Carburetor Question (To Jet or to Go Up In CFM)

[KyleSeal]

What I need to know: do I need to rejet my Edelbrock? I have a 454 BBC with a larger cam and Edelbrock Performer RPM. My problems all started with the Holley no longer cooperating, backfiring through the carb, bucking at low RPMs, and dying at idle sometimes. So I moved down to a 600 CFM 1405 Eddy, and it actually starts. But I have to keep it at 2 grand to keep it running. Unlike the Holley, which would barley run at all.

So do I need to put bigger jets in it? I assume its stock. We've messed with the idle screws and mixture screws some but not much difference.

Or should I move to a 650 CFM? I know whatever I get I will also buy the tuning kit for it.

Originally I had a 750 Double Pumper with mechanical secondaries and it flooded the engine like crazy. My spark plugs were done in nearly a month.

and yes I know I'll lose top end power with the smaller sized carb. But honestly all I need is a good sounding truck. After all 1 ton's were not known for being fast. Just scaring ricers.

Thanks in advance, also if theres anywhere else I should check for problems please let me know. I'm learning.

[Marshy]

Nice truck!

Did you check your ignition timing since the truck started acing up? If not you might want to throw a light on it and check that its still good.

Regarding the Eddy carb, google search for the users manual. You can down load the full manual that will show you proper carb setup for the 1405 and what jet/rod/spring setup to use for your desired AFR. It also gives instructions on setting the idle mix too. Without using an O2 sensor to read A/F ratio I don't know how you would be able to tell which jets you need to move to. There is a chart/graph in the back of the manual which will help you make your selection.

[geezer#99]

If you're running the eddy, you need a fuel pressure regulator set at 5 psi.
Likely thats all you needed with the holley too!

[KyleSeal]

I actually could not check the timing. What was happening was the truck was feeling like it was misfiring and would be really boggy, especially after a gear shift. I'd nearly need to be on the floor just to keep it from dying (good 5 gallons of gas left). It died on the way home, backfired thru the carb, and I let it cool off a little, and it would give me trouble starting but since I was just a mile from home I just let it bog and act up until I got it home, I thought it was vapor lock.. come to find out the next morning a cold start showed the same backfire! We've mainly been trying to get it to run long enough to heat up to check timing. But the fouled spark plugs and split spark plug wire led me to believe it was really rich running.

Originally Posted by Marshy

Nice truck!

Did you check your ignition timing since the truck started acing up? If not you might want to throw a light on it and check that its still good.

Regarding the Eddy carb, google search for the users manual. You can down load the full manual that will show you proper carb setup for the 1405 and what jet/rod/spring setup to use for your desired AFR. It also gives instructions on setting the idle mix too. Without using an O2 sensor to read A/F ratio I don't know how you would be able to tell which jets you need to move to. There is a chart/graph in the back of the manual which will help you make your selection.

[KyleSeal]

How would a fuel pressure regulator help? I've never researched them, nor have I had one, so I am curious as to what it would do in my given situation.

Originally Posted by geezer#99

If you're running the eddy, you need a fuel pressure regulator set at 5 psi.
Likely thats all you needed with the holley too!

[Marshy]

Originally Posted by KyleSeal

How would a fuel pressure regulator help? I've never researched them, nor have I had one, so I am curious as to what it would do in my given situation.

If your pump is providing too much fuel psi then fuel can push past the float valve, raise the fuel level in the bowl and cause a rich condition. If you are unsure what psi your pump is providing you could go get some hardware and a cheap fuel psi gauge to check it before buying a new pump or regulator for a problem that might not exist.

Eddy manual:
http://www.edelbrock.com/automotive/...404_manual.pdf

From page 8:
Fuel Pumps and Pressure
Avoid extremes in fuel pressure. At IDLE, there should not be any more than 6.0 psi; if the vehicle has an adjustable fuel-pressure regulator, set it to 5.5 psi. With most fuel pumps the minimum fuel pressure is encountered at high rpm and WOT. Fuel pressure should not drop below 2.0 psi. If it does, a fuel pump with more capacity may be required. Note that some later model vehicles (the 5.0L Ford is one example) have mechanical pumps that will give more than 6.0 psi at idle. The vehicle will perform well, but may be prone to stalls on quick turns and stops with the clutch disengaged. If this problem occurs, check the fuel pressure. If it is more than 6.0 psi at IDLE, it should be reduced through the use of a regulator, such as Edelbrock #8190, or by creating a restricted by-pass bleed to the fuel return line. Edelbrock Street Fuel Pumps are highly recommended for all Edelbrock Performer Series carburetor installations.

[KyleSeal]

Also Marshy - thanks for the compliment on the truck. My uncle bought it in 87 from the original owner. Its completely stock ('sides the lift kit) and I remember being on the farm as a little kid in 98-99 sitting on the hood and in the seat. I actually have a photo of me sitting on it as a kid. I'm only 20 and want to keep it running and driving for my future family to see!

[Marshy]

Awesome.

You should double check the initial timing. Maybe you can borrow a llight from a friend? If you can manage to get it to idle, just make sure you unhook the vacuum advance hose so that you are reading just the mechanical advance by the distributor.

Carbs don't typically cause a sudden change in performance like you have described. They can get dirty and stuff but don't usually crap the bed and leave you limping home. You need to troubleshoot more before replacing/changing anything else.

[Marshy]

You Tube

I hope that imbedded correctly...

Full link is here: https://www.youtube.com/watch?v=wR_AfQjyT-A

[truckster]

Backfiring through the carb makes me think timing. It could be the ignition timing (if you're lucky) or it could be that you slipped a tooth or two on your timing chain. Either of those conditions can cause backfiring through the carb.

[Marshy]

Originally Posted by truckster

Backfiring through the carb makes me think timing. It could be the ignition timing (if you're lucky) or it could be that you slipped a tooth or two on your timing chain. Either of those conditions can cause backfiring through the carb.

I agree. That's where my mind was taking me. Hopefully ignition only.

[KyleSeal]

But the thing is, once I threw the Edelbrock on, I have had no backfiring at all. Not even close.
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[KyleSeal]

Also, it wasn't a big fire ball like you see when they normally backfire, this was like white smoke filling up the air cleaner, and puffing a little. Nothing 'major'. Prior to all of this, the truck would have some problems starting once warmed up. I thought it was a starter heat soak issue, but it doesn't seem it is. Also prior to this me and my father were messing with the idle speed, dropping it from a 1800 idle to a 1200 idle.
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[cableguy0]

You shouldn't be anywhere near 1200rpm at idle. A stock engine should idle at about 750 or so in park and about 600rpm in drive. You need to check your timing and get it correct first. After that work on the carb.

[KyleSeal]

It has a rather large cam in it that causes the high/rough idle.
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[geezer#99]

Originally Posted by KyleSeal

It has a rather large cam in it that causes the high/rough idle.
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You shouldn't have any problem getting it to idle at 750 rpm if your timing and carb are set right.
Your white smoke out of the carb is fuel vapor from flooding.

[cableguy0]

Originally Posted by KyleSeal

It has a rather large cam in it that causes the high/rough idle.
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What size is the cam? My last small block idled at 800rpm with a .550 lift 246@.050 duration cam. No reason you shouldn't be idling under 1k. Idling at 1200 takes you completely off of the idle circuit. Your constantly going to have flooding issues because you are pulling fuel through the jets.

[KyleSeal]

I'm not sure on the size of the cam. All I know is that it's a huge cam, making it a really rough idle anywhere below 1200.
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[Marshy]

Originally Posted by KyleSeal

I'm not sure on the size of the cam. All I know is that it's a huge cam, making it a really rough idle anywhere below 1200.
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Well according to Edelbrock's application chart, the 1405 carb is good for 400+ ci but does recommend cam duration not to exceed 220* (@ 0.05 lift). The 750 cfm carbs are good for cams up to 230* and 800 cfm carbs are 240* duration. If you have a really large duration you are likely causing your own misery. What model was the Holly? It sounds like you need to be running a larger carb to me. Without checking your timing you are just taking shots in the dark.

Eddy Application chart:
http://www.edelbrock.com/advertising...hart_03186.pdf

[geezer#99]

Originally Posted by KyleSeal

I'm not sure on the size of the cam. All I know is that it's a huge cam, making it a really rough idle anywhere below 1200.
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First fix your flooding problem with a regulator and then put a proper timing curve in it and it'll idle at 750 rpm.

You'll have twice the power and stop wasting all that gas.

[storm9c1]

I agree with others. The first thing you have to do when you swap to an Eddy is check fuel pressure. If you don't want to bother with a regulator, take the hit and buy an Eddy fuel pump. For the BBC, the PN is 1722. No regulator required with that pump.

I also agree that you should check the timing as well just to be sure.

[KyleSeal]

The only reason why I don't believe the timing is bad is because once the Edelbrock went on it fired up every try. The 750 it would start once and then just turn and turn and turn. That's why I believe I need to downside the carb to a 600/650. But once I find out for sure what cam I have I will double check everything. And our timing light actually for some reason just quit working. So we're in the dark for timing at the moment.
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[KyleSeal]

http://www.jegs.com/i/COMP-Cams/249/CL11-602-4/10002/-1
There's the cam. Also an Eddy Performer RPM intake.
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[AcampoDave]

Originally Posted by KyleSeal

The only reason why I don't believe the timing is bad is because once the Edelbrock went on it fired up every try. The 750 it would start once and then just turn and turn and turn. That's why I believe I need to downside the carb to a 600/650. But once I find out for sure what cam I have I will double check everything. And our timing light actually for some reason just quit working. So we're in the dark for timing at the moment.
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You know what they say, "Timing is everything" I wouldn't even spend another dollar on the motor until I bought a new timing light first.

[Marshy]

So here's the thing... You'll never figure it out unless you troubleshoot. You always start with the easiest/most obvious things. Checking timing is a must IMO. Its also not the only thing to check but its the easiest so get that out of the way.

Your original questions were
1) do I need to rejet my Edelbrock?
2) should I move to a 650 CFM?
3) if theres anywhere else I should check for problems please let me know

The answers were;
1) possibly need a rejet although Edelbrock does not recommend the 600 cfm carb for an engine with cam duration over 220 @ 0.050" lift and you are running a cam with 243* duration. That in itself could make it difficult to resolve your initial problem. It was also pointed out that with a 1200 rpm idle you are now on the power circuit of the carb and the idle screws are no longer at play. That alone means you cent even begin to dial that cab in properly without getting initial timing and idle speed set properly.

2) Edelbrock actually recommends their 800 cmf carb given the large cam duration you have.

3) As we all keep saying, proper timing is the first step. Get the initial timing at about 10-12 degrees at 650-750 rpm then adjust the idle mix screws. If your ignition timing is too low then it will have a hard time idling and you will have to compensate by turn your idle speed screw (not mix screws) in more which opens the main butterfly to get your rpm up. This combined with the retard timing will also make it want to keep firing when you shut it off.

So, start with timing then move to the carb. Good luck.