Engine Boring question?

[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?

[69 in St.Louis]

I've rebuilt a few stock and mild engines but never a 1835, but I believe 1776 is the largest piston you can put in a stock case before you bore the case for larger cylinders. I think 1776 cylinders are bored out 1600 and that is why the cylinders are thinner. To make a 1835 you need to start with a set of cylinders which have a larger outside diameter. As far as five speed goes I've read that adding a fith gear slows the engine too much and overheats your engine. Check out what Gene Berg says on the subject. Good luck, I would'nt mind making my '69 a highway machine as well.

[[email protected]]

Re: crankcase...the 83, 85.5, 87 and 88 mm P/C all fit in the stock case bores...ie. the 85.5 is simply a "slip-in" that the factory used to increase the 1500 cc to a 1600 cc. The 87 and 88 slip-ins are generally not recommended and were never used by the factory.

Now, once you start to bore the crankcase, you can go with thicker 88 mm P/C, 90.5, 92 or 94...all of these require the case and heads to be bored. The thickwalled 88 mm are extremely durable (similar to the 83 mm), while the 90.5 is also very durable (often said to be just as good as the 85.5). The 92 mm is just a slip-in that fits the 90.5 mm bore, so it is not as durable (it is too thin to resist warping in the long run), but many people still use them. The 94 is more durable than the 92, but not as good as the 90.5 (94 mm is used in a lot of fast street and strip Beetles, but I wouldn't recommend for a bus).

In summary, 83 mm = ~1500 cc, 85.5 mm = ~1600 cc, 88 mm = 1679 cc, 90.5 mm = 1776 cc, 92 mm = 1835 cc and 94 mm = 1914 cc. I have built numerous 1776 cc, 1679 cc and 1914 cc engines. I would strongly recommend that you go with either the 88 mm (big bore kit only, not the slip-in version)/1679 cc OR the 90.5 mm/1776 cc, especially on a bus. My previous '69 Westy ran especially great with a 1680 cc, Kadrons, header, 009, mild cam. Perhaps check out type2.com for bus-specific info. Good luck!

[Zander68]

Forgive my ignorance, but I guess this is how we learn.
See if I have this right, Bigger pistons= more power...................Correct?
But you've added header,mild cam,dual carbs.
My intent is to pick up some speed on the freeway. (cruise around 70-75)but I don't want dual carbs, as I hear they are a bitch to synchronize. I plan on changing tranny with motor.
I would prefer to remove my stock 1600 and start new. Is this practical?

[[email protected]]

Actually, Kadrons (EMPI) are very easy to adjust...in fact, I have never adjusted any of the five or six sets I've owned over the years, except for the set screws that connect the linkage to the carbs. However, the Weber and Dell'Orto dual carbs have four barrels instead of two, so they may need more tuning.

Now, regarding cruising 70-75 mph, my '69 Westy ran great with the stock single carb 34 PICT, but I switched to Kadrons in order to get more air & fuel for climbing mountain roads. There is a big jump from third gear to the overdrive fourth in a bus, so twin carbs really help.

[vwsrus]

One thing to remeber is that it's a bus. I've a 71 westy and thought the same. I put an 1835 in it with a progressive carb. It ran like a champ. I only got about 16 mpg though. But I could do 90 mph! That's freaky in a bus. I ended up trashing the valve train due to over revving it in first gear. Also remember that the engine has to work harder to push such a great mass. Dual carbs are wonderful. Even the progressive was great. IT's all about more gas and air in the combustion chamber to make it fire better. But the more fire, you need more cool otherwise no ride and a waste of money. I'd be hesitant to just jump to larger cylinders. Try upgrading small things first. Go with port & polished heads. No one can go wrong there. Try a electronic ignition system. Your goal is not only more horse power but retaining the tourqe.

Hot Vw's or VW Trends just did a few articles about a freeway flyer trans in a bus. they also did a stroker engine in it too. the guy was traveling 60 miles to work in it and reported that it was getting 20 plus miles per gallon and had a lot of power.

Feel free to give me a shout.

[static]

vwsrus is correct. It's a bus, not an Acura.

With a few exceptions, my advice is to stay stock, roll a fat one, light it up, get into the right lane and drive 62 mph.

Big bore kits, dual carbs, stroker kits, etc are just more trouble than they are worth and will only get you to meet more tow truck drivers.

[Zander68]

I don't mind the right lane, hell I don't mind 62mph. I just don't want my bus to sound like it's going to fly to bits on the freeway.
Maybe motors not the problem. What about the trans? Any upgrades out there to bring the rpm's down in 4th gear?

[stripedzebras2]

I put an 1835 in my 71 bus. I really didn't have any complaints about it. It would do 85 on the freeway. Probably about 70 or so fully loaded for camping. But of course that wasn't uphill!! The only problem I had with it was a collapsed valve, but I had that warrantied. But I am also looking to upgrade it now, I want to go uphill faster.

[chabanais]

1776cc, as I understand it, is the largest you can go without having to enlarge the case or having to add extra cooling. I have had a 1776 engine in my '71 Bus for about 5 years. Everything else is stock. It runs fine, I can go 65-70 on the highway no problems, faster if I need to, and my compression is still as high as it was when I had it put in. I use synthetic oil and that's about it aside from regular tuning, etc.

[Amskeptic]

Your stock transmission rear axle ratio in the '68-73 buses was 5.37:1 which gives you about 4,200rpm at 60 mph. That happens to be right near the horsepower peak for a stock Bus. As VW intended, I might add. If you want reliable high speed driving, you need to pick your favorite cruising speed, and see about getting a gear ratio that allows you to have the engine near the horsepower peak.
I read above quote about 90 mph, that is 6,000 rpm with stock gearing. Not good for a Bus. If you decide to up your horsepower and torque, you will want to change your gearing for the best balance of highway driving.
Most VW Bus Engineering Geeks try for a horsepower to torque split between third and fourth, so that your hill climb will slow the Bus down to the torque peak in fourth-shift-to-third, now you are in the horsepower peak for third. The stock Bus already does this nicely. Use the 1976 2- liter Bus as your guide if your new engine has gained 10-20 horsepower over stock, and if it has gained enough torque to hit 100 ft/lbs or so. If you put in a 4.57:1 rear axle and a .88 4th gear here is what your new freeway flyer Bus would do.
77 mph @ 4,200 rpm.(consider that your top reliable cruising speed in cool temps)
70 mph @ 3,800 rpm (all day if you want)
Shift from 4th to 3rd @ 55 mph will exchange your torque for horsepower, can't beat that.
Colin