Why port factory heads?
Thread Starter
12 Second Club
Joined: Dec 2001
Posts: 931
Likes: 0
From: Santa Clarita, CA
Why port factory heads? I want my stock LS1 heads to flow as good if not better than the next guy, but here is my question: Why wouldn't GM produce the best following head straight out of the box? Lord knows they have the research and development budget to do so. What would be the rational to hold back on head flow? Was GM concerned with metal thickness in areas? looking at potential emissions ramifications or? or what? Were the LS1 heads Computer Numerically Controled machined to begin with, if so, why not go for max flow? I guess I am a bit confused as why 3rd party porter gains are to be had in this area, keeping valve size stock. Maybe these are stupid questions, but the reason I like this site is for the enlightenment.
Regards,
Regards,
Re: Why port factory heads? Because these cars are not soley dedicated to absolute performance like a Ferrari would be. What I mean by that is, that GM builds these cars for all kinds of customers, where as somebody like Ferrari knows that they only have to design a platform for one kind of market segment. GM sells these cars to anyone, that's why they have 2+2 seating, even though the backseat is useless for that. They are concerned with throttle response, and all types of parameters. Sure most of these cars will go to an enthusiast,but there are some that will go to some goof , that never maintains their car, and puts bad gas in it, or whatever. They also use a cylinder head design across many different lines, so they try to meet in the middle, and you wind up with a part that is not the best that it could be if it were designed for a single purpose.
Thread Starter
12 Second Club
Joined: Dec 2001
Posts: 931
Likes: 0
From: Santa Clarita, CA
Re: Why port factory heads? Thanks sawedoff for the response, but you get right to heart of what is perplexing me, in what way are they pacifing the average driver by holding back on head flow design. I don't understand the benefits.
Regards,
John
Regards,
John
Thread Starter
12 Second Club
Joined: Dec 2001
Posts: 931
Likes: 0
From: Santa Clarita, CA
Re: Why port factory heads? That's an interesting point chikin, I never thought of the aftermarket, and their needs. What is interesting is how GM, Ford, DaimlerChrysler, etc benefit from the aftermarket, besides creating a following for a particular vehicle (and potential future sales). Probably another thread in an of itself, but interesting nonetheless. As far as holding back on power, I'm not so sure these days, power is a pretty considerable selling point. I hope this new Dodge SRT-4 raises/holds the bar on what the public expects power to weight ratio from a 20K performance car.
Regards,
Regards,
TECH Fanatic
Joined: Nov 2002
Posts: 1,317
Likes: 0
From: metro st louis
Re: Why port factory heads? Chikn you have a really good point there. That really explains why it's hard to find a Grand National, Typhoon, or Syclone in bad shape, but I'm sure there some turds to be had. It also may explain why GM under rated the F-bodies with the only engine differences from the C5 being fly-by-wire and acc. placement.
TECH Addict
Joined: Dec 2001
Posts: 2,298
Likes: 2
From: new england
Re: Why port factory heads? If you study stock vs. modded head flow like i do, you will see that GM has port flow in lift ranges that stock cam sees are very good. most of porting gains are above the .470" valve lift point where stock cam never gets too. So they have a head design that serves very well with stock engine and programming package. Our unlimited performance needs are where porting and larger valves are needed to get best results.
TECH Veteran
Joined: Aug 2002
Posts: 4,055
Likes: 1
From: Hartsdale, NY
Re: Why port factory heads? GM will not max out the head design becasue they need to keep selling new cars.
When the volume sales for a particular year start to decline they will modify the motor to produce higher HP and everyone will won't a new car because it has more HP than last years' model...
The ZO6 was a classic example; the first model was 385HP now they are 405HP.
So next time you buy a new Z06, GM will produce a 420HP model the following year and yours will be a slow pig! ...So you will trade it in a buy an new ZO6...This will keep the shareholders' happy!!!
When the volume sales for a particular year start to decline they will modify the motor to produce higher HP and everyone will won't a new car because it has more HP than last years' model...
The ZO6 was a classic example; the first model was 385HP now they are 405HP.
So next time you buy a new Z06, GM will produce a 420HP model the following year and yours will be a slow pig! ...So you will trade it in a buy an new ZO6...This will keep the shareholders' happy!!!
Trending Topics
TECH Apprentice
Joined: Aug 2002
Posts: 331
Likes: 0
From: Gambrills, MD
Re: Why port factory heads? There are some other factors also involved. As has already been noted, stock heads are optimized for the stock cam, which has low lift and duration #'s. This benefits fuel economy, emissions, and driveability --- at the expense of performance. The Z06 heads have much larger ports --- good for performance, but bad for economy & driveability.
Also, aftermarket heads are carefully machined, either by hand or with a CNC machine. This removes all the casting irregularities, smooths airflow, etc. It's also expensive.
Also, aftermarket heads are carefully machined, either by hand or with a CNC machine. This removes all the casting irregularities, smooths airflow, etc. It's also expensive.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Re: Why port factory heads? The reason they don't do it is because of cost. Every operation on a head costs money. Porting and polishing takes a lot of cyle time and would cost big bucks. They want the best performance they can get for the cost. The gains of porting just don't justify the added cost on a production basis. Remember, they are making all these heads on the same machining line in Ypsilanti: 5.3, 5.7, 6.0, and the LS1-LS6. They achieve a cost reduction by commonizing tooling and manufacturing processes for all these parts. It is one of the reason GM is making money this year, and Ford and Chrysler are just scraping by.
GM already has a lost-foam casting that puts it light years ahead of it's competitors who still sand cast heads. have you felt the short side radius on a stock LS1-head? On a lot of heads, you have to port and polish just to get where the LS1 starts. It s probably one of the best production heads in the world. Just MHO.
-Geoff
GM already has a lost-foam casting that puts it light years ahead of it's competitors who still sand cast heads. have you felt the short side radius on a stock LS1-head? On a lot of heads, you have to port and polish just to get where the LS1 starts. It s probably one of the best production heads in the world. Just MHO.
-Geoff
*Bad Trader*
Joined: Nov 2001
Posts: 1,459
Likes: 0
From: here and there
Re: Why port factory heads? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
The reason they don't do it is because of cost. Every operation on a head costs money. Porting and polishing takes a lot of cyle time and would cost big bucks </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">if they were cast to a diffrent size there would be no need to port or polish <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
(just had to put in 2 cents to show i read it lol)
The reason they don't do it is because of cost. Every operation on a head costs money. Porting and polishing takes a lot of cyle time and would cost big bucks </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">if they were cast to a diffrent size there would be no need to port or polish <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
(just had to put in 2 cents to show i read it lol)
