Compression Help
Thread Starter
Launching!
Joined: Dec 2017
Posts: 245
Likes: 45
Compression Help Hey guys, I'm trying to figure out what is needed to reach my desired compression ratio so I can order head gaskets soon. I'd like to touch 11.0:1. Build is a general LS1, which I've read the general piston out of the hole is .006, but, I understand isn't always the case but I have no way of measuring. Cylinder heads are currently at Frankenstein for their stage 1 port work on my 243's. They will take off 0.010 for surfacing. Which puts them around 63cc (I think). Cam is a BTR Stage 2 LS3 225/238 .612/.585 113+3. Using the basic Summit Racing calculator it seems that using a .040 gasket and bringing the heads to 62cc will get me right to 10.98:1 if my deck clearance is at or close to 0.006. With the specs I've listed would this be safe along for my cam as well? If I decide to stick with the 63cc and 0.04 gasket I'm at 10.85 which doesn't seem too far off. Wold the extra CC off the heads make much difference in power? Any feedback is appreciated. Thanks
TECH Fanatic
Joined: Oct 2014
Posts: 1,220
Likes: 179
From: Virginia
You can play around with this to get an idea. Also, you can consider pistons with valve reliefs, or get a fly cutter to solve any PTV issues... I'm at 11.2:1, LS3. Got the heads off at the moment, considering more...
https://www.uempistons.com/index.php...tors&type=comp
https://www.uempistons.com/index.php...tors&type=comp
Thread Starter
Launching!
Joined: Dec 2017
Posts: 245
Likes: 45
Nice! I'm not sure if I want to go with an aftermarket piston at this time. Playing around with the Summit calculator, 3.898 bore, 3.622 stroke, 63cc head, flat tops, 0.006 deck clearance and a .040 gasket it shows 10.85 compression. Which I could have the heads milled to 61-62cc also, which is another option. Best around for me is 91 octane
TECH Fanatic
Joined: Oct 2014
Posts: 1,220
Likes: 179
From: Virginia
You can just retard the spark some to make up for the lack of octane. It really isn't a big change off of 93, honestly. Camshaft has much more to do with actual effective compression than anything though. You can get away with a little more timing depending on what cam you run. Just make sure you check that PTV.
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TECH Fanatic
Joined: Oct 2014
Posts: 1,220
Likes: 179
From: Virginia
Also, keep in mind compression causes heat, and the known weak point in an LS engine is the piston itself. I would recommend doing it right and getting some forged h-beams and pistons in there.
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Joined: Jan 2018
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From: Dade City, Fl.
Hi Sleeper, be careful with the thinner head gasket choice if you didn't measure piston out of the deck. .You could end up with not enough quench clearance. BTW...
what are the 243's head work gonna cost you? I contacted Frankenstein and they never got back with me. I ended up sending my 243's to Total Engine Airflow.
what are the 243's head work gonna cost you? I contacted Frankenstein and they never got back with me. I ended up sending my 243's to Total Engine Airflow.