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Old 04-24-2011, 10:40 PM
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help with 305 hp

I have an 85 el camino. I bought some accesories and was wondering howmuch HP I would gain, and how I could get more? 270 cam, long heddman headers (straight pipes, no cats) new timing chain, .030 bored, rpm air gap intake manifold, lifters, perform 1.5 rockers, valve springs, edelbrock 4 barrel carb, and I'm getting a valve job on the heads. and I'm thinking about buying some iridium spark plugs. Also I will be putting in a 700r4.
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Old 04-25-2011, 05:56 AM
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Quote:
Originally Posted by elcamino_bert
I have an 85 el camino. I bought some accesories and was wondering howmuch HP I would gain, and how I could get more? 270 cam, long heddman headers (straight pipes, no cats) new timing chain, .030 bored, rpm air gap intake manifold, lifters, perform 1.5 rockers, valve springs, edelbrock 4 barrel carb, and I'm getting a valve job on the heads. and I'm thinking about buying some iridium spark plugs. Also I will be putting in a 700r4.
With that cam the best mod you can make is a change in gear ratio. The TH700R4 has a deep first gear and that will help a lot- but until then, expect this thing to be sluggish until it gets up on the cam.
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Old 04-25-2011, 07:30 AM
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Quote:
Originally Posted by elcamino_bert
I have an 85 el camino. I bought some accesories and was wondering howmuch HP I would gain, and how I could get more? 270 cam, long heddman headers (straight pipes, no cats) new timing chain, .030 bored, rpm air gap intake manifold, lifters, perform 1.5 rockers, valve springs, edelbrock 4 barrel carb, and I'm getting a valve job on the heads. and I'm thinking about buying some iridium spark plugs. Also I will be putting in a 700r4.

a set of 305 vortec heads and matching intake would make big gains in airflow,compression and match your cam much better.
a 2500 stall conv and 350 rear gear ratio would really wake it up

with your combo your going to gain approx 30hp

with the combo i mentioned i bet you get 80hp

do yourself and ppl around you a favor give up 5 of those hp and weld some cats in it please
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Old 04-25-2011, 01:49 PM
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thanks cobalt 327

What kind of gears should I look into?
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Old 04-25-2011, 03:02 PM
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Quote:
Originally Posted by elcamino_bert
What kind of gears should I look into?
You should start by seeing what the rear gear is now. A lot depends on how you use the vehicle for one thing. If you do a lot of highway driving, you'd want to stay reasonable, like around 3.23-3.42 range. If you are more an around town driver, 3.73's would work well.

But that's why an OD AT works so well- you can have a steep rear gear, yet the OD will pull it right on down to a highway gear.
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Old 04-26-2011, 07:28 PM
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My 305 went , Vortec heads , perfrmr cam , intake , QJet , headers with DMturbos muffs, electric fan , 3.73 with 28" tire , TH350C lock up on a switch. Great build, powerband for street, needs no stall . Busy , but driveable on the highway, 65 at 2850rpm. Problem, the 85 GM truck weighs about 4800lbs. 15.7 run at 87 mph. 17 MPG at 65 cruise at one speed no hills.
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Old 04-28-2011, 04:37 AM
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If the "270 cam" is the comp 270H magnum cam it is too big, unless you are going to use 4.56 gears and a 3500-4000 stall race converter and 10:1++ cr . Its a big cam for a 305 and won't work well with a OD trans. not much low rpm torque in this small motor.

Cut the cam choice back. 206 to 216@.050". put some 3.73-4.10 gears in it and a 10" high stall. A 10" "3500 stall converter" will give a real 3000 stall behind a 305. Its just right.

Forget the th700r4. Big waste of money.

Use home ported #4416 305HO heads or L-31 350 vortec heads.
best with .030-.040" shaved off the decks and a thin felpro 1094 gasket for more cr. Use 1.6 intake and 1.5 exhaust rockers.

Its very easy to over cam a 305.

Last edited by F-BIRD'88; 04-28-2011 at 04:45 AM.
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