What a Predator 212 Actually Makes: The Dyno Sheets

Harbor Freight sells the 212 as a 6.5 horsepower engine. Kit sellers advertise 9, 14, 16, 20. Almost none of those numbers came off a dyno, and the ones that did rarely say what correction factor the dyno used — which on a small engine is worth a few percent all by itself. So this page uses one source: Red Beard's Garage, whose Road to Horsepower series runs every configuration on the same dyno and prints the sheets, corrected to 29.92 inches and 60°F. That is the standard reference, and it is the same basis this site's simulator reports.

Stock: 6.7 hp

Predator 212 Hemi, throttle stop screw removed, 30-minute break-in, stock carb, stock muffler. 6.74 hp @ 4,400 / 8.40 lb-ft @ 4,100 (Episode 2 sheet; Episode 1's three-run average was 6.67 / 8.25.)

Harbor Freight's 6.5 rating is honest. Note the rpm: with the throttle-stop screw out but the governor otherwise in place, the engine pulls to about 4,700, and peak power arrives at 4,400. A fully governed engine at 3,600 never sees its own peak — that is why the "stock" result in the calculator depends so much on which governor option you pick.

Stage 1: 9.1 hp

Same engine, GoPowerSports Stage 1 kit — pod filter and adapter, jet, header with muffler. 9.11 hp @ 4,700 / 10.94 lb-ft @ 4,100 (Episode 2; Episode 1 averaged 9.03 / 10.96.)

That is +2.4 horsepower and +2.7 lb-ft for the cheapest kit on the market, on the stock cam, with the governor still in the engine. The Stage 1 kit is the best money you will spend on a 212, full stop, and the reason is simple: the stock air filter and muffler are sized for noise and dust, not airflow, and the stock jet is sized for the stock filter.

Open header: 8.7 hp — less than the muffled header

Stage 1 kit, muffler removed, header run open. 8.70 hp / 10.79 lb-ft — a 3.65% loss against the same header with its muffler on.

This surprises people every time. A small single-cylinder engine wants a tuned exhaust length, and the header-plus-muffler kit is that length. Cutting the muffler off makes it louder and slower. The simulator treats "straight header (open)" as a small loss against the header and muffler kit for exactly this reason; the header page runs the exact number for your build.

Governor delete, stock cam: 8.9 hp

Stage 1 kit, governor removed, ARC billet flywheel (+8° timing), 18 lb valve springs, throttle plate, stock cam. 8.90 hp @ 5,500 / 10.01 lb-ft @ 4,100, sweep to 7,200 rpm.

Compare that to the governed Stage 1 sheet above: the same horsepower and one lb-ft less. Pulling the governor and adding the flywheel and springs let the engine rev to 7,200, but the stock cam has nothing to give up there, so the peak just moves from 4,700 to 5,500 without getting any bigger. Red Beard's conclusion on camera was that there is no real point in doing the governor kit without doing a rod and a cam at the same time — and the sheet backs him up. This site's governor page and the rod guide say the same thing.

What the 10, 13, and 15 hp builds on this site are

Those three pages are simulator combinations, not dyno sheets. They are built from the four anchors above plus published cam and head specs, and they are labeled as estimates because that is what they are. Nobody has yet put a DynoCams 275 or a ported head on Red Beard's dyno with the sheet on screen; when someone does, the numbers get checked and the pages get fixed. Until then, treat the 10-hp build as very well anchored (it is Stage 1 plus a little), the 13-hp build as reasonable, and the 15-hp build as the least certain of the three.

Reading the ladder

• 6.5–6.7 is a healthy stock engine. If yours reads lower on a dyno, check the throttle stop and the break-in, not the engine.
• 9 is Stage 1 with the governor in. Anyone can get here for the price of the kit.
• 9 with a governor delete is where the money starts being wasted. Do not stop here.
• 10 to 15 is a cam, springs, a rod, and a carb — in the order that works — and it is the part of the ladder the simulator is for.

Build the stock engine in the calculator, set the governor option to match your engine, and add the Stage 1 kit. If your calculator number and the sheet above disagree by more than a few tenths, tell us — that is what the contact page is for.

Sources: Red Beard's Garage — Road to Horsepower Ep. 1 (tQjitfEMDxM) and Ep. 2 (vaL4-d5Fz70), inertia dyno, corrected to 29.92" / 60°F. Harbor Freight's 6.5 hp rating. Kit-seller horsepower claims are not used.

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