Strokers

[DurocShark]

Sluggo, you said your engine is an 1800 converted to a 2000? Did you swap cranks too? Reason I ask is, according to http://www.tunacan.net/t4/reference/displace.shtml, putting 94mm P&C on only makes you a bit under 1900. The 2000 has a 71mm stroke, 1700 and 1800 have 66mm strokes.

2 liter crank & rods. 94mm P&C. Definite 71mm stroke.

Let me see if I can get this right.

The stroke of a crank is how far the crank moves the piston within a cylinder. The longer stroke also provides more leverage... The piston is pushing against the crank at a greater distance from its center, taking that leverage and turning it into torque.

"Stroker" engines use a crank with a longer stroke.

You pick up displacement as well as a side effect, but the torque is where the magic is.

If you're using a 2000 crank, you already have a 71mm stroke. Cranks can be bought much larger. Raby sells up to 82mm stroke cranks (!).

I'm considering a 74mm crank for the engine I've got in my garage. $500 and counterweighted. The debate is 94mm cylinders (stock)? Or bore them out to 96mm?

Decisions decisions...

heehee

(I'm going with 96's using the OG cylinders, bored out 2mm.)

[Amskeptic]

The longer stroke also provides more leverage...
I'm considering a 74mm crank for the engine I've got in my garage.

You also change the rod ratio as you increase the stroke. This adds to side loads on the piston in a hurry. Stock 1.7-1.8 rods are at a ratio of 1.92 IIRC, the stroker engines have a 1.67 which is close to the limit.
Colin

[spiffy]

Isn't a true stroker one that keeps the cylinder and piston specs stock...I am thinking of a chevy 388ci stroker.

After all the saying goes...

"You drive torque, but you sell horsepower"

IMHO torque is the carrot we should chase with these engines.

[Amskeptic]

Isn't a true stroker one that keeps the cylinder and piston specs stock...I am thinking of a chevy 388ci stroker.

After all the saying goes...

"You drive torque, but you sell horsepower"

IMHO torque is the carrot we should chase with these engines.

That is true, you have to go chase Chevy rods when you get goofy stroker-mad, or Carillos or billet titanium, and don't forget to bring a wheelbarrow of cash.

You lose the intrinsic design balance of an engine when you change its parameters radically. The European press picked up on the lomp of the 2.0 buses, and that gorgeous BMW 3.0 straight six was nicely ruined when they booted it up to 3.3.

I refuse to get in a hurry. There is nowhere I have to go that requires flogging my poor chariot.
The gearing of the early Type 1 bus with 81 ft/lbs of engine torque has just as much wheel torque as the late bus with 102 ft/lbs of engine torque, it just takes 20% more time to perform the same work.
Colin

[spiffy]

So....stroking a 1700 case is a RELIABLE option?

[Amskeptic]

So....stroking a 1700 case is a RELIABLE option?

There is no stroking a case, nor is there a 1700 case. You may need to clearance a Type 4 case for major stroke, and you may need to grind down the camshaft base circle too, and grind the rods down a bit here and there, but discuss with your performance machinist. . . I ain't answering that one.
Colin

[spiffy]

So....stroking a 1700 case is a RELIABLE option?

There is no stroking a case, nor is there a 1700 case. You may need to clearance a Type 4 case for major stroke, and you may need to grind down the camshaft base circle too, and grind the rods down a bit here and there, but discuss with your performance machinist. . . I ain't answering that one.
Colin

Thanks for slapping me back to reality, what I meant to say is that the 1700 case would be the best option....IF you wanted to go there?

My performance machinist only works with a razor blade



Next topic should be "How to adjust your AFM to account for your newly aquired intercooled turbo"

Okay....bed time for (me) bonzo!

[Amskeptic]

what I meant to say is that the 1700 case would be the best option....IF you wanted to go there?

There is no 1700 case. The cases are interchangeable, spigot sizes are the same for all 1700-1800-2000 engines. The only distinguishing characteristics are bus oil fill hole, carbureted engine fuel pump bosses, and 914/411/2 dipstick, and of course, the later Vanagon cases.
Colin

[DurocShark]

The longer stroke also provides more leverage...
I'm considering a 74mm crank for the engine I've got in my garage.

You also change the rod ratio as you increase the stroke. This adds to side loads on the piston in a hurry. Stock 1.7-1.8 rods are at a ratio of 1.92 IIRC, the stroker engines have a 1.67 which is close to the limit.
Colin

Actually, every recommendation I've read says to stay above a 1.7 ratio.

Stock 1700/1800 has a 1.90 ratio, stock 2.0 has a 1.84. A 74mm stroker crank with stock 2.0 rods would reach a 1.77 ratio.

The higher the ratio, the higher in the RPM band the power peaks.

The nice thing is that the Type 4 cranks can be modified to accept Type 1 rods, so you get a selection of lengths.