I searched....nada.....

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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a lot of people use 317 heads to drop their compression

 

West Coast Cylinder Heads sells Edelbrock cnc ported 245cc heads which are thicker deck castings than stock. You can get them with 74cc combustion chambers. Those have the largest combustion chambers that I know of. There's not a lot of information or reviews on them out there but the few guys that I've read about using them liked them. I was gonna get a set before I decided to swap pistons to lower my compression. Hope this helps.

 

I read where the Pro Comps had a .500 deck thickness here a few years ago. I know people have their opinions but they have a 70cc chamber available and if the deck is that thick and the aluminum alloy they used for casting is OK, why not.

 

The WCC edelbrock 245 as mentioned are great heads. If I remember right deck thickness is 5/8th and you can get them in 74cc. I run them but with 64cc chambers and they have been great and make great power.

 

I have a set of Trick Flow 225 CNC heads that came from TEA with the optional 70cc chamber, if I remember right they have a 5/8" thick deck. I also have a set of World Warhawk as cast 235 heads with a 72cc chamber. These have a 3/4" thick deck. While the Warhawks don't have the flow of the Trick Flows they are can be found for a less money if budget is the primary issue. I have half the money in those compared to the Trick flows.

 

Air Flow Research 245's have heads with 73cc chambers & .750" decks

 

So is there a calculator I can use to see what my compression will be with different chambers, gaskets, pistons, etc...?

73cc AFR 225's might drop my cr enough......

I will hate having to do a piston change.....

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Whats the chamber size on the 317 heads...?

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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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You can keep your heads if converting to e85

 

My current heads are old 1997-1998 LS1 ported heads. flow 304cfm@.650....they are terrible.

Don't I need a thicker deck for 19-20 psi.....

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http://www.csgnetwork.com/compcalc.html

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.

 

In that case I'd go to stock/ported 317s, cost effective and works very well, plus a ls9 headgasket and arp/china studs and boost 20# all day.

 

I've been using this site for years

http://www.bgsoflex.com/auto.html

Some really good programs, very helpful.

Good luck.

 

Do the 317s have a thicker deck too.......?
What intakes can be used with the 317s....?

Im just planning a single PT88 on my 390ci.......


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Only info I do not know is "Deck Height".........I entered zero.

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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Assuming your engine is in fact 0 decked, 10.4:1 compression is not bad on e85. Should make for a peppy engine out of boost and help with spool time on a big single setup. Just make sure you feed it plenty of fuel and as with any boosted engine, the tune needs to be right.

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.

 

EDIT: AES just emailed me back and said my deck height is.... 9.225

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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You didn't get a build sheet with the new motor? If not just ask AES for the full build sheet. Assuming they still have your detailed info on file.