VDL 4412 carb stumble

[roybeckett13j]

Bought a VDL 4412...have some issues.

It sounds GREAT revved up, reves from 2500 up awesome.

But, it wont get off idle smoothly.

Installed the carb and a new spacer when it started this.

Could it be a carb problem? vac leak?

also...when i check the timing and set it at 34 degrees at 300-ish, it stumbles worse coming off idle. But when i set it by ear it gets better! timing light going bad?

thanks all.

[stock car driver]

What size discharge nozzle a lot of the carb builders put a tiny one there.

willys has a 18 and it wouldnt work for me at all.

I went to a 28 and havent looked back.

31 is also a common one if you dont have a 28-31 on there i would try that first.

[TeamTerminator]

Check the pump operating lever spring. If thats loose on the accelerator pump lever it will cause a stumble like u are having reving off idle. Had this happen last week on my 2 bbl last week. after adjusting the spring to get the slop out it reved up great after that.

[roybeckett13j]

Ive tried a few different nozzles, cams and adjusting the linkage/spring with little avail.

So far I have...

Put the old carb on, ran great.

put all the accelerator pump stuff from old carb to new carb, no help

put metering block off old carb onto new carb, no change.

changed the float level all over the place, no help.

So, that takes out the metering block, accel pump, and foat level/bowls, and leaves the body of the carb as what should be causing this.


Sorry post is getting long, please stick with it...

One thing I noticed, the holes in the throttle valves in the old carb appear to be about 1/8th inch...the new carb has holes considerably bigger than the old ones.

Could this be getting the transition slots covered too far?

needin some help, thanks.

[stock car driver]

Im not sure what happens when those holes are too large, I do know John at JDR Performance told me not to drill out the 4412 like my 350 carbs unless I absolutely have to. His email is on his website, I would shoot him and email or send him the carb it sounds like something you bought used... Ive had no luck with used stuff from anyone lately it seems racers are desperate and willing to sell junk way more often now than in the past.

[let-r-eat]

Have you narrowed it down to rich or lean? Covered half the carb/choked ect to see if it helps? 4412 on a v8 should rev quick and clean.....

[roybeckett13j]

http://i930.photobucket.com/albums/ad143/bigroy1978/IMG_20110704_141514.jpg

Picture of the race baseplate (right) and stock baseplate (left).

You can see the difference between the holes. Also, there is a port that has what looks like a restrictor in it on the end oppisite the PCV port on the stock, but not on the race. Is that blow out protection?

The plugs were nasty black, so im guessing its really rich...

[stock car driver]

those are big holes, I would send the carb to john hell fix it for you and run it on his test mule motor.

[hogracer3d]

the VDL staff has excellent customer service, hell he even answered the phone when he was at the races on a Saturday, when I had an issue, that turned out to be not the carb at all

[let-r-eat]

Looks like someone that didn't have a clue played with it.....Does the idle mixture screws kill the engine when screwed in?

[pickel]

looks like an alcohol base but i could be wrong

[roybeckett13j]

Ok, figured it out.

Put the old base on the vdl carb, helped some.

Pulled the plugs and found two bad, changed them...helped more!

Realized the accel pump arm was hitting the adapter stud about 3/4 stroke...fixed it!

Geeze...sometimes I wonder about myself!

Thanks all!

[stock car driver]

Ok, figured it out.

Put the old base on the vdl carb, helped some.

Pulled the plugs and found two bad, changed them...helped more!

Realized the accel pump arm was hitting the adapter stud about 3/4 stroke...fixed it!

Geeze...sometimes I wonder about myself!

Thanks all!

You gotta use a short head bolt there on some adapters if you dont grind them down to make space for a full bolt head, no way on using a STUD for the adapter mounting under a 2 barrel with a 4 barrel adapter..