Flat spot

octanejunkie · Post by **octanejunkie** » Thu Mar 30, 17 4:19 pm

Had a mess about today, and got a better vacuum. Much, much better. Still slightly flat and i think theres more to come though..

Can someone explain to me how needle valves work, as i think this may now be the source...

Post by **MattH** » Tue Apr 04, 17 9:43 am

octanejunkie wrote: Can someone explain to me how needle valves work, as i think this may now be the source...

Do you mean the float valves?

octanejunkie · Post by **octanejunkie** » Wed Apr 05, 17 8:43 am

I meant metering rods.

Still can't get the car to run right!! Arrrgggh.
Been trying to tune it for the last two days. Still bogging off idle. Gets better when warm. When its cold, it really coughs.
When i get home from work, with the car warm, i make slight adjustments, then go for a spin up the road, and it goes really well for a minute or two, then the stumble/bog/flat spot slowly returns. Seems like its better with the air filter removed. I've been doing loads of research, and i think everything is set as good as i can get it.
Would timing cause a flat spot like this??
Doing my head in now

octanejunkie · Post by **octanejunkie** » Wed Apr 05, 17 8:48 am

Starts instantly, hot or cold. Runs well on the choke.

When you rev the engine from the engine bay it sounds like theres a little "hole" or delay just as you rev it.

Trying to give as much info as possible, so forgive my descriptions

GJUK · Post by **GJUK** » Wed Apr 05, 17 10:44 am

bigger jets, more fuel.

octanejunkie · Post by **octanejunkie** » Fri Apr 07, 17 9:09 am

Ordered a new inlet manifold gasket (fel pro). Had a bit of oil around the front of the manifold where it meets the timing/water pump cover.. No other signs of it blowing and vacuum is very strong at tickover, but i guess its worth a try.
Also forgot to mention that the exhaust chuffs a bit at idle.

Seems to idle ok, but it goes kind of.... "glug, glug, glug, glug, pffft, glug glug, pffft, glug, glug, glug, glug pffft" No pattern to it, just seems random, both banks. Got the idle jets set about right, but can't dial out the "pffft"..

Anyone had or heard of this???

Blue · Post by **Blue** » Fri Apr 07, 17 9:37 am

You need to sort out the timing first, you'll never get it running right unless you do that. My mate already set it is not the correct answer here....

octanejunkie · Post by **octanejunkie** » Fri Apr 07, 17 10:30 am

Blue wrote:You need to sort out the timing first, you'll never get it running right unless you do that. My mate already set it is not the correct answer here....

I haven't had a "mate" set the timing... I had it set at a local garage when i fitted the new carb, though how much knowledge they actually had about Mopars is pretty limited i think! I don't know what they set it at though. Didn't make any difference.

Blue · Post by **Blue** » Fri Apr 07, 17 11:05 am

What I was getting at is unless you've gone through the timing procedure yourself it will be wrong, guaranteed.
I'll explain why, the figures quoted in the workshop manuals are donkeys years out of date, you can not buy the fuel they were using then, those figures are meaningless now.
What anyone who wants to get these cars running right has to do is find out what timing thier particular car needs, there is no given figure. The fact that this takes some effort and a few hours time is why no mate or garage is going to spend that long doing it assuming they even know what to do. There was a sticky on how to do this but it seems to have gone? anyone have it saved? we really need it back there, and the carb tuning one.
Getting the timing right doesn't require a high level of skill but you do need a decent timing light with an advance knob, some patience and probably half a days time to do it. Once done it's done and your car will run so much better for it.
You know those products that offer more power, better running, less MPG and cooler running? it's all cobblers right? Getting the timing spot on will do all those things and it's free.....

Adam · Post by **Adam** » Fri Apr 07, 17 12:52 pm

Once you've set the timing...

Check the operation of the accelerator pump. Does it squirt a steady stream into the carb throats when you operate the throttle linkage? Do this without the engine running.

Get a mate to follow you and observe whether any unburnt fuel comes out the exhaust (will look like black soot) when you get on it.

If it does, it's dumping too much fuel into the motor, causing it to stumble.

If it doesn't puff any soot out of the exhaust, it's not getting enough fuel to match the sudden increase in air flow.

I'm not familiar with the 2 bbl carb, but there may be an adjustment on the accelerator pump - maybe 3 hole positions for the lever that actuates it?

octanejunkie · Post by **octanejunkie** » Fri Apr 07, 17 1:22 pm

The only adjustment on the Carter 2bbl is via a sleeve on the actuating shaft with a philips screw to set the cam to operate the pump when you accelerate. There is also some adjustment via the metering rods.

I've got a nice strong squirt of fuel in both barrels from the pump, so am pretty sure this isn't the case.

I'm gonna have a stab at the timing and see if it needs further advancing.

Adam · Post by **Adam** » Fri Apr 07, 17 4:54 pm

Disconnect and plug the vacuum advance, then set the timing to around 36 degrees "all in". That should get you in the ball park.

Reconnect the vac adv pipe, and adjust that cam on the accelerator pump to give you more or less of a shot as required.

Good luck

Blue · Post by **Blue** » Fri Apr 07, 17 4:55 pm

I'll quickly run through the process to give you an idea of whats needed. Get the engine up to operating temperature, remove the vacuum hose to the dizzy and plug the carb end. Slowly increase the timing until the tickover revs just stop going up. Lock the dizzy off at that point and switch off the engine for about 10 mins. Start the engine, if the starter is labouring knock out 2 degrees and try again, keep doing that until it starts without labouring. That will be you initial timing figure sorted so make a note of how many degrees that is. Now you need to slowly increase the revs watching the mark until it stops advancing which could be as high as 4000 rpm. Make a note of how many degrees total advance you are getting. You want no more than 34 degrees at this point and you will likely have more than that now. You now need to remove the dizzy and limit the advance slots to get the initial figure you've arrived at whilst not going over 34 degrees total. There are a couple of ways to do that when you get to that point.