WOT issue 2bbl 318

[Sportfury70]

Okay so I’m at my wits end here. I have a 1970 satellite with a 2bbl 318/904 and 8.25 2.73 rear.

Engine is original and I don’t think it’s been apart. I have this issue where when I give anything more that 3/4 throttle it bogs and shakes losing power. Here’s what I’ve done:

Ignition: new dizzy with correct points clearance, new coil, new ballast resistor, new rc12yc plugs (replaced autolites, looked good but #8 was cracked) Timing set at 9 initial and 34 all in. Idles seems best there.

I have all the idle vacuum in the world.

New fuel pump

Holley 2280 with a fresh rebuild. It was “professionally rebuilt” by a shop before i bought it a few months ago. I rebuilt it again and it was clean as a whistle, but some of the clearances were off. I reset the accelerator pump stroke, high idle choke clearance, bowl vent, and fuel float all to 1970 318 mopar specs.

Air bleeds are 1.5 turns out, changing that doesn’t make much of a difference in rpm.

Curb idle is about 650-675 depending on temp.

Yesterday after doing all this, it ran great and the WOT bog was gone. Today it’s back like the problem never left.

Any ideas guys?

 

[turbine68rt]

That carb looks like it was oe for late '70's. You can get a new Carter BBD inexpensively that would be closer to what your car came with new. Bought a couple of those for customers with good results for less than $100.

 

[1967coronet]

Is there anyway the choke blade is being drawn closed when accelerating ?
Also with doing a points swap double check things with a dwell meter if you can barrow one.
Dwell should be around 28 to 32.

 

[Sportfury70]

Yeah I’m not sure where the carb came from, but it’s not the later solenoid version. The choke does not close on WOT, I made sure of that after the rebuild. I do agree that it looks like ignition is still suspect, have to look for a dwell meter.

I’m eventually swapping a magnum 5.9, and plan to do an electric ignition conversion.

I’ve been thinking to keep an eye out for a used edelbrock 4bbl intake. I have a Holley 670 avenger I can throw on from an old SBC build.

 

[davek]

Is there a pic posted because I dont see a carb?

 

[493 Mike]

Did you actually test the fuel pump? Possibly the tank sock is plugged.
Mike

 

[PRND21]

I had a 318 Poly engine do the same thing many years ago, turned out the vacuum advance diaphragm had a hole in it. I replaced the diaphragm and ran fine after that.

 

[Bird 426]

Bogs are usually fuel, too much air. I had to richen the stock Carter 2-barrel on my 318.

 

[dvw]

I see no mention of plug wire replacement. My bet is under load a wire is allowing spark to go to ground.
Doug

 

[tonysrt]

You may have a cam problem, they were using plastic gears to save money and screw customers. I had a 318 with a new timing chain, but had many bent push rods that was having a problem at full throttle backfiring. Start by pulling a plug wire at a time and see what response you get.

 

[Geoff 2]

OK. You go to 3/4 WOT & it shakes, loses power.
[1] What happens if you go to 1/2 WOT?
[2] Is the engine perfectly smooth at all times except at 3/4 WOT?

 

[Kern Dog]

You may have a cam problem, they were using plastic gears to save money and screw customers.

That wasn't the reason for the plastic gears, stop playing the victim.
The decision to use plastic lined sprockets (They aren't gears....gears mesh with other gears, sprockets are driven by chains)...was to reduce engine noise.
Plastic made the sprockets more expensive to produce than all steel.

 

[tonysrt]

I found it hard to believe they would use anything more expensive to make to install. Just look at the long list of recalls and it was usually to save money some where and would come back and bite them in the ***. I also find it hard to believe that a plastic part is more expensive than a metal gear. Maybe it was the weight loss between metal and plastic on the front end that gave better gas economy also.
When we rebuild an engine does anybody put plastic gears with their timing chains? I guess they can't afford the plastic gears.

 

[tonysrt]

I looked on Rockauto and the silent timing chain with the plastic gears is cheaper than with metal gears

 

[Sportfury70]

Is there a pic posted because I dont see a carb?

 

[Sportfury70]

Did you actually test the fuel pump? Possibly the tank sock is plugged.
Mike

I did not, but I can throw a gauge on it for pressure.

My first thought was fuel starvation from a low float. The float was a bit low, so I fixed that. I guess I can flow test it too with a pint jug and timer.

 

[Sportfury70]

You may have a cam problem, they were using plastic gears to save money and screw customers. I had a 318 with a new timing chain, but had many bent push rods that was having a problem at full throttle backfiring. Start by pulling a plug wire at a time and see what response you get.

The timing doesn’t jump around like the chain is loose or anything, but I’m wondering about it nonetheless.

 

[Rebelrouser]

Okay so I’m at my wits end here. I have a 1970 satellite with a 2bbl 318/904 and 8.25 2.73 rear.

Engine is original and I don’t think it’s been apart. I have this issue where when I give anything more that 3/4 throttle it bogs and shakes losing power. Here’s what I’ve done:

Ignition: new dizzy with correct points clearance, new coil, new ballast resistor, new rc12yc plugs (replaced autolites, looked good but #8 was cracked) Timing set at 9 initial and 34 all in. Idles seems best there.

I have all the idle vacuum in the world.

New fuel pump

Holley 2280 with a fresh rebuild. It was “professionally rebuilt” by a shop before i bought it a few months ago. I rebuilt it again and it was clean as a whistle, but some of the clearances were off. I reset the accelerator pump stroke, high idle choke clearance, bowl vent, and fuel float all to 1970 318 mopar specs.

Air bleeds are 1.5 turns out, changing that doesn’t make much of a difference in rpm.

Curb idle is about 650-675 depending on temp.

Yesterday after doing all this, it ran great and the WOT bog was gone. Today it’s back like the problem never left.

Any ideas guys?

Lot of things could cause your issue, but the one that makes most sense is lack of fuel or running lean. I would install a fuel pressure gauge inline tape it to the windshield and do some WOT runs just to make sure supply is good. ON old cars I have had rusty fuel lines and cracking rubber connection cause the fuel pump to pull air, many times right where the line comes out of the tank. You can even install a vacuum gauge at the end of the fuel line start it for a moment, pump should pull a vacuum and hold it even after you shut it off, a quick bleed off equals problems with lines. Other issue is gas is not the same as in 1970, you may need to install or drill your jets slightly richer, I would look at the plugs to see if they show lean.

 

[Sportfury70]

They are 287 jets. I was thinking about running a 1/16 bit through them

 

[Sportfury70]

OK. You go to 3/4 WOT & it shakes, loses power.
[1] What happens if you go to 1/2 WOT?
[2] Is the engine perfectly smooth at all times except at 3/4 WOT?

It idles great, starts easy (unless it’s really cold out), and runs at 1/2 throttle no problem. Every once in a while there was a hiccup on the off-idle transition from a stop to accelerate, but I think I fixed that with resetting the accelerator pump rod.

I did have some issues with it stumbling and even backfiring once after I drove it for a few hours, but think that might have been the points and timing not being set correctly. I think I have that fixed now, but haven’t taken it on a long road trip since the rebuild and new plugs.