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runs better without air cleaners??

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Chet Zerlin

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100-6 BN6. Got both SU's synched with (obviously) air cleaners off. Took it for a test drive and ran great. Brought it back in and reinstalled both air cleaners then took it for another test drive and it ran really bad (?). Coughing on partial and also full throttle. Hesitation on full throttle too.

Came back in, took air cleaners off (PITA!!) and went back out and it ran fine again....

Both (wire mesh) air cleaners don't appear to be dirty but obviously something is changing the air flow into my SUs....

Anyone have a similar problem or have an idea what's going on? Suggestions?

Thanks!
Chet
 
Just a thought did you thoroughly clean the filters and re tune the CARBs with the filters installed???
 
That would suggest the rear air cleaner is badly clogged. Examining your spark plugs should be revealing--4, 5 and 6 might be sooted up.

Follow Keoke's advice and report back!
 
No idea what the vent setup is on your car..but...
I have seen contaminated crankcase oil affect carbs when the filter is put on with other marques.
Gasoline vapourizing and sucked into carb.
Just a thought. If you do have a vent line to the rear air cleaner, remove it and try again.
When we suspected this in shops, we'd pull the disptick, stand away from the car, and using the requisite Zippo, light the oil on the stick.
If it flared at all, change the oil.
 
Hi Chet,

As Keoke and Michael have indicated, the most likely cause of your problem is a blocked rear cleaner and checking the plugs would indicate the air/fuel mixture of your rear cylinders. However, I would also suggest you carefully check the body of the rear carburetor for any stress lines and movement when placing and tightening the cleaner on the carburetor.

Although not common, a friend a while back, had an elusive problem that turned out to be a carburetor body crack that would open just enough to screw up the movement of the piston and needle when too much torque was used to tighten the air cleaner. I must admit, I was very skeptical of his problem/resolution but was impressed by the similarity of issues.

Good Luck,
Ray(64BJ8P1)
 
One other question....has anyone found a easier method of attaching the air cleaners to the carb? The front one is not too bad but the back takes me at least a 1/2 hour and usually includes hunting for a nut or lock washer that fell "somewhere".....then has to be fished out from the depths of the engine compartment with a suitable magnet....:censored:
 
i have my Triple Webers set up on a rolling road without air filters. If I run the car in competition with the filters on there is a drop in performance and even a hesitation and fluffing under full acceleration as the filters do restrict airflow. In normal road driving it isn't noticeable. In your case it probably is due to a filter problem however you didn't mention any problem before you had the carbs tuned.
 
Check the gasket between the airfilter and the carb weather the holes line up. Blocking up the holes that connect the area on top of the piston prevents the piston to rise properly.
 
Hi Chet,

On my BJ8 with 2 HD8 carburetors, I use 1 bolt and a pin (with washer) inserted into a drilled through stud for center attachment of each carburetor. The approach provides a tight fit and eliminates quite a bit of hassle.

Carb Cleaner Pins.jpg

Ray(64BJ8P1)
 
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Today I decided to pull all 6 spark plugs and check them. Started with number 6 and worked my way forward. 6 and 5 looked "brownish", 4 was black (definitely rich), 3 and 2 were "brownish" and #1 was....well....broken.
IMG_4200.JPGIMG_4204.JPG
Fortunately I was able to use a screw extractor to get the core of that spark plug out of the engine without damaging anything. I replaced all 6 spark plugs and now the car runs great with both air cleaners attached:encouragement:.
Just wondering if anyone else has had this happen to them with a spark plug?
 
Not heard of this problem in Healeys, but Ford had a massive problem with broken plugs in some of their OHC V8s (different cause, though). I'd: 1) not use that brand of plug again and 2) put some antiseize--preferably nickel or copper--on the threads next time I install plugs and 3) torque carefully (they really don't have to be 'gorilla'd' down).
 
It is not difficult to break a spark plug's insulator by getting the socket "out of square" to the head. esp. if there is no rubber liner to help with alignment.
 
Check with the spark plug manufacturer on the use of anti-seize, some plugs threads are coated with a metal that acts as anti-seize and recommend You NOT use the paste.
 
bdcvg said:
Check with the spark plug manufacturer on the use of anti-seize, some plugs threads are coated with a metal that acts as anti-seize and recommend You NOT use the paste.
Click to expand...

Thanks for this info. I recently changed plugs in my 2008 Mustang GT and was confused that anti-seize wasn't mentioned in the shop manual (I put it on anyway, and reduced torque setting slightly). The original plugs came out easily and didn't seem to have any anti-seize on them; I should have taken that as a clue. I suspect it's pretty much only newer cars/plugs that come with the metal 'anti-seize,' but don't know for sure. The newer, pre-coated plug threads seem to have a brass-colored, 'anodized' look to them.
 
Since I have an aluminum head, I didn't want to take a chance on galvanic corrosion. The three brands of plugs that I have tried weren't coated with any anti-seize from the manufacturer.
 
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