5k Is It Webbers Or Valves?

[brendan]

hi all

just put in a 5k that i bought off a mate of a mate about a year ago into my 70

the problem is number 1&2 piston insnt fireing

i checked the comp and its reading 180

i checked for air leaks and theres none

i checked firing order and its all good

and also checked for spark

changed plugs and leads and still sounds like a dog

I'm running twin sidedraughts 45s and out of the webber feeding fuel to number 1 & 2 piston its spitting and backfiring a little .

all i can run it down to is a valves staying open or it needs a good tune

what do yous think it could be ?iether valves staying open or tune is out?

any suggestions would be greatly appreciated

 

(ohh and also when i put my hand over the webber feeding number 3 &4 it sucks my hand in very firm

but when i do it to webber feeding number 1&2 it sucks but not as firm)

 

cheers! >| :lolcry:

[Taz_Rx]

Deffinately tune.

If you had stuck valves you wouldn't have got 180psi on the compression test, it wouldn't have had any comp.

 

Dual webers/dellortos/solexs can be pretty tempremental if not tuned correctly. You can basically think of them as 4x seperate carbys. Hence having them all tuned in sync is imperative.

The more you can spend on some tuning then the better it'll be, ideally you want a dyno tune.

[brendan]

cheers

 

yeah thanks for the tip i thought if a valve were getting stuck wouldndnt it be pooring out smoke fromn the exaust ?or na

[Old fella]

G`day mate, it sounds like the carbs are out of synch. There should be a synchronizing screw in between the carbs on the throttle linkages that will increase or decrease the amount that number 1 carb is open at idle speed. Try turning the screw while the car is idling and at the same time using a peice of garden hose as a stethoscope and you should be able to get the carbs pretty close. Air mixture screws are located on top of the carbs near the manifold and unless you really know what you are doing, leave them to the experts.

When the carbs are out of synch like this, you end up with cylinders 3-4 trying to race 1-2 because they are getting more fuel. DCOE webers are notorius for rejectin a small amount of fuel while idling if you have a lumpy cam. It comes out like a fine mist or small droplets when you accellerate.

Good luck,

Old Fella.

[corollaart]

Sounds like you have a vacum leak on one carby ,replace soft mounts and even the manifold gasket.

 

Then as taz said get it on a dyno ,its the only way to do them and well worth the money.

 

It will be the only way to ever get the best out of them.

 

Because the first thing the dyno guy will check is vacum leaks.

 

rob

[philbey]

Dyno Dyno Dyno.

 

Seriously. I got 50% more power after a $300 dyno tune, even after fiddling and balancing them quite successfully myself.

[brendan]

hi all

i took all your pieces of advice and evryone of you were right (TUNE)even though he tuned it without the dyno it made a shit load of difference it running pretty good

He said for me too book it in for a dyno at his shop next wednesday and he'll make it run better again

cheers ! :wub:

Edited March 17, 2010 by brendan