Help with compression and head choice
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Teching In
Joined: Apr 2021
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Help with compression and head choice So I bought a junkyard lq4 and decided to rebuild it. I ordered flattop pistons to essentially build a lq9. I took the 317 heads in to get a port job and they found cracks between the valves on 6 of the 8 cyl. My goal was 650ish with a single turbo
I have the tbss/nnbs intake, 218/227 112+2, .600/.600 Lift truck cam, pac 1218 behive springs, Holley terminator x, all the bearings/gaskets/rings/pistons to rebuild it engine
I need new heads, will have to stick with cathedral to match the intake. Worried about chamber size and compression
I only have access to 91 octane (no e85) but I live at 6700ft, which I have read decreases chance of pre detonation.
I'd like to stay under $1200 for the pair. I'm kinda lost. Should I scrap the turbo idea?
I have the tbss/nnbs intake, 218/227 112+2, .600/.600 Lift truck cam, pac 1218 behive springs, Holley terminator x, all the bearings/gaskets/rings/pistons to rebuild it engine
I need new heads, will have to stick with cathedral to match the intake. Worried about chamber size and compression
I only have access to 91 octane (no e85) but I live at 6700ft, which I have read decreases chance of pre detonation.
I'd like to stay under $1200 for the pair. I'm kinda lost. Should I scrap the turbo idea?
799/243s ported, could be done in that price range, maybe a little more. A very good head as cast. No, stay with the turbo, why scrap that idea? A 7875 with billet wheel off eBay would work if you’re on a budget for the power level you’re wanting. Maybe an S480 if you’re really wanting more.
Thread Starter
Teching In
Joined: Apr 2021
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799/243s ported, could be done in that price range, maybe a little more. A very good head as cast. No, stay with the turbo, why scrap that idea? A 7875 with billet wheel off eBay would work if you’re on a budget for the power level you’re wanting. Maybe an S480 if you’re really wanting more.
To get a real accurate static compression number you’d have to know the head gasket you’re going to use, like compressed thickness, bore diameter of gasket, how far out or down the pistons are at TDC, buying flat tops before you figure what you need to get about 10:1 scr might have been your first gaff. You’ll need to cc the heads you plan on using, you can add a slight amount of volume to your C chambers by unshrouding and softening the chambers but that is for your porter to do. There are many free to use compression calculators online like Summit racing’s. Tuning, timing and fuel choice will dictate how much boost, start conservative then add.
Thread Starter
Teching In
Joined: Apr 2021
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Yeah had I known then what I know now, I would have done a lot of things different. It's been a frustrating 5 months with not being able to get parts at all and ordering wrong parts. I've been trying to do as much research as possible but still get kicked in the junk haha.
The head gaskets came in the rebuild kit from ws6store. So maybe I can contact them and hopefully get the spec's. I would assume that they are super close to whatever the oem was.
The head gaskets came in the rebuild kit from ws6store. So maybe I can contact them and hopefully get the spec's. I would assume that they are super close to whatever the oem was.
Joined: Jul 2007
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From: ELSA, South TEXAS (956) 802-7700
Seems your concern is available octane and not wanting to risk having detonation, and your desire to go turbo. Just get another set of 317s to keep compression slightly above 10 as originally intended. 317s cost less than 243/799s, and proceed with turbo build.
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Thread Starter
Teching In
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Yeah I think that's what I'm gonna do. Where's the best place to find some? I looked on ebay and found a new set for 670 but the reviews are not so good for the place.
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Verdad Gallardo Joined: Jul 2007
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From: ELSA, South TEXAS (956) 802-7700
Thread Starter
Teching In
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Sadly I'm in the middle of nowhere. I had to drive 3.5 hours to take the heads to the place that was gonna do the valve job. No junkyards within 3.5hr drive. So it will have to be mail ordered. Sucks because pictures only show so much.
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Under 1200 will be tough if you need heads. So here is what I would do of this has to be the budget. Scrap the turbo for now, buy some AFR enforcer heads. See what they can do for chamber size. Save up and get the turbo later. Done
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The 1200 is just for heads. The chambers on the enforcers are on the smaller side and would raise the compression more. But I was looking at those initially. The seem really decent especially for the price.
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Thread Starter
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Those are sweet but out of my price range right now. I do believe in buy once cry once. Just not sure if the juice is worth the squeeze for my build. I may be wrong