LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Anyone know how much cfm gain by adding backcut swirl polished valves?

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Old Apr 3, 2007 | 01:21 PM
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Anyone know how much cfm gain by adding backcut swirl polished valves?

Taking heads of a buddys car and he doesn't have any left for porting. I thought that backcut/refacing work on the stock valves was around 35ish and thought that would pick up a decent gain for the money and be easy to replace? thanks
Old Apr 3, 2007 | 01:25 PM
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manley has descent valve sets..and you could do a 5 angle VJ
Old Apr 3, 2007 | 01:39 PM
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Originally Posted by mdacton
manley has descent valve sets..and you could do a 5 angle VJ
Yeah, but money being a big issue he isn't looking to upgrade to 200+ dollar valves + the cost of a valve job. The work mentioned above would be on the stock valves.
Old Apr 3, 2007 | 01:42 PM
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Well i can't say what it would be worth but i had it done to mine,but i also ported my heads myself at the same time.
Old Apr 3, 2007 | 01:57 PM
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I don't quite understand the question as asked. Please simplify it for me. I'm old.
Old Apr 3, 2007 | 02:01 PM
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Originally Posted by BUBBA
I don't quite understand the question as asked. Please simplify it for me. I'm old.
I think he wants to see what type of gains can be had from back cutting a stock valve.....probly 0-5 h.p.

the VJ has some h.p. to be found in it....but if $200 is high then I would just leave it how it is
Old Apr 3, 2007 | 02:22 PM
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So I assume that the statement that there is nothing left to port means that the heads were ported to the max including, of course, deep pocketing the valves. If this is the case, I doubt that doing anything to the stock valves is going to do anything with regard to increased flow. JMHO
Old Apr 3, 2007 | 03:40 PM
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Originally Posted by BUBBA
So I assume that the statement that there is nothing left to port means that the heads were ported to the max including, of course, deep pocketing the valves. If this is the case, I doubt that doing anything to the stock valves is going to do anything with regard to increased flow. JMHO
No, the heads are stock unported. just wondering what swirl polishing and backcutting the stock valves would do since heads are already off the car and ~35 seems like a good price

Last edited by 1LESSZ28; Apr 3, 2007 at 03:42 PM.
Old Apr 4, 2007 | 09:00 AM
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Originally Posted by 1LESSZ28
No, the heads are stock unported. just wondering what swirl polishing and backcutting the stock valves would do since heads are already off the car and ~35 seems like a good price
Go for it, what can it hurt?
Old Apr 4, 2007 | 11:02 AM
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Well, if that is what the original post says, then.....anyway, if you are going to the trouble of machining the valves, why in the world would you not at least machine the pockets, because that is the biggest restriction in the heads and will give you the biggest increase in flow.JMHO
Old Apr 5, 2007 | 11:23 AM
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Originally Posted by BUBBA
Well, if that is what the original post says, then.....anyway, if you are going to the trouble of machining the valves, why in the world would you not at least machine the pockets, because that is the biggest restriction in the heads and will give you the biggest increase in flow.JMHO
hmm. machining the pockets sounds like a great idea. any idea on cost? Would the increase be realized without porting other areas of the head?

Lol I can see how the first post is confusing...basically not enough leftover after the rebuild to port the heads.
Old Apr 5, 2007 | 11:55 AM
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You should realize the greatest benefit from valve pocket work---more than porting the rest of the heads. The MOST important thing for you to do is to locate someone who is reliable and has a stellar reputation for port work.

Then you can ask them what they will charge you for whatever work you want done on the heads. It's all based on time it takes. Obviously the more work, the longer the time. If pockets only, then it would be based on per pocket time. You might save money by deinstalling and installing the valve train, however, if it was me, I would have them do the whole job, even if the machining was just the pockets with some mild detail work on the the rest of the intake and exhaust ports.jmho
Old Apr 5, 2007 | 12:04 PM
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BTW: If you take the valve train apart, keep the parts in orderaccording to which cyl they come out of----valves, rods, rockers, etc.

And take some good photos of the ports and pockets, so that you can compare the finished product with the unfinished product. I.e.,take some after shots before the valve train is put back together.

This will accomplish several things. It will put the porter on notice that his work will be checked. It will be available to advertise his work. It will show others here what was done. It will give you the satisfaction of knowing that you got what you paid for. It will see if any damage was done.

Or.....as Martha would say "it's a good thing".
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