Weird Edelbrock carb noise

[B736866]

Im having a weird noise come from my Edelbrock 1406 carb, fresh rebuild and all stock jets and needles. The motor is a sbc 307 all stock. Only mods are the edelbrock intake and carb and a new HEI distributor. The noise only happens at had acceleration. The timing is set at 10 degrees btdc.

<iframe width="420" height="315" src="https://www.youtube.com/embed/loiq3A0fh5k" frameborder="0" allowfullscreen></iframe>

or

https://www.youtube.com/watch?v=loiq...ature=youtu.be

[geezer#99]

Did you put all the intake bolts back in the right spots. There are short and long ones. Longer bolts can hang up on the pushrods.
Also sounds retarded.
Have you confirmed tdc #1 and your timing tab/mark are correct.

[B736866]

All of the bolts were the same length on the intake. How do I check to see if the timing mark is correct?

[geezer#99]

Did you use the stock bolts?
Here's a link for tdc.
http://www.crankshaftcoalition.com/w...op_dead_center

[B736866]

I can't say for sure that they are stock bolts because I am the forth owner. The TDC is correct. Could this be a timing chain issue?

[geezer#99]

Was it running with the eddy previously or is this a new carb/intake install and that's the noise you get?

Bump your timing up to 16 and see what it does.

[B736866]

The edelbrock intake and carb are new. When I got the truck it was running a holly 2bbl carb and stock intake.

[geezer#99]

Did you do anything else at the same time?
Like adjust valves maybe!
Have you checked the firing order?

[B736866]

Only other thing changed was the distributor. Yes, I triple checked the firing order to be sure it's right. I also replaced the wires. I have not checked the valves though.

[geezer#99]

Pop the cap on the dizzy and check the rotor is seated right.
Also look in the carb while idling. Could be flooding a touch. Eddy carbs don't like more than 5psi fuel pressure.
Did you bump the timing up?

[B736866]

I tried bumping up the timing today, still popping on hard acceleration. Also when I bump up the timing I can't get it to idle @ 600 rpm. I dropped the timing down to 4 btdc and that helped a bit but it's still popping. What am I looking for in the carb to see if it is floating?

[geezer#99]

Originally Posted by B736866

I tried bumping up the timing today, still popping on hard acceleration. Also when I bump up the timing I can't get it to idle @ 600 rpm. I dropped the timing down to 4 btdc and that helped a bit but it's still popping. What am I looking for in the carb to see if it is floating?

You're looking for any raw gas!
Should see none while it's idling.
Have you checked for vacuum leaks?
Do you have all the unused ports on the carb plugged off.

[hamjet]

I would put the old dizzy back in and see if it still acts the same or not...

[Zeke's Garage]

Can you hook up a vacuum gauge to the engine while it idles and see if it stays steady, or is fluctuating? Something sounds really odd. The way it revs really slow sounds like retarded timing, but it's tough to tell without putting hands on it. Verify TDC by using the piston, you can't trust an old harmonic balancer, they tend to slip on the rubber ring.
Sounds like more than one thing might be going on here, so also check your spark plugs.. its' really easy to crack the ceramic while handling them and you'll end up with a misfire.

Good luck with it.

[B736866]

Originally Posted by hamjet

I would put the old dizzy back in and see if it still acts the same or not...

I really appreciate all of the replies guys. This has me and my buddies stumped so all the help I can get is very helpful.
It was doing making this odd noise with the old points style distributor that is why I replaced it.
I will have to get my hands on a vacuum gauge and test it out. How do I use the piston to find TDC. I just used the finger over the spark plug trick in order to get TDC after I replaced the dizzy. Could this also be a result of a bad timing chain?

[B736866]

Originally Posted by hamjet

I would put the old dizzy back in and see if it still acts the same or not...

I really appreciate all of the replies guys. This has me and my buddies stumped so all the help I can get is very helpful.
It was making this same odd noise with the old points style distributor that is why I replaced it.

Originally Posted by Zeke's Garage

Can you hook up a vacuum gauge to the engine while it idles and see if it stays steady, or is fluctuating? Something sounds really odd. The way it revs really slow sounds like retarded timing, but it's tough to tell without putting hands on it. Verify TDC by using the piston, you can't trust an old harmonic balancer, they tend to slip on the rubber ring.
Sounds like more than one thing might be going on here, so also check your spark plugs.. its' really easy to crack the ceramic while handling them and you'll end up with a misfire.

Good luck with it.

I will have to get my hands on a vacuum gauge and test it out. How do I use the piston to find TDC. I just used the finger over the spark plug trick in order to get TDC after I replaced the dizzy. Could this also be a result of a bad timing chain?

[hamjet]

Originally Posted by B736866

The edelbrock intake and carb are new. When I got the truck it was running a holly 2bbl carb and stock intake.

was it doing it before you did any of the mods? If it was then yes, it could have jumped 1 tooth on the chain.

[B736866]

No it wasn't making any of these noises before the swap. It would struggle on hills that's why I upgraded.

[BrianG]

Wow, that thing is running rough. Sounds like some serious spark nock or something else going on in there. You might want to try popping the valve covers and seeing if all the rockers are moving up and down. Could be a worn cam lobe, a rocker just loose, or bent push rod. Could also be a jumped timing chain I suppose. Set the timing to spec. Check all the vacuum ports, caps, hoses, etc. again. Another idea which is a long shot and probably far from the problem would be to check the other end. Meaning what do you have for an exhaust. Could there be anything along the way creating a partial plug? Keep us informed on your progress.

[swamp rat]

I think i hear a vacume leak. that will affect your idle and how the engine runs.

Edelbrock 1406 carb has a vaccume port on the rear center just above the base, this is a mnanifold vacume port meaning it has the same vacume as the manifold, it would normally be routed to brake booster but you don't have one, did you plug the port?

The Edelbrock performer intake manifold also has a vacume port behind the carb mount as well, did you plug it? I missed mine once and got that same sound.

There are 2 small ports on the front of the carb, passanger side will go to your distributor, its a ported vacume, that means the vacume changes with throttle position or as the butterflys open and close, driver side will get plugged. The big center one will go to your PCV on the valve cover, make sure you have a good PCV valve.

When you set the timing you need to unhook the distributor vacume hose and cap off the port on the carb with a port plug, buy them at the auto parts store.

You do have a knock that isn't related to vacume loss, could be a bad lifter or exhaust leak.

[Zeke's Garage]

Originally Posted by B736866

I really appreciate all of the replies guys. This has me and my buddies stumped so all the help I can get is very helpful.
It was making this same odd noise with the old points style distributor that is why I replaced it.



I will have to get my hands on a vacuum gauge and test it out. How do I use the piston to find TDC. I just used the finger over the spark plug trick in order to get TDC after I replaced the dizzy. Could this also be a result of a bad timing chain?

If you checked TDC with your finger over the spark plug hole, and the mark on the balancer lined up with the pointer, then you should be good with that. It's just verifying that the balancer ring hasn't moved on you.

You say that it's popping when you accelerate hard, which could just be detonation, meaning that you need to back off your timing, or you have really bad gas in it. It could also mean a jumped timing chain or a stuck valve.

The vacuum gauge will tell you if you have a valve train problem, and potentially a valve timing problem by the level of vacuum you're able to obtain. Other than those non-invasive tests, you're looking at pulling the valve covers and the timing cover to inspect your rockers, studs, pushrods and timing chain.

[luvbowties]

Originally Posted by B736866

Im having a weird noise come from my Edelbrock 1406 carb, fresh rebuild and all stock jets and needles. The motor is a sbc 307 all stock. Only mods are the edelbrock intake and carb and a new HEI distributor. The noise only happens at had acceleration. The timing is set at 10 degrees btdc.

<iframe width="420" height="315" src="https://www.youtube.com/embed/loiq3A0fh5k" frameborder="0" allowfullscreen></iframe>

or

https://www.youtube.com/watch?v=loiq...ature=youtu.be

First to admit I don't hear well, but I'd bet a bit of $ I hear a vacuum leak. Adjust whatever you need to get it to idle by itself as close to 600 RPM as possible, with air cleaner off. Get a stiff piece of paper(cardboard?) that will cover complete carb top. Punch a hole in center so that it slides down along the air-clnr stud; slowly slide it down, choking the carb bit by bit. If engine speeds up & runs more level as the paper gets closer to carb, then fix your vacuum leak!
There are several ways to find leak after you determine you have one.
Sam

[DUDLEY]

I agree. Sounds like vacuum. Did you torque the manifold ?

[11SECSS]

Also recheck your firing order 18436572 as I've seen a lot people have the 5/7 backwards

[B736866]

I have checked and rechecked the firing order. Tomorrow I will look again for a vacuum leak using the cardboard trick. Today I pulled all the plugs and re gapped them to .45, it helped a bit but still making that noise. I will post a new tomorrow.