Flathead Help

I've worked on a few flatheads and various small blocks and haven't been stumped yet, until last night.

My stock 49 flathead started cutting out at rpms above 2500 and power just immediately falls off with no chance in continuint to gain rpm.

i've checked all the normal stuff and every thing checks out, until i start removing plug wires one at a time. It makes no difference when i remove plug wires 6-8. However, i know i have spark at the plug and i have fairly equal compression at each cylinder (1-8). If i remove any other spark plug wire, it is instantly noticable. What gives?

 

maybe your wires are bad and arcing on something. Good wires work wonders

 

i've replaced wires, i've had it running in the dark so i could find arc outs, there isn't any. Is it possible the intake runners to 6-8 are blocked?

 

is ur advance in ur dist. stuck?

 

Just wondering...you replaced the plug wires, were they replaced befor or after the problem? have you replaced or added anything else since it was running at full power? what type of distributor electronic or stock?

 

Are you using the correct firing order?
Do you know the cylinder numbering on a flathead?

 

check your wires also look for carbon tracking in the dizzy cap. maybe look at the relucter wheel in the dizzy

 

firing order is correct, cap looks good, stock distributor, advance is working - getting about 14 degrees advance from idle to point where it cuts out. car was running good, went for drive, came to an intersection, then when i pulled away is when it started. i've replaced points, condensor, swapped distributor with another motor, swapped carbs, swapped plugs, swapped plug wires. i'm out of ideas without pulling the head and intake.
if i remove the plugs 6-8 and ground them out, they spark. however when they are in the motor, it doesn't run any different with the wires connected or not.

 

Have you tried another coil? Is the coil getting hot?

 

forgot to mention that, i tried a different coil too

 

after digging deeper, 6-8 don't pull any vacuum, they only blow

 

Time to pull the heads off. Sounds valve related and possibly lost a valve seat insert.

 

I don't understand this! You mean that, with the plugs out, on the intake stroke, you can not feel a va***n at the plug hole? but, that on the compression stroke they blow out the plug hole?

what is the compression shown on those two plugs with the compression meter?

One: if you have compression and not firing it is an ignition problem caused by lack of ignition or lack of fuel.

Two, you can tell the difference by smell if you put your thumb over the hole and smell the compressed air coming out on compression stroke.

Three. You say it isn't the plugs , wires , or other stuff.

Four. You say it is at 2500 that the problem starts! Ergo, it is not the fuel, and must be ignition.

Five. You say you have changed points , ignition capacitor, wires , etc.

Now we switch back to fuel, Check your fuel filter, fuel level, and fuel pressure.

Six, as it happened after you were driving it, and it came on suddenly, it again reverts to bad fuel, pressure, check your fuel pump

that is the best I can do!

traderjack

 

Check your gas tank or pick up tube. It could be some **** blocking the fuel inlet which would cause it to starve for fuel at higher RPM's. Also the **** could move out or away from the pick up tube after you let it sit causing it to run fine when you first start it the next time. Then after you have been driving and stppping the **** in the tank is now all mixed up and finds its way back over or in the suction tube causing it to run like **** when you try to leave a stop light.

Fuel starvation is often mistaken for an ignition problem. Check it out!