Lm7 flat tops
12-08-2016, 10:30 AM
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Lm7 flat tops
99 lm7 with 4.8 pistons. Wanting to bump the compression a little more by milling the heads but worried about valve/piston clearance with a bigger cam. Haven't decided on a cam yet because Im worried about the the combination of how much to have milled, what gaskets to run, and lobe lift. Anyone have any experience with this?
12-08-2016, 08:26 PM
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Any idea what a good cam would be? around 11:1 compression, 93 octane.
Also, how much milling would have to/ can be done to get it close to 11:1 with flat tops?
Also, how much milling would have to/ can be done to get it close to 11:1 with flat tops?
12-09-2016, 11:25 PM
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Also watch your Dynamic Compression Ratio. Most people over look that and it can cause detonation. Stay under 8.5:1 with 91/93 on Dynamic Compression. The cam will be the biggest factor for that. Also keep your Quench in the ideal range, around .035" is ideal and do not go under .030", you can get closer to .030" with an iron block and I would stay around .035" with an aluminum block. I will be running a BTR Truck Stage 2 212/218 and PRC Stage 1 Ported heads. I milled the heads to 63cc and will be using a .045" Cometic head gasket. That puts me at 10.5:1 Static Compression, 8.5:1 Dynamic Compression and my Quench is at .038". Which is ideal for 91/93 Octane. The closer you can get to .035" Quench the less change of detonation.
As 1FastBrick said, you also need to know how far out the piston is, most are around (-.003")-(-.008"). Mine is -.007". Look into some the the online Dynamic and Static Compression ratio calculators and mess around with them a bit. You will also need some certain cam specs as well to use it. Just my thoughts and opinion.
As 1FastBrick said, you also need to know how far out the piston is, most are around (-.003")-(-.008"). Mine is -.007". Look into some the the online Dynamic and Static Compression ratio calculators and mess around with them a bit. You will also need some certain cam specs as well to use it. Just my thoughts and opinion.
12-09-2016, 11:39 PM
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That is my biggest issue, understanding all the combinations and how they work together. I was thinking with the right combo i should be able to get close to 400horse at the flywheel?