Low power up hills new carb

S

Steve Grant

Member
Truck in question- 1972 1210, 4x4, 4.10 gears, 392, spreadbore, 13 inches in mercury at 5480 ft in elevation, pertronix ignition in the stock Holley distributor, set the timing 20 degrees. I had a edelbrock 1406 on the engine prior, using a edelbrock adaptor. I replaced the carburator, because I was having a hard time getting the truck started in the cold. I replaced the plugs, plug wires, cap and rotor, air filter, still had problems. I installed a Holley 0-80457s 600 cfm carburator on the engine. Truck starts fine now in the cold, good power on flat ground, but when I go up into the mountains, the truck falls on its face. It did not do this when I had the 1406 installed, ran very well. What do I need to do to get this truck back to where it was before??
 
Sounds like you got some dirt in there some where when you switched the carbs. Fuel filter? Needle valve? Float not allowing enough fuel in? Sounds like something like that to me...

20 deg advance seem like a lot of advance ??

There are many folks that have far more knowledge on this board then I do, I am sure if my ideas are off then can get aid in solving this problem....
 
Engine has been power timed, does not ping. Fuel filter is new. Ran great with the edelbrock, I'd do 70-75 up floyd hill with throttle left. Read about mayben's power timing.
 
Re edelbrock - did you check the position of the choke plate when the engine was cold?

Assume it started fine in summer, so I assume the choke May have been not letting enough air in... Needed to be readjusted for cold weather...

Holley - is it brand new? It is possible it is a bit too Rich for over 5000 ft elevation.
 
I did check the choke plate, I set it for the cold winter, even left it same spot during the warm months. The Holley is brand new. 64 jets, 65 power valve, plain secondary vacuum spring. 600 cfm, same one mayben uses, 0-80457s.
 
At what rpm and throttle setting does it fall on it's face?
Is it low on power with only the primary barrels open and looses power as you open the secondaries?
 
Hope you all had a merry Christmas, sorry for not replying back quickly. Mr. Kennedy I found the issue. It was the power valve, I went to a higher number, truck runs like champ like it should. I put a paper clip on the secondary vacuum actuator rod to verify that the secondarys were opening, and drove it up I-70, going up the mountains, pulled off the road, the paper clip was pushed down verifying the secondarys opened. I don't have a tach in the truck, hoping to pick one up soon with some Christmas money...truck is running fine now.
 
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