Weber 45 DCOE air leak

[Mk2Neil]

Hi all,

Just fitted a pair of twin 45 webers to my pinto mk2 Escort. They had the standard weber jetting and all i have done is changed the choke sizes down to 34mm. Bought the carbs already bolted onto the manifold and fitted them to the car with a malpassi filter king at just under 3 psi. Throttle linkage is all free and not sticking, but started the car and the revs seemed to be raising and dropping so i couldnt get a decent idle or balance the carbs properly (only by eye through the progression holes). Blipping the throttle the revs were hanging up even with the throttle cable slack. I did wonder if the idle jets were too lean so i swopped from the 55F8s to 55F6s and still exactly the same. So i was thinking that we have an air leak, so sprayed some carb cleaner over the Misab O rings and no difference either. Just taken the carbs off the manifold and noticed that there may be a potential air leak from the O rings, but there are small round machined indents right where the o ring sits and noticeable leak path around them. The misab O rings look ok themselves, just an imprint of where the carb machining is. Has anyone seen this before? Is there a way to seal the carb flush around the area where the indents are or a sealant i can use on the O rings?

I was running some other 45s (which i sold) a while back and went to a 32/36 again, the car was dynod and set up before with the other 45s so its not an ignition or timing issue, just trying to get these newly purchased carbs running right if possible.








Many thanks, Neil

[Miniliteman]

Difficult to diagnose from behind a keyboard but I would check the fitment of the new chokes first.

[Graham]

Hi all,

Just fitted a pair of twin 45 webers to my pinto mk2 Escort. They had the standard weber jetting and all i have done is changed the choke sizes down to 34mm. Bought the carbs already bolted onto the manifold and fitted them to the car with a malpassi filter king at just under 3 psi. Throttle linkage is all free and not sticking, but started the car and the revs seemed to be raising and dropping so i couldnt get a decent idle or balance the carbs properly (only by eye through the progression holes). Blipping the throttle the revs were hanging up even with the throttle cable slack. I did wonder if the idle jets were too lean so i swopped from the 55F8s to 55F6s and still exactly the same. So i was thinking that we have an air leak, so sprayed some carb cleaner over the Misab O rings and no difference either. Just taken the carbs off the manifold and noticed that there may be a potential air leak from the O rings, but there are small round machined indents right where the o ring sits and noticeable leak path around them. The misab O rings look ok themselves, just an imprint of where the carb machining is. Has anyone seen this before? Is there a way to seal the carb flush around the area where the indents are or a sealant i can use on the O rings?

I was running some other 45s (which i sold) a while back and went to a 32/36 again, the car was dynod and set up before with the other 45s so its not an ignition or timing issue, just trying to get these newly purchased carbs running right if possible.


Attachment 89089

Attachment 89088



Many thanks, Neil

the lead plugs tend to sink with either age or over tightening the carbs, back in the day we use to take a drill and very gently drill a little way into the plugs and then fill the recesses with Araldite, when it was dry gently flat it down with wet and dry

[katana]

Odd marks - deffo look machined rather than impact damage. To discount, i'd brake clean them out, fill with epoxy and shave flat once cured to give flat surface for o-rings to seal against. It may not be the problem but best be sure!

[Mk2Neil]

Thanks, it is strange as the previous webers I fitted ran fine from the off although they just needed a dyno session to jet them better. I'll double check the chokes and put a light skim of araldite on the plug recess and skim flat. See how we go!

[Mk2Neil]

Just an update, took the carbs off and put them on another manifold with new misabs and bolted them back on. Got it running and unscrewed the idle mixture screws out each until I got a nice idle, then rebalanced the carbs. Now ticks over lovely and blipping the throttle is as it should be, so I think it was a mixture of an air leak or adjustment if the mixture screws. All ready to drive to the dyno soon. Thanks for the replies though!