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post #1 of (permalink) Old 01-16-2004, 07:25 PM
joblope
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305 heads for a 383

I can get higher compression heads to put on a 383 I'm building. I was told that they will bolt right on. But do the 305 heads have the same a/c bolting patter for a 350? Also, are the coolant holes from my block going to match the coolant holes on the heads? Are there disadvantages to running these heads on my truck? The valves are 1.84/1.50 valves. Is this adequate for a 383. They are coming off a Z28.

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post #2 of (permalink) Old 01-16-2004, 07:53 PM
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Re: 305 heads for a 383

They'll bolt on.

What are the casting numbers?

They do not flow well enough even for a 350. I would not even run them ported on a 350. Even my ported ones on my "mild" 305 are the bottleneck.

Chances are the chamber volume is too small unless you're going to run dish pistons.
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post #3 of (permalink) Old 01-16-2004, 09:02 PM
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Re: 305 heads for a 383

the casting number is 416. Couldn't I get some machine work done on them and put larger valves (1.94/1.60) in them to help flow better? They are 58cc.
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post #4 of (permalink) Old 01-17-2004, 10:43 AM
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Re: 305 heads for a 383

If you put 1.94 valves in the valves will be nearly touching. I don't believe you'd be able to get 1.60 valves to fit.

An extremely well ported 305 head flows what a mediocre 350 head does. A 305 head with 1.94 valves and well ported is supposed to compare to camel humps. You still aren't even coming close to what Vortecs or AFR 195s produce.

By the time you spend $100 to machine for new valves, $80 for a valve job, and $80 for new valves you'd been better off buying aftermarket heads. There are aftermarket heads in the Vortec head price range that you don't have to deal with all the install problems Vortec heads create.


So I take it there is some reason you want 11:1 compression in your 383?
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post #5 of (permalink) Old 01-17-2004, 02:17 PM
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Re: 305 heads for a 383

I was wanting a 9.5 or 10 compression ratio for the extra torque and hp. I'm reading a chevy performance book talking about how the higher compression heads are going to give more torque and hp. The book is talking about saying away from the lower compression heads (like 76 cc heads) used on smog regulated cars and trucks. I know that if I get too high of a compression, I can't use pump gas. I'm in the process of matching the cam, pistons, and heads so they all coincide. At least I'm taking my time so I don't screw anything up. Will vortec heads bolt on and have a the fitting holes for a 79 Blazer, or will I have to get a specific block for those heads?

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post #6 of (permalink) Old 01-17-2004, 05:18 PM
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Re: 305 heads for a 383

There are several options for heads for your 383. In my humble opinion, 9:1 compression is usually safe for 87 octane unleaded gas, except in hot weather of 100 degrees or so. In my humble opinion, building a daily street driven engine with a compression ratio more than 9:1 is not the best idea. [img]images/graemlins/frown.gif[/img] In my humble opinion, based on the dozens of Small Block Chevy engines I've built, the 76cc head is an excellent head to use on a 383 to keep the compression ratio close 9:1. The "Old School" on building a 1 horse power per cubic inch Small Block Chevy 350 included using flat top pistons, 2.02 / 1.60 76cc heads.
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post #7 of (permalink) Old 01-17-2004, 10:39 PM
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Re: 305 heads for a 383

wow! I looked up some information after reading your post, and it looks like if I go with 64cc heads or smaller, with my flat top pistons, I'm looking at a 11:1 compression ratio or higher. Does that sound right, and with that compression ratio, I'm starting to move out of the realm of pump gas, right? Thanks!
post #8 of (permalink) Old 01-17-2004, 11:50 PM
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Re: 305 heads for a 383

Check this link for a COMPRESSION RATIO CALCULATOR http://kb-silvolite.com/temp/calc.php
It's my humble opinion that a 383 should be built using Chevy 350 rods (5.7") long. With the 350 connecting rod I use Federal Mogul / Speed Pro pistons (part # H600P) when I build a 383. The H600P piston compression ration is about 9.2:1 with 76cc heads. Federal Mogul / Speed Pro piston (part # H602P) has a compression ratio of 8.65 with 76cc heads.
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post #9 of (permalink) Old 01-18-2004, 11:15 AM
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Re: 305 heads for a 383

</font><blockquote><font class="small">In reply to:</font><hr />
So I take it there is some reason you want 11:1 compression in your 383?

[/ QUOTE ]

Uh, duh. At 10:1 with cast iron heads you're going to be pushing it even with 94 octane Sunoco. If you polished the piss out of the combustion chamber to get rid of any heat concentrations then you could probably pull it off.

I don't think you comprehend flow. You'll make better horsepower with "crappy" 75+cc 350 heads with no porting than you will with the 1.94/1.50 machining you want to do along with porting those 305 heads.

Is there some reason why you're set on using these 305 heads on your 383?
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post #10 of (permalink) Old 01-18-2004, 11:51 AM
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Re: 305 heads for a 383

I'm not "set" on using 305 heads. I don't think I'm goign to get them, but I think up to a point, higher compression would mean more hp and torque. However, like you guys were saying, it would be very hard to put in larger valves in that head and flow would be terrible. What do you know about Vortech heads? Will my edelbrock intake fit onto Vortech heads? Also, it's driving me crazy trying to figure out what parts from certain years will fit with other parts. Is there a book that has interchangability of parts from different years?

Thanks
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