Stock lower end smog pistons with 781 heads

[Turbo4whl]

Are they the original heads you are reinstalling? Big block's could have used three different diameter push rods. The push rod guide plates need to match the push rods.

Also, if they are early heads, they will not have flame
hardened exhaust valve seats. Using today's unleaded fuel, the seats will burn as previously stated. Any thing made pre '73-'74 will not last long if you do not machine and install hardened seats.

 

[buddy350]

WOW

Thank you all.
I really appreciate the knowledge. Have read everything about 3 times now. LOL
Such good advice.

The exhaust valves on the 290 heads appear to have some type of coating on them, Some of the coating is gone.
The valve springs in the 290 heads were a little taller once removed from the heads than the ones out of the 781 heads.

The valve springs from the 290 heads had 3 shims per spring and the 781 heads only had 1 shim on the exhaust spring and a type of rotary disc on the intake or was it the exhaust had the rotary shims.

 

[bucket]

Normally the exhaust side has the valve rotators. Some later engines have rotators on the intake and exhaust sides. Comp Cams sells rotator eliminators if you want to ditch them for better valvetrain stability. They are basically just hardened steel spacers that have a lip to locate the base of the spring.

 

[Salty Crusty]

Those 290's are "semi-closed" chambers, they'll work very well. They're worth money, though, to people trying to restore muscle cars. The LS5 from back in the day had those and if cammed right, would outrun the square port "race" engines, much to the dismay of the LS6 owners!
But...you'll make just about the same power with the 781's because the 290's shroud the valves a bit. They can be reworked with a Serdi to unshroud the valves but you'll have to mill the heads to get compression back up.

 

[MikeB]

What's the reason for studs? A good set of bolts will do just fine.

If you do use studs, remember that they have virtually zero torque on them, so be sure to use ARP thread sealant to keep coolant from leaking past.

Also, run an old tap or thread chaser through all the holes, regardless of whether you use bolts or studs.

One more thing: I don't know about our trucks, but with some engine compartments there is no room to remove a head up and over studs, even with a small block!

 

[idahovette]

Good call MikeB, never even thought about pulling the head OVER the studs! Would be very tough to do in some instances!!