Author Topic: jtanguay wrote: (Read 2522 times)

vanagonturbo · « **on:** July 07, 2008, 07:51:32 pm »

Oversized valves for an AAZ head. Anyone else know anything about this? I am going to be taking the valves out of my new AAZ head to port and polish it and it would be very convenient to know that oversized valves are being referred to here. I would love to have bigger valves, I just dont know what application. Thanks all!

jtanguay · « **Reply #1 on:** July 07, 2008, 08:20:47 pm »

i think you can use tdi valves, but then you need to have a machineshop do work on the head... valve seat grinding etc.

or are the tdi valves even bigger than the aaz??? maybe PD valves???

in the previous post i mentioned that 1.9 valves are bigger than 1.6 valves... not oversized :wink:

vanagonturbo · « **Reply #2 on:** July 07, 2008, 08:39:14 pm »

the AAZ valves are the same diameter as the TDI valves. I dont have any PD heads on the shelf so I cant measure them. Something about valve stem diameter might come to mind though.

The AAZ valves are definitely bigger than the 1.6 valves though.

jimfoo · « **Reply #3 on:** July 07, 2008, 08:49:11 pm »

Quote from: "vanagonturbo"

the AAZ valves are the same diameter as the TDI valves. I dont have any PD heads on the shelf so I cant measure them. Something about valve stem diameter might come to mind though.

The AAZ valves are definitely bigger than the 1.6 valves though.

Older AAZ's have 8mm stems where as newer ones have 7mm, as do TDI's. 7's are much easier to come by.

jtanguay · « **Reply #4 on:** July 07, 2008, 08:58:25 pm »

wonder why they went from 8mm to 7mm??? surely an 8mm one would have more surface area, and therefore spread the load on a greater surface? or were they looking to just lighten the load... OR were they trying to create a weak point in case of timing belt failure??? so that the valves would give and do less damage inside the motor?

vanagonturbo · « **Reply #5 on:** July 07, 2008, 09:15:18 pm »

I would assume flow improvement. Timing belt failure should not occur (according to the manufacturer, lol) so they probably didnt calculate for that.

jtanguay · « **Reply #6 on:** July 07, 2008, 10:37:00 pm »

Quote from: "vanagonturbo"

I would assume flow improvement. Timing belt failure should not occur (according to the manufacturer, lol) so they probably didnt calculate for that.

ah true...

myke_w · « **Reply #7 on:** July 11, 2008, 07:17:20 am »

Using smaller valve stems improves flow a good bit actually. Also (obviously) any material you can remove from behind the seat, the seat itself, port, and even guide will buy you flow. Hence 3 and 5 angle valve guides. There is more than one way to skin that cat

jimfoo · « **Reply #8 on:** July 11, 2008, 07:42:54 am »

Also, 7mm guides/valves can be put in an 8mm head with no problems.

saurkraut · « **Reply #9 on:** July 11, 2008, 08:01:20 am »

Quote from: "vanagonturbo"

I would assume flow improvement. Timing belt failure should not occur (according to the manufacturer, lol) so they probably didnt calculate for that.

I don't think anything can survive a highway speed timing belt failure, including 8mm vavle stems.