Barry, Load that V10 up with a load of your rusty $$$ and go buy yourself a new carb.

hohoho , Jim , i don't have any $ !  euro's ?? 
ofcoarse i can buy a new carb but that's not the game ! i must find  the  solution  and be glad to have solved that problem !  and also  every time  i have to drive to speedshop ( some 30 miles ) with my Ram i enjoy it ...... just went for 2 gaskets of 5 $ total , but you don't want to know what it costs on gas.........

you don't want to believe it .....
find the "right" ( they fit the passing pins and resamble pics on internet ) gaskets, figured out about their difference , ( That litle hole must be seald around as it is a passing tubing for the pumpers).
Installed new gaskets,new power valve.
Again i have a perfect starting, perfect idle, perfect reving stationary ,( no colored exhaust fumes )  .... but driving he stops at 3000 rpm  and  begins pufpufpufpuf's.....
Now i'm really out of thinking what to change..... That 3000 rpm , and in all gears !...????? what could that be ? tryed it with static advance between 2 and 10° , always the same. Put a 36° mark on the damper and checked with timing light , i must have 10 to 12° static to reach that 36°.Dwell is perfect 30°.The optimum vacuum is about 8 tot 10° static.
Checked all plug wires with ohm meter. seems OK
New spark plugs, checked firing order.
All dubble checked.So i claim the carb.
But on the carb you cannot do much. Just checked the fuel level in the bowls ( sight holes ) , OK , the pumpers and throtles work, the jettings are clean ,find no vacuum leak , all gaskets are new, don't mind choke items as they are all removed .

Perhaps buying a new one ???? As our first Belgium Vette meeting is next month , so deadline becomes closer and closer !

This may sound stupid - or may have been covered - But I had a 350 Chevelle that did the same thing - I finally traced it to dirt in the carb bowels . I cleaned the bowels - changed the gas filter for the next few weeks and that solved the problem - Hope it helps

Big Al

Thanx. already cleaned the bowels , they where even perfect clean.  

I have now a pressure gauge witch i install tomorrow to see my fuel pressure, while driving .... perhaps the pump ?????

It keeps me out the bars !

Within the gas tank is the pick up and sending unit- this has a fine metal mesh screen attached. Could this be partially clogged and at higher PRMs- need for gas - the flow is constricted/restricted  by the cloged mesh filter ?? Just a thought

Big Al

I'll check that but don't suppose it as it's all new ( even the gas-tank ) . The car was off frame restored to new in '99. I can even look in the mirror trough the gas at the tank -bottom !

 

Barry,

I just found this thread today. If you had a blown power valve, it would cause it to run rich at low RPMs since a blown valve constantly leaks fuel. It would be OK at high RPM. If the power valve was stuck shut it would result in a big bog on throttle opening but would eventually catch up.

Sounds to me like you are running out of gas over 3000 RPM. Maybe a bad fuel pump or clogged pickup or fuel filter. If you can tee your fuel pressure gauge line in up close to the carb then run the line long enough to get in the car, watch your fuel pressure when she goes "pufpufpuf" and see if the fuel pressure drops.

Another thing you might check is your choke sucking shut on wide open throttle. Try adjusting your choke tension spring holding the choke open and see if that fixes it.

I'll bet anything it's something simple and you'll get it fixed. You are one persistant bugger!!!

Dave

Another thought - there is a vapor return line  from engine back to gas tank - could this be constricted , - bent, clogged, pinched - such that it causes problems at high rpms - -like a back pressure which inhibits fuel from getting into the carb - just a wild thought  as it seems that it could be fuel rather than spark issue

Big Al

I like Autom8r's

"Another thing you might check is your choke sucking shut on wide open throttle. Try adjusting your choke tension spring holding the choke open and see if that fixes it"

Simple but its a could be cause

thanx guys for helping surching solutions. BUT look what i find today :

installed a pressure gauge on the fuel line running a long hose in the car and driving it. Pressure was OK , 0.4 bars and constant.
Changed gaskets under carb to be sure about vacuum leaks. Seemed OK and indeed, , problem was the same.
Wanted to be sure about the firing order so dicided to remove the rocker covers and to watch the valves to see it followed the firing order as  in the books.... LOOK WHAT I FIND :

the selflocking nut on exhaust valve cilinder 1 had broken (the locking part above the nut ) and that nut had to be vibrated up and up untill there was as much play that the valve wasn't anymore working!!!!!!!
 One side is cracked , the other side lost a part. Luckely i find the missing litle piece still on top of the head.

All nuts seem to be new , as the engine was rebuild. Perhaps a factory fault ? I think to buy 16 new ones , original GM's ?

O GOD O GOD , does this means i found the problem ???? i think so , this is in fact a really BROKEN part , so cilinder 1 was pumping against a closed exhaust valve ....So , monday to the store for new ones and find out !!

YIPI YIPI YIPI YIPI YIPI

 Hopefully this means the end of this thread ! story to be continued !