Hi all, I have a 300 with a Clifford intake, Edelbrock 500 carb and EFI dual exhaust manifolds. Has coolant plumbed to intake for heat.
The engine runs very good, but even with the manifold heat, the carb base is really cold while running. Then, after driving for a while, after shutdown, the carb gets really hot and boils the gas(heat soak?) and floods the engine.

So what's the answer? Was thinking about eliminating the intake heat and adding a pre heat setup to the air cleaner?

Has anyone done this? I currently have an open element air cleaner. What air cleaner would work best?

Any input welcome.

 

Check the float level, needles and seats. How does it run once you restart after it sits and floods? Can you see fuel leaking anywhere if you look into the carb at idle?

An air cleaner with the hot air stove helps a ton while the engine is cold but more restrictive than an open element. On my Bronco the A/C plenum butts up against the intake enough it requires a 9" diameter filter. One of these days I'll snag a couple of air cleaners from a junkyard to rig up something offset to accommodate a stove...

 

You have two separate deals going on.

The pre-heat set up basically is to help prevent carb icing. The venturi effect cools the air as it goes thru the carb. If you want the carb warmer while running then a aluminum carb spacer with coolant running thru it would be a good choice. This can also keep the carb from getting too hot while running. But doing that isn't going to help you much after shut down. Without the engine running the coolant doesn't circulate so it also heat soaks to a certain extant.


The heat soak is pretty common in small tight engine compartments like vans or a COE. To help with this you need to look into a heat shield between the carb & intake manifold along with a composite carb spacer ( made out of something that won't transmit heat very well ) . And you can also run a thick carb gasket between the spacer and the carb. I believe Ford did this on a lot of the carbed V8's from the factory.

If I can ever get my 300 engine swap done in my E350. I was considering, along with what I mentioned above, adding a small electric fan and some ducting to the carb area. Bring in cool outside air. And some how set it up so it will run for a few minutes after the engine is shut down. This will keep the air moving around the carbs to also help with this. I just haven't figured out how to do it yet. I have to find some kind of fan controller that will work for this.

One other thing. Are you running a mechanical fuel pump or a electric one? If you are running a mechanical one switching to a low pressure electric pump with a external regulator will also help quicker restarts if the gas does boil out of the carb. The electric pump will refill the carb quicker. And even if you are running a mechanical fuel pump I recommend a fuel pressure regulator. Certain carbs don't like much fuel pressure. And I have seen mechanical pumps have enough pressure to push fuel past the needle & seats and flood a engine. So I like to run fuel pressure regulators on any vehicle with a carb engine.

Enough of that novel.

 

Thanks Ted and Baron for the response.
Yes, it is the engine in my COE.....very tight quarters under the doghouse, which I'm sure isn't helping the heat soak problem. Also makes me wonder if I need the manifold heat. I may have to try it without. I have a wood isolator I plan to install under the carb....

As for the fan idea, I also had that thought. My '88 F150(4.9 EFI) had an "after run blower", not real sure what it was for, but it would sometimes come on after shutdown..... might check into that as well.

I am running a mech fuel pump.....will check pressure. When the engine floods, it starts sluggish with lots of cranking and me holding the throttle wide open. The excess gas does not seem to be getting all the way to the oil pan however, which is my biggest concern.

 

Your manifold heat is probably helping. Everyone calls it manifold heating, but it actually does more cooling then heating once the engine gets to operating temp. It should help keep the manifold from getting to hot. Go ahead and try it without it. If it gets worse put it back on. If it gets better leave it off. I don't run any on my inlines.

I believe those blowers were to blow air on the injectors. Not a whole lot of air flow by them with the manifold design. I don't think any of my trucks have still had the blowers by the time I get the trucks. I've had plenty of those air blower manifolds but everything else is usually missing. I forgot all about those. I'll have to do some searching at the yards and see what I can find.


Is the starting problem it being flooded or just not having any fuel in the carb? And have you checked and made sure the choke is open? I know I've over looked some of the simple things on mine in the past.

And your COE is a awesome truck!

 

It's flooding for sure....raw gas smell and it misses a bit till you get all the extra fuel cleared out.
Manual choke so easy to see that's open.

Back to the air cleaner.....what type air cleaner does a van w/a six use? Maybe I could make that fit....

 

It uses a offset air cleaner. The carb half won't work for you because it's for a little 1V carb. But a similar one that would probably fit your carb would be the offset one for a Early Bronco ( 66-77 ) with a V8. You should be able to find one on epay but they aren't cheap anymore. The prices are insane! I remember when I could buy these for $5.00 or less! I just checked and it looks like the cheapest one is $125.00 and it's missing the snorkel! Here's a listing, it's $185.00 but it has some good pictures to give you some ideas.

https://www.ebay.com/itm/1966-thru-1...UAAOSwKQ9aIFJW



With your fab skills you could probably make one fairly easy.

 

Interesting......aside from the price, it looks a bit too long to fit under the doghouse. I picked up a similar inverted/offset air cleaner at the junkyard today(for $15!!!!). Off of a '78? PU....will see if I can cut that up and make it work.

Thanks for your help!

 

Was the truck a V8 or the 300? I know some of the 300 powered 70's trucks had that style. But those are for the 1V carb. It will take some creative fab work to convert it to the larger 2V/4V carb. But it will give you the air cleaner assembly to start with. You got that for a good price! That's a whole lot more realistic then almost $200 for a air cleaner.

And if the single snorkel proves to be too much of a restriction. Then locate another similar air cleaner and pull the snorkel off it and cut another hole in your housing and add the second snorkel.

 

Let me take a look at the shelves in my garage. Might have something you can use for this project. I'll let you know. It mostly gathers dust anyhow lol. Also...i was having similar issues with a 300 powered truck. Checked the float, made a small adjustment, coolant plumbed under intake, installed an electric fuel pump, and ran a thicker gasket. It has ran like a champ since.
So...ran to garage and back. Theres a filter housing w/ horn, inlet ducting, and heat riser hose (nearly new,) also have a 14" open filter setup thats been sitting up there for a couple years. Might be another part or two i didnt see on the top shelf. Should be able to stitch something together between it all, if you want it.

 

Finally got time to check my floats.....they were a tad high. Then I noticed a larger issue....
I have the carb sideways for clearance, and the engine angle is about 4 degrees down at rear. So one float bowl is half empty(acc pump side) and the other is over full(fuel inlet side).
So I am making an angled carb spacer out of hardwood. Hope to level carb and isolate it from heat soak at the same time. We'll see if it works.....

Have not tackled the air cleaner project yet.

 

I'm surprised your Clifford intake does not already have a 4 degree tilt built into the carb pad. Mayhabpst somebody milled it "flat" for use in a circle track or dragster application.

 

That is odd, on an Offenhauser C the rear of the carb pad is visibly higher above the plenum than the front.

 

I think he has the carb mounted like you would on a Offy DP.

 

It's an older manifold that uses a bolt on carb adapter. I bought it used......