[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: VW & Audi cylinder head port info needed...
>The ports certainly appear to be *very*
> similar to each other but looks can be deceiving and since I'm not trying
> squeeze every last CFM possible out of it but merely clean up the major
> restrictions, I don't want to go to the trouble of casting port molds if I
> can avoid it. Any BTDTs will be greatly appreciated.
> Also, I'm going to use a larger exhaust valve but am having trouble
> any aftermarket sodium-filled ones with 7mm stems ... do such critters
> and if not, has anyone had any luck using Stainless Steel valves instead
Certainly the 4cyl and 5cyl heads are close enough that you should approach
them the same in porting. We have had great results by flattening the floor
around the radius in addition to normal smoothing and enlarging (for wide
open throttle). I would not enlarge other than the flattening and smoothing
for the street, but you will still lose some low speed velocity.
I have used Stainless in racing applications with no problem. In fact I
currently am racing a VW GTI motor with turbo at 22 lbs. boost using stock
valves (not sodium) that have been ceramic coated. EGT as high as 1750 F for
short periods and no problems (yet in two years). In other applications we
use Inconel for the exhaust which is superior to stainless for the heat. An
ideal situation would be to use stainless intake, Inconel exhaust, ceramic
coat the chamber, piston top, valve faces and exhaust ports after porting.
The last stainless 7mm valves I got were custom made, we had to cut to
length and the keeper groove.