305 rebuild with performance parts

Discussion in 'Engine Performance + Maintenance' started by Connor C, May 27, 2020.

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  1. Schurkey

    Schurkey I'm Awesome

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    The GM TBI-to-Vortec cylinder heads intake manifold is hatefully expensive.
    Plus the EGR pipe/hose, and the fittings on each end.
    You'd need to fabricate a bracket for the throttle, cruise, and Trans TV cable if used.

    Or the Summit-brand (Made by Trick Flow) TBI heads which are a genuine bolt-on except for needing hardened pushrods.

    [Edit] The Summit heads have a 62cc chamber, so compression drops a bit on a 305. Supposedly "angle plug" heads, but no-one is complaining that the headers or exhaust manifolds don't fit. And one guy mentions that you'd need a couple of pipe plugs for a coolant port machined into each head.

    The heads come with guideplates, if you use the guideplates you'd need hardened pushrods and different NON-GUIDED rocker arms. If you use the OEM guided rockers, you don't need the guideplates or the hardened pushrods. [/EDIT]
     
    Last edited: May 31, 2020
  2. 98 Nitro

    98 Nitro I'm Awesome

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    I did not include the 87-95 Summit, Edelbrock or Enginequest heads because they are really 350 heads, 305s like small valves and chambers. EQ does make a replacement 305 vortec head though. Some good used Vette aluminum TPI heads or porting 305 TPI heads are the other options. The Vette heads also require the 86 and older intake.
     
  3. Erik the Awful

    Erik the Awful I'm Awesome

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    You also have to drill the bypass holes in the heads or run the Vortec water pump. If you run the Vortec water pump you have to plug the coolant bypass in the block. Your support brackets for the serpentine belt system also have to be modified. The accelerator/TV cable/cruise control bracket has to be reworked to give the appropriate throws. Depending on the manifold you might have to rework your PCV and brake booster hoses. Mostly easy stuff, but it takes some time to do. Having a welder also helps.
    No engine likes small valves, for the same reason backpressure isn't good. The 305's bore diameter limits valve size, which is one of its drawbacks versus a 350.
    An aftermarket Vortec performance intake with a TBI adapter isn't terribly priced.
     
    Last edited: Jun 1, 2020
  4. Schurkey

    Schurkey I'm Awesome

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    Does the aftermarket Vortec performance intake retain the bosses for the alternator brace, and the A/C compressor brace? How about ignition coil mounting bosses? EGR?

    I used a ZZ4-style manifold, getting the EGR to work was a bitch and there's no boss for the strut on the A/C compressor--which means there's no boss to mount the electronic package on the right side of the TBI. It did have the boss for the alternator brace, and it wasn't too hard to get the coil and power-booster tube mounted.
     
  5. 98 Nitro

    98 Nitro I'm Awesome

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    Ya true the 307 I had in a Nova liked the 1.94 heads better than the 1.72s it came with stock. Thought about putting my 2.02/1.6 heads on it but never did.
     
  6. Erik the Awful

    Erik the Awful I'm Awesome

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    I did forget about the junk on the passenger side of the intake. I yanked all that when I put the sniper on. None of the braces line up, but I modified my alternator brace to fit. The ignition coil bolts on as normal. No EGR boss. I tweaked the brake booster tube to fit and modified the throttle and throttle valve cable bracket. As I said, "Mostly easy stuff, but it takes some time to do. Having a welder also helps."
     
  7. Supercharged111

    Supercharged111 I'm Awesome

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    I can't believe nobody has asked this yet: why does the OP feel the need to rebuild the engine? Did it throw a rod through the block? Does it burn a quart of oil per tank of gas? Or does he simply perceive that it's worn out because it's slow because it's a truck?
     
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  8. Schurkey

    Schurkey I'm Awesome

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    I have a 305 in a '77 Nova. About 55K miles on it. Mom bought the car new in the fall of '76.

    The cruise control drops speed, and has to recover, EVERY time the CCOT A/C compressor kicks on, at highway speed. Put another way: The engine doesn't have enough power to go 60 mph AND run the A-6 compressor, without yanking the throttle farther open.

    305s are turds no matter what vehicle they're in.
     
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  9. L31MaxExpress

    L31MaxExpress I'm Awesome

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    Never felt the 601 head 305 in my old G20 was a turd even in stock form. Even turning the factory A6 compressor it had no problem cruising 90+ MPH. It ran alot better than the sawed off quadrajet 2bbl fed 882 smogger head 350 in my 1980 C10. The van had a 700r4 and 3.08 gears. The C10 had a 3 on the tree and 3.08s. The van would easily outrun the truck stock for stock. The G20 had over 200K on it and the C10 around 120K too at that time. The truck had a 2 cylinder York compressor on it. Zero acceleration when the a/c was on. The 350 would struggle to turn 3,000 rpm.
     
  10. Hipster

    Hipster I'm Awesome

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    An 8.5cr(maybe) 80's truck 76cc open chamber headed smogger engine that is leaps and bounds behind the later model 305 with tight chamber heads is what you use for a comparasion and justification? They had just about the same hp/tq ratings. Lets not forget the low 1st in a 700 for seat of the pants feel.

    You're really reaching on this one. Holy smokes man. Comparing it to the worst 350's Chevy ever built.
     
    Last edited: Jun 8, 2020

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