engine hesitation just as throttle is opened

Dear Speedsters,
I have just purchased an Apal with a recently (last year) rebuilt 1700 cc type 1 fitted with twin Scats (?).
The PO, a nice fellow but didn't seem to have much mechanical nous, didn't seem to notice the hesitation (flat spot)when you open the throttle and let the clutch out-car takes a "gulp" before accelerating- inviting following traffic to give one a love tap or worse, from behind.
The carbs are brand new and the throttle pumps are working.A mechanic suggested that the acceleration pumps tubes may not be aimed correctly (said they need to direct fuel to the gap between the butterfly and the carb body).
Any thoughts on what the cure might be ?
I have also noticed that the firm that did the work also failed to ensure that the throttles are fully opening (they're only opening about 2/3)
I don't know if it's relevant but the car also has a "stage one" (mild) cam fitted.Oh and a "Monza" exhaust (quad pipe)

Thanks,
Phillip

What type of dizzy?

Dont know-doesn't seem to have any markings-looks new E2-1 no. on rotor, no vacuum adv/retard.

hmmmmm.......

Couple of easy tries, first:

Check the timing. It may be a tad retarded. If it has centrifugal advance (no vacuum hose attached), make sure that it is running 30 degrees before TDC at 3000 rpm. Setting the timing at idle won't do you any good - it has to be set at 3,000 rpm.

If it has a vacuum advance, then see what it is at idle now and advance it a degree or two. It should be somewhere between 6 degrees and 10 degrees when done, but this is ONLY for a vacuum advance distributor!!

Next, if you have points in the distributor, set them with a dwell meter to 46-47 degrees dwell (do this BEFORE you do the timing checks). If you have an electronic module in the distributor, it cannot be altered so ignore this step.

If all these are OK and it's still hesitating (sometimes called "bogging") then check the actuator arms on the accelerator pumps to make sure that they start to squirt gas as soon as the gas pedal (or linkage) is moved, not a few degrees later. You've got classic off-the-line Bog there, and its usually caused by retarded spark or insufficient fuel delivery when advancing the throttles.

One other thing I thought of is that the advance curve of the disti might be way too much retarded at idle due to wrong springs or simply not the correct disti for that engine.

Hope this helps!

Gordon

Are the "twin Scats' kadrons by any chance? If so, then AJ Simms website could also help.

Invoice for engine work just says "supplied twin Scats".
To my eye they look like a Solex.

Both the carbs and the dizzy should have numbers stamped in them. 009 dizzy is notorious for not advancing when you'd like it to. Various remedies if indeed an 009.

They are probably Solex PDSIT Carbs. These carbs work well with a SVDA distributor. They have a vacuum port that will work with the distributor to give a nice smooth advance. For a discussion of this feature see http://www.aircooled.net/new-bin/viewproductdetail.php?keyword2=FSK0060&cartid=0920201023540967 and http://www.aircooled.net/new-bin/viewproductdetail.php?keyword2=IGD0001&cartid=0920201023540967 for info.

I just went through this on a friend's sandrail I was working on. The accelerator pumps were dumping WAY too much gas, and bogging it out. Otherwise it ran fine. Backed off the nuts until they were just touching the springs and voila, no more falling on it's face off idle. Try it, but count your turns so you can put it back. Change one thing at a time, and write it down.

Dual Solex PDSIT 35s, 1915cc motor. SVDA distributor with point eliminator also. Now runs like a top. Had a REALLY worn bug-spray on it, wouldn't idle.

Solution was to balance the carbs.
So easy.
P