Washburn’s Metal · Free tool
Engine Build CalculatorKnow what it'll make before you buy the parts.
For the air-cooled Volkswagen Type 1 engine — Beetle, Bus, Ghia and Type 3, from the 1200 up through the 2332 strokers. Pick a crank and a set of pistons and see exactly what you end up with — displacement, what the case needs, what rods it takes. Then add the cam, the carbs, the heads and the exhaust, and get an honest horsepower and torque range built from real dyno numbers, not wishful thinking.
Tool one
What does this crank and these pistons actually make?
Pick a stroke and a bore. You get the displacement, the name people call it, and — the part nobody tells you until the case is already apart — what the build actually takes to put together.
69mm is the stock Type 1 crank. Everything above it is a stroker.
85.5mm is the stock 1600 barrel. 90.5 is the biggest that still drops into an untouched case.
The whole chart
Every stroke against every bore. Colour is how much work the combination needs, not how good it is. Click any cell to load it into the calculator above.
| Stroke \ Bore | 83mm | 85.5mm | 87mm | 88mm | 90.5mm | 92mm | 94mm | 96mm |
|---|---|---|---|---|---|---|---|---|
| 69mmstock crank | ||||||||
| 74mmstroker crank | ||||||||
| 76mmstroker crank | ||||||||
| 78mmstroker crank | ||||||||
| 78.4mmstroker crank | ||||||||
| 82mmstroker crank | ||||||||
| 84mmstroker crank | ||||||||
| 86mmstroker crank | ||||||||
| 88mmstroker crank |
Wide table — scroll it sideways on a phone
Tool two
What will it make?
Tell us as much as you know. Every question has an “I'm not sure yet” option — pick it and we'll assume what's most common on a motor that size, say so plainly, and widen the range to match. An honest wide number beats a confident wrong one.
The cam decides where the power lands more than how much of it there is. A big cam in a small motor just moves the whole powerband above where you drive.
Valve sizes are intake x exhaust in mm. This is usually the real ceiling on an air-cooled motor.
Don’t know it? Almost nobody does — it falls out of your heads and your deck height. Work it out on our compression calculator — heads, pistons and deck height in, compression ratio out.
Fill in what you know and press Estimate this build. Anything you're unsure of, leave on “I'm not sure yet” — the estimate will still work, it'll just be a wider range and it'll tell you exactly what it assumed.
This tool is for air-cooled VW Type 1 engines only — the upright case used in the Beetle, Bus, Ghia and Type 3. It does not cover the Type 4 engine from the later Bus and the 914, and it does not cover Porsche 356 or 911 engines. Those are different engines with far less published dyno data behind them, and folding their numbers into a Type 1 model would only make it worse, so we left them out on purpose. Call the shop for those.
Read this before you quote the number at anybody. These are estimates from a model fitted to published dyno results, not a measurement of your engine. Two engines built to identical part numbers routinely land 10–15 hp apart on the same dyno, and the same engine can read differently on two different dynos. Use it to compare combinations against each other and to sanity-check what somebody is claiming. Don't use it to settle a bet.
We’d rather talk you out of the wrong cam than sell you the right one twice.
Washburn’s Metal · Orange, California
Tool three
Work it the other way — tell us the number you want.
Say what you're after and what the car is for, and we'll show you the combinations that get there, what each one costs in parts, and where each one stops being a street motor. Every part listed is something we stock, with a real price. Where a build needs something we don't list, we say so rather than quietly leave it off the total.
Stock 1600, done properly
85.5mm x 69mm · 1585cc · Stock / factory grind cam · Stock single Solex 28 / 30 / 34 PICT · 7.5:1 · 87 octane regular
The factory combination, rebuilt to spec instead of to a price. No more power than VW intended, and none of the headaches either — it runs on 87, it idles, and it will do it for another hundred thousand miles.
Wake up the 1600
85.5mm x 69mm · 1585cc · Mild street cam · Dual Kadron / Solex 40 — 32mm venturi · 8:1 · 91 octane premium
Same 1584cc, same bottom end, roughly half again the power. Dual Kadrons, a mild cam, a header and electronic ignition. This is the cheapest real horsepower on the whole page and it stays civil in traffic.
1776 street
90.5mm x 69mm · 1775cc · Street performance cam · Dual Weber 40 IDF / Dellorto 40 DRLA · 8:1 · 91 octane premium
The classic first big-bore. Stock crank, stock case, 90.5 pistons and a set of 40s. Nothing here needs the case machined, which is why this combination has been the default answer for fifty years.
1835 torque motor
92mm x 69mm · 1835cc · Street performance cam · Dual Weber 40 IDF / Dellorto 40 DRLA · 8.25:1 · 91 octane premium
92mm on the stock stroke. A little more cubic inches than a 1776 for very little more money, and the extra bore all shows up as midrange. Good bus and Ghia motor. The case has to be machined for 92s.
1915 hot street
94mm x 69mm · 1915cc · Hot street cam · Dual Weber 44 IDF / Dellorto 45 DRLA · 8.5:1 · 91 octane premium
94mm on the stock crank — the most displacement you can get without a stroker. With a W-120, 44s and CNC-ported heads this is a genuinely quick street car that still starts on the button.
2110 stroker street
90.5mm x 82mm · 2110cc · Hot street cam · Dual Weber 44 IDF / Dellorto 45 DRLA · 8.8:1 · 91 octane premium
An 82mm crank under 90.5 pistons. Strokers make their power as torque low down, which is what actually moves a heavy car — this is the one to build if you tow, haul, or just hate downshifting.
2276 street / strip
94mm x 82mm · 2276cc · Hot street cam · Dual Weber 48 IDF / Dellorto 48 DRLA · 9.5:1 · 100 octane unleaded
94 bore, 82 stroke, 42/37.5 valves and a set of 48s. This is where an air-cooled Type 1 stops being a fast Beetle and starts being a race engine that happens to have a licence plate. Premium fuel only, and it wants an oil cooler.
Buy it already built — 1776 turn-key
90.5mm x 69mm · 1775cc · Street performance cam · Dual Weber 40 IDF / Dellorto 40 DRLA · 8:1 · 91 octane premium
If you would rather drive it than build it. A complete, dyno-tested, ready-to-drop-in 1776 with heat. One part number, one box, no machine shop.
Buy it already built — 1914 turn-key
94mm x 69mm · 1915cc · Street performance cam · Dual Weber 40 IDF / Dellorto 40 DRLA · 8:1 · 91 octane premium
The big-bore version of the same idea. 1914cc, AS41 magnesium case, dyno-tested, with heat.
Prices are what those parts cost on this site today and will change. Nothing here includes gaskets, bearings, hardware, balancing, machine-shop time or assembly — a realistic all-in figure on a built motor is meaningfully higher than the parts total. The “Add this build to cart” button loads the listed parts into your cart so you can see the real total and edit it; it doesn't order anything.
How this works
Where the numbers come from, and where they don't.
Most horsepower calculators are somebody's opinion with a text box in front of it. This one is fitted to published dyno results, and it will tell you when it's guessing.
Displacement is arithmetic
π/4 × bore² × stroke × 4 cylinders. No opinion in it. We checked every combination in the chart against the displacement the industry actually calls it — 90.5×69 comes out at 1775.4cc and everybody calls it a 1776. The chart rounds; it doesn't fudge.
Power is fitted, not invented
The cam sets how much power per litre is on the table. The carbs and heads decide how much of it you actually get. Compression scales it by the Otto-cycle relationship. Then the carbs, heads and exhaust each impose a hard ceiling — the published flow limits of the real parts. Those coefficients were least-squares fitted against 86 published builds — the 62 with complete, publicly checkable specs are listed below.
The exhaust limits are somebody else's
We didn't invent the exhaust ceilings. CB Performance publishes a horsepower bracket for each primary tube size — 1-1/2″ is 90–140 hp, 1-3/4″ is 175–220. Those are the numbers the model uses. The only one we interpolated is 1-5/8″, because CB doesn't print a bracket for it, and we've said so here rather than hide it.
Flywheel, not wheels
Almost every published air-cooled dyno figure is an engine-dyno number taken at the flywheel, and most sources never say which they mean. This model is calibrated on flywheel numbers and reports flywheel numbers, and shows you the rear-wheel equivalent separately at roughly 15% less. If somebody quotes you a number, ask which one it is.
How accurate it actually is
Against the 62 reference builds, the model lands within 6.6% of the published figure on average and within 5.5% for half of them. The stated range catches the real answer about 78% of the time. That's honest for this kind of estimate — and it's why we show a range instead of one number.
What it can't do
It doesn't model turbos, superchargers or nitrous — forced induction rewrites all of it. It doesn't know your tune, your jetting, your deck height, your altitude, or how good the porting really is. And it assumes the combination is actually matched. It will warn you when it isn't.
A big cam needs compression to work with
This is the one the model used to get wrong. A long cam bleeds cylinder pressure back past the intake valve at low rpm — and if the static compression is low there was never much pressure to give away. A 1996 magazine test that ran one engine through sixteen configurations at 7.0:1 throughout proved how expensive that is: we now take about 16% off per point of compression below what the cam wants, and the tool says so on screen.
Where the data actually comes from
Magazine dyno shootouts, builders' own published sheets, forum threads where somebody posted the graph, and racing classes whose displacement and carburettor size are fixed by a rulebook and checked by scrutineers. That last group is unusually trustworthy — a Formula Vee engine is 1192cc because the rules say so, not because a seller says so.
What we left out on purpose
Porsche 356 and 911 engines and the Type 4 — different engines, and folding them in would make a Type 1 model worse, not better. Forced induction, which rewrites the whole relationship. And pre-1972 American figures quoted as SAE gross, which are measured with no fan, no generator and no exhaust, and run 15–25% above the same engine measured honestly.
Orange, CaliforniaThe receipts
The builds this thing is calibrated against.
86 builds went into the fit; the 62 below are the ones whose full specification is public, so you can check our arithmetic. Every row is a published figure with a live link to where it came from. Where a source gave rear-wheel horsepower we've converted it to the flywheel and said so. Where a number is a manufacturer's rating rather than a measured dyno pull, we've said that too — the difference matters, and it's usually 10 to 20 horsepower.
Wide table — scroll it sideways on a phone.
Questions
The things people ask us.
Does this cover Type 4 or Porsche engines?
No. This tool covers the upright Type 1 case — Beetle, Bus, Ghia and Type 3, the engine family that runs from the 1200 up through the 2332 strokers. The Type 4 engine used in the later Bus and the 914, and Porsche's 356 and 911 engines, are different animals with different data behind them, and there is far less published dyno work on them. Call us for those.
How do I calculate air-cooled VW engine displacement?
Displacement in cc = π/4 × bore² × stroke × 4, with bore and stroke in millimetres, divided by 1000. A stock 1600 is 85.5mm bore by 69mm stroke, which works out to 1584cc — VW rounded up to 1600 and the name stuck. A 90.5mm bore on the same 69mm crank gives 1775.4cc, which everyone calls a 1776. The chart on this page runs the arithmetic for every common crank and piston combination.
What's the biggest engine I can build without machining the case?
1776cc — 90.5mm pistons on the stock 69mm crank. 90.5mm barrels drop straight into untouched case holes. The moment you go to 92mm the case has to be machined, and 94mm needs the case bored to 97.25mm and decked about .060″ a side. On the stroke side, 74mm is the largest you can usually fit with minimal clearancing; past about 80mm the case has to be relieved for the rod bolts, no exceptions.
How much horsepower will my 1776 make?
It depends almost entirely on what you bolt to it. A 1776 on a stock cam, a single carb and stock heat exchangers is a 70-horsepower motor. The same 1776 with a W-110, dual 40s, big-valve heads and a 1-1/2″ merged header is comfortably 100 to 115 at the flywheel. CB Performance rates their 1776 kit at 105 hp with exactly that combination. Use the estimator on this page with your actual parts rather than going off displacement alone — displacement is maybe a third of the answer.
Is that horsepower at the wheels or at the flywheel?
Flywheel. Almost all published air-cooled VW dyno data comes off engine dynos, so that's what the model is calibrated on and that's what it reports. The tool also shows a rear-wheel range rather than a single figure, because the real spread is wide: one builder measured 147 rear-wheel horsepower with the fan belt on and 160 with it off, on the same engine in the same session; one shop’s engine-dyno-to-chassis-dyno comparison lost 31%; another sheet’s own pair implies 11%. Anyone quoting you a flat 15% is quoting a rule of thumb, not a measurement. Whenever somebody gives you a horsepower figure, the first question is which end of the engine it came from.
What compression ratio can I run on pump gas?
On 91 octane, about 9.5:1 is the sensible ceiling for a street air-cooled engine, and that assumes good chamber shape, correct timing and an engine that actually stays cool. Race engines run 10.5 and even 11:1 on 91 — the 2007 Hot VWs Engine Builder Showdown was won at 10.97:1 on pump fuel — but those are built, tuned and monitored in a way a street motor isn't. On 87 octane, keep it under about 7.8:1. Too much compression for the fuel doesn't make less power; it breaks pistons. If you don't know what yours actually is — and most people don't, because it falls out of your heads and your deck height rather than off a box — work it out on our compression ratio and deck height calculator.
Which camshaft should I run?
Match it to displacement and to what else is on the engine, not to how it sounds. Engle's own guidance: a W-100 suits engines up to about 1900cc, a W-110 is the hot-street answer for a 1776, and a W-120 wants 1915cc or more and will barely idle without dual two-barrel carbs. Duration and compression climb together — a W-110 asks for 8.25 to 8.5:1, a W-120 for 8.75 to 9.5:1. Put a big cam on a small motor with stock compression and you lose everything down low and gain nothing up top.
Where does a stock case actually run out?
Cooling is usually the first wall, and it turns up somewhere around 2.0 litres — not as a cliff, but as the point where stock cooling stops being automatic and you start needing a full-flow oil system and an external cooler. Magnesium cases are considered fine right up to 2332cc; experienced builders will tell you to stay with mag up to 84mm stroke by 94mm bore and only move to aluminium past that, mostly because 86mm cranks are a nightmare to clearance in a mag case. Stock rods, rebuilt properly with new bolts, survive higher rpm than folklore suggests.
Why does the estimate say “low confidence”?
Because you left things on “I'm not sure yet”, or because the combination you described sits somewhere the reference data is thin — very large displacement, very high compression, or a mismatch like a race cam behind stock carburetion. The model widens its range rather than pretending to a precision it doesn't have. Fill in more of the boxes and the range tightens. It also tells you exactly which assumptions it made, so you can go and check the ones that matter.
Can I trust the parts list to be complete?
Not on its own, and it says so. The lists cover the parts that determine the power — pistons and cylinders, crank, cam, carbs, heads, exhaust, ignition, case. They don't include gaskets, bearings, hardware, or the machine work, and on the bigger builds there are lines marked “Call” for things we don't currently list, like the right length rods. A real invoice on a built motor is higher than the parts total on this page. Ring us before you buy a whole build and we'll go through it properly.
Talk to a person
A number on a screen never built anything.
When you’re ready to turn a combination into an engine — or you want somebody to talk you out of the wrong cam before you buy it — call the shop. We’d rather spend ten minutes on the phone than process the return.