:eek1 ooohh... this could get interesting... this isn't Pandora's Box, this is Pandora's BOX... To start with, there was a recent, long, extended, well-debated thread on dual-plugging, which included reference to at least several other threads on the subject... You can start with that. And this one, a classic article. ... and then there's the cam question.... ... and the moorespeed-Siebenrock.... You WILL get responses!!
How many miles on the engine? How much money do you want to spend? How long do you want it to last? These three questions should answer your question as to what to do. A forth question could be, What performance do you expect? Why I say that could be a forth question is because how you run in the engine and how you ride it every day will determine that. If the engine has less than 100k miles on it, I'm a believer of making them last as long as possible. If you want the biggest bang for your buck, rebuild the heads, put in a new cam chain and sprockets and ride on. If the pistons and cylinders are close to spec. put them back in. As for performance enhancements, the sky's the limit. Some you'll notice, most you won't.
There is a very long and sometime acrimonious thread on cams here, just use the search function. It comes down to 2 camps, those who think that the BMW 336 cam is the best there is (as long as you don't get a faulty one) or others who think that the wider variety of cams now available might give you a better choice for your particular engine. Nobody seems to be able to demonstrate how cam choice can change engine characteristics, ie same engine spec, different cams blah blah. I have a seibenrock 1070 bike, with dells, the seibenrock as symmetrical cam, ported etc etc, put together by someone who knows what they are doing, it's very quick, but I seem to prefer my slightly less modified 90/6, with high comp Wossner pistons and a 320 degree cam from Motoren Israel. It suprised my KTM riding buddy the other weekend when I opened it up..... Take a look at the Motoren Israel website for a wide range of cam shafts. Both my bikes are dual plugged, seibenrock recommend it for their 1070 kits, and a I think that it's a good idea for any airhead with 9.5 CR or over, especially if you are like me and use your bike to travel to places where fuel quality might be a bit suspect. I have a dyno test booked in 3 weeks time to check the R90, I did a baseline check before I fitted the 320 cam, so should be interested to see what that cam does in that motor. There are various dynocharts on my photobucket website, same user name as here.
The only comment that I would make is that I think a carb upgrade would complement the engine upgrades. I doubt if the current 32mm Bings would keep up with the motor. They would effectively strangle it.
My 1070 bike uses dells....and a full 40mm exhaust. On the cam choice issue, my bikes spend quite a lot of time riding unknown to me narrow twisty roads and speeds that might reflect my ignorance of that countries legal and medical systems. So I like cams that retain low rev performance from 2k to 3k and give me a nice kick from around 4k. Avoiding radical levels of lift is likely to help long term reliability.
Acrimonious? I remember Moorespeed saying that he wouldn't use a BMW 336 as a 'paper weight'. Then someone else pointed out Moorespeed praising the BMW 336 for the great cam that it is in some article written up a few years back. I guess before he invested in his own cam to sell? I do not remember anyone saying that the BMW 336 was the best cam there is. Could anyone quote that? I do remember people that use and like the BMW 336 cam defending it against the usual decades long anti-336 BS. It goes way back. Probably back to when Luftmeister started selling an alternative even though it was mostly owned as I understand it by BMW's importer at the time? I believe it was Moorespeed that said the typical 336 bashing line that the 336 made less power than a 308 below 6000rpm? I am glad we have FINALLY got to the point that that nonsense isn't even brought to the table anymore. It took a LOT of typing over the years! That and a lot of other people chiming in with their ACTUAL experience describing the 336 for what it actually is: a moderately ground all around great midrange performance cam. Below 3000 rpm? With 8.5:1 compression? Yes, in my experience the 336 does make less power than a 308 below around 2800rpm. But now my bike is dual plugged with 10.0:1 CR and a major port job along with its 336. Now it makes more power than a stock bike with a 308 from idle on up. A LOT more power. BMW's 308 and 336 are the only two cams I have run. I have nothing but good things to say about the 336. GREAT all around performance cam that is easy on our mile long valve train. I just had my engine apart with 71,000 miles on my 336 for toasted exhaust guides at 101,000 total miles. My cam and all four lifters looked perfect. I put all that right back in! I replaced the timing chain and crank sprocket and I put new cylinders and pistons in too. One of my compression ring grooves had worn like they often do and almost all of the crosshatch was gone from the top half of my cylinders so . . . . I don't have any experience with moorepeed pistons. I do have experience with custom machined squish band pistons. Matching the pistons squish band to the heads squish band is far from anything new. I would dual plug if raising compression is in your plans. Most everyone that is winning is excepting Moorepeed. From every main event qualifying Harley Davidson XR 750 on the track to every top fuel funny car and rail dragster on the strip that makes it to the NHRA finals. There is nothing vintage and/or old man about all those classes!!!
Both those articles were written prior to a wider range of camshafts, becoming available......and owners own reviews of their own work is subject to a great degree of confirmation bias, unless the owner has the balls to subject his wrk to some objective testing. Obviously this is also true of commercial bias from those who sell the stuff... I like dealing with someone who can demonstrate the success of their modifications, either on the racetrack or on the dyno. And remember that if you sell a modified bike on the basis that it has X performance but the proud owner only gets Y, you are not going to stay in business very long. So Jim Cray continues to get my vote as he does use a dyno to check his work.
Steeper ramped cams? Most all performance cams have steeper ramps than the 336. That's what I like about 336's for street bikes. Very little extra lift with even longer ramps to baby our mile long pushrods. They flex enough as it is with 308's. From what I can tell from looking at my pushrods after 70,000 miles of shifting at 8000 rpm all the time, they don't flex any more for the 336's extra lift over a 308's. I was running stock spring pressure with titanium valve spring retainers. I did replace my titanium retainers. They were well hammered. Nevertheless, I decided to go to custom made aftermarket 4130 pushrods. I suspect they are an important part of my overall performance gains this last go through. The big time pushrod guys (NASCAR and NHRA) have had a revolution in pushrod tech in the last decade or so. Everyone is now running pushrods two or three times heavier than before for less flex and more power with very little penalty in lower valve float rpm's.
That is quite counter-intuitive to me.... the theory of reciprocating mass and all that. Interesting, I am all ears!
Exactly. It was counter intuitive to everyone. Some guy figured out how to film them in action a little over ten years ago and was amazed at the amount of flex. Cam timing at the valve was WAY off what everyone thought was going on. Mind you, these car guys are running WAY more lift AND spring pressure but still . . . . The fact that our pushrods flex a lot with 308's is undeniable. Look at them and figure what they are rubbing against to wear like that. Even BMW's steel pushrods flex like that to a lesser degree. People in the know have known that weight on the pushrod side of the rockerarm somehow makes very little difference in valve float rpm over weight on the valve side of the rockerarm for half a century and longer now. But still people were running as light as they could on the cam side of the arms too. All that has recently changed and is an important part of higher power outputs. 4130 is a lot stronger in compression than 1018 ('regular' cold rolled steel) so that is what most people are using. Some are using 4140 but most seem to think 4130 does the job. That is NASCAR and NHRA guys. Very moderately stiffer valve springs can compensate for pushrods three times as heavy as what was being run. Valve spring harmonics are also being controlled by weight distribution as well. My setup is still experimental with only 5k miles. I am running stock spring pressure with 4130 pushrods that weigh almost three times BMW's aluminum rods and twice as much as their steel rods. AND 2mm bigger and heavier intake valves than before. From what I can tell so far, I think my valve float rpm went down around 300rpm. That is really no big deal since my bike is now making much more power at lower rpms so I am not revving it nearly as high as I use to. I thought I had better point out that I have been and I am still am running titanium valve spring retainers. Just a few grams on that side of the rockerarm makes a Big Diff. I agree with most that they lowered my valve float rpm almost 500rpm. But still, I think I am going to preload my springs a bit if I ever have my heads off mostly for that missed gear and whatnot. For instance, I was gently rolling into my throttle down hill and in second gear at very low rpm. Mind you, with my close ratio RS gear set my second gear is almost like your third gear. In a nano second my bike was sideways and my tack pegged off the chart for spinning up the rear wheel. The road was slightly damp! I was worried to death I bent a valve. Luck was with me THAT time! There are all sorts of custom pushrod places and the prices are very affordable. Most of them do not have metric ball ends. There is an American sized ball end that is very nearly the same. I have seen serious troubles with ball ends in our engines so I didn't take any chances and got metric ball ends. Google around. PM me if you are interested in what I am running. I have just about got my shop setup again!
The advice that I've always received is that bottom ends can go to 200k or more. Probably worth it to check pil pump whilst you are playing with cams. To make the best of your cam then think about CR and dual plugs. You can retain stock low compression pistons and increase CR by milling head/cylinder. This has other advantages see thread here on Squish.
That 336 cam conversion article? I can't believe people are still bringing it up. It's a huge source of misinfo. I think that article is why so many people thing that 336's have no more lift than a 308 and gets all it's differences over a 308 from overlap alone. Wrong! The article starts off with a major error in its first paragraph and goes down hill from there. Economics? I suspect Jim Cray is the real deal. Nevertheless, I have seen all sorts of businesses be in business for decades and decades not delivering what they promise. If only 'economics' were as perfect as many seem to go on like it is. BS! Lot's of bad businesses stay in business. The 'free market' revolves around nothing but human psychology. It has nothing to do with any Law of Nature or any other law. Perhaps other than we humans can be as stupid as we are smart and I would say the odds of that are worse than 50/50. Squish band? I still do not see the advantage of running a low compression piston and taking .050" off the heads or cylinders to get the exact same compression the stock 9.5:1 pistons will get you? The squish band? Instead of taking .050" from there why not take zero to up to around .010 or .015 off a very narrow portion of the heads combustion chamber? I try to save what I have got AMAP. Valve train geometry and thermodynamics will thank you for it. I just hot rodded my engine some more with 101,000 total miles after putting a 336 in it 70,000 miles earlier. My rod big end bearings were nearly perfect but I prime my pump every oil change and use BMW oil. I have looked at enough mains to think that my mains needed no attention. Same with my oil pump. I looked at it 70,000 hard revved way over redline miles ago and it was perfect. I have looked at enough oil pumps to believe that pretty much nothing wears them but cylinder stud repair metal shavings or glass beads run through the engine for not cleaning the parts properly after bead blasting them. That is nothing within reason considering a properly cared for airhead. I didn't look at my oil pump either. It was still sealed perfectly and as dry as toast around the cover. My RMS was leaking just a tad so I replaced that. I am not super wealthy either. I would save my money on the ignition. The stock ignition works fine dual plugged. Remapping the ignition curve is not hard for the most part. Dyna just came out with their lower primary resistance blue coils. /2 BMW bulk ignition wire is cheap and so is NGK caps. A lot of electronic adjustable ignition curves have every option known to man but what I have seen work on dynos time and time again with different bikes. The curves are very often not adjustable regarding the curve's rpm range. That I don't understand? Good luck!
Today I've been out on a couple of my airheads, both 93 gs bikes. One of them has a 336, 9.5:1 pistons, moorespeed one piece valves (44 inlet, 38 exhaust) 40mm bings. Goes really well and pulls like a train. The other ones fitted with a moorespeed engine. Lightened and balanced crank. Moorespeed long skirt pistons, r80 small port heads machined to fit 1000cc barrels, ported and flowed. Moorespeed one piece valves (46mm inlet, 38mm exhaust), 324 cam and 38mm dellortos. I haven't had the time to get the jetting perfect but there's no comparison in performance to the other bike. This one feels like an 1100 oil head. It pulls harder all the way through and really takes off when it hits 5k. Long term this engines not staying in the gs and will be fitted into a road bike chassis. It's too quick for the gs chassis. If you go for the moorespeed pistons you don't need to twin plug.
