70 GTX takes too long to start

[rumblefish360]

Sounds like it’s time for an electric fuel pump to get that fuel delivered quick and easy. Your starter will love you for it.

 

[polyjohn]

Hi El Toro,

Good to hear there is another 70 GTX in Surrey!
My Moparmate Jim Chandler had one since the 80's in Cheam village.
Cool car and he drag raced it for many years, running 11 seconds dead!
I owned it for a while and he restored it in the 2000's.
Someone in the MMA owns it now and it looks superb in Burnt orange.

I have a 71 GTX too and its got a 'sixpack' coming very soon lol.
Its off of a 70 sixpack Challenger near you in Weybridge.
Its a non vacuum set-up for drag racing so he's buying a complete new set up from Holley.

I had a sixpack back in the 80's and it was a mare for cold starting and after a long winter!
If the carbs are 'old' originals then it could be a long haul...

I would always fit a new centre 500cfm as 50 year holleys are troublesome at best.

best wishes from Kent John H.

Jim's GTX at Brooklands and my mates Polara behind with a 512ci big-block coolio...

 

[polyjohn]

Hi again El Toro,

The 70 GTX is a high compression engine!
It will not run on unleaded (low octane) without damaging the pistons.
E10 is poo fuel and may hurt the pistons.
I would only ever use Super-unleaded with octane booster if needed.
Apparently Esso is still 100% petrol '99-octane' with no additives?

A compression test is needed to find out your cylinder pressures to see where you are at?
High compression can be 'bled -off' with a big camshaft.
The mistake they made with Pauls 70 sixpack was high compression pistons, and a small camshaft.
After many attempts to get her to run properly, all that happened was 'engine failure'.

The pistons are totally destroyed only after a few hundred miles.

 

[polyjohn]

David's 512ci engine in the Polara (daily driver) lol...

 

[Ranger16]

I believe it needs to be fully closed but soon as the car fires off, the choke pull-off will crack the plate about an 1/8 of an inch.
there is an adjustment rod to set the gap with.

if you live in a very warm climate - the cold choke set like in the picture will likely work ok.

Hmm................ Well I was going by the Edelbrock manual with the 1/8" gap, but I will have to try the "full closed" next year as mine takes longer to start than I think it should as well.

 

[polyjohn]

Hi again,

The problem I see with most high compression engines is 'cylinder burnishing'.
Its like bore wash from too much fuel going past the rings, but much worse.

Cold cranking is a bad time for any engine, it should start asap, or you are causing damage.
Pooring fuel down a carb is asking for trouble and only used in an emergency.

If there is fuel and a spark, the engine will fire!
If its not firing, something is wrong...

Lack of fuel is obvious if you look at the carb when pumping the throttle.
Lack of spark or incorrect ignition timing is not so obvious...

If you go into A12 discussions, there is a full description on six pack carb set-up.
It shows that All three cabs are necessary for idling and are crucial for good fuel air mixture...

 

[oldbee]

Hmm................ Well I was going by the Edelbrock manual with the 1/8" gap, but I will have to try the "full closed" next year as mine takes longer to start than I think it should as well.

Sometimes if choke tension is not enuff the pull off starts to do its thing and the plate opens too far.Not enuff tension lets the choke plate open too far just from air rushing down venturi's.

 

[Ranger16]

Maybe I'm wrong, but it just seems to me that a fully closed choke would literally choke off the intake and prevent the engine from starting.

 

[toolmanmike]

Maybe I'm wrong, but it just seems to me that a fully closed choke would literally choke off the intake and prevent the engine from starting.

No. It is proper adjustment for it to close until the engine starts. Why have a choke if it doesn't close. One set too lean (open even slightly when closed) makes it hard to start.

 

[72ls5fla]

Maybe I'm wrong, but it just seems to me that a fully closed choke would literally choke off the intake and prevent the engine from starting.

soon as the engine starts, there will be enough vacuum to activate the choke pull-off and the choke plate will open slightly.
raise the rpms and it will open further.

 

[toolmanmike]

Maybe I'm wrong, but it just seems to me that a fully closed choke would literally choke off the intake and prevent the engine from starting.

In California abcause of the warm temps they adjust the choke so the butterfly is almost closed. What he says and does are 2 different things.

 

[Mopewbie]

You really need to know if the choke is closing all the way when the engine is cold. If is sits for a few days then fill the center carb through the bowl vent.

Don’t pump while cranking, it will open the choke. Also will help it to go lean and backfire through the carb destroying the power valve,

Been out yesterday, 2 pumps, all good straight away, that never happened before. LOL.

Didn't know about the pump while cranking really, good to know. Maybe previous owner had no idea either and decided to not touch anything so passed the info over, who knows?
Probably I was doing that wrong as well since I got bored of just cranking and pump the pedal messing up the choke.

More tests to come but what a difference already.

Thank all.

 

[440+6]

I wonder why a choke and its function is such a mystery to so many?
So much misinformation..?.......

 

[Gygeneral]

With my six pack, if its been longer than a week that it has started, I poured some gas down the vent tube on the center carb, and it fired up instantly. If I didn't do that is would take a lot of pumping and cranking. I think in my case the fuel evaporates from the bowl that 's why you have to pump a lot. Try it see if it starts right away. I used a syringe to squirt fuel in the tube. I used 3 full syringes worth of gas

 

[Ranger16]

No. It is proper adjustment for it to close until the engine starts. Why have a choke if it doesn't close. One set too lean (open even slightly when closed) makes it hard to start.

OK, I'm gonna have to readjust and try it again in spring, but we all know that an IC engine needs 3 things, fuel, spark and air. Again, I may be wrong, but it seems to me that with the choke completely closed, you are eliminating one of those three things. What am I misunderstanding?

 

[toolmanmike]

OK, I'm gonna have to readjust and try it again in spring, but we all know that an IC engine needs 3 things, fuel, spark and air. Again, I may be wrong, but it seems to me that with the choke completely closed, you are eliminating one of those three things. What am I misunderstanding?

Yes. . It get's air but it needs a rich mixture to start. As soon as the engine fires the butterfly will open just a crack to prevent flooding. The butterfly, like they mention in the videos, is set to "just close".

 

[R413]

The choke needs to close completely with engine off. You have to press the pedal so the choke can set. It is spring loaded.

when the engine starts the choke pull off is to open the choke plate approx 1/4 of the way so it can run. It is operated by manifold vacuuum so when the engine starts it should open of working right. You adjust it by bending the linkage.

 

[turbine68rt]

Maybe I'm wrong, but it just seems to me that a fully closed choke would literally choke off the intake and prevent the engine from starting.

I can tell you one thing for sure, with my completely stock 440 if the choke is opened at all (cold), even a small amount, there's no telling when it will start. Fully closed it will start in a matter of seconds.

 

[dadsbee]

Glad to see some others here that remember Winters in these cars! You also have to learn each and every one of them, as they all generally like something different to start.

 

[Ranger16]

OK, you guys have convince me. I'm going to readjust the choke (full closed) and see if that makes a difference.