another flathead with a bog problem

I am looking for ideas as to whats going with my 8ba. I have a bog when you step on it and i can't figure it out. It is a 8ba .080 over, super dual manifold with holley 94's, 4.5 power valve, 47 jets, gmcbubba distributer and a t5 if that matters. I have checked for vaccumm leaks around carb bases and throttle shafts. I keep wondering if it is related to my pcv setup i have rigged up which consists of 1 inch carb spacers and that have 5/16 lines run off and t'd into 3/8 line into pcv valve. any ideas for me to check or try?

thanks
mike

 

Plug the PCV lines and see if it goes away. If it does, you need a PCV that is valved differently then the one you are using.

 

The issue I had with my 8ba with a single 94 on the stock manifold still running the road draft set up was taken care of by getting a tight throttle shaft. I had the issue pop up again an the first good cruise after rebuilding the carb, but it turns out I hadnt pushed the accelerator pump link in far enough to catch the "detent" and it had pulled out of the throttle shaft, leaving me with no acc. pump. Just a couple other things to check after confirming the PCV.

 

Throttle shaft leaks can be temporarily patched with some grease, just to see if anything changes. Like plugging the PCV, just a diagnostic.
Usual suspects would be slow advance (you want it to get moving right off idle), accel pump shot, lean idle...
Adjust idle mix screws
Slowly rev engine idle--1,000 or so with timing light. You want advance to start right up and keep going...something in there might be gummed up.
Try accel pump adjusts in winter hole, middle hole, summer hole...see what happens
for a very crude mixture test, run car through the bog range over and over, pulling out chokes a bit more on each pass, and see if there is an improvement or worsening.

 

As expected Bruce is right on. But also make sure your choke plate isn't partially closing during high acceleration.

 

Try 51 jets and stock 7.5 power valves.
Mine ran like crap with 48's. Must be worse with 47's.

Make sure the power valves are seated properly, the fuel pressure isn't overpowering the needle valves and the accellerator pumps are working.

PCV setup shouldn't effect it, you could pinch it off temporarily to check for a difference.

I have 52 jets in my Holley 2100's, but they have a 1" venturi. 94's are 15/16" so try the 51's.

Mart.

 

Did not focus on jet size...that is indeed likely to be getting into lean turf! Choke test will ID that if it's the problem.
Let's see...Regina is at somewhat under 2,000 feet elevation...you are at Ford spec jetting for 10,000--15,000 feet elevation...
Yup, you are going to have to move!
Who has a topographic map of Canada handy?

 

Having to move sounds like a pretty drastic fix. Couldn't he just add more carb spacers to make the altitude adjustment???

 

regina is 1890 feet above sea level so thats alot carb spacing. i will try choke test never thought of that.

 

J Twitero is right, re; that accelerator pump link,...That was problem with that carb, until they stopped using it in the 50's !! PCV,...I put the valve into the manifold, well below the carbs.....I opened out a plugged vacuum port in the offy 2x2 mainfold, and threaded it for the pcv valve. The line then goes to where the road draft tube used to go, in front of the manifold. Hope this helps..... 4TTRUK

 

Quick question... if my power valve was leaking wouldnt i have problems with idling. It starts good and idle perfect right now, my only real issue is this dam bog....

mike

 

Another issue can be blown power valves. if the carb's have had a backfire through them, the power valves will be shot.

 

If you have a bad seal between PV and carb body, any leakage goes right down the vac passage into engine. If leak is large, you will see black smoke and have very crusty sparkplugs. You would also have poor performance above idle, degree dependant on amount of leakage. Also carb will empty quickly when parked...bad seal there is straight out the bottom of the bowl.

 

If the power valve is leaking you will find the engine starts easily and does not need hardly any choke - it's already over rich. If you don't realise the power valve is faulty you then wind in the mixture screws (leaner) to compensate.
Not mentioned yet are the accellerator pumps - which hole are the links in? Mine tends to want the richest hole on both carbs.

Mart.

 

I finally figured it out last night. the accelerator pump on one carb came off. I put it back on and it made all the difference. thanks for for all tips. I learned alot the last couple weeks i have been diagnosing this.

mike