408 guys, what CR are you runing?
10-30-2006, 05:35 PM
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408 guys, what CR are you runing? What compression ratio are you guys building your 408's to? Ive done some shopping around for parts and keep coming at 8.5:1-9.25:1. Having trouble finding dish pistons with -16 to -24 cc dishes, and am considering a 9:1 CR build so I can leave my options for FI open later on. What are most of yall doing for buildups?
-Lurius
-Lurius
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10-30-2006, 06:29 PM
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Any of yall running nitrous? I want to keep my nitrous after I install the new motor, but keep hearing mixed opinions on the matter. Some are saying I should use flat top pistons if I am going to use nitrous, others say it dosent matter.. then theres some saying to go with 9:1 CR if I want to use around a 150 shot.. What do yall think?
-Lurius
-Lurius
10-30-2006, 06:58 PM
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I built a 408 for a buddy which we used the -12cc Mahle's and lq9 heads, its around 10:1 and he is currently spraying a 150 shot on it. That's at 24* of timing to be safe and 11.7~11.8 A/F at WOT with the juice. The Mahles are good for a 200 shot I believe. We run about 27* timing on just motor only. This is in a fullsize Silverado pickup, and the cam is a 233/239 TSP. I know thats not a lot for a 408 but it helps get that heavy truck movin good.
10-30-2006, 07:01 PM
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Originally Posted by Rhino79
I built a 408 for a buddy which we used the -12cc Mahle's and lq9 heads, its around 10:1 and he is currently spraying a 150 shot on it. That's at 24* of timing to be safe and 11.7~11.8 A/F at WOT with the juice. The Mahles are good for a 200 shot I believe. We run about 27* timing on just motor only. This is in a fullsize Silverado pickup, and the cam is a 233/239 TSP. I know thats not a lot for a 408 but it helps get that heavy truck movin good.
So your buddies engines holding up with that 150 shot and 10:1? No regrets on it? Would you change anything about the buildup or is it great the way it is?
-Lurius
10-30-2006, 07:11 PM
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Originally Posted by Lurius
Thats really helkpful info there. This is going in a FS pickup as well. Im going with an even more tame cam, a 224 or 228 likely. This is a daily driver, so I am trying to build it first as a reliable powerhouse, and 2nd as a good fun race engine. Not trying to beat any records, just something to have a lot of fun with at the track while still being able to drive it to work. So no race gas lol. 10:1 is what I had considered first off because its the stock CR for the lq9 motor, and im running a 93 octane tune anyways with my 5.3L at 9.5:1 and figured I might as well increase compression on the 408 till I was told to go with lower for nitrous..
So your buddies engines holding up with that 150 shot and 10:1? No regrets on it? Would you change anything about the buildup or is it great the way it is?
-Lurius
So your buddies engines holding up with that 150 shot and 10:1? No regrets on it? Would you change anything about the buildup or is it great the way it is?
-Lurius
10-30-2006, 07:21 PM
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What size injectors are you running?If you are having fueling problems,you need to address the fuel pump and injectors,before changing your intake and throttle body setup.And I'm running 8.8:1 compression with my FI setup.
10-30-2006, 07:26 PM
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Originally Posted by whitt1
What size injectors are you running?If you are having fueling problems,you need to address the fuel pump and injectors,before changing your intake and throttle body setup.And I'm running 8.8:1 compression with my FI setup.
10-30-2006, 07:38 PM
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How high do want to rev your 408?I don't normally take mine past 6600rpm.The wall you are hitting may not be caused by your intake.Are your heads porting stock and what valvesprings are you running?
10-30-2006, 07:39 PM
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As for fuel in my case, I was looking at that 255lph in take kit and 8.1L injectors(I think they are 41lb?).
What are some of yall's bottem end setups for 408's around 9.5-10 to 1 CR?
Great info guys, keep it coming!
-Lurius
What are some of yall's bottem end setups for 408's around 9.5-10 to 1 CR?
Great info guys, keep it coming!
-Lurius