What makes a head better than another head?
08-18-2009, 12:27 PM
#1
12 Second Club
Thread Starter
iTrader: (7)
Join Date: Jun 2009
Location: Baltimore, MD
Posts: 406
Likes: 0
Received 0 Likes
on
0 Posts
What makes a head better than another head? Okay, I searched the stickies, high and low, and there's terrific info, however I can't determine WHY some heads are better than other heads.
The name brand heads that are custom cast are twice (sometimes more) the price, and people talk about how good they are. Well I know this is a newbie question but, why? Aren't heads just holes? Why are some ported "better" than others? Why are some not ported at all? Are there different ways to port? Different end goals?
I know there are different combustion chambers and valve sizes and whatnot. But why are two heads with the same dimensions different quality and thus performance?
Also, on a side note, if you got heads for a 346 with 1 3/4 headers, and then went to a big cube (400+) could you have the exhaust ports enlarged to take advantage of a 1 7/8? Just curious as to how that works. If your exhaust port is 1 3/4 diameter, than any size over that for the primaries is wasted right?
Thanks for any clarification.
The name brand heads that are custom cast are twice (sometimes more) the price, and people talk about how good they are. Well I know this is a newbie question but, why? Aren't heads just holes? Why are some ported "better" than others? Why are some not ported at all? Are there different ways to port? Different end goals?
I know there are different combustion chambers and valve sizes and whatnot. But why are two heads with the same dimensions different quality and thus performance?
Also, on a side note, if you got heads for a 346 with 1 3/4 headers, and then went to a big cube (400+) could you have the exhaust ports enlarged to take advantage of a 1 7/8? Just curious as to how that works. If your exhaust port is 1 3/4 diameter, than any size over that for the primaries is wasted right?
Thanks for any clarification.
08-18-2009, 01:07 PM
#3
TECH Junkie
iTrader: (5)
Join Date: Feb 2007
Location: Key West, Florida
Posts: 3,183
Likes: 0
Received 0 Likes
on
0 Posts
lots of things come into play on heads and making power.
it isn't all about more air, its about smoother air, faster air.
too big of a port can be detrimental to low end power, too small will hurt top end performance.
valve angles and allow for bigger valves due to changes in tolerances for piston to valve clearance.
budget heads generally have less work done to the ports, more attention to detail takes longer which costs more, but generally increase the flow potential.
cost of aftermarket heads reflects thousands of man hours in research and development to make and optimum head. remember factory is the starting point, and are manufactured on a cost-effective basis. not always a power-effective basis. they also have looser tolerances.
anyone can take a grinder to a head...you have to know what you're doing to not MESS UP the head.
bad porting can cost power.
in the race for every possible horsepower, sometimes you 2x the price for a 1/10X gain...
it isn't all about more air, its about smoother air, faster air.
too big of a port can be detrimental to low end power, too small will hurt top end performance.
valve angles and allow for bigger valves due to changes in tolerances for piston to valve clearance.
budget heads generally have less work done to the ports, more attention to detail takes longer which costs more, but generally increase the flow potential.
cost of aftermarket heads reflects thousands of man hours in research and development to make and optimum head. remember factory is the starting point, and are manufactured on a cost-effective basis. not always a power-effective basis. they also have looser tolerances.
anyone can take a grinder to a head...you have to know what you're doing to not MESS UP the head.
bad porting can cost power.
in the race for every possible horsepower, sometimes you 2x the price for a 1/10X gain...
08-18-2009, 02:03 PM
#4
TECH Fanatic
iTrader: (1)
Join Date: Nov 2007
Location: NJ
Posts: 1,193
Likes: 0
Received 0 Likes
on
0 Posts
WOW thats a board question. heads are all about how the airflow's though them. Not just the amount the smallest size and shape change can. change everything about a head.
Also, on a side note, if you got heads for a 346 with 1 3/4 headers, and then went to a big cube (400+) could you have the exhaust ports enlarged to take advantage of a 1 7/8? Just curious as to how that works. If your exhaust port is 1 3/4 diameter, than any size over that for the primaries is wasted right?
To this question. Dont go enlarging exhaust port to try and get more flow. This side of the head work differently then the intake side too.
Its about the comb of the engine a big engine with 1 3/4 head or a small FI engine will still make more power with the 1 7/8 headers.
Also, on a side note, if you got heads for a 346 with 1 3/4 headers, and then went to a big cube (400+) could you have the exhaust ports enlarged to take advantage of a 1 7/8? Just curious as to how that works. If your exhaust port is 1 3/4 diameter, than any size over that for the primaries is wasted right?
To this question. Dont go enlarging exhaust port to try and get more flow. This side of the head work differently then the intake side too.
Its about the comb of the engine a big engine with 1 3/4 head or a small FI engine will still make more power with the 1 7/8 headers.
