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Old 05-03-2012, 06:04 PM
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350 chevy 3/4 ton carb

looking to add some power low end and high end torque to my 1986 Chevy k20 going to be a mini project. I wanted to know this truck is bone stock do i need to tear the engine apart to add some good increase in power or can I update the ignition set up and a new carb like a 1405 eddlebrok with headers I do have a flowmaste exhaust. or am I throwing money away there and just go right at the motor buy a rebuild kit do over size valves springs cams port and polish the head and new carb with pistons and rods. I'm not looking for a speed demon I'm looking for 30 to 50 hp gain to make it closer to a newer truck its pretty sluggish the motor and tyranny was rebuilt about 30 thousand miles ago. I don't want to do the carb full exhaust and ignition spend about 1600 bucks and cant even feal the diffence thanks for the help guys, first project truck

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Old 05-03-2012, 06:33 PM
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You will have to raise the compression, change the intake, carb, exhaust and camshaft to make any significant increases.
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Old 05-04-2012, 12:16 AM
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I would start with a pair of Vortec or aftermarket Vortec/fast burn style heads. Vortec heads, with NO other changes, will give you 30-40 HP. The Vortec heads will raise your compression ratio about a full point over what you have now with the 76cc stockers, plus they flow better than ANY of the earlier heads. Combine this with a dual plane intake manifold, your favorite flavor of 600-650 cfm carb, small tube headers and exhaust, with a mild cam and you will gain well over 50 HP.

This example is all priced from Summit Racing:

Summit 151124 Vortec heads with .520 lift valve springs $309.50 each
Summit 226018 dual plane Vortec intake Idle-6000 rpm $139.95 each
Summit K1103 Cam/lifter kit .442/.465 lift, 272*/282*
advertised duration, 214*/224* duration @ .050 lift,
112* LSA, 108* ICL $99.95 each
Hedman Headers 69230 $175.95/set
Holley 0-80450 600 cfm, square bore, electric choke,
single inlet, GM, vacuum secondary $339.95
Total $1374.80

Use head gaskets that will give you a good quench (about.040"). If the block has never been decked Fel Pro #1094 .015" shim gaskets with the nominal stock piston deck height of .025" will give you a .040" quench. Buy a set of self aligning rocker arms from your local salvage yard.

This build will give you 9.5 - 9.6 to 1 static compression ratio with a dynamic CR about 7.7:1. It should run fine on 87 octane gas, and should put out 325+ HP and close to 400 lb/ft torque. Compared to the stock rating of 165-185 HP (depending on GVWR) and 275-285 lb/ft torque, this should put many smiles on your face.

Last edited by BigEd36; 05-04-2012 at 12:44 AM.
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Old 05-04-2012, 01:36 AM
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First of all, what carb is on it now? Next where is the spark timing set at? What rear gears does the truck have? There are small, inexpensive mods you can do that will help with power. You could spend around $600 and get around a 40 horse increase in power if you play your cards right. Give me the info I asked and I will pass on to you what you can do so it'll make a little more power without breaking the bank.
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Old 05-04-2012, 07:54 PM
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Best thing I've done yet with my '82 K10 'Burban was swapping out the 3.08's for a set of 3.73's I had in a spare truck. It is not a 50 horsepower gain but it feels like it. I live in a hilly area here in TN and the gear swap stopped the constant downshifting up hill while cruising in overdrive. Rebuilt motor is now in the works but let me tell you it is night and day, that's with 31x10.5's and I'd even go as far to say I would have been safe going with 4.11's. Mileage believe it or not is about the same, I guess cuz it spends most of the time in O.D. now and not downshifting as much. As far as the carb goes you can't beat a properly set up Q-Jet. Hope this helps.
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Old 05-05-2012, 11:02 AM
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I just finished swapping out a 6.2 diesel in an 83' K20, to a Gen 1 350 with the newer vortec heads and serpetine setup. I also opted for the Rochester Qjet from Summit racing. I must say for a brand new start up, this carb required next to zero as far as tuning.
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Old 05-05-2012, 12:06 PM
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hey

its all stock the original carb is on it and thats why I was wondering if i should go to a eddelbrock or holley i want the more dependable one can the crank and tranny handle that 350hp if you drive it right without geting on it hard all the time. I was thinking of a 1406 eddelbrock electric choke.
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Old 05-05-2012, 03:40 PM
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A properly tuned Q-jet will out perform a properly tuned 1406 everyday of the week.

When was the last time the motor had a full tune up(cap,rotor, timing set, filters changed, carb adjusted)

What is the condition of the motor, have you done a recent compression test to check the condition of the motor.

You may just need a good tune-up to make the vehicle more driveable.

Id also agree with the axle ratio change, makes a far greater difference than adding a cam or intake.
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Old 05-05-2012, 06:01 PM
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You didn't answer any of my questions so I guess you don't want to know.
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Old 05-05-2012, 07:09 PM
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I agree sitick with a q-jet. That should be whats on it since thats what came stock. However, If the motors worn out, your just throwing money at the wrong end. How did you determine you needed a new carb? Look at it this way, is putting more "or less" air and fuel into it going to make it run any better? If not then worry about checking your ignition system, and your motor out before you drop a bunch of cash on something you may not need yet? Thats my .02
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