RHS 200cc iron heads with 50cc chambers

[travis]

I picked up a new set of these bare from Gary C, and am about ready to start building. I need to order valves…don’t these typically use a +.200” valve? I’m thinking somewhere around 1.800-1.850” installed heights.

I’m planning on using these on a 10.5-1 or so 385” sbc that peaks around 6200-6500 rpms. They are cut for 2.02/1.60 valves…do I want 2.055’s or 2.08’s? Will those even fit within the chamber?

[BillK]

Can you borrow a couple of valves to get an initial measurement ? Thats what I would do but I have a ton of valves sitting around to try. Would be annoyed if I took somebody's word for it and ordered valves and then had to return them fir the correct ones.

[F-BIRD'88]

Be aware that if the small 50cc chamber volume was achieved by milling the head the VTP clearance will be a lot LESS than another typical sbc head.
Something to check.

[skinny z]

…don’t these typically use a +.200” valve? I’m thinking somewhere around 1.800-1.850” installed heights.

FWIW, my iron RHS Pro Torker Vortecs use a .100" longer valve.

[travis]

Be aware that if the small 50cc chamber volume was achieved by milling the head the VTP clearance will be a lot LESS than another typical sbc head.
Something to check.

I’m assuming the factory achieved a 50cc volume by milling a 64cc head, but I don’t know for sure. Since I’m going to have to use an approximately 30cc dish piston, I don’t “think” ptv clearance will be an issue

[F-BIRD'88]

I don't know if on those heads if they mill down a 64 cc casting or modify the location of the chamber closer/shallower to the deck.. That would explain the longer valves thou. Reguardless, the valves do get closer to the piston.

[steve cowan]

I picked up a new set of these bare from Gary C, and am about ready to start building. I need to order valves…don’t these typically use a +.200” valve? I’m thinking somewhere around 1.800-1.850” installed heights.

I’m planning on using these on a 10.5-1 or so 385” sbc that peaks around 6200-6500 rpms. They are cut for 2.02/1.60 valves…do I want 2.055’s or 2.08’s? Will those even fit within the chamber?

Valve length in my opinion will depend on flat tappet of roller cam,spring stack etc.
Seat pocket and valve seat,
I am using std length valve 600" lift roller with -0.050" locks with shim under spring.
Installed is 1.795" but its on coil bind
I would like a set of those heads

[GARY C]

Be aware that if the small 50cc chamber volume was achieved by milling the head the VTP clearance will be a lot LESS than another typical sbc head.
Something to check.

I’m assuming the factory achieved a 50cc volume by milling a 64cc head, but I don’t know for sure. Since I’m going to have to use an approximately 30cc dish piston, I don’t “think” ptv clearance will be an issue

Based on the deck thicknes I don't think they mill to get the small chamber.

An 11/32 stem 5060 valve will give you about a 1.93 install height with a hardened shim only, so you can reduce that with a cup and shims or a shorter valve.

[GARY C]

I picked up a new set of these bare from Gary C, and am about ready to start building. I need to order valves…don’t these typically use a +.200” valve? I’m thinking somewhere around 1.800-1.850” installed heights.

I’m planning on using these on a 10.5-1 or so 385” sbc that peaks around 6200-6500 rpms. They are cut for 2.02/1.60 valves…do I want 2.055’s or 2.08’s? Will those even fit within the chamber?

Valve length in my opinion will depend on flat tappet of roller cam,spring stack etc.
Seat pocket and valve seat,
I am using std length valve 600" lift roller with -0.050" locks with shim under spring.
Installed is 1.795" but its on coil bind
I would like a set of those heads

Kim Barr Racing in Texas has a bare set, probably let them go cheep, I just don't know what shipping would cost. His number is 972-272-6121

[steve cowan]

I picked up a new set of these bare from Gary C, and am about ready to start building. I need to order valves…don’t these typically use a +.200” valve? I’m thinking somewhere around 1.800-1.850” installed heights.

I’m planning on using these on a 10.5-1 or so 385” sbc that peaks around 6200-6500 rpms. They are cut for 2.02/1.60 valves…do I want 2.055’s or 2.08’s? Will those even fit within the chamber?

Valve length in my opinion will depend on flat tappet of roller cam,spring stack etc.
Seat pocket and valve seat,
I am using std length valve 600" lift roller with -0.050" locks with shim under spring.
Installed is 1.795" but its on coil bind
I would like a set of those heads

Kim Barr Racing in Texas has a bare set, probably let them go cheep, I just don't know what shipping would cost. His number is 972-272-6121

Gary,
Would cost me an arm and a leg for sure,I like the idea of a small chamber like that,possibly get close to 12.0:1 comp with flat tops
PS - I purchased a GZ vac pump 12 months ago the kit was approx $800 US
By the time it landed on my door it was $2400 AU and took 3 months to get here lol.

[rustbucket79]

The chambers are small because they are angle machined (milled). IIRC the valve angle is in the 21 1/2 degree range rather than stock 23 degree angle.

Beware the potential for valve pocket depth, floor angle and potentially location issues with many shelf pistons. These are NOT a bolt on and go head, you had better be damn certain you’ve done all your verifications because valves hate being punched by pistons.

[GARY C]

Valve length in my opinion will depend on flat tappet of roller cam,spring stack etc.
Seat pocket and valve seat,
I am using std length valve 600" lift roller with -0.050" locks with shim under spring.
Installed is 1.795" but its on coil bind
I would like a set of those heads

Kim Barr Racing in Texas has a bare set, probably let them go cheep, I just don't know what shipping would cost. His number is 972-272-6121

Gary,
Would cost me an arm and a leg for sure,I like the idea of a small chamber like that,possibly get close to 12.0:1 comp with flat tops
PS - I purchased a GZ vac pump 12 months ago the kit was approx $800 US
By the time it landed on my door it was $2400 AU and took 3 months to get here lol.

I believe EQ still cast these heads in AUSTRALIA, is there not an outlet for them there or do they no longer cast the 50cc chamber?

[houser45]

Eq does not make the 50cc version.They did in the older casting years ago. With the new 200 cc iron head they came out with a few years ago they were going too but never did. They are made from the standard casting. 1.5 degree roll over before the head bolt holes are drilled and spot faced.

Valves are closer to the deck. piston to valve clearance will be tight with any race camshaft.


The Rhs casting i believe was made the same. good heads. I had some porosity issues with the newer Eq’s and I only use the Dart 49cc versions now.

Adjustable guideplates are a must on all of these if you want the valve train right.