should new exh valves recieve undercut?

[ThikStik]

I guess Im gonna be the Alpha tester of a set of SB Internatial exh valves. I took a couple of valves out to look at them. I noticed that past the cut at the seat, toward the stem, there is a fingernail catching ridge. Should this ridge be ground away for flow improvement? I can def see this mattering on intake, but wasnt sure how it'd matter on exh . Also, i know this isnt exactly what under cut means. Any help, thanks.

 

[87GN_70GS]

What you are talking about is a backcut. 30 deg works nice there. Undercut refers to the stem.

 

[ThikStik]

Ok , so ill take them back and request a 30d backcut. I also will ask them how much they shaved from the heads, as im now worried the intake wont fit. I told them NOT to cut them..why wont they do anything the customer asks?! Well, there may be a fight with the angry guy at the Birmingham Cylinder Head Service. He already is incensed with me questioning the maker of the new exh valves. Thanks Scott. BTW-do u know of anyone who could port a set of irons in Ala? I may just start over with some low mile heads i have.

 

[Mad_Trbo]

Head resurfacing

How much did they have to cut, unless you saw a significant removal of material you should be ok.

 

[ThikStik]

He said they probably only took 5 thou or so. Thing is, these heads have been done 3 times. He did say that their surfacing machine is better than those of the past, and that my head surface was rough. and his new surface job was way better. He said he would cut the intake surface on the head vs on the intake if there is a mating problem. I coudnt tell a difference in the surfaces...but i have been pushing out felpro 9441 gaskets. Got some rjc's coming. thanks man

 

[WSLN 6]

I had more than that taken off my heads to remove receiver grooves and the intake still fits ok, you should be ok....You will see if you just set them on the block with the intake, open plenum I guess.
Pm me and we can chat about the RJC gaskets.

 

[charlief1]

What you are talking about is a backcut. 30 deg works nice there. Undercut refers to the stem.

The seats are cut at 45 degrees so the 30 degree won't help a lot. cut it closer to 20-25 or if you really want to make it flow start with 15 then do a 25 degree cut. This will allow you to get rid of the ridge and not mess with the seal on the valve. :biggrin:

 

[ThikStik]

Thanks WSLN, ill do that test fit. Charleif1, I guess ill just get the 30 back cut, cause ive already got them informed to do that. If i did the 15/25, that would entail cutting the head again woudnt it?