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Inlet Manifold Leak?


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#16 paul748

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Posted 17 September 2018 - 05:44 PM

Do you have the vacuum advance pipe connected?

I had similar issues and found that the rubber connector at the carb end was not sealing correctly.

Also check the crankcase breather pipes.



#17 Spider

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Posted 17 September 2018 - 06:02 PM

Worn Butterfly and / or Throttle Shaft will also be a cause.



#18 carbon

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Posted 17 September 2018 - 06:46 PM

And running with a non-standard exhaust. The flanges on most of the currently available exhuast downpipes are slightly thicker than the original type.

 

In my experience if you use original inlet manifold with a more recent exhaust there is 10-20 thou difference. This was enough to cause leaks into the intake and resulting in uneven idle.

 

Needing an AAA needle may be sign of intake leak. AAA is one of the richest profiles available and may overfuel a 998 under load unless you're running a significantly modified unit.



#19 EasterBern

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Posted 17 September 2018 - 07:04 PM

Thanks for all the replies, I think I've got it sorted now.

 

20/50 oil in the dashpot and back to an AAU needle and it's running perfectly (at the moment anyway).

 

Well, it started missing on the first trial run. Then I noticed that the fuel gauge was on empty!! A can of fuel and then it was fine on the 2nd run!!

 

I think it was a worn shaft on the HS4 that originally caused it to run lean, but the HIF38 it's now got seems to be good.



#20 cal844

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Posted 17 September 2018 - 07:24 PM

Perfect, do you have an inline fuel filter you could fit?

If not you can get them at an MOT station, then fit it between the tank and fuel pipe at the rear subframe, as to get to the float assembly on an HIF 38 means the cab has to come off the car

#21 EasterBern

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Posted 17 September 2018 - 07:52 PM

I did have one fitted between the pump and the carb, but during the last carb change I somehow managed to lose it!! I got it from Halfords, I will get another.



#22 EasterBern

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Posted 25 September 2018 - 06:49 PM

I took the Mini on a 100 mile trip today, and it's back to it's old tricks!

 

Well, not as bad, the idle is up to 1200 RPM again, and it feels weak again. But nothing like as bad as before.

 

Interestingly, I had to put some more petrol in again near home. It started running better with more fuel in the tank, so maybe the fuel pump is getting weak?

 

Also, at times when accelerating I could hear a sudden whistling sound, so I'm thinking that it could be the inlet manifold not sealing properly, I'll check the thickness of it and the exhaust manifold as mentioned above.



#23 cal844

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Posted 25 September 2018 - 09:11 PM

I'd say to get a pressure regulator to check the pressures, maybe even try to rig some kind of camera or recording device so you get an accurate picture of what's going on

#24 Homersimpson

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Posted 26 September 2018 - 07:23 PM

I had a car that ran better when full than empty, it turned out to be a blockage inside the tank on the fuel outlet where someone has siliconed the fuel gauge sender in and over time some of it had dropped into the tank and got sucked into the outlet.

 

It might also be worth checking the tank vent is working.






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