At what point does it make sense to go to a 1.90 intake and 1.610 exhaust valve? Getting ready to have my standby heads ported and wondering if there will be much of a difference in oversize valves with my current setup.

 

just about any twin cam build will benefit from 1.900 intakes.if ports & seat area are properly shaped,a 40-50 CFM increase can be seen which equates to big HP/TQ gains.make sure whoever is doing your heads the difference between porting for the bigger valves & not just installing bigger valves (which will gain almost nothing)

 

Don't want to have the heads ported with stock valves and then find out they should have bigger valves, then have to take them off and redone. Thanks for the post.

 

A chap called Des Hammill wrote a very informative book where he covered off a setup/design using larger intake valves.

The book is called "How to Power Tune Harley-Davidson 1340 Evolution Engines for road and track" (ISBN 1-874105-88-X)

I'm planning to use his porting theories on a spare set of heads I have lying around.

cheers

 

More air in+more air out=more power. Simplicity at it's finest. Talk to as many shops that you can handle, take notes, and then go with who will give you the best results to match your riding style.

 

When really looking for it, as far as big hp is concerned, age-old engine building info always refers to the intake valve size approx. 1/2 the size of the bore, and the exhaust about 75% of that.
Not only the valve size, but the shape of it, and how the seats are cut that can GREATLY enhance cylinder head flow.
Scott

 

Like it says I currently have the Andrews 26. If I go to another cam I do not want to have to pull the heads and do them again. Maybe an Andrews 37 at some point or higher ratio rocker arms for the 26? Looking at 81 or 82 cc heads when I am done.

 

Our 98"er's/Andrews 26/9.6 cr/Stage II heads will post 93-95 hp and 109-111 ft/lbs, carbed, with a Supertrapp 2/1.
Torque is usually all in by 3500.
Those VH pipes won't do you any favors.
Scott

 

Those VH pipes won't do you any favors.
Scott[/QUOTE]

That is on point

 

Ummmm..The thread is 2 years old matey!