Creating this thread for pure discussion regarding these heads on a 5.7 or 6.0. On the RHS website, they boast that these heads provide up to 100 bolt-on horsepower over stock and feature all the benefits of other RHS LS7 heads. Again, simply creating this thread to get opinions on these heads. I would imagine these would be a great set of heads if you were trying to create an absolute max effort 5.7 or 6.0 and would be killer paired with a big/aggressive cam, and possibly an intake like a Super Victor. I don't imagine that anyone on here is running these heads on a small bore, but could be wrong. I know the RHS LS7 heads for a big bore motor are pretty killer, and Chris Frank has a program for them, and stated that the RHS LS7 heads picked up quite a bit over the MAST 305cc heads.

 

What's the runner size on the small bore heads?

I would think these would work well on a 402/408 depending on the runner size.

Also, with LS3 rockers and use of the LS7 intake... it should scream. The FAST LS7 is better than the FAST LS1 intake.

I could see on a max effort 346, well over 500rwhp and an LS2 or 6L probably something in the 530+ rwhp range. Maybe even more.

 

Looks like 266cc. Here is more information about them.


Finally, LS7 Heads for Small Bore GM LS Blocks (LS1-LS6-LS2) are Available

RHS® Pro Elite™3.900" Bore LS7 CNC-Ported Cylinder Heads not only get the best LS rectangular port heads onto all GM LS 5.7L – 6.0L blocks, they also provide up to 100 bolt-on horsepower over stock and feature all the benefits of other RHS® LS7 heads. These new Pro Elite™ cylinder fit all LS applications down to the 3.900" bore, and utilize LS7 intake manifolds. Offered in CNC and P-Port (unfinished runner) versions, the heads’ intake ports are raised .220" from the stock location for a straight line of sight into the cylinder, and utilize the LS 6-bolt head design compatible with the RHS® LS Race Block and GM LSX Block. They can also be used with OEM, 4-bolt blocks. Additionally, a .750"- thick deck surface and reinforced rocker rails make for more rigidity in high horsepower and boosted applications. RHS® Pro Elite™ 3.900" Bore LS7 CNC-Ported Cylinder Heads are designed to use eight standard, LS1-style exhaust rockers and eight offset LS3-style style intake rockers and stands. Buyers will save money, as they won’t need to order a full set of less common 1.8 ratio LS7 rockers.

•Includes (1) bare 355-T6 aluminum CNC cylinder head


•CNC-machined intake & exhaust runners as well as combustion chambers


•Intake ports raised .220" from stock location for strait line of sight into the cylinders


•FIt LS Blocks down to 3.900" bore - Perfect for 5.7-6.0L (LS1/LS6/LS2/LQ4/LQ9) block equipped applications


•Uses (8) LS3 offset intake rockers & (8) LS1 intake or exhaust rockers OR (8) LS3 exhaust rockers over less common/more expensive LS7 rockers


•Will work with standard 4-bolt OEM LS blocks or aftermarket 6-bolt blocks (RHS® LS Alum. Block & GMPP LSX)


•.750" thick deck & reinforced rocker rails make heads ideal for high HP & boosted applications


•Set-up for 2.100" intake & 1.575" exhaust valves

 

It's a really interesting head IMO. There isn't a lot of info on them out there and Comp/RHS tech. dept. hasn't replied to any of my emails inquiring about them.

 

266... yeah I'd definitely put these on a 402.

I could see 550-575 on a 402 with 2" headers, FAST LS7 102, and a camshaft like the Striker from Ragin Racing... 244/256 110+4... it would fly. Hell, the Striker on an otherwise stock LS7 with all the goodies hits 570/515. And these heads have similar runner size but probably flow better even on the smaller bore, so the difference in bore and the 25 cid difference becomes moot. Add the FAST to that number... this could be close to 600rwhp on a 402.

Hmm...

I imagine these use 3/8" pushrods as well. Which is good.

 

I think the interesting questions are:
1) what is the cross sectional area of the ports?
2) what valve timing is optimal for these assuming they are a high RPM head given what we assume is an obviously large cross section?

I'm interested in them and I've seen alot of speculation on how much extra volume the runners have due to the raised ports, but if one just measures cross section and compares it to know alternatives, then that is a pretty good starting point which is independent of extra runner length.

If they can be used on a 5.7 with cam timing similar to a small bore LS3 style head then they could be a good option for more dedicated max effort type builds.

 

I would use LS7 cam timing for it, which is much closer to LS1 than LS3. At least as a starting point.

And if the runners are close to stock LS7 size, I'd definitely want these on an LS2 stroker. The LS7 is already a pretty higher RPM head on a 427. I wouldn't want to go too much smaller. And I'd put an LS7 type cam in there that's proven to make power with the LS7 head with a 4" stroke.

 

That's a big valve and big port for a 5.7 though. Valve timing will have to account for that with optimal overlap as with the small bore LS3 on a 5.7. If it's a big cross section for a 427 then it's a huge cross section for a 346.

With for a bigger motor that has a larger bore, then well, what is the point of a small bore head?

 

Because you still can't run an LS7 on the LS2 or LS3 block either. And they are much cheaper than an LS7 block. Plus you could use the LQ4/9 block.

Or you could use a 383.

Remember. The LS2 is "small bore" too. These are said to work on the 5.7L, but I think they are intending these to be used more on the 4" bore LS2.

 

Understood, but the first sentence in the OP intends theoretical discussion on how to make it work on a 5.7 or 6.0. Not how to make it work on an engine which it will already work on.

 

I wouldn't try to run it on a 5.7L with a hydraulic setup. If you run a Super Victor, go solid roller. Spin to 8500.

 

all i know is if i bought a raised runner style head like this for 2500+ dollars i definitely wouldnt top it off with a choked intake manifold.

Single plane manifold chopped and shaved to hell with a few pounds of puddy in the bottom should do the trick.
Or maybe a ITB manifold of somekind.

 

I fully agree with you there. Single plane Super Victor would be the only way to roll if someone did go with these heads on a 5.7 or 6.0. Hell, these are max effort heads, so might as well throw a max effort intake on there as well.

As far as using these heads on a 402 or 408, or hell, even a 416, wouldn't you just step up to these? Post number 5 from Chris is a pretty interesting read.

http://www.yellowbullet.com/forum/sh...d.php?t=633426

 

I took a good long look at these before deciding on the Mast small bore ls3's.

The runner cc doesn't dictate everything to me, but 240 vs 266 is pretty substantial, even with the relocated valves.

Honestly RHS heads never have impressed me. Mast has proven results, and the casting itself is immaculate.

As for Chris's statement, there's even things he can do to Mast heads to get more out of them. By the same token, so can Cary, so it's 6 of one and a half dozen of the other to me.

 

So would anyone care to guess how much power one could make with these heads on a 5.7 with around 12:1 compression, a pretty decent sized cam, and a Super Victor intake with 4150 TB?

 

I'd run a solid roller setup, 14:1 CR, C16, Super Victor... 550+

 

if you apply 1.6hp per cube it comes to roughly 550hp on a 5.7
the same 1.6hp per cube theory would approach 683hp on a 7.0

seems legit.

 

Could you run that same compression on e85? I think these heads would be really awesome on a 364ci with one of Kip's low lash solid rollers. Run it on e85 and go for as high of compression as e85 will allow for. Hell, that setup would make some really good power.

On the other hand, I do see people's point that it's kind of wasted on a 5.7 or 6.0. If you're going to put that much into it, might as well go for bigger cubes.

 

I don't know. I can't get it anywhere around here so I've never looked into it.

And you're right. The money needed for 8500 RPM would be better served in an LSX454 or something with even better heads.

 

I think if I were to build a LSx454 or bigger cube engine, the larger RHS LS7 heads that Chris does would be at the top of my list. What heads do you consider to be a better option for a 454 or larger cube engine?