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Old 10-27-2012, 08:54 AM
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L31 Valve Job

OK Im takin my vortecs to the machine shop monday to get checked out and milled. I was wanting to get a valve job done but didnt know if it would make a difference. does anyone have experience with this. My new valves are: int - 2 1/32 and exh - 1 9/32. Or should I just keep the stock valves in cause it wont make a difference. The heads will be on a 94 chevy pick up with jegs intake manifold and a jegs camshaft. Stock tbi.

Thanks for the input

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Old 10-27-2012, 09:29 AM
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Quote:
Originally Posted by allansmith859 View Post
OK Im takin my vortecs to the machine shop monday to get checked out and milled. I was wanting to get a valve job done but didnt know if it would make a difference. does anyone have experience with this. My new valves are: int - 2 1/32 and exh - 1 9/32. Or should I just keep the stock valves in cause it wont make a difference. The heads will be on a 94 chevy pick up with jegs intake manifold and a jegs camshaft. Stock tbi.

Thanks for the input
I think you meant to say the new exhaust valves are 1-19/32". We usually use decimal instead of fractional measurements, like 1.94 or 2.02 inch intakes and 1.5 and 1.6 inch exhausts.

I would keep the stock valve sizes on a street engine. Get a good three angle valve job and if you are replacing the stock valves, have the new valves back cut the same as the OEM valves are done.

Also be sure the seats are cut concentric to the guides. That will mean the guides will need to be good. If they're not good (and they seldom are if the heads are used), have them redone before the valve job is done. Any decent machine shop will be familiar w/all this.

Good luck.
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Old 10-27-2012, 10:45 AM
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If its a mild build and the factory seats and guides are in good shape then I wouldn't mess with it. There is power there in a more serious build but I don't know how hard you're pushing it.

I'd stick with the stock intake valve size, and maybe the stock exhaust valve size, maybe one bigger. cleaning up the bowls and guides is relatively easy (just time consuming) and can again make more power on a more serious build.
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Old 10-27-2012, 04:20 PM
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To have the larger valves installed will cost you a bunch of money. If done correctly and won't make any noticable difference in your application.

Be advised most used 350 GM Vortec heads are cracked. They have been running over 85 percent cracked at my shop. Last week had a guy bring in three pairs. He got one good head!!
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Old 10-28-2012, 07:32 PM
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I have herd that they crack easy. I just helped pull the motor after we drove it. Everything was good but guess I wont know for sure till I get them checked. Thanks guys
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Old 10-28-2012, 08:51 PM
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I have decided to do some more upgrades to these heads so for future purposees I have a solid pair of mean heads. I have been doing some research and what I have found out is that the springs are crap so I need some advise on upgrading these. I have parts below that I think would be great for these heads. what do u think. I will be getting the three angle valve job and port and polished. Im not sure if Im putting these on my truck now but Either way they will be put on a 355 or 383 in the near future. But not sure exactly what that setup will consist of. Just trying to get a mean pair of vortec heads for now and will decide all of that later.

thanks guys

Comp Cams 26981-16 Comp Cams Beehive Valve Springs

Comp Cams 19004-8 Comp Cams Ultra-Gold ARC Aluminum Rocker Arms

ARP 134-4201 ARP Head Studs
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Old 10-29-2012, 07:47 PM
How fast is fast enough?
 
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Quote:
Originally Posted by allansmith859 View Post
I have decided to do some more upgrades to these heads so for future purposees I have a solid pair of mean heads. I have been doing some research and what I have found out is that the springs are crap so I need some advise on upgrading these. I have parts below that I think would be great for these heads. what do u think. I will be getting the three angle valve job and port and polished. Im not sure if Im putting these on my truck now but Either way they will be put on a 355 or 383 in the near future. But not sure exactly what that setup will consist of. Just trying to get a mean pair of vortec heads for now and will decide all of that later.

thanks guys

Comp Cams 26981-16 Comp Cams Beehive Valve Springs

Comp Cams 19004-8 Comp Cams Ultra-Gold ARC Aluminum Rocker Arms

ARP 134-4201 ARP Head Studs
you're getting ready to drop some serious money on stock thin casting heads... For the same money you can get new aftermarket heads that are a hell of a lot better.

Vortec heads are great for a CHEAP head. When you take the cheap out of the equation they're not that great. Bowtie Vortec's on the other hand are a great aftermarket head, but aren't exactly cheap.
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Old 10-30-2012, 10:57 AM
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Ya your right. I want to stay cheap on these heads for sure. I def want to get different rocker arms and valve springs. What kind do you recomend?

Thanks
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