Quick question before purchasing

[chrisb]

Evening people

well I’m back on the 40’s ..
ive purchased another MATCHED pair of dcoe 31

if you all recal from my last request I had a miss match pair.. which are going up for sale as single units ( spares etc )

So the engine
1640cc ( using 1300 pistons )
cortina GT spec head ( ported & polished )
fast rd cam ( unknown spec )
vac-less dizzy .. side exit cap .. ( converted screw-on )
( the cap isn’t a perfect tight fit .. which does concern me a little )
motorcraft type dizzy

the carbs

using a synchroniser I’ve balanced the carbs to each other then balanced each barrel

twin 40 dcoe 31
32mm chokes
4.5 aux
mains 130
airs 180
F16 tubes
pump 40
idle 45f9

the car now with the replacement carbs pulls well doesn’t hesitate unlike the old ones..
HOWEVER is a bugger on tickover .. engine surging up and down the Rev range ... revs high so I reduce the tickover ... it steady’s but then rises again
l’ve tried altering the ( four ) idle screws but they don’t seem to have much effect

im unsure if you screw them in to richen or weaken ?

My thoughts are the idle jets .. but what do I go for 45f8 ???

This is just to get it as close as I can before booking a rolling road set up ...

and whilst I’ve mentioned that any recommendations for a good one in the north west Manchester area

thanks Chris

[Graham]

screwing the idle mixture screw in leans the mixture, but only when the throttle is shut, if something is holding the throttles open slightly they will have little or no effect

[chrisb]

Hi Graham

I even disconnected the throttle linkage rod just to check it wasn’t holding them open
But the linkage actually holds the throttle shut until the pedal is depressed
There is slack in the cables

[Graham]

when you say you have balenced the throttles what are you adjusting?

[chrisb]

when you say you have balenced the throttles what are you adjusting?

With the engine warm I set the 2nd carb (screw) that connects to the 1st carb linkage .. with the balancer I adjusted this screw until both inner most trumpets had the same reading ( approximately 7 on the gauge )
Then I then adjusted each mixture screw unit each barrel was reading the same ..
I got the ticking over ok ... but then the revs increased as the engine got warmer ... so I reduced the main throttle screw ... engine slowed.. but after a minute or so it stalled

I’ve checked for air leaks with a quick spray of brake cleaner with no increase of revs ...
checked I’d NOT over tightened the carbs ( grabbing each carb body there is slight flex ) so they are not bolted up tight.

[Graham]

you dont set balance on the mixture screws! once you have set the balance on the linkage thats it, done. then once by one adjust the mixture screws to get best/fastest idle, you may then need to slow the engine down and repeat the idle mixture adjustment

[chrisb]

I’ll give that a go thank you .. watching too many duff information YouTube videos

So you think the idle jets should be ok then ?

As I say I am going to get it on the rollers , just want to at least half right ...

Next step is finding a tuning rolling road that still understands carbs

[Graham]

45f9 should be ok

[chrisb]

45f9 should be ok

Hi Graham ,
I had quick look tonight whilst trying not to upset the neighbours raving it too hard
I got it ticking over nicely using the method you said
Get a spit / click every so often..
I did a video but it’s too large to upload

Get a nice clean rev ,BUT .. the engine takes a while to settle again , seems to hold the revs up .. not wildly high
But not , tick-over speed

Too rich ?

Thanks for your help
Chris

[Graham]

probably a bit lean, lean tends to spit and hold revs up because you need the idle mix screws a long way out to keep it idling