350 build.
07-23-2010, 11:13 AM
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350 build.
Just looking for peoples opinion and input,and guess onif any hp gain.I,m using a 1976 350 block.with stock marine cam.88-95 vortec heads.and used all old externals marine parts.started.alt etc.please feel free to input.
07-29-2010, 09:20 AM
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I'm doing a a vortec build right now myself based on a 78' merc 260 (chev 350). Remember you are going to need a new intake for the vortec heads and centerbolt valvecovers. There are several designs available I went with a Volvo/penta aluminum high rise but weiand has the stealth and Edelbrock has the Performer RPM in the vortec config. GMPP also has their high rise that looks to be the same as the Volvo version. I had to install .100 SHORTER pushrods to have correct valvetrain geometry. Jim Miller has an article on PROPERLY measuring and setting up valvetrain geometry, this is a critical and somewhat confusing step for a novice...I can email you the article if you would like. As for horsepower increases...with the vortec heads, stock compression, lets assume you go with the Weind Stealth...should be in the 290ish hp range.
07-30-2010, 10:09 AM
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Here's what I would do...
Sell the older block and replace it with a 1pc rear main seal block. The benefits are worth it (factory roller... cheap and easy valvetrain upgrades!... better sealing oil pan and crank seal, etc.).
If you have the means, go ahead and replace the rotating assembly with a Scat or Eagle FORGED rotating assembly (a cast crank will work, but there have been some issues with Eagle cast cranks breaking at the harmonic balancer). Keep compression under 9.5:1. Gas these days is CRAP! Don't go crazy with compression because the fuel will help to ruin a good engine. Vortec or Vortec-esque heads (GM, RHS, Edelbrock) would be great in this application especially if you choose a cam that works with the flow capabilities of the Vortec port (nothing much over .500 lift, etc.). Top it off with a Performer RPM AirGap or the like, a 750 Holley, and some GLM split-runner manifolds. Horsepower should be right around 450 with as much torque.
A similar built 350 would net you upwards of 380 to 400 horses. MKOS1980 over on Speedwake dyno'd his 260 short block equiped with Vortec heads and a GM LT4 "Hot" cam and got 380 HP out of it. That is on the STOCK short block! I have the same set up in mine (my 383 dropped a valve) and can't speak enough on how good of a combination it is.
Hope this helps.
Tom
Sell the older block and replace it with a 1pc rear main seal block. The benefits are worth it (factory roller... cheap and easy valvetrain upgrades!... better sealing oil pan and crank seal, etc.).
If you have the means, go ahead and replace the rotating assembly with a Scat or Eagle FORGED rotating assembly (a cast crank will work, but there have been some issues with Eagle cast cranks breaking at the harmonic balancer). Keep compression under 9.5:1. Gas these days is CRAP! Don't go crazy with compression because the fuel will help to ruin a good engine. Vortec or Vortec-esque heads (GM, RHS, Edelbrock) would be great in this application especially if you choose a cam that works with the flow capabilities of the Vortec port (nothing much over .500 lift, etc.). Top it off with a Performer RPM AirGap or the like, a 750 Holley, and some GLM split-runner manifolds. Horsepower should be right around 450 with as much torque.
A similar built 350 would net you upwards of 380 to 400 horses. MKOS1980 over on Speedwake dyno'd his 260 short block equiped with Vortec heads and a GM LT4 "Hot" cam and got 380 HP out of it. That is on the STOCK short block! I have the same set up in mine (my 383 dropped a valve) and can't speak enough on how good of a combination it is.
Hope this helps.
Tom
