1043cc engine kits 97mm

[bernardofeio]

hello

any comments and technical details on the several 1043cc engine kits? lets try to summarize these 97mm versions


to my knowledge there are 4 (maybe more)
　
-Mahle sport kit standard
Compression: 9,5:1
Barrel length: std
Piston + rings weight :604g
Caracteristics: nikasil barrels and casted pistons
Pros and contras: "bolt on"

-Mahle hight compression ratio.
Compression: 10,5:1
Barrel length: ?(short cylinders)
Piston + rings weight:?
Pros and contras: not "bolt on"?
Caracteristics: nikasil barrels and casted pistons
Power/torque:

-HPN engine kit
Compression:
Barrel length
Piston + rings weight
Pros and contras:´
Caracteristics: nikasil barrels and casted pistons
Power/torque:
　
-"Venolia" engine kit
Compression:
Barrel length:
Piston + rings weight
Pros and contras: pistons prone to cracking
Caracteristics: steel lines and and casted pistons
Power/torque:




bernardo feio

[bmweuro]

This would be the most reliable and street-able kit out of the 4.

-Mahle sport kit standard
Compression: 9,5:1
Barrel length: std
Piston + rings weight :604g
Caracteristics: nikasil barrels and casted pistons
Pros and contras: "bolt on"

[supershaft]

I think BMW had a lot of good reasons for stopping at 94mm. Namely cylinder wall stability and gasket seal.

[moorespeed]

There is not a problem with 97 mm pistons in nicasil cylinders, I have been racing with them for well over a year with no problems, my pistons are 415g . 12.5 -1

[bmweuro]

Originally Posted by moorespeed

There is not a problem with 97 mm pistons in nicasil cylinders, I have been racing with them for well over a year with no problems, my pistons are 415g . 12.5 -1

You are my hero That has to be some serious HP!!!

[Airhead Wrangler]

How 'bout the 1070 kit? Where does it fall in here. I don't understand how the thickness between bore and stud bores isn't impossibly thin. I see that the cylinders don't extend beyond the base joint as BMW cylinders and 1043 cylinders do.

[supershaft]

As thin as the cylinder walls are long the stud bores, the issue that I have seen numerous times with the lined big bore kits is that the cylinder gets like a corrugated pipe right in sync with the cylinder's fins. I would think that issue would be worse with plated aluminum but I don't know from first hand experience. In my experience, it takes about a race season for the corrugated cylinder walls to show up. That's fine for racing but . . . . I hope the plated bores are better about that but I would think they would be worse?

[Airhead Wrangler]

Since they make their own casting for the cylinders they can make the walls as thick as they want, but the one thing they're stuck with is the locations of the cylinder studs.

[supershaft]

Originally Posted by Airhead Wrangler

Since they make their own casting for the cylinders they can make the walls as thick as they want, but the one thing they're stuck with is the locations of the cylinder studs.

Thicker walls? That would take an entirely new casting for a really small economy of scale. I don't see it with my own eyes either. Measuring the outside of the cylinders between the fins would answer if they did that. I hope so but I have my doubts. The studs AND pushrod tubes not moving is the source of some sealing issues that's for sure. The super thin cylinder wall along the stud bores can't be good? Oh well, we aren't the first to push cylinder wall thickness to the point of troubles. Most all engines suffer that fate to some degree. BMW has said in so many words that they think they had got there with a 94mm bore.

[Rob Farmer]

Originally Posted by bmweuro

You are my hero That has to be some serious HP!!!

Richie's too modest to blow his own trumpet so I'll do it for him.

Richie did some head work for one of my bikes a few months ago. The quality of his work and parts is second to none. to say I'm pleased would be an understatement. he's also racking up an impressive list of winners in Classic racing http://www.moorespeed.co.uk/classic-racing

[RGregor]

Originally Posted by supershaft

Thicker walls? That would take an entirely new casting for a really small economy of scale. I don't see it with my own eyes either.

Have you ever seen one of the kits mentioned here?
Supplier for the Siebenrock kit is Mahle.
Being not the OEM supplier they probably had to make a new casting.

[chasbmw]

I have a Seibenrock 1070 kit on my bike.

It has done something in the region of 10k miles, it has not suffered any of the theoretical weaknesses that SS talks of, the cylinders are nikilsil and are I would assume are new castings to fit the kit, certainly the cost of the kit would make this economic even at very low production numbers.

The kit includes cylinders, pistons, con rods and the assymetrical cam from Seibenrock. The kit works together with the other mods on my bike, dells ported heads twin plugs, 40mm exhaust, Jim Cray silencers, lots of torque, plenty of BHP and if you wish 50mpg at bimbling speeds. The engine was put together by Jim Cray, who balanced it as well. I used the HPN clutch friction disc as had problems with clutch slipping.

Charles. Speaking from experience.

[supershaft]

Chase, do you have an accurate way of measuring the cylinders between the fins in order to see if they are bigger castings on the outside?

For street bikes the troubles I have seen for lined big bore kits takes that many miles or longer to show up. If it's not smoking, using oil, and leaking oil in another 10 or 20K miles it is doing great. My trouble is that I expect it to be doing great in another 70k miles. I wish nothing but good luck!

[RGregor]

Originally Posted by supershaft

If it's not smoking, using oil, and leaking oil in another 10 or 20K miles it is doing great. My trouble is that I expect it to be doing great in another 70k miles. I wish nothing but good luck!

The 97mm HPN kit has been used here now for over two decades.
The 98mm Siebenrock kit for over 5 years.
I personally know several riders with these (97mm and 98mm) kits installed running them for years and many many kilometers.
None of the problems you describe have been experienced or ever been reported in the beemer-related forums.

Perhaps the sets you saw were just a pile of crap?

[chasbmw]

Back in the old days if you wanted a larger than stock engine, you had to take a BMW steel lined cylinder and bore it out, im not sure if special liners were fitted, but in any event the liner would be thinner than standard as the operation was constrianed by the size of the existing BMW cylinders, these were often fitted with venolia pistons. These are the setups that according to SS have developed corrugation.
Nowadays we have the luxury of the kits coming out of Germany mainly sold under the brand name Seibenrock which feature new aluminum cylinders faced with nikilsil and no steel liners. The dimensions of these cylinders is still constrained by the location of the pushrod tubes and the cylinder bolts, but I would suppose that an aluminum casting faced with nikilsil with be much more stable than a casting fitted with a liner. The only proper way to measure the thickness of the casting would be to do it with the cylinders off the bike, I'm not that willing to do this because one of the downsides of the Seibenrock 1070 kit is the cost of replacement cylinder head gaskets!


I was wrong about the Swiss cam, that one is a 320 degree cam. On the HPN site they are at pains to tell everyone that the 320 cam they use in their bikes is different from the 320 'Swiss cam'