Oversized Engine builder valves

[1930]

Can someone tell me if installing the engine builder valves is going to require having all new valve seats installed or is it just a matter of cutting what is there.

Also how will installing these valves affect my CC measurements. The head is 60 cc now but will installing these valves make that number get lower or higher?

Will there be any valve shrouding using these valves. I have read that the chambers will need to be swept/valves de-shrouded after their installation, any truth in that?

Im going to guess that installing the larger valves and then sweeping/unshrouding the valves ( if that were needed to be done ) would cancel out one another if bigger valves were to reduce chamber size at all but that is just an un-educated guess.

Thanks

 

[C130 Chief]

How much bigger are the oversize valves? On the intakes, if the seats have been resurfaced more than a couple times (or ground even once badly) the valves will end up recessed in the chamber which increases chamber volume slightly and hurts flow. Fitting an oversize valve will allow the valve to be "raised" back up in it's seat. Now if the valve is only a little larger, shrouding shouldn't be much worse that before. On the exhaust side you'll probably need insert seats. The original induction hardening on 72-later heads was only a few thousandths deep and could only ground away with a light cut. If the guides were loose and the seats were worn heavily, or the head was an earlier casting insert seats are the way to go.

Hopefully one of the slant gurus will have some guidance about fitting significantly larger (small block) valves,if that's what you are after.

 

[1930]

How much bigger are the oversize valves? On the intakes, if the seats have been resurfaced more than a couple times (or ground even once badly) the valves will end up recessed in the chamber which increases chamber volume slightly and hurts flow. Fitting an oversize valve will allow the valve to be "raised" back up in it's seat. Now if the valve is only a little larger, shrouding shouldn't be much worse that before. On the exhaust side you'll probably need insert seats. The original induction hardening on 72-later heads was only a few thousandths deep and could only ground away with a light cut. If the guides were loose and the seats were worn heavily, or the head was an earlier casting insert seats are the way to go.

Hopefully one of the slant gurus will have some guidance about fitting significantly larger (small block) valves,if that's what you are after.

• Thanks very much, valves are not much lager, I did not know about the induction hardening process so that is definitely interesting.

 

[RustyRatRod]

You can do the valve seats either way. What I would do is just machine out the intake seats but have hardened exhaust seats installed.

The chamber volume may be affected, but it will be a minute amount. Not something I would worry about.

The shrouding issue is a non issue, IMO. The valves are not THAT much bigger.

 

[1930]

You can do the valve seats either way. What I would do is just machine out the intake seats but have hardened exhaust seats installed.

The chamber volume may be affected, but it will be a minute amount. Not something I would worry about.

The shrouding issue is a non issue, IMO. The valves are not THAT much bigger.

Thanks very much rusty