Vizard's 30 degree valve jobs
12-10-2002, 02:06 PM
#1
Drifting
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Vizard's 30 degree valve jobs
He;
has anyone tried out Vizard's suggestion of a 30 degree valve seat setup?
It's written up in his Max performance SBC on a budget book. There is a
technical review of the book in the Review section...
12-10-2002, 03:48 PM
#2
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Re: Vizard's 30 degree valve jobs (adam)
some production cars used the 30 degree seat,i think it was pontiac or buick. it helps low lift flow but a 30 degree back angle on the valve head to narrow the seat will also help. :chevy
12-10-2002, 04:19 PM
#3
Le Mans Master
Re: Vizard's 30 degree valve jobs (clem zahrobsky)
I picked up almost 25cfm (peak @ .400")by putting a 30* backcut on my intake valves. Usually the backcut is beneficial to low lift flow and sacrifices flow at higher lifts, but I didn't see a decline in flow until past .700". Considering each cfm is worth approximately 2 potential hp, that almost 50hp potential for less than $60 in machining...
Lift......B/C Int...... Std Int..... Exh
.200..... 136......... 138 .........111
.300..... 213......... 192......... 154
.400..... 274..........250..........215
.500..... 323..........304.......... 241
.600..... 359..........346......... 253
.700 ......378......... 373......... 258
.750 ......374......... 382 ..........261
.800....... 370........ 380.......... 262
Lift......B/C Int...... Std Int..... Exh
.200..... 136......... 138 .........111
.300..... 213......... 192......... 154
.400..... 274..........250..........215
.500..... 323..........304.......... 241
.600..... 359..........346......... 253
.700 ......378......... 373......... 258
.750 ......374......... 382 ..........261
.800....... 370........ 380.......... 262
12-10-2002, 04:50 PM
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Re: Vizard's 30 degree valve jobs (Monty)
That is a good improvment. Also those flows are very nice.
Was that your head porting or someone elses?
12-10-2002, 04:54 PM
#5
Le Mans Master
Re: Vizard's 30 degree valve jobs (adam)
Thanks, they're Dart CNC ported. I did a little gasket matching with a die grinder and roll but that's it, other than the intake valve backcut they're right out of the box.
12-10-2002, 06:24 PM
#6
Re: Vizard's 30 degree valve jobs (Monty)
I picked up almost 25cfm (peak @ .400")by putting a 30* backcut on my intake valves.
I was going to do this, instead I just put them back on the motor.
Maybe next time.
Or, can I retorque a head gasket once it has been torqued down but not ran?
12-21-2002, 11:58 AM
#11
Le Mans Master
Re: Vizard's 30 degree valve jobs (89vette)
Cutting a 30 degree angle on the backside of the valve. You've probably heard of a 3 angle valve job? This 30 degree angle is usually a 4th cut, and typically will show a noticeable improvement in low and mid-lift flow. It's a cheap mod that can be made during machining and assembly that can produce worthwhile improvements in power.
