Losing my Mind, 340 Six pack wont pull

Been Fighting it since i got the car running. Every time i go to get on it the car will simply cut out and wont pull anything past 3100rpm. Pulls fine till then but after that it hits a wall. I want to make it work and not just toss a 4 barrel on it.
Heres what i have done already,
New ECU
New Dist pick up
New Ballast resistor
Timing at 10 Deg and no vacuum advance total timing at 36
All carbs have been gone through fully
Changed out secondary springs to differnt colors light to heavy springs and still the same
Car Has new valve springs, cam and lifter
14-15 vacuum at idle
63 main jets and stock secondarys.
Idles and free revs great. no hesitiation.
new fuel filter.
Plugs are RN9YC @ .040 gap

Insight would be apprecated to who ever has owned one of these animals.

What is the psi of the fuel pump? Are you positive the secondaries are opening?

The one aspect of trying it with a 4bbl is.......it will help point you where to look for the problem.

If the 4bbl fixes it, it's a carb problem.......and visa-versa.

6psi and yes they are opening. Set a gopro under the hood to verify.

Wire the secondaries closed and see what happens.

Are the carbs original or repros? The reproduction carbs have the little things that the original carbs had wrong ironed out.

That will not work out very well. If you want no secondary opening then disconnect the vacuum lines to the outboards.

1.Have you set the fuel level corekt in the carbs ?
2. I would try to open the outer carbs whit engine on idel on the center carb and see if the engine responce like it should on those carbs to verify that they give the engine fuel.

I have not done any work on the sb 6-pack but on the bb they like larger main jets for preformance like 66-68.

It shore sounds like the outer carbs dont deliver fuel to the engine so are they assembeld corekt whit the corekt gaskets for the jet plates so the fuel holes aint plugd !?

Jerry Binder wrote a realy good articel that explain alot on the 6-pack carbs that i can email you if you like !?

I don't see new fuel pump on your list.

You could be plugged off at the tank too with this crap they call "fuel" these days. Could be load of poo in there blocking your fuel lines.

I ran into that years ago. I worked at a garage and a local guy had a Ramcharger that he put a 440 in. He had the machine shop build the engine and he put it in. It done the exact same thing. Sounded good at idle and would rev like crazy. He changed everything atleast 2 times and finally give up. I pulled the timing cover and the timing chain was off 2 teeth. I lined it up and it would pull to 6000rpm no problem. Before it would go to 3000 and stop. Even holding it to the floor it would set at 3000 all day long.

(1) I'd T into the fuel line & see what psi you have "at speed" when it acts up. (2) Will it rev up normal like you want it to in your driveway? on the second suggestion, the fuel requirement wouldn't be the same cuz of the minimal load but you should be able to load it ign wise pretty good by gunning it to pin it to ign or fuel. keep us posted. & when it acts up does it spit & sputter or wont go any higher but is smooth or something else?

Robert's questions are good even though it seems like you may have answered them.
Is 6 psi at WOT all the way to 3100 in 3rd or 4 gear?
Fuel consumption under load is much higher than in N. I'd expect 3-5 psi down the track. That would indicate the fuel inlet valves are open. Your description sounds like it won't go past 3100 in 1st or 2nd. How about on the highway (Interstate)? Will it go to 3200-3300 cruising at 70-75 mph or whatever your gearing works to?

Honestly, if its just hitting like a wall like a rev limiter then I would not suspect fuel. I've made it through the lights with fuel pressure at zero (there was enough in the bowls to just make it although it sure wasn't best time) and I've run on 2 barrels (out of 4) to 6000 rpm in 3rd on the dyno. It reduces acceleration but doesn't kill it or even close.

See if i can reply to everything asked.

All new fuel lines, tank and sending unit.

we put the secondarys to direct vacuum and reved it, the secondarys are working and dumping fuel.

The carb rebuild kits came from quick fuel.

going 75 in 4th is got nothing left in it. it just falls on ots face.

Ill see about fuel psi under load and see what happens.

I had that problem on a customers car...Took me a couple of days to find out that the rubber hose back by the gas tank was closing up under load..

If it's not fuel then it's a volumetric efficiency issue.
Try this: Bring engine to operating temp. Place vacuum gauge to read manifold vacuum. Record vacuum reading at idle in park or neutral. Bring engine rpm up to 2500, hold, read vacuum gauge.
Is the vacuum reading at 2500rpm the same or higher than the reading at idle? It should be same or higher.

If it's lower at 2500 rpm then it's a breathing problem.
#1 Cam timing is incorrect. Remove valve cover, bring engine to TDC on exhaust stroke (360* from TDC compression stroke) using piston stop. Don't rely on dampner markings or timing chain markings.
Inspect intake and exhaust rocker action as you rotate engine back and forth no more than 10*. Are both valves being activated? Exhaust closing and intake opening? If only one valve is moving then cam timing is off by at least one tooth.
#2 If cam timing is correct then a collapsed muffler or double walled exhaust pipe is restricting airflow.

So this is basically cruising. Yes?
The motor is at 3100, car going 75 mph in 4th.
So a test to determine if it is rpm related is to take it 70 or 75 mph in 3rd. That you could still safely do on a public road.

Testing fuel pressure while driving takes a little bit of effort to arrange a visible gage safely. Lots of option but take your time on doing that right. Cost of an error is too high.

When I've needed to check fuel pressure at wot on the road, I just tape a small mechanical gauge to the windshield right where I can easily see it.

Although there was talk of a go-pro....... So I guess the gauge could be anywhere the camera could get a good look at it.

Sounds like fuel, it comes right back after the rpm decreases below the problem rpm? Have you check rotor phasing? Msd has a good video on it. Mine was just like the before video! DOH! Also check the burn pattern on the distributor terminals. Is it in the right spot? I chased this for a good bit of time!

Vibration dampener all in order? Possibly running extremely retarded if timing mark on dampener has shifted, causing ignition timing setting inaccurate.

Even with secondary carbs disabled, should get at least 5 grand on center carb alone.

What does your vacuum gauge read at wide open throttle at 3000 rpm. What does it read at idle?

What is voltage at positive coil wire post. Should be st 12 volts unless thru ballast resistor., then 8 plus volts.

No huge vacuum leaks such as power brake or pcv disconnected. Unlikely to cause this,,,never know.

Excessively weak valve springs. Forget if this has been checked.

I also like valve timing suggestions.

Just did the vacuum test and in fact it is losing its vacuum as it revs. Did a quick comp test and 80psi all around. Gonna let it cool off then pull the cover yet tonight

Ill be pulling the timing cover off tonight since i see comp is way down all around

Sounds like your on to something.

post what it ends up being.

What's interesting about the "it won't rev because of the cam timing" hypothesis is......modern cars with VVT can move the cams around 50 degrees.......and they rev just fine.

I agree the 90psi cranking pressure needs looking into.

I thought the vacuum reading test was a check for plugged catalytic converters(or other exhaust restrictions).

I'll be interested to see what's found when the timing cover is removed.

If the cam is retarded 2.5 teeth(35 deg) as someone mentioned, I would think there's a good possibility of some bent exhaust valves.

soo i installed the cam straight up and didnt even look at the damn cam card....

http://www.lunatipower.com/CamSpecCard.aspx?partNumber=60403

By the looks of it i should advance it 4 degrees


Been a long ass time since i delt with a gasser

If you just lined up the dots it SHOULD be 4*'s ahead.

Something's up with your 80 psi of compression, either you've got 5:1 compression or the cam is way off

so by right's i am 4deg advanced. i should be using the -4 to be straight up. correct?

that would likely get you "close" to straight up. I don't think that is the problem tho especially since advancing the cam would bump the cranking compression #. Keep digging, the 80 lbs is what Sherlock Holmes would call a serious clue.

Most cams are ground with 4* advance into them so if you line up the dots the cam will be installed where the cam grinder wanted it.

Dot to dot SHOULD be in at 106 where the card says. If you retard it 4 you SHOULD be at 110.

The only way to know for sure where it is is by degreeing the cam in. I've seen some weird stuff over the years. You could have some tolerance stack up and have it be way off. But I'd bet it's pretty close to 106. You just need to verify that.

Sounds like a cam timing problem or ignition timing issue.

You could use the split overlap method to see if your lifters are about equally off the base circle at TDC at end of exhaust stroke.
It's quick and dirty.

I've had a sticking mechanical advance do something similar.
R.

If you have a vac plate in your dizzy, make sure its not grounding out, might not apply her but I had a gm points dizzy do this.

I feel like a moron now..... Checked the timing marks and i thought they were good. Had my brother look at it and pointed out i had lined it up with the key way and not the actual mark.... Put it on right and 140psi cold. Have the timing cover to toss on but ill report back in the morning.

Glad you found it. You're not the first to do that. You certainly won't be the last.

So, 2 1/2 teeth off........ 35deg.

I'd be doing a leak down test.

With the key straight up and the top gear dot straight down, the cam is advanced 2 1/2 teeth.
This almost always results in the intake valves running into the pistons...... Unless the valve pockets are really deep and/or the cam is really small.

So that means you still have not degreed it in? if degreed from the get go this would not have happened. Just saying.

This is why most of the stockish rebuilt 340/383/440's I have worked on can't get out of their own way. Its a stockish build so everyone figures its not worth 15hp or whatever HitRod picked up in their latest cam timing article. When it makes 200hp and can't bark the tires everyone blames the poor old engine. Glad you found a smoking gun. Now put the wheel to it before you button it back up!

It rips like a scaulded cat now! The cam isnt big by anymeans but everything was fine as for leak down and comp. Guess i got lucky. The old tired motor only has to last till i get the gen3 hemi built for it. Thanks for the advice guys

Welcome to the rookie mistake learning club
Next time degree IT

You sound pumped! enjoy! I learned something on this too.

Now fix the idle tune up because 10* is not a good setting, good for a stock 318, yes... anything else, no!

I ran 19 initial on both of my DD 318's, an 85 in a Ramcharger and an 83 from a cordoba.

Perfect example

https://board.moparts.org/ubbthreads/ubbt...tml#Post2304123

Still waiting on my stroker kit , but the machine shop said they would degree the cam while I was there , so I could watch and learn