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5.3 Chevy 862 valve job porting questions

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5.3 Chevy 862 valve job porting questions

Postby c4mo » Thu Aug 29, 2013 11:13 pm

I tried to do a little searching before I ask, but here goes. I'm wondering the max I can mill the heads, I've been told around .040. I assume bowl work will help these out. A good valve job and set the throats at 90%? Any suggestions on valve job angles? From searching airflowdevelop wrote 39/45/60/75/90 the thread was about 243 heads so I'm wondering if this applies here. I'm guessing that kind of valve job will take care of the throat diameter. I figure that a 2.00 valve would be wise, while leaving the stock exhaust valve size.
To give an idea on application:
2004 5.3
233/241 at .050 111+3 (rough estimate from cam grinder, yet to purchase)
Ls7 lifters
PAC 1218 springs
Victor singleplane
750 holley
Long tube headers, speced by pipe max 1 5/8-1 3/4 3 in collector
Pg trans brake
4800 stall 8 inch
6.14 gear
32 x 14 tire
3061 w/ driver.

Thanks
Morgan Allen
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Re: 5.3 Chevy 862 valve job porting questions

Postby CGT » Fri Aug 30, 2013 8:43 am

The 862's I have seen have the throat WELL over 90% with no material for a bottom cut. It will take a bigger valve to be able to get a decent valve job on that head, judging from the ones I've seen.
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Re: 5.3 Chevy 862 valve job porting questions

Postby SMITHBERGRACING » Fri Aug 30, 2013 9:30 pm

c4mo wrote:I tried to do a little searching before I ask, but here goes. I'm wondering the max I can mill the heads, I've been told around .040. I assume bowl work will help these out. A good valve job and set the throats at 90%? Any suggestions on valve job angles? From searching airflowdevelop wrote 39/45/60/75/90 the thread was about 243 heads so I'm wondering if this applies here. I'm guessing that kind of valve job will take care of the throat diameter. I figure that a 2.00 valve would be wise, while leaving the stock exhaust valve size.
To give an idea on application:
2004 5.3
233/241 at .050 111+3 (rough estimate from cam grinder, yet to purchase)
Ls7 lifters
PAC 1218 springs
Victor singleplane
750 holley
Long tube headers, speced by pipe max 1 5/8-1 3/4 3 in collector
Pg trans brake
4800 stall 8 inch
6.14 gear
32 x 14 tire
3061 w/ driver.

Thanks

LS heads like a wide (.100+) top cut. You can take alot more than .040 off if desired as long as you have piston to valve clearance. The 2.00 valve is as big as you can go if you are running the 5.3L bore and as already stated will help get the throat size back.
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