Hot Rods H.A.M.B. brains needed

Any chance that when the engine torques, it is shorting out the power to the ignition? Easy to check for burned wire or put a piggyback spade connector on the power wire and run a wire to a volunteer inside the car. Have a friend watch it.

 

Add some timing..........mix well......
Try again and continue to add timing until it rattles going up a hill in top gear.

 

Me thinks it's a fuel delivery problem also. It could be that the fuel bowl is low enough at part throttle that pressing down the accelerator is using what is left in there with the remaining pump shot, and you are getting instant bog. You could have a restriction in it and still have adequate fuel pressure at low speed or at idle I have also seen air cleaner restrictions act in somewhat the same manner, but given your previous issues with the fuel system, that is where I would look. Disconnect the fuel line at both ends and make sure it is clear. Drop the tank if needed and look at the fuel pickup, and make sure it is clear.

 

What kind of intake do you have? Friend had a 350 that would do the same thing, run fine as long as you didn’t punch it. He had a rather tall single plane with a thick carb spacer. We took out the spacer and changed the squirter cam (Holley), it was starving on acceleration. Too much air and not enough fuel until you let out and closed the throttle blades a bit. Worked great after after we did that.

 

I would hook up a fuel pressure gauge and a timing light, stick the timing light under the windshield wiper or duct tape it to the hood so you can see the " flash pattern " if the flash appears to falter when the engine does you know it's ignition, same with the fuel pressure....you can hook the gauge up temporarily in the same manner if you don't want it permanent....one more thing, if you just recently had to start using the ethanol blend shit we get in New Jersey you may just need to richen up which ever carburetor you choose....they could POSSIBLY all be lean if they ran good without the ethanol....you know i also heard about some distributors with vacuum advance having a broken ground wire from the breaker plate to the dizzy body and they get some ground until the vacuum advance is full in....

 

Check and make sure the Vacuum advance is not stuck. Check the fuel flow first, then look at the vacuum advance and make sure it's working. I had the same type of problem in my Roadster, and it's Ford powered, but it was the vacuum advance was stuck.

 

Make sure the fuel tank is vented correctly also check to see if your air cleaner lid is not so close to the bowl vents that its choking it off.

 

If it has HEI, hook up a vacuum hose to the advance and suck on it while engine is running. The small green and yellow wires from the pick-up coil move every time the advance does, over time the go bad. While cruising, the vacuum is pretty steady, WOT, it drops quickly, something to look at anyway.

Timing light under wiper blade is a really good idea to separate electrical from fuel problem. A tachometer should show same thing if you watch it closely.

 

Check fuel filter/strainer right at carb. Went through this same issue, with on old C10 I drove. Cruise down highway right as rain, but try to give it some decent throttle to pass, and truck would fall flat on its face. Filter was plugged in the carb, would flow enough to maintain steady state cruise, but not enough to accelerate.

 

Quote from original post 1; “Missing something....... please share thoughts.”

If none of the previous 40 odd posts on vacuum and fuel blockages don’t come to anything, my question would be does the auto match the application ?

 

Disconnect the vacuum advance, plug the hose, see if it still stumbles, this will give you an idea if the pick up wires in distributor are disconnecting when vacuum advance plate moves.

 

What head and what spark plug are you using - you've replaced everything but the concrete the car sits on, I'm wondering if maybe you have aluminum heads with a speak plug designed for the cast iron head or something simple like that. They'll thread in fine and work decent enough until a load is applied, when replaced you buy a new set of the same plug number. I've seen it happen. The other critical thing is it a 'projected' plug designed for todays' fuel? A traditional non-projected plug that we've used for years would work fine when first installed but degrade quickly.
I hope it is something simple as the wrong plug type, you've probably got the right ones as I see you are thorough but the question needs asking.

 

As stated above, fuel delivery issue would also be my 1st 'go-to'. And the 1st of those being remove the gas cap and take it for a spin, see what happens. How much rubber hose or braided stainless is in the system? It can delaminate inside and the loose "flap" closes off flow when demand is high. I'm going to assume you did the pump checks for not only pressure but delivery. Meaning you cranked it over into a container to measure volume for 10 seconds or so. It could indeed be something electrical/ignition related like a small short (also mentioned above) that happens when you lean on it. The main change in the whole gig is the automatic trans. Is vacuum involved in a 350? I don't remember for sure but I think so, but then again you have 16 at idle, right? Where did that come from if there's vacuum to the trans? If no vac, sorry, we can move on. It might be as simple as the additional linkage for the trans shorting a feed to the ignition when you go WFO. Not being there the best I can do is stimulate your hands-on experiences.

 

Years ago I had a similar problem I changed everything, finally I took the fuel tank out and as it was laying on the ground I removed the fuel gauge sender, once that was out I could see a small piece of plastic that was slightly larger than the fuel line and could float around and occasionally block the line. After that was removed problem solved.

 

I question the distributor changes. You said you changed out an old accel with two different plug and play models that could actually be the same with a different color cap.
I have heard many bad reports on these distributors, if you can get your hands on a good points distributor that would rule out any questions of some small electronic piece that can be hard to test.

 

Is the trans kicking down like it should? It's a simple enough system to check to see if the trans is hanging in too high a gear.

 

Ok lets start over,

Will run up to full rpm if you just ease it up to full throttle?
Will it pull full rpm in first gear?
Will it pull full rpm in 1 & 2 gear?
Will it pull full rpm on the primarys?
Does only lay over if you open the secondary?
Does it run to full rpm then lay over before the next gear?
Does just fall on its face if you floor it at low rpm?
Does it fall on its face if you floor it at higher rpm?
Does it ever pick up and run at WOT?
Does the trans downshift when you floor it?
Does it recover and pull hard if you let off and step back in to it?
Does it pop and bang out the tail pipe when it stalls?

Get back to us on these, Y/ N questions

 

Found this to fix timing issues on more than one sbc: Pull the distributor and look at the gear for wear. Just a little wear puts the rotor way off where it should be during mechanical or vacuum advance events. If the gear shows any wear replace it.

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Just for the hell of it check the vacuum line between the turbo 350 and the carb.

 

This is one of those "Wish I was THERE!" deals.
I recall a nice '40 coupe with a 283 in it, in 1958. Friend bought it from an older kid, Kent, that did the install. Car did roughly the same thing, but it was NOT a fuel problem:
Stomp throttle to floor, acted like it ran out of gas...Let up, and instant recovery.
Three times made me look under hood...Finally discovered the linkage contacted the primary coil wire on WOT, underneath where the coil was, real 'obscure', just out of eyesight.
Foot to floor, direct short to the 'points lead'! Instant shutoff, like a mag kill switch.
New primary wire, routed correctly...problem solved.
Turned out that was the reason Kent sold the car. His Dad was an M.D., 'diagnosed' the '40 as a 'Lemon'! "Can't be fixed..." LOL (LOVE that one!)

 

Had a friend who had a dead rat in his gas tank. Would pull down over inlet, car would go dead. Shut it off ,wait a few min. carry on. And this has nothing to do with your problem...........But when you do figure it out, please post it. Good luck

 

I wonder if anyone here has ever driven a car with a fuel starvation problem? It takes a little bit of time for the bowl to run dry, it doesn't happen instantly.

 

That's why I think it's ignition related

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hey, I tried to explain that 2 f'n days ago.... I guess logic means nothing

Me too..that ALSO was suggested two days ago:

 

Running out of ignition can feel like running out of fuel. Check the voltage at the distributor or coil,coil output is dependent on coil input. Also check the rotor for punch through

 

I'm there too Jim, but low/slow delivery can run the car at low load/speed conditions then be nearly dead at WFO if not toally dead. His scenario seems more appropriate to small volume carbs like he's using, whereas a Holley might take a bit longer, or run along ok until you want it all and there's not enough in the bowls to feed the need. Qjets were really good for such issues given their small float bowl capacity. Still, I favor the shorted wire gig happening in the least expected place. I too wish I was there and frankly love a challenge like this. The switch to an auto trans is a usual suspect in this one. Linkage in different spots, kickdown cable shorting something, a feed wire on the starter...

 

Hey, classicdreamer.
Some good advice, but also some suggestions not taking into account everything you told us.
At first blush, it sounds like a fuel deliver problem. But you tried what...3 carbs? And you said you checked and serviced the whole fuel system. Jim's right...(as usual)...fuel starvation doesn't happen instantly. Still...good to double check actual flow at the line at the carb...however you decide to do that. Shoot...pull the hose at the carb, put it in a clear jar or bottle so you can watch it and crank the engine for a bit. It should flow WAY more than any street-driven carb would ever use.
Or just run the engine at a relatively high rpm for a bit with the air-cleaner off. Rev it. Rev it again...let it die. Then immediately look into the top of the carb and pump the throttle. I bet you still see a strong squirt from the accelerator pumps. If so, it aint fuel. If it's just dribbling, you missed something in the fuel system.
If it was a vacuum leak, the idle would tend to hover high for a moment after revving the engine. You didn't say it does that.

For all the reasons, I too think something with the ignition.

Let me ask. Did you replace the spark-plugs before you started changing out carburetors? And ran the engine with the new plugs and first carb? The first carb was runnin way rich? And you haven't looked at the plugs again since?...because hey...they're new. If so, check 'em again. You said it ran way better with the replacement carbs than with the first one, but didn't fix the wot problem at all. Your original crappy carb may have somewhat fouled the NEW plugs too. Then you changed the carb and it stopped running lean and ran better at lower speeds...but the fouled plugs don't misfire until under a heavy load.
Good luck, let us know.

 

If the symptoms don't show when stomping the pedal while sitting in Park, it could be as others suggested...a g-force-induced ignition short. I experienced something similar. Took days to finally track down the problem. The wire going through the bottom of the base of my distributor had worn through, and was shorting intermittently. But not just on acceleration.

 

Haven't heard anybody say, check that your battery is charged too.
And run the engine while holding a spark-plug terminal close to its spark plug. Spark is hopefully blue, strong and snappy...not orange and weak.

 

when using fancy distributors I find the best way to test for ignition problems is put a known good points distributor in it. with points there are no mysteries. if it does the same thing with points then you know that is not the problem.