I have got an lcb fitted to my car, on top of the manifod just behind the rocker cover on the right hand side there is a pipe sticking up. Since i had the car someone had previously bodged bits of cable tie into it. Anyway, changed my carb today because the old one was playing up and found that for some reason the tube for the vacuum advance wasnt working. Tried unblocking it bt no luck. For some reason i decided to pull all of the cable tie out of the small manifold tube - the revs dropped and car was running rough. So i bunged up the carb tube and put the vacuum advance pipe on the manifold tube, now the car runs great. Question is - what is this pipe and is it ok to run the car like this?? Sorry cant put pics on at the moment. Engine is a standard 998.
Small Pipe On Top Of Manifold
Started by
DavesBluey
, Mar 21 2006 09:45 PM
10 replies to this topic
#2
Sprocket
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Posted 21 March 2006 - 09:55 PM
Cant understand your description as there are so many pipes in the engine bay.
Picy????/
Picy????/
#3
dan__wright
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Posted 21 March 2006 - 09:59 PM
for lamda sensor?
#4
Bungle
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Posted 21 March 2006 - 10:00 PM
what age and engine does your mini have ? 
#5
RacingGreen
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Posted 21 March 2006 - 10:03 PM
what age and engine does your mini have ?
"Engine is a standard 998"
for lamda sensor?
Not on a carb'd 998
#6
DavesBluey
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Posted 21 March 2006 - 10:10 PM
dont really know the age of engine as its not original, blieve uts early 80's?
Maybe manifold is the wrong description (not too good when it comes to engines). Its the bit that bolts to the head which the carb and the manifol bolts to. This is the part wi the tube i'm talking about on top of it.
It has a pipe each side which i think some one told me you can connect pipes up to it to have it water cooled or something? The tube sticking up looks like a vacuum advance pipe, but is dead straight, about 3/4 of an inch high.
Maybe manifold is the wrong description (not too good when it comes to engines). Its the bit that bolts to the head which the carb and the manifol bolts to. This is the part wi the tube i'm talking about on top of it.
It has a pipe each side which i think some one told me you can connect pipes up to it to have it water cooled or something? The tube sticking up looks like a vacuum advance pipe, but is dead straight, about 3/4 of an inch high.
#7
Dan
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Posted 21 March 2006 - 10:13 PM
It's the inlet manifold, nothing to do with the LCB.
It's just a vacuum source, block it up. It probably means the manifold was designed for a different Mini than yours.
It's just a vacuum source, block it up. It probably means the manifold was designed for a different Mini than yours.
#8
DavesBluey
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Posted 21 March 2006 - 10:16 PM
As the vacuum pipe on top of the carb doesnt seem to want to unblock is it ok to use it for the vacuum advance pipe then???
#9
Dan
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Posted 21 March 2006 - 10:19 PM
Not really, it's quite important for good running where the vacuum source for dizzy advance is taken from. On the Metro there was a great problem with rough running when they tried to move the advance connection around on the carb, it really needs to be right by the throttle.
It would be ideal for a vacuum gauge though.
It would be ideal for a vacuum gauge though.
#10
DavesBluey
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Posted 21 March 2006 - 10:24 PM
cheers, ill work on getting the other one on the carb unblocked then. My car has never really run near perfect since i have owned it. I am now wondering if it was because the cable tie blocked hole was letting a bit of air in? Im hoping blocking it up properly will help?
#11
Sprocket
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Posted 22 March 2006 - 12:02 AM
All depends if the dizzy was intended to be used with throttle edge depression or manifold depression. The vac take of on the carb may well be throttle edge depression and as such there will not be much of a vacuum at idle, at least not untill the throttle is depressed slightly. Like the name suggests this point is right at the throttle edge and vac is reliant on the position of the throttle at that point. Manifold depression will see what ever vacuum is pressent in the manifold and a good vacuum will be present at idle.
Now it all depends if you have a Throttle edge depression carb and a manifold depression dizzy, or a manifold depression carb and a throttle edge dizzy, if so, it may never run right untill this is corrected. As for what you should have and how to identify what it is I dont know, but if you still have ALL the original parts it may give you an idea.
This has a lot to do with total ignition advance and where it comes in on revs. Throttle edge depression is used to give a vacuum advance curve that is low vacuum advance at idle, higher at part throttle, and lower at full throttle. Manifold depression gives high vacuum advance at idle, lower at part throttle and lower still at full throttle. this is aditional to initial advance setting and mechanical advance, so it is very important to get the advance right at specific revs, particularly with the crappy low octane fuel we are forced to use
Either way if there are leaks in the intake side of things, these need sorting first
Now it all depends if you have a Throttle edge depression carb and a manifold depression dizzy, or a manifold depression carb and a throttle edge dizzy, if so, it may never run right untill this is corrected. As for what you should have and how to identify what it is I dont know, but if you still have ALL the original parts it may give you an idea.
This has a lot to do with total ignition advance and where it comes in on revs. Throttle edge depression is used to give a vacuum advance curve that is low vacuum advance at idle, higher at part throttle, and lower at full throttle. Manifold depression gives high vacuum advance at idle, lower at part throttle and lower still at full throttle. this is aditional to initial advance setting and mechanical advance, so it is very important to get the advance right at specific revs, particularly with the crappy low octane fuel we are forced to use
Either way if there are leaks in the intake side of things, these need sorting first
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