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Looks correct. California cheater correct. Awesome.
How about them runners?
Thanks very much, yes the runners, there is some complexity there, the 90 degree turns are done in 2” pipe which has an ID of 47.6 mm and then I need to taper them down to about 44.5 mm ID which is the next size down in size. The machinist needs to make those transitions pieces after I give him some instructions after a basic mock up. The 44.5 mm pipe transitions to 43 mm at the head. I will port the flange plate from it’s standard size (40 mm) which is a scavenged 944 part. This also allows the use of the more modern fuel rails similar to the S4 etc.
Thanks for the comments, regarding rubbing some grunge on to the manifold don’t worry there plenty of that here. I have to now clean and grind the heads for welding. This a very big job, all of the combustion chambers are getting welded up along with the valve and spring pockets. Then they will go to the heat treater.
Hydroblasting the head.
Started welding up various ports not used for the 928
what is the valve-to-valve spacing int/exh on a 928, vs a 944?
You are correct, it’s different and going from memory the nett difference is 1.5 mm in valve spacing. The other difference which flows from that is valve placement in the bore. I will post a pic of the head, it has alloy plugs pressed into it to be welded up. This will allow us to move the valves and use smaller guides. That head is for the big bore engine 107.95 mm or 4.25” in the U.S. It’s probably use a 2.18” intake......We will make new billet cam boxes to accept a modern hydraulic tappet.
I may not do this next lot of welding, my machine is only 200 amps and I don’t have helium, helium is expensive and if I don’t have the amps it’s money wasted.
The chambers are being welded to fix corrosion and create a quench area the 2.7 head doesn’t have. There is also plans for a diffuser where the head was flat between the valves. Head will need to be straightened and heat treated. I’m planing on 16 mm of valve lift which is about the maximum permitted with a beehive spring which I need to run with the hydraulic tappets.
Plugged up ready for grinding, then welding and then straightening. We will then move the valves after the surfaces are ground of course.
2.7 litre head plugged ready to be ground out then welded then the valves will be moved to optimize the valve placements
928 head, spring seats to be welded up and the ports raised. This is possible due to the solid tappets which allow for the spring to be raised in the head.
More welding needed but one 944 specific water port welded. The plug seem for the round hole.
This the start of the changes to the chamber.
‘The welding is not finished, as I mentioned, there is a need for more amps, I will also weld around the exhaust part of the chamber to shape it better, it will then get CNCed after a prototype is produced.
your project is very interesting.
what more modern lifters are you going to use? something else in 38mm or a different size? stock 928/944 DOHC use a 35mm which is also the size used in Subaru and VW amongst others, huge availability.
do you think the valve spacing on an early 928 head is "close enough" that a 944 cam would be able to actuate the lifters without much problem due to off-center misalignment?
since you're doing welding stuff to the chamber what are your thoughts on a proposed experiment i came up with once upon a time?
I found it interesting that very early US 4.5/4.7 928 heads had a similar sort of "heart shape" that later went away.
Originally Posted by V2Rocket
The 944 chamber is of course a wedge head similar to the various Small-Block engines, so I thought to look at the most-highly developed small-block head offered by an OEM...the GM L31 Vortec. Vortec heads, with the other required supporting parts (specific manifolds etc), are basically a +50-hp bolt-on for non-Vortec engines. These are said to be the best-flowing SBC head GM ever made, but what interests me is the chamber shape.
It is said you can take out 4-6 degrees of advance after switching to Vortec heads...they make more power and get better mpg than the pre-Vortec heads, I'm guessing the shape makes for some strong swirling around each valve as the piston comes up.
Here is a comparison of the pre-Vortec chamber (left) vs Vortec chamber (right). What is interesting is that these have about the same nominal chamber cc despite the difference, so CR is comparable.
And here is a picture of a slightly modified 944 chamber...
Now while not identical, you can see the 944 chamber is similar in shape (although flipped around, since SBC spark plug is on exhaust side) to the non-Vortec head...what I want to know is, what might happen if a 944 head were welded up opposite the plug boss to have a similar "heart shape" chamber? Might this be a worthwhile experiment to try to take out some ignition timing?
your project is very interesting.
what more modern lifters are you going to use? something else in 38mm or a different size? stock 928/944 DOHC use a 35mm which is also the size used in Subaru and VW amongst others, huge availability.
do you think the valve spacing on an early 928 head is "close enough" that a 944 cam would be able to actuate the lifters without much problem due to off-center misalignment?
since you're doing welding stuff to the chamber what are your thoughts on a proposed experiment i came up with once upon a time?
I found it interesting that very early US 4.5/4.7 928 heads had a similar sort of "heart shape" that later went away.
So the tappet diameter is 28 mm, they weigh 30 grams with oil. They have been tested in the BMW Judd LM engine at low lifts to 10,500 rpm. My engine will only go to 8,500 rpm max. However the lift may be an issue but I feel it should be o.k because the parts in the valve train are very light. The intake valve is in the range of 2.18” to 2.20” and weighs around 70 grams. The beehive spring and Ti retainer will also be light.
Porsche radius tappet
I think the curvature of the radius is 127 mm from memory. I’m not worried about the valve spacing, we will have to make our own cams and cam boxes. We won’t use the design that Porsche used with the cam having to be passed through the bearings. We will need 16 mm of lift and that is best done with bearing caps. Anyway, let’s get all the welding done and tidy up the heads and get the new guides drilled before getting too excited. The heads then need to go off to the porter who will fit the copper seats and have the chambers shaped then cut with the CNC. I suspect that won’t be complete till the end of the year if I’m lucky.
Greg, I think you should carefully check one thing about the radiused lifters for the high lift (16mm) cams. Make sure the cam lobe is fully travelling on the lifter. If the cam lobe will be outside the lifter (riding on the edge) the cams will go down quickly.
Åke
I would reconsider going with titanium, it is a very soft metal and wears very quickly in an engine. I would look into chrome moly steel parts as they can be made almost as light as Ti but last a lot longer.
Lindsey Racing sells beehive springs with chrome moly retainers if you don't want to custom make it yourself.
I would reconsider going with titanium, it is a very soft metal and wears very quickly in an engine. I would look into chrome moly steel parts as they can be made almost as light as Ti but last a lot longer.
Lindsey Racing sells beehive springs with chrome moly retainers if you don't want to custom make it yourself.
You are correct about titanium, in fact many retainers in NASCAR are 300M. However, depending on the spring package sometimes only Ti is available. I will seek advice when it comes to decision time. The intake valves will be Ti however, in the engine that is getting the welded 928 heads with the piston guided rods, I have 7 mm stemmed intake valves that are currently uncoated. The plan is to get the intakes coated with CrN and then hopefully DLC, the dlc version costs $65 per valve. Not cheap! However wear is then very low and I will get the stem tip and keeper groove also done with CRN. I have the current tech in valve seats, both will be made from Moldstar. That is also expensive at around $35 per seat but apparently is the bees knees. So $100 is just speciality parts and coatings, still have cut the seats on the valves and seats. These days most valves get 5 cuts and seats 3 to 4. Can’t imagine that being cheap either. For the 2V 928 head engine I have steel beehive retainers from Comp Cams, they weigh 10 grams. I also have Comp springs but I think I will change these for PSI.
DLC coated intake valve
Bottom of valve
The exhaust valves are a super alloy from Ferrea, I think they are Nimonic?
I changed the front intake runner design (5) I think this looks better, I want to the air to go into the port straighter but.....
First iteration
I think this looks improved.
So obviously this is just taped together, I need to solder the trumpets in permanently and then grind them I to a uniform length. Then I will fine tune the runner lengths. I also dropped one of my U Bends to the machinist which I now need to get back to finish the manifold. The plan is to weld each runner getting strong penetration and then grinding internally and externally and perhaps a polish. I will then weld the runners to the manifold flange plates. I then think I should do a detailing job to complete any tidy up areas. To preserve the finish I will then get them anodised in a satin finish. I suppose the runners will take a weeks work to finish also. So two weeks for this complete manifold but remembering I had the parts ready to go, that makes a big difference.
Looking pretty good, straighter than factory
A rather bent intake runner
Missing a pipe
Look at the height of the plenum in relation to the air box. It dips downwards, this is because Porsche uses the same runners reversed each side.
Now look at the modified plenum, it takes advantage of the bonnet/hood height better.
02-16-2018, 02:46 PM
