Thicker deck heads...biggest chambers.....????
I need to know what heads.....with a thicker deck....have the largest chambers.?
For use with my LQ9 390ci.....4.030" bore.
My current heads chambers are at 65cc......
I'm at 10.8:1 cr with flat top pistons. I need to drop my compression down to 10:1 or lower if possible. I want to use 93 octane........or full time E85 if I have to.
Or...which thicker deck heads can have their chambers opened up enough to drop my compression.
Mid Frame T4 PT88 4" DP bumper exit....Huron Speed Single A/C kit is what I want to use.
Thanks..
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Last edited by ondatrack; Mar 14, 2015 at 06:21 PM.
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73cc AFR 225's might drop my cr enough......
I will hate having to do a piston change.....
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Edelbrocks are big money.....right....?
edit: I see....$2,340 for the 245cc Edelbrocks. 74cc chambers.
74cc should be plenty to drop my cr to 10:1 or a little lower.......NO...?
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Last edited by LS6427; Mar 15, 2015 at 01:26 PM.
Don't I need a thicker deck for 19-20 psi.....
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That's the calculator i use to figure compression. I would need to have more specs on your engine to accurately calculate your static compression ratio. I hope that link works as I'm on my phone at the moment. Changing your head gasket thickness can lower your compression as well but it's kind of bandaiding the problem.
Don't I need a thicker deck for 19-20 psi.....
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http://www.bgsoflex.com/auto.html
Some really good programs, very helpful.
Good luck.
What intakes can be used with the 317s....?
Im just planning a single PT88 on my 390ci.......
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That's the calculator i use to figure compression. I would need to have more specs on your engine to accurately calculate your static compression ratio. I hope that link works as I'm on my phone at the moment. Changing your head gasket thickness can lower your compression as well but it's kind of bandaiding the problem.
flat top pistons
3.825" crank
4.030" bore
.051 LS9 gasket
74cc AFR 245cc heads
0 Deck Height
Calculator says 10.4:1
I don't want to bandaid anything.
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Last edited by LS6427; Mar 16, 2015 at 03:26 PM.
Any cathedral port intake can be used with 317 heads. Of course you will have to recalculate your compression since 317 heads have I believe 71 or 72 cc chambers.
I would also suggest contacting one of the cam gurus such as Martin@Tick or Lil John and telling them your goals and specific application. While your static compression ratio is important, your dynamic compression comes into play as well and can be altered by cam choice. This can make a higher compression engine safer on lower than race grade fuels by manipulation of valve events.
I highly recommend getting with one of these guys or a cam guru of your choice and discussing your goals and expectations before you make any moves as far as purchasing parts. Good luck man.
Any cathedral port intake can be used with 317 heads. Of course you will have to recalculate your compression since 317 heads have I believe 71 or 72 cc chambers.
I would also suggest contacting one of the cam gurus such as Martin@Tick or Lil John and telling them your goals and specific application. While your static compression ratio is important, your dynamic compression comes into play as well and can be altered by cam choice. This can make a higher compression engine safer on lower than race grade fuels by manipulation of valve events.
I highly recommend getting with one of these guys or a cam guru of your choice and discussing your goals and expectations before you make any moves as far as purchasing parts. Good luck man.
I'll probably go with the AFR 245cc 74cc chambered heads.
I guess I'll have to ask AES what the deck height is on their 390ci's......
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Last edited by LS6427; Mar 17, 2015 at 09:57 AM.





