5 Angle Valve cut? What's it mean really?
Thread Starter
Melting Slicks
Joined: Dec 2004
Posts: 2,137
Likes: 5
From: Howard PA
5 Angle Valve cut? What's it mean really?
So I take my LT4 heads to get a 3 angle valve job done and the machinist asks me "you mean a competition valve job?" I said yeah, thinking it mean a normal 3 angle.
I went to pick them up today and this is what I wound up with, a 5 angle.
Can someone explain the the cuts, if it's worth it or is a 3 angle enough, also if this looks right for a 5 angle? It looks good but does it do anything over a 3 angle? I can't find much on Google explaining the differences.
Thanks.
I went to pick them up today and this is what I wound up with, a 5 angle.
Can someone explain the the cuts, if it's worth it or is a 3 angle enough, also if this looks right for a 5 angle? It looks good but does it do anything over a 3 angle? I can't find much on Google explaining the differences.
Thanks.
Racer
Joined: May 2005
Posts: 472
Likes: 1
From: looking for my insanity state of confusion
On a 5 angle valve job, they just cut the valve seats at 5 different angles for better air flow. A 3 angle grind is sufficient for most street applications. There is also radius grind on the seats, but that isn't worth it unless your into competition. As far as the pictures, I can't tell how many angles are cut.
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
I've seen this type work. Great job by the machinest. I have heard of bowl blending before. I was going to learn that technique. I need to fix up my valve grinder. My Sioux seat grinder is in perfect shape. Three angle valve jobs are extremely easy. The work I see in these pic that are posted take a pro. "NICE" 
Get a copy of How To HotRod Small Block Chevy's. It's worth its weight in gold. Trust Me... 
Get a copy of How To HotRod Small Block Chevy's. It's worth its weight in gold. Trust Me...
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Racer
Joined: Aug 2002
Posts: 432
Likes: 0
From: Lancaster CA
i was under the impression that all 5 angles are on the head (which is what that diagram shows) and that it is to smooth out the air flow, not change how well the valve seats. unless i am mistaken, which i dont think i am, the valve only contacts the head on the 45 degree section and that is where the seal is made.
Race Director
Joined: Dec 2002
Posts: 13,345
Likes: 230
From: SCMR Rat Pack'r Charter Member..Great Bend KS
Originally Posted by SSLT1KID
i was under the impression that all 5 angles are on the head (which is what that diagram shows) and that it is to smooth out the air flow, not change how well the valve seats.
The photos show no more than a 3-angle seat, possibly only a 2-angle...on the seat! (valves angles are not considered in this context)
Multi-angle cuts do improve performance (flow) slightly. The trade-off (and there is always a trade-off) is reduced valve/seat life.
The more angles on the seat, the less surface area available for the one angle that the valve actually seats on. This means that seat pressure (in psi) goes up, which results in increased wear (not so much abrasive wear, but impact wear)on the small actual sealing/seating area on the valve and on the seat itself.
ALLT4, I don't think you got a five-angle seat on those heads.
If there was, you'd barely be able to see any angles at all; each one being so very small, it would look more like one, continuous radius.BTW, they don't actually cut radii on seats because they would wear...very, very quickly...into a "flat" anyway, losing valve clearances in the process.
Larry
code5coupe
Thread Starter
Melting Slicks
Joined: Dec 2004
Posts: 2,137
Likes: 5
From: Howard PA
It's hard to see in the picture but when I look at them close in strong light I can count at least 4 cuts on the seat, maybe 5. I can almost see a tiny little cut right before the last cut in the chamber.
There are three cuts on the valve, two larger ones on the back and then the margin.
I don't know, but from what I can see flow should be increased some.
There are three cuts on the valve, two larger ones on the back and then the margin.
I don't know, but from what I can see flow should be increased some.
Instructor
Joined: Nov 2001
Posts: 141
Likes: 0
From: Renton WA
I'd like to know how to do a valve job properly that isn't three angle.
I'll save you the grief. It's not possible.
Ok, well, new heads many times have only 2 angles cut into them. But, invariably you always need 3 angles to adjust valve overhang and seat width anyway.
Kind of like "hardened" valves seats. If they are hardened, why can you cut them with a simple hand file?
I'll save you the grief. It's not possible.
Ok, well, new heads many times have only 2 angles cut into them. But, invariably you always need 3 angles to adjust valve overhang and seat width anyway.
Kind of like "hardened" valves seats. If they are hardened, why can you cut them with a simple hand file?
Burning Brakes
Joined: Jun 2003
Posts: 937
Likes: 0
From: Bedford Tx
OK, I see,
an inside cut,
the seat cut,
three outside-bowl cuts, with the middle cut of
those three being by far the most obvious.
........
with that said,
how popular,
is the back cut intake valve,
for the older SBC?
edit, spellimg
an inside cut,
the seat cut,
three outside-bowl cuts, with the middle cut of
those three being by far the most obvious.
........
with that said,
how popular,
is the back cut intake valve,
for the older SBC?
edit, spellimg
Last edited by silver84; Jul 23, 2006 at 07:08 AM.
Thread Starter
Melting Slicks
Joined: Dec 2004
Posts: 2,137
Likes: 5
From: Howard PA
I don't know how you can possibly say you only see three cuts. They don't look like the diagram but I don't think they're supposed to. The diagram only explains the the cut angles, not how wide all of them should be.
Here. I blew some up a bit.
Here. I blew some up a bit.
Last edited by ALLT4; Jul 23, 2006 at 07:36 AM.
Team Owner
Joined: Sep 2002
Posts: 22,209
Likes: 12
From: OBAMA IS HITLER
Originally Posted by rocco16
Multi-angle cuts do improve performance (flow) slightly. The trade-off (and there is always a trade-off) is reduced valve/seat life.
by the way, regarding reduced valve/seat life......are you referring to a 3 angle job (ultra popular for street applications) or a 5 angle job? and either way, how much of a reduced life? and what is required to remedy that?
Last edited by Red Tornado; Jul 23, 2006 at 12:13 PM.
Racer
Joined: Aug 2002
Posts: 432
Likes: 0
From: Lancaster CA
The more angles on the seat, the less surface area available for the one angle that the valve actually seats on. This means that seat pressure (in psi) goes up, which results in increased wear (not so much abrasive wear, but impact wear)on the small actual sealing/seating area on the valve and on the seat itself.
i dont think that is the case. the valve only seats on the 45 degree section and there are set limitations for that ( i cant remember them right now, but it is a pretty tight tolerance) the multiple cuts go into the "meat" of the head not the valve seat itself. i know you dont want the valve seat to be too narrow because it will not have enough cooling surface contact area with the head and it can burn a valve. you also dont want it to be too broad of a contact area, but i an not remember the reason why. but even if you do not have a multiple angled valve job there is a set limitation to the valve seat.
i dont think that is the case. the valve only seats on the 45 degree section and there are set limitations for that ( i cant remember them right now, but it is a pretty tight tolerance) the multiple cuts go into the "meat" of the head not the valve seat itself. i know you dont want the valve seat to be too narrow because it will not have enough cooling surface contact area with the head and it can burn a valve. you also dont want it to be too broad of a contact area, but i an not remember the reason why. but even if you do not have a multiple angled valve job there is a set limitation to the valve seat.