| Author |
 Topic  |
|
Peter Scott
United Kingdom
1240 Posts |
 Posted - 21/05/2008 : 19:30:46
|
Last week I had problems with my front float bowl flooding. I cleaned and checked the needle valve twice but could not correct the problem. In desperation I tried the old worn needle valve which I replaced a year ago and it works fine! Very frustrating.
Are Grose jets the answer? I am thinking about trying them but at £20 a pair I would like some input from those who have tried them first.
What experiences have you had with Grose jets?
Peter |
|
|
KevinH
United Kingdom
156 Posts |
Posted - 21/05/2008 : 21:52:51
|
Peter,
I had a problem with the float chamber flooding recently. The fuel pump would operate quite rapidly, then very slowly and the carb would flood. After checking everything and ú25 for a new needle valve, it seems that the needle valve wasn't sealing where it fits the float chamber and petrol was leaking in from underneath the valve. I removed the copper washer and fitted a fibre washer instead, tightened firmly and the flooding has stopped.
Kevin |
 |
|
|
David Allison
United Kingdom
665 Posts |
Posted - 22/05/2008 : 08:34:21
|
Peter - Kevin
These float valves dont normally give that much trouble - it is possible that the shaft holding the float against the valve (or even the holes in the float body top) is worn.
This can cause the float to stick - but seeing as the problem was cured by fitting another valve - I think it was the valve at fault.
I think you were unfortunate and recieved a bad replacement float valve.
No experience of the Grose Valve type method in SU carbs on MMM cars but the idea is common on the Holley carb in the USA.
It is not a new idea - simply the application of good common sense - rather like most engineering solutions.
The standard valve though has proven more than reliable in SU carbs for over 80 years so I dont honestly think that you can go against the needle type valve.
However - you pays yer money and takes yer choice!
I say again - I think you were unlucky.
Regards David |
|
|
|
Peter Scott
United Kingdom
1240 Posts |
Posted - 22/05/2008 : 08:58:52
|
Kevin, David
Thanks for your thoughts on this subject. The new valve has worked fine for a year and then suddenly is a problem. So it could be that the float rather than the valve is the problem. I am off on holiday today so will check the float and the shaft on which it slides when I get back. I will also check that the valve body is sealing OK, so I have covered all the angles.
Thanks, Peter |
|
|
|
tholden
United Kingdom
1638 Posts |
Posted - 22/05/2008 : 10:04:39
|
Peter I would also suggest that you check to make sure you do not have any dirt in your fuel which can cause an intermittent problem with the needle valve and also that your float chamber is vented to the atmosphere.
The original style of needle valves can wear quite rapidly and cause problems. I dont have any experience with the Grose valves but I would recomend the use of the Viton rubber tipped needle valves which can be obtained for about ú7 or 8 each from Burlen. Always replace both the needle and the valve together. I have rebuilt quite a number of pairs of carbs using these and have never had a problem. Only last week I fitted them to my MGA carbs to replace the sprung loaded plastic ones which were used in that era.
TH |
|
|
|
Rodney Collins
United Kingdom
424 Posts |
Posted - 22/05/2008 : 10:36:25
|
Hi Peter, Retired people tell me that they can't afford holidays any more, that's why I am still working!! Anyway last September I had the same problem on my single SU so much so that it filled my supercharge up with neat petrol! I stripped the carb cleaned it, checked it, and kissed it, and put it back together switched on----- and another blower full of petrol I did the same procedure but this time I used my airline (buy a cheap compresser best ever investment) and blew air into ever hole i could find, put it all back together switched on and waller!! no further problems. I am sure you will find you have some foreign body stopping the needle from sealing, but too small to see.
Regards Rodney. |
|
|
|
Gerhard Maier
Germany
873 Posts |
Posted - 22/05/2008 : 11:02:48
|
Peter,
since some years I use the Grose Jet in the ND and my ômodern MGÆsö,
and I regret that there is no size available for the bigger fload-chambers of the 1 7/8 carbs.
I think that the Grose Jet two-ball system needs less pressure for closing than the SU needle system, and there obviously must have been a reason, why SU changed over the years from the solid steel needle to the half plastic needle and even to rubber-tips.
The steel-balls in the Grose Jet are always moving and turning, and so the sealing surface will not wear and get pitted, and the bigger of the two balls which touches the hinged lever, has a diameter of about 6mm and so will not dig into the lever surface.
Surely when there is dirt in the petrol, also the Grose Jet canÆt cope with, and the higher price is another drawback for that system.
(and another little loss of originality!)
Gerhard
|
|
|
|
kimber
United Kingdom
1529 Posts |
Posted - 22/05/2008 : 12:50:56
|
quote:
Originally posted by KevinH
Peter,
I had a problem with the float chamber flooding recently. The fuel pump would operate quite rapidly, then very slowly and the carb would flood. After checking everything and ú25 for a new needle valve, it seems that the needle valve wasn't sealing where it fits the float chamber and petrol was leaking in from underneath the valve. I removed the copper washer and fitted a fibre washer instead, tightened firmly and the flooding has stopped.
Kevin
I must say that it does seem logical for the body of the valve to tighten against a thin copper washer, but my recollection of the many that I have dismantled is that none was present. I have just looked at a diagram on the Burlen website and none is shown. I'd be interested to hear what you knowledgable types have to say. (Any comments relating to age and memory loss will be treated with contempt). |
Edited by - kimber on 22/05/2008 12:53:39 |
|
|
|
JMH
United Kingdom
911 Posts |
Posted - 22/05/2008 : 12:54:31
|
Peter,
I would completely agree with what Terry says about the rubber tipped valves, I have found they cope better than the earlier plastic or all metal ones, even in applications where a much higher pressure pump has been fitted.
JH |
|
|
|
David Allison
United Kingdom
665 Posts |
Posted - 22/05/2008 : 14:13:02
|
Kimber - Andrew
As if I would make any comments about your age - you are only a few months older than me!
The carb on the NA did not have any washers between the float boat mounting and carb until last year - a probably misguided attempt to make things look nice prompted a fuel leak which only fibre washers would cure (I did not have any suitably sized copper ones at home).
I think that when everything is new and shiny - the machined faces probably dont need the washers - because everything is all flat and lovely.
74 years later and the damn thing is knocked about by a combination of UK roads (Berkshire are the worst), corrosion and alloy associated anno dominii (not yours or mine Andrew).
Terry - Jeremy
I also agree on the rubber tipped needle valve - it is a shame they dont do them the right size for the needle valve holder in the NA's big carb - I ended up making some new ones myself (although I now realise that it was while I was at Tech. and that was 28 years ago), the last one of which I fitted last summer.
My Midget used rubber tipped needle valves in its various combinations of SU float bowls - the Weber had a different method (which I never needed to take to pieces).
Very interesting what Gerhard says about the Grose jet - I certainly like the idea - just dont see it as necessary thats all.
Regards David |
|
|
|
KevinH
United Kingdom
156 Posts |
Posted - 22/05/2008 : 14:30:33
|
The problem that I had was with a new float chamber and lid assembly (bought several years previously). When it kept on flooding, I suspected the needle valve after checking everything else. After several conversations with Burlen (who were very helpful), I ordered a new needle valve which didn't solve the problem. I have the T4 assembly (3" dia float chamber) which uses a large needle valve which Grose don't make, and this is the only one to seat on a thin copper washer in the lid. I didn't like the marks on the copper washer when I removed the needle valve, which was why I changed to a fibre waher and solved the problem.
This is the only time I have ever had a problem with an SU flooding (30+ years of them), and have never had a problem with needle valves.
My problem was with a bad needle valve to lid seal, which is probably due to an imperfection in the seating area of the lid which the more resilient fibre washer has accommodated.
Kevin |
|
|
|
Peter Scott
United Kingdom
1240 Posts |
Posted - 22/05/2008 : 14:40:54
|
Very useful debate. Checking my records it was two years ago when I rebuit my carbs not one year ago (time flies.......). And checking the Burlen site I see that they now supply the viton rubber tipped valves as a matter of course. Looks like the metal tipped plastic valves are no longer sold. So perhaps I need to buy some viton valves.
There was no debris in the float bowl filter. I did have the tank off this past winter and washed it out and fitted new take-off pipework. But I agree that the fuel you purchase is not necessarily devoid of any dirt. So I will remove the float bowl and check it for cleanliness.
Thanks for all the input, Peter |
|
|
|
tholden
United Kingdom
1638 Posts |
Posted - 22/05/2008 : 14:47:59
|
Andrew you are correct there was never originally a washer between the body of the needle valve and the float chamber lid but a thin one will do no harm.
TH |
|
|
|
George Eagle
United Kingdom
3238 Posts |
Posted - 22/05/2008 : 21:00:10
|
I have an 1 7/8 inch carb on my blown NB. Normally there is no problem with flooding, the exception is if the car has been standing for some time and most/all fuel will have evaporated from the bowl. If I then switch on the fuel pump the force of the fuel entering the bowl can tilt the float causing it to jam. The solution is to turn the pump and and off a couple of times.
If used regularl there is no problem.
George |
|
|
|
Rodney Collins
United Kingdom
424 Posts |
Posted - 23/05/2008 : 10:07:57
|
That's interesting George, it was this situation that started my problem, my blown PA/PB had been standing for about 4 months when I went to give it a run, on swithcing on the pump just kept pumping and filled the volumex up with petrol. I will remember to do as you say switch on and off to refill the bowl.
Rodney. |
|
|
|
rbm
United Kingdom
141 Posts |
Posted - 27/05/2008 : 09:34:02
|
it has to be remembered that viton is only good on petrol, but is desolved over time by methanol.
Richard |
|
|
|
Topic |
|
Forum Locked
Topic Locked
