243 or 706 heads? (LQ4 + Torque Cam + TBSS Intake)
01-22-2022, 11:54 PM
#61
01-26-2022, 10:12 AM
#62
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This is an oldie but a goodie. As @RedXray said this same setup wouldn't pose a PTV problem with the flat tops in your LQ9. Right around 5* Intake Valve Opening (IVO) @.050 is where we start recommending checking PTV clearance. That is with a flat-top piston, standard deck height, and un-milled heads. The now SUM-8720R1 has a -1* IVO so PTV won't be an issue.
With that being said something to think about is compression and octane. Going with 61cc 706/862 heads on your LQ9 would net around 11.4:1 compression. In a heavy truck that's going to basically take 87 octane out of the equation. You would need to run 93 all the time. If you planned on doing much towing or heavy hauling even with 93 the timing would need to be conservative. This is somewhere we would actually recommend going with 65cc 243's instead. At that point, you'd pretty much be in TBSS LS2 territory right around 10.9:1 compression. 87 could be used with conservative timing for daily use. 93 will need to be used for any hauling or towing. Even then you will need to pay close attention to data logs watching for knock.
Depending on what you're looking to do with the truck you could go larger on the cam. Red has a stout cam in his truck with a well-thought-out combo to go along with it. Take a look at his signature with all the other mods that go along with that cam. That's something to think about going with a larger cam. You can't just stab the biggest cam in there and run it. It's a domino effect that grows larger the bigger you go with the cam.
With that being said something to think about is compression and octane. Going with 61cc 706/862 heads on your LQ9 would net around 11.4:1 compression. In a heavy truck that's going to basically take 87 octane out of the equation. You would need to run 93 all the time. If you planned on doing much towing or heavy hauling even with 93 the timing would need to be conservative. This is somewhere we would actually recommend going with 65cc 243's instead. At that point, you'd pretty much be in TBSS LS2 territory right around 10.9:1 compression. 87 could be used with conservative timing for daily use. 93 will need to be used for any hauling or towing. Even then you will need to pay close attention to data logs watching for knock.
Depending on what you're looking to do with the truck you could go larger on the cam. Red has a stout cam in his truck with a well-thought-out combo to go along with it. Take a look at his signature with all the other mods that go along with that cam. That's something to think about going with a larger cam. You can't just stab the biggest cam in there and run it. It's a domino effect that grows larger the bigger you go with the cam.
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