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799 do have valve seat overhang many times , the 243 dose not have this problem it is a more consistent casting . Any difference between the two are a wash after a CNC program .
799 do have valve seat overhang many times , the 243 dose not have this problem it is a more consistent casting . Any difference between the two are a wash after a CNC program .
Whatever you have, 799 and 243 heads are functionally identical except, as I said, for the casting method. The specs are the same. The surface texture WILL be different.
Whatever you have, 799 and 243 heads are functionally identical except, as I said, for the casting method. The specs are the same. The surface texture WILL be different.
And the vj!! These 799 came off a newer 5.3. Maybe gm killed flow/reverse flow off on purpose. It is only a 5.3. Corse thess 243s are off a newer 5.3 to. So honestly idk what gm thinking. Top cut is way more important than surface texture for your information
I have a set of 799's off a 2007 5.3 that look the same as the picture above.
But below is a set of 799's off a 2010 L20 4.8. Looks more like the 243, maybe.
that's interesting you have a set of non top cut 799s as well. That's why I posted this.
so guys know. 317s, most have a non desirable top cut as well and don't flow well.i wasnt aware of this with 799s .most I have seen have a top cut
Great info. I suspected the same as you. When you get the 243’s clean, re-post pics of them if you get some time. I see other differences, unless the debris is causing optical illusions. Thanks for posting this.
Great info. I suspected the same as you. When you get the 243’s clean, re-post pics of them if you get some time. I see other differences, unless the debris is causing optical illusions. Thanks for posting this.
I did clean them before flowing. Cause carbon. Especially in the valves job top cut,hurts the numbers. The top cut is probably the most important angle in a valve job. They all matter, but lack of one is crazy.
I did clean them before flowing. Cause carbon. Especially in the valves job top cut,hurts the numbers. The top cut is probably the most important angle in a valve job. They all matter, but lack of one is crazy.
Totally agree. 1/2” above the seat and 1/2” below the seat is 40% of importance in port design.
Great info. I suspected the same as you. When you get the 243’s clean, re-post pics of them if you get some time. I see other differences, unless the debris is causing optical illusions. Thanks for posting this.
Cant say I am suprised.
terrible manometer bounce on the 799s at higher lifts
Cool, thanks for posting the flow numbers. I got a set of 799 heads for a good price, but I did hand port them. I'm glad I did because the 243 heads flow better in your chart.
I see. The top cut is missing from the chamber. With the valve out I remember the ugly “step” from the steel seat to the chamber.
When my guy did the VJ with the Serdi cutter, it fixed that.
The exh is the same story.
Put your VJ on one port and report back.
I’d love to have a flow bench and VJ equip. Prob never come out of the basement.
Funny thing is, very few LS owners doing their own builds even consider a good valve job. Lap em and call it good.
01-26-2020, 01:07 PM
799 243 head difference 
