Help!! Engine Miss

[Monte Howard]

My first thought was the wires from the msd box to distributor, do not let them go anywhere near the coil, I know this has been suggested already. So I would look at the wiring/ switches you changed then I would throw a different carb on and see.
I have had two quadrajets over the years that went bad all of the sudden. They would not rev over 4500 rpm. Rebuilt them several times with the same results. Finally gave up and they are in the trash now. Don't assume the carb is ok, the only way to know for sure is by trying a different carb.
If a different carb doesn't work, I think I would rewire the entire car with a nice new switch panel.

[Kevin Lang]

Hey Ben! just my 2 cents but you dont have solid core sparkplug wires do you ? because i learned this one the hard way years ago before MSD posted a warning about the RF interference from them screwing up the operation of the MSD box. Good luck and hope you find it soon. Kevin

[njk53]

Originally Posted by Kevin Lang

Hey Ben! just my 2 cents but you dont have solid core sparkplug wires do you ? because i learned this one the hard way years ago before MSD posted a warning about the RF interference from them screwing up the operation of the MSD box. Good luck and hope you find it soon. Kevin

Had the same thing happen to us. Had a fresh motor right off of the dyno (ran great on the dyno) put it in the car and it picked up a miss. The cause was a leaking header gasket. Put new gaskets on..... problem gone. Just a thought.

[Arnold Greene]

Ben, have you checked fuel pump flow and your fuel filter? For an engine like yours, the pump should flow a gallon in 15 to 20 seconds to keep up with the QJet demand. Anything more than 20 seconds is suspect. The filter could be clogged inhibiting flow. If you have a return style pump, where is it plumbed back into the cell? Good luck.

[Bob Gullett]

Dumb question but was the cam changed and is a 4-7 swap?

[Ben Kallies]

Monte,

Thanks for the thoughts.

Kevin,

I'm running MSD 8.5mm plug wires. No solid core.

Arnold,

I checked the fuel filter when I drained the fuel system, and all is well. I can fill a gallon in about 23 seconds. I had previously been told that anything under 25 seconds was ok. Regardless, my problem is occuring when I'm barely tipping the throttle. I would think that even if fuel flow was insufficient for racing, I'd still be able to drive it around the block.

Bob,

Not a dumb question, and yes I did install a new 4-7 cam, and yes I've checked and rechecked the wires about 2 dozen times. I always assume the possibility that I've done something foolish.

-Ben

[Ben Kallies]

Thanks to all for your input so far.

I've already got a #10 ground strap to one head, and I'm down to bare metal at both contact points. I'll add a second ground strap to the other head, just to be safe. Please keep the experiences and thoughts coming. It gives me places to look, things to check, and God-willing, the possibility of narrowing down the problem.

-Ben

[67camaroracer]

Did anyone mention a firewall feed thru for the coil wire, ?

[goinbroke2]

Flat lobe on exh would cause popping out carb.

If it's a miss while reving in neutral I would of closed off the choke and check the result.
Also look down the throat while reving and see if it's a smooth pattern of fuel or blobs of fuel from the emulsion tubes on both sides. If it makes no difference, rev it and move the dist around(advance/retard) and listen for a difference.

I'd also close the gap on the plugs to about .030 just to test.

Another dist wired directly to batt and another carb will prove if it's external. Your saying you've switched dist and carb so next is;

Comp check and leak down

Valves are adj right.....you didn't leave the break-in valvesprings on did you???
vacuum leak, p/brake hose cracked or carb gasket etc?


And the "out there ones"
Same oil pan as the dyno? thinking oil pump sucking the pan because of lack of clearance and the resulting vibration/cavitation acting on the dist causing spark scatter.

How did you lift the engine to install it? undo an intake bolt or remove carb and use lift plate? Check those area's for warp/vac leak

[Ben Kallies]

67camaroracer,
-coil is mounted on the firewall. No feed-through. Already replaced the coil and wires.

goinbroke2,
- car starts right up and fuel flow is smooth out of the squirters. Fuel pressure gauge is rock steady.
- oil pan is the same as dyno, and oil pressure is good.
- lifted the engine in the car via a carb-plate
- break-in springs were changed on the dyno
- while I haven't hooked up a vacuum gauge yet, I've checked for leaks visually. The engine is running rich as opposed to lean, so I don't suspect a vacuum leak. The unburned fuel brings tears to my eyes when it's running, and the plugs are all over the map, but mostly dark.

-Ben