Extreme pre ignition runs like crap!

T

Thomas C Potter

Senior Member
My 68 LTD has been running great for 10 years / 30k miles on rebuilt FE engine, stock, nothing fancy. Very consistent Barry Grant 650 carb, Pertronix ignition.

On same full tank of gas, ran great for the first 5/8, and within 20 miles slowly developed extreme pre ignition, low power. I almost had it towed home.

First was to check timing, right were it has been, 8 deg static, 34 full.
All spark plugs look good, I was hoping to see some crud lodged in 2 or 3 plugs, but none.

I am in process of drawing old gas and put in fresh. I always use name brand gas, no 7/11 or shettz crap.

Thoughts??
 
Bad gas, fuel filter.

See if the carb has a small fuel filter right at the inlet, where the gas line attaches.

Then check to see if the fuel pump diaphragm is good or bad
 
+1
Sounds like a lean condition. I'm doubting it's a vacuum leak, but not impossible. Could be a sticky float or some gunk in a jet. I clean lots of ethanol crud out of carburetors these days.
 
I think your looking at right things. I however ran into bunch of trouble with Petronix (won't ever use it again). Just check that its working well. I have FE's as well and I run 12-14 of initial timing, especially with hotter ignition. That's with pump gas as well. Check for good grounds for your ignition too.
 
All indications are a head gasket leak between 3 & 4.

So, if someone wants to buy a rust free (came from California) 4 door Brougham in the next 48 hours, it is available. I do not want to sell, but we are in midst of getting house on the market, retiring, moving somewhat south. My 06 Mustang GT conv is advertised, it makes sense to sell one of my cars to free up garage space (storage space) vs the $4000 min it will cost to do the pod thing.

Why 48 hours, I plan to take Tuesday off and take the heads off on this LTD.

$5000

TP 703 620-2243 call after 8:15am, or before 9PM


how do I put a picture right here??
 

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ThinkI see the problem, those no-need to retorque head gaskets!!
Loosening the ARP nuts on the passenger head, some were not that tight. So much for no re-torque required!! #$&$#@(“!!

What is the experience on the more modern torque-to-yield head bolts??
 
My saga continues.. Had heads surfaced while they were off, CJ valves installed, little porting. It was trying to run, distributor was one tooth off, now it will not run but get very loud backfire out of exhaust pipes. Poor cat!!

!!!@#$$%%^ Thoughts??
 
Tdc #1 on exhaust stroke, pull the plug and verify piston comes up all the way with your finger over the spark plug hole...
Then check the piston with a coat hanger and make sure the piston is rising up all the way, once up all the way, check balancer to timing mark, you should be dead nuts on 0 of the timing mark on the timing cover.

Now point the rotor toward #1 spark plug

Check the voltage to the points, it should have a resistor to about 8 volts,
If upgraded ignition it needs 12 volts

You can and should check compression just to verify all valves are opening and no bent pushrods.

Make sure your plug wires have low resistance, and are in the correct firing order
 
Thomas C Potter said:
My saga continues.. Had heads surfaced while they were off, CJ valves installed, little porting. It was trying to run, distributor was one tooth off, now it will not run but get very loud backfire out of exhaust pipes. Poor cat!!

!!!@#$$%%^ Thoughts??
Click to expand...


Sounds like firing order mix up, dist off or timing WAY off...


Good luck!
 
I can't add to these comments other than to say it sounds like a distributor/timing issue to me.

How did you determine it was a tooth off?
Similar process to get it timed
 
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