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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 75 C20 on December 27, 2006, 07:16:00 PM
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how hard will it be to port-polish my orginal heads on my 75 c20 with a 350. how long should it take me to do.-how much u think i would spend on doin it. i already got the engine pulled out soooo.... the valve seals are gittin a liltle bit bad cuz she smokes a lillte bit once inawhile when u first start her up.- and i figured it be cheaper to rebuild my stock ones cuz i cant afford new fancy nice heads.
thanks for the advice Edited by: 75 C20 at: 12/27/06 7:19 pm
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How hard depends on how skilled and steady handed you are. Porting & polishing should be done after the heads are stripped. Enlarging the ports and keeping tight smooth radius' will allow higher volume and create a velocity increase in flow. It is very time consuming to do it right and if you don't have a steady hand it can cost you a lot of money to fix or just end up ruining a cylinder head. Stay steadily away from the valve seats. One nick and you're all done. Remove any burrs or casting flash and take your sweet time.
As far as reconditioning the heads, clean them and decarbonize them thoroughly, check them for warpage with a precision straight edge, check the valve stems for wear and the margin. Check the valve guides for wear and look for cracks. If everything checks out ok now's the time to grind the valves and the seats. Check your spring installed height and if you are changing your camshaft make sure the springs you are using are compatible with the cam. If you ever plan on using roller rockers now is also a good time to fit the heads with screw in studs and guide plates.
As far as valve seals go, I prefer the positive seals over umbrella seals. If you don't have any equipment to do this stuff it might be more cost effective to have a machine shop do it for you or maybe a tech school.
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You would be way ahead to just go and buy a new set of Vortec heads about $540. ready to bolt on.You would need a intake for those also.$130.
Rockers and center bolt valve pans too.
Steve