AVS2 Dripping Fuel

[Steve Payne]

I have used this version on a couple of cars
https://bbclassics.co.uk/products/aerol ... drEALw_wcB

Easily adjustable and a reasonable price.

Steve

[88V8]

I am curious why no-one has suggested a fuel pressure regulator? Less than £100 all in for the V8 version. (The gauge detaches during driving).
Screenshot_20240915-215957.jpg

I agree. The Filter King I linked to above is a pressure reg. I have them on both my V8 cars and have had for over ten years. One car came to me with excessive pressure, one with too little.
One should never assume.
I leave the gauge permanently in place.

Wrt to ethanol and its tendency to vapour-lock, the less metal fuel line under the bonnet the better, as metal fuel line picks up heat.
Rubber does not pick up heat, and the use of high-quality rubber fuel line is not a safety issue provided it is run away from exhaust heat. I use Gates Barricade which is also ethanol-proof.

In terms of safety, don't site the regulator where a loose connection might drip on the exhaust.

As regards the OP, in addition to actually checking the fuel pressure and not just trusting that it's OK, take off the carb horn and check the float(s) height, as per the carb setup instructions which can be found on the Edelbrock site if one does not have a paper copy. The horn fixings are T-Stars btw, not Philips or Pozi..

Also check the needle valves.

Hint... before removing the horn, remove the centre stud that holds the air filter, or the horn gasket will tear on the stud. How do I know that...

[johnw]

Jensen lagged the steel fuel pipe. I don't think you can have a safer solution than an unbroken steel pipe from a mechanical pump to carb. If they work these unadjustable mechanical fuel pumps seem to keep on going for 30 years+ then they leak onto the floor avoiding standard exhausts. There is no high pressure that gets down regulated, so all relatively low pressure, no joints in the valley to leak into the oil or pool on top of the engine. For push on connectors like Nigel's pump, a simple pressure gauge is £15 off ebay, and it also does vacuum, and has push on connectors.

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[CliffCV8]

You lot are a bad influence

Hahaha. Underrated post here

[Darth V8R]

Jim wants to replace the carburettor altogether (with a 750 cfm Holley), fit a phenolic spacer (we had one originally but had to remove it because the air cleaner trumpet was fouling the bonnet, this may no longer be an issue after we bent the trumpets downwards), block the exhaust gas recirculation ports by fitting a different valley pan gasket.

Any thoughts?

Nigel:

While it is tempting to remove the EGR, if for no other reason that to clean up the engine bay, consider this: The EGR is inactive at idle and at wide open throttle so there is no idle or performance issues with leaving it in place. It is only active during cruise conditions when it reduces emissions AND improves highway (motorway?) fuel economy by about 5%. That's correct, motorway fuel economy goes UP with a correctly functioning EGR.

During cruise conditions, the engine must work to pull air and fuel past the throttle butterflies. This requires power, which means some fuel must be burned simply to draw in the air and fuel. This is caused by the engine pulling a high manifold vacuum on the intake stroke of each cylinder and each piston must work against the manifold vacuum during an intake stroke. The EGR reduces the work required to do this by bleeding in a small amount of inert gas to reduce the manifold vacuum. In engineering parlance this phenomenon is called a pumping loss which is one reason petrol engines are less efficient than diesels. Diesels do not use throttle butterflies, they throttle the engine by adjusting the amount of fuel (only), air flows into the motor with no restrictions.

In short, an EGR is a win-win. Reduced emissions AND better motorway economy. So unless your EGR is misbehaving, leaving it in place and functioning is a better choice.

BTW, the economy boost is not present in city driving, as the engine is seldom cruising, rather it is decelerating, idling, and accelerating. A properly functioning EGR is inactive under all of those conditions.

Vance

[NigelK]

Thanks for the comprehensive post Vance. I fear I may have led you down the garden path somewhat by my use of the phrase “exhaust gas recirculation”. On Mopar big block engines in factory spec, there is a temperature-controlled valve in one of the exhaust down pipes. When it’s cold this valve closes, and diverts exhaust gasses from the now closed down pipe, through the inlet manifold via “crossover ports”, and into the other still open down pipe on the other side of the engine. The idea is to improve fuel atomisation at cold ambient temperatures (I think). So not an EGR system at all. Sorry for my misleading post…

[Clive Bishop]

Late to the game on this thread, but I had a similar experience with the edlebrock for my 440.....I bought it from a main UK supplier and tried over 18 months and 500 to get it runnign right and in the end went to Jim and he swopped it out fore a Holley and problem solved.

It seems like others have said, even some of the from Edelbrock parts are not up to scratch these days and the "out of the box " running is not true. Jets and other components on mine were not right and when I asked under warranty was told it was over a year old no matter what mileage.

The Holley that Jim fitted has worked well since and doesn't foul the bonnet underside with the original air filter set up with snorkels.

[Steve Payne]

I agree some of the Edelbrocks dont seem to work as they should out of the box. I have fitted numerous ones over the years and some just work and others need needles swapping and endless tweaking before the engine runs as it should and others you just bolt on and they are perfect. I have found the electric choke on the 1411 can often need a tweak before it is 100% but that is an easy job.

Steve

[johnw]

I agree some of the Edelbrocks dont seem to work as they should out of the box. I have fitted numerous ones over the years and some just work and others need needles swapping and endless tweaking before the engine runs as it should and others you just bolt on and they are perfect. I have found the electric choke on the 1411 can often need a tweak before it is 100% but that is an easy job.

Steve

1411 is one I haven't bought. These carbs have numbers like 1406, 1806, 1411. Part numbers starting with 19 are the newer AVS2 series. I bought 3 in the space of 6 months around year 2000, all worked out of the box, with No 2 getting stuffed only as recently as 2020. I have yet to look inside properly, I suspect it is probably the needle valve getting stuck. I then opened the 3rd one that had been sitting in it's box for 20 years and it worked fine with modern fuel at least initially. Very pleased looking back that I went for a 3rd one!

[NigelK]

Jim Smith has been working his magic on the engine. Replacing the AVS2 with a Holley carb has resolved the lack of smooth idling / stalling in traffic problem.

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However 4 of the 8 spark plug lead boots were severely scorched, and Jim suspects spark plug firing issues caused by arcing at higher revs. These are not the right boots (they should be at the distributor end of the leads) but they were the only boots that could be made to fit the plugs on cylinders 3, 5, 4 and 6.

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The issue with these cylinders is a lack of clearance between the plug boot and sidewall of the header tube, exacerbated by heat wrapping. Replacement boots were showing heat damage within a few minutes of being installed. The wrapping is also retaining so much heat that it’s actually getting scorched.

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Jim has created reliefs in the headers so there is now some clearance. He’s also going to look at ceramic coating to reduce emitted heat - anyone have any experience with Cerakote products?

[Clive Bishop]

Hi Nigel,

Will ceramic plug boots not help the issue with your car?

I understand that the manifold is close and having it wrapped reduces the available space, which I why I have left that and will have my manifolds eventually ceramic coated for the 440 if I feel it is needed but to be honest haven't had the issue that you have with your engine with the issues above.

My Holley that Jim fitted runs well except for this moment, which needs to be investigated Maybe I'll have to get it towed up to Jim's for a engine fix and service

[NigelK]

Hi Clive

Good idea, but Jim says there's not enough room for the thicker ceramic plug boots, even with the reliefs in the headers. He's just finished prepping the headers for application of this - https://www.cerakote.co.uk/shop/cerakot ... ure-c-186/ It's what the manufacturer recommends for headers, interested to see whether it works...

Best wishes,
Nigel

[Clive Bishop]

Yep will be interesting to see, although not sure if that stuff is expensive or cheap in comparison to Zircotek or similar

[Steve Payne]

Ignition lead socks are the answer, https://www.amazon.co.uk/Shinehome-Degr ... D53NU?th=1
Slide them down the lead and they insulate the boots and leads from the heat. Can be fiddly to fit but once fitted you wont have any more problems with damaged leads or boots even if they touch.
Before I fitted these to my car even the most expensive leads would last a couple of years but with these they have been on the car for 8 years and are they are still in good condition.
Steve

[Darth V8R]

My view on heat soak:
Heat soak would not cause this to only happen above 1500rpm. I would say heat soak could only cause this at lower rpm like tickover, then it would disappear at higher revs as greater fuel consumption reduced the temporarily high pressure caused by heat soak.

+1 on this comment.

I would say that the size of the carburetor IS the problem. At idle up to some number (1500 RPM?) the engine is running on the idle circuit, when it transitions off the idle circuit, the fuel is then delivered by the main circuit. A high CFM carb has large boosters, and requires large air flows to operate correctly. My bet is that the vacuum signal is not strong enough to insure vaporization of the fuel in the oversized main circuit.

A gnarly cam can cause this as well, as there is little vacuum at lower RPMs and idle speed must be set higher to avoid stalling. The typical solution for this is to drill small holes in the butterflies so that the carb can use the idle circuit up to a somewhat higher RPM when the vacuum increases sufficiently. When the transition from the idle circuit occurs, it is at a high enough RPM to have adequate vacuum to operate the boosters.

Back to the problem at hand. If the boosters are replaceable, smaller boosters will likely fix the problem. If they are part of the main casting, you will need to go to a smaller CFM carb.

As to the "expert" recommendation, well, I would ask how much he works with downdraft carbs. Four BBL carbs are an endangered species these days, and true expertise is hard to come by.

Single plane manifolds also affect vacuum, and so are not routinely used on the street unless the engine is heavily modified. I don't know what kind of manifold you are using, but for street dual plane manifolds are preferred. If you are using a single plane manifold, you may find that you need to revert to a dual plane. Hopefully this will not be the case.

Vance