fuel problem...flooding

[terrymac]

Thanks to everyone for the input the problem seems to be fixed. I seem to be lacking the snap in the bottom end that I expected. After talking to different people the concensis is I'm over carburated and not getting enough air...good excuse for a blower. Would not re-jetting to smaller jets help this. Drivablilty is great no boogs works great once the revs are up. My thought is smaller jets less fuel more air

 

[bucketkids]

Dang sure got my curiosity peeked so don't forget to fill us in on the end. Years ago, about 25 I aint that old LOL, when you changed a fuel filter in a chevy (screwed into the carburator) you would get a little piece of dirt between the needle and the seat. You pinched the line till the engine died, let go and restart. The floats would be down and the fuel flow would blow the crap out stuck in there between needle and seat. Shame about the lack of attention from the vendor.

 

[Screaming Metal]

Thanks to everyone for the input the problem seems to be fixed. I seem to be lacking the snap in the bottom end that I expected. After talking to different people the concensis is I'm over carburated and not getting enough air...good excuse for a blower. Would not re-jetting to smaller jets help this. Drivablilty is great no boogs works great once the revs are up. My thought is smaller jets less fuel more air

Oh Terrymac.........too much carb???????when someone tells me that....I just smile.......get more cubic inches! Ha! Are you running a 2-4bbl lowrise??? Or are you running a 2-4bbl. on a tunnelram?

If your over carburated......your over-carbed.........now if your running too rich, now thats another ball game! Over carbed......you gotta keep your rpm's up......a progressive linkagewill help..... a little smaller carb will do.....but if you feel brave, and are mechanically inclined.......run off the first 2 bbls. of your front carb, disconnecting the rear 2 and not running them. As you throttle is opened up and engine rpm comes up so it can take the extra cfm.....have the rear carb come on in. Just because you have all those barrels.....doesn't mean you gotta use them.

A setup like that.....it just might solve your problem of the exrta cfm and really put a smile on your face.....

 

[terrymac]

I'm running a 4 bolt 350 .030 over with 9.5/1 hemmel pistons 194 heads cam is 490 lift and i forget around 300 duration. 2 500 cfm edelbrocks on a low rise edelbrock intake with progessive linkage set up running on the primary on the rear carb. I'm running as much timing as I dare on a stock HEI distributor. I expected wheel spinning gut knotting go. The car works good no flats or boogs is quite responsive and goes like crazy once the revs are up. I have 18" wide Mickeys on the rear that bite real good so maybe I'm expecting too much. I tried un hooking the front carb but really didn't see much difference in the bottom end

 

[Wild Mango]

Sounds like the advance isn't coming in fast enough. Light car like a bucket you can tolerate most or all of the advance in by 2500rpm. With all that carbs she won't be lean downstairs so try setting the total advance to say 36 degrees and then go to the other end and put some light springs in the distributor. The odd scattered ping when you hop on it is OK, just so long as it doesn't sound like a chinese kitchen collapsing in an earthquake.

 

[Screaming Metal]

Sounds like the advance isn't coming in fast enough. Light car like a bucket you can tolerate most or all of the advance in by 2500rpm. With all that carbs she won't be lean downstairs so try setting the total advance to say 36 degrees and then go to the other end and put some light springs in the distributor. The odd scattered ping when you hop on it is OK, just so long as it doesn't sound like a chinese kitchen collapsing in an earthquake.

Mango I believe has it...............:razz:

 

[Screaming Metal]

I'm running a 4 bolt 350 .030 over with 9.5/1 hemmel pistons 194 heads cam is 490 lift and i forget around 300 duration. 2 500 cfm edelbrocks on a low rise edelbrock intake with progessive linkage set up running on the primary on the rear carb. I'm running as much timing as I dare on a stock HEI distributor. I expected wheel spinning gut knotting go. The car works good no flats or boogs is quite responsive and goes like crazy once the revs are up. I have 18" wide Mickeys on the rear that bite real good so maybe I'm expecting too much. I tried un hooking the front carb but really didn't see much difference in the bottom end

Terrymac, is it 300 @.050....??????????? Whats your centerlines??????..........I believe we've found some of your problem. This much cam......will take a lot of carb......but only up high where the engine can us it. Its probably best to be running 390's or even 450's.......but I've had customers rum twin 500's and 600's with little or no problems........they just feather the pedal until they get away from the light..........

You said it runs good and is responsive........after the R's are up........mucho cam timing. You cantame down your timing by running variable lift lifters which will bring up more of your bottom end.......but then your gonna have stumble because of those 2 500's honking down low.....and your engine won't bog.....it'll probably try to backfire thru the intake or just die.

Now that we know more about whats going on.....some of the others can give you some more info...........

 

[terrymac]

I took the car to "PA Racing engines" Man that is one smart guy. He reworked the distributor customized the vacumn advance and reset the mixture screws. Huge difference not the same car at all

. His advise to get more bottom end than I have is to lose one carb. His question was do I want more power to win races or the look. I guess I have the best comprimize . I still have to be careful how I park or the syphoning will take over. I'm trying to find a frame mounted fuel shut off a diesel but I can't remember what they're on. Would be an easy fix just a keyed wire to the solenoid. I've seen them so I know they're out there
Thanks everybody for the input

 

[Screaming Metal]

Hey terrymac....if its a tunnelram andnot a low profile 2-4 setup......put a single 4 on the tunnelram.....still look cool............... Glad to hear it doing better..................

 

[Mike]

Here's a really good rule of thumb to use for carburetor selection -

(Cubic Inches X Maximum RPM)/3456

All the "I've got a pair of 1050's on my 327" guys are going to wade in here screaming at me, but lets look at your application.

You have a 355" motor. What's the maximum RPM you see with this combination? Do you ever screw it up to 6,000?

(355 X 6000)/3456 = 616 CFM

Maybe you're brave and you run it up to 7,000? 719 CFM

8,000 RPM? 821 CFM.

9,000 RPM? 924 CFM.

10,000 RPM? 1027 CFM. Ahhh, now we're finally reached the flow capacity limit of your carbs.

But let's start looking at this realistically. What is the maximum RPM on this motor in normal driving conditions? I bet you rarely run it up to 4,500. That's 462 CFM.

300 of duration means a lot of overlap. A lot of overlap means a loss in manifold vacuum. A loss in manifold vacuum means a weak signal to the carb/s. Carbs are pressure differential devices and when a carb doesn't see much differential, it gets lost. So the carb is going to be sitting there waiting for air speed to pick up through the venturis before it starts to understand what the heck is going on. And that isn't going to happen until the motor starts to get upstairs.

I've been watching this happen for more years than I can count. A customer walks in the door with a wad of cash in his hand. His buddy told him to get a set of double-hump heads, a set of 12.5:1 pistons and a 302 camshaft, a tunnel ram and 2 750 CFM double pumpers for his street-driven 4X4 pickup with 33" tires and 3.08:1 gears.

What do you mean I will have to run race fuel in this engine, I plan to pull my boat to the lake with this truck. What do you mean I'm going to have to put lower gears in? Won't that kill my mileage on the way to the lake? And why do I need a looser convertor? And I think the stock valve springs will be OK, they still have 85 lbs of seat.

Start at the opposite end of things. How are you planning to drive the car? On the street? Long distances, are they a possibility? If so, then you are likely wanting to use pump gas. So a lot of compression is a no-no. Where is the motor going to spend the majority of its running time? At 3,000 RPM? Then build everything with that in mind, so the engine can be happy at 3,000 RPM. That means 'think small'. Small runners in the heads and intake. Small valves. Small cam profiles. Small carbs.

Need a visual to see what I'm talking about? Go outside, take the nozzle off your garden hose and turn the water on. Go ahead, turn it on full blast. How far is the water shooting out of the hose? Now, take your thumb and reduce the opening at the end of the hose. What just happened to that stream of water? Air does the same thing in a runner as water in a hose.

Same with intake manifolds. Take a plastic soda bottle and pull a vacuum on it with your mouth. See the bottle collapse? Now, take a five gallon jug and pull a vacuum on it with your mouth. Your vacuum ability gets lost with that additional volume, doesn't it?

Again, the bigger-is-always-better guys are going to flame me for this one, but don't let them fool you. If I just spent $10K on a sheet-metal intake and a pair of whiz-bang, double throw-down Dominators, then that is going to be the hot lick too. I don't want you to see me fuming because my investment won't work.

Do you want to have things look good? Or do you want performance to rip your head off?

 

[putz]

I believe stuff like your carb calculation should be in the tech department.I found the tire diagram and moved that over after a suggestion from a new person.

 

[Screaming Metal]

Yea Mike.....its hard to explain to some people that you gotta get the equipment that fits the situation........you don't need a 5 lb. Drilling hammer to set your keepers in your spring retainers when you do that valvejob.......