Inliners International Forums General Discussion Hi Performance Holley 4 barrel bogg

I have been experimenting with the smallest Holley 4 barrel, a 395 cfm model 8007 on my 302 GMC inline 6. It bogs when I take off normally. Once the high speed circuit kicks in it runs fine.

Holley says to play with the accelerator pump cam and nozzle sizes. I have but it still bogs.

I also thought the vacuum controlled secondary barrels might be opening too early. I wired them closed and it still bogs.

Any ideas?

Is the intake heated?

Could be many things.

Try the next size squirter. Could be the cam lobe. Try switching the screw hole. Could be the arm is out of adjustment. Look it up on Holley's website. Could be timing.

double check your timing and make sure that the advance is working.

Hi, I'm working through bogging too. One big, positive change was to put a heavier spring into the secondary to slow the opening. The guys here say my plugs look lean, so probably some jet work too. There's some discussion of O2 sensors now to do a better job tracking it down (My 230/250 Build), fyi

It seem to be in the transition phase of the operation. It idles well and accelerates great but just off idle it dies. Does anyone know what controls the transition phase between low speed and high speed operation. It can't just be accelerator pump and the raw gas squirt jets. There must be a transition circuit within the carb with jets and air passages somewhere?

It's most likely your power pump. If the cam and cam arm are adjusted right check the pump itself.

Sounds like the PV (power valve) is not working. Simple to replace and cheap to buy. You will need to remove the float bowl and jet plate to access.

Test it first before going that far.

Start the engine and while at idle cover the carb with your hands. If it stalls the PV is fine according to Holley.

I really think it just needs an adjustment.

"half of all carburator problems are located in the distributor"
I'm not positive where that came from, but it has proven to be great advice. It is quite a bit of work to unhook, unbolt, and disassemble a carb. Quite a bit less to make sure we have good spark at the proper time.
Timing can affect how well the carb works. Holleys have a transition circuit that is very sensitive to where the throttle blade is at idle. When the engine doesn't have enough vacumm, we open the throttle with the idle screw to get the idle speed we want, but that affects the idle transition port.
You need to hook up a vacuum gauge to manifold vacumm. There are two vacumm ports on the Holleys. One is ported, one straight manifold. The ported one will have the lowest vacumm at idle. When you identify it, plug it and forget it. Your jimmy distributor was always on manifold vacumm. Unhook the vacumm line to the dist and slowly advance it until you find your highest reading, then back the timing off until you've lost 2*. This is a good baseline setting. Hook the vacumm line back up and set your idle speed, and adjust the idle mixture using your vacumm gauge. Now, watching the squirters, rotate the throttle. They should start immediately. If not, adjust. Take it for a drive. If it is still bogging, you'll need a larger squirter. Holley makes them from mid 20s- mid thirties. The power valve enrichment circuit default is full rich. if the power valve is compromised it wouldn't be the problem here. Sorry for the long post

Sorry. When I said to advance the distributor untill you got the highest vacuum reading and then back it off 2, I meant 2" on the gauge. For instance, if 20"was your highest reading, back it off to 18". It will give you a good baseline.