fuel pressure regulator

[Dom]

Do I need one of these even if im running on dcoe carbs? an currently running with a facet silver top competition pump feeding the carbs directly with no problem so far, but would like to rule out a possible problem with fueling.


cheers

[graham bahr]

yes, no, maybe,
its preferable,

the float valves in your carbs are only designed to withstand 2/3psi fuel pressure, which is certainly less than the fuel pumps producing.

by fitting one your less likely to suffer from floading as the needle (float) valves wear, sometimes you will get improved and clean carburation as the fuel level which is likely to be a bit high with too high a fuel pressure is likely to be better, unless your carbs have jets that are a bit on the small side, in which case your still better off to fit one and rejet as nec.

some cars depending on how well they are set up in the first place gain considerably in the running and economy depts

[Al Weyman]

Fit a Filter King with adjustable pressure capability and run a pressure guage off it (leave it under the bonnet unless you fit an expensive sender kit, I have mine just poking under the bonnet and can still read it from the cab), not only do you get an excellent low restriction filter but can fiine tune the pressure. I solved a lot of problems on my black Camaro with one of these set ups. I actually set the pressure to around 4 to 5 psi. and the trick is to make sure it never drops below 3psi flat out at the end of a long straight as a momentary fuel starvation problem on a big V8 (or any engine I should imagine) can wipe out the piston crowns in seconds once the cooling effect of the fuel is lost.

[R59]

Another option is to run a return setup on your plumbing. It's what they fitted to the Vauxhall Nova Sport as standard fitment, and it worked a treat.

Concur with Al's comments on the cooling effect being lost with fuel starvation, and the idea of filtering with low restriction. My current car uses a FRAM cartridge filter, but then again, I'm using -8 plumbing (7/16th") for most of it, and -10 (1/2") for the rest, so it's big flow.

Rob.

[Dom]

the reason I ask is that now I have a rough running engine (which i originally put down to the massive cam wear on one exhaust follower) which now has a new cam and i'm sure the timing is spot on but the spark plug on one cylinder is permenantly wet with fuel.

Could not having a regulator cause these symptoms?

[graham bahr]

no, unless you have something very weird going on if its only one cylinder effected it cannot be down to fuel pressure.

the first place to start is a compression test have you got a tight tappet? and check that your are getting a spark, have you tried a new plug? sometimes a cylinder can be so wet with fuel that even a new plug wont fire, warm the engine up, put a hot plug from a good cylinder in the problem one and try it again.

have you got a massive air leak? this could cause a mixture too weak to burn but could still foul the plug, its unusual to find both symptoms but possible, try spraying the inlet manifold carbs mounts etc with wd40 or sinilar with the engine running, if the spray effects the way the engine runs you have got an air leak

if non of this helps then you have a problem with one barrel of one of your carbs. is the idle jet missing? that would allow big quantities of fuel into that cylinders, dont laught but we once had a guy drive a car down to us for jetting because it ran really badly and consumed massive quantities of fuel, when we went to check the jet sizes we were amazed to find non fitted!! is the idle air corrector jet blocked? maybe the carb has a badly twisted spindle so one butterfly is more open than the others and the wet cylinder is drawing fuel from the mains when the engines idling, look down the chokes with teh engine running, can you see fuel dribbling from the aux vents on the bad cylinder, listen to the carb balence with a bit of hose, a slight different between the two carbs is possible but, if the engine has good even compressions both barrells on each carb should sound identical, if not you have a twisted spindle

[graham bahr]

have you only just fitted the carbs? what did it run like before it wore the cam lobe?

[Dom]

Compression is good, different plugs have been used - definitely getting a spark.

Carbs have been on the car 3 years and engine ran fine up until the cam wear.

Having taken the head off, the piston on that cylinder is very clean compared to the others and taken off the manifold with carbs still attached - looking up the manifold there is a puddle of fuel sloshing around the o rings on the offending cylinder.

worth noting that that carb is more gungy on the outside especially around the affected cylinder.

Can't find any gaping holes where jets should be - car was dyno'd a couple of months ago.

[Dom]

It's just occured to me that 3 races ago part of a filter sock was sucked into the carb - possibly the offending cylinder i'm not 100% sure. This ended up wrapping itself around the spindle and keeping the throttle wide open (not fun when trying to brake for a corner!)

Since then after extracting the foam (everything seemed ok) i've had a head gasket failure, the strange cam wear on a fairly new cam, and now this weird overfuelling. Nothing was mentioned at the dyno recently about the carb being a problem though.

[graham bahr]

cam wear is possibly caused by massive overfueling, thinning the oil, massive over fueling would also leave the top of the piston clean,

is the engine in one piece or in bits? if its in bits i would take the carbs off and look down them whilst holding them upto the light and see how much light you can see around the throtlle plates with the throttlesd closed, each barrel of the carb should be the same, although off the car both carbs will be different

have you done a compression test?

[graham bahr]

what sort of engine is it?

[graham bahr]

i take it it was on the dyno before the problems started not since

[graham bahr]

if you put a nice new spark plug in it will it run on all cylinders? if it does is it only at high revs? or does it tick over but not want to rev smoothly?

[Dom]

It's a ford CVH 1600. After installing a regulator it seems to run fairly happily at medium revs but is reluctant to idle. I've not played much with the revs as I still have to bed in the cam yet.

A change of plug make no difference - it's does run but plug still gets damp.

It was dyno'd before the cam problem but after the filter incident.

[graham bahr]

are all the compressions even? if it runs i would listen to all the intakes with a length of rubber hose, which should give you a better idea if its a mechanical problem or not, does the engine respond to the idle mixture srews on all cylinders?

[Dom]

Yep the compression is good and even over all cylinders. I'll have a fiddle with the idle screws during the weekend after i've finished running in the cam.

[Al Weyman]

Do you have Hydraulic tappets still in the engine, may be a problem there, pumping up and holding the valve off the seat but not apparent when doing a slow turn over compresson test, just a thought. If you are sure there is nothing wrong with the carb set up (maybe borrow a set and try them on) then it must be a mechanical or an electrical problem associated with that cylinder.