• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Carburettor suction chamber cap loose - why?

Share this page

R

RobWarren

Jedi Hopeful
Offline
I've done a search but can't seem to find the answers....

I have a '67 BJ8 and everytime I take the car out for a drive, by the time I get back and check under the hood, the carburettor suction chamber cap on the carby closest to the windscreen is loose and sitting out on top of the chamber i.e. it's completely off.

Wondering why?

I've tightened it right up and still it comes loose whereas the other one is fine and doesn't move.

Any ideas?

Rob
 
Hi Rob,
Check both caps for a thin fiber washer under them. If the caps are metal & don't have the washer get the Moss #370-650 washers, or equivalent, & install. The washer helps a lot to keep the cap from vibrating loose.

Also, if the caps are plastic, many are, the threads may be worn or distorted enough to not hold. New dampers are available.

Probably not the problem, but a spit-pop/back through the carbs has been known to push the damper rod completely through the plastic caps, or to strip the plastic threads.
D
 
Will have a look at the thread as it's a plastic cap and I figure it must be coming loose with vibration and perhaps heat expansion as well.

Thanks Dave

Rob
 
I hadn't thought of that......it's just had a 13-month engine rebuild and a 500-mile service and oil change last week - put the Penrite oil in (recommended) so shouldn't be an issue.

I hope.
 
Rob,
I think Randy means the oil in the dampers. It should likely be no heavier than SAE 20. Many folks use ATF.

Too thick would put a lot more strain on the dampers.
D
 
Hello Rob,

the plastic tops only need to be tightened finger tight.

As far as damper oil is concerned I have been using the 3 in 1 household oil as it's about 10 wt and that seems to work just fine. If you have a wife that came with a sewing machine then sewing machine oil is about the same weight.

Regards,

Peter.
 
BUNDYRUM said:
As far as damper oil is concerned I have been using the 3 in 1 household oil as it's about 10 wt and that seems to work just fine.
Click to expand...

Peter,

I was told that 3 in 1 household oil is 20 weight and says so on some on the cans. I don't have any to check out that claim .. just thought I'd pass on that tidbit.

Cheers,
John
 
After having my rear carb's damper come loose a few times over
several months of driving,
I finally noticed that my rear damper was a different length and part number than my front damper ! I bought the right one
from Moss and have not had it come loose after that. It also seems to idle a little steadier.
Ed
 
I agree that the oil thickness can be the cause. I've used 10 and 20 wt. I've also used 2-cycle motor oil. It seems to work really well with my engine set up. You know the thick stuff really seems to mess up the operation of the engine.
 
That is an odd one, I would not think the grade of oil would effect the thing coming out unless there was a further problem with the threads or fit between the parts.

Does swapping them around make any diference? Probably won't, but shouldn't harm and might help, just the little screw in part, not the whole dashpot.

If that doesn't work couple ideas, dab of silicone sealant on the threads or the lowest strength of loctite (threadlocker if you can get such down under).
 
Righto - time to revisit this. I'm being lazy but I don't have the car back from the garage yet (where the engine is being rebuilt AGAIN). What's the best way to go about draining the oil currently in the dampers so I can replace it with 20wt for peace of mind.

And where can I find a wife with a sewing machine? They sound like an excellent purchase.
 
You can remove the chamber, take the piston out & turn it upside down. Or, apply suction to the fluid in place & suck it out. Or, mop it out with a piece of rag.

Didn't know that sewing machines were still being used.
D
 
Thanks Dave. As ever, you're there with the solution and other good ideas - good man.

Shame about the wives with sewing machines. I guess I'll have to make do with trying to find one that comes with a stack of cash and a toolkit.
 
I've used Marvel Mystery Oil(no joke), for several years. It's the right weight and also good for the head(upper end). Good to add a quart at oil changes too.
Patriick
 
Get an old, extra , eyedropper style antifreeze tester. Attach a snug fitting 3 inch piece of rubber or plastic tubing.
You can use it to remove the old contents of the damper reservoir and then use it to add your new choice of damper oil. I am also using Marvel Mystery Oil.
Ed
 
Back
Top