Do you think I will have any issues with these heads on a stock 346 cube?
I am going to order these along with an MS4 cam.
I am mainly concerned with the valve size. I want to ensure they are not to big. My original plan was to go with 7.350" pushronds to compensate for the .005" milling on the heads.

 

That's probably a good choice, if they're milled, you'll probably have to flycut your pistons though.

 

That is the second time someone told me this. They are milled .005. Can't I make up for this with maybe a shorter pushrod (7.375) or a .040 thick gasket?

 

I am pretty much going to do what they did in this article. They didn't mention anything about flycutting.
http://www.gmhightechperformance.com...onclusion.html

 

ME personally... i'd cut them. IT's like $200 of insurance.

 

Can you explain why you would cut them? This is what I am still trying to understand. I am a bit confused. Is it because the piston might hit the head?

 

No, the valve might hit the piston. This is what happens when that happens...

 

Ah I see. So TSP mills them .005 and they don't account for this?

 

Honestly, i dont know know all the tolerances, as far as how much is to much and what you can get away with. All I know is you dont want a valve hitting a piston.

 

IN the article they used Stg 1 heads. Those heads do not require flycutting. You want to purchase Stg 2.5 heads which are milled. They mill the heads for smaller combusion chambers. Flycutting is something the builder needs to figure out because of endless possibilities with camshafts. With the size of the MS4, it will require flycutting.

 

Correct me if I am wrong but the Stage 1 heads are milled as well unless I am reading it wrong.

The last sentence in the first paragraph.
FWIW-
* 7.400" = 187.96mm
* -7.350" = 186.69mm
____________________
* 0.050" = 1.27mm

Head mill of .005 = .127mm

Wouldn't they be safe not flycutting and still going with a 7.400" pusrod?
The gasket should cover the difference and not hurt compression right?

 

My stage 1's came milled .015.

 

Not to sound like a dick, but call TSP or email them and ask.....They have all the answers, they made the stuff, so they know what goes well with what, and what needs grinded, or cut and what gaskets to use......

 

PRC Stg 1 uses stock size valves 2.00 / 1.550

PRC Stg 2.5 uses 2.04 / 1.575

 

this is where the problem is. the ms4 barely squeaks by with stock sized valves. theres no way that it will fit even if the heads werent milled.

 

IM not sure about the milling of the Stg 1s. As far as I knew they had only a CNC job and upgraded springs with all the goodies. I got them because the MS4 would fit without flycutting and they are a great price. Today TSP offers a valve upgrade for those heads. Those valves will defiantely require flycutting the pistons with the MS4.

 

The stage 1 has extra clearance built into the head allowing us to deck them 15 thou & still give better than stock p/v. That being said the LS6 2.5 heads have less p/v than a stock head. As a result we typically ship the stage 1 with the ms4 camshaft. Honestly with all the results I've seen I like the stg1 heads a lot when combined with the ms4

Jason
Texas Speed

 

Thanks Jason.
I will ordering them today.
It sucks because I want the stage 2.5 because I will be adding a Procharger next year but don't feel comfortable milling the pistons.
Can you do stainless steel valves on the Stage 1?
I will try to give you guys a call today to order everything.
You sent me an estimate awhile ago jason.krivda@maab.centaf.af.mil

 

I'd go especially go with the "stage 1" heads if you are planning a supercharger. Once the air is twice as dense, airflow becomes more trivial.

Ben t.

 

I was more worried about heat.