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Old 12-01-2010, 07:59 PM
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should i rebuild my 305 vortec or swamp for a 350

i have a 1997 gmc 305 vortec with 380,000km on it and don't wanna sel my truck but would rather rebuild it, because i don't wanna spend the money on more stuff for a different motor. or what would you do and what would it cost?

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Old 12-01-2010, 08:46 PM
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My 85 C10 has a 305 V8 with a lockup th350. Performance goals are straight line acceleration of a LT1 corvette. That adds up to a 14.2-4 1/4 mile. Very hard to do with a 305 V8 and th350 with 2.73 gears.

The usual upgrade to vortec heads are great idea on the street. Add a perfomer intake and performer cam to the QJet, and the 305 comes to life. The stock 4bbl intake to performer intake is not that much more. The stock 305 cam had .381/.410" lift 187/202 degree duration at .050. The Edelbrock cam with .420/.442" was a kick in the pants. Big difference in power from 1000-4500 rpms . The Vortec heads made the biggest difference. The heads by them self add 55 hp and 15 # torque.

The HEI curve and Q jet carb were modified for performance. M hanger with DR rods, mod secondaries for full opening set 5/8 turn door tension.

The trans H350C has the lockup on a switch. Governor mods with TCI kit. Yellow and blue spring 2/5 weights shifts at 4700 1-2, and 4900 2-3.

B&M governor calibration kit for WOT.....THIS IS JUST AN APPROXIMATION!!
GM#24202127 = 4400 rpm
Blue&Yellow 2 & 3 = 4900 rpm C10 tried good torque jump to 2nd at 4300
GM#24202117 = 5000 rpm
Blue & Yellow 4 & 3 = 5100 rpm
GM#24202122 = 5200 rpm
Blue & Yellow 2 & 5 = 5300 rpm C10 tried revs out till done at 4700
Blue & Yellow 5 & 3 = 5500 rpm
Blue & Green 4 & 5 = 5600 rpm
Blue & Green 3 & 5 = 5600 to 5700 rpm

All this and my C10 is not even close to low 14's. Burnouts and clowning around are fun. For corvette acceleration the trans needs to be changed. A 700r4 with 3.42 gears shuld get me the rest of the way.

$1,500 for trans and 2000 stall
$590 for 3.42 rear gear kit

Keep saving. Swamp.
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Old 12-01-2010, 10:46 PM
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350

305s are terrible motors i wouldnt put any money into a 305 i would put a 350 in it if u want power over gas mileage if u want gas mileage buy a honda
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Old 12-02-2010, 07:36 AM
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Since you are used to the 305 then you will really notice the extra power if you put in a cam, edelbrock intake, and a 4bbl carb. The compression ratio on that motor is probably very low. When you rebuild it, give it some more compression. I would do 9.5 but no higher. Then you could do a nice port job on the heads to improve airflow whick will also be good for some extra power. I also agree that the rear gears would be good to change.
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Old 12-02-2010, 10:37 AM
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Must be just me.

How would you get LT1 corvette straight line perfomrance from a big truck?

Last edited by spinn; 12-02-2010 at 10:44 AM.
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Old 12-02-2010, 06:45 PM
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Quote:
Originally Posted by spinn
Must be just me.

How would you get LT1 corvette straight line perfomrance from a big truck?
Add a Blower or N2o.
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Old 12-02-2010, 06:48 PM
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Originally Posted by SSedan64
Add a Blower or N2o.
life's not fun without those. lol
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Old 12-03-2010, 12:21 PM
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Quote:
Originally Posted by deisel power
i have a 1997 gmc 305 vortec with 380,000km on it and don't wanna sel my truck but would rather rebuild it, because i don't wanna spend the money on more stuff for a different motor. or what would you do and what would it cost?
Rebuild the 305 Vortec and slip the '385 Ramjet/Marine roller cam in it. On paper it doesn't look much different than the stock Vortec roller but it will give it a nice mid-range boost and won't kill your low end or drive the ECM nuts.
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