66' 300 383 rebuild

[Bryon Mason]

I just put the engine back in my car after a rebuild, very few mods
Extreme energy cam
Hardened seats
Blended bowls
Electronic ignition
The problem im having is that the kickdown doesn't seem to be working properly. When I test drove it the engine runs good, but when I get into the throttle rhe accelerates, but doesn't feel like the 4 barrel is really opening up. Its the stock carter carb and original intake. Any suggestions on what I should try before I just buy a new carb?

 

[Imperialist67]

Nice progress - I'm not qualified to advise you here, but I wouldn't give up the Carter until all other options have been gone through.... good luck.

 

[Ross Wooldridge]

There is a specific linkage setup procedure that is outlined in the FSM. You also need to check that the throttle cable is properly adjusted to fully open the carb when the pedal is fully depressed - get a buddy to help.

 

[Bryon Mason]

There is a specific linkage setup procedure that is outlined in the FSM. You also need to check that the throttle cable is properly adjusted to fully open the carb when the pedal is fully depressed - get a buddy to help.

The pedal does feel soft, meaning when I put it to the floor in my head I feel there should be more pedal left.

 

[Ross Wooldridge]

The factory carb is an excellent choice for that motor, so do your due diligence in making sure the stuff attached to it is all set up properly. Good luck!

 

[LocuMob]

Adjust the throttle linkage. I pull it back tight to make sure the secondaries are opening, tighten and check the pedal inside the car. Adjust if the pedal stays down too far. Then I adjust the kickdown as per the FSM as @Ross Wooldridge described. Having a buddy helps, but it's simple to do by yourself.

It feels like the secondaries aren't opening when the trans isn't getting the proper pressure, doggish.

 

[mopar440]

Yeah, check carb is fully opening, also, that year did not have partial throttle kick down, only should downshift at full throttle

 

[mopar440]

Also, look at vacuum. New cam may affect, and if it's AFB, it has vacuum primary metering rods

 

[Bryon Mason]

Yeah, check carb is fully opening, also, that year did not have partial throttle kick down, only should downshift at full throttle

On the test drive I put it to the floor, I got acceleration but not at the rate it should have been by giving it full throttle.

 

[WissaMan]

I don't know much about the AFB to know if it's possible, but maybe you could disconnect the secondaries altogether and test it, then reconnect and compare. Or do something to the linkage to keep them shut

Keep in mind, they say that when a carb is adjusted properly, you won't feel the secondaries "kicking in", it'll just be a smooth power band. Though in my case I like to be able to feel it a little just for the reassuring feedback.

 

[Ripinator]

I just put the engine back in my car after a rebuild, very few mods
Extreme energy cam
Hardened seats
Blended bowls
Electronic ignition
The problem im having is that the kickdown doesn't seem to be working properly. When I test drove it the engine runs good, but when I get into the throttle rhe accelerates, but doesn't feel like the 4 barrel is really opening up. Its the stock carter carb and original intake. Any suggestions on what I should try before I just buy a new carb?View attachment 432380

You don't need a new carb - a rebuild maybe, but not a new one. Get out the FSM and make sure all the linkages and the kick-down are correctly adjusted. Get out yer timing light light and vacuum gauge and make sure everything is at spec. Your engine should run really great, when everything is set up and tuned right.

 

[CBODY67]

It could well be that you need to quicken the advance curve in the distributor. Mopar Perf used to sell a pair of springs for that purpose.

When I put a [email protected]" cam in my 305 Camaro, then took it for its initial drive, it did feel underwhelming to me. Had to fiddle with the dist springs (used OEM springs rather than the popular aftermarket spring kit) and base timing a bit to get it to where it felt and acted better than it used to. Possibly, your expectations of greatly-increased power might be a little too optimistic?

I later determined that a part of what I wasn't feeling was due to the 110 degree lobe separtion rather than something closer to the 114 degree stock situation. Which also affected idle mixture adjustments on the OEM replacement Holley 4160 I upgraded to from the stock 2bbl.

Do make sure the throttle cable is moving the carb to WOT when the accel pedal is floored. If using the same carb and intake as before, putting the kickdown rod to the previous adjustment should be fine, I suspect. But all of that depends upon the accel pedal moving the carb to WOT.

Which ExtremeEnergy cam did you use?

Just some thoughts,
CBODY67

 

[Big_John]

This is just tossing something out that I've experienced a few times now.

The secondaries won't open on 4bbl carbs despite the owners having all sorts of "expert" advice. Turned out that the choke wasn't opening all the way and the linkage was blocked (as it should be) by the choke not being fully open. It doesn't take much and apparently it gets overlooked. If you've just hooked the carb back up, the choke linkage might not be right, or if you've blocked the crossover, it might not be adjusted quite right.

Not saying that's the problem, just spit balling a possible cause based on something I've seen overlooked by some guys that I thought knew better.

 

[Bryon Mason]

Thanks for all the tips, took a quick peek at it last night and it seems the throttle "bottoms out" before it opens up. I could push it back by hand but im fairly certain there wasn't any pedal left. Going to make some adjustment this weekend and hopefully that helps.

 

[Bryon Mason]

Well I made all the adjustments, 4 barrel now opens, kicks down, and it just falls flat on its face like its starving for fuel. I can see the fuel pumping into the front 2 barrels when im manually adjusting it. Just at a total loss other than its a 55 year old carb that's probably never been rebuilt. With that said, whats a good replacement and should I keep it between 600 to 650 cfm?

 

[LocuMob]

Did you check the timing and vacuum as mentioned?

 

[Bryon Mason]

Did you check the timing and vacuum as mentioned?

I did. Nothing helped. Even had one of those overpriced fancy snap on timing lights.

 

[CBODY67]

Fuel pump push rod length? Replaced the rubber fuel line sections from the tank forward?

The OEM-style fuel pump is very efficient at lower rpms, but allegedly becomes less so at higher rpms. A shorter total stroke due to the worn push rod can possibly make it look "good" at lower rpms, but less so at higher rpms?

What road speed are you doing the WOT-kickdown at? What happens when doing kickdown at 65mph? Or if you do a progressive throttle increase without getting into kickdown? If those "progressive applicatiion short of WOT" happen reasonably well, then the metering rods in the carb are still moving up and down. A slightly-flat response (after any accel pump shot is consumed) would mean the carb mixture needs some more enrichment (primary jets/rods), but there should not be any backfires or similar.

On my '67 Newport 383 4bbl, the OEM AFB is a full manual-secondary carb. NO air valve in the secondary side, but from my experiencies, the total size of the carb is not too great to not tolerate WOT from idle (with the stock 3.23/H78-14 factory tire size equivalent). When I dressed-down the casting flash on the venturis and finessed the gasket matches between the carb sections, then I to exercise a little bit more discretion and use a slightly higher rpm (than base idle) for WOT applications. With the factory cam.

Get a quality carb kit for the carb. With the carb off of the engine, remove the carb's top casting, which should expose both of the float bowls. The secondary jets are the ones at the back of the respective float bowl areas. With proper safety shielding of your eyes and such, carefully apply some spray carb cleaner to the jets (with the straw on the aerosol carb cleaner's nozzle) to see if fuel comes to the secondary venturis, on each respective side. The fuel feed circuits should be shown in the Chrylser service manual.

With the modern AFB/AVS (or post '67 OEM 4bbl), youi'll need a new air cleaner base plate with the larger "Holley-size" (for back then) hole in it.

Before the engine rebuild, was this performance issue operative?

Just curious,
CBODY67

 

[mopar440]

Definitely rebuild it or at least, remove top, check jets and secondary venturi like stated above

 

[Bryon Mason]

Fuel pump push rod length? Replaced the rubber fuel line sections from the tank forward?

The OEM-style fuel pump is very efficient at lower rpms, but allegedly becomes less so at higher rpms. A shorter total stroke due to the worn push rod can possibly make it look "good" at lower rpms, but less so at higher rpms?

What road speed are you doing the WOT-kickdown at? What happens when doing kickdown at 65mph? Or if you do a progressive throttle increase without getting into kickdown? If those "progressive applicatiion short of WOT" happen reasonably well, then the metering rods in the carb are still moving up and down. A slightly-flat response (after any accel pump shot is consumed) would mean the carb mixture needs some more enrichment (primary jets/rods), but there should not be any backfires or similar.

On my '67 Newport 383 4bbl, the OEM AFB is a full manual-secondary carb. NO air valve in the secondary side, but from my experiencies, the total size of the carb is not too great to not tolerate WOT from idle (with the stock 3.23/H78-14 factory tire size equivalent). When I dressed-down the casting flash on the venturis and finessed the gasket matches between the carb sections, then I to exercise a little bit more discretion and use a slightly higher rpm (than base idle) for WOT applications. With the factory cam.

Get a quality carb kit for the carb. With the carb off of the engine, remove the carb's top casting, which should expose both of the float bowls. The secondary jets are the ones at the back of the respective float bowl areas. With proper safety shielding of your eyes and such, carefully apply some spray carb cleaner to the jets (with the straw on the aerosol carb cleaner's nozzle) to see if fuel comes to the secondary venturis, on each respective side. The fuel feed circuits should be shown in the Chrylser service manual.

With the modern AFB/AVS (or post '67 OEM 4bbl), youi'll need a new air cleaner base plate with the larger "Holley-size" (for back then) hole in it.

Before the engine rebuild, was this performance issue operative?

Just curious,
CBODY67

Thats my problem, when I bought the car the engine turned over and ran but the car was not drivable. Violently shaking. So I knew it needed a rebuild, unfortunately i was unable to test anything else out. Anything over an idle RPM and the entire car shook Violently. The car runs now, ive had it up to about 50 mph when I give it the full pedal and it stumbles and falls on its face. I'm ordering all new electrical components for the engine as well since there is a rats nest of wires that need to be addressed. I knew i was inheriting a problem with the engine, just didn't know it would be this bad, but I love these big old cars and jumped at the chance when I found a 66 for sale near me I could trailer home.