Building a Fast and Reliable Engine
By Mark Herbert
I think building a large displacement VW engine has almost become an art form. Bore, stroke, rod length, and compression can all be combined in so
many different ways that once you throw in the human factor you will usually end up with a different and unique motor every time.
I know when I build a new motor that I'm always thinking for a new angle. With so many heads, carburetors, exhaust sizes and cams available you can
choose your "state of tune" or the RPM range that the motor will operate at. Other engine marks don't have this flexibility. Even the famous
smallblock Chevy that also has an entire aftermarket industry behind it falls short of the aircooled VW in parts choice sometimes. So many parts
choices are a great thing but of coarse it can be confusing sometimes.
The best thing I can tell you is look, listen and learn. Sooner or later you will start to figure out who knows what they are talking about and whose
parts work the best. For those of you who don't want to wait that long I will list some proven motor combinations later in this article.
There are basically two kinds of people that want to build a more powerful VW motor. There is the person who wants the fastest thing they can build
and there is the person who wants a reliable everlasting motor. I will try to bring these people a little closer together. First of all the main goal
is more power. So if you're going to build a more powerful motor there's no sense in not going far enough. It costs about the same amount of money
to build an 1800cc stroker motor as a 2275cc stroker motor. And they will both last if they are assembled correctly. With the same carbs, heads and
exhaust they will basically make the same horsepower but the 2275 motor will make it at a lower RPM and be much more fun to drive. Also a motor that
turns 6000 RPM will out last a motor that turns 8000 RPM all the time. So the point is bigger is better when done correctly.
There are some basic levels of performance with a VW engine. Things like heater boxes, boring and stroking determine how much performance you can
obtain at a certain level. The first decision you need to make is do you really need your heater boxes? Are you going to be driving in cold climate
for long periods of time? I did, and it sucked with no heater but at least my car was fast! :-) I eventually built an oil-cooled heater and all was
fine. But don't kid yourself, it took me a long time to build a custom heater and I froze my butt off until then. If you choose to run heater boxes
then I don't recommend stroking your motor or running it at sustained high speeds. The boxes are very restrictive and cause heat to build up in the
heads and will eventually crack them, in some cases severely. Even a stock motor with cleaned up exhaust ports and a competition header instead of
heater boxes will run cooler under extreme conditions.
The next step is boring the case for bigger pistons. If you're going to bore your case for 88s then why not bore it for 94s? It costs the same
amount. Just remember that you must adjust your compression ratio as the motor gets bigger. If you just slap stock heads on a 1900 it will have 9to1
compression and that's too much. I ran a 94x69(1914cc) 7to1 compr. with Kadrons in my bus for years and it was a great motor as well as simple to
build. Whether or not you can go to the larger 94 pistons depends what year case you are using. I don't recommend using 94s with the early 10mm head
stud cases. The later cases as well as all new cases come with 8mm head studs and can be bored for 94s safely. While I'm talking about head studs I
use chromoly 8mm head studs on all my motors. They can easily be torqued to 25lbs or more and do not come loose. The stock 8mm studs can be used but
they will only torque to 18lbs. and if you are buying after market 8mm studs they are usually substandard so just pay a little more and get the
chromoly ones. If your case comes with 10mm studs, the stock ones are fine.
As far as big bore pistons are concerned the only ones that need help are 92s. If you have a 10mm stud case, these are the biggest pistons I would
use. The tops of 92 cylinders are too thin so if you want to use them I would have them sleeved up to 94 bore size. A good VW machine shop will know
how to do this. I will also sleeve 94s up sometimes because it gives a better seating surface in the head. When boring a case for larger cylinders its
best to have it cut for wide base cylinder shims. This also gives a better seating surface. Sleeving the cylinder and using wide base shims keeps the
cylinder from eating into the case or head. I've taken apart daily driver 2332 size motors after years of service and the heads were still torqued to
30 lbs.
Next is stroke. The way I see it if your going to stroke it then STROKE it! Buy at least a 78mm crank and I prefer an 82. An 84 and larger crank
should really have longer rods so Ill get to that in a minute. A 74mm crank is better than a 69mm and if you get one for free I would think about
using it. The thing is if you're buying a crank it only costs a small amount more for an 82. An 82 crank with stock VW rods is an awesome combo! An
82 stroke with any bore and some OK flowing heads will smoke the tires as far as you want! It will also pull a bus and a trailer up any hill. The 82
crank combined with a stock length rod creates a shorter rod ratio than a stock 69 crank with the same rods. This short rod ratio causes the piston to
snap harder at top dead center and in turn makes the heads breath harder. In short what you get is a high torque motor that pulls hard and has
excellent throttle response. This combination coupled with some big pistons and a good set of heads and a medium size cam will make a great street
motor or even an excellent bus motor. If you go with a big cam and heads you will have a real screamer capable of quarter mile passes in the 12s The
key to this whole combination though, is a properly ported set of heads and the short rod ratio.
An 84 stroke could technically be used with stock length cylinders but it is a good idea to go with longer ones with 84, 86, 88, 90 stroke cranks.
Unfortunately the only cylinders that come in longer sizes are 94s so I guess you will just have to be satisfied with huge motors like these:
84x94= 2332cc
86x94= 2387cc
88x94= 2443cc
90x94= 2500cc
I would keep your rod ratio at 1.67 or slightly more for these bigger motors since a shorter rod ratio gives you more torque at a lower RPM and these
motors generally don't need any help in the torque department! Rod ratio is the crank stroke divided into the rod length. Stock VW rod length is
5.39". Porsche length is 5.325" and other popular sizes are 5.5, 5.6, and 5.7. You can order some brand rods in any length. Carillo, Pauter are a
few...
One drawback of a long stroke motor is that after 82 mm they become increasingly wider and you must start to trim the engine tin to get it in the
engine compartment. You can build your motor around this though. A 78 crank with stock rods or an 82 crank with Porsche length rods coupled with any
size stroker piston will fit well into even an early 1200 engine compartment. Or you could just start snipping tin.
Now that I've gone over what it takes to build a larger displacement motor I will get into the "state of tune". Allot of Cal Look VWs these days
are sporting huge motors with giant cams and heads. These engines can put out upwards of 200 HP on 92 octane gas. That's about 1.5 horsepower per
cubic inch. In comparison, a 406 ci V8 would have to put out over 600 HP to make the same HP per cubic inch as these VW motors do. These motors are
impressive to say the least. But they aren't the best choice for a nice driving, fast VW. On the other hand I see people putting together a new motor
with such conservative parts that it seems a waste to me. Ultra low compression ratios, tiny cams and worst of all some advertiser's lame non-ported
out of the box heads! Money spent on head porting is never a waste. Well-ported heads will make any motor run better. Sometimes allot better. I
believe that the best street motor is a big motor with a medium state of tune. An 82 x94 is just about the biggest motor u can assemble with stock
rods. Combined with a set of 40x 37.5 non-welded, fully ported VW heads and a 295dur. x 500 lift cam, a set of 48s (not IDAs) and a 1 5/8s exhaust.
You can have a motor that doesn't cost a fortune to build, will last (as long as you take care of it) and will haul ass! It will also get decent gas
mileage and drive like a dream. This motor will pull at low RPMS as well as high and you won't need to have close ratio gears in your transmission
because it will pull with stock gearing, no problem. In fact, it will run the quarter mile in three gears and you still have 4th gear for the freeway.
You can also use this same motor in a bus but you will have to raise the gear ratios to make it drivable - unless you want your bus to run 14s in the
quarter! I suggest a late model 4.86 or 4.57 R&P along with some larger diameter rear tires for bus applications.
A motor like this will pull from 3500 to 7000 with the right heads. The same motor size but with aftermarket or welded VW heads and a 320 duration cam
will usually only pull from 5500 to7500. A much smaller RPM range. That's why they need closer ratio gearing and a 5 speed to drive on the freeway.
Of course they are frightfully fast too! Huge motors with huge cams can be driven around with no real problems although they will need valve jobs more
often. It's just that you have to be in the right gear to make it go and it will not get very good gas mileage. You have to ask yourself do I want to
sacrifice so much for a 12 in the quarter instead of a 13? Just look in the magazines under new car specs. and see how many cars run 13s in the
quarter. Not many and you usually won't see one driving around anyhow. But to each his own.
I will take a motor with a middle state of tune every time but some of my friends just want the most power no matter what the cost and they like high
state of tune motors. The thing is if I'm next to them and they're not at 5500 RPM when we jump on it, I will leave them in the dust!
Here are some of my own motor combinations that have worked well for me. All cams listed are Engle brand. 1914cc, 94x69
This motor can be built with smaller cylinders but the low RPM torque will suffer slightly. 94 Cima pistons, 69 counterweighted crank, stock weight
flywheel, stock rods. All balanced. 110 cam (285dur x .430lift) You can use 1.25 rockers if you want or a VZ25 cam with stock rockers. Solid shaft kit
for rockers, thin-wall chromoly pushrods. 040 stock VW heads fully ported with reshaped and hemicut chambers, a competition valve job with dual
springs. Compression ratio for bus, 7 to1 for bug 7.5 to 1. 1 1/2 " header with 2" turbo muffler. Dual Kadrons or 42 Webers or 36/40 Dellortos. 40
Webers can work but they need bigger 32to34 mm venturies. Also a single 36 Dellorto or a 40 Weber can work with an isolated runner manifold but they
get bad mileage and they make your motor slower. 009 distributor and Bosch blue coil. This motor can be used with heater boxes if it is used mostly
for around town driving. If you drive at sustained freeway speeds the heads will be cracked in no time. I really think heater boxes should only be
used on an almost stock motor. This motor will make any VW a really fun car to drive. You will go from having a stock anemic slug to a car that has
effortless power. This motor can also be revved fairly high and will make power well into the RPM range.
Stroking the motor
The next step as far as I'm concerned is a crank. Sure you can spend money on bigger heads and put more cam and carbs on a stock stroke motor but
then you have a motor that is faster only in the high RPM range. For my money, I would build the same motor as above with a 78 or 82 crank. 600 U.S.
dollars will buy you a welded stroker, the machine work you need and a set of stroke relieved stock rods. It's more complicated to put together but
well worth it. It's a good idea to go with larger carbs and exhaust at this time because you will need their better breathing ability. Your new motor
can be a 2006cc to a 2276cc and it will pull like a stock stroke motor never could. The RPM range will be much lower so it will start pulling sooner
too.
2276, 94x82
OK, now for my favorite motor. a 94x82 (2276cc), medium state of tune. 94mm Cima pistons, 82mm welded stroker, stock relieved VW rods, 14+lb flywheel,
120 cam (295dur x .495lift w/ 1.25 rockers). Solid shaft rocker kit, 3/8 thin-wall chromoly pushrods. 8 mm chromoly headstuds. 040 stock VW head
castings w/ 40x37.5 valves, fully ported (as big as you can go without welding), unshrouded chambers w/ hemicut, 8 to 1 compression, competition valve
job, stainless steel valves, dual springs, titanium retainers, tapered intake guides, intake guide bosses NOT removed, intake manifolds match-ported
all the way up.
48 Dellortos on IDF manifolds are my 1st choice but 48 IDFs will work fine too. IDF manifolds are a tricky thing because there are so many different
types. The ones that work the best on this motor are Gene Berg, but they are a pain to install because they are shorter. I've heard CB performance
makes some decent manifolds but they may be too tall. Other manufactures make manifolds that are slightly taller than the Bergs and are easier to
install, but they have a tendency to break at the flanges. I use 11mm nuts with thick washers to make installation easier.
I also grind down a 1/4" drive socket and the manifold sometimes to make sure everything is clearanced before I put the manifolds on. A little bit of
grease on the gaskets helps them seal and the gaskets will come off in one piece later when you remove them. I use a 1 5/8" header on this motor with
a 2 1/2" turbo muffler. If you can find metal exhaust gaskets you are better off. I use a small amount of hi temp silicone on them and I use Porsche
style 12mm copper locknuts to install the header and muffler and I use washers on all.
Well there you have it. This motor will never disappoint, and it will last a long time too. I still have my first motor of this type and it has been
in several cars including my bus. If any of you have seen the QUAIFE test video with some moron doing donuts in a black 61 bug for 5 minutes straight,
that's me (Editor's note: this video can be seen in the Audio/Video section). That's about the 3rd car that that engine went in. I overheard people
talking after they saw the video "that's the end of that motor". Well it went into my bus after that and got driven 140 miles round trip from my
shop to my house. I will never get rid of that motor, its way too much fun!
Here are a few things that apply to any HIPO VW motor:
36hp aftermarket fan shrouds: These shrouds do not have all the spotwelds that a stock shroud does. They have no welds on the front side to hold in
the internal fins. If you put allot of miles on your motor the fins will break off and over heat one side of the motor. To fix this I squeeze silicone
glue in the seams between the shroud face and the fins. You can't reach all of them but get as many as you can. This will keep the fins from
vibrating and falling off.
Welded and balanced fans: Get one. Further, if you build a motor that is revving 7000 or more I use power pulleys so it doesn't throw the belt every
time you rev the motor. Most high HP big cam motors will not over heat with this pulley.
Piston Rings: I replace the top chrome ring on a Cima piston with another cast iron one. They seem to seal better.
Ported heads: First of all make sure when you order your heads that they DON`T cut out the intake valve guide bosses. True head porting talent is hard
to come by. You should talk to a head porter about your heads, not your VW parts supplier. I will try and get some numbers of good head porters listed
in the future.
Welded strokers: Welded cranks can take a lot of HP, but there are limits. Using a smaller Porsche or Chevy rod journal, long stroke cranks with allot
of compression is a bad idea. An 82mm VW journal is as far as I would go and these cranks have been used for decades with no problems. You must check
all welded cranks for straightness and journal trueness.
Cases: Your are much better off getting a new case. If you can find a low-mileage, used case and you know how to check for cracks and warpage then it
might be OK. But it's still a gamble.
Lubrication and Cooling: An additional oil cooler/fan/thermostat mounted under the rear luggage compartment next to the trans on the left side is a
good idea for warmer climates. I use cast iron full flow covers for the oil pump.
Mufflers: In a recent dyno comparison between Flowmasters, Boorlas and other top brand mufflers, Walker Dynomax super turbo mufflers made the most
power. The best part is they don't make your car sound like a dune buggy.
