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Old 03-27-2012, 08:58 AM
Devin Devin is offline
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Random engine swap question

Soon after I graduate from college and move back to California, I am going to turn a 2007 scion tc into a rear wheel drive, drift toy. I know which rear end, and transmission I want to use; I'm just having a hard time making up my mind on the engine. I am contemplating an LS3 engine swap. I could also pop on a custom supercharger if I wanted to use the original engine.

The question that keeps popping up is this. Is there any real advantage to an engine which runs twin cams (DOHC) over a single cam set up with push-rods like the LS3? Can you please clarify this for me?

Either way the power plant in this car will be putting out at least 500hp. So, can anybody load me up with info?

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Old 03-27-2012, 10:24 AM
dougbfresh dougbfresh is offline
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Is there even enough room to put any of this is a (cough-cough) Scion? May as well get a Camaro and drive it. Overhead cam engines generally have less mass (no pushrods/rocker arms) so they tent not to float at high rpms like pushrod engines. BUT, I have not seen a factory DOHC motor put out the HP most LSx engines can.

Hope you know how to WELD/fabricate-you'll be doing a LOT on this conversion (still don't get why you would do this). There are guys all over the net with 4-500 hp on the factory boat anchor motor, probably takes some big RPM to get it. I guess you can't "Drift" in a FWD car so easily though.

Last edited by dougbfresh; 03-27-2012 at 03:49 PM.
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Old 03-28-2012, 11:38 PM
olddog olddog is offline
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Overhead cam engines are easier to build for high rpm use, than a push-rod engine. As Doug said a lot less mass. Also the 4 valve per cylinder heads are a superior design for air flow. Again the 4 valve is lighter, lending itself to higher rpm potential. The smaller area of the 4 valves is also less area per for pressure to work on in boosted and turbo charged (pressure of both exhaust and intake valves). So they are theoretically a better design for boost applications.

With that said they are physically bigger than there push-rod counter parts. They are a much harder to work on and more complicated design an many ways. Just because the engine can potentially rev higher without valve float issues, does not mean it can. For one, the bottom end on many of these engines will not withstand any more rpm than a typical push-rod engine. Secondly the valve springs are smaller and lighter and less strong, so the valve still float due to the weak springs.

As Doug said, the LS engines are making impressive power. In reality, it all depends on how the engine is built. Either design can be built to just about any Hp level and any rpm range, given enough money.

If you are trying to stuff a lot of power into a small space, go with a turbo and a smaller engine.

In a V-8, the 5.0 Ford is about the smallest and lightest, at 400 lb in all cast iron from the factory. You can build them out of all aluminum parts and cut 130 lb or so off of that. Turbos can push them over 1000 hp. You don't need that big of an engine. I would look at the 4 poppers or V-6 engines.
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