Vacuum Question

Adrian Worman · Post by **Adrian Worman** » Fri Jul 04, 14 9:14 pm

Happy to see you out in it mate, the grin on yer face sez it all

Me girl mate loved the 'Bullit' holes

morgan · Post by **morgan** » Sun Jul 06, 14 1:00 pm

Pete - will do

Ade - good to see you too. Yeah, was happy that she was working so well. Got some spare bullet holes if you want em...

morgan · Post by **morgan** » Thu Jul 10, 14 8:57 pm

Right. Here's the latest....

Whipped the dizzy out (because I am all confident now

) and changed the advance stop bushing. Swapped the springs to the appropriate curve.

Set car up. 20deg seems too much, slight kickback. 18deg seems happy. at 3K she is running 34deg on the nose.

Took her for a run - pulls like a train (even my little old mild lump). Very happy. Still pongs of fuel, so hooked the vacuum up again. Bangs, pops, misfires, wont run at all as soon as you get past idle...

Now researching 'adjusting vacuum'. I'd like her cleaned up a bit but something is wrong here. Its advancing/retarding alarmingly on vacuum.

Still - overall, even if I never get that bit working, the rest is very good. Very happy

I can live with her ponging of fuel - especially when she runs as good of this.

morgan · Post by **morgan** » Fri Jul 11, 14 10:26 am

Interesting. Not just me....

Exactly this -

https://www.msdignition.com/forum/showt ... hp?t=14403

Dave-R · Post by **Dave-R** » Fri Jul 11, 14 11:19 am

Have you tried adjusting it? Hex key inserted in the hole.

morgan · Post by **morgan** » Fri Jul 11, 14 12:19 pm

Dave wrote:Have you tried adjusting it? Hex key inserted in the hole.

Yeah. Thats what Ade suggested. Gonna have a play. I'm like the kid that cant leave well alone now it working

EDIT - MSD vac cans cant be adjusted with a hex apparently ?!? Need to fit an alternative one. (source - MSD tech forums). Odd.

Dave999 · Post by **Dave999** » Fri Jul 11, 14 1:14 pm

suck on the vaccum pipe

it should be almost impossible to suck anything in. and if you can you should see the advance plate move in the dizzy

if your mouth fills with the joyous takes of oily fumes

your vacc can diaphragm is busted or leaking due to shoddy workmanship and by plugging it in you just intorduced a major air leak.

Dave

morgan · Post by **morgan** » Fri Jul 11, 14 1:46 pm

Will give it a go - but I am pretty sure its moving. Runs like a dream with vac plugged. Plug vac in and idle stays but any increase at all bangs (like a mortar cannon) out the exhaust, stumbles, misses, drive would be impossible....
Its advancing/retarding WAY too much. But in the interests of science - yes, will update later !!

Dave-R · Post by **Dave-R** » Fri Jul 11, 14 2:54 pm

Just bin the Bananarama! thing. You don't need it. I never used one.

Post by **MattH** » Tue Apr 26, 16 8:33 am

Morgan, did you ever solve the stink?
Ive got that issue now, fumey at idle and a day out in the car is making eyes water and clothes stink of unburnt fuel. (318 2 barrel, standard electronic factory dizzy).

I searched up this thread and wondered if you got the vac back on to cure the fumes?

morgan · Post by **morgan** » Tue Apr 26, 16 9:36 am

Nope. Never got it working. Eventually got the timing to what I consider to be the best compromise (From memory its 16/34 with a stock curve).
Its still fairly fruity - you pong of exhaust a bit, but it doesnt burn your eyes. (or in the words of the MOT man - 'I could run another car on what comes out the back of that') I'll bring it to the herts meet in the summer, you can have a sniff

I'm basically leaving it now. Exhaust needs welding up where it blows a bit at the joins - that should ensure all fumes go out the tailpipe. Hoping that will be it.

Blue · Post by **Blue** » Tue Apr 26, 16 10:02 am

I agree with Dave, plug the vacuum can and crank up the initial. Modern fuels seem to need so much initial advance these days, having a vac can connected as well just advances the timing way too much.

morgan · Post by **morgan** » Tue Apr 26, 16 11:53 am

On mine (which is an MSD) You can change the advance stop bushing, so I could play around with initial without letting it go much past 34 at the top. Dont know if you can prevent this with yours Matt ?

Dave999 · Post by **Dave999** » Tue Apr 26, 16 2:10 pm

fumes at idle is possibly lack of ignition advance at idle

you wouldn't necessarily want to provide that with vacuum advance. better off with mechanical.

i.e you set the initial much higher than for 1970s petrol

trouble is with so much initial advance as you open the throttle, the first crack, you expose the ported vacuum port to high vacuum and the vacuum advance pulls in too much.

so the vacuum advance needs to be limited.

trouble with that is

if you limit it too much you don't get the correct advance at higher RPM

High RPM 3000 + you will have 30-34 BTDC max advance on cruise or coming off the gas, initial + mechanical in the dizzy and you then need the advance pulled up to 46-50 BTDC for that throttle closed idle mixture only, high rpm spell, by the vacuum can

if you limit the vacuum advance you don't necessarily achieve that.
depends how the vacuum advance adjustment works

just limiting its advance (i.e purely the distance the lever travels

Or increasing the vacuum necessary to get that advance.

i.e you need a stiffer vacuum can (round cans)
or adjust the one you have (the one with the hex shaped profile to the front)

you probably need a can that wants a higher vacuum to achieve its full advance

so it doesn't go and pull in much if any at all in normal off idle acceleration but does pull in advance at throttle closed or just open when exposed to the vacuum created by a motor turning at 3000+ rpm

so if you vac canister has a hexagonal section its an adjustable

tightening the Allen screw down the vacuum inlet makes it pull in advance faster and at much lower vacuum

loosening it off makes it work at higher vacuum
try loosening it off.

if you loosen it off too far you end up with no vacuum advance at any vacuum level.

Dave

Post by **MattH** » Thu May 05, 16 3:16 pm

Just had anpother play with this to try and lose the stink. I have reconnected the vacuum and backed off the initial timong to about 14. It starts alot easier than before and drives OK, no backfiring.
I did keep putting more timing in but could hear it pinking on full throttle so backed off the timing until the pinking stopped, so I have set it more by ear than numbers. Seemed Ok along the bypass.
I do wonder if I need the FBO kit to limit the mechanical advance.