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38DGAS air/vacuum pipes

Posted: Sat Mar 23, 2019 4:28 pm
by Wasman
Right I've done my bit and searched the forum, can't see any evidence of this being discussed in any detail.

I'm chasing a misfire and I noticed a definite pause in the engine when I touch a small pipe on the carb. It's a new 38DGAS from AJL.

My questions:

First:
What does the short pipe connecting the base of the carb on the LHS to what looks like a casting holding a diaphram do? I've seen it in other pictures, but what is it's purpose? Could it safely be removed and if so should the pipes be blocked or left open??
IMG_20190323_162438.jpg
The short pipe
IMG_20190323_162438.jpg (191.41 KiB) Viewed 1019 times
Second:
What should be on the end of a brass pipe on the RHS of the carb? Mine is open, should it be blocked??
IMG_20190323_162504.jpg
The brass pipe
IMG_20190323_162504.jpg (161.83 KiB) Viewed 1019 times
All 'sides' are from the perspective of the driver.

Thanks in advance!

38DGAS air/vacuum pipes

Posted: Sat Mar 23, 2019 4:40 pm
by scimjim
First one is the acceleration valve (squirts fuel in when you floor it to prevent the hesitation caused by a delay in the fuel from the main jets responding).

Second one goes to the standard air filter - I tend to block any unused pipes.

38DGAS air/vacuum pipes

Posted: Sat Mar 23, 2019 4:53 pm
by MadMax
I thought the accelerator pump was on the RH side of the carb and has a mechenical linkage? (seen in pic 2)

The stub showing is plumbed into my vac advance on the dizzy.

38DGAS air/vacuum pipes

Posted: Sat Mar 23, 2019 4:55 pm
by Wasman
Thanks guys. I doubt that's my problem as the car is undriveable at the moment, the misfire has got much worse recently. But that's for another post rather than go off topic!

38DGAS air/vacuum pipes

Posted: Sat Mar 23, 2019 5:05 pm
by AJL Electronics
Give me a ring Monday if you are still having difficulty.

There are two vacuum ports. The one on the side of the carburettor is for the vacuum advance to the distributor. If not connected it will cause a weak mixture. The one at the back between the quadrants is for the air cleaner motor. If not being used, it MUST be blanked off, the air leak from notmdoing so will make it very hard to keep running.

38DGAS air/vacuum pipes

Posted: Sat Mar 23, 2019 5:26 pm
by scimjim
MadMax wrote:
Sat Mar 23, 2019 4:53 pm
I thought the accelerator pump was on the RH side of the carb and has a mechenical linkage? (seen in pic 2)

The stub showing is plumbed into my vac advance on the dizzy.
You’re right - the other side is the anti-stall valve.

38DGAS air/vacuum pipes

Posted: Sun Mar 24, 2019 8:45 pm
by Wasman
Thanks for all the useful knowledge guys and offer for phone support from AJL, as usual spot on. Thanks especially to Martin who came round with a spare carb, dizzy and other bits, spent his Sunday afternoon helping nail down the cause of a long running problem! (Carb related but with ignition symptoms!!).