Shenlon

iTrader: (4)

Hello everyone, I'm in the process of researching a future build to replace my current LS1. I've done a ton of reading up on the various cathedral head ports and rectangular ports and it seems like the experts have really determined how to make each one sing. My question is, for a bigger displacement motor, which is better?

I'm guessing from what I've been reading that the rectangular ports will perform better on a larger bore since that's what does well for the LS7, and I haven't completely decided what my bore/stroke will be for the engine I have built.

So, can someone break down where each head really shines, if it makes any difference at all?

For the purposes of this thread, the engine can be assumed to be in the 427+CID build range, and budget is not really a significant factor if that makes any difference.

Stage7

iTrader: (1)

I know it's not the answer you are looking for in this thread, but your best bet is to either email Erik@ HKE or email or call Shawn @ Va Speed to discuss your build. There are a lot of variables, and truly with the right combo, any of the big cathedral, ls7, or even l92 heads can be your answer.

What is the primary intended usage of the motor? What are the priorities of the build? Reliable, tame idle, broad torque curve, pump gas? Or race, max effort, could care less about idle, peaky power curve? Does the manifold need to clear a low cowl and hood, or are you flexible. You said your budget is flexible, so if you enlist the right builder and are clear with your goals and application you should be happy.

A big motor needs to breath, so focus on your attention on the Mast/PI cathedral or square port ls7 or l92, largest baddest TFS heads, etc out there.

Your engine builder will tell you which one is the best for your goals and specific build, but you won't go wrong with any of the ones in my post. This is of course assuming you are planning to use a builder vs. building it yourself.

Shenlon

iTrader: (4)

I will most likely be going through a builder, and I definitely intend to call one and discuss exactly what I want. I love researching these types of things though, and I've literally spent hours on end reading through threads here and have never seen this specific issue addressed so I was just hoping someone could give a good run down of the advantages of one vs the other.

I have seen lots of builds that perform very well using both styles, but haven't been able to really pick apart any specific trends regarding one style over the other due to the overwhelming array of other factors that can greatly influence a motor's performance.

I guess I worded my original post poorly, but I hope my objective is a little more clear now. Thanks for anyone that can help answer.

ringram

later model heads move air with a smaller cam for better emissions and driveability than the cathedrals stock for stock.

Stage7

iTrader: (1)

I agree, and to add to that, the cathedrals seem to have a more mid range torque stock to stock.

Somewhat of an exception or at least an asterik to the later model heads comment is the large bore 275cc Mast/PI cathedral heads. They seem to not need as much cam as the smaller runner cathedrals.

Advanced Induction

iTrader: (2)

Shenlon,

Of paramount importance would be your desired operating range, and power requirement. When I say operating range I don't necessarily mean 2-7k, since drivability is obviously a requirement. I am referring to the RPM range you'll usually be in when out enjoying the car. On 427cid+ you could build anywhere from 500-600rwhp w/ a moderately sized/priced head like GM LS3's or a good cathedral. You can also easily get into the 600-700rwhp range w/ a little hotter setup that still drives well for a bit more.

Sounds fun, good luck with your project!

-Phil

BigRich954RR

iTrader: (1)

Ok for most hp go with the super slick brand new canted heads.
Next one in cost range is the Ls7 style good for lots of power and over all great head but little more money.
Then i say go with a cathedral head make great tq and can still make alot of top end power

rem308winvtr

iTrader: (24)

ls7 head or a trick flow 245 or bigger