Stock and oversize valve sizes?

[guhfluh]

I've been searching forever on here and neons.org for stock and oversized valve specs. I just finished changing the valve stem seals on a ported head I purchased and took a couple of the valves out for measurements. Evidently they are oversize, but I'm trying to figure out how much. I also took measurements of the stock valves I had laying around, but from what I found on the specs and what I measured, it doesn't match up. So, here's what I measured:

Stock:
34.84mm Intake <--True to the spec I found
29.42mm Exhaust <-- 1mm over the spec I found

Mine:
36.06mm Intake
30.52mm Exhaust

So are my intakes +1mm? (~+1.22) and my exhaust +1mm or +2mm?

Maybe I made a mistake in measuring the stock exhaust?

And another thing I forgot. What vendor uses REV valves? The intakes are backcut, like DCR advertises, but the exhaust aren't...

[Fischy]

Quote: Originally Posted by guhfluh

So, here's what I measured:

Stock:
34.84mm Intake <--True to the spec I found
29.42mm Exhaust <-- 1mm over the spec I found

Mine:
36.06mm Intake
30.52mm Exhaust

Are my exhausts +1mm or +2mm?

30.52 - 29.42 = 1mm oversize aprox.

I'm using stock diameter intake and +1mm exhaust. The valve job guy (at Valley Head SoCal) mentioned that going +2mm on the exhaust valves would be a stretch.

[guhfluh]

Well, I've concluded that I have +1mm intake and +2mm exhaust REV valves and I have no idea if the intake or exhaust are backcut, as I don't know what I'm looking at.

From what I can see, the intake stem is cut down some, but not the exhaust, but I don't know what the process is called

[a853rox]

Quote: Originally Posted by guhfluh

Well, I've concluded that I have +1mm intake and +2mm exhaust REV valves and I have no idea if the intake or exhaust are backcut, as I don't know what I'm looking at.

From what I can see, the intake stem is cut down some, but not the exhaust, but I don't know what the process is called

Pics?

Rev valves are not back cut from the factory but some Ferreas are (depends on the series). Although both generally will stamp/label each valve on the stem above the lock....

The skinny stem before the valve face is called a "necked down" feature that promotes better airflow by reducing the stem diameter where it is not needed. Typically a good thing, but sometimes some shops can do this too far and compromise the strength of the valve. Rev and Ferrea both, have shown this does not weaken their valves though.

[guhfluh]

That's all I took when i had them out. I have a couple more from the top looking down, but you can tell anything from that angle.

They're labeled REV on the stems above the locks.

[a853rox]

Tough to tell from the pics if the intake valve is backcut, but I can clearly see the exhaust valve is not. Any good head shop should be able to do a valvejob and backcut if needed though. (I would recommend backcutting the exhaust side too)

[guhfluh]

Can you tell how many angles are on them/serdi or do you have to look at the head?

I'm just going to run it as is. I'm happy with the port job I see, the oversize valves and cams I have.

[a853rox]

Quote: Originally Posted by guhfluh

Can you tell how many angles are on them/serdi or do you have to look at the head?

I'm just going to run it as is. I'm happy with the port job I see, the oversize valves and cams I have.

Neck down, valve angle, and back cut, are all features of the valves themselves, and can be measured (30 degree backcut, 45 degree valve cut, ect).

The number of angles of a valve job refers to the seat side of things. If it's referred to as a "3-angle" valve job, it may have a seat with 30, 45, and 60 degree seat cuts in it. often times there are more angles like 5 or 7 in a seat, and some of the best are either hand blended, or cut with a profile cutter and use a full radius for improved flow (generally on the exhaust side but can be either).