no oil in my dashpot...is this a bad thing?
Discussion
Hi fellow cainers, I have just noticed (being a trifle lazy and not really mechanically minded) that there is no oil that I can see in my dashpot. the carb is an HIF 44 1.75" and the car runs absolutely spot on, and has done since I got it 20,000 miles and 2 years ago.
Any ideas? and also, what does the oil do? and why does it work fine without it?
Thanks
Tom
Any ideas? and also, what does the oil do? and why does it work fine without it?
Thanks
Tom
You need to put some oil in there, depending on what state of tune ur engine is it could need 20W50 if standard or thin 3 in 1 type if its a high state of tune.
It acts as a damper and stops the piston from banging up and down when the air pressure changes in the carb. So the piston acts just like your car if you took the shocks off of it!
It acts as a damper and stops the piston from banging up and down when the air pressure changes in the carb. So the piston acts just like your car if you took the shocks off of it!
cone said:
ur car will have a realy bad flat spot, unscrew the top, if it sounds like a shy girl frm Hull , top it up wid 3in 1 , b carefull puttin top back on them HIFs cross dead easy !
I haven't noticed any flat spot, but then again it does have a 286 degree cam in which means it waits until 3750 before doing anything interesting! I'll get some of the 3in1 stuff. so do I just unscrew it and fill it up to the very top? or what? and why does it cause a flat spot?
>> Edited by minimax on Thursday 13th January 17:29
I think the oil thickness you fill it with largely just dictates the throttle response you get. A light oil will mean a faster response to changes in engine load (ie, rpm/throttle openage) but the piston (which the oil sits in) is likely to bounce about if the oil does not provide enough damping (And hence the fuel mixture bounces with it...)
I've found mine runs nicely on mostly 15W40 Castrol engine oil, with just a tiny dash of some light oil.
If you're feeling adventurous, you could experiment with different oils or different oil mixtures. You'd probably find you can adjust the "attitude" of the engine by doing this. Some cars are more sensitive to the type of oil you use than others.
I've found mine runs nicely on mostly 15W40 Castrol engine oil, with just a tiny dash of some light oil.
If you're feeling adventurous, you could experiment with different oils or different oil mixtures. You'd probably find you can adjust the "attitude" of the engine by doing this. Some cars are more sensitive to the type of oil you use than others.
I use a 15/50 in the Summer and a light, 3 in 1 type oil in Winter. If you overfill it you may get a bit of smoke, but it doesn't matter. However, make sure the little hole in the dashpot screw-in cover is not blocked. Of course, you can mix different thicknesses of oil to achieve optimum throttle response, although you shouldn't really need to.
The damper gives you transient enrichment as you open the throttle, by holding the piston down and increasing the depression through the choke. This is the SU equivalent of a throttle pump, and improves throttle response. But having the piston held down also increases the restriction and limits power, so ideally you want just enough damping to give you enough enrichment to give you a crisp throttle response. Too little and the engine will gag briefly as you open the throttle, too much and it will take a moment for the power to build up.
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