Twin carbs one not working ?

[Squirralien]

I have an EK with a Holden twin manifold and two Strongberg carbies (standard Holden version) one carby is working well and the front one doesn't seem to have much suction through the top at all and show no sign of fuel squirt, with motor not running the rear carby will spray fuel in the air, haha sounds great,, the front one nothing, when its running there is alot of suction from the rear and a hand over the carby top will stall the engine but the front has very little suction and has no difference to the motor running with a hand over it, I changed carbies on the front with no difference, the fuel bowl with the float is filling with fuel ?

Any ideas would be appreciated

[Harv]

No vacuum on the front carb - unusual.

a) is the choke plate on the front carb fully shut?
b) has someone put a blanking plate under the front carb (run one carb for economy, but keep the second one there for "cool factor")? Unusual for twins, but not unheard of when running triples.
c) is the throttle plate shut on the front carb (should still get suck though!).

Cheers,
Harv

[Squirralien]

Im a bit lost on the terms but both butterfly plates are operational and open, the accelerator butterfly seems to work fine but no fuel, the choke is not connected on the front one but it is open, and no blanking plate, I swapped it over and put another carby so I know its not likely to be the carby, but when the motor is reving and there is alot of suction in the rear carby and only very little from the front I don't understand this as they are both connected to the one manifold and I am sure the manifold gallery is as one right through not separated in to two so the two carbies operate one end of the motor only, If you know what I mean,, so how can one suck hard and close to nothing on the other one, I feel like I have worded this for a laugh but I can't think of another way,,,,
Is it possible that the motor hasn't got compression on the front so not operating the front carby properly,
Im just clutching at straws as you may know but Im not that mechanically minded, I can change bits and put motors together but that doesn't mean I understand the complete operation of it,
I will pull a plug out next time I get time to play and check it has compression, could a bent valve cause this maybe?

and stop laughing,,,, mind you I am so go ahead

[Harv]

Hmmm.... wierd. If both throttle and choke butterflies are open, the old grey should be trying to suck your arm in .

I'm not as familiar with grey twins (spent more time with BMC and Isuzu twins), but would assume the manifold is indeed "straight through" and not split front/rear. The manifold being blocked full of shit is an option, but unlikely. Assume the manifold gaskets (both head/manifold and manifold/carb) are OK and not blocking off flow?

Lack of compression is unlikely (we lapped the valves in on my 327 on a bench grinder to get it going, and it would still try to suck your arm in ).

The no fuel part should be easier though.No vacuum on the front carb means it won't pull fuel in when running (the back carb will compensate a fair bit though which is why it's still running). Despite that, it should still "squirt" when the accelerator is pushed (you said the fuel bowl was filling), as the accelerator pump is purely mechanical. Provided the bowl is filling, the fuel issue is less likely to be a carb problem (you've tried two carbs) and more likely the linkage isn't operating the front carb. If you disconnect the front carb linkage and operate by hand, does it squirt?

Sounds like front carb linkage is not operating the carb, leaving the throttle plate shut (no vacuum) and hence not operating the accelerator pump, though you said the throttle plate is operating... I'm out of ideas (though still not laughing... wish I had a beer for every time I couldn't work stuff out).

Cheers,
Harv

[newman]

Had a similar problem, ended up being a worn vacumn plunger, I was running an older one (I should have replaced them when I recoed the carbies, won't make that mistake again ) and the only replacement I could get was a plastic shaft one that you can shorten to suit a grey motor.
When you said Holden manifold I assumed red motor with X2 manifold, are they a recent addition or have they been on for a while?

Mick

[Squirralien]

yes it is a red, sorry should have mentioned that, the set up has been on for a while but at the same time I have only just bought the car so I do not know its history, from the outside it does look like the linkage is working fine, there is plenty of movement with the linkage to operate the carby, I would also think that if a gasket was failing to the point to stop the suction it has on the back it would be a noisey leak that could be heard,,
Would I be right to expect the suction to remain strong even if the carby or rather both carbies were not working

I am interested to know more about the vacuum plunger and where this would be, I will have a look in the manual and see if there is anything like that, maybe not, different carby to the grey I think,,

[Squirralien]

[Trev]

A simple question, is there a fuel line going to the front carb?

[Squirralien]

Yes theres a fuel line going to the front carby, I have put a picture up just above your post that you have probably seen now but it can be seen there on this side of the carby, when I took the front carby off and put another one on the fuel bowl with the float in it was 3/4 full of fuel so its definitely getting to the carby

[Stygian]

No offence, but those carbs look pretty old. What could be happening with both the carbs you put on the front is that the throttle shafts are worn and are letting in air. Kits wont fix this problem. It can be hard to see when the engine's running to as the vacuum tends to suck the shaft in and give the impression of no play. As Mick suggested, start by using professionally reconditioned carbs. Then if the problem continues, you know it's not the carbs, and then you can use a process of elimination to find out the problem. If it's not the carbs, I would take a good look at the manifold for problems and the whole throttle linkage setup for excessive wear. Good luck, I'm curious to find out what it is.

[Squirralien]

hmmm, ok thanks, recon'd carbies are a way off yet but I will continue to try things and let you know if I sort anything out, Im sure I will find another carby that will be good enough to work if it is 2 carbies that are no good and that really wouldn't surprise me,,
I don't take any offence to anything unless its just outright rude I just appreciate any input and I will work on any suggestions that I can within my budget, in time recon'd carbies might find their way on but can't afford to do it as a fault finding excersise, I have two other project cars tugging on the pocket and two daily road cars as well

[newman]

Easy check for vacumn leaks, spray WD40 around the carby bases where they bolt to the manifold and the throttle shafts with the motor running. The revs will rise if its leaking

Mick

P.S. Grey motors are my thing though I have had red motors, start collecting red motor carbs and make another pair up with new carb kits through them. You have a workshop manual and you can check the jets etc are the same when you take them apart ( They really aren't that hard) and it will be a good learning experience for you.

[Cal]

Why not grab the carbie from the back that does suck and try that on the front. You'll know straight away if it's a carbie problem or not.

[Squirralien]

I will try the spray and swapping carbies around,, thanks,,,

Thanks for everyones input, gives me many other things to try and I will keep this updated when I find the issue

[Trev]

The front carb doesn't even have a choke butterfly.
What size are they? carbs.
I would Get them professionally recoed and start again.