holley help...

[camshaftgsxr]

355/700r4 with a holley (who would think i would have any problems huh?) from cold start to warm throttle response is amazing in neutral but when its in drive it doesn't wanna accelerate at all just stumbling and falling all over itself, even when the rpms are up at 2000-3000 it won't speed up even with very little throttle, the carb is a 600cfm holley with only about a thousand miles on it, i have done manifold vacuum tests and adjustments and other things but nothing, i watched the holley instructional video on carb tuning and i tried to get it dialed in but no help... any suggestions

thanks peoples

[78swest]

time to upgrade to a edlebrock lol two screws cant mess that up

[69BBsuburban]

Sounds more like a timing issue. Lazy advance, etc...

[cableguy0]

Where is your timing set at? Timing needs to be set before you mess with the carb. Most people do more harm than good when trying to tune a carb. There is a ton of tuning info in the engine/drivetrain section. A holley is a much better carb than the edelbrock. Theres a lot more tuneability and a holley will make more power every time. Have you checked your fuel filters? Is it running really rich? Is it smoking?

[mrh33916]

I agree with cableguyO, make sure the timing is right, but one thing you can easily check on the carb. is to make sure the accelerator pump is working properly.
Without the engine running look down into the front of the carb. and rotate the linkage to WOT.
You should see two good streams of fuel shooting down into the carb. If not you have a lean condition when trying to accelerate.

[joe231]

is it a vacuum secondary carb?

[leegrady]

Blown power valve.

'81 GMC K2500 longbed, 350/sm465/np-208/Corp. 14bolt.

[camshaftgsxr]

yes vacuum secondary, no to edelbrock, no to the powervalve, and timing is an issue i'll have to check it when i get it back in the garage, the only thing i'm bothered by is it will run fine for a month then go bad

[staggerd86c-10]

could be due to cold weather too, maybe you put bad gas in it, alot of gas stations are skimping on the fuel. I have a gas station by my house that if i put gas in one of my carbd cars it runs like sh!t. I have the same problem but i narrowed it down to the carb and im just replacing it with a double pumper, i have a 670 street avenger now but i cant get it to run the same again.

[leegrady]

At the risk of sounding condescending, how do you know the powervalve is ok?
Did you visually inspect the valve? Did you replace it with a known good one? Is your Holley a newer or modified carb in which the baseplate has the passage removed or blocked that causes the powevalve to fail when the engine backfires?
You describe a problem in which the engine performs badly under load, that occurs sometime. Stuck weights on the centrifugal advance? I doubt it. How about fuel delivery to the carb? Defective sparkplug wires under load will cause the complaint you described. Stuck valve(s). Cold weather? With all due respect to staggerd86c-10, I run my truck this winter at minus 20 below zero in the morning no problem. Chevy GMC trucks will run upsidedown in the ditch in ten feet of drift. Cold temp be damned. The truck was born to run. Find the problem, fix it, be happy.

Set base timing, and then check centrifugal advance, then vacuum advance with a timing light with a built in advance gauge to measure total advance.

I run my lawn mower on 112 octane. Yeah, need good gas.

81 GMC k2500 350/sm465/ corp 14 bolt/ dana 60 ft.
95 Thunderbird lx 4.6L
65 replica Daytona coupe Stroked 351w eight single Holley toilet bowls, modified ECC-4/tremec tko 5sp/9inch detroit locker 0-60 3.4sec/ 1/4mile 11.1/ top speed 180mph. Accelerates harder at 130 than a vicky police interceptor in first gear.

[camshaftgsxr]

Originally Posted by leegrady

At the risk of sounding condescending, how do you know the powervalve is ok?
Did you visually inspect the valve? Did you replace it with a known good one? Is your Holley a newer or modified carb in which the baseplate has the passage removed or blocked that causes the powevalve to fail when the engine backfires?
You describe a problem in which the engine performs badly under load, that occurs sometime. Stuck weights on the centrifugal advance? I doubt it. How about fuel delivery to the carb? Defective sparkplug wires under load will cause the complaint you described. Stuck valve(s). Cold weather? With all due respect to staggerd86c-10, I run my truck this winter at minus 20 below zero in the morning no problem. Chevy GMC trucks will run upsidedown in the ditch in ten feet of drift. Cold temp be damned. The truck was born to run. Find the problem, fix it, be happy.

Set base timing, and then check centrifugal advance, then vacuum advance with a timing light with a built in advance gauge to measure total advance.

I run my lawn mower on 112 octane. Yeah, need good gas.

81 GMC k2500 350/sm465/ corp 14 bolt/ dana 60 ft.
95 Thunderbird lx 4.6L
65 replica Daytona coupe Stroked 351w eight single Holley toilet bowls, modified ECC-4/tremec tko 5sp/9inch detroit locker 0-60 3.4sec/ 1/4mile 11.1/ top speed 180mph. Accelerates harder at 130 than a vicky police interceptor in first gear.

don't worry about sounding condescending its a new carb. i know its not the power valve, i'm gonna check the timing i'm pretty sure its to far advanced and has to slow of a timing curve making it run good up top but stumble down low, will post up progress after i check/fix the timing

ps. plug wires are new but i haven't been into the distributor yet so i don't know..


here is a vid of the truck, ignore the moron waving from the cab... sound is okay but you can here it stumble only under load at low revs then run fine after a few hundred more rpms

YouTube- cameron's 1984 chevy silverado burnout

[leegrady]

watched the clip. Sounds like it almost died there didn't it? Sounds like a bit of a cam in it too.

Automatic transmission, and a cam means the idle must be set higher than stock.

Perhaps the secondaries are opening too soon.

Also, if it is an auto trans. what is the stall on the converter?

[camshaftgsxr]

Originally Posted by leegrady

watched the clip. Sounds like it almost died there didn't it? Sounds like a bit of a cam in it too.

Automatic transmission, and a cam means the idle must be set higher than stock.

Perhaps the secondaries are opening too soon.

Also, if it is an auto trans. what is the stall on the converter?

yes its got a cam, 270h nothing big but the trans is a 700r4 and the stall is stock for what ever vehicle it came from.. idle is set at the spec on the rad. core support so 550rpms (which i did recently set lower but it ran fine for a while), but it does is at lower rpms as well, like when driving at 15mph if i roll on the throttle it stumbles.. any ideas? please feel free to ask more Q's i'm very willing to assist someone helping me

also this problem came from nowhere, i mean i parked it for three months after the harness fried and then put new gas in it and it still does it, but when i was driving my truck everyday it would begen to get worse until i readjusted everything again (about every 500 miles)
thanks guys!

[cableguy0]

Once you get into changing cams are carbs etc that sticker on the core support means nothing. The idle is too low. The stock stall is hurting you bad.Timing and idle factory specs are useless to you. That cam isnt huge but its pretty healthy. You need at least a 22-2400 stall it would likely respond best with 26-2800. Timing needs to be set at a total of 36-38degrees all in by 3k rpm. Idle timing will end up somewhere in the 14-16 neighborhood but the distributor needs to be curved.To be honest with the wrong converter its going to fall on its face coming off idle regardless what you do. Does it try to lurch forward at red lights?

[leegrady]

I agree with cableguy0. The idle should be around 750 with an automatic transmission. Possibly even higher esp. with the aftermarket bumpstick.

I agree too that without a higher stall converter it will never have any low-end. Could even be too that the stator in your stock converter is not locking up. This will without a doubt cause very bad acceleration. But, I'm really just grasping at air with that one.

The fact that you described the problem as coming on from nowhere leads me to believe that it is timing, carb, bad coil.

[camshaftgsxr]

i bumped up the idle and it helped out, i think you guys are right about the stall being too low.. my tranny guy told me it needed a higher stall converter but i didn't ever think that would cause my problems (sturttering and such) on acceleration

and yes it does lurch at stoplights..

[cableguy0]

You need a converter. You will never get it to run right especially right off idle.The engine is going to be lugging too hard to get moving

[camshaftgsxr]

alright thanks, can too low a stall hurt my trans?

[cableguy0]

No its just going to hurt performance.

[camshaftgsxr]

well that sucks...