2.9 valves

[bobbo]

The suggestion for the 2.8 is to install 2.9 valves.
are the 2.9 valves too large to use with the 2.8 seats ?
A lot of discussion on installing larger valves with existing seats is on various forums throughout the internet.
Any one with experience with this ?
No doubt a lot of geometry and flow designs would be involved.
Thanks Bob

 

[kmathis]

2.9 valves are the way to go, the whole issue with the 2.8 heads is breathing. with the 2.9 valves and seats you can really feel the difference in the power band. New seats and new valves and your machine shop shouldn't have any issues. I think the 2.9 valves are marginally taller or shorter than the 2.8 valves but not enough to make a difference. I ported and polished mine as well. there are a number of cams available for the 2.8 as well...but that can awaken all kinds of controversy.

 

[bobbo]

Kelly, seems reasonable that the larger valve would need a larger seat. Though there is suggestion that the 2.8 seat can be machined to suit.
Having a hard time wrapping my head around how a larger valve would be of any benefit if the seat and port diameters aren't enlarged to acomadate.
Bob

 

[sd_pace]

when the 2.9 seat are cut there is a lot of excess that needs to be cleaned out to open the throat . I had the machinist cut the holes first so I could grind them out, then took it back to have the seats put in. just dont go to deep and hit the water jacket

 

[61Alpine]

I have a 2.8 engine in my #2 Alpine.
I had my matching shop put the crank from a 2.9L and the valves into my 2.8L

It has been about 8 years since the work was done and I have been stalled on the project since, so I have not run the engine yet but this year it will run.

So yes you can put 2.9L valves into a 2.8L according to my machine shop.