MHS StockMod heads are non ported PI heads with performance modifications.  We take stock seasoned PI head cores and install our custom manganese bronze guides with ultra tight valve stem to guide clearances to improve both oil control and allow an improved performance valve job to be done.  The stock head has double to triple the valve guide clearance and thus you have to make the valve job much lower performing.  We go from the stock 3 angle valve job to a performance 5 angle on the intake which includes tightening of some of the angles and widening of the others to enhance the flow.  We also will bowl port the short side radius of the intake port if desired (no cost extra).  Flow gains from 2-10CFM are found this way.  This is the perfect head for those on a budget, and for those in a race class that does not allow porting.

Options:

Bowl port the short side radius of the intake port - FREE

Modify stock intake valves for larger cams - $50

Install 0.5mm oversized SS intake valves - $100

Install 0.5mm oversized SS exhaust valves - $100

Install a set of Pacaloy Stage 2 0.600" lift valve springs - $150

Install Comp high load valve springs for turbo applications - $250

Install Timeserts for spark plugs to all 8 cylinders - $150

Send us your valves or valve springs to install in these heads - no charge

Include a new set of OEM Ford exhaust studs and bolts - $75

Assemble heads/cams/rockers with rebuilt OEM lash adjusters - $200

Mike at Turbocharged Innovation just went 11.17 at 129MPH with a crappy 1.88 60ft and 102MPH in the 1/8 in 85 degree weather.

Here is a video of this run.

Car is a 3680lb 99-04 style Mustang with the prototype original heads (which would end as a Stage 1 with a 0.5mm valve and Comp high load spring option), stock PI cams and intake, stock auto, stock 3.27 rear, aftermarket 3000 stall converter, and his turbo setup.  The rest of the car is amazingly stock.

With a restall of the converter so it can be in boost off the line and some weight savings high 10's at over 130MPH should be realized.  Then I might be able to talk him into some cams finally.........

UPDATE - Ryan just went 10.9@134MPH with our 600RWHP combo in a full weight vehicle!

I have an amazing supply of Romeo cores for dirt cheap for hopefully the next few years that have never had a reject.  I pass that pricing on to you.

With a 4.6 sized engine 210CFM will support approximately ~7500RPM naturally aspirated before more CFM even needs to be considered according to the established "calculators".  You need a real intake manifold to achieve this as well as the stock plastic intake manifold won't allow much over 200CFM and 7000RPM anyways.

Our heads are designed for stock manifolds, or headers with 1 5/8" tubes since that is what most of you use.  Most flow numbers are done with 1 3/4" tubes and the ports are taken to that larger size to "fluff" a higher reading.  When that larger port gets used on a typical 1 5/8" header the flow typically drops lower than what ours have as you now have a serious mismatch in the worse possible location.  1 5/8" headers are used on 8000+RPM 2V engines, you need to pull some serious RPM before even considering 1 3/4" headers. 

28 inches and stock bore diameter of 3.55"  Larger bore diameters will flow slightly higher numbers.  Some of the other heads out there are flowed at the stock diameter and some at larger diameters, be sure to check when comparing.

Quite simply that is not where the restrictions are!  The restriction on the intake is in the middle of the port and the exhaust is in the bowl and the roof by the guide. 

Chamber shrouding primarily from the slightly larger valves.  These are small bore engines with small compact combustion chambers.  Once the valve moves far enough away from the seat the larger valve itself finally becomes less of a restriction rather than a greater restriction.  The flow charts are also done with a stock bore diameter, a larger bore diameter will favor the larger valves.

Powdered metal works good for valve seat material, and it works decent enough for valve guides.  However all it takes is one PTV issue and that powdered guide fractures easily.  Then it becomes a tiny fragmentary grenade inside your motor.  I have seen enough motors damaged from cracked and fragmented powdered guides to where I don't use them.  Bronze guides also absorb heat from the valve better and transfer to the aluminum head casting better.  Bronze is a much better conductor of heat than powdered metal.

We just got back one of the first sets of heads I had ever done.  It survived 30,000 miles of abuse via 20-25lbs of turbo boost.  The guides had increased clearance by 0.002"  Since we install the guides at such a tighter spec than OEM, these heads came back still within OEM specs (but at the high end)  The stock powdered guides that I have removed are usually 0.010" larger under similar conditions.

It is done on a CBN Rottler.  You need a super smooth finish for the MLS gaskets and many shops do not have the correct equipment for this.

PI heads get 5 angles on the intake, 3 angles on the exhaust if a StockMod, and 4 angles if one of the ported series.  We will do different things to the valve job if the application is a high boost blower or turbo.  All valve jobs are not the same, there is much more to it than just the number of angles.

$100 once they arrive to me.  I will send your cores back to you ported.  I do not swap them for another set unless you desire that (like Romeo and Windsor exchanges - we are always looking for good Windsor cores)

Never touched a set so I would not be the best person to work yours over.   Since they are discontinued now is probably not the best time to starting learning them either.