older CASES vs higher HP

Mr.R

Marvin,
Yes I told him my days of ridding over to Le Mans with 3 litres of Pro Boost in my back pack are now long gone, I actually did that in '02. 😯
I said that I'd probably go down the route that Chris/CJS and you have followed as it was after all a road machine, pointing out that Chris's work was already proven on these motors, that he'd already carried out the development work and spread those costs over all of his customers motors.
Saying that I couldn't afford to pay for the development work myself.
He replied that if I did get a set done by Chris he'd like to see them before I fitted them to the motor, along with a standard head to compare them with.

Pete has all of the latest CNC kit to modify any sort of head, alongside all of the traditional machine shop kit, inc' a flow bench and at least 40 years of experience in tuning competition heads upto World Championship levels.
Despite it costing his customers well over £10,000 for him to build/tune a 4 cylinder car motor, he's never 'Not Busy' having a 12 month waiting list for an engine built by him.

He'd been a bit put out when I wouldn't let him go the whole hog on my 916SP heads, saying that I'd read that it was an easy job to port these heads slower and they should make enough power as they were, after he'd fitted the new valves.
He supplied and fitted the valves, modifying the new Renault guides, BMW guide seals, opened out the inlet seats to take the 35mm valves/matching them to the ports, cut all of the angles, lapped the new valves, also supplying and modified a pair of BMW car exhaust valves to fit a pair of my Bevel heads and charged me a 'mates rate' of £300 for the lot.
The parts alone would have cost me more (getting on for double) from any Ducati tuning specialist in the UK.
To the car boys/racers over here Pete is the C.R. 'Axe' Axtell of their World, many top tuning shops/race teams put their head work out to Pete and then pass it off as their own handywork...
I've seen many lables/job cards tied to heads in his workshop inc' some from Factory teams waiting for his attention, the heads are stacked floor to ceiling in there.

Paul/Loony,
I haven't a doubt that he can do what he thinks he can with a pair of Desmoquatro heads, but haven't the cash to find out at the moment.
He really does have 'Guru' status over here, he's that good that all of his work comes to him via word of mouth and as I've said he's still got a 12 month waiting list.

Steve R

Mr.R

marvin wroteNot to start an argument but I think the one on the left is the better combustion chamber. I think you would be better off using the 748 heads that I unshrouded and contoured for you and flat top pistons. If you want more compression than 12/1 you could mill a little off of the heads. Hi dome pistons may give you a higher compression ratio but the flame travel is not as good as it has to burn "over the hump". 12/1 should be high enough for you in the MidWest if you plan on using pump gas as the ethanol sucks! just my 2cents.

Hi again Marvin,
Here's a link to something Phill911 posted some time ago on here and later pinged it to me via a PM a couple of months back.
Have a look at the combustion chambers on this Factory 888 bike, it was being raced in '91, so it's the same age as the left hand one in my pic's,
it's almost exactly the same as the 916SP head on the right side of the pic's.

http://www.finecars.cc/en/detail/car/46768/index.html?no_cache=1

Any thoughts on why the factory went down this route?
They later put this design into the road bikes, it can't have been about emissions on the Corse motor.

Steve R

marvin

I have no explanation why the factory went that route. Compression ratio/RPM,??

I can't help but think that if they were that good that all of the current engine builders would have gone the route that they went!

It will be interesting to have Pete take a look at Chris's when you get them and compare to stock heads.

P.S. If you take a look at the Testastretta heads they are more like John Hacket's. Of course they have a different included angle and very large valves.

Mr.R

Marvin,
PM sent to you.

Steve R

marvin

Mr.R wroteMarvin, PM sent to you. Steve R

Haven't gotten it yet!

Marvin

CJS

The clover leaf combustion chamber can produce fantastic power especially with flat topped pistons. I spent hours with my own personal bikes over the years welding up (adding) and removing them.

The conclusion is to get as much squish band area as possible with the required flow needed to make power. This is why some of the car guys are adding not subtracting meaning there is room for more material in there chambers without hurting the flow as much . Its not as simple as thinking more ribs and squish bands = more power . Every applicatoin is different. I have been messin around with 998 heads/squish bands and i can say this week i hit 150 Din hp with stock pistons and cams. I have barely seen top names get that with hi-comp pistons.

In the case of a 748 to get the required flow the ribs need to be removed but not the side pads. On an open chamber head such as a 996sps you can weld in approx 8ccs of weld in cloverleaf fashion without affecting flow and Power goes right up.

Back to a 748 The larger the valve the more of the side pad needs to be removed from a clover leaf chamber otherwise you get what i call poor valve performance . If you run into this situation its clear that by reducing the valve size makes more power or you can leave the large valve in remove some of the side pad and recover the compression some other way. I laugh sometimes as people do the DIY deshroud and remove from the wrong place. I had some 916/955 heads prepped by a top name firm with 37/31 valves . This made poor power . Once i saw the chamber it was clear poor valve performance was the issue . At flows 0-7mm of valve lift it was no better than a 33mm valve as the shrouding killed it.. I spent ten mins correcting there work and the 130hp he was promised by the other firm was instantly met and exceeded.

On the 130 odd hp 853 bikes i have built it is also clear the last little bit of cfm flow extracted by chamber modification makes more power . I can show this by flow vs dyno data with everything else being equal.

Everyone must realise you cannot see or predict where air travels. It must be tested and sometimes simply cutting in a larger valve ruins performance. In my work i dont remove any material that i havent tested first . Its also worth noting different engines like different things especially when engine speeds are different. In the car world piston cfm demand is lower than a bike spinning at 10k.

I had a pair of 888 heads sent in recently which were odd. One head was the same as a 916 and the other was like the one on the left in mr Rs pictures. How ducati fitted 2 different heads makes me laugh. The head with the ribs are better as the ribs/shrouding dont affect flow with this valve size plus they add compression (remember were not talking 748 now) 748 must have work done. The other heads with less shrouding must have been some type of homologation thing where ducati may have been thinking of fitting large valves for future racing (hence less shrouding)

Adding bumps or ribs directly between the intake and exhaust valve is also a way of controlling reversion and can make an engine run better at lower speeds by not allowing as much fresh charge out of the exhaust on cam overlap (cross flow) . I have seen engines with too long duration cams use this methord .

You may ask why the testastretta does not have the cloverleaf chamber . Its not needed as its so crammed with valves and delivers strong compression without anything needed to take up the excess room. The 998rs has a clover chamber which is crafted in such a way it does not affect flow but subtracts chamber volume.The filled in chamber does restore the compression ratio when used with its deep pocket rs pistons . There are no hard or fast rules . Find what a perticular motor likes and do not try to apply a system from what you hear to all other machines as that will leave people even more puzzled 😄 . In short what works for one will not work on another. Its possible to make extreme heads which deliver massive power under 10k, 9k or whatever but this requires a lot of welding, engineering and a very hi cost to the customer . If im paid enough money ill do it but in reality what average ducati customer wants to pay pay 1500 quid for the priveledge when a 600 quid version delivers bang for buck ?

Sorci851

Hello,
I am curious if installing 996 heads or 36/30 valves on an 888 engine would require machining of the valve pockets in the pistons. Has anyone here tried this set up before? What are the power characteristics like (assuming standard cams in place)? How large of valves can be installed before piston machining would be necessary?
Justin

erthmvr888

Hi Justin The engine cylinder/head studs are spaced different on the 996 engine cases than the 851/888/916 cases so you would have some work there. Trav

Sorci851

Hi Trav,
Oh yeah, I completely forgot about the stud spacing thing - no go on the 996 heads. Anyway, do you happen to know how large of valves can be installed in 851/888 heads without having to machine the piston valve pockets?
Thank you,
Justin

Mr.R

Machining the valve pockets in the pistons is a 30 min'/1 hour max job, the small amount needed to be removed will hardly effect the balance.
Fitting 36/30 valves to 851/888 heads will need bigger valve seats fitted $$$$'s.
I found a pair of bare 2nd hand 916SP heads on e-bay for £120, these already have 34/30 valves, (the same sizes fitted to the 888SPS and SP5's) but the inlet seats can be opened out to take 36mm valves without the need for new seats.

Steve R

Sorci851

Hello Mr. R,
Would the 916SP heads bolt straight onto an 851/888 engine, or would some modifications be required? I like the idea of running 34/30 valves on my project 888 engine. Also, in another post you mentioned Plasma brand valves as being good quality. Do you happen to know who sells Plasma valves, and what they cost? I searched online, but couldn't turn up any suppliers. I found some 34/30 valves at Ferracci here in the US, and also through Kaemna, but they are pretty expensive. I would rather go with bolting on a used head with 34/30 valves in lieu of expensive modifications to my 33/29 heads (92 851 heads).
Thank you,
Justin

Mr.R

Sorci851 wroteHello Mr. R, Would the 916SP heads bolt straight onto an 851/888 engine, or would some modifications be required? I like the idea of running 34/30 valves on my project 888 engine. Also, in another post you mentioned Plasma brand valves as being good quality. Do you happen to know who sells Plasma valves, and what they cost? I searched online, but couldn't turn up any suppliers. I found some 34/30 valves at Ferracci here in the US, and also through Kaemna, but they are pretty expensive. I would rather go with bolting on a used head with 34/30 valves in lieu of expensive modifications to my 33/29 heads (92 851 heads). Thank you, Justin

Hi Justin,
I answer to Steve, 😉 Mr.R is just my forum name as there's 1,000's of Steve's out there.

The 34/30 916SP heads will bolt straight on without the need to machine the valve pockets on standard '92 851,888,916 Strada or ST4 pistons, even when using 996SPS cams (that have a higher lift than Strada cams) with the inlets cams advanced to a 107 centreline from 119.5, there's close to 4mm clearance to the bottom of the valve pockets with the squish set at a tight 0.9mm.
If you go for larger then 34mm inlet valves, the pockets will need to be opened out (not machined deeper) to clear them.

This's what I found when building my '92 851/916cc motor, with 35/30 valved 916SP heads, (+1mm on the inlets) 996SPS cams and 0.9mm squish clearance.
On Brad Black's (Bikeboy) info page he went to 104/107 on a 33/29 valved 916 fitted with 996SPS cams.
I was being a bit conservative with 107/107 as I was using bigger inlet valves and a tighter squish, but having checked it all out now I sure that 104 on the inlets wouldn't be a problem.
There's lots of info' out there by people who know a lot more about this stuff than me, but I always double check for myself as it could cost me a lot of money, if it all goes 'Tits up'.
To keep the motor safe you don't want to go under 1.5mm piston to valve clearance.

The valves I used weren't 'Plasma' branded, they were UK manufactured plasma hardened Stainless steel race (quality) valves with wasted inlet stems below the guides/about as good as you can get short of Ti' valves, but have a much longer life expectancey over Ti' valves.

I'm just a bit busy at the moment, but could find out a price for you if you're interested, as I want to get another set of 36/30 valves for some "Full Monty"/balls out heads for my ST4 cased 984cc motor.

Steve R

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