Ported heads = a no no

[Dominic]

Unless you're going forced induction I propose ported/polished heads are a no-no for our 350-400cfm injesting engines. Want to read why?

Here's one article for you:

http://www.superflow.com/support/sup...efficiency.htm

[pgriffith]

Oh crap. Now I have to buy a turbo! ;)

[WickEdSix9838]

porting the heads is where you will get the biggest gain for NA HP, the article is talking about how to port them, when you port a set of heads you want to keep the port small as you can yet flow as much air as possible, so you keep the velocity up in the ports, how big you port the heads to depends on the size of the motor and how may RPM's it will be turned...

[ September 15, 2002: Message edited by: WickEdSix9838 ]</p>

[Dominic]

It just seems to me nobody has done any dyno runs using a cam with before/after head porting to show that its even worth while on our cars.

[WickEdSix9838]

porting the stock heads probably wont yield as much gain as would porting an aftermarket head because the castings are real thin and you cannot pull enough metal out to make the heads as mean as they could be because you will hit water...

[Skinny]

<blockquote>quote:</font><hr>Originally posted by Dominic:
It just seems to me nobody has done any dyno runs using a cam with before/after head porting to show that its even worth while on our cars.<hr></blockquote>

RiceCooker did. Before he pulled 16X-something at the wheels. After he pulled 200 at the wheels with the Supersix package.

I agree that heads can be "over-ported" even for a forced induction car. See this article from GMHTP which talks about porting the heads on a turbo Buick engine.

[Dominic]

Ricecooker did a stock to supersix package dyno comparison. He did not just simply slide in the cam and dyno, then install the heads and redyno to see if it was worthwhile.

I quote from 3800performance (who is not necessarily right) "We have now studied and flow-bench tested more than a dozen different 3800 Series II head porting designs, and are convinced our Stage 2 heads will outperform any other heads on the market retaining stock valves.

These 3800 Series II cylinder heads are now available for L67 engines. The same work could actually be performed on L36 cylinder heads, but our testing shows gains of almost zero for L36 engines with less than approximately 300 crankshaft horsepower."

In order to make more than 300 crankshaft horsepower from one of these engines you need forced induction or a higher redline. The redline is governed by the harmonic balancing of the engine, PCM, components, fuel, etc and is not an easy thing to raise - so I won't even go there.