bastard 40 Horse Conversion

[new2bugs]

Ok, I know this sounds crazy but i was wondering what i would have to do, besides the obvious machine work to put 87mm pistons and jugs on a 40 horse with 40 horse heads 40 horse case. Is there a Rod and crank compatiblity problem. Can i use stock 40 horse rods or stok 1600 rods. I want to put this together for my brother and I have the 87's and a 40 horse with worn cylinders, and a new set of 40 horse pistons a barrels may be more expensive than the machine work to make it bigger. I am just trying to figure out what the cheapest route would be. Plus am sure he will enjoy the better pick me up or the bigger displacement. Well I will go out to the Garage and see what is what.

[PEPPE]

i usually do with 85.5. machine the barrels 10mm down, install 22mm bushing in the rods, bore the head hole to the proper sixze and go!
it will work for sure.

[new2bugs]

I am not certain that I understand exactly what you mean. Can anyone help me understand what he means by this. I have no problem getting the heads and windows opened up for this, that much I understand. I am not sure what is meant about the pin sizes . I know the rods are different lengths.

Are the pin sizes different for the 87's and the 77's. I mean In diameter. What length rods would be benificial to use the 40 horse rods or the 1600 rods? Which could I use.

Maybe I'll just put at 1641 single port in there, all I need is a muffler and an Intake and Carb. Well and to rebuild it ofcourse.

I would really rather put together some bastard combination.

[Marc]

Problem #1: 40HP rod big-ends and rod journals are wider than 13/15/1600. The bearing is the same width, but if you use a 1500 rod on a 1200 crank you'll have grossly excessive sideplay.
Problem #2: 1200 wristpins are 20mm in diameter, not 22 like the later rods.
PEPPE's solution, hogging out 1200 rods to accept 22mm wristpins, is the most expedient. It sounds scary as hell (40HP rods are pretty frail compared to 1500s to begin with) but he's been doing it for years and says he hasn't had a failure yet.
There's still problem #3 to deal with, though: with the short 64mm stroke, 13/15/1600 pistons are going to have a ton of deck height and you'll have to cut down the barrels to correct it.

Unless this 40HP case is a 9xxxxxx or "D" block it has no cam bearings and after about 200-250,000 miles it'll always have low oil pressure - especially at hot-idle - and may not even be good enough for a 1200, let alone a 1522. If it's a good case, there's nothing stopping you from slipping in a 69mm stroke crank & late rods to build it as a 1641 (you'll need to install longer head studs and use a 1600 exhaust) except respect for the 40-year-old alloy.
An engine this size would be severely asthmatic with 40HP heads on it, and the intake manifold & overcylinder tin would have to be stretched - much simpler to use 1300 or 15/1600SP heads/manifold/tin.

[new2bugs]

what end of the cylinders would have to be trimmed to fit the head end or the case end?
Are the main journals for the 64mm and the 69mm cranks that same, In diameter. You already said that the 64mm journals are wider. Could I use the 69 mm crank with the short rods from the 40 horse if I thinned them in width and trim down cylinders to maintain the same deck height. kind of like how you would do a stroker. That would make it like a stroker. Longer stroke same deck height. If I reworked the heads and put bigger valves would that get rid of some of the asthmatic problems? THis souds like a a good bit of work, but I am getting excited about it. I could always seek out an old set of Dual 28mm solexes that they used to put on the busses.

Am I explaining this right? Do I just sound like some freak? I would love to have truly unique engine. Something to be proud of and something different

I don't think I said this but, I do have a single port 1600 case and a fairly new set of 87's I also have a 69mm crank. All I have to do is check out that case to see if it needs any machine work. I am missing and intake and Carborator. Well I would rather put a extractor on with at single quite pack. Would a 30 Pict fit on a single port manifold? Or would a 34 Pict be better. This will not be an emissions vehical. Oh and I need to buy bearings and all the fixings. And Pistons rings of course. anyway, thanks for expanding on that for me Marc.

[PEPPE]

it is exactly like marc describes.
i usually trim the base of the barrel but it is doable on both sides. no matter.
to have the best result i have a special fixture for the lathe.
it is possible to use 1600 crank with 1200 rods, BUT on stock pistons it is needed to grind (and rebalance weight) on piston's skirt, because of short rods pistons hits the crank. i have done but i don't like to do again.
best performance is gained with 31 pict 3 carbs or 34 pict with adaptor for small manifold.

[Stroker 40 horse]

For old engines, you need old hot rodding books, like the one with the yellow cover (hint hint). You can use 36 HP rods on a 69MM crank that is offset ground to 74MM or so, use the stock pistons with about 1/4" spacers. No case or head modifications needed, and therefore the integrity of the block is maintained! This creates a 1601 with lots of low end torque, I would assume. I will get my book and give you more info.

[Marc]

Anything's possible, some things are just stupid.
I wouldn't even use 1300 rods on any kind of performance engine, and 40HP are even flimsier. 36HP rods are so weak that the factory repair manuals document using a fixture to check them for straightness when the pistons are off and bending them by hand to correct.

I once built a "1500 the hard way" during the second fuel crisis in the 70s to see what kind of mileage I could get out of a motor with enough balls to push a latemodel Beetle around in traffic safely. Used narrowed 40HP rods on a 1500 crank, 1500 cylinders and 83mm big-bore 40HP Japanese pistons (no skirt clearance problems with them, and the 20mm wristpins could be retained). Used 1965-style ("large-port") 1200 heads with stock valves, a sweet valve job and minor port cleanup. Had to lengthen the intake manifold, and neither a 1200 or 13/15/1600 muffler would fit - was able to heat & tweak a 1600 header into place. Had to lengthen the overcylinder tin, too. In the end it was an interesting conversation piece but it was WAY more trouble than it was worth, considering that you can get nearly as good of mileage and more power from putting 1300 heads on a 1600, and that goes together like a stocker.

[PEPPE]

i have seen that you have a fiat 500. what is the value of it in USA?
i have 2 to sell and i am curious

[new2bugs]

How does it work with offset grinding a 69mm crank to 74mm? Does it have to be standard bearings to do it. Does it mean you have to get different size piston rods or bearings?

If I could offset grind the crank I would just use the 87's and then put it in the 1600 case. I might need to upsize the heads to dual port of something. This case is single relief with cam bearings.

Case Model # is H0457102
Heads model # 311.101.373A Any Idea what the valve size is?

the 69 mm crank doesn't have t he 69 stamped in it. But it is a VW crank. There is the VW logo and a 19 cast into it. It has a Y and 5 stamped into it too

[Marc]

The HO case is from a 1967 1500SP. Not a bad piece when it was new, but who knows after 35 years? I certainly wouldn't use it without having casesavers installed, the overall condition and the amount of other machinework required would determine if it's worth the trouble. You'd still have a small-oil-passage case when you were done - that's all we had to work with until the `70s and plenty of successful engines were made from them, but there's better stuff to choose from these days. I would recommend against using it for a dualport since a DP needs a DP cooling system and the small-passage case isn't compatible with that.
The valves are probably 35.5mm intake, 32mm exhaust.
Offset-grinding the crank is interesting but it isn't cheap, especially to do right. The increased stroke comes from removing more material from one side of each rod journal than the other, so you must use a smaller-diameter rod unless you're going to have the journals built back up with weld - it goes FAR beyond the stock surface-hardening so the journals should be rehardened; the indexing/phasing of the oil supply drillings is thrown off as well so you should grind some reliefs into the journal to shift the oil delivery points back towards the stock location. You're also reducing the "overlap" between the main & crank journals which weakens the crank considerably. You'll need to find rods of the correct journal diameter & length; they'll probably need extensive machinework before they're ready to use (for example, it takes about $150 worth of work to narrow & bush early smallblock Chev rods to work in a VW. Assuming you can find good cores, that'll give you too-long rods that weren't even as strong as a stock VW 1600 rod when they were brand new).
I suggest that you quit trying to find oddball ways to put questionable parts together and spend your time & money on something more conventional - the weird stuff is intriguing and amusing to think about but it's seldom practical, and there isn't much chance you're going to discover something that hasn't already been done, long ago, and since forgotten about because it was such a waste of effort for the results. I'm not saying that there's anything wrong with innovation, but this kind of crap isn't anything new, it's just recycling old bad practices from the days when we didn't have the wonderful selection of off-the-shelf parts to work with that exists today.

[new2bugs]

I guess since this is all pretty new to me and I have only ever rebuilt one engine, and that was the above mention 40 horse, I haven't had a chance to read everybit of VW literature that has ever been written. I am trying desperately to catch up with guys like you though. I am Envious of your knowledge, and Experience.

I just love engines and want to try new things. I had lost my Creativity and am working slowly on trying to regain it. This is the only subject that I have any passion about, even though it is pretty silly to you guys though.

But like I said I will probably just put a 1641 together since I have all the hardware for that. With the exception of and induction and exhaust. This is probably the cheapest route.

To put the 1200 back together all I need is new cylinders. originally I was wanting to see if I could make the 87's work. that way I don't have to worry about New induction and new exhaust. Which now I Know it is possible but that does entail probably as much money in machine work, and grinding as a stroker would, as it would cost for new 77's for the 40 horse. And that would be much easier.

Thanks a million for your answers, advise, and paitience.

[Marc]

You should be able to make a nice little 1641 singleport using the HO case (I wouldn't try for much more out of it). 87s don't take well to overheating, they'll distort and develop blowby more easily than stock-thickness cylinders, but in a lightweight car you should have no problems with them if you keep the compression ratio reasonable and the cooling system functioning well. Don't be a fool and put a racy cam in it, stay stock or close to it (a singleport's strong suit is a nice broad powerband, too much cam will only lose bottom-end with little gain up top).
Keep an eye on eBay, some 1200 pistons/cylinders may show up. I had a bunch of 40HP stuff hoarded which I finally realized I'd never get around to using and either gave it away or sold it cheap to my machinist and to a Formula Vee builder, there's gotta be more folks out there who'll do the same someday.