Webber'd 4AGE Running on 2 Cylinders

[75Ta22LT]

Hi everyone,

Getting REAL cut at the bloke that sold me this car.

The engine has high comp pistons, mild port and polish, dual 42mm DCOE carbs and crazy ass cams.

Now the only real problem im having, is that the bitch is running cylinder 3 and 4 only.

It has a pretty hefty vacuum leak behind the inlet manifold and arse end of the carbies.

Ive checked spark, checked compression, thinking it may be blocked idle jets or something. Possibly even fuel because they seem to fire over about 6500rpm (when it gets on cam).

Any ideas would be great as im pretty much stumped.

Cheers guys

[mongrel]

twin 42's... on a 1.6, poor thing is probably drowning.

[Ben Wilson]

Fix the vacuum leak before you do anything else, while you've got the carbies off, give them a good clean and see how you go.

[jonra23]

As Ben said fix the vacuum leak, guessing it is on the cylnders that aren't firing.

Are the cylinders firing at all, CAREFULY feel the extractor pipes on non firing cylnders to see if they are warm/hot.

If not firing at all check wether the front carb is getting fuel.

regards
jon

[kingmick]

Take out plugs of in 1 and 2 and see if there fueled up or dry!

[Fish]

i have the same problem!

We took the vacum port screw out of the front carby and she sprang ito life!!!!.

i'd get the manifold machined and straightened.

I'm getting mine cleaned and rebuilt. fucking things

[ViPeR_NiPPleX]

what's controlling the spark? but as everyone has said, definately get the leak fixed.

[75Ta22LT]

Yeh the leak was first priority.

The manifold is actually a pretty good little unit, looks proffesionally done.

Ive got $600 worth of receipts for the webbers being overhauled.

ALL 4 PLUGS ARE FUEL FOULED AFTER ABOUT 10-15 MINUTES OF RUNNING TIME.

HOWEVER, its a possibility that cylinder 1 and 2 arent getting enough fuel.

one or both cylinders fire periodically, when they arent firing, theyre filling with to much fuel and then when they do fire its just as a backfire.

Im using a HEC 715 bosch coil. Bosch recommends a MEC 715B (or 716B cant remember). Its definitely possible that this could affect it, however i did not believe it could do so to such an extent as to drop 2 cylinders.

The Vacuum leak is pretty much on all 4. I need to redo the seals.

Where is the vacuum port screw? i can spot the air/fuel mixture screws....

Going to play around with it tomorrow when i get the chance so ANY ideas will be a great help.

So far, planning to spray misted fuel down the trumpets to see if the dead cylinders are under fuelled. Gonna check the exhaust manifold (dont use ur hand fool those little spray bottles can save the injury) for heat on all 4.

Fuel Pump is a high volume, low pressure unit. Ive got a replacement which may be worth putting on, as the current one makes a VERY loud ticking noise but doesnt seem to tick over smoothly (very erratic).

[M.J.H]

Yeh the leak was first priority.

The manifold is actually a pretty good little unit, looks proffesionally done.

Ive got $600 worth of receipts for the webbers being overhauled.

ALL 4 PLUGS ARE FUEL FOULED AFTER ABOUT 10-15 MINUTES OF RUNNING TIME.

HOWEVER, its a possibility that cylinder 1 and 2 arent getting enough fuel.

one or both cylinders fire periodically, when they arent firing, theyre filling with to much fuel and then when they do fire its just as a backfire.

Im using a HEC 715 bosch coil. Bosch recommends a MEC 715B (or 716B cant remember). Its definitely possible that this could affect it, however i did not believe it could do so to such an extent as to drop 2 cylinders.

The Vacuum leak is pretty much on all 4. I need to redo the seals.

Where is the vacuum port screw? i can spot the air/fuel mixture screws....

Going to play around with it tomorrow when i get the chance so ANY ideas will be a great help.

So far, planning to spray misted fuel down the trumpets to see if the dead cylinders are under fuelled. Gonna check the exhaust manifold (dont use ur hand fool those little spray bottles can save the injury) for heat on all 4.

Fuel Pump is a high volume, low pressure unit. Ive got a replacement which may be worth putting on, as the current one makes a VERY loud ticking noise but doesnt seem to tick over smoothly (very erratic).

They may have been overhauled but were they jetted to suit the motor?
Doesn't sound like it if the plugs are fouled after 10 mins.

Probably the best thing to do is get the proper rubber type gasket for webbers and fit those with nylock nuts to hold the carbs on with vas they don't have to be done up super tight with those gaskits. Fit the recommended coil and plugs ( Are the plugs in there at the moment the right ones?) and take it somewhere to get them to rejet the carbs to suit the motor.


Oh and as for the fuel pump this may be a problem also as when I was running webbers I only had a std electric pump and had no fuel problems with that so maybe the pump you have is the wrong type.

Good luck with it all.

[takai]

HEC715 is the high energy version of the MEC715, it wont change anything greatly.

[75Ta22LT]

I bought a carby kit (one....fool) however it only had the gaskets for the front of the carbs, in between the trumpets and carby. I was planning on using rubber O-rings with some gasket sealer as i couldnt find anywhere to buy the specific gaskets.

Its recommended coil is MEC 717B

so.......with the HEC715 not having a ballast resistor etc etc......i dunno guys could be it.

Bloke at repco auto repair said it could be something to do with the tappets.

Oh, and the fuel pump is recommended for carbied applications, specifically aftermarket.

[takai]

4AGs dont have tappets.

[M.J.H]

I bought a carby kit (one....fool) however it only had the gaskets for the front of the carbs, in between the trumpets and carby. I was planning on using rubber O-rings with some gasket sealer as i couldnt find anywhere to buy the specific gaskets.

Its recommended coil is MEC 717B

so.......with the HEC715 not having a ballast resistor etc etc......i dunno guys could be it.

Bloke at repco auto repair said it could be something to do with the tappets.

Oh, and the fuel pump is recommended for carbied applications, specifically aftermarket.

Any speed shop should have the right soft mount kits like this one.

http://www.datrats.com.au/SOFT-MOUNTS.JPG

[Screamn_Sleeka]

twin 42's... on a 1.6, poor thing is probably drowning.

42's are the smallest DCOE's you can get...
40's are bigger.
Venturi:
40: 24-36mm
42: 24-34mm
45: 28-40mm

Depending on the parts selection for the webers, they wont be a problem.

Fuel pump should be between 2-8psi. 2-4psi is optimum.
If you are using the standard 4age fuel setup then it will be 15psi or something, and the webers wont be working properly, probably running rich and fouling plugs.

Vacuum leak could be the whole problem, its leaning out the mixture.
Buy some softmounts like posted above.

[nb86]

if it's consistently only two cyl's missing it won't be the coil.
vac leak is a definite possibility. fix this first.
unscrew the main jet cap on the front carb, the main jets should be alright if it's clearing up over 6500 rpm, clean the pilot jets out.
check that the throttles are set approximately evenly by removing the sight screws above the progression holes. then try to get a better balance by ear with the engine running. if you're still running rough, move on to idle mixtures.
remove the idle mixture screws and clean the ports with carby cleaner, then wind all the idle screws in and back out 1/2 a turn. from here back one screw out at a time and look for an increase in idle speed. when you get the highest possible idle, stop there and move on to the next screw. repeat it for all four, then go through and give them another tweak, again looking for the highest idle you can get. re adjust the throttle stops and possibly have one more go at the mixture screws if the idle needed significant adjustment.
if it's still no good i'm surprised, if your fuel pump ticks loudly and erratically it's a nasty solid state facet (or similar) and is probably ok.
i doubt it's valve clearance issues, the shim over buckets can't really be that far out, maybe enough to burn a valve or clatter a bit but not enough to kill two cylinders.