Dual DCOE 40 - Sputtering under load

[nhep23]

Car has been running great, been driving it end of Summer and into the beginning of Fall, when temps are anywhere from 75-95F out.

 

Fired it up this evening at 45F and I experienced sputtering or hesitation when accelerating in first and second gear in RPMs under ~2500. Once I'm cruising at 40+MPH in 3rd or 4th I don't feel it. Drove it for ~20 minutes to warm the engine up and still felt it in the early gears.
 

Ran it this past weekend when it was ~70F out and didn't feel this at all.

 

Timing has recently been set. 1400RPM and the ball on the flywheel.
Carb settings haven't been touched.
Ignition is good, all spark plugs and cable are good. Pertronix ignition

No choke

 

Starts up OK, takes a few pumps and then fires up as normal.

When I have the car parked and in neutral, I can slowly rev up to ~3500 RPM and there is no sputtering/hesitation, so it's only happening when the engine is under load (engaged in first gear and car moving).

Any thoughts? Something easy? Do I have to adjust the fuel mixture? After I drove it around, head/block were hot and the carbs were much cooler... still warm, but cooler.

Yes I looked through previous posts.

No I didn't see anything pertaining to DCOE 40 exactly for this issue, that's why I'm posting.

 

Thanks!

 

 

[halboyles]

Check fuel filters both in-line and in the carbs.

[Son of Marty]

Slipped outa sync? Float sunk? vacuum leak?

Edited October 13, 2021 by Son of Marty

[nhep23]

@halboyles @Son of Marty If any one those things were messed up, wouldn't that be evident when I rev the engine in neutral with no load???

[visionaut]

Could your static ignition timing now be set at too low RPM?

 

1400 with the ball is for regular 02s. Dual sidedraughts would have timing more akin to a ti, no?  The RPM is higher for setting with the ball on a ti.

 

Plus it’s usually the last thing you tweaked…

DCOEs w/o chokes do take a wee bit to warm up to run proper when it’s cold. Mine do, and until warmed up it ain’t great at low revs. But that lasts at most for me 2-minutes (and it can get damn cold here).

 

The oddity’s that if it’s cold out you get it even after it’s all warmed up…and yet have no symptoms on a warm day.

[02Pilot]

I've had DCOEs ice up on cool, humid days, but if you're getting it from the start, that's not what's happening here (I wasn't clear on when you felt this - from the off, or after driving for a while).

[AustrianVespaGuy]

I guess just pull you jets and do a quick blast with carb cleaner to make sure none are plugged up, but honestly those symptoms to me point much more strongly to an ignition issue than a fuel one. You SURE that Pertronix is 100% in good shape?

[02Pilot]

Hmmm, come to think of it, I also had a Pertronix module start to crap out similarly (serves me right for trying to use technology unnecessarily - nothing wrong with points). As the saying goes, most fuel problems are ignition problems.

Edited October 13, 2021 by 02Pilot

[zinz]

By "sputtering" do you mean they are backfiring out the carbs?  This would indicate a lean condition.

 

I have certainly had an electronic igniter fail and give such a symptom ( the early Ireland Engineering dizzies were notorious for this failure).  

 

Timing set to the ball and 1400rpm is okay, I would think (24 degrees @ 1400rpm) that is certainly advanced enough early on, like side drafts need.

 

Perhaps one accelerator pump is not functioning properly?  This would cause such a symptom as you describe.

 

...maybe it's just cold natured?

 

Ed

[visionaut]

1 hour ago, zinz said:

Timing set to the ball and 1400rpm is okay, I would think (24 degrees @ 1400rpm) that is certainly advanced enough early on, like side drafts need.

Ed, I don’t have a ball on my JBR flywheel, so I’ve never used that method (I use the all-in timing method, where I shoot for a total of 34-35 deg). But for the ti, Blue Book lists 25 deg ( the ball?) at 2200rpm — so less early advance with the sidedraughts. ??? ( ti has higher compression too though)

 

FWIW, I also think it’s timing/ignition not fuel. Never had a PerTronix fail, weird it’s temperature triggered  tho.

Edited October 13, 2021 by visionaut

[nhep23]

Update.  The award goes to…… @visionaut!!

 

Drove it again when I got home from work. 60F out. Still sputtering. 

 

Checked timing. Ball still visible at 1400RPM. Distributor was tight. 

 

Cranked it up to 2200 (for Ti) and adjusted distributor. 

 

Took it for a spin. No sputtering, running like a dream. 

 

Took it out again tonight at 45F. Still good. 

 

I guess dual side drafts + the 10.5:1 compression ( forgot to the mention that) needs the 2200 instead of 1400. Now I know. 

 

Thanks everyone for the suggestions. 

[Milo]

=

Edited March 12, 2022 by Vladimir