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Old 5th April 2007, 17:02   #1
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Default Multi-angle Valve job

Hi All,

Apart from a porting and polishing, I'm planning to get a multi-angle valve job done on my OHC .. searched the Forum but I didn't find any info on this ..

I'd like to know more about multi-angle valve jobs, specifically
  • whats the difference between a 3-angle and 5-angle valve job?
  • what are the pro's and con's of these?
  • can these be done on any car? - I read somewhere that American cars need these more than the Japanese - any merit in that?
Apart from discussions, links to good articles and schematic diagrams will also be useful.

Regards
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Old 5th April 2007, 17:13   #2
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Google is your friend
Honda-Tech.com: All Motor: 3 angle valve job Vs. multi angle valve job
The link is right from the Horse's mouth.

To put it simply, its just a way to increase airflow.
You can't go in for a 5 angle one(Also called radial). don't have anough material there.

For Honda stick to 3 angle.

Last edited by tsk1979 : 5th April 2007 at 17:15.
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Old 5th April 2007, 17:15   #3
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You want to do this on an OHC? Don't think you'll notice any difference if the job is done correctly. But chances are that it wouldn't be done right, and you'd end up doing more harm than good to your engine. Remember, its a Honda engine here, not an Chevy small block!
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Old 5th April 2007, 17:24   #4
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Quote:
Originally Posted by tsk1979 View Post
Google is your friend
Yes it is. But if we all believe that then we wouldn't have a Forum such as T-Bhp, would we?

Quote:
Originally Posted by tsk1979 View Post
Incidentally, I saw that link before I posted - seems to be a forum discussion on the the same.

Let me clarify - I'm more interested in the technical aspects of the valve-job, not some forum discussing their "opinion" of the job.

Quote:
Originally Posted by tsk1979 View Post
To put it simply, its just a way to increase airflow.
Paaji, I understand that. .
Give me the complicated - thats what i seek from you.

Quote:
Originally Posted by tsk1979 View Post
You can't go in for a 5 angle one(Also called radial). don't have enough material there.

For Honda stick to 3 angle.
Thats what I thought as well, can you please explain this point more.

Last edited by manveet : 5th April 2007 at 17:34.
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Old 5th April 2007, 17:29   #5
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Quote:
Originally Posted by manveet View Post
Yes it is. But if we all believe that then we wouldn't have a Forum such as T-Bhp, would we?
OT : Well said .. sometimes you have to make them understand.
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Old 5th April 2007, 17:31   #6
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Quote:
Originally Posted by Rtech View Post
You want to do this on an OHC? Don't think you'll notice any difference if the job is done correctly. But chances are that it wouldn't be done right, and you'd end up doing more harm than good to your engine. Remember, its a Honda engine here, not an Chevy small block!
Are you implying that a Honda engine is pretty well made and doesn't require a 3-angle valve job? Please explain.

p.s.
FYI - I plan to go for throttle body expansion and a Stage-II port-polish job. AFAIK it differs from a Stage-I in the sense that apart from porting-polishing they also shave off a bit of the head from here and there. That, and the valve job. So you telling me that I really don't need the valve-job, is that right?
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Old 5th April 2007, 17:43   #7
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well manveet. To do a thoroughly professional job, you would need to put the head on a flow bench. I know of only a handful of tuners, who do this, and none are in Delhi. Without that, it is more a case of hoping its done right rather than knowing it will be done right. If its done wrong, it could create a situation that could even restrict the incoming air rather than allow more to flow through. Ofcourse, i'm talking extreme cases to get the point across.

Edit: Yes, a Honda engine is built far better than many others, so to gain a small advantage, you need to put in a lot more effort and good workmanship. It would be far easier to get a larger percentage increase in power out of, say an Indica engine, than it would be from a Honda engine.

However, I feel you've started this thread to have a discussion on this subject, which is great. We need more technical discussions.

Last edited by Rtech : 5th April 2007 at 17:45.
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Old 16th April 2007, 17:52   #8
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Well, on preliminary browsing, I couldn't find a lot of technical info on this subject .. anyways, heres the little I found ..

Modified engines feature a multi angle valve job for increased head flow and performance. This usually entails placing different angles on the valve seat itself, increasing the flow of combustion gases and improving horsepower and torque. A multi angle valve job is the cutting or grinding of 2 or more angles on the seat and valve.





On most of our American engines we perform three angle/radius valve jobs. This is more applicable in the American iron heads and differs with some imports. We have seen most American cylinder heads benefit from a three angle radius valve job, but mostly because the American heads are so bad to begin with. Many American heads suffer from poor uneven castings right out of the box, so if performance is your goal, doing a multi angle valve job with bowl blending would be critical to your engines performance.


The more I read up, I realize a Honda may not require this at all.
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Old 17th April 2007, 01:49   #9
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Manveet,

Can you please post a link to where the italicized text is quoted from...

cya
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Old 17th April 2007, 02:21   #10
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Valve angles depend on the flow from the ports and the angle of the combustion chamber to the valve itself. This would vary from car to car and no one angle fits all. The jap cars tend to have good 2 angle jobs that work quite effectively most of the time the easiest way to identify which head needs an angle change is to see if the valve is surrounded by very steep walls in the combustion chamber.
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Old 17th April 2007, 02:27   #11
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Sorry am posting from my mobile hence could not edit my last post. The better option would be to change the combustion chambers design and increase compression.
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Old 17th April 2007, 11:09   #12
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Quote:
Originally Posted by Rehaan View Post
Manveet,

Can you please post a link to where the italicized text is quoted from...

cya
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Yes. Sure.

Valve Grinding, Valve Job, Multi Angle Valve
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Old 18th April 2007, 02:25   #13
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A good ported polished cylinder head is benifitted a lot by a good valve job it can contribute as much as 25% in flow gain, usually stock factory valve seats involve only cutting 45-deg surface so as to valve seal since the engines are mass produced the manufacturer usually ignores multiangle valve jobs since it becomes time consuming & adds cost factor

A typical 3 angle valve job is shown in fig below

In a three angle valve job two additional cuts are made on each side of 45-degree seat cut the first cut is around 60-70 deg which is also known as throat cut it helps the air entering combustion to have a smooth transition to wards 45-deg seat cut, the other cut after the seat is 30-deg cut aka top cut. the whole idea of multiangle job is to make path smoother for air to enter combustion chamber.

For people who are porting/polishing cylinder head, getting multiangle valve job from a good turner will definately help.

Apart from this there is also 5 angle valve job also known as Radius valve jobs these are more aggresive cuts to give smoothest of flow for intake & exhaust ports.

fyi:Honda B Series engines heads the valve seats are 3 angle from factory itself.
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Old 18th April 2007, 06:20   #14
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Excellent diagram and explaination Ford_Rocam!

Definitely made things a lot clearer....

I guess although a completely radiused valve would be the best and smoothest for flow, it would be very hard to get it to make an exact seal with the head when closed, and hence the multi-angle is the next best bet since where the valve seals with the head they are like tapering cones, and as long as the angle and size are close enough between the valve and head, it will seal well.

cya
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