Chevy valves swap into 242 head

[Goatboy4570]

Im doing a + 0.040" 80s vintage AMC 258 i6 / 4.2l (264) with the 242 head (7120 casting) swap right now, and im thinking Chevy 1.94 valves to save having to install new guides as i just have them reamed over to 11/32 . + i have valves on hand. My 40 overbore should help with clearance but im gona check that.

There’s still the business of springs, retainers, seals and installed height. My cam is going to be a lunati 256/262 with .484/.507 lift.

anybody out there done this swap or have knowledge any tips and help would be much appreciated.

 

[gutthans]

I did similar several years back. Heads got cut for Chevy springs, and I used off-the-shelf Z-28 single/damper springs (.500 lift max) as I ran the Comp 254-H. There are .525 sets available all around the web. The real issue will be unshrouding the valves if you go the 2.02/1.94 route. You'll HAVE to do a trial assembly of with one set. Just lay Play-Doh into the dish area of one piston and rotate it through a cycle with the head on. Cut the valve impression in the clay in half, remove one side, and and measure the distance to the floor of the dish area.

Your install height will be either 1.640 or 1.700 depending on the exact spring you select. Look for about 110-125 seat pressure and 262-292 open. Your valve float will be around 5700-6000 rpm at those specs I think, but that should be higher than you'll run it anyway.

 

[gutthans]

Oh, and I forgot to mention the head bolts...early 80's blocks had 7/16" while late '87 up uses 1/2" again. Your choice is to get 'centering washers' from Clifford or HESCO, or get your block tapped by the machinist for 1/2" bolts. If you don't do one or the other, there is a chance of easily misaligning the head on installation (and you won't know until the head gasket blows out...).

 

[caveman]

Jeep Strokers • Homepage
Lots of good info here. You'll have to do some searching.