Burble on Over-run

[opus10583]

Hi,

I first thought to post this in the Cosmetics section, it's purely an aesthetic issue:

How do I get my newly DFEV-carbed 1800 to burble melodically on over-run?

Thanks,
Mark

[boogiedude]

Over run? Do you mean dieseling?

[opus10583]

Over run? Do you mean dieseling?

Hi,

No, when you back off the throttle on a downhill run or setting up for a turn...

Thanks,
Mark

[GeorgeT]

That may be a timing adjustment. I can change how my injected Spider sounds when I let off the gas by changing the timing.

[124JOE]

remove air cover look down the venturies
give it some gas and see if its followed by a few drops of gas
if you see drops when you let up
then your mixture screw is too far out"play with it untill you have no drops and still has go power"

do you have a vacume gauge
put one on the intake port
dial your mixture screw to get as much vac as you can"i got 15 inch pounds"

[Weelan]

Joe would that cause or prevent the burble? Seems like that would prevent it, I think the OP wants to cause his engine to make that sounds. I think?

[opus10583]

Hi,

So that would be rich on the idle screw and more static advance?

Thanks,
Mark

[124JOE]

its rich on the mixture screw
the timing should be locked at 10 degrees BTDC

[opus10583]

Hi Joe,

Thanks, but having this car is all about making me grin, and the burble makes me grin.

Turns out less advance might be what I need for that:

http://autospeed.com/cms/title_Getting- ... ticle.html

...Vacuum distributor then?

Thanks,
Mark

[manoa matt]

Mark, I don't understand. When you got your 78 with the stock carb you wanted correct jets and spot on jetting, now with a 32/36 you want to have improper timing and improper mix to make a cool sound.

You can get that sound if you drill a small hole in the exhaust pipe near where the cat would be. It will pop and gurgle/burble on over-run. (not serious, but it would)

Regardless the 32/36 should do that anyway because it does not have the fast idle system.

Just messing with ya'

[opus10583]

Mark, I don't understand. When you got your 78 with the stock carb you wanted correct jets and spot on jetting, now with a 32/36 you want to have improper timing and improper mix to make a cool sound.

You can get that sound if you drill a small hole in the exhaust pipe near where the cat would be. It will pop and gurgle/burble on over-run. (not serious, but it would)

Regardless the 32/36 should do that anyway because it does not have the fast idle system.

Just messing with ya'

Hi Matt,

...I'm an enigma, wrapped in Krispy Kream.

A lot of what you see is me thinking out loud, a lot is four major projects in the air and needing something to distract me even further while I find solutions, some is whistling past the graveyard.

Thanks,
Mark

[TronDD]

My Spider does this and I'm trying to get it to stop.

Haven't had time to check timing yet (ugh, there is an ugly pun in there), I can let you know what the timing was, if that turns out to be the cause.

Tim.

[124JOE]

remove air cover look down the venturies
give it some gas and see if its followed by a few drops of gas
if you see drops when you let up
then your mixture screw is too far out"play with it untill you have no drops and still has go power"

do you have a vacume gauge
put one on the intake port
dial your mixture screw to get as much vac as you can"i got 15 inch pounds"

this may help you then

[TronDD]

I adjusted the idle mixture last summer with no effect. I didn't have a vac gauge so I adjusted to highest idle.

Tim.

[engineerted]

The Burble or popping on Decel is caused by a lean condition in one or even all of the cylinders, the mixtures are too lean to burn in the cylinder and it's pumped in to the exhaust where it is ignited by another cylinders hot gas or even the exhaust valve. This condition is acerbated by adding high flow headers and free flow exhaust systems as this helps lean out the mixtures. So if you want this to stop or reduce the popping Burble you need to richen your idle circuit. On a carbureted car you can only go so far before idle quality start to suffer.

The same goes for adding burble, lean the idle mixture and /or add a flow thru exhaust system or better yet add adjustable cam pulleys and increase the valve overlap.