What size of heads?

[jusbus09]

I am looking for some dart heads or any other aftermarket heads to put on my chevy 383 that will go on my off road project. I want my motor to have around 9.5 to 1 compression ratio so i can run the motor on pump gas. That way if i am in mexico i can run on pemex if i have to. I have flat top pistons so i need help from some mechanics as to what cc of head i need, and what port volume i will need to get the correct compression ratio for my application.

[jusbus09]

Come on somebody on here has to know something that can help me out!!!

[lowdownndirty]

port volume = air flow....depending on where you want to make power will determine what size you want/need.....just as a guess with a reliable 383 195 range will do good
just off idle - 5500-6,000 rpm

combustion chamber size will be part of what determines your static comp. ratio.

what your deck height, are your pistons 2 or 4 valve relives or true flat tops,what heads gasket are you going to run,what`s the compressed thickness?

just a guess, here I`d say 74 cc`s would be best to keep a lower comp ratio 9-9.5:1

[richcomstock]

Find the part number on the pistons you are using. Most manufacturs will have reference charts relating the pistons, cumbustion chamber size, and compresion ratios.

[BTF Fabrication]

Your cc should probably be closer to a 67cc.usually a 64 cc w/ a flat top will be around 10:1.And you can get the DART sportsman's in a 67cc.

[lowdownndirty]

BTF good catch,

I only added in for 2 valve relief pistions, with a 4cc per relief(8 cc total) .032 head gasket and .020 deck height and 74cc chamber`s for a static ratio of 9.44:1

.032 gasket,.020 deck, 4 valve relief 4cc per,(16cc total) 74cc chambers would be a sick 8.77:1......

same as above with but with 67cc chambers 9.35:1

disclamier...4cc per valve relief was just a general guess to just get a est guess.

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Like said before, left out way to many varances to make a ACCURATE guess

[jusbus09]

Wow thanks for all the help guys. I know i have 2 valve relieve pistons, i dont know my deck height, and i am just using stock gm head gaskets. But at least i have a guestimate of what type heads i should use. I just dont want to get the compression ratio to high where i have to run high octane gas. Are those sportsman heads any good as compared to the other heads dart makes? Thanks again to all for chiming in.

[Chris_Wilson]

74cc chambers would be a sick 8.77:1......



Here's a 408 EFI Chevy, 560hp on 87 octane with 8.65:1 CR:

http://www.compcams.com/Community/Articles/Details.asp?ID=2041817420

[Stephen]

My 383 used the dart sportsman 200's with 64 cc chambers (with a little smoothing work to add some volume) and flat top pistons and it ran OK on 85 octane up here at a mile+ elevation. I did get some rattle with the torque convertor locked at high load and low RPM and especially at lower elevations. It used a 270 degree solid cam and sea level #'s were about 415 hp and torque. It had the short 400 rods. It had good low end torque and was pretty usable all around but really turned on around 2500rpm. I've often thought that breathing system would be better suited to a 406.

[BTF Fabrication]

Wow thanks for all the help guys. I know i have 2 valve relieve pistons, i dont know my deck height, and i am just using stock gm head gaskets. But at least i have a guestimate of what type heads i should use. I just dont want to get the compression ratio to high where i have to run high octane gas. Are those sportsman heads any good as compared to the other heads dart makes? Thanks again to all for chiming in.



The sportsman heads are just a steel counterpart of the aluminum heads.They flow just the same and are a very nice head.

[Dezertpilot]

That "Cheap Date 408" would be one super nice Mexico prerunner motor JEEZ!

[Chris_Wilson]

I'm building a Ford version for my bronco. Should have 500hp on 86/87 octane. Won't be snappy like my Leon Patten prerun motor in my F150 but hey, at least I can fill it up in Valle T.