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Old 10-02-2010, 11:46 PM
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350 vortecs with 1.94 1.50 clear a 305

Will 906 Vortec heads from a 350 , have valve to cylinder wall clearance problems on a 305 ? The 1.94 valve sounds nice but will it fit the standard bore 305 ?

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Old 10-02-2010, 11:56 PM
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Never tried it, but I think I have read that it won't work. Even if there was no mechanical interference, the intake valve would be so close to the edge of the cylinder that it would screw up flow past the valve and I doubt in the end that you would gain anything. Ideally, you need 0.200" between the edge of the intake valve and the bore so that the slug can maintain its shape past the valve and into the cylinder without incurring turbulence.
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Old 10-03-2010, 01:35 AM
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You're also looking at a drop in C.R.
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Old 10-03-2010, 01:44 AM
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The will bolt on and clear, one of the magazines(Car Craft, Hot Rod, Chevy HiPerformance) used them right out of the box with a .025" flat mill job on their 400hp 305 build-up a year or so ago. They also used a .015" head gasket along with the mill job to keep from losing any compression, milling the heads got them down to 60cc from the stock 64cc, closer to the 305 stock 58cc.
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Old 10-03-2010, 11:23 AM
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Thanks.

The 305 has a 3.75" bore, and when that 1.94" valve opens , valve must get close to the wall. Although the 305 heads were supposedly 1.94/1.50 valved.

1.94 + 1.50 = 3.44 , there could be room ? The cant of the valves with only 1/2 inch of lift, could keep them from getting to the rim while maintaining flow .

Last edited by spinn; 10-03-2010 at 11:51 AM.
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Old 10-03-2010, 12:31 PM
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The won't quite flow as well as on a larger bore because of the bore shrouding, but they clear unless you get into monster solid roller cam type lifts. Even with the shrouding, you won't find a stock 305 head that flows better unless you do some porting on whatever 305 head you use.
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Old 10-03-2010, 02:01 PM
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Can 4.08" standard .39" head gaskets be used to install them ?

I want to do the vortec 305 upgrade on my 85 C10. The current setup is a performer cam/springs,manifold, and Qjet. 1900 stall and TH350 with 2.73 10 bolt rear. Can you offer an additional advice on the project?

Fall cleaning found me a some cleaned up 906 vortec heads .
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Old 10-03-2010, 03:04 PM
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Quote:
Originally Posted by spinn
Can 4.08" standard .39" head gaskets be used to install them ?

I want to do the vortec 305 upgrade on my 85 C10. The current setup is a performer cam/springs,manifold, and Qjet. 1900 stall and TH350 with 2.73 10 bolt rear. Can you offer an additional advice on the project?

Fall cleaning found me a some cleaned up 906 vortec heads .
Yes, you can use that gasket, but if the block hasn't been zero decked and it is combined with unmilled Vortecs 64cc chamber it will really kill the compression ratio badly, like 7.0-1 with stock flat top 305 pistons.
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Old 10-03-2010, 03:36 PM
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Unusual quoting. Makes no cents.

Nice to know they will fit.
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Old 10-07-2010, 06:40 PM
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From other, multiple, sources say they will not fit. The flame front will be altered do to shelfing. Bore shelfing is something negative about mating the 3.75" 305 block bore and the supposed 4.08" chambered vortec heads. One person replied claiming a 3 point drop in compression between 64cc and 58cc chambers ? That one escapes me as well. The machine shops claim any thing more than a .10-20" mill and the exhaust side casting will crack.

After hearing from this site , the heads got newish beehive springs and seals, and are prepped for installation. The vortec heads are looking back at me wondering the same. Does anybody know what they are talking about, definitively, there is no just jump ?

Found a ring pinion set of 4.56 gears for the 8.5" rear . If the trans gets upgraded to a 700r4 it is a go.
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Last edited by spinn; 10-07-2010 at 06:55 PM.
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