I have no idea what all was done to my 340 before I got it.
I do know it has a Torker 340 intake, Carter AFB 4b carb, electronic ignition, electric fuel pump and fuel regulator and a electronic rev limiter.

I had the timing set to factory spec of 5* before and get this awful hesitation, most of the time it just dies when I mash the pedal down from a dead stop.

I advanced the base timing to 10* before and it does take off better, still not a lot of power but it does not stall out.

Okay my question, given the fact somebody dropped a lot of extra money into the motor I wondering if they may have done something to the cam.
I don't know what a 'over sized' cam does for you, but if this was the case is it possible that I need to advance the timing even more?
I am afraid to 'just do it' as I have read warnings against advancing to far.

Thank you for any help.
Joe.

 

im not sure what your calling an oversized cam? but too much duration will cause poor low end. you can play with the dist a bit. time it by ear. what you wanna watch out for is detenation. when it pings back it off. you can also use offset cam "keys"to acheive better aceleration by retarding the cam

 

"im not sure what your calling an oversized cam?"

Me either, it just something I have seen people chatting about or heard them talk about. I'm just grabbing for straws....

We have a new distributor - cap and rotor. Just installed one of those 1" spacers between the carb and the intake as I was told that would help, nope. New ignition coil ..... I don't know I'm at my wits end


What do you mean by "to much duration" ?

 

i really cant see a carb spacer helping that.. that usually just takes away botten power and gives more high end power. cam duration is how long the valves stay open.. circle has a duration of 360 degress. for a streat bound small block 280 deg duration for an automatic, manual 292 deg duration. but you dont know what you have. and the only way to find out is take the intake off and measure it with a cam degreeing kit/ cam checking fixture. they run about 80~100 bucks that will tell you lift/duration and centerline.

 

thats the 1st i have heard of a oversized cam.. i have heard full race. 3/4 race. and i have no idea what that means? they probly dont either. i hear ppl talk about rv cams. and all that is to me is a low lift short duration cam for 4x4's and rvs. ..

 

An over sized cam usually means that the lift/duration numbers are too high (big) for the application. A "bigger" cam will most often start making power at higher rpm's and a "smaller" cam will have more throttle response and low end performance (RV cam). Having said all that I think your problem is more likely carburetion. Too big of a carb or an incorrect accelerator pump. Borrow someone else's smaller carb and see if that doesn't make a HUGE difference.

 

To big of carb? That brings to mind what one of the guys said about an exhaust restriction. The motor has stock exhaust manifolds. So it very well could be that while there is no exhaust restriction in normal conditions, with the after market intake and the large 4b carb the exhaust could be acting as if it were restricted.... Make any sense?

Being that it's in the Dakota I don't believe there is room for headers. Even the block huggers make me worry about space. So opening up the exhaust is kinda out of the question.

I sure appreciate you guys help here, with your help I think we can crack this nut and when we do, that little truck is going to scream!

Joe.

 

Oh for the love of Pete!
You ever know a guy that if there is two ways of doing something he always does the wrong way first? Well if you did not before now you do

The carb spacer kit I bought came with two inserts, one with 4 holes matching the carb barrels and one that is open whole [more or less matches the intake manifold].

Well reading here I find of coarse I've used the open whole insert and took the carb in completely the wrong direction......

Well someday my son will appreciate the fact that I shown him a whole lot about how not to do things

Joe.

 

i dont know if this will help but the carb on my 340 is a holley 750 dual feed when i would give it a tromp she would bog down not die but acted like she was gasping took tha carb apart and they had huge jets in it sending to much gas in and choking my motor replaced the jets with smaller ones and she runs like a raped ape hope this will help

 

Now that would make sense too, because the motor is surely getting gas and a lot of it! Was it the primary, secondary or possibly both pairs of jets you replaced?

Joe.

 

Carb spacers will effect certain RPM ranges depending on design. 4-hole spacers are designed for low to mid range power and better throttle. Open spacers are better for high RPM.

What size carb do you have on there now? How does it run at higher (4000+) RPMs?

 

The carb is a Carter AFB 9606 (605 cfm) on a Edelbrock Torker 340 intake.
No tach so I can only say it does run decent at highway speeds and idels fantastic, just croaks when you mash the pedal down.

Thank you
Joe.

 

replaced both but i cant remember what size i put in sorry

 

picking the right cfm carb.

(c.i.d)340x max rpm. (lets say) 6000: 340X6000=2040000/3456 (divide by) = 590.27 cfm that cfm number is at 100% efficiency.. like a drag car. so streat car would be about 80% so your cfm would be 472. (carb size)
did i lose you?
also you can buy strip kits for those carters they come with alot of needles and jets so you can find the perfect combo

 

Dang 1966! Sweet formula! I did it for my 440 with 6000 rpm and it came out 763...80% of that would be 611, so should I be using a 650 instead of the 750???

 

you rounded up good!! for street use yes i would.

 

Yeah, rounding up is just one of my many talents I can round up reel good!

 

I think we need to get back to basics here. Does the truck idle? How well does it idle? Does it idle rich? Do the idle mixture screws work, or is there no change while adjusting them? Do you have to have the carb cranked way past idle, to get it to idle? What is your vacuum at at idle, is it low? These are the symptoms of an "over-cammed" motor, or vacuum leak.

 

The engine idles great and comes up to driving speed just fine with a moderate acceleration.
Mixtures screws work and are adjusted at 2 turns out.
Idle screw is turned 3/4 of a turn past were it first touches the linkage.
No vacuum gauge but seems to have a lot of vacuum.
Verified all vacuum hoses no leaks.

One thing that does bug me about the vacuum is the PCV valve vibrates, at times it's a loud enough buzz you can hear it inside the truck. It did this with the valve that was on there when I bought the truck so I replaced it and it still does the same thing. Not always, mostly when the engine is warming up.

I think I will spend another $26 dollars on some smaller jets for the carb and if that don't do it I'm going to give in and take it to a shop. I just absolutely hate the idea of that because for me the whole point is to do it yourself, but I'm about licked here I think.

I sure appreciate everyone's help and suggestions.
Joe.

 

Then your cam is not oversized.

 

Thanks Scott,

When this nut is cracked I'm sure to let ya all know what it was

 

Play with a vacuum gauge!

 

good luck on replacing the jets i hope it solves your problem let me if that was the problem

 

Set your initial at 12* btdc, using a dial back timing light set advance at 36-38 at 3000 rpm's and see if that helps. If your total timing exceeds 38 take a 3/32 allen wrench and insert it through the nipple on the vacuum advance can and see if you can adjust it. If your can is adjustable. Counterclockwise to retard, clockwise to advance.

 

I pulled the Primary Jets out tonight and will be taking them to Auto Zone in the city tomorrow. I could not find a magnifying glass to see the #'s so I took pictures. I can see them now, but have no idea if they will be useful?
These and the secondary jets appear to be the same size, I have no idea if they need to be the same size? I'm planning on just replacing the Primaries unless I hear something different you fella's. The plan is to replace them with something smaller.

 

HOLY MOLEY.... 120's? sheeze yeah i would say that those a lil on the large size.....