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I know about the water port and the round intake runner difference. But what caught my eye was the open cumbustion chamber for lower CR Vs the 944 4v head that has a closed chamber head. And the exhaust stud configuration. Has anyone ever attempted to use a 928 4V head on the 944Turbo? If it's a turbo set up I was thinking a custom intake would need to be made anyways using the 928 flanges. And the water port can be drilled and filed clean like the 944S. I only ask because I'm starring at both heads. And the 951 exhaust headers fit a 928 head perfectly. So if you had spent all the $ on an 8V racing header set up and want the 16 valve head, could the 928 head be used with these minor mods? Update: Nope, but they can work with a 16v stage two headers using 8v head flanges.
Last edited by Humboldtgrin; 01-09-2016 at 11:20 PM.
I had this same thought recently, I tried asking on the 928 side about port diameters but didn't get much info. Could you measure the two for comparison?
Think you could CC the 928 chamber? I believe the 32v 928s were basically flat-top pistons.
I think the 928 head could be good on a 944 block because the ports are smaller, perhaps that would lend itself to higher port velocity = more lowend that the 944S desperately needs.
As far as the manifolds bolting on, I believe there was a sort of transition in 85-86 on the 32v heads of the 928 regarding the exhaust studs, I think after 87 they went to a 3-bolt flange like the 944?
I'm also going to see how far off the turbo intake manifold is to this 928 4V head. That would be cool if it lined up (drill and tap a few holes). Will see tomorrow when the sun comes back. Kinda suprized after 30 years of these parts being around I have hardly any feed back on a mod like this.
Search for older posts, we discussed this on here with ptuomov a while ago. The bottom line was it would be a big waste of time and money.
I'm going to see anyways. Maybe the 928 85,86 4V head will work and not the 928 87+ 4V heads. I don't see that much of a difference for it to be a big waste of time and money. And I bought the car for $102.50 with both heads in the back of the car. So I feel it's worth checking itno further.
Also I have the cams for both heads.
Subscribed. I think the early 4V 928 head is worth exploring. Kudos to Humboldtgrin for taking the initiative to see how this may pan out with the early head.
Let us know how 928 cams work on a 4 cylinder engine...
It seems Thom has a funny side. Sorry not into bending valves right away. The "S" cams fit perfectly from the 944S. The turbo intake is a little off and has much smaller holes. But with a little fabrication, some 928 flanges with custom intake, or cut off the runners on the turbo manifold a use the plenum, looks like it will work just fine. looks like the 944S fuel rail will fit with minor adjustments if any for mounting as well. Looks like I'm going to biuld myself a 928 DOHC turbo head set up for the 951 2.5L block. Just to show it can be done. Wonder why no one has done this before? I'm still not seeing the "big waste of time and money". I'm seeing a very possible, and most likley huge power gains thou. I will keep all posted. May take a while to put together due to funds. But I will.
False: Also not all 928 32 valve heads were 100mm. The 928GTS DOHC has the 104mm bore block. Making it a 5.4L not a 5.0L.
Last edited by Humboldtgrin; 08-21-2015 at 01:25 AM.
Also not all 928 32 valve heads were 100mm. The 928GTS DOHC has the 104mm bore block. Making it a 5.4L not a 5.0L.
Nope, all were 100mm
The GTS 5.4 got it's added cc's from a longer stroke...85.9mm
Incidentally it's the same stroke that the newly-developed hybrid strokers run
Just when Porsche could have made it easier by crossing the large-bore design from the 944 to the 928 and making the 5.4 that way, they kept them small and made a new crank instead
You could also regrind 928 cams to work on a four cylinder. I know its a little pricey to do a 968 or S2 regrind so it may be more costly to completely change the lobe locations. See if you can get a quote at a few cam grinders. It could be cost prohibitive but it may be worth a look.
Nope, all were 100mm
The GTS 5.4 got it's added cc's from a longer stroke...85.9mm
Incidentally it's the same stroke that the newly-developed hybrid strokers run
Just when Porsche could have made it easier by crossing the large-bore design from the 944 to the 928 and making the 5.4 that way, they kept them small and made a new crank instead
Dam I thought it was a .2 increase in bore on each side, same as the big bore on the 944 cars. Didn't research.
Also I'm going to have to spend $ for exhaust cam. The exhaust S cams I have has bad journals. So does the S head. So the last owner thought the 928 head would work but found out it won't. Fine with me its a parts car now. And cheap!!! And I have a nice 944S block identical to the turbo s blocks.😃
The heads I now own:
86 944nax2
86 944t x2
89 944 2.7
87 944S(bad exhaust cam journal)
85,86?,928 DOHC
Not to include the running 86 944na with of course a head on it from a turbo because I did the head replacement, I gave it to my freind for welding on my turbo's quarter panel.
I may have an obsession problem... And thank you for letting me know about the 928 GTS bore. Really thought it was 104mm for years without researching. I have to do more homework!!!
08-18-2015, 11:13 PM
928 4V head for turbo question.
