Whats a 3 angle valve job? Whats unshrouding? Im fixing to have my heads ported and want to know this before i go.

 

A 3 angle valve job has 3 angles cut in the head.
The 45deg valve seat, a 60 degree cut under it and a 30deg cut above it. A "bowl cut" of 73/85deg below
these 3 angles helps open up the bowl.

Some machine cutters actually cut a multi angle radiused
seat all in one operation. More and more shops are using these valve seat cutters now.

The valve may or may not have multiple angled cuts on it too, besides the 45deg seat angle. A 30deg back cut angle is typical.

Other angles are used but these are typical.

Deshrouding or unshrouding refers to cutting back and blending the combustion chamber walls in certain specific areas to allow air to flow efficiently between the new larger valves and the chamber walls.

A good series of books that will help you under stand this and more about modifing cylinder heads for hiperformance use is By David Vizard. One title is: How to Build Chevy Small Blocks on a Budget. This and much more is covered in this book.

You can get these books online at Amazon.com or from many well stocked Speed Shops. Best $10 you'll spend on going fast.

 

Seat cutter

 

Deshrouding a 305 head for larger valves.

 

Thanks alot! youve got some experience in 305 heads dont you? B/c im fixing to do a 350 reduild and i want to use my heads. If had them worked will the work on a 9.3:1 350 rated with 64cc heads? Will i need the 3 angle job and some unshrouding?

Can you do alittle narration on the unshrouding?

 

Yes they will work.

Read my past posts on porting heads. And buy David Vizards book(s).

You'll want to install new larger 1.94x 1.60 valves so you'll need a new valve job ( machine shop).

Yes a 3 angle valve job is the way to go.

 

with a 3 angle valve job (or any porting for that matter) do you need to get new valves? can you just port your heads and put all your old stuff back on?

 

anyone?

 

If it's still good, you can re-use it.

If you go to the trouble of porting heads, it's worthwhile to get valves that will also help flow; ones with undercut stems and various other more subtle forms of streamlining. You can get them from any number of mfrs, including Comp, Manley, Lunati, etc.

If you're not going to do the port work yourself, I'd suggest Hyperformance in Atoka, just off of Hwy 14 and just into Tipton County.

 

Umm, I read a 3 angle valve job is 2 angles cut in the head, 1 angle cut in the valve, and a 5 angle valve job is 3 on the head 2 on the valve.

Clarify?

 

You may have read it; but somebody wrote wrong.

A 3-angle job is 3 angles on the seat. Usually something like 30, 45, 60. There's usually only one on the valve, usually 44, although on a really premium job, people will radius the edges of the cut, and either back-cut or radius the valve margin too.

The one-step radius cutters are real popular these days. They're making old-fashioned 3-angle ground jobs obsolete. They do a better job, for cheaper than a cheap grinding job.