engine rescue team needed!! HELP

[antonio]

all, hi
to follow GC recommended jetting, i changed main and air jets on my 2xdcnf's.
but i don't know why, my engine sudunly runs on 3 or2 cylenders!!
i'm not sure it's because i swapped jets...i know air and fuel mixture must be tuned again, but engine should still runs on is 4 legs!!
recently, carbs and ignition were tuned by a "man of the art".engine was rebuilt with new head (new valves, guide...)new rings, balanced shaft and flywheel, so engine is supposed to run nice!?oups, carbs were bought from new, so sure they works fine.
plugs were swapped, they are all good.
the strangest thing, is that cylender number 4 sometimes runs, sometimes not!!this mornig it was number 3 to be out of order!!
i suspect my ignition to be faulty, be i do have spark on plugs.
i was also thinking about a faulty ground on head or engine, because depending on braking or if i turn hard, engine work bad or very bad.
i've noticed a strange noise, as if i was able to hear spark noise!!of course wire are new and well plugged.
i hope someone would have found bravery to read up this last words.
antonio

[Cousin Cleotis]

Check for air leaks.

Good luck,

Paul

[Guy Croft]

to follow GC recommended jetting, i changed main and air jets on my 2xdcnf's.
but i don't know why, my engine sudunly runs on 3 or2 cylenders!!

Why are you connecting my jetting advice with your misfire?!
Do a compression test and buy a Gunson 'Colortune'.

GC

[antonio]

guy, sorry if i offence you, it was not my purpose.i connect jetting and misfire because i don't know if changing jets include re-tune carbs.
what is a Gunson 'Colortune'. ?
i'll try to get a compression test tomorow.
english is not my language, i'll do my best to explain myself, but sometime....!sorry

antonio

[antonio]

i know what a colortune is now.
is it possible that a carb is completly silly because of jets change?
guy, if my comperssions are good, would a bad mixture cause complete misfire for the two cylinders?
if my carbs are sychronized, will i be able to tune carbs just with "colortune"?
regards
antonio

[sumplug]

a
Are the carbs set right.? Have you checked the fuel flow to both carbs.? Hope you have plumbed them in correctly? Open the top of the carbs, is the float moving freely and chamber have fuel in?
Have you got an airleak at the manifold? Try some washing liquid around manifold for a temporary seal.
Take plugs out, are they fireing?
What ignition system are you using??
Are you using the right manifold and carbs sitting in correct position??
Have you got a plug tester to use in between the plug and lead? This will determine spark.
Something to think about.


AC.

[antonio]

hi
thanks for advices
now, i'm sure compression are good, i've cheak i have no leaks, good sparks and fuel arrives on both carbs.
i've bought "colortune", and carbs appears to be badly set!it's surprising as they were tune 1 mounth ago.maybe it's because i change main and air jet...
when i did carbs convertion, i was adviced to use a pressure regulator.i bought a KING regulator , but do i have to change fuel pump too?
the best pressure i can get is 0.4 bar, is it enought?
regards
antonio

[Guy Croft]

Antonio hi

Now you are learning!

0.4 bar is way too high, you need a pump that produces 3-4psi max ie:0.25-0.28 bar max or the fuel pressure will lift the float needles off the seats. Don't rely on a Filter King to take the pressure down from 0.4 bar (nearly 6psi) to that low level, they are not that accurate.

I strongly recommend the Facet Silver Top 'Interrupter' (not the competition version in thise case nor the cheaper solid-state version) type pump, without regulator, just an in-line filter.

GC

[antonio]

sure i'm learning!! :shock:
why do i always find the worst mecanic to do job i'm not able to do??
how is it possible to run a workshop when you advice your customers to run weber with 0.4 bar mini??? :evil:
this F. man told me i should change my fuel pump to something more powerfull!!i imagine fuel would have burst my carbs!
ok, another 100 euros spent for nothing (king+ manometer)this car will lead me to bankrupt

thank for advice guy and tell me if you have a friend who can tune carbs in north of france, it would help me to spare money, time and bad nights!

[Dynodave]

Antonio ,
have you checked that the carbs are balanced correctly?.
Because cylinders 3 & 4 are on the same carburettor its possible that its not open as far as 1 & 2 cylinders carb.this would cause both 3&4 to be prone to dropping out ie not firing properly.
Its worth checking.