Dual Weber IDF 40s, Carb Rookie question... Options

[rfinegan]

Sounds much better...did you sync with the snail or just first movement of the slave?

[malcolm2]

Sounds much better...did you sync with the snail or just first moment of the slave?

I double checked with the snail after I tightened the cable.... All flow numbers FOR IDLE still match the table I posted above. made no changes there tonite and no testing over idle.

But I do want to know about the accell pumps I adjusted. Thoughts on returning those?

[r_towle]

That sounds better, much better.
Go drive it

[r_towle]

I would stop adjusting now.
I would swap in new plugs, drive it till hot, try to shut it off while revving with no idle
Then read the plugs

You are down to just reading the plugs now without a EGT sensor on each port….and don’t worry, reading plugs is how it is still done.

Google how to test and read plugs
Specifically the process.

For me, when I think I am right, I take a highway run.
I line up an exit at speed then shut it down and glide into the rest area.

Plan ahead, find a simple safe place todo this

The idle circuit is naturally very rich, so it will make the reading of the plugs false if you idle too long after the run.

Hard to explain.

But, before you adjust anything you now need data.

[porschetub]

If you have big differences in from and back on a carb make sure the plates are closing at the same time. It is very common to have twisted throttle shafts on used carbs. These are new so it should be fine?

Not likely the throttle shafts are twisted due to them being new.still a good point as if the arm or cam wheel is not supported when tightening this will happen ,had that on one of my Zenith carbs and had to replace on spindle and the jointer coupler...so you never know.
Anyway I degress,have read this one over and over and IMO there is a vacuum problem caused by valves that aren't seating correctly or a leak @ the manifolds/carbs,reason for saying this is;
incomplete combustion as seen on the plugs ?,could be ignition issue also ?,
uneven vacuum reading well out of specs and not correcting with tuning,
uneven setting "tip in" idle on throttle stops,
valves not seating when closed ,could be correct lift not dialed or geometry wrong ?,
piston rings haven't "bedded in " so a compression test will reveal that (IMG:style_emoticons/default/sad.gif) ,
What we don't know is with other variable's but I would be a doing a compression test first,think you are over carb tuning as the vacuum is the issue here.
good luck and cheers.

[r_towle]

If you have big differences in from and back on a carb make sure the plates are closing at the same time. It is very common to have twisted throttle shafts on used carbs. These are new so it should be fine?

Not likely the throttle shafts are twisted due to them being new.still a good point as if the arm or cam wheel is not supported when tightening this will happen ,had that on one of my Zenith carbs and had to replace on spindle and the jointer coupler...so you never know.
Anyway I degress,have read this one over and over and IMO there is a vacuum problem caused by valves that aren't seating correctly or a leak @ the manifolds/carbs,reason for saying this is;
incomplete combustion as seen on the plugs ?,could be ignition issue also ?,
uneven vacuum reading well out of specs and not correcting with tuning,
uneven setting "tip in" idle on throttle stops,
valves not seating when closed ,could be correct lift not dialed or geometry wrong ?,
piston rings haven't "bedded in " so a compression test will reveal that (IMG:style_emoticons/default/sad.gif) ,
What we don't know is with other variable's but I would be a doing a compression test first,think you are over carb tuning as the vacuum is the issue here.
good luck and cheers.

Pretty sure a compression test was one of the early things that he did, maybe at the beginning.

[porschetub]

If you have big differences in from and back on a carb make sure the plates are closing at the same time. It is very common to have twisted throttle shafts on used carbs. These are new so it should be fine?

Not likely the throttle shafts are twisted due to them being new.still a good point as if the arm or cam wheel is not supported when tightening this will happen ,had that on one of my Zenith carbs and had to replace on spindle and the jointer coupler...so you never know.
Anyway I degress,have read this one over and over and IMO there is a vacuum problem caused by valves that aren't seating correctly or a leak @ the manifolds/carbs,reason for saying this is;
incomplete combustion as seen on the plugs ?,could be ignition issue also ?,
uneven vacuum reading well out of specs and not correcting with tuning,
uneven setting "tip in" idle on throttle stops,
valves not seating when closed ,could be correct lift not dialed or geometry wrong ?,
piston rings haven't "bedded in " so a compression test will reveal that (IMG:style_emoticons/default/sad.gif) ,
What we don't know is with other variable's but I would be a doing a compression test first,think you are over carb tuning as the vacuum is the issue here.
good luck and cheers.

Pretty sure a compression test was one of the early things that he did, maybe at the beginning.

Thanks Rich ,missed that...not good for a "fresh" build ,even with low comp pistons it should be 125 psi even ish if run in properly ? the variation between cyl's 1 and 3 exceeds what is the norm even for a used motor .
Think the OP should do another compression test when engine is warm and if result is the same put a squirt of oil down the plug holes,if a retest shows an increase thats the issue,if as I suspect you will need to do a "leak down" test on your valves also.
Don't for a minute trust the manifold gaskets with the common intake manifold kits around,the EMPI ones for example are very soft and too thick causing leaks after they are fitted ,ask me how I know,most likely better check that first.
I persist asking about this but fitted 36dlra's to my last carb case from 411,NOS raised top pistons and 1.8 barrels,fully rebuilt heads,my carbs had little done to them but setup on a bench and cleaned,motor ran unreal almost out of the box as they say,so without being a dick something is wrong here reason I'am asking,cheers.

[malcolm2]

Something could have gone wrong. The mechanic here is me. Even doing the BEST LEAN set-up in the beginning was challenging to me. The Weber to-do list was not clear for a real carb beginner, like me. Poorly written, if you ask me.

Part of the reason I paid AC.net for the cleaning, set-up and jetting, etc..... I figured I could follow directions to get the damn thing on the road.

This process has taught me a good bit, but not near enough yet.

It is running nicely now, or at least I would rank it as NICE. Ran some good hills etc... this week. Bus is a different animal vs the 914, wow is it different.

Gonna put some more miles on it and take the plug reading recommendation after I fix a few other items.

Thanks again everyone.... Stay tuned.

Clark

[r_towle]

Congratulations.
remember...same (or less powered) motor...yet add in terrible aerodynamics, and about 1500 lbs.

The great thing about a bus is it teaches you how to plan when you want to pass someone, or go up a long hill.

momentum is your friend.

Rich

[majkos1]

hey guys,
Kevin here,
been lurking here ,working on a friend 914, fresh rebuild, trying to carefully break in the motor,, even added zinc for peace of mind.

I'm a Fuel injection guy, absolutely hate carbs on a stock 914 motor.
so you know where I come from.

anyhow, helping my friend here, and willing to learn about carbs and their adjustment stuff.

I had dual carbs on my Type III awhile back, so familiar with them.
(I even put back the fuel injection the ole Type III had.)
another story.

After fidgety with the 40's Weber carbs,
get them settled in,
removal of throttle linkage info was valuable !
(someone else had rebuilt motor and install the carbs)

experiencing constant backfire issues.
someone mentioned the exhaust may be leaking?
I wouldn't doubt because the improper used of washers on the exhaust studs,
I corrected em,

should I remove the exhaust to inspect for leakage or is there any other suggestions for me?

Me and Joe, his 914, are trying to get his 914 ready for Red Rocks. (IMG:style_emoticons/default/driving.gif)
will appreciate any info or leads.
Thanks! (IMG:style_emoticons/default/shades.gif)

[majkos1]

oh yeah,
his motor is a 2056

[Superhawk996]

experiencing constant backfire issues.
someone mentioned the exhaust may be leaking?
I wouldn't doubt because the improper used of washers on the exhaust studs,
I corrected em,

should I remove the exhaust to inspect for leakage or is there any other suggestions for me?

Where is the backfire occurring? Out of the intake manifold or in the exhaust system?

No point in messing with the exhaust if it’s backfiring out of the intake

[majkos1]

yes, back firing through carbs.

[Superhawk996]

Verify plug wires vs firing order.

Verify timing

Verify valve lash - especially on intake valve but do both intake and exhaust while you’re there. This should be done before adjusting carbs if there is any question about what valve clearances are.

[technicalninja]

SuperHawk has good advice: (IMG:style_emoticons/default/agree.gif)

yes, back firing through carbs.

If ignition timing is correct, advances working then.

Compression test, leak down test, R&R heads to repair poor sealing on intake valves would be my next steps.

If comp/leak down were good I'd be confused. (IMG:style_emoticons/default/headbang.gif)

[majkos1]

SuperHawk has good advice: (IMG:style_emoticons/default/agree.gif)

yes, back firing through carbs.

If ignition timing is correct, advances working then.

Compression test, leak down test, R&R heads to repair poor sealing on intake valves would be my next steps.

If comp/leak down were good I'd be confused. (IMG:style_emoticons/default/headbang.gif)

Thank guys!!

I was wondering about the valves too,
Previous mechanic was a lil out there, and I inherit this mess.