porting heads?
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Posting Guru
Joined: Jun 2003
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From: Des Moines, Iowa
porting heads?
well i am still getting my engine rebuilt and was wondering if porting the heads of my 77 400m are worth it? i am getting a cam headers intake and holley 750 carb, what do you guys think? the shop will charge 150 for porting the heads and then they also suggested roller tipped rockers for 200, with all that. what should i expext and is it worth it? it will be going in my 77 ford f150 4x4 and i am wanting to do some good off-roading with at least 35" tires.
Posting Guru
Joined: Aug 2000
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From: (near) Denver USA
porting heads?
IMO, any shop that would charge $150 for porting either:
a) doesn't know what they are doing, or
b) is charging you too much to do something so easy that you could it yourself.
There are several other recent threads on porting, with a variety of suggestions and ideas on the topic.
I think full roller rockers (roller fulcrums and roller tips) are worthwhile, but I wouldn't use "roller tipped" rockers.
a) doesn't know what they are doing, or
b) is charging you too much to do something so easy that you could it yourself.
There are several other recent threads on porting, with a variety of suggestions and ideas on the topic.
I think full roller rockers (roller fulcrums and roller tips) are worthwhile, but I wouldn't use "roller tipped" rockers.
Posting Guru
Joined: Mar 2002
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From: Boise, Idaho
porting heads?
Bubba's right. Unless you have a huge aversion to getting a little dirty, you should consider doing it yourself.
You might want to look for some early 70's Cleveland 2V heads. The ports start out a little better and they don't have the water jacket problem in the port roof like the later 351M/400 heads have.
Bubba, why don't you recommend the roller tip rockers. I was considering them because they reduce the friction where it's worst - on the tip of the valve. The roller fulcrum is good but the stock fulcrum is large enough to reduce the amount of PSI to a much lower level, reducing the amount of heat generated.
As I understand it, stock rocker systems produce a lot of heat. The roller stuff's big advantage is that it reduces the heat. I think it also reduces the oiling requirements. On stock systems, oil is what carries the heat away from the hot springs and valves. (The constant flexing of the valve springs also produces heat. I don't know why, I just heard that it does.)
You might want to look for some early 70's Cleveland 2V heads. The ports start out a little better and they don't have the water jacket problem in the port roof like the later 351M/400 heads have.
Bubba, why don't you recommend the roller tip rockers. I was considering them because they reduce the friction where it's worst - on the tip of the valve. The roller fulcrum is good but the stock fulcrum is large enough to reduce the amount of PSI to a much lower level, reducing the amount of heat generated.
As I understand it, stock rocker systems produce a lot of heat. The roller stuff's big advantage is that it reduces the heat. I think it also reduces the oiling requirements. On stock systems, oil is what carries the heat away from the hot springs and valves. (The constant flexing of the valve springs also produces heat. I don't know why, I just heard that it does.)
Posting Guru
Joined: Aug 2000
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From: (near) Denver USA
porting heads?
Paul,
With conventional rockers, the worst thing about the rocker-to-valve interface is the side loads imparted to the valve guide/valve stem. Roller tips dramatically reduce that.
The biggest source of friction, however, is the fulcrum, and it is for the same reason that the force/area is lower, i.e., more surface area.
IMO, for the small cost difference between just a fulcrum conversion, or sled fulcrum roller-tip rockers, you're better off to get a full-roller rocker.
The reason that moving the springs produces heat is a little theory called "conservation of energy." When the spring is released, it never returns as much kinetic energy as it took to compress it.
Internal friction in the metal absorbs significant energy. That kinetic energy is converted to heat in the metal. If not cooled sufficiently, excess heat will ruin the temper of the spring and cause fatigue and failure.
Ever notice how hot a coat hanger gets when you bend it back and forth until it breaks? That's an exaggerated example of the same principle.
With conventional rockers, the worst thing about the rocker-to-valve interface is the side loads imparted to the valve guide/valve stem. Roller tips dramatically reduce that.
The biggest source of friction, however, is the fulcrum, and it is for the same reason that the force/area is lower, i.e., more surface area.
IMO, for the small cost difference between just a fulcrum conversion, or sled fulcrum roller-tip rockers, you're better off to get a full-roller rocker.
The reason that moving the springs produces heat is a little theory called "conservation of energy." When the spring is released, it never returns as much kinetic energy as it took to compress it.
Internal friction in the metal absorbs significant energy. That kinetic energy is converted to heat in the metal. If not cooled sufficiently, excess heat will ruin the temper of the spring and cause fatigue and failure.
Ever notice how hot a coat hanger gets when you bend it back and forth until it breaks? That's an exaggerated example of the same principle.
Posting Guru
Joined: Aug 2000
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From: (near) Denver USA
porting heads?
You either misunderstood the builder, or it's a case of: a) he doesn't know what he is doing.
Port matching involves grinding both the heads and the intake manifold to produce equal flow on all ports, from the intake plenum to the valve head. Every port requires unique grinding and modification. It is very painstaking work, and it requires great skill and hours of flow bench testing to do it right. I wouldn't trust anybody who offered to port match a set of V8 heads for less than $800-$1K.
If he's talking about "gasket matching," that's almost a total waste of time and money, and again, it makes me think he doesn't know what he's doing. (If any amateur is going to work on my heads, it'll be me.)
Check out the other recent threads in this forum on the topic of porting. There's a lot of info there (including an explanation of port matching and other terms).
Port matching involves grinding both the heads and the intake manifold to produce equal flow on all ports, from the intake plenum to the valve head. Every port requires unique grinding and modification. It is very painstaking work, and it requires great skill and hours of flow bench testing to do it right. I wouldn't trust anybody who offered to port match a set of V8 heads for less than $800-$1K.
If he's talking about "gasket matching," that's almost a total waste of time and money, and again, it makes me think he doesn't know what he's doing. (If any amateur is going to work on my heads, it'll be me.)
Check out the other recent threads in this forum on the topic of porting. There's a lot of info there (including an explanation of port matching and other terms).
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Posting Guru
Joined: Jun 2003
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From: Des Moines, Iowa
porting heads?
i have heard from all around that these guys are good and know what they are doing, i have taken my old jeep straight six there and it runs stronger than than the new v8 i was going to throw in it. what kind of HP number can i expect from port matched heads and intake, comp. ratio of 9/1 - 9.5/1, cam, roller rockers, headers, and 750 carb? is this close to 350 hp?
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Posting Legend
Joined: Sep 2001
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porting heads?
Build your engine to 1971 specs and blueprint it.
A 750 will not get you any more power but it will give you worse mileage than a 600/650.
Anybody that will port a set of heads for $150 absolutely does not know what they are doing or is just doing a little window dressing that isn't worth the effort. I can see $150 per cylinder for a little minor porting work.
Read the threads here, then read them again and again...
Get the book bubbaf250 mentioned:
http://www.motorhaven.com/customer/p...&cat=44&page=1
and READ it!!!!
Email me if you want some more books to read, I have a whole list...
Finally, LISTEN to bubbaf250, Beyer, and GT40 etc our foremost experts on the 400! You will find there are several here if you read enough posts.
A 750 will not get you any more power but it will give you worse mileage than a 600/650.
Anybody that will port a set of heads for $150 absolutely does not know what they are doing or is just doing a little window dressing that isn't worth the effort. I can see $150 per cylinder for a little minor porting work.
Read the threads here, then read them again and again...
Get the book bubbaf250 mentioned:
http://www.motorhaven.com/customer/p...&cat=44&page=1
and READ it!!!!
Email me if you want some more books to read, I have a whole list...
Finally, LISTEN to bubbaf250, Beyer, and GT40 etc our foremost experts on the 400! You will find there are several here if you read enough posts.
Posting Guru
Joined: Mar 2002
Posts: 2,070
Likes: 2
From: Boise, Idaho
porting heads?
Eric makes an excellent point when he says 'build it to 1971 specs and blueprint it.'
A lot of power can be make just by getting the engine to work the way it was originally designed to work. Zero deck, close fitting pistons, rings that are hand gapped, ports and valves that are perfect. Getting the details right makes a big difference.
A lot of power can be make just by getting the engine to work the way it was originally designed to work. Zero deck, close fitting pistons, rings that are hand gapped, ports and valves that are perfect. Getting the details right makes a big difference.
Posting Guru
Joined: Jun 2002
Posts: 1,099
Likes: 0
porting heads?
They have done so many articles in the past that show how to gasket match. It's so stupid to think the gasket manufacturer has the ideal port shape in their gasket opening. The gasket's only purpose is to seal the port. They have larger openings so they won't interfere with any airflow. Gasket matching is nothing more than "Porting for Dummies".
Blueprinting is something to be done yourself. It's very time consuming. Paying someone else to do it right is a waste of money. You would be lucky to gain 10HP.
Blueprinting is something to be done yourself. It's very time consuming. Paying someone else to do it right is a waste of money. You would be lucky to gain 10HP.
