Starlet 4K Vaccum Advance Questions. Helppp :)

[brownevan]

Hey everyone.

 

So after my KP burned a valve less than 200 miles after purchasing it, I immediately sent the car into the shop for a new top end rebuild, new valves, gaskets, and to check out the engine, etc... from my recent purchase.

 

Well, the starlet's previous owners have done quite a few good and bad things to the car:

 

flares

strut bar

cam

2 inch exhaust

the cheapest gauges possible

 

all vaccum systems were indiscriminately ripped out and plugged

 

no heater.

 

and i'm not exactly sure what all he removed; not being a 4k expert. the shop i took it to did a good rebuild and adjustment, i'm sure, but when i went to go check on the car they hadn't touched the vaccum system, and sort of acted as if they didn't want to go there.....

 

this was a performance shop that i assumed could make easy work of an old system like this...

 

so that leads me to my question. what vaccum lines are required to run the dizzy to get proper ignition while cruising and at low rpm???

 

thanks in advance, and if any of you can help me, it will be a sigh of relief.

[GJM85]

One hose that runs from the carb to the dizzy. It should be here...

[altezzaclub]

Time to get a carb to match the cam and extractors I'd say- Weber 32/36 downdraught or even better, a Weber DCOE or SUs.

[brownevan]

Time to get a carb to match the cam and extractors I'd say- Weber 32/36 downdraught or even better, a Weber DCOE or SUs.

 

Funny you mention it :) I've got some CBR900RR sidedraught carbs waiting to go on the K motor; I just need a mani for them and don't have any resources for that out here in oregon without getting charged an arm and a leg. i bet one of you guys down under could get one to me almost as easily...

[brownevan]

One hose that runs from the carb to the dizzy. It should be here...

 

Is this the only line that the dizzy needs for ignition timing? it seems insane that i would get a grand worth of work done to my motor and they wouldn't consider connecting that single little piece of tube.

 

would someone explain to me a little in detail the 4k vaccum system? just so i'm not so in the dark; i'm an amateur wrench, tryin my best :)

 

thanks for all the feedback guys.

Edited January 13, 2013 by brownevan

[GJM85]

Basically, the distributor has a function known as vacuum advance. It's used to advance the timing of the engine between low to mid range load increasing low speed drive ability.

It uses ported vacuum sourced from just above the throttle butterfly. The effect of the vac advance diminishes as engine speed increases as the low pressure zone in the carb moves from the throttle plate to the main venturi.

This is where the mechanical advance of the distributor takes over.

[altezzaclub]

I've got some CBR900RR sidedraught carbs waiting to go on the K motor;

Nice! You should be able to have a steel manifold welded up for a couple of hundred bucks. Just cut the port shapes out of a bit of plate and weld stub pipes on as needed.

[brownevan]

Thanks guys. when i pick up the car on monday i'll let you know how it goes!

[TRD ke70]

If you get stuck with the vacumn system, i have a US starlet workshop manual, has everything in it and i use to own a KP60.

[brownevan]

So, I picked up the car today; and the mechanic said he tried to run the vaccum advance straight from the throttle body and it didn't work. he claims i need an electronic or centrifugal ignition; is that true? what am i missing? i just got a 4k back with 0 miles on a top end rebuild, and the car feels like a wet fart below 3250, and rips hard at 3500-5000.

[brownevan]

not to mention after a valve job; i still have tons of lash! is that because of ignition timing?

 

and pardon my naivete, but i see two vaccum ports sticking out of the side of the dizzy; which one do i use to connect the carb, and which do i block? i heard there's a "secondary" vaccum line that's very important, and the charcoal canister as well?

Edited January 15, 2013 by brownevan

[brownevan]

i found this online on kp61 forum: i hooked it up exactly this way and it seems to improve my low rpm acceleration a bit, but the ignition timing is still off i think....

 

[altezzaclub]

i still have tons of lash!

I assume that is tappet gap?? Simple to adjust yourself, maybe the mechanic didn't know what 4Ks were meant to have.

 

I reckon close off all the vac ports and get the car running correctly, then start adding them in one by one. None of them are important.

 

If the points and timing are correct, it will run fine without a vac advance. I hooked up the vac advance and the charcoal canister and blocked everything else, but it was a few years back and I've changed to SUs so I can't check which ports I used.

[brownevan]

at low rpm, if i step on the gas, it's quite boggy compared to my stock 2tc, and then right at 2750 it picks up. could this just be my lumpy cam on a stock carb? i really need to get those sidedrafts on there......

[altezzaclub]

Could be, depends on the cam and its timing. If its a "3500-7500" sort you might have to live with the bottom end.

 

Get the quads on and start chasing it, you don't want to spend ages and money sorting this problem only to do it again when you change carbs.

 

Can you get an air-fuel reading down low? See if it is lean. No chance of the cam timing being advanced a tooth?? That makes it all up top. How about pulling the ignition timing back a few degree to help it low down.