Okay, help with my motor, was: "carb dial in help? (webber IDF 44)" Options

[VaccaRabite]

*edit* Note, cylinder bank 3/4 is not firing. Plugs are oil fouled. All four cylinders have decent compression, considering that the rings probably are not set yet. Carbs are fresh rebuilt, I have yet to check spark.*/edit*

I have set my idle at 1K rpm.
Idle adjustment screws for the 3/4 bank is almost all the way out.
Idle adjustment screw for 1/2 bank several turns in.

Both carbs are idling at 5 kg/h according to my flow meter.

Mix screws for all 4 carbs are 2.5 turns open.

When I open the throttle to ~3K rpm, the 3/4 bank only sucks slightly more air. The 1/2 bank jumps up to about 15 kg/h.

So, where am I off.

I have my weber tech manual too, but thought I would ask here to see if I got a faster "ah-ha" type answer (like usual).

[Joe Bob]

Ya needs a UNISYNC.....

Disconnect the linkage and check the flow on all four throats....

Clean the plugs and re-install. If the rings need to seat, let it run and watch the oil temps....

[VaccaRabite]

Ya needs a UNISYNC.....
Disconnect the linkage and check the flow on all four throats....
Clean the plugs and re-install. If the rings need to seat, let it run and watch the oil temps....

I am using a syncrometer, but it is not Unisync brand. is there a difference? I am using the plastic and rubber one that pelican sells.

Engine is not in the car, and car is not ready to drive, to getting the load to seat the rings is problematic.

You did measure the airflow with the linkage removed at least on one side yeah? And start from scratch?

I set idle without the bar linked up. Tomorrow I might start fro scratch again.

Why are they oil fouled? Carbs won't cause that.
Do a,leakdown and compression check. It sounds mechanical to me.
Swapping carbs will tell if there is an issue with a carb, if the problem follows the carb, thats what it is.. If it maintains the issue on the 3-4 bank its something else.
Process of elimination.

Leak down, done with cold engine and probably non-seated rings was between 8 and 12 percent for each cylinder.

Compression test done today on a warm engine netted results:
Cyl3 115
Cyl4 105
Cyl1 115
Cyl2 122

My guess is that the oil on the plugs was from 2 sources, me putting oil down the spark plug hole the first time I started the engine for the 20 minute break in, and since the 1/2 bank was doing all the work, the 3/4 bank probably did not get hot enough to become self cleaning. When the rings seat, I would expect all the compression numbers to go into the 120s. It makes sence to me, but what to I know?

Tomorrow I will swap the carbs, and see what happens.

Zach

[ArtechnikA]

I am using a syncrometer, but it is not Unisync brand. is there a difference?

Nowadays I prefer the synchrometer to the UniSyn.

I still have a vintage (35+years) UniSyn in my tool chest and I always will, but the Synchrometer is a better product these days, at least for the 6's I work on.

Coupled with the fact that the new UniSyn's are cr&p. I posted comparison pictures a while back in some thread or another. The new ones have untrimmed sprue on the float, huge parting lines on the castings and other indications of very crude manufacture. It almost looks like someone bought the 40-year-old tooling and just kept using it. There are places in that tool where tolerances are critical.

So the "old guys" who got great results with a UniSyn are correct - it used to be a great tool. But what you can buy today is not that tool. A Synchrometer is the way to go.

BTW - as long as you are checking everything - badly-adjusted intake valves is another reason airflow gets out of synch. Especially since you have some time on the motor, maybe it's time to recheck cylinder head nut tightness and valve lash.

[VaccaRabite]

BTW - as long as you are checking everything - badly-adjusted intake valves is another reason airflow gets out of synch. Especially since you have some time on the motor, maybe it's time to recheck cylinder head nut tightness and valve lash.

I forgot to mention that. Valve lash was reset to .006 in and out as to the specs on the cam card. I did that just before going to sync the carbs. The valves probably have less then 10 minutes on them running at idle or just above.

All the rest of the stuff I will do, but it is pouring outside, so probably not today.

Zach