Zephyr's got the percolation blues (HELP!) (link)

[Tom Wells]

The Zephyr has a 557. And a problem.

Here's the whole percolating gory story. Help if you can!

http://www.firstcoastcobraclub.com/v....php?f=8&t=743

Thanks,

Tom

[Z-linkCobra]

Do you have the plexiglass inspection hole plugs? If you dont go find you some so you can see what its doing. Sounds like to me you tried everything I would have suggested but I want to lean towards your fuel pressure rising enough to over power the needle and seats. Do you have a way to put a temp. fuel pressure gauge on it located somewhere that you can see it while driving to see if thats what its doing?

Do you have a return line on it by chance? If you do could that be plugged? Does your regulator have a vacuum port for increasing fuel pressure as needed. How are you setting your fuel pressure. With just the pump running engine off or engine running? If it has a vacuum port that might be jacking with you.

I dont mean to insult your intelligence an any way by asking these questions. Just throwing out some ideas.

Gene

[Tom Wells]

Gene,

>Do you have the plexiglass inspection hole plugs?
No, solid plugs. I set the levels idling with the solid plugs out.

>fuel pressure rising enough to over power the needle and seats.
That's why I changed the regulator. Same 5psi reading on the gauge.

>Do you have a way to put a temp. fuel pressure gauge on it located somewhere that you can see it while driving to see if thats what its doing?
I can try that.

>Do you have a return line on it by chance?
No return line. Both the pump and regulator are designed to work without a return. At least according to Aeromotive LOL

>Does your regulator have a vacuum port for increasing fuel pressure as needed.
No vacuum port.

>How are you setting your fuel pressure. With just the pump running engine off or engine running?
Tried both ways - engine on and engine off. Same result for pressure (5psi) and same percolation.

Thanks for the response - no offense whatsoever.

I wonder if I need to lower the whole engine bay temp somehow.

Tom

PS: Almost forgot! When the percolation starts, the fuel pressure goes to zero.

[mreid]

I read your saga. Can you post a picture of your engine? It would be helpful to see the fuel line routing. Also, does the fuel line (anywhere from the tank to the carb) come close to any exhaust components?

A couple of other things. Fuel line insulation can actually hold heat in vs. keep heat out, particularly if the line passes close to the exhaust at any point. Just because the regulator is designed to not use a return, does not mean that it will work well for your application. A return line would help immensly, but will provide a limited remedy if the line is too close to the exhaust. Picys please!

[Mister]

Tom,
I solved my percolation problems by replacing my large dropped base air filter with a small diameter air filter.
My theory, right or wrong, was that the big air filter was trapping heat. Whatever the actual cause was, the small air filter eliminated my fuel delivery problems.
By the way, my problems were much worse when "winter gas" was sold. I think it is more gaseous than "summer gas".
Good luck.
Mike

[lovehamr]

Tom I tried to respond on FCC but got that login thing. On the subject of the monster Zepher I have to think that getting some air moving through that Fox engine compartment may be a prime way to drop the under hood temps. I mean the largest engine for that compartment design was the 5.0 and seeing pics of that 385 series BB in your car tells me that with a solid hood there can't be much air flow through it. How about some louver type vents at the back of the hood? You could probably rip some out of some POS in a junk yard for a few bucks. I agree with mreid as well, having a return line for the fuel would help by keeping the carb with a constant flow of cool fuel. Besides, a FP designed to operate under high flow rates at 14psi can't be to happy constantly fighting a 5psi regulator. I would bet that those 2 mods would end your problem.

JMO of course. Good luck my friend.
Steve

[Tom Wells]

Steve,

The problem with the return line is that it goes from the reg - on the firewall - and not the carb.

Venting the engine compartment does sound attractive particularly if I can find a stealth way to do it. I need to look at the engine compartment and try to see if there's a way to do that!

BTW, just type in the "captcha" letters and you should be able to log right in.

Mike,

I have a wee small filter - well, it's kind of a screen - that I can try. I'll definitely put that on the list of things to try.

mreid,

Here are a few shots of the engine compartment, at least the first two in the thread. http://www.firstcoastcobraclub.com/v....php?f=2&t=677

The fuel line goes straight from the passenger side of the carb to the firewall. It takes a gentle turn toward the passenger side of the car where it is attached to the regulator.

From the reg it goes downward and outside the frame rails toward the rear of the car. I doesn't come near the header; probably a foot away.

The closest it gets to the engine at all is the rear of the passenger side head, which I just insulated today.

I'll try for more photos tomorrow after the Daytona Flea Market

Tom

[Tim Brewer]

How thick is your phenolic spacer? The bigger the better.

[Z-linkCobra]

Where are you getting your fuel pressure from? You say it goes to zero when the problem starts....zero at the regulator? or are you grabbing pressure from a line gauge that feeds the bowls? If its not there already anyway to get pressure at the regulator?

If it is a heat problem...which it sounds like so far you could put in a cool can after the regulator somewhere.

I think Lovehmr might be on to something when he talks about the 14psi pump fighting the regulator. Where is your pump located? If the pump is airating the fuel simply by force then when it gets to the motor compartment it will expand that much easier.

Maybe a small(like 1/4") return line off the outlet of the pump right back into the tank...take the back pressure off the pump.

Just thinking outloud.

Gene

[Tom Wells]

Tim,

The spacer is Edelbrock's 0.3" thick one. I already had to reduce the height of the air filter from 3" to 2-1/2" to accommodate it.

Gene,

The pressure gauge is at the carb.

The pump is in the rear, just next to the gas tank. The reg is on the firewall, well away from the exhaust (as in about a foot).

All,

One of the guys here thinks the underhood temp is the problem, as it isn't well ventilated. The carb works fine for an hour at a time on the highway; no problems. When I stop and the heat builds under the hood, the Vesuvius starts. And keeps going. The bottom of the air filter becomes way too hot to touch. And the engine compartment is pretty full!

So I'm going to do an experiment -> run without a hood for a bit, as a test.

If all works OK then I need to start to make the fake scoop into a real one, maybe open up the fake fender louvers and louver or otherwise vent the rear part of the hood.

I'll report back after the experiment.

If that doesn't work, maybe the return line could be the next experiment...

Tom

[lovehamr]

Actually, that sounds like a good plan Tom.

O'course you could always abandon the whole stealth rig thing, put a tunnel ram or blower on that puppy and just leave the hood off.

See, I'm here to help! LOL

[mreid]

Tom, that thing is awesome! Completely agree on the underhood temp as the primary problem and it sounds like your experiment will confirm it. Even with the air flow enhancements, you may still have the problem on hot days when idling. If you are using a dropbase air cleaner, it will trap manifold heat and boil the carb. Is there any way to get a thicker spacer under the carb once you open up the fake hood scoop? While I still believe the return regulator would help some, I don't think it is a primary solution. Lowering the underhood temp is though.

By the way, I thought you might like a couple shots of my 1970 Mustang. I put a 460 init and had at least two of the same issues - exhaust (had to fab my own headers and exhaust) and fuel percolation (different air cleaner, cowl induction hood, and return regulator). The cowl induction hood gave me both better air flow in the engine compartment and more room to raise the carb and air cleaner. Just a thought. No problems after those changes:





Mark

[cdog]

My car will do this, but only in extreme heat. Like idling on Las Vegas Blvd. in July.

Maybe try a KN filter and KN Xtreme lid. That could spread the heat out and maybe up.

Also, what manifold do you have? Maybe a low rise manifold gets hotter. I have a Torker II which is low rise and can get this issue.

How about slapping some big ass electric fans on the engine? How about lowering your thermostat temp?

Do you guys think that adding a return line could somehow help?

[Tom Wells]

March 26 update at the bottom of the thread here: http://www.firstcoastcobraclub.com/v...3&p=3799#p3799

Maybe the fuel line is picking some heat up somewhere....

Tom

[mdross1]

Fuel pressure dropping to zero means the needles are off their seats or at least one of them is.Naturally the pump is going to do it's job and overfill the bowls with nothing to stop it.You might talk to Holley about the zero fuel pressure issue
My 460 with 850 dbl pmp Holley regulated to 5.5lbs and water temps at 190+or- never gives me any problems.

[Jerry Clayton]

You have violated about every basic rule of fuel supply that I can think of--if you are interested in a plan to work your way thru this--let me know

[mreid]

Wow, I think this whole thread says that he is interested in a plan. Please do provide details.

[Tom Wells]

Plan details X2

[Jerry Clayton]

Areas that need to be changed---the fuel routing from the tank/pump needs to come forward via a minium of -8 (1/2in) line , well clear of all the exhaust and go to the front of the engine to go up to the carb area(this gives it a chance of airflow keeping fuel lines cooler). The fuel pressure guage you have won't work as you already know---it is liquid filled and needs to be vented to balance the pressure or you won't ever read any pressure.
After the line is fed to the carb, mount the regulator and let it regulate pressure via a return line to the tank.

Keep all this stuff off the firewall as you have entirely too much heat from the exhaust in that area--keep it up front and away from Exhaust.

Set the pressure at the carb at 3 1/2 lbs

Take a look at rerouting your stuff according to this and do pics if you can of any problem/questionable areas

[Tom Wells]

Jerry,

Thanks for the input. It's already ordered.

I'll use 10AN for the feed line and 8AN for the return. With a cooler in the return.

Keeping the lines away from any exhaust will be more of a challenge. The car has IRS and a full exhaust which crowds things up quite a bit, so keeping away from that will be a miracle. Thankfully the temps are only about 100* that far back, and I plan to wrap any nearby pipe sections with DEI header wrap as needed.

There will be a pause while the parts are in transit, and also while they are being installed....

Tom