hthomasd

Hey everyone!

In case you didn't see my intro thread, I'm new to the lsx world and have so many questions. I've been reading all that I can and this is what I've got so far.

The 5.3l motor is going in an rx7. The car will not be driven daily and I want to hurt some feelings. The car however will be a street car.

The motor is stripped down and I'm ready to get into the motor and this is where my first questions come in. I've got a cam picked out. The cam is a comp cams 281/283 571/573 lift. The heads are the stock 862 casting heads. I'm sure it goes without saying that I need to ditch those heads and find a set of 243/799 heads and go from there? Or have I already started wrong and need to pick a cam that will work around a solid head choice?

Take it easy on me people....

conan

iTrader: (5)

Welcome.

Are there any different specs on that cam ? 281/283 ?

243/799 is a good head choice, I would at least have them milled and run a thinner gasket to bump the compression up some.

Are you doing anything with the bottom end ? Is this a LM7 - 5.3L with a dished piston ?

Mercier

iTrader: (15)

What's your budget? 862s are great with some work. Most factory heads, ported well, can end up to in the same flow neighborhood. What I'm saying is if porting is in the future, might be worth considering saving your $ on the 243s and get the 862s worked with a 2" intake valve. Smaller combustion chambers already(smaller than even the 243 by a bit) and can be milled further.

hthomasd

This is the cam. http://www.summitracing.com/parts/cc...8-11/overview/

I was not planning on doing anything bottom end yet. It is an Lm7 from a 2003 Silverado.

Budget is pretty open. I started to look into working the 862's but some people suggested its not worth the money and to get a set of 243's. But what you're saying makes sense.

Fry_

Define pretty open? For about $3k you could build that motor into a forged 383.

hthomasd

Sorry, pretty open on heads. Basically, is it worth it to spend $1000 to have the 862's port and polished, milled, and rocker work needed to get good power with that cam? Or should I not waste my money on the 862's and invest the money into a set of 243/799?

I had read an article with a test of that cam, worked 862 heads and a FAST intake manifold. They were able to make a little over 400hp at the crank. That's where I was headed.

Mercier

iTrader: (15)

http://elliottsportworks.com/?page_id=59
That's what I would do with a set of 862s. Cam, 2" valves, double springs included. IMO once you port and 2" valve 862s, a set of ported 243s isn't much different but you start with $300 more in the original heads. Your LM7 wont handle larger than 2" intake, BTW.
400 crank HP seems a little low for aftermarket cam, intake and worked heads. See this article for crank numbers with stock GM cams.
http://www.hotrod.com/how-to/engine/...st-comparison/