richardh
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| posted on 7/4/12 at 08:36 AM |
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V8 running then under load tries to stall
HI,
My v8 is having some issues.
Starts fine, idles ok and can blip the throttle fine right up to 4k revs.
Took it for test drive round the field and it ran fine for 1/4 mile then started to want to die on me whilst under acceleration.
New fuel, new pump, engine compression tests ok, fuel in tank, no blockages or leaks.
Tank has a breather pipe
Its running on a single holley (which i know nouwt about)
Any ideas folks.
Smoke from rear is coming out light grey-ish
Ta, Rich
Time for a change!
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craig1410
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| posted on 7/4/12 at 11:26 AM |
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What type of distributor does it have? If it's a Lucas 35DE8 then it might be broken wires on electronic ignition amp. What sort of misfire are
you getting? Complete shutdown or regular or irregular misfire?
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Neville Jones
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| posted on 7/4/12 at 12:01 PM |
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Is the carb a four barrel?
Does it have side pivot or centre pivot floats?
Nev.
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richardh
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| posted on 7/4/12 at 01:53 PM |
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i'll need to go check the make of the dizzy.
no idea on the carb or floats
its a holley and thats as far as i've got 
not so much of a misfire but just it wants to stall
Time for a change!
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craig1410
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| posted on 7/4/12 at 02:32 PM |
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Hi Richard,
Just to be clear what you are experiencing, when you say "stall" that to me means that the engine is stopping when at idle but the fact
you say it happens under acceleration suggests it is not stalling at idle but (in my words) is completely losing power for a period of time then,
presumably, running normally again.
So, would it be correct to assume that the engine idles fine and generally runs fine but sometimes completely loses power when accelerating? Does it
ever happen at steady state (ie. when cruising) or does the engine ever shut off at idle?
If it is only happening under acceleration and is a *complete* loss of combustion then I'd say it was ignition related because carbs generally
don't cause the engine to completely shut off without having a bit of irregular misfire thrown in either just before or just after the loss of
power. The carb could be delivering a mixture well outside the "normal" ratio and still cause at least some combustion to occur.
So, assuming it is an ignition fault, I'd suggest checking the low tension (voltage) side of things because, again, the high tension side (plugs
& leads) would tend to cause a regular (eg. 1 of the 8 cylinders) misfire rather than complete loss of combustion. Having said that, the ignition
coil could be breaking down internally which might cause complete loss of power but I'd say that is less likely.
So, check all your low voltage wiring including the coil low tension connections, ballast resistor (do you have one?) and ignition amplifier (inside
or outside the dizzy depending on type).
The more info you can give (along the lines described above) the more accurately we can try to diagnose the problem.
Cheers,
Craig.
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richardh
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| posted on 7/4/12 at 02:38 PM |
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thanks,
i've no idea on how to test this stuff.
all wires look ok and go to the right place.
timing is fine and the plugs new and leads fine
That's the limit of my testing knowledge i'm afraid
I'll google your suggestions and see what it says.
Cheers
Time for a change!
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craig1410
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| posted on 7/4/12 at 02:53 PM |
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Hi,
No worries, just make sure all connections are clean and secure with no signs of broken wires (the wire will crease with PVC and feel
'floppy' at the break). Disconnect and reconnect them a few times each to self-clean the contact surface. If its dirty then use brake
cleaner or meths to clean the connections.
There are pictures of some of the different dizzys on this page: http://www.v8engines.com/electrics-1.htm
Do you know if you have a ballast resistor? It will look like this: http://www.rimmerbros.co.uk/Item--i-DRC1638 and will be near the distributor.
It might come down to swapping out some parts to try to find the culprit. There might be a locostbuilder in your area who could come over and try to
get a better idea what is wrong.
Cheers,
Craig.
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rusty nuts
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| posted on 7/4/12 at 03:17 PM |
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Your symptoms sound like you could have a flat spot due to the accelarater pump not being set up correctly , if it was ignition I would expect it to
cut out completly although I once had a Golf that cut out on accelerating but would cruise OK, that turned out to be a partial break in the points
wire and disconnecting the vacuum advance got it home . As said already stalling is normally when the engine is idling or just starting off not when
the engine speed is above idle, Is the engine cutting out completly? Do you have an air leak ? Does the engine only rev to 4,000 rpm?
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coyoteboy
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| posted on 7/4/12 at 04:44 PM |
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Not sure on the dizzy on these but could it be a vac advance line split? I had similar near-stall issues on an old car only under load when the vac
advance diaphragm split.
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RAYLEE29
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| posted on 7/4/12 at 05:46 PM |
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Hi could be worth checking your fuel heights in the float bowls this is externally adjustable on the usual holleys fitted to rv8s theres a brass plug
(on the side of the bowl)you take out when the height is correct fuel just starts to dribble out the height is adjusted by altering the height of the
needle undo the locknut (on top of bowl) and screwing up or down a little at a time (1/2 turn).
also do you have a fuel pressure regulator on there holleys dont like too much pressure.
if your going to stick with the holley then get a book as youcan adjust almost anything on them.
another thing to check is the oil pressure, standard fitment for sd1s had a fuel pump cut off for low oil pressure if its wired in and you lose oil
pressure the you lose the fuel pump.
hope this all makes sense.
Ray 
build diary1
http://picasaweb.google.com/raylee290/RoadsterPics#
build diary2
http://picasaweb.google.com/raylee290/KITCARPICS?authkey=Gv1sRgCI2AouyYgpuQmAE#
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richardh
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| posted on 7/4/12 at 05:48 PM |
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ok, my dizzy looks more like this type (middle pic from linky) Lucas 'Limb' system 35DLM8
No ballast resistor apparent
Cleaned contacts, checked fuses, wires, connections, earths, etc
Guess i need to start stripping the carbs down now.
Or let someone who knows what they are doing do it at least.
re the revving, it will rev past 4k idle no problem, only under drive will it stutter past about 4k ish.
If i can get into 3rd then it seems to want to pull a bit more but again as i go through gears and accelerate, it wants to starve itself of fuel (only
way i can describe it)
Time for a change!
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richardh
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| posted on 7/4/12 at 05:53 PM |
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i had a fuel reg on and set it at stages between 1psi and 4psi (think it was psi's)
took it off after i saw it idle and then fuel was pouring out of somewhere in the holley and all over the valley gasket.
After running it it still seems like its been wet from fuel leaking out of holley somewhere but at idle and stand-still revving i cant see anything
leaking anymore from anywhere
Time for a change!
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