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Old 04-18-2004, 01:53 PM
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305 heads on a 350

Good afternoon everyone

I just bought a set of heads from a 305 HO. They have been modified with a set of 2.02 and 1.6 valves. I am putting them on a 350 sbc. they have be measured to 62cc, I was wondering what compression ratio this would produce.

The 350 is a mystery, numbers can't be read but I was told it was an early 80's block with a slightly hotter cam.

Has anyone else tried the larger valves in the 305 heads. The numbers are 1404116.

thanks in advance for any feed back.

cheer

84stepside

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Old 04-18-2004, 02:43 PM
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If the chambers were not deshrouded when the bigger valves were installed, the heads will flow less with the bigger valves than they did with the smaller valves. they do have fair sized ports, but they are some what known to be crack prone, so if they were not checked for cracks they need to be. Compression ratio will be higher with the smaller chambers, but it also depends on what kind of pistons your running, if there flat top pistons compression will be too high and the engine will detonate itself to death in real short order on pump gas, if there dish top pistons you can scrape by on pump gas if you keep a close eye on spark timing. I would have the chambers deshrouded if they have not been done so already to at least get some benefit from the larger valves, this will also open up the chamber size and help lower the compression ratio some to be more liveable on pump gas.
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Old 04-18-2004, 02:44 PM
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you'll want to port the the heads considerably to make having large valves worth while. Sounds like you'll end up with a nice set of heads! With flat top pistons you should make about 11:1 with a .041/4.166" gasket, decked to 0.

K
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Old 04-18-2004, 04:06 PM
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-- Killer formula and double vision

Are you sure about the CR. I was hoping for about 9.8 to 1 or there about.

Looking at the area around the 2.02 valve there has been some area remove to allow the valve to run. I was told that the cc was increased from 58 to 62.

What do you mean by "deshrouded". (is this the area behind the valve to allow for more air flow). Or are you talking about the actual ports being cleaned up to match for the headers.

I know the basic's of an engine but have never done a complete rebuild of a sbc on my own. So I appoligize in advance for some of the questions.

The 350 is running flat top pistons, I was hoping to be able to run 91 Octane gas from Mohawk stations (ethanol mix) without detonation problems. Am I out to lunch (dreaming)??

Thanks for your responses

84stepside
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Old 04-18-2004, 05:20 PM
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well, i used the chamber you said, a 350 standard bore motor decked to zero and the felpro gasket I mentioned. If you want less use dish pistons.

K
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