No power in 3rd gear. Carb issue?

[1971lubr]

My 302 was rebuilt long ago, has maybe 10k-15k on it. Since finishing up the resto and finally driving it again, I have no power in 3rd gear regardless of RPMS.

3 speed manual, stock 3.50 rear end with 31's. I ran 31's before the resto and it had tons of power. I'm thinking it's carb related? It has decent power and runs ok (not perfect, I feel like it has a miss) in 1st and 2nd, but in third there's nothing, even at 2,000 RPM I can put the pedal to the floor and it just slowly lugs up to speed. It's like the secondaries aren't even opening up. It's an Edelbrock 1405 4bbl. I did tear it down, clean it up, put in all new gaskets and a new accelerator pump. Am I looking at some sort of vacuum issue keeping it from opening up? Starts right up and idles great. Thoughts?

 

[blubuckaroo]

Try to resolve the miss. If it sounds like it has one or more cylinders not pulling their weight, you'll need to identify those.
I like to pull the wires from the distributor cap, one by one, I find the one that makes no difference in the idle speed. That'll be the culprit. Use insulated pliers for this!
From that point you'll need to check the condition of the plug and wire. You could use a known good wire and plug for this.
If none of this resolves the miss, I'd pull the intake manifold to examine the gasket. There have been many cases where aluminum manifolds have had leaky intake gaskets and had a hidden vacuum leak from the valley area.

 

[Broncobowsher]

Check your timing, make sure you are getting advance with RPM.

 

[DirtDonk]

You running a stock three-on-the-tree, or floor shift? If on the column, any wires for the ignition running down near the steering column and shift levers by any chance?
Just thinking that there should not be such a noticeable difference just from one gear to the next. Yes, I realize that it's going to struggle more in third than in the other gears, but the picture you're painting is of an extreme change just from 2nd to 3rd. Maybe something physical is at work.

Good luck.

Paul

 

[Unaweep]

Different vehicle but same problem. My Baja Bug had no power in the upper gears...turned out a buddy had pulled a spark plug wire off.

So to answer your problem - no power to a cylinder.

Erik

 

[nvrstuk]

So sitting in neutral you can hit the throttle and it's instant (near) throttle response?

As said before the super easy check is pulling plugs wires carefully to see if you have a dead cyl or two...

Also mentioned...check timing...it got bumped or more likely, you have zero advance. This will give you great response under Zero load, seem like you have decent power in the lower gears but ZIP in high at all rpms until you get up to 4k or so...

good luck, sounds like a simple fix

 

[1971lubr]

Paul, it's floor shift. Regarding wires, ransil and I checked each wire with a probe weeks ago and all had power. I guess that doesn't rule out 1 not putting out enough power though? Throttle response in neutral is pretty good, could be a little sharper IMO though. Timing has been advanced, maybe not enough? All good ideas to look into.

 

[B RON CO]

Hi, I like the check by removing 1 wire at a time. As mentioned, if there is no change in the engine, look closer at that cylinder. The engine should really shake when you remove a wire. Run the engine at night and see if the wires arc to each other. If you have points and condenser change them. 10-15K is the life of a set of points. Also see if you can manually open the secondary throttle, it may be stuck closed, but I think the engine should run better on just the primary throttle. So take a ride with the air cleaner off and make sure the air cleaner is not the restriction. You should also make sure the gas pedal fully opens the throttle. These simple suggestions may help, but if you feel there is a miss you have to get to the bottom of that. If all these suggestions don't fix it I would do a compression test. Good luck

 

[DirtDonk]

How long did the engine sit idle during the restoration? You might consider a compression check if none of the other ideas nets any obvious results.
You might just be way down on power overall. The 3.50's and 31's are not a bad street combo, but would really task a weak engine in the upper gears.

Paul

 

[jckkys]

The needs of the engine in 3rd gear are a result of increased load. High load exposes both ignition and carburetion problems. The carburetor needs to produce a richer mixture not more air volume. The secondaries are irrelevant, they only come into play at high RPM, likely well over 3000 in a little 302. A 600 cfm 4bbl on a little 302 rarely uses the secondaries at all. Power enrichment in an AFB is the function of the metering rods. If you didn't change the primary jets, rods or step up springs, the step up pistons may be sticking.
The engine needs a much stronger spark when under a load. The resistance of a higher compression mixture is also higher. The spark has to have more voltage. That means it needs better insulation. You need to check the coil, plug wires, distributor cap, and plugs. A Sun scope can narrow the search, so that's where I would start. The average full service gas station or automotive shop would be able to inexpensively provide this service.

 

[bronconut73]

A Sun Scope?
Really, you think any old service station will have one. If they do I hope they have an old feller there to run it. The kids working at a modern "service station" would even know how to turn it on, lol...

 

[1971lubr]

Paul, it sat for about 15 years, but the block was filled with oil to try to preserve it for that time. I suppose I could have developed a crack in the intake or head gasket (although no antifreeze/oil contamination I can find) over those years. I'm crossing my fingers it's not a bad cylinder or two.

This carb was tuned and jetted for Colorado, so it should be running lean down here in PA at 1500' of elevation. When I cleaned the carb up and put new gaskets in, I did not change the jets, step up springs, etc. I know those need changed, but I also drove it a little when I first moved here and it didn't run starved with the high altitude tuning way back then.

I've located an old school mechanic (old feller) nearby that was recommended by a guy that is a heavy collector of vintage cars & exotics. He's going to take a look at it next week and see if we can figure out exactly what the problem is.

 

[jckkys]

The scopes are common here largely because of the fact we have no rust and the tags for older vehicles are dirt cheap. Older pickups alone keep shops that work on them working. I got a Sun distributor machine from one of them, and one of the speed shops does timing curves. The Shell station a couple hundred feet from my house has a scope. I suppose the rust belt has lost the abillity to work on carburetors and distributor ignitions. Even here it's getting hard to find a tranny shop that can do a quality rebuild on a C4.

 

[1971lubr]

Played around with the timing this morning and discovered that the mechanical advance wasn't working in a new distributor. Opened it up and one spring was heavier than the other. Removed the heavy spring and the mechanical advance is working now. Set timing to 10° and its running better now. Going to have to get a new spring to replace the heavy one. Carb needs dialed in as well.

 

[SHX669]

What distributor do you have and is it all mechanical or vacum and mechanical advance

 

[1971lubr]

Mechanical and vacuum. I ordered an 81 F150 distributor since I pulled the duraspark from an early 80's pickup.

 

[jckkys]

The heavy and light springs are in most Ford electronic and point distributors. You need 2 light springs like the Crane and Mr. Gasket kits at Summit. Here;https://www.summitracing.com/search/Part-Type/Distributor-Advance-Kits/Make/FORD
The Crane kit also includes a US made adjustable vacuum advance diaphragm and instructions to set up a custom advance curve for both centrifugal and vacuum advances.
Here;http://www.fordmuscle.com/archives/2000/03/timing/index.shtml,is a great informative article on this.

 

[jckkys]

The Ford Muscle article didn't paste. I'll try again;http://www.fordmuscle.com/archives/2000/03/timing/index.shtml

 

[1971lubr]

The Ford Muscle article didn't paste. I'll try again;http://www.fordmuscle.com/archives/2000/03/timing/index.shtml

Excellent! Thanks!

 

[1971lubr]

Pulled the light spring from the old points distributor and put it in. I think I lost mechanical again. Running like it was before removing the heavy spring completely.