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308 dodgy acceleration

Gday boys

for a while now i've had this dodgy acceleration and i've tried everything i can think of so its time i ask for some advice.

set up i have is blue 308 running a fresh rebuilt quaddie jetted for 308(from sues carbs, i assume they jetted it correctly) with a cable throttle linkage

what happens is if i give it about 50% throttle it accelerates nicely.
if i keep the pedal going down to 100% WOT it bogs and when i back off to 50% again the acceleration picks up again.

what i've tried so far;

-made sure that the pedal when pressed to floor opens carby 100%
-made sure the carby is nice and snug to the inlet manifold and i used a new gasket between the 2. im pretty sure ive blocked all vacuum holes that aren't in use.
-quite sure i'm not getting wheel spin as i'm running an lsd with tyres that are quite chirpy when they do spin so i would hear it.
-clutch and pressure plate are quite new, tried the old handbrake on and pull the clutch out and it seems to be not slipping at all
-i'm hearing no grinding or crunching in my w50 and the box was just opened up and had new bearings put through- gears were great and the problem also happened pre-gearbox rebuild
-a mate of a mate of mine with a performance shop set the timing and set up the quaddie so i assume that's right as he's a Holden man and knows his stuff.

Ok so any ideas??? It's really giving me the sheets


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take it back to the

take it back to the performance shop because he knows his stuff.

WHAT? no gravy?

308 boggy

agree with dave, or:

remove the carby top and check jet/rod sizes for yourself

check timing for yourself

so many times i have fixed cars that have been set up by "guru's" at a very high cost - and oh-so often it is something very simple

one such 308 problem i recall was in a torana, guy rang me and was prepared to shell $4K+ out for a new engine over the phone, as his was at 080" oversize and he was convinced this was the cause of his overheating. he had been to 5 different workshops

a few minutes chatting with him had me convinced i could at least check it out first - end result was a combination of seized dissy advance mechanism, incorrect thermostat and incorrect fan set-up was all it took to cause high temperatures.

a few hours work to solve the above problems and turn the "crook" engine into a cool running, strong performing engine again, all without the need to even remove the tappet covers.

moral of the story - TRUST NO ONE!!!


thanks dave and ben.

Ben, do you reckon it sounds like dodgy timing and tuning?

Where are ya located? Maybe you can be the new guru(paid) to tune my 308?


My Shed

perth mick

mick, unless the perth in your sign on name is your surname then im afraid we are at opposite ends of the country lol!

as a side note - sometimes just to diagnose you can run a hot wire from the battery to the coil + and see if thats the cause. only problem is if you need to turn it off you will have to remove the wire.


no worries

i'll run a new wire to the +, it had a join in it and i meant to redo it a while ago anyway.

I think curly might be right with his diagnosis. Now that i think back it might have started when i did the conversion with my 253 before my 308 and it is the same dizzy.


My Shed


MICK I had this exact drama with the 4x4sandman, would accel at half pedal but be a bitch at WOT. I bought brand new carbys and so on, couldnt fix it. Experts misdiagnosed it, told me jets and stuff. THE FIX WAS that I was running electronic ignotion from wb v8 powered by my HZ ballast wire. The ballast wire always read 12v when cold, it reduces current as it heats up. I re gapd and checked my plugs to match the electronic dizzy and ran a 15a wire to my coil from somewhere on the upstream side the fuses from a "on" position on my fuse panel, and, bugger me, no more fireworks at WOT. (wide open throttle)

This is guessing that your running an electronic dizzy in your HQ, so wack a fresh wire on to the coil.


All that I have left to do is everything.

Curly my man

i do have an electronic dizzy from a blue engine in my 308.

i did the old join the pink wire to the main feed wire to by pass the stainless resistor wire(cant remember the finer details it was a while ago)

i thought i did it all correctly

so basically all i have to do is run a 15a wire from further up on the ignition switch? Can you recall which colour it was mate?

Cheers for your help.

btw im back in Aus now, how did your front end project go?


My Shed


I ran mine from the fuse panel. If you have the time by all means run it from the ignition switch, Just look for the other end of the ballast wire! From memory I ran mine from the fat pink wire on the back of the fuse panel. There are some spare terminals on there you can plug into. Do a test, before you unbolt the colum to get to the ignotion switch. Run your new red 15a wire from this pink wire so you can see if it runs better. Make sure it turns off properly before you drive anywhere! Have a gander behind the fuse panel and get your multi meter out and just check for the right power at on and start and not at acc or off!

Of yeah, the stuck bush! I got it out with fire drill and grinder. I have all the new bits there to go back on but im up north so all I can do is think about it whilst im building barrow island. First thing to do when im back is get the chassis blasted, painted and then I can screw stuff back on. Cant wait. Rain permitting.

T, mine redlined, as far as i could hear, and still did this. As far as i could hear, again. It was loud. Curly.

All that I have left to do is everything.


cool mate, ill do that and see how i go, hopefully that will sort it, i'm hoping for a smile when it reacts properly to WOT


My Shed

Further Redline RPM

"T, mine redlined, as far as i could hear, and still did this. As far as i could hear, again. It was loud. Curly."

Isn't that consistent with what I'm saying? The Engine made Redline RPM in Neutral, confirming you *didn't* have a Fuel Supply problem.

You had an Ignition problem, which manifested itself when the Car was in Gear and the Engine loaded.

It's easy for a Spark to occur in an unloaded Engine.
It's hard for a Spark to occur in a loaded Engine.


My Shed

Holdenpaedia, they're the brakes Mate.

Oh yeah, I mis-read your

Oh yeah, I mis-read your line. Sorry bout that T. I was excited. I cant read good when im excited. Thats a good tool to remember.

All that I have left to do is everything.

Redline RPM

If it will make redline RPM in Neutral it's not a Fuel problem it's an Ignition problem.


My Shed

Holdenpaedia, they're the brakes Mate.


Sounds like an issue with the vacuum brake on the secondaries.
With the engine running, make sure the top butterfly's (vacuum brake) is closed and can hold pressure when you try to push on them.
They also need to actually open when the throttle is pushed passed half way, there is a small lock that prevents the secondary's opening when the choke is not off 100%, check that too.
The idea behind the vacuum brake is that they control both the vacuum sent to the fuel supply, and the metering of the fuel supplied to the throats.
If they don't open, they won't deliver the right amount of fuel and restric the air flow, if they open without resistance they will not allow the vacuum to suck the fuel from the fuel supply pipes and will give it a gut full of air.
Quaddies are fantastic carby's, but you need to know how to work on them.


Dislike me for who I am you may, like me for whom I'm not, you never will...

arsewipes diagnostics

gday mate sorry for the late reply.

when engine was running i pushed the butterflies and they wanted to stay closed, the lock also worked, i noticed when the engine was off(and obviously no vacuum was present in the diaphram the lock didnt engage so it sounds like its doing everything you said it should.

i also did the choke thing which seemed to be ok since the choke flap is in open position when warmish.

i checked the dizzy was getting enough power(used method 2 in the refurbishing guide where you run a new seperate wire)

only thing i havent checked now is the dizzy, i did rebuild it according to the guide and it seemed to be ok. the vacuum advance also seemed to work(did the old depress the diaphram with the rod and cover the hole and it held its pressure.

maybe its got something to do with the small crack in the stator in the dizzy?


My Shed


Make sure the diaphram that operates the secondary chokes is ok, holds vacuum and operates as it should.
It still sounds like a fuel delivery issue, can you see the small lock out that holds the secondary butterflies closed, it's on the main throttle shaft and is connected to the primary choke, it will not allow the secondaries to open at all if the choke is not completely off, another thing to look at is fuel pressure and float levels.
Most of the adjustments on the quaddie are made by bending things, so adjustments are different for each carby and normally require an individual set up on the vehicle.
The carbies are quite unpredictable and require a fine touch to have them tuned to perfection.
Failing all that, do you have access to another carby to try to rule out that area?


Dislike me for who I am you may, like me for whom I'm not, you never will...

fixed or not?

well last night i snipped my link from the pink to yellow, soldered a nice fat red wire to the nub left, ran it through the firewall and connected it. Method 2 for anyone thats got the bosh electronic dizzy rebuild tutorial(masterpiece)

so i started it up, went down the road and it seemed to bog a little but i think its because it was cold(didnt give it wot)

anyway got on the highway and booted it but my tyres are so [Naughty Pottyword] it just keeps spinning in any gear.

i hope it has fixed it but ill have to wait until the road dries so i can tell.

it seems to sound a bit stronger on idle


My Shed

it just keeps spinning in any gear

...Showoff... ;P

I wouldnt mined if mine could do that even while it was playing up...

If it starts knocking.... Turn the stereo UP!!
My Shed


like i said tho wet road and [Naughty Pottyword]ty cheese cutters, i reckon a wippersnipper motor could spin my tyres in the wet


My Shed

hows the ute going? have you

hows the ute going? have you got any traction yet? Im sure spinning the tyres at 140mph means its fixed, how ever thin they are.

All that I have left to do is everything.


took it for a spin to rocko today, seems to be marginly better but unless its at 100% running temp i'll still get my weird reduced acceleration from 50%-100% throttle.

i think its time to check the things out on the carby the other blokes mentioned.

i really wanted your idea to work, was the simpler of the 1 million things that could be causing it

i rebuild the dizzy following the instruction i mentioned before, i noticed the strator magnet had a crack in it, not sure if that made a diff but ive got another electronic dizzy here ill rebuild and chuck in and see whats happening there. ive also got an engine tick that might be coming from the dizzy(well i hope so- 2 birds with 1 stone!)

next time im in your neighbourhood i can take you for a drive and you can see for yourself if ya want?


My Shed


It would have been nice with such a simple fix, but alas, its not always the case. I find when im chasing and fixing things I do more than one thing at once and I end up not being able to excatly determin what was wrong. I guess im just impatient.

Im up north till the 29th, but after that yeah drop by. flick us ur email.

All that I have left to do is everything.

To also add to arsewipe's

To also add to arsewipe's comment...check that your choke flap is fully open with the engine at temp.
If your choke was set up should be almost closed (not fully) when dead cold.Fully open when hot.
If its not set right,the choke locks out your secondary throttle plates.
So check and make sure.

It could be just me, but we

It could be just me, but we dont really need chokes in w.a. I have never used one on an OH in 14 years of owning them. Not usually cold enough.

All that I have left to do is everything.

quaddie choke

i just started my ute, been running for a few mins and the choke is open, its not at running temp- barely eveen gone up 1 incriment o my gts temp gauge. if i press on it wants to be in the open position. when the engine was more cold it would half assed stay between both.


My Shed

problem solved!

i had my vacuum advance hooked upto the wrong line on the carby so it was always advanced and never got more advanced as the revs went up.

bloody eye opener when i put my foot down now


My Shed

So simple! The ute runs good

So simple! The ute runs good yes? I guess a timing light would have been useful here with finding this one.

All that I have left to do is everything.


yea runs sweet mate, throws me back in the seat and puts a smile on my face.

ill still take ya for a drive when ur back in town.

what do you do for a crust in barrow?


My Shed

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