SteveO
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| posted on 17/11/03 at 08:18 PM |
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spark plugs
Hi
I'm having some problems. I'm changing spark plugs nearly every week and i don't know why. I know the 40s are running slightly rich
but now the egine sounds not too good. the last few times changing the plugs sorted this. i've tried halford recommended sierra 2.0 fuel inj
plugs,champion, NGK and some cheapo ones as well. am i using the wrong fuel inj plugs on carb engine? Pls can anyone enlighten me on what to look
for.
a friend said soaked plugs is very bad news as fuel in the chamber prevents oil from lubricating the cylinder and wears out rings etc.
Steve
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Stu16v
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| posted on 17/11/03 at 08:26 PM |
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Steve, what colour are the plugs when you replace them?
Unless your engine is tuned/modified, use the plugs for that engine. However, if your engine was originally electronic ignition, and it has been
converted to points ign, you will need to adjust the plug gaps to 25 thou.
Finally, what state is the rest of the ignition system like? A knackered dizzy cap/rotor arm/ ign leads can cause symptoms like this. Replace plugs,
all will be fine for a while. Plugs soot up a bit, electricity finds an easier route to earth, i.e. through any or all of the knackered parts
mentioned above.
HTH Stu.
Dont just build it.....make it!
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JoelP
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| posted on 17/11/03 at 08:51 PM |
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at the back of the haynes manual there is a chart showing different spark plug conditions and the probable cause.
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SteveO
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| posted on 18/11/03 at 07:12 AM |
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thanks guys, the plug gaps are as the haynes manual says and they are covered by a light film of the black stuff and one is soaked- once it was plug4
now its 1. if any of the ignition dizzy and cables are bad it should show when i put new plugs as well?
Steve
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Stu16v
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| posted on 18/11/03 at 10:48 AM |
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quote:
. if any of the ignition dizzy and cables are bad it should show when i put new plugs as well?
New plugs can hide any problems of the ignition system elsewhere mate. When the spark plugs are new, they are nice and clean, and easy for the spark
to be created. As they get covered with deposits, rather than making a spark, the electric current with try and find an easier route, usually escaping
through poor leads etc. As soon as this happens, the plugs get dirtier, quicker, and big misifres set in.
As it seems to be fouling different plugs up each time, it doesnt sound like a basic engine fault. Do the carbs stink of fuel when the engine is
switched off? DO you ever get drips of fuel underneath the carbs? What fuel pump are you using?
Sorry for all the Q's just trying to paint a better picture for some internet diagnosis....
HTH Stu.
Dont just build it.....make it!
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SteveO
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| posted on 18/11/03 at 12:04 PM |
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Stu'
I'm using a manual fuel pump and now that you mention it there are times when fuel drips from the carb, i have a filter king between the tank
and pump. as i'm made to believe the 40s can with stand the pressure from the pump. but i might turn down the pressure from the filter king
knob. the cables are new from Burtons but i'll change the rotor and cap today.
Steve
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Stu16v
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| posted on 18/11/03 at 01:28 PM |
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It might also be that the float levels are incorrect, one (or both) are punctured (rare), or the float needle valves are worn (quite common).
It might be worth whipping off the carb tops to check above items.
Float level is as follows: With the gasket in place, the float level should be 8mm from the gasket with the float 'tang' just touching the
needle. This is important, because some needles are 'spring loaded' (you will know what I mean if yours is like this). Hold the carb lid
vertically and check the float height with an 8mm drill bit.
Check floats for punctures by dipping them into hot water. If air bubbles appear you have a dodogy one.
Check float needles, and see if there is a discernable wear lip on the 'taper'. If there is, they are buggered, and you will need new
needle jet assemblies.
One last thing, how are the carbs mounted to the manifold i.e. you are using the proper fitting kits-correctly adjusted?
HTH Stu.
Dont just build it.....make it!
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SteveO
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| posted on 19/11/03 at 08:58 AM |
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So the 8mm when the carb lid is held verticall should be the gap between the needle and lip thing of the float, ie the total available movement of the
lip is 8mm from fully open to close?
when i got these carbs they were on holby manifolds so i just used the spring-like washer again to mount them on the new manifold, i've heard
two different things about tightening the carbs to the manifold; some say air-tight and the guy i got them from said not soo tight to allow carb
movement.
Steve
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jollygreengiant
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| posted on 20/11/03 at 08:00 PM |
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quote:
Originally posted by SteveO
when i got these carbs they were on holby manifolds so i just used the spring-like washer again to mount them on the new manifold, i've heard
two different things about tightening the carbs to the manifold; some say air-tight and the guy i got them from said not soo tight to allow carb
movement.
Steve
Throw away the thackery washers and use the later weber system 2 X cup washers , 1 X rubber cotton reel and 1 X nylock nut per stud. Far superior
system to thackery's.
Enjoy
[Edited on 20/11/03 by jollygreengiant]
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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Stu16v
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| posted on 20/11/03 at 11:55 PM |
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quote:
So the 8mm when the carb lid is held verticall should be the gap between the needle and lip thing of the float, ie the total available movement of the
lip is 8mm from fully open to close?
No mate, the 8mm gap should be between the float and the carb lid, with the float tang *just* resting on the float needle.
P.s. As JGG says, far superior. What are you using to seal between carb and manifold? If you have a plastic washer with an 'O' ring either
side, consider replacing them for a much better solution as these are very prone to leaking/dislodging/sucking in air. Ask for some
'Misab' plates, which are an aluminium plate with a rubber 'O' ring bonded on.
Once you are sorted with that lot, I can tell you how to tighten them properly (and yes, there *should* be some movement)....
Dont just build it.....make it!
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SteveO
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| posted on 21/11/03 at 10:35 PM |
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Thanks guys, i'll check on burtonpower on saturday. Once i sort this out i'll keep ya all posted.
Steve
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mad4x4
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| posted on 24/11/03 at 02:01 PM |
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From what I've been told 40's need low pressure(5psi) at high flow and don't work well with a regulator. A Regulator noraml limits
pressure and reduces flow.
If you have a pump that gives high pressure High Flow then you'll constantly over fuel the carbs. This would give the symtoms of running very
rich.
If you run with a regulator forcing pressure down to 5 psi you may find that the flow will not be high enough and you will get fuel starvation.
Good old Catch 22.
Scot's do it better in Kilts.
MK INDY's Don't Self Centre Regardless of MK Setting !
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Stu16v
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| posted on 24/11/03 at 09:59 PM |
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I've personally never had (or heard of) a problem using a regulator as long as the regulator is mounted as close to the carbs as
possible. If the reg is mounted close to the tank, then the flow wont be sufficient.
Mounting a reg close to the tank isnt really an option with a standard fuel pump though-so no worries there. What pressure does a standard manual pump
run at? If it is 4 psi or less, there shoudnt be the need to use a regulator.....
[Edited on 24/11/03 by Stu16v]
Dont just build it.....make it!
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SteveO
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| posted on 26/11/03 at 11:10 AM |
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like a lot of builders i initially used the jetting set by the Dave Andrews jetting calculator as a starting point for the performance i wanted and
new cams. The filter king i was highy recommended, it's mounted close to the carbs and i've checked the 8mm and carb floats, all ok.
this leaves maybe rolling road and jetting maybe? i do'nt know; but anymore ideas welcome.
i'll tweek carbs and reg to minimum and see the behaviour.
Cheers
Steve.
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Stu16v
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| posted on 26/11/03 at 10:16 PM |
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The Dave Andrews guide really does get you close, so assuming you werent too generous with the expected output of the engine, the jetting shouldnt be
too far away.
Really difficult diagnosing over the 'net, but I would be looking more closely at the ignition system now....
How old are the leads/plugs/cap etc? Are you on points or electronic? Ballast igniton?
Dont just build it.....make it!
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steve m
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| posted on 26/11/03 at 10:39 PM |
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Were do I find this "Dave Andrews chart"
as I have my 40's in bits at the moment
they had been running quite rich and the plugs were dark brown, my plan Is to rebuild them , and get my car rolling roaded next year
my set up was the same as a 1600 pinto, even tho ive got a 1700 xflow I have been told that the differance would be minimul,
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UncleFista
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| posted on 27/11/03 at 01:11 AM |
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here 
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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steve m
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| posted on 28/11/03 at 12:56 AM |
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thanks for the link
good fun
but also depressing as ive only got 34mm chokes
steve
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SteveO
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| posted on 28/11/03 at 12:58 PM |
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Stu16v,
i've got the cup washers and rubbers now and i can see why there are soo much bettter than the old spring washers , but where can i get the
'Misap' ali' plates to go between the carbs and manifold?
Steve
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Stu16v
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| posted on 28/11/03 at 05:54 PM |
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Almost any decent tuning supplier will sell Misabs mate. Try Demon Thieves, Burton Power etc etc.
Dont just build it.....make it!
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steve m
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| posted on 28/11/03 at 08:53 PM |
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were do I buy thes fab washers' as Ive still got the old thackery ones and half of them were broke
steve
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Stu16v
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| posted on 28/11/03 at 10:06 PM |
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Same places mate.......
Dont just build it.....make it!
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