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Bogging on hard acceleration
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Author:  shadango [ Wed Aug 15, 2018 8:44 am ]
Post subject:  Bogging on hard acceleration

So my son rebuilt his slant 6 carter BBD two BBL a couple weeks again and all has been fine including a 4 day road trip....A thousand miles or so since the rebuild.

Last evening it started bogging on moderate to hard acceleration .....it runs fine other wise.

Stab the pedal and it bogs and sometimes stalls.

Seems like accelerator pump to me and I told him to check the setting, and open it up some if it's still at the "correct" setting.

No other issues that we can find yet. Fuel filter was changed before the trip.

Any thoughts on this ?

He goes away to college with it in just 3 days .....don't want him to have issues while away at school.....

Thanks for any help folks.

Author:  Greg Ondayko [ Wed Aug 15, 2018 8:58 am ]
Post subject:  Re: Bogging on hard acceleration

Dave, Check everything Like Fuel filter, Inlet screen, Fuel pump, the Pump shot can be easily adjusted on these carbs with a flat blade screwdriver so some tuning trips are needed there with the screwdriver in the car.

Another thing to consider is the Air filter (new or clean one) and the Charcoal emissions can - those can disintegrate leaving the maroon 80 f body well totally marooned... :-(

It can pull a bunch of carbon pellets into the whole carb and block stuff up.

Also if all of that checks out tuning with a wideband o2 gauge can help.

Can you tell if its bogging due to overrich or over lean?

Greg

Author:  shadango [ Wed Aug 15, 2018 9:16 am ]
Post subject:  Re: Bogging on hard acceleration

Well, at midnight its tough to tell anything. LOL He got home from work at 11 and we took it for a ride.

It feels , to me, like its leaning out.....if you ease on the accelerator it doesnt do it at all....the faster you punch it, the more it bogs...I even got it to stall once. Feels like too much air, not enough fuell runs clear once it gets past that. No issues kicking down into passing etc. ONLY happens off-idle far as I can tell.

When he had the carb open at the last rebuild there was a little rust in the bowl....so clearly we need to take a look at the tank and lines at some point...had him swap in a new fuel filter right away.....it had been running fine though before the rebuild, just had leaky gaskets and the float seemed high....

After the rebuild all was great....like I said....for 1,000 miles he has informed me.

We DID have a lot of rain lately and I suggested maybe something got wet or some water got in the fuel....but it really seems to be running fine aside from the off idle bog/hestitation.

As far as the charcoal cannister....so unplug the canister I guess and cap the carb and check....

He says thatas far as he can tell the pump shot is "maxed" at the setting it is at now, which hesays is measuring what the book says...I am thinking he may have that wrong.

But , still, the car ran great the last 1,000 miles and then all of a sudden........I dont figure it is the pump as it doesnt feel lean on acceleration once you get past that initial bog.

There is no screen on the inlet.

Wonder if the pump diaphragm could have failed this soon? It was a new parts store kit.

Author:  Dart270 [ Wed Aug 15, 2018 10:23 am ]
Post subject:  Re: Bogging on hard acceleration

Sounds like accel pump. Can you look down the carb and work the throttle linkage and see if it is shooting one strong stream into each barrel?

Lou

Author:  drgonzo [ Wed Aug 15, 2018 11:03 am ]
Post subject:  Re: Bogging on hard acceleration

Timing can give those same symptoms. Sometimes the worst fuel issues are electrical. ;)

Author:  shadango [ Wed Aug 15, 2018 7:03 pm ]
Post subject:  Re: Bogging on hard acceleration

Quote:
Sounds like accel pump. Can you look down the carb and work the throttle linkage and see if it is shooting one strong stream into each barrel?

Lou
Thats exactly what the son did today, and says he sees no gas squirting.

So, he is gonna pull the carb off first thing in the morning and pull the top half of the carb off and see whats up.

It was a brand new carb kit.....could the diaphragm have gone bad just like that?

Where do you guys stand as far as reusing the felpro base gasket and the airhorn gasket? He actually has another airhorn gasket from another kit he already had (older kit) as well as another diaphragm....but not a base gasket.....we are using the thick felpro deals (60188) as opposed to the thin ones.

Author:  emsvitil [ Wed Aug 15, 2018 7:53 pm ]
Post subject:  Re: Bogging on hard acceleration

You might be able to pull the top off the carb without removing it from the manifold.

I've done this on my BBS...….. I take off the 2 short screws hold the top, then 2 of the long screws holding the whole body to the base. Then put the 2 short screws on the middle to base to keep it on the base. (not sure if this works on BBD, but it might)

Author:  Dart270 [ Thu Aug 16, 2018 3:49 am ]
Post subject:  Re: Bogging on hard acceleration

Could be a faulty new diaphragm. I bet you can pull the top off and replace the acc pump w/o disturbing much (hopefully including the gasket). A new carb kit would have a gasket though, right?

Lou

Author:  shadango [ Sat Aug 18, 2018 10:12 pm ]
Post subject:  Re: Bogging on hard acceleration

SO, just to update --- turns out the cup on the accelerator pump inverted......

My son decided to try leaving the carb on the car and just pulling the top and it worked fine.

He used a pump from an old kit we had sitting in storage....green cup.

He said that when he first replaced it and tested the car, it still hesitated some....adjusted the stroke on it and that was the final fix.

At least it was an easy fix.

Thanks to all who suggested stuff!

Author:  Dart270 [ Mon Aug 20, 2018 5:18 am ]
Post subject:  Re: Bogging on hard acceleration

Fantastic.

Lou

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