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

See post 31.

 

Sorry for the late responses jammed up at work. The car didnt start doing it over night. Feel like it has happened over time.
The ignition module in the accel distributor burned out in August and that’s when the replacement parts started. Before that the car was weak off the line never really full capacity.
Changed the coil first to an accel super stocker.
Then the distributor was changed to a a summit ready to run. Same time replaced wired with 8.5mm msd wires. Ran for a month or 2 okay, not great. Think timing was off. At wot it was off and on with pulling hard. More timing to the motor and problem got worse. Fuel pressure started going crazy. Changed the fuel pump in sept, changed carb in sept. After putting on the new carb it was giving me issues with backfiring. Brought to a shop they timed it to ?? . Pulls hard off the line and not completely falls on its face at WOT. Brought it to another shop who went through in the past 2 weeks. Retiming, bringing motor back to TDC, checking fuel line and pickup tube in tank (clear) inside tank looks relatively new. No kinks, fuel pressure seems stable at 6psi. They also swapped the carb to a Holley 650 and same issue.
Just told by them they have exhaust all tuning options and that they believe it is degreeing the cam.
If that was the case would it have been shot the entire time or could it get worse over time?

 

Just got off with edelbrock tech and they suggested the Airdoor adjustment.

Any chance the accel coil is not jiving with the msd distributor?

 

Find a shop with a oscilloscope and someone who knows how to use it.

 

any suggestions in the NYC perimeter?

 

Ck the PH.book for auto electric and tune up shops One that has been around for a long time with some real old guys working there.

 

Is the accel coil made for points or electronic ignition?

 

It's a cheap and easy thing to check. That's the reason I suggested it on the first page. You don't have to throw any money at it or swap parts to test it out and the only tools you need to grab are a couple of screwdrivers. It may not fix your problem and then you can cross it off your list for now. But you'll find out soon enough if it does or doesn't.

The air valve needs to open at a controlled rate... Like this!

 

It’s the accel super stock points ignition coil, but says it works with both points and breakerless electronic.

Called Holley and told them I have an msd dist and a accel coil and the tech was like “ um no... that’s going to cause issues.”

 

If you have a ohm meter check a crossed the 2 small terminals it should read about 2 ohms. I think a MSD coil is around .7 ohms.

 

Since the original carb was a vacuum secondary type carb, when the secondaries start to open too fast or soon, take your pick, if the rpm is too low, you have to have fuel to cover up the dead spot, ie, too much air too soon. sometimes it's at such a low RPM the engine cannot recover until you let off the throttle to stop the admission of too much air. Capish? I'm leaning towards a lean condition. Your results may vary. Weak ignition can cause the conditions you have mentioned, like backfiring ect... but so can a lean mixture. I'm with Dan Griffon. Find an older mechanic shop . Someone who doesn't just change parts but diagnosis the problem. Timing would have to be WAY off to cause what you are experiencing. Cam timing?.......eh. Lippy

 

Clay has it too I think. Lippy

 

Narrowing it down.
I like these diagnostic threads. 50 heads are better than one. And we learn stuff. And problems get solved.
How's it goin', classicdreamer?

 

Lumpy said..."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."
I have run into this before....rust/dirt plugged vent pipe on a 60s chevelle. The diagnosis is super cheap...free! Remove both the gas cap and the air cleaner and drive it. If it's better, you're on to something. If not, you've just eliminated 2 possible problems and didn't cost you a cent.

 

HEI likes to have coils with .5 to .7 Ohms primary resistance and a good ground on the distributor You would not want an inline resistor wire or ballast resistor either. Could be a combination of things and not just one thing with all the new parts introduced.

 

I still believe it's weak ignition

Sent from my SM-G965U using The H.A.M.B. mobile app

 

I picked up the car today. Pulled much better than before, but still chokes on a quick WOT. This weekend going to swap over the msd coil. Adjust the kickdown cable and a couple other things.

 

90 % of carburettor/fuel "problems" are actually ignition problems. Does your engine/chassis/battery have a good ground and another good ground wire to the distributor body from the block. I have seen cars which had the engine grounding through the linkage/cable to the carburettor, because the proper ground had freyed or broken or even just came loose at one end. Grounding through engine mounts or loose wires will change as the motor torques, low voltage will stop electronics including HEI in it's tracks, and will burn out modules.

 

So is this at any speed? Is it the same from a 'fresh run' as in it had a chance to idle a while and off you go? Is it after you rolled along a 1/4-1/2 mile then gets this mega flat spot? I'm gonna throw something in the mix here. Can you look at your gauges in this condition and see any change in the volt meter/amp meter? That would indicate a short and at least add focus to your search. There's been a lot of keyboard diagnostics here so far but I'd rather give you a nudge based upon your hands-on with it. So that said, manual or electric choke? If it's manual give it a tug when it happens and see if it wakes up. Assuming it does you're closer to a fuel issue to solve. If it does nothing or indeed gets worse you have a fuel dump issue, as in too much on WFO, and that would lead you toward getting the secondary action sorted. Still, I'd try to cast an eye on your volt meter and see if it drops a bit, or indeed perks up a bit. Drop would be a low voltage short, perking up would be cutting out voltage. Amp or volt, if there's a decent interference going on it might show. If this looks like a I dig a challenge like this, well you're right, I do. Plus we have "sister" cars so there's that...

 

So.... Have you tried putting another quarter or half a turn of pre-load into the secondary air valve adjustment yet?

 

Sounds like Dist vacuum advance is not working, check the points plate for movement and the wires under it too.

 

Throw a timing light on it. Check mechanical advance. Vacuum advance normally doesn't effect performance, but effects economy. Make sure you are getting proper amount of advance. Might want to pull that new dizzy out and slip in a hei unit from the boneyard. Or a known functioning unit .

 

Ck Balast Resistor, HEI don't use one, points dist need a balast resistor also coils are different for hei and points dist.
Got to configure for one or the other points balast resistor and std coil with no built in balast resistor or hei no blast resistor and hei coil with built in resistor.

 

I had a new Accel coil that made my Blazer act like it was running out of gas. When it was cool it worked fine when it was warm under a load it sputtered and quit. I really thought it was a fuel problem.

 

Have you followed up on Ticketyboo's easily done suggestion (post #41)? I had symptoms exactly like yours on a Chevy 6 with HEI. After checking the fuel pump, checking the accelerator pump, cleaning the carburetor superficially on the car, cleaning the carb thoroughly on the kitchen table, I disconnected and plugged the vacuum advance, and "Eureka"! The wire to the ignition sensor had broken inside its insulation after a 100,000 rotations of its mounting plate. The broken ends were normally held in contact by the insulation, but hinged apart when the vacuum advance deployed. I guess if you've tried different distributors, this cause becomes less plausible.

 

90% of carburetor issues are electrical in nature

There's been all the questions asked for a great internet trouble shoot session
Haven't seen much answers
There's certain ways I'd road test it and then evaluate those results.
The ways have already been explained and results asked for.
How are you making out

 

My two cents......I had one that did pretty much the same thing and it was the battery about to go dead. At higher RPM it couldn't "keep up" with the MSD box.
I agree with the poster explaining it CAN'T be running out of gas when just prior to the full-throttle-stomp it was fine. Also the statement about most carb problems are ignition problems instead is true. We ALL wanna blame the CARB when the engine goes sour!...Poor carb
6sally6

 

It seams everything I thought of was already mentioned except one, a partially plugged exhaust, disconnect your muffler and see what happens.

 

bump
Hopeful for an update.

 

Sorry guys for not updating NY weather has kept me out of the non heated garage.