327 in '68 Malibu

[kirkwoodken]

Quote: There is no "correct" universal setting. If you can turn the screw down all the way and it's not surging at light throttle, that is probably the best lean setting. With a wideband and the correct metering rod / jet combo, you can see the A/F ratio change with a half turn of the screw. If you don't have a wideband, go as lean as you can go without hurting drivability. If it has a surge issue now at light throttle cruise, turn the screw out a bit and raise the "lean stop". Unquote.

This is how people have been tuning for "lean" as long as I can remember. It does help to have a distributor machine. You need to know your combined centrifugal and vacuum cruise advance, as it should be around 48-52 degrees as a starting point. You lean out the primaries until you get lean stumble. What I do when I get to stumble is look at the plug gaps. You may have better luck opening the gaps as a lean mix is harder to light and sometimes a larger gap will smooth out the stumble so you can go leaner. And sometimes not! Years ago I had a 6 cylinder with Duraspark. Always ran and idled rough. Opened plugs to .080" and smoothed out the running at all RPM. From my experience, you should be able to cruise at 16:1. Keep in mind that cruise timing and WOT timing are two completely different circumstances. Lean mixtures burn slower than rich mixtures to a point. If you have an engine you want to cruise with, you need vacuum advance, otherwise you are running with retarded timing at cruise speed and keeping more heat in the engine, which is not good. It's not the other way around.

[vds]

What is the procedure to fine tune the idle mixture on this '79 305 Qjet ? It's idle is a bit like a Holley when you lose
the adjustment on the idle mixture screws, when the primary throttles are open too much at idle It's ok at idle
out of gear, but when you drop it into gear it's not so happy, and if you bring up the idle speed for when it's in
gear it then doesn't respond to the idle screws when it's in neutral

[F-BIRD'88]

Did you do as I posted re: re curving the distributor? It wants a lot more intial base timing at idle that DOES NOT drop off when in gear.
re curve the distributor for a shorter 10deg mech advance curve
This allows 24-26deg initial base timing , a 10deg advance curve and thus 34 to 36deg total max mechanical advance.

Now it will idle correctly in gear with responsive idle mix screws and correct pri throttle blade/T slot exposure at idle.
use a primary metering rod step up spring that stays DOWN (lean) at idle
EG: 4" vacuum rated. ( edelbrock Qjet. tuning part.)

Then : also limit the max travel of the vacuum advance to 10-12deg max vacuum advance limit.

Use only ported vacuum on the carb for the vac adv.

Unless and until you correct the distributor advance curve you can play with that carb
for ever and will not get it right.
You cannot get the right curve just by just swapping the advance springs.
You need to limit the mech advance travel to 10deg. (20 ish deg is stock)
That 224-234 465-488 114 cam needs this mod to idle correctly and be responsive off idle.
get a 3000++ / 3500 stall converter and gears if you want it to GLH. (1/4 mile acceleration)

[vds]

Good advice Firebird It requires quite a lot of the advance travel in the distributor to be restricted to get to that
24 to 26 static and arrive at 36 total I cut the travel by half and it still requires a bit less travel It made the thing
better on the bottom end and cleaned up the idle Only problem now is he took it for a run, and it got away on him
and charged the curb He's faced with some undercar repairs now as a consequence

[rfoll]

It should be a requirement to learn when to lift before you drive a hot car. One of the local idiots bought a 572 and put it in his 4 speed Malibu. He took his buddy for a ride and it smoked the tires at speed. They went into a ditch and buddy didn't survive.

[econo racer]

Sorry to hear this. What else did you do with your ride? I.m interested because I also have a 68 malibu. It needs alot of work.

[vds]

He had it repaired, luckily he had enough insurance on the thing to achieve this. They had to lift the body off, as it had collapsed through the dogleg bends behind the suspension arms and before where the frame runs straight under the
sills. The repair shop wanted to put another frame in it but they couldn't find one easily, so they had to pull it back
straight. The distributor rework really woke it up, but It still needs a bit more tuning. A friend of his has a rolling road and he was going to put it on there and see where it's at

[vortecpro]

It has a powerglide transmission, and about 800 rpm higher stall converter, with 3.08 rear ratio

It will be a dog... That cam in a 327 in a 68 malibu needs serious gears, a th350 and 10" 3500 stall. A 9" race converter and 4.56 is not too much.

That 224-234 114 LSA cam works real good with the 142-144 lil roots blowers in a low cr SBC Another option for that car/cam/327 lame gears is nitrous oxide injection.

Change the cam. Something small duration 211 or LESS @.050"
It will be better in every way.
EG" comp cams dual energy cs-265DEH-10 211-221 .442 .465 110/106
PN 12-208-2

The open carb spacer is a big mistake on that setup.
Modify a 4 hole Q jet adapter to "split style" You want the divided plenum.

Your probably not going to like the 327 with 240 @ .050 SL cam in my shop truck with 3.08 gears and 30 inch tall tires LOL Oh....I just noticed I did the dist wrong as well.....its locked out

[rfoll]

I didn't see any mention earlier, but if the 1" spacer under the carb is open, it can make tuning very difficult. My experience with open spacers on these carbs is that the throttle response at low rpm becomes very soggy, and it requires the carb mixture to be richened considerably.

[F-BIRD'88]

It has a powerglide transmission, and about 800 rpm higher stall converter, with 3.08 rear ratio

It will be a dog... That cam in a 327 in a 68 malibu needs serious gears, a th350 and 10" 3500 stall. A 9" race converter and 4.56 is not too much.

That 224-234 114 LSA cam works real good with the 142-144 lil roots blowers in a low cr SBC Another option for that car/cam/327 lame gears is nitrous oxide injection.

Change the cam. Something small duration 211 or LESS @.050"
It will be better in every way.
EG" comp cams dual energy cs-265DEH-10 211-221 .442 .465 110/106
PN 12-208-2

The open carb spacer is a big mistake on that setup.
Modify a 4 hole Q jet adapter to "split style" You want the divided plenum.

Your probably not going to like the 327 with 240 @ .050 SL cam in my shop truck with 3.08 gears and 30 inch tall tires LOL Oh....I just noticed I did the dist wrong as well.....its locked out

Locked out + vacuum adv would work very well with a 327 and 240 cam. But others will get all over you about that. Bla bla bla