mixture adjustment for 170

[falcondave63]

i'm trying to get the mixture set correctly on my 63 Falcon with a 170. whats the correct method for the on car adjustment for the mixture setting?

 

[addo]

Set your base timing at idle speed. Warm that motor up until the thermostat is open. Choke (if fitted) should be fully off. If it's automatic choked, make sure the choke's open all the way. Remove the air cleaner assembly.

Adjust the hot idle screw (or idle screw if it has a manual choke) until the idle speed is dead on textbook. Think it's 525RPM with a manual trans. When doing all this, have the radio operating, and the headlights on high beam, and the demister fan blowing.

These are important because electrical demand slows down the motor by increased generator load, and your "worst case scenario" would be not having enough idle RPM on a cold rainy night...

Double check that base timing again. If it's correct then you move onto the mixture. Screw the needle in until the RPMs increase, kep going until they start to decrease. Get back to the last steady point and adjust your idle screw again.

You will find it's several iterations of this exercise; screw in the mixture needle until the idle falters, back out a touch for stable idle, then adjust the idle speed screw... Eventually it will be balanced. Now with the motor running, refit the air cleaner assembly. A measurable rise of RPM means your filter is obstructing flow significantly.

Shut off the electrical accessories and idle will jump a little. That's what you want.

Cheers, Adam.

 

[falcondave63]

Adam, thanks a ton!! the carb has a manual choke. i'll try and give your advice a whirl tomorrow. almost forgot, what is the timing supposed to be?

 

[addo]

I don't remember offhand. With the vacuum plugged at carb, probably 6° by factory but you could well find 10° works just as well.

 

[falcondave63]

well, i'll check it out today. i'll put my timing light on it and see what i come up with. any suggestions as to the procedeure for checking the timing?

 

[addo]

You need to set the timing at idle speed.

It doesn't matter if the mixture is right or wrong, just that speed is correct. The vacuum line fitting on your carb needs unscrewing and you temporarily seal it with duct tape at the carb - steel line itself doesn't need plugging.

Factory advance says 4° - but try eight.

 

[bigcatchdaniel555]

i just put in a carter rbs carb from a 72 250 on my 66 200 the motor runs perfect however should i adjust the float or should it already be at the right level

 

[addo]

You know the old saying! "If it ain't broke..."

 

[falcondave63]

oh, its broke. i cant get it to run right. its bucking and at times backfiring through the carb. i wasn't able to check the timing. i cant find a notch on the crank pulley...i'm frustrated at this point...

 

[Bort62]

Go down, find the notch with your finger (not running) and mark it with white-out or something easily visible.

 

[falcondave63]

thanks! i'll feel around the crank pulley and see if i can find the notch. when i do i'll hit it with some white paint.

 

[jamyers]

Go down, find the notch with your finger (not running) and mark it with white-out or something easily visible.

Where's the challenge in doing it with the engine off? :roll:

 

[fxp]

find the notch with your finger (not running)

good tip 8)

jamyers - never assume anything mate.

 

[falcondave63]

definatly with the engine off, lol. any othe tips on setting the mixture? i can set it an get it running smooth but at times it will backfire and pop after hard acceleration. sounds like its backfiring through the carb. also, if i'm just cruising and say im in third gear , i'll floor the accelerator, the engine will cut out for a split second and then will pick back up as normal. any ideas?

 

[falcondave63]

any other thoughts on this backfiring and such???

 

[Bort62]

If it is backfiring through the carb, your timing is too advanced.

or you have an intake valve not seating.

 

[falcondave63]

it only started backfiring through the carb when i screwed around with the mixture...this is weird....

 

[mkgcars]

I agree that it's unlikely the mixture is doing it - really sounds like timing. The mixture is really only relative to idle, how's it running above idle? If you're having any issues then that would backup a timing issue.

Relative to the idle mixture: I seem to recall reading that it should actually be tuned with the engine at 1000rpm. You warm up the car, and then turn up the idle until it's 1000rpm, and then you fine tune the mixture to maximize RPM - favoring a rich mixture over a lean one, in the case where the RPM seems to have hit max. You then turn the idle back down to recommended RPM.

There are plenty of threads about slipped harmonic balancers- in case you find it is a timing issue and the timing mark seems to be way off.

matt

 

[falcondave63]

thanks for the info!! yeah, i'm having some stuttering and some hesitation and a lack of power off idle under normal driving. i'll have to check the timing after i re-paint the timing mark on the harmonic balancer.

 

[falcondave63]

well, i finally have time off of work. so, i'm heading to the workshop and i'm going to try and the the ol' girl to run properly for me. i'll keep you guys updated.