Need suggestions with possible twin carb issues...

Well a day of great news for everyone :grin: First Jeff and not blowing another head gasket and I've done my compression and spark test and have fantastic results.

First drove the car around the block for 5 minutes to warm up engine and then did compression test with my son turning the key and me holding WOT one cylinder at a time.

#1...180
#2...190 (thank God!)
#3...180
#4...185

Never would have guessed that the cylinder in question #2 would have the highest compression of the four. I was so shocked that I did the test twice to confirm the results.

I checked the spark coming from each plug lead at the spark plug and the spark was healthy.

I'm very relieved that I have great compression across all four cylinders so I'm thinking my problem with #2 lies with carb. I'm gonna try shooting compressed air in the carb where the idle/mixture screw goes to see if that helps.
 
Good news (so far) Pete. And those comp #s aren't bad either :)

I would check your idle jets too. Were these the Carbs you had on the car before? You didn't change anything?
 
GREAT NEWS... now, as a last resort...

Trade the carbs, left for right. A bitch to do I know, but if that is indeed where the problem is, it will prove it.

You probably will not need to care for the linkage as it should fail just idling from what you have said earlier. If the problem follows the "roll", its in the carb. If not, then it is elsewhere... gotta be electrical... possibly a defective dizzy cap with an internal crack or crossfire.

I'm sure you have rolled plugs by now, right?
 
Yes these are the exact same carbs I had on before with a stock bottom end. Now with increased displacement and my compression is up to 10.6:1 from 9:1 before. I also don't know what effect the 40/80 camshaft which has much more lift and duration then the PBS camshaft I was running before has on the carb setup.

All those internal engine changes may have no effect on carburation which is what I'm trying to research and learn.

I paid really close attention to what the engine was doing when I went for my warm up drive last night. Although my AFR's stay between 12's and 13''s the car seems to stumble or lag at around the 2500rpm mark which from what I've read is the transition from the idle jets to the mains.

I'll keep learning and we'll get it.:jedi:
 
Swapping the carbs is certainly something I could try. By rolling plugs do you mean replacing or just swapping them from cylinder to cylinder to see if the problem follows the plug?

Because I've never rolled anything other then the engine over:wink2:

You always make me laugh Tony!!!
 
About the DCOE's

The Webers have four fuel circuits that you need to concern yourself with:
1) idle - closed butterflies - adjusted with idle jets and mixture screws
2) progression - cracked butterflies to around 3000rpm - fixed on older carbs but may be adjustable on yours
3) main - about 3000rpm and up - adjusted with main jets, air correctors and emulsion tubes
4) pump - quick acceleration - mainly adjusted with pump jets and exhaust jets

All of these overlap to some extent. Your throttle lag at around 2500-3000 is probably caused by inadequate overlap between the progression and main circuits. Assuming that the carbs are assembled correctly (many aren't - aux venturis are installed incorrectly or jets can be forgotten) you are probably looking at emulsion tubes to fix the lag condition.

About the cylinder that isn't pulling, I think you are down to double-checking valve adjustment and carefully pulling all of the parts out of your carbs right down to the main venturis and verifying that everything is as it should be.

Because you've rebuilt your motor, everything you knew about the DCOE setup on your car may change. It is drawing a lot more air.

BTW: Mike Pierce (Pierce Manifolds) sells a couple of very good DVDs regarding DCOE tuning.
 
Do you have an update on your condition???

I am just really curious if you've been able to resolve your problems. I'm sure we could all learn something from your experience.
 
Sorry for the delay on updates but I just wanted to rule out all other issues that could possibly cause poor running conditions.

-Compression is excellent
-verified valve clearances today
-determined that I have a weak spark on the #2 plug wire so I'm ordering a set of Magnecor plug wires.

As for the carbs: AFR's are excellent 12's at idle and under throttle but lean out 15+ when I accelerate hard and then let off the throttle. If I gear change by 3500rpms then the afr's remain between low 12's and mid 13's

This last test drive was with a bad plug wire on #2 so I'll do another test run and report back after my new wires arrive.

Current setup:
32 chokes
F11 emulsion tubes
F8 55 idle jets (tried the F8 50 and would lean out as soon as I started to accelerate)
pump jets 45
145 mains
190 air correctors

Jetting I want to try:
F14 or F15 emulsion tubes as they are richer throughout the rpm range
F9 series idle jets as they are richer in 45 and 50
Possible smaller pump jets as other with similar engine setup are running 35 pump jets.
Want to try 135 and 140 mains as I have 130 and below.
 
It's hard to tell with one cylinder not pulling...

Understand that my direct experience with DCOEs is with a race car (1500 w/ big valves * 8K+ rpms) and I have 40's - though I wish I had 45's.

It seems to me like you wouldn't mind leaning out the idle just a bit. Low 12's are good for power but you don't need all that at idle; it just smells-up the joint. I wouldn't mind a high 13 in that range.

I don't like what a 32 choke does for my car; what kind of revs are you planning on pulling with your new motor? It is a street car, right? I run 36 but would go bigger if I could. Just remember that I'm looking for peak power. Dyno shows that 32 provides just a little more mid-range grunt but really hurts the top end.

I think the F16 and F11 tubes are most common in X1/9's. I'm betting that you are close enough without messing with those - unless you are trying to address that 2500 rpm lag that you spoke of earlier. That might disappear though if you start to run on all four cylinders.

Keep us posted.
 
I completely agree that firing on 3 cylinders even my AFR readings will most likely all change.

As for what type driving style I'm after...
Yes it is a street motor but I spent thousands in parts and machining to put together this 1600 stroker motor with high compression, big valve head, aggressive camshaft, lightened and balanced full bottom end. I'm looking for power between 2500 and 7000rpms.

I agree that 32 chokes are probably too small for what I'm after so I'm considering trying 34 chokes. Many years ago I was running with 36 chokes but the bottom end was stock and the power wouldn't come on before 4500rpms which wasn't suitable for street driving.

I appreciate you taking the time to assist me.
 
Yeah Pete... Sorry for the vagueness...

"Rolling" means to swap plugs, wires, carbs, etc. to see if the problem stays with the bad side, or "rolls" to the other side.

Glad I can bring some humor into your life... I see humor in so many things... must be the (prescription) drugs I take... Stay young, I'm beginning to question if growing old is worth it!
 
Magnecor plug wires arrived yesterday and to say there's a difference in the quality compared to OEM would be an understatement. You can just see the quality in the construction of these awesome wires.

I'm firing on all four cylinders now with the new wires but the transition from the idle jets to the mains is still lagging. I'm going to pull all the jets and blow everything out with my compressor and hopefully that will fix the issue. I'm searching for a good write-up or video on cleaning Weber DCOE carbs and wonder how much can be done with the carbs installed in the car or should I just pull them and order a new gasket set and properly clean them?
 
My offer still stands

I have a copy of Des Hammills book "How to build & power tune Weber and Dellorto DCOE & DHLA carburetors." I can mail it to you and you can mail it back when you are done with it.

Cheers,

Rob
 
Sorry for not jumping on this opportunity the first time you offered. I can use all the help I can get. I'll PM you with my mailing address and you can let me know how much the postage is.
Thanks,
 
No worries Pete

I'll send it your way. No hurry to send it back, I don't use either of those carbs these days, it's just part of my library.

Cheers,

Rob
 
Plug wires do help...

Good news on that.

About your flat spot in acceleration: your comment earlier that you "tried the F8 50 and would lean out as soon as I started to accelerate" seems like a clue. I really think that you'll be best served here if you think of 4 distinct fuel circuits: 1) idle, 2) progression, 3) main and 4) pump. And, while there is overlap between these circuits, you wouldn't play with idle jets to correct a problem at 3500 RPM.

Of these four circuits, the progression is probably most problematic because it is the least tunable.

Assuming the carbs are clean, I guess I'd work in the order:
1) Set float levels to spec - be aware that "spec" is different for brass vs plastic floats.
2) If you didn't change them the last time you touched the pump jets, replace the aluminum crush washers under the pump jets - a drop of fuel past one of these will cause you troubles.
3) Make sure the idle speed screws are adjusted to just touch the stops +1/2 turn. The butterflies should be nearly closed and the screws are just going to prevent the butterflies from closing completely and binding in the carb throat.
4) Preset the mixture screws - this is a bit tricky because there are different types of screws - long and short taper - so know which you have and set them accordingly.
4) Re-synch the carbs
5) Change idle jets until you get the idle mixture to something closer to 14 than 12. Resist the urge to set the idle with the speed screws. Idle speed ought to be jets and mixture working with a nearly closed butterfly. Long-taper mixture screws need to be adjusted to 2 1/2 - 3 1/2 turns from the seat - if you need to close them more than that to get your speed down, you need a leaner jet.

After all that I think it's time to go for a ride and document as best you can at what RPM range you feel your flat spot.
 
Replacing crush washers for pump jets is easy enough but I've never set my carb floats myself before.

I found this video but how necessary are having these special tools to set the floats?

[ame="http://www.youtube.com/watch?v=WT_CXqG8tn4"]DCOE Weber Float Level Adjustment - YouTube[/ame]
 
That vid is pretty good I think

That looks good to me - you don't really need the tools that he mentioned, you just need something to measure the gaps. I've used a ruler but it's awkward - just find something the right thickness, like a long bolt or a drill bit and that should work fine. If you have brass floats and you are using a crude tool, you need to subtract something for the seams - they say set it to 8.5mm so just use 8.
 
My DCOE's are the 45DCOE 152's which are the later style not using the brass floats. From the video I gathered that that a 12mm drill bit will set the gap perfectly when the float is closed but I didn't get the gap amount for when the float is open. The chart at the end of the video lists the measurements for all the older DCOE models but not the 152's

I'll keep searching the net to find out the float settings for the 152's
 
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