hesitation/bog 66 C10 w/283

[indy66]

I've searched and read through a bunch of threads on here and other forums about his issue and am still having problems so i'm posting this to see if anyone has any ideas what the problem could be.

When accelerating from a stop I am getting heavy bog and sometimes the engine dies. There is also some hesitation when lifting off the gas while driving then reapplying throttle. Other than that the idle is fine and once I get going drives fine until i lift off the gas.

The truck is a 66 C10 with a 283 and 2B rochester, all stock.

Here is what i have done to try and correct the issue:

Carb tank soaked and rebuilt

accelerator pump replaced with rebuild and checked ok

New rotor and cap, dwell set to 30* (points look newer)

New R45 plugs gaped to .35

Gas tank drained and filled

Fuel filters changed (inline and in carb)

Originally had a inline filter between carb and pump and i reconfigured that to 1 inline before fuel pump and one in the carb

Timing initially set to 4* then advanced to 6* then again up to 8*-10*-12*
I also checked dwell and idle RPM again every time I advanced the timing. The timing advance seemed to help some but it still will die if i give it too much gas when accelerating.

Any help is appreciated!

 

[vwnate1]

Flat Spots

Thanx for the preamble , it helps .

I'm assuming you've tested and there's no dizzy vacuum @ idle but it jumps *instantly* when you open the throttle ? .

If not , there's your problem : dizzy vacuum advance is to overcome off idle flat spots .

Check that and report back .

 

[joek3167]

I say vacuum advance to

 

[indy66]

thanks for the replies, i tested the vacuum advance this weekend and the diaphragm was blown. Replaced that and it seemed to work great. I also set the timing back to 8*

While i was out test driving i had a huge backfire from the tailpipe and started to sputter a little after that and back to bog at acceleration. Got home and found #4 plug wire was melted, the strap came loose and it was laying next to the header. So i'm guessing that when it melted and sparked to the header it caused the backfire, which also blew the header-exhaust gasket. though the exhaust leak could have been there already and i didnt notice it, i'm not sure. Im going to get a new set of wires at work today and see if that helps.

Could the faulty wire cause the same bog issue?

 

[vwnate1]

Re : Rough Running

The backfire is likely what blew out the vacuum biscuit , re check it again .

If you're on a tight budget , the junkyards are chock full of good used plug wires , just ensure no cuts / abrasions and the ends & length match , after you've paid for them , _gently_ clean off the grime with hand cleaner and a clean(ish) rag ~ you'll be amazed at how good they look .

Use a test light and battery in the yard to test continuity before paying ! . if the test light won't light , the wire is kaputi .

I got the entire HEI setup off a '77 Nova for my old '69 C/10 , the underhood of that Nova looked like someone had poured tar or used grease all over the engine but I $aved $eriou$ $ and spent an hour cleaning , everything looks new now and of course , the short free wires made my engine run smooth & strong again .

 

[indy66]

The backfire is likely what blew out the vacuum biscuit , re check it again .

If you're on a tight budget , the junkyards are chock full of good used plug wires , just ensure no cuts / abrasions and the ends & length match , after you've paid for them , _gently_ clean off the grime with hand cleaner and a clean(ish) rag ~ you'll be amazed at how good they look .

Use a test light and battery in the yard to test continuity before paying ! . if the test light won't light , the wire is kaputi .

I got the entire HEI setup off a '77 Nova for my old '69 C/10 , the underhood of that Nova looked like someone had poured tar or used grease all over the engine but I $aved $eriou$ $ and spent an hour cleaning , everything looks new now and of course , the short free wires made my engine run smooth & strong again .

The backfire was after i changed out the biscuit, i think it backfired due to an exhaust leak. New plug wires seemed to have cleared up most of the issue, have to pull the choke out a little after stopping so i'm going to go through the carb again. Thanks or the junkyard advise, i work for a large B2B distributor so parts are almost at cost which makes things insanely cheap.

It seems like the remaining issue is puddling after I stop, so i'm going to adjust the mixture. I'm just guessing on that, but if I pull out the choke a little when im stopped i can go with no problems so that makes me think lean? How many turns out do you recommend?

 

[vwnate1]

Intake Manifold ' Puddling '

This is caused by float valve leaking or the float sinking .

Often , a *tiny* bit of smurf gets caught in the float valve , this is why the paper element , micronic fuel filter is supposed to be mounted right at the carby's inlet .

The mixture screw , *gently* bottom it then back out 1- 1/2 turns ~ a " turn " means 360? , not a twist of your wrist .

I hope you looked closely at the tip of the mixture screw , if it's bent or has a tiny flat spot on one side of the tip , it's JUNK and cannot be fixed nor re used .

 

[indy66]

This is caused by float valve leaking or the float sinking .

Often , a *tiny* bit of smurf gets caught in the float valve , this is why the paper element , micronic fuel filter is supposed to be mounted right at the carby's inlet .

The mixture screw , *gently* bottom it then back out 1- 1/2 turns ~ a " turn " means 360? , not a twist of your wrist .

I hope you looked closely at the tip of the mixture screw , if it's bent or has a tiny flat spot on one side of the tip , it's JUNK and cannot be fixed nor re used .

Thanks Nate. I'll readjust the idle, I have it at 2 turns out now which probably is part of the problem. Mixture screws look good, had those out a few days ago to check and the float is a new brass float. I do have the in carb filter installed, however it is brass and not paper. From what i read here it could be puddling:

http://www.thecarburetorshop.com/Troubleshooting.htm

 

[indy66]

Here is a pic of the truck, kind of bad but i'll get some better ones.