vonmoldy

I know what extude honing is but is it good idea on heads here are some on ebay wanted to know what y'all thought.
http://cgi.ebay.com/ebaymotors/LT1-P...spagenameZWDVW

slopokrodrigez

I think the extrude hone is a great idea for heads. I hadn't thought about doing them. The price is right for the heads also. BUT, be careful with them having been milled down to 50cc chambers. I can't remember what stock is but you may have 2 issues.

The CR may have been raised too high for your application and they may not fit without modifying your intake to compensate for the milling.

Also, if you plan to use them on a completely stock engine, you probably won't see much gain from them. You would want at least a cam that can utilize the flow characteristics better.

Fred can best tell you about the CR and fitment. Give Injuneer a PM or wait a little while, he'll appear here.

rskrause

Ask yourself these questions: have I ever heard of a professional race team using heads prepared this way? Have I ever heard of a head manufacturer using it?

Rich

Mindgame

There are areas in the port where you don't want to remove material, or perhaps only want to remove a little. Extrude-hone is indiscriminant... it doesn't "know" where to remove and/or leave material. Basically, what you end up with is a larger scale verion of the existing port and that's not what you want.

-Mindgame

MachinistOne

Exactly

Most porter's pick up airflow by re-shaping ports in the correct area's, NOT by just making the port bigger, that kills velocity.

Extrude hone is great for 5.0L ford intake manifolds and stock class rule exhaust manifolds....nothing else.

1racerdude

AS&M has said that after their port work,they had some set's extrude honed and they picked up 9-10% more flow.
This was back in '95 and don't know if they still fool with it.
If ya do a stock set it's like has already been said ya just got a larger port with the good and the bad still there.

vonmoldy

I agree with the above comments about removing all instead of specific areas. And i think it would best be used after hand porting...but anyone have dyno comparo's? What about a LT1 intake. Extrude hone intake $600

rskrause

If that's the case, they need a new head porter!

Rich

1racerdude

Not according to them!!!!!

Mindgame

Bigger runner = higher volumetric flow rate. No surprises there right?

I think the part that some people miss is that.... more flow doesn't necessarily equate to... more power.

Any time you add volume to a port by relieving more material from the slow/lazy areas of a port, you will hurt power. A good head porter knows this... an abrasive putty does not.

-Mindgame

Z28barnett

I think the theory behind extrudehone is that the paste is a type of fluid.

Since air can be regarded as a fluid, in flow calculations, its flow pattern will be related to the flow of any other fluid.

If the theory is correct then "Lazy areas" of the port will see little abrasion from the extrude hone since the paste will not erode as much from that area as it does from parts of the port that allow fast movement of the paste along the walls.

How well theory matches practice is the big question.

I think on the intake you might gain more than you would on heads, since you can't easily do hand porting.

Back to back test would be interesting. Sounds like the test has been done once with some improvement. Might give a porter some extra info to see where the extrude hone removed material.

I wonder if you would need to simulate the valves to get better results?

All of this is speculation on my part. Pick the theory apart at will.

Z28

LameRandomName

Von -

I think that if I had a set of heads that I wanted to "smooth on out a bit", that I might consider extrude honing.
However, "smooth on out a bit" is kind of a fluid term; no pun intended.

I've got a little knowledge here, probably just enough to be dangerous; but I think the important thing to remember is that a port job and an extrude hone are NOT the same thing.

Extrude honing might be useful for putting a somewhat smoother finish on the inside of the ports, knocking down some casting flash or things of that nature. But that abrasive paste can't "think". If you try to use it as a substitute for a port job you may not get the results you expected.


Now...
My problem with the heads you are looking at on ebay is that it's impossible to truly know the thinking that went into the job or what kind of job was done.

You MAY get some nice heads or you MAY get some dogs that are too hogged out and have thin walls in bad places.

Ported heads are one of those things that you want to get from a reputable source.

1racerdude

Ya know there are different grits of that media.They can go from fine to polish like a mirror or course to take out material.
Not knowing what they used for AS&M it's hard to say if the port's were any larger or not. The 10% is what Jim told me when I went there. I didn't see the head's that had the work done on them.
As ya said ya can have flow without having size.

Mindgame

The problem with that theory is.... air doesn't cut anything. Air also moves through a port at 200-700 feet/sec and due to air density, speed and combustion chamber shape, valve open area, etc., it will not exhibit the same velocity map. IMO, this is simply a poor analogy.

Does a pressurized abrasive media moving through a port know which is the floor and which is the roof?

No, it will remove material from all surfaces it comes into contact with indiscrimantly. I think it has it's place. Removing small bumps, creating a smoother finish and making something larger overall. Won't be putting any head porters out of work though.

-Mindgame

rskrause

If you have to use stock cast manifolds, for some reason, the EH process can be useful. There would be people camped outside the place waiting to get if they could gain 10% on a good head port job.

Rich