1966 Chrysler 300 engine surge

[Bryon Mason]

I have a engine surge that's going to be the absolute death of me. Engine is 383 with slight upgrades. 512 heads with hardened seats and bowled, comp cam k kit for Chrysler, Edelbrock AVS 2 650 , 1 inch aluminum carb spacer. Electronic ignition conversion, NGK plugs and Taylor 8mm wires. I've upgraded the fuel pump, still mechanical. Carbs getting 5.5 psi. Problem just developed and I can't seem to trace it out. Any suggestions would be greatly appreciated.

 

[halifaxhops]

UHM more info when and what exactly is it doing?

 

[Bryon Mason]

Surges at idle, surges when maintaining a constant speed, really bad surge with WOT. At idle about every 6 seconds car surges , WOT its a constant in and out surge. Steady speed you can feel the car stumble like its missing. However its not constant at steady speed.

 

[halifaxhops]

I would look for vaccuum leaks first. Then go from there. Al the vacuum, brake booster, bad pcv valve etc. If nothing move on to fuel make sure it is not flooding out the bowl, does not really sound like ignition yet from what you mentioned.

 

[CBODY67]

What is the engine oil level? Have you put a timing light on it while it is surging? Will it surge not-under-load (i.e., in "P") and also in "D" with the foot brake firmly applied (at lower rpms)?

After I got my '70 Monaco 383 "N" back in 1975, it had a surge right before it would shift 1-2 at WOT. I checked everything. Float level, timing, ignition (still points) and all was at specs. I had read about B/RB engines sometimes having a higher-rpm surge due to uneven loading of the oil pumo, which is at the base of the distributor shaft/drive. As the pump loading changed, it changed the amount of torsion on the distributor shaft, which resulted in timing changing several degrees as that happened. I changed to Castrol GTX 10W-40 and it went away, magically, and stayed away.

In more recent times, my modern car started to surge a bit. I checked the oil, which was not low enough to turn on the "Add Oil Message", but was a small bit below "ADD". I put 1/2 quart of oil in it and it ran smooth again. Do need to get it changed, soon, though, by the OLM mileage.

My experiences, not sure if they might help you or not.

CBODY67

 

[57fury440]

It was converted to electronic ignition. Is the distributor new? Maybe the vacuum advance is acting funny or there is a problem with the advance plate.

 

[Big_John]

Surge often means a lean condition.

Look at the plugs and see if it's running lean.

Watch a YouTube video on reading plugs (there's a bunch) if you don't know how to "read" a spark plug.

 

[Bryon Mason]

It appears it was the carburetor base gasket under my 1 inch spacer. Now if I can only figure out why it's such a dog in first gear. Top end runs great, off the line she doesn't want to get moving.

 

[stubs300]

Delete the carb spacer and see how it behaves! Good Luck

 

[Bryon Mason]

Honestly thinking of just going with a different intake. That old cast iron gets so damn hot. The spacer actually helped with the heat soak.

 

[mr gtx]

Honestly thinking of just going with a different intake. That old cast iron gets so damn hot. The spacer actually helped with the heat soak.

is it an open spacer

 

[Bryon Mason]

is it an open spacer

 

[CBODY67]

You've already got a dual-plane intake, which is good for lower to mid-rpm torque. NO aftermarket intake is magically going to increase off-idle torque by 30lbs-ft or so. What cam in the engine? What heads? Ignition and carb? What engine and rear axle ratio? Will it even lay a bit of rubber on quick take-offs? On dirt? Mileage on the engine?

NOW, if you want it to keep up with the 4cyl little cars with their gazillion-speed automatics, then graft a ZF TF 8-speed onto the back of your engine. Instant 4.9 low gear compared to your existing 2.45 low gear . . . not counting the toreque converter ratio. "Improved launch", as the factory people note.

The other thing is that no WOT right off of idle. 1/2 throttle punch should get things going better, from my experiences. Then more throttle about 40% through low gear.

Just some thoughts,
CBODY67

 

[Bryon Mason]

You've already got a dual-plane intake, which is good for lower to mid-rpm torque. NO aftermarket intake is magically going to increase off-idle torque by 30lbs-ft or so. What cam in the engine? What heads? Ignition and carb? What engine and rear axle ratio? Will it even lay a bit of rubber on quick take-offs? On dirt? Mileage on the engine?

NOW, if you want it to keep up with the 4cyl little cars with their gazillion-speed automatics, then graft a ZF TF 8-speed onto the back of your engine. Instant 4.9 low gear compared to your existing 2.45 low gear . . . not counting the toreque converter ratio. "Improved launch", as the factory people note.

The other thing is that no WOT right off of idle. 1/2 throttle punch should get things going better, from my experiences. Then more throttle about 40% through low gear.

Just some thoughts,
CBODY67

Engine specs on the original post, engine maybe has 800 miles on it since rebuild. 727 trans with 3.23 rear end. Im not building a race car but at the same time it shouldn't be a pig off the line.

 

[CBODY67]

Not to sound flaky, but "pig" in comparison to what? What is the standard of comparison? Below what road speed?

Respectfully,
CBODY67