Question about 540 CI Dart Motor

[Ron in SoCal]

So the motor runs fine when you do the ol' pour gas in the carb trick which means (to me) your fuel pump is probably fine cause it spins fast enough and moves enough fuel when the motor is running, but your lines or filter are crap when you turn it over via the starter.

Not sure if you've done this but figure out if the carb is getting fuel when cold. If not, have your flex lines tested and check / replace the filter.

I hate diagnosing over the interwebz.

[intocarss]

Originally Posted by uxojerry

Dart 325 heads would be a normal selection for a 540. With Lemon's headers and a 3.5 inch exhaust, Im thinking your 540 is something more, maybe Dart 345s. A run of the mill 540 is 650hp. A trick 540 is 850hp or so.

There aren't many BBC fans here. Remember you'll make more hp with a plug wire off, than most with a perfect tune, lol.

Originally Posted by Xpock182

Could you tell me more about what you are referring to here? Also I am trying to figure out why the car is not cranking up immediately all of the time. It seems that after it sits for a week or so it won't crank.

I took the air filter off and try to crank it but I don't think it's getting gas. However if I pore a small amount of gas directly into the carburetor it cranks right up and runs fine.

I cleaned the fuel filter (it was a mess) cleaned the distributed cap & sprayed carburetor cleaner in both carbs.


Unfortunately the car does not have a fuel pressure gauge. This car sat for about 2 years before I purchased it.

Any advice? Is this a bad fuel pump?? Spark plugs?? Perhaps this car was not built for street gas??


Would love some help.

What uxojerry is referring to is the port volume of the heads.... .

If that car has been sitting for a couple of years and is running rubber braided fuel hose, the rubber could be coming apart inside the hose and clogging things up.

Another thing I've seen when a car sits for a long while is the fuel pump diaphram gets weak as do accelerator pumps in the carbs and does not pump enough fuel when trying to start it via cranking it over...IMOHO get rid of the 2 carbs and get a single Holley or electronic EFI unit. BTW very nice car

[Flash68]

Originally Posted by intocarss

What uxojerry is referring to is the size or flow numbers of the heads.... 325 cfm or 345 cfm.

Actually I think those are the intake runner volumes.... like AFR 227 vs 235, etc. etc.....

Those heads surely better flow a lot better than 325 or 345!

[intocarss]

Originally Posted by Flash68

Actually I think those are the intake runner volumes.... like AFR 227 vs 235, etc. etc.....

Those heads surely better flow a lot better than 325 or 345!

You're rt it's port volume

[Xpock182]

Originally Posted by intocarss

What uxojerry is referring to is the port volume of the heads.... .

If that car has been sitting for a couple of years and is running rubber braided fuel hose, the rubber could be coming apart inside the hose and clogging things up.

Another thing I've seen when a car sits for a long while is the fuel pump diaphram gets weak as do accelerator pumps in the carbs and does not pump enough fuel when trying to start it via cranking it over...IMOHO get rid of the 2 carbs and get a single Holley or electronic EFI unit. BTW very nice car

I think you hit the nail on the head. I shined a light into the fuel tank and see a lot of black small bits in the fuel. I'm assuming its rubber.

With this being said I would have to assume that the fuel pump has some junk clogged in it also.

I think my solution is to replace the manifold (to accommodate a single 4 barrel Holley) and buy a new carb. Also I am going to consider replacing the fuel pump and all of the fuel lines.


And thank you very much by the way!

Now the question is if i should go ahead and go to EFI or replace all of these parts.

[68Cuda]

Originally Posted by Xpock182

Now the question is if i should go ahead and go to EFI or replace all of these parts.

If the money is not an issue, go EFI. You will have to swap out the whole fuel system though.

By the way, quite a few cars on this site do not have LS engines...

[Solid LT1]

Originally Posted by 68Cuda

If the money is not an issue, go EFI. You will have to swap out the whole fuel system though.

By the way, quite a few cars on this site do not have LS engines...

I had one of those Weiand 440 Six Pack "super stock" manifolds back in the 70's on my Mopar, that thing had HORRIBLE! Fuel distribution problems, I nearly took a piston out with that thing....sold it for cheap...I hear they are worth some $$$ nowadays..

Back to OP, you want a billet mechanical fuel pump and do yourself a favor and make sure that big Rat motor has a lightweight fuel pump pushrod in it for high RPM reliability. The Carter AFB dual quads aren't known for being a good road race style carb, a single big Holley 4bbl carb will probably make more power and perform better in hard cornering. My buddy is building a touring 55 Chevy and he's using that dual quad intake with 2 FAST 4bbl throttle body/injectors on his 454 motor, he had a aluminum plate CNC'd to offset the throttle body's and make them fit the intake, it probably won't make as much power as a well done port fuel injection intake but, he wanted the 2X4bbl look on his motor. When the bill is all totaled up, I think he will have around $4K invested in his EFI project....about 1/2 the price of an all aluminum LS3 crate engine

When you replace the fuel lines go with PFTE or "Teflon" style hoses as they can tolerate the ethanol in modern pump gas. Earls, Fragola, Tech AFX are some good sources for PFTE style hose/fittings.

I'm looking closer at you engine photos....looks like you have a good billet mechanical pump on that Rat motor....rebuild kits can be sourced from Speedway Motors or CV products if you think then fuel pump diaphragm/check valves have problems.

[uxojerry]

I think it would be important to get the current fueling issues fixed, carbs tuned etc., before going efi. You may find that you like the current set up.

I would suggest finding a local trustworthy engine shop. Have them fix your current issues and do a partial tear down on the motor and check everything out. That will get you the piston, head and cam specs and some peace of mind.

If you decide to go efi, check with F&B Throttle Bodies. They do a lot of 2x4 and 3x2 efi kits and are very reasonable.

The best BBC resource on the internet, is the performance section of the chevelle forum. A member near you may be willing to give you a hand.

Your car is beautiful and has some very nice parts and outstanding craftsmanship as depicted in the photos. Good luck working out the bugs.

Is that a Dart aluminum block? Photos kind of lead me in that direction. If so that is around $4k above an iron Big M.

[68Cuda]

Originally Posted by Solid LT1

I had one of those Weiand 440 Six Pack "super stock" manifolds back in the 70's on my Mopar, that thing had HORRIBLE! Fuel distribution problems, I nearly took a piston out with that thing....sold it for cheap...I hear they are worth some $$$ nowadays.

Take a close look... no fuel distribution problems with this intake. This intake is considered the best cast manifold ever made for the 440. It takes some modifications and considerable tuning to get it to work good with the six pack carbs because the fuel tends to puddle under the center carb. It was originally intended for super stock use and was not meant to be used on a street car. Mine is converted to port EFI - no fuel mixture issues! Best of both worlds!

By the way, those intakes start around $1k these days, depending on condition.

Originally Posted by uxojerry

If you decide to go efi, check with F&B Throttle Bodies. They do a lot of 2x4 and 3x2 efi kits and are very reasonable.

F&B did the six pack intake on my car (see my previous post for a picture).

[GregWeld]

Originally Posted by Xpock182

I think you hit the nail on the head. I shined a light into the fuel tank and see a lot of black small bits in the fuel. I'm assuming its rubber.

With this being said I would have to assume that the fuel pump has some junk clogged in it also.

I think my solution is to replace the manifold (to accommodate a single 4 barrel Holley) and buy a new carb. Also I am going to consider replacing the fuel pump and all of the fuel lines.


And thank you very much by the way!

Now the question is if i should go ahead and go to EFI or replace all of these parts.

If you can actually SEE crap in the fuel tank - and after it sitting for two years it could be anything - moisture etc... and also the "new" fuels tend to not be so compatible with older rubber fuel lines and even the older rubber diaphragms in some fuel pumps. Several manufactures had issues with their good old METAL parts in carbs with the new fuels causing all manor of corrosion and stuff...

We don't know how old ANY of these parts are or their origins...

So --- if it was my car and I was having these issues and wanted to spend as little as I could - then I'd be removing and flushing the fuel tank... and replacing any of the "rubber" or flex lines with new - and make certain they are compatible with todays fuels (many people don't even know that you can buy different types of fuel line)... I'd replace or clean any filters.... I'd probably just go ahead and replace the fuel pump since you don't know what's inside of it... and I'd have the carb disassembled and inspected ------- or do as you have mentioned - replaced with a different manifold and a single carb. My guess is that you have a whole bunch of "fuel" related issues. The car should fire right off cold or otherwise with good fuel and properly tuned. That's not to say it will run or idle well "cold" -- that depends on the choke - etc if it even has one (doubtful).


RE: EFI conversion.

This would cost more... as you'd replace the tank with an in tank EFI electric fuel pump - it would require some wiring and relays etc.... you'd still want to replace any rubber hose in the fuel line... and you'd need to buy the type/style EFI intake and system that you'd wan to convert too. Then depending on whether or not you choose a "tunable" system - you'd have dyno and tuning expense... or choose a self tuning system - and skip that... but sounds like maybe you're the guy that would have all of this done at a shop. KaCHING....

The value would depend on how much you drive it - and whether or not you just want EFI. A carb or EFI are going to make the same power... The EFI is more tunable for certain things... and they generally start and run better "cold" or "hot"... but that, to me, is just nonsense if you don't drive the car that much... I have EFI on all my street rods... and a carb on the Mustang track car.... I can tell you that the Mustang lights off and runs within about half a revolution... and has no choke... so big deal - I feather the gas a little. It runs REALLY REALLY WELL... I have no intention of changing it over to EFI!

Depending on who's doing the work - the cleaning and changing a few hoses and the fuel pump - and inspecting or rebuilding the carbs - might be $2500 worth of labor and parts.... EFI is going to be 5 or 6 grand easily. Can be much more depending on what EFI you choose.... and then it's the "here we go, we might as well do....."


The main point is -- this bad boy should light off instantly.... Doesn't make any difference if it's a 540 -- or a 747.... a well tuned motor should fire with authority... if it doesn't - then you need to find out why. It's fuel / air / spark.... get 'em right or fight the fight.