SWATPARAMEDIC

I'm rebuilding an 02 24 valve engine to put in an 01 and was measuing the valves and clearance and the angles for the exhaust and intake valves are different. I was wondering if anyone knew why and could explain that to me.

Thanks.

first4age

I know valve clearance are ususally different between exhaust and intake. I thought it's because the exhaust valve is expose to heat (exhaust cycle) so it will expand a bit, as a result, it needs more clearance.

The angle of the valve as in placement? or as in seat angle? Gasoline engine seat valve is usually 45*.

Hercules

Exhaust valve is 45 deg and intake is 30 deg. The 45 deg exhaust angle provides a good compromise between durability and creating less of an obsticle to effect the velocity of the gases leaving the cylinder. The 30 deg intake angle is supposed to cause a more efficient mixing of the air with the injected diesel fuel as the air enters the cylinger. As for the angle in relation to heat, that goes back to the compromise between durability and flow velocity. Heat in relation to the valves is more a function of valve recession, or how far the valve is below the surface of the head when the valve is fully seated...ie. not open. You do not want the valve to be flush with the head. The exhaust is slighty deeper than the intake. I may be little off, but, I think the exhaust valve recession is .038 to .058 inch and the intake is .028 to .048 inch. I'd have to check the book to be sure because I've been bouncing back and forth between 12v, 24v, two generations of power strokes, and recently a couple duramax heads. I just check each time now just to be safe. Anyways, deeper into the head is safer. Shallower probably flows better, but, you are talking about a turbo charged engine. Anytime I do a valve job on any diesel head, I cut the seats so valve recession is usually about .010 deeper than the recommended upper range figure. So, if the upper limit is .058, I cut the seat for .065 to .068. The reason is after I surface the head, which usually needs about .007 to .010 removed to get it flat again, I end up back at the upper limit when done. If I'm a little deeper, that's OK, if I'm a little shallower than the upper limit, that's OK too. In the end, the valve is better protected from heat.

Oh, before I forget, recently, we've been cutting both the exhaust and intake to 45 deg in performance builds.

SWATPARAMEDIC

Ok, That makes sense to me. I appreciate taking the time to respond and help me out.

RTillery

Hercules, what part of the country do you work in? Is it a full engine machine shop? What kind (brand) of equipment are you using? Just curious as I have been around a lot of machine shops and engine rebuilders. Thanks!