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Old 08-21-2016, 03:48 PM   #1
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Default Cylinder head machining questions

I'm going back to machining school soon and I'm looking for advice and guidance on valve jobs.

Where are you machinists placing pointers on the valve and on the cutter for best performance? I've been doing slighty above center of the valve and on the top of the 45 angle

What SEAT angles are you guys using for boosted motors, nitrous motors, NA etc

Tips and tricks you guys want to reveal for LS heads...

thanks
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Old 08-21-2016, 10:49 PM   #2
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I put the seat cut all the way out to the edge of the valve. I like using a couple 45 degree cutter profiles that every SAM student gets that seem to work really well on the LS/SBF stuff. The top and bottom angles are not too far off the typical 30-45-60, but I have a 75 degree bowl cut under the bottom cut. The seat is only about .040 wide, so on power adder stuff, I might use a cutter with the same angles but a wider seat to help dissipate heat better.
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Old 08-24-2016, 06:52 PM   #3
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Okay, are you making a back cut on the intake valve? If so how wide do you leave the primary angle on the valve? I am an NTC student in MN. If you were to change the angles slightly is it a steeper 30 and 60? Also what do you mean by cutter profiles?
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Old 08-25-2016, 02:08 AM   #4
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When I make the bottom 30* cut on a traditional 3-angle performance valve job, I'll typically set the dial indicator .015 less than the diameter of the valve.

Once the seat angle is cut, the bottom cut sets the width of the seat and the top angle (60* for example) sets the width of the seat. Which I vary depending on the application.
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Old 08-25-2016, 02:10 AM   #5
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Sometimes you have to be careful with back cuts on the valve. I've seen them loose flow numbers and I've seen them gain.......on both intake and exhaust. It takes some flow testing to see what certain heads/valve designs work best with.
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Old 08-25-2016, 08:57 AM   #6
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Quote:
Originally Posted by Createaaron View Post
Okay, are you making a back cut on the intake valve? If so how wide do you leave the primary angle on the valve? I am an NTC student in MN. If you were to change the angles slightly is it a steeper 30 and 60? Also what do you mean by cutter profiles?
I will usually leave the backcut that's on aftermarket valves, but with stock valves, I use a 30 degree. I haven't really played around with them as far fine tuning a port, but a 30 is better than nothing. Obviously, you want the seat width on the valve at least the same width as the seat cut in the head, but on most LS valves I've ground, you can get the back cut really wide before ever even getting close to that.

On both the intake and exhaust, the top cut should be steeper than 35 degrees. You can look at the spec sheets for a lot of the aftermarket castings online and most of them will be around 36-38 degrees on the top cut. On the intake side, I go steeper than 60 and more shallow on the exhaust. Both get a 75 bowl cut to narrow the bottom cut to about .100" wide.

I don't manually cut each angle. You can purchase cutters with the profile you want built in. Newen, for example, has dozens of cutter profiles available with the top, seat, and bottom angles built in. You can even design your own. Some even have multiple radii for exhaust valvejobs.

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Old 08-31-2016, 09:20 PM   #7
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Thanks for the replies, guys. I'll try these tips
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Old 09-04-2016, 04:06 AM   #8
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KCS: how come the practice isnt to make both the convex and concave profiles more round?
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Old 09-08-2016, 08:46 PM   #9
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KCS: how come the practice isnt to make both the convex and concave profiles more round?
I'm not sure what you mean, are you taking about using radii instead of angles?
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Old 09-16-2016, 06:59 PM   #10
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Bringing back this thread with more questions.. What size intake valve can you fit in a 5.3 862 head in regards to no shrouding? 2" possibly? It will be on a 3.898 bore iron block. Also, I'm really interested in these conical valve springs that comp cams offers. Any thoughts/reviews on those?
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Old 09-17-2016, 03:10 PM   #11
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Bringing back this thread with more questions.. What size intake valve can you fit in a 5.3 862 head in regards to no shrouding? 2" possibly? It will be on a 3.898 bore iron block. Also, I'm really interested in these conical valve springs that comp cams offers. Any thoughts/reviews on those?
The seat insert is large enough for a 2.02" intake valve, which wouldn't be shrouded in a 3.898" bore. It's less than 52% of the bore diameter.

I had the Comp conical springs in my Trans Am. One broke, valve dropped, now I'm replacing engine. Not sure why it broke but I probably wouldn't risk it in this time around with the new engine.
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Old 09-17-2016, 03:41 PM   #12
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Thank you that is helpful! Do you bottom out your new springs when you get them? Basically coil bind them on a spring tester to check if any break.
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Old 09-19-2016, 12:34 AM   #13
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Thank you that is helpful! Do you bottom out your new springs when you get them? Basically coil bind them on a spring tester to check if any break.
Sort of. I compress them to coil bind to see what the height is. That, along with the valve lift, will determine my installed height. The springs will break if they're going into coilbind in a running engine, but not on a static spring tester.
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Old 10-20-2016, 06:27 PM   #14
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KCS, assuming youre a machinist. Do you deck your intake/exhaust gasket surfaces, if so, what machine are you using?
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Old 10-20-2016, 06:54 PM   #15
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How many years have you been doing this? You have excellent tips!
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Old 10-21-2016, 10:29 AM   #16
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KCS, assuming youre a machinist. Do you deck your intake/exhaust gasket surfaces, if so, what machine are you using?
I used to be a machinist, so I haven't had the need on anything in a while, but I used to use a Storm Vulcan mill that could be used for milling cylinder heads, intake manifolds, or engine blocks.

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How many years have you been doing this? You have excellent tips!
Thanks. I started in 2005 when I went to SAM but I was lured into the Oil & Gas industry a few years ago. I still help out at a local shop on weekends when I have time.
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Old 10-28-2016, 11:24 PM   #17
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Quick question. Looking at pistons and rods for my build.. Im looking at pistons that utilize a 1.313 or 1.314 piston ch but the specify using a 6.125 rod on there specs. Can i use a 6.098 or 6.100 rod with these pistons? If theyre the same pin diameter i dont see an issue. If i use the 6.100 rod with 1.314 it would put me at zero deck
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Old 11-03-2016, 02:28 AM   #18
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Quick question. Looking at pistons and rods for my build.. Im looking at pistons that utilize a 1.313 or 1.314 piston ch but the specify using a 6.125 rod on there specs. Can i use a 6.098 or 6.100 rod with these pistons? If theyre the same pin diameter i dont see an issue. If i use the 6.100 rod with 1.314 it would put me at zero deck
Impossible to calculate until you provide us with a stroke measurement. If using a stock crank, the 6.100 rod and a ch of 1.314 in a 9.240 deck height block would put the piston in the hole 0.015". If doing machine work on the block, you're gonna loose some of that when the decks are squared up.

On the stock 9.240 deck and a 6.125 rod/stock stroke and 1.314 ch, the piston would be 0.010" out of the hole before squaring the decks.

Obviously the pistons are designed for a stock stroke and will not work with a 4" crank and typical rod lengths.
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Old 11-06-2016, 05:26 PM   #19
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I was just asking if i can interchange rods on a certain piston as long as i end up with the piston height i want. Found my answer elsewhere
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