure the rocker has a groove worn in it from the valve, and the feeler gauge bridges the groove to give it too large a gap. So unless you have the rockers re-surfaced on a grinder it is always likely you will end up with tappet noise sooner or later.

 

Swap over between ported and manifold vacuums and see if it affects the tapping noise. Even take a few degrees off the ignition advance and see if that stops it. From what I understand America has low octane fuel compared to Europe & Japan, but they must have something good over there for all the Ferraris.

 

The iTBs will add to pinking woes if they do breath better than the stock setup, so you might have to re-tune it all then. That only means resetting the timing once you have the mixture set correctly. Are you going to run fuel injection or quad carbs??

[brownevan]

If it is pinking from pre-ignition it will be audible under hard acceleration, especially at low revs. It will vanish the moment you ease up on the accelerator. So if you can't hear the tappet at idle or maybe 1000-1500 revs in neutral, maybe it is advancing too fast and pinking.

 

that's exactly what's going on. is this something i should worry about?

[altezzaclub]

yes, you need to either slow the advance curve or reduce the mechanical advance at idle. Octane booster would be another solution, maybe try a bottle and see if it stops it.

Get a timing light onto it and get some real readings to work with. I'd be interested to see how much the advance drops off as you open the throttle and lose that manifold vacuum.

 

..and at least you know its got good compression with that head job!