[brian98]

I thought I've heard others have done this, but couldnt find it in a forum search. I want to put the 748r OF cams in the 996. Lobes dont line up on rockers exactly the same, but it looks close enough? 996 has stock 36/30 valves. Someone already replaced the rockers with new hard facing, so I've got that going for me too.

yes, I know I'm going to have to cut bigger piston pockets to keep squish down and not hit P to V. My concern/question is if the change in cam to rocker alignment is an issue.

TIA

Brian

 

[CinKo]

I thought I've heard others have done this, but couldnt find it in a forum search. I want to put the 748r OF cams in the 996. Lobes dont line up on rockers exactly the same, but it looks close enough? 996 has stock 36/30 valves. Someone already replaced the rockers with new hard facing, so I've got that going for me too.

yes, I know I'm going to have to cut bigger piston pockets to keep squish down and not hit P to V. My concern/question is if the change in cam to rocker alignment is an issue.

TIA

Brian

Brian, first let me be clear, I have not done this on a ducati, I would not have chimed in at first but since you got no responses I wanted say what I know and at least move this back up to the top for you.

I have swapped cams before from similar bikes, specifically and most recently from a ZX-11 to ZRX1100, From my personal understanding as well as my take from what others have told me is that If those lobes don't line up perfectly you will end up getting pitting under use. I would definitely confirm with someone before trying that as it sounds (at least to me) as if it would eventually cause some damage, possibly very quickly if you can notice just from looking at them that they aren't fitting well.

 

[TomTom]

Ive tried it.
There is no upside in power Im afraid, the head is the culprit.
Absolutely no wear issues with the different valve spacing though.
No need for excessive piston pockets, you are mistaking for G-cams or such that are 300 degree duration.
Squish isnt affected by any of that

 

[belter]

i fitted them to this one, in place of the sps inlet. not sure if it was worth it or not. we were trying to pull the power peak down a bit too maybe.

i'm not sure that i like the final angle of the curve just below the peak. to my mind that shallow angle running up to the power peak is an indication of cam / head mismatch of some sort, but i've not ever had the chance to really do anything about testing for it. my m400 has the same thing for instance, wheres advancing the cam got rid of it to some extent on that. changing to a shorter duration inlet cam on it (620) made it peak earlier with more of a traditional peak curve shape. but now i'm rambling.

seen it also on moto guzzi v11, which have a cam derived hole around 4,000 rpm too.

thoughts tom?

BikeBoy.org - Ducati 996SPS with bigger valves and more compression

 

[Namor]

Ive tried it.
There is no upside in power Im afraid, the head is the culprit.

Did I miss something or do you mean that dropping the R cams into a 996 engine doesn't make more power?

I thought R intakes with standard intake cams used for exhaust was worth some power.

 

[belter]

a 36mm valve theoretically only needs 9mm lift, so you're probably better off with the bit more duration you get from the sps inlet as opposed to the r inlet.

 

[JEC]

My question would be are you paying a premium for the R cam or is the same or less than SPS? If it's a steal, go for it. If its the same price or more than SPS why bother?

For the record SPS cams are well worth it in the 996. Especially with extra compression. I'm running Pistal R2000s with 1.2mm squish, T1 SPS cams with 110/110 centrelines in a 996 engine with light flywheel, alloy slipper clutch and adjustable alloy cam pulleys. It's a superb combo and it runs on pump gas.

(Before someone says I'm going to blow a ring land I've already put 10,000 street miles on these pistons. Proper tuning and the right cam timing is key.)

 

[seven4niner]

My question would be are you paying a premium for the R cam or is the same or less than SPS? If it's a steal, go for it. If its the same price or more than SPS why bother?

That’s pretty much the guts of it...,well, for those on a budget anyway.

R cams may not be the absolute dogs danglers but when you can pick up a complete 748R engine for the price of a set of 996SPS cams it makes a fairly compelling argument.

 

[brian98]

bottleneck

Tom/Brad: would the setup using 748R cams make more sense if the valves were increased to 31/37?

And to those that ask about cost of 748R cams...yes: I have cams already lying around. (so cost is "free")

Appreciate everyone's thoughts

Brian

Ive tried it.
There is no upside in power Im afraid, the head is the culprit.
Absolutely no wear issues with the different valve spacing though.
No need for excessive piston pockets, you are mistaking for G-cams or such that are 300 degree duration.
Squish isnt affected by any of that

 

[belter]

jmo - the 748r cam has a lot more lift, but less duration, so you'd need a lot more inlet flow to make the 748r inlet cam work.

the 748r exhaust cam would possibly make more power, not sure if the capacity will overcome the mid range hole you get with the 748r.

the longer duration cams will help overcome the lower head flow, but it will generally lead to the narrower power band.

whereas a testa will make more power with less duration due to the heads working better.

but, to clarify - what cams do you have? i was thinking you had 996 sps cams. if the choice is std 996 cams or 748r i'd go the 748r. are the heads std? the 748r inlet won't have any more lift at tdc than the std cam i don't think. the exhaust is longer at the closing end, that might give a p-v issue.

 

[TomTom]

There are variables enough to this subject everyone is correct at some point. that is the only thing Im willing to say is certain.
The more you understand the more you understand how broad the 'problem' is

Is it just flow in a bench that matters? Nope
Is longer blow down better for top end ? Nope

Things are proving inconsistent even if youre being super meticolous, which goes to prove it is not an easy task answered in a line or two.
And that is from doing test on Ducatis for well over a decade in the Dyno.

However, if you do keep on trying you may stumble on a super-combo, and that is likely to get talked about, but the important details are never there and then its useless as such

 

[Namor]

So purchasing his cams and placing them in a 996 isn't going to so much?

What sort of exhaust cams would work with the 748RS cams?

I ask for other's sake, because he isn't asking much, and in another 10 years they will be impossible to find.

 

[xracer]

There are variables enough to this subject everyone is correct at some point. that is the only thing Im willing to say is certain.
The more you understand the more you understand how broad the 'problem' is

Is it just flow in a bench that matters? Nope
Is longer blow down better for top end ? Nope

Things are proving inconsistent even if youre being super meticolous, which goes to prove it is not an easy task answered in a line or two.
And that is from doing test on Ducatis for well over a decade in the Dyno.

However, if you do keep on trying you may stumble on a super-combo, and that is likely to get talked about, but the important details are never there and then its useless as such

This is a subject very close to my heart. The never ending possibilities with things that cause the air to flow or not and all the interactions of valve timing/lift/duration with different exhaust dimensions and intake configuration all play for an extremely complex equation. Even intuitive thinking sometimes goes out the window and sometimes you just have to accept what is and go away scratching your head.
You are in a very enviable place Tom with the equipment you have around you. Learning these things is fun and frustrating at the same time.