What am I getting with a "Shredder" head?
TL:DR (the quick and dirty):
- +1 full point in compression at 18cc with no milling needed
- 25% increase in flow over stock heads verified on our flow bench
- Larger 28.5mm and 24mm x 5.5mm stem stainless steel valves compatible with aftermarket billet retainers and split keepers
- Heavy duty stamped steel rocker arms
- Stronger automotive style steel retainers and keepers
- 26lbs valve springs
- Intake flange accepts Mikuni, Nibbi, or other PZ style round slide carburetor
- Adapter is available for PWK D-slide style carbs.
Below is a spreadsheet comparing commonly available GX200 clone head flow in manometer readings with no corrections. These are NOT CFM readings and cannot be compared to other flow benches, they are only relevant to our flow bench. All heads in this comparison were tested under identical conditions, one right after the other on the same night, of course on the same bench. Higher numbers indicate higher flow, but are not necessarily linear. You can see that the Predator hemi gains nothing above .250" lift, so a 308 cam is useless for it, but the Shredder keeps gaining until over .300", so it can take advantage of a 308 or a 356 cam, and a Stage 1 will work even better at high lifts!
| Engine Designation | .100" | .150" | .200" | .250" | .300" | .350" |
| Loncin H225 hemi | 0.30 | 0.44 | 0.53 | 0.53 | 0.53 | 0.53 |
| Ducar 212 hemi | 0.25 | 0.45 | 0.57 | 0.57 | 0.58 | 0.59 |
| Predator 212 hemi | 0.25 | 0.45 | 0.54 | 0.59 | 0.60 | 0.62 |
| Predator 224 non-hemi | 0.32 | 0.56 | 0.64 | 0.66 | 0.70 | 0.73 |
| Predator 212 non-hemi | 0.23 | 0.47 | 0.66 | 0.70 | 0.75 | 0.79 |
| Northstar c225 | 0.28 | 0.68 | 0.70 | 0.73 | 0.77 | 0.81 |
| Wildcat WC946 | 0.38 | 0.67 | 0.77 | 0.81 | 0.82 | 0.83 |
| Shredder Stage 0 | 0.28 | 0.54 | 0.74 | 0.84 | 0.91 | 0.94 |
| Shredder Stage 1 | 0.31 | 0.63 | 0.92 | 0.96 | 1.03 | 1.08 |
All of this can be bolted on with our intake adapter and a suitable boot and carburetor for a full top end build. Think “head/cam LS” when comparing to stock. Okay, okay, maybe with a billet Stage 2 bottom end and a 308 cam, but this gets you halfway there in an hour of wrenching.
The details:
The Shredder head was a factory big valve sand casting built just for the 14hp DTV Shredder 208cc gasoline engine derived from the Honda GX200. In essence this engine is another clone, but it included some other nice-to-haves like an oil cooler, CDI ignition, charging coil, and 15ftlbs of torque. Its cylinder head was designed to work at all engine speeds below 6,000rpm with a small cam, so it works great as delivered with the popular .265 lift cams out there. If you know you are going to be removing the governor and going to stage 2, this head and intake are the ultimate stage 2 upgrades, and with porting you can keep using this head LONG after you’ve made more power than a D port die casting can ever make. Here are the specifics of what makes power with this head:
+1 point in compression - And that is with a 0.040” head gasket due to the smaller 18cc chamber. 0.010” gaskets will give even more.
25% more flow over a die cast stock D intake port clone head – The port floors in the Shredder head have more material in them and a gentler transition to the valve seat allowing more flow which means more horsepower. The bowl area and valve guide are also a HUGE improvement over the die cast heads. Port flow is not as much about perfectly smooth and shiny runners as it is about the overall shape of the runner and bowl area. Bowl, floor, short side radius, and transition to seat are all massively improved with this head.
Oversized stainless steel valves – The 28.5mm intake and 24mm exhaust valves are not only larger than a stock die cast head, but they are stronger too. You don’t need to order a built head with stainless valves because this one already has them for you. These valves have the standard 5.5mm stems and are compatible with available aftermarket billet retainers and split keepers, so you can keep using them even if you go to dual valve springs.
Automotive style steel spring retainers and split keepers – Just like some of the newer engines, this head comes with automotive style steel retainers and split keepers. This system of valve control is far superior to the lawnmower style slide-in retainers for better valve control at elevated spring rates and engine speeds. It’s another thing included with this head that you don’t have to spend time and money buying elsewhere. You might need aluminum retainers if you intended to rev to 7500rpms with the 26lb springs this head comes with.
26lb valve springs – This head comes with 26lb valve springs installed from the factory. You won’t need to upgrade unless you are going beyond a .265” lift cam and/or 7500rpms. If you like, you can upgrade to billet aluminum retainers with no other changes and just a valve spring compressor tool, or throw in some dual springs and explode with rpms because the valves will work with them too.
Can it be ported?
Yes, most definitely! This casting weighs double what a diecast D port stock type head weighs, so it has a lot more material in the casting that can be cut away to form the proper aerodynamic shapes. This is also where this casting excels because it has more material between the port floor and valve seat on both intake and exhaust runners, which is the Achilles Heel of the older D port style die castings. We need to make clear here that ported D port style die castings cannot, and will never, flow mod for mod, as much as this sand cast Shredder head because of their flat port floors and their resulting short side angle (it’s sharp!), not radius, and a lack of enough material to fix it correctly. It doesn’t matter how large of a valve you put in the die castings, because of the lack of any effective short side radius they will never flow what the Shredder can with porting and big valves. Because this material is present in the Shredder head you can cut a properly broad short side radius that allows much less separation on the floor and balances the charge velocity between the floor and ceiling where it is critical in the bowl and seat area, greatly increasing flow by reducing turbulence.
What’s the wait time?
There is no wait time for in-stock parts. Ported heads might take a few days longer, but we may go ahead and have some off the shelf big valve combos available as soon as our valves and other parts come in. It is important to note that because of the available flow of stock Shredder heads they can support around 15hp. You don’t need a big valve ported head unless you are making more power than that.
Will this bolt right up to a non-hemi 212?
Yes, but you’ll need offset dowel pins to get it centered correctly. The stock head dowel pin size for a non-hemi Predator is 11mm, but this head fits the hemi block style 10mm diameter dowel pins. The dowel pins are important because they prevent the head from moving before, during, and AFTER the head is torqued to the block. With 10mm diameter dowels in an 11mm block you can see as much as 0.040” movement per side, and that is HUGE. Here is a link to our stepped dowels that will allow you to bolt a Shredder head onto any clone block. Sold in pairs here:
Stepped Head Dowel Pin Set - 10mm to 11mm
This head will bolt up to any of the 70mm bore blocks with 10mm dowels such as 212 hemi, 223, 224, or 225 engines out there.
Depending on your block's deck height the 5.260" pushrods should work fine, but always check your geometry during mock assembly. If you are using one of our tall deck blocks you will need 5.370". Again, always always check your geometry.
Will this bolt onto a Predator 212 hemi?
It sure will, and it works perfectly! Going from the worst flowing clone head to the best flowing has got to be awesome, right? If you're using a stock rod you can use a 0.010" thin head gasket and if your piston is at zero deck you should use a 0.040" head gasket. Pushrods need to be around 5.200" in length, but always check for the perfect fit.
What intake manifold do I need for this head?
We have intake adapters for both round (PZ and PE) and flat (PWK) Mikuni style carburetors available on our website that are specifically matched to the stock port diameter of the Shredder heads. PZ style adapters can have a carburetor bolted directly to them with the included studs and nuts, PE and PWK style carburetors can use the 33mm diameter red boots and clamps from Amazon, and our intake has retaining channels cut into it for a good, firm hold on the carburetor.
Why doesn’t your intake manifold have a pulse fitting on it?
Because most pulse pumps have a vent hole on the top that creates a massive vacuum leak when connected to the intake manifold. We have used pulse pumps for years and never had an issue using the governor boss on the top of the block for the pulse signal.
What size pushrods do I need for the Shredder head?
We have found the best geometry using stock length wedge (non-hemi) head pushrods for whatever block you are using. We always recommend chromoly pushrods and a billet guide plate for all applications.
Non-Hemi Predator block w/ Shredder: 5.260”
Hemi Predator block w/ Shredder: 5.200”
BBC Tall Deck 70mm Block w/ Shredder: 5.370"
**always check this with your rockers, followers, cam, etc during your mock build**