Engine Boring

[Zander68]

I've heard that boring a stock 1600 case to 1835cc leaves the cylinder walls to(or very) thin is this true?
What is the down side of this? I spend a lot of time on the freeway, and I'm planning to match a new tranny with the bigger motor. (not sure if I'll go five speed, or just change gear ratios)
I'm not looking to win drag races, just want some more power for my bus.
Any thoughts?

[Erik G]

yea, don't put an 1835 in a bus. If you want bigger, use the 90.5's. the 92's are the worst, The 94's are great in a bug, but I don't think I would use them in anything heavy. What kind of budget are you looking at? I would think something like a 1904 or 2007 would be great in a bus, (74x90.5 and 78x90.5) lots of low and midrange torque to push that brick around.

[Zander68]

Erik, sounds like you have a pretty good grasp on the motor situation, however I don't. All I know is, I don't want some race engine I'm always gonna be adjusting. I want power and dependability. You know, oil changes every 3 months and valve adjustments every month, just like my stocker. No dual carbs to synch!!
My budget for motor is around$1200.-$1500. I want to keep my 1600 as a back up.
Ps. what are the numbers (74X90.5) in reference to?

[Tru-Dubs-Bri]

The 74mm is the size of the crank, the 90.5mm is the size of the pistons...

[Erik G]

where do you live? I am sure there is a builder near you that can help you out. If you go with a bigger motor, you are going to nee bigger carbs, syncing isn't that bad, and you don't have to do it all the time. also what year is the bus? 68?

[[email protected]]

There was an article in the Aug. 2001 issue of Hot VW's regarding an engine upgrade for a bus. It was a stroker engine (78 x 8 with 40 Kadrons but of course the case had to be machined. I would say a 76 x 88 would be just as good and its pretty much just a bolt together engine. Anyway if you read the article, I thinks it's exactly what you are looking for in performance for your bus.

[[email protected]]

I've built several bus motors and got the best durability from a 1679cc (88 mm "machine-in" P/C) with Kadrons. also, had good luck with 1776cc previously. Made the mistake of using a 1914cc and got less than 30,000 miles before the cylinders warped out of spec. The above mentioned 78 x 88 sounds good as well!

[VW Jack]

The numbers refer to stroke (crankshaft diamter) versus bore (piston diameter) in millimeters. From those numbers you can calculate the displacement in cubic centimeters (which is the same as milliLiters) which is the 1600 or 1641 or 1835 number that you see all the time. It is equal to the volume of 4 cylinders with the same diameter as the engine bore and the same height as the crankshaft stroke. It's good to know what people are talking about because you can get to almost identical displacements via different methods. (ie a 69 mm crank by 94 mm piston gives almost the same displacement as 90.5 mm pistons via 74 mm crankshaft, but they develop their power differently and argueably take different levels of experience and money to build.) Available Type I cylinders are 85.5, 88, 90.5, 92, and 94 mm. Available Type I crankshafts are 69 (stock), 74, 78, 82, 84, 86, 88, and 90 mm. All the piston/cylinder options are about the same amount of money, but increasing the stroke costs. Hope this helps. Oh, and almost nobody uses the 92 mm pistons/cylinders because the cylinder walls are too thin so they don't last.

[VW Jack]

The numbers refer to stroke (crankshaft diamter) versus bore (piston diameter) in millimeters. From those numbers you can calculate the displacement in cubic centimeters (which is the same as milliLiters) which is the 1600 or 1641 or 1835 number that you see all the time. It is equal to the volume of 4 cylinders with the same diameter as the engine bore and the same height as the crankshaft stroke. It's good to know what people are talking about because you can get to almost identical displacements via different methods. (ie a 69 mm crank by 94 mm piston gives almost the same displacement as 90.5 mm pistons via 74 mm crankshaft, but they develop their power differently and argueably take different levels of experience and money to build.) Available Type I cylinders are 85.5, 88, 90.5, 92, and 94 mm. Available Type I crankshafts are 69 (stock), 74, 78, 82, 84, 86, 88, and 90 mm. All the piston/cylinder options are about the same amount of money, but increasing the stroke costs. Hope this helps. Oh, and almost nobody uses the 92 mm pistons/cylinders because the cylinder walls are too thin so they don't last.

[VW Jack]

testing

[VW Jack]

testing again.

[VW Jack]

testing

[Zander68]

It shows 11 replies, however the last one I see is from myself to Erik.
Wonder why?

[Dave]

Now, one thing to remember, when most of these guys are talking about the 88 mm piston and cylindr size, they are talking about the "machine-in" units, NOT the "slip-in" ones. I know there are some success stories from people who have run the slip-in 88's, and had bad luck with the 94 mm pistons and cylinders, but my experience has been axactly the opposite. The 74 x "slip-in" 88 engine in Skip Coiner's Bus gets run over the Tejon Pass every day on his way to work, and, for SoCal, thats quite a mountain pass, in some sometimes pretty extreme heat. The only thing that has gone wrong with Skip's Bus has been a cracked muffler, and some rubber oil lines leaking. Other than that, it has worked quite well. He has been driving his Jetta to work the last couple of months, though, as the heater in a Bus, as I am sure you know, doesn't work so well, when it's climbing at 4,200 feet on a nice chilly November day (or night)I think another problem you might have is your budget, I assembled a 1914 cc engine for my Single Cab Bus, when I worked at VW Trends, called "Project-Budget beater" - I managed to get a free Gene Berg crank, a good AS-41 case for 25.00, a set of 40 IDF Webers for $100.00, and some "freebies" by rummaging through everyone's stash of unused parts, and I have a lot of friends that live close by that are into VWs, and I still went to, I think it was, $1,200.00 or so for the final engine cost. If you are going to go bigger than a 1776, then I would really suggest the use of dual carbs, as most single carbs will actually get worse mileage than a dual-carb setup, and most of the stock single carbs will choke a 1776 or larger engine of fuel and air, which make for a lean condition, somehting you DO NOT want to have in a Bus
( or any other VW, actually)
Keep listening to everyone, formulate a "plan of attack", and have fun-

Dave

[Zander68]

To Dave,
Thanks for your input, and your last line of advice. It makes the most sense. That's why I'm here at the forums trying to pick other VW owners brains. And I plan on having some "FUN", just as soon as I get over the frustration of figuring out what to do. HA HA.

[Dave]

I just figured out that I printed something that is incorrect- Skip Coiner's bus does *NOT* have "slip-in" 88mm pistons and cylinders, they are the "machine-in" style. Sorry for the mistake and the confusion.