Author Topic: "rebuilt" 350  (Read 566 times)

Offline Tegra1027

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  • Newbie
"rebuilt" 350
« on: August 17, 2018, 07:39:42 PM »
Hey everyone. I just picked up an 85 c10 with a 305. I believe the engine is out of something a bit newer. The whole front main seal is just RTV basically.

I also have a 350 which is sitting in an 80 k20 farm truck. This engine supposedly had a fresh rebuild right before it sat. At this point it has been sitting for 10+ years. What should/can I do to see the condition of this engine and make sure it will be a good swap for my C10? TIA

Offline 75gmck25

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  • Posts: 423
  • 1975 GMC K25 Camper Special, 350/TH350/NP203
Re: "rebuilt" 350
« Reply #1 on: August 18, 2018, 06:20:07 AM »
Pull the plugs on the 350 and put a few squirts of penetrating oil in each cylinder, then turn it over by the balancer center bolt.  However, don't get carried away and break anything.  If it does not turn over easily, the pistons may be rusted to the cylinders.

If it does turn over freely, then pull the valve covers and get the numbers off the heads and the numbers off the block pad.  There are many sources online to look up the numbers and verify what you have.

Its probably a basic 350 with smog heads and low compression, which means about 210-220 HP at best.  However, that engine is the starting point for most builds, and it works fine for a daily driver.  Adding a new dual plane manifold, good carburetor and headers will bring it up to about 240-250 HP, and swapping in an RV cam will get you another 25-30 HP.   At that point you really need better heads and more compression, so further mods get much more expensive.