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Early 928 to 944 Head swap

 
Old 05-23-2011, 04:58 AM
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pjburges
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Default Early 928 to 944 Head swap

Ok so whats the deal here. I measured the valve stem center to center distance and yes its different.
The oil ports match,
Coolant ports match enough I can make them work.

I have a pair of fresh rebuilt 944 heads on the shelf, and they look WAY beefier than the ones on this M28/01 1979 928. Valves are bigger, ports are better shaped and bigger, chamber shape is better and you can actually SEE that it generates better swirl via the carbon deposits. OHH. And it has beehive springs compared to the 928's wimpy ones. So wtf man??? I thought the 928 was the expensive motor??? I can tell the 944 heads with those flat top pistons in the engine would yield an awesome compression ratio too...

The 928 motor is a euro - whole car was crated from germany and has flat-top pistons. Does this mean higher compression? Or still just 8.5:1?

Is it worth it to try to swap the 944 heads on the 4.5L? Will valve shrouding be a problem? Can I run the 928 cams "off center" of the valve stems? Supposedly a 79 928 thats euro has favorable cam timing compared to the US versions...

At the very least with these 944 heads doing nothing, and if my springs are worn out on the 928 head, should I swap on the beehive units from the 944? They appear a direct fit.

Thanks for any pointers guys!
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Old 05-23-2011, 05:56 AM
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slate blue
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Well I think you will have trouble without custom cams as the intake is placed in the same location on both heads but the exhaust is moved towards the edge of the bore. So you can't move the cams per say. Where do they contact the lifters with this new spacing? As the 928 has an offset cam lobe to lifter arrangement to rotate the lifter in the housing. Maybe it will just be on the other side of the lifter. I haven't given it any thought.

The 944 head will flow better than the early 4.5 heads but putting the 944 valves into the 928 head and making the right changes to blend the seat could be even better. I wouldn't increase the port size till I saw how it ran.
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Old 05-23-2011, 05:57 AM
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No point, no special gains, and the 4.5 Euro is pretty much the same if not the same as the early US. I don't think any engine internals are different, but its not a platform for performance, so haven't paid much attention to all the details. Pretty much the answer to all your questions is no.
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Old 05-24-2011, 12:23 AM
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Euro has identical cams to the Euro S with just a hair less lift and exhaust duration - so it has a distinct advantage over a regular 4.5L. I could easily chuck these cams up in the lathe and grind the off the base circle to get identical lift to the Euro S cams and nearly the same timing (sans exhaust).

Let me rephrase the question. I have a pair of 928 heads already pulled from the OB. I have a pair of sitting 944 heads on the shelf. I'm going to freshen up two heads. Why should I NOT use the 944 heads? They are clearly higher flowing better designed units.

-Paul
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Old 05-24-2011, 07:29 AM
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Borrowed from one of Porkens old posts. 78 and 79 US and Euro used the same cams.

78-79 US (ROW) M28-3/4 (1/2), [email protected]/[email protected] (HP229/TQ250)
Stamped: 155.07/156.07
Intake opens: (-8) BBDC, closes: 55 ABDC, duration: 227, centerline: 121.5 ATDC, advanced: 6.75
Exhaust opens: 38 BBDC, closes: 2 BTDC, duration 220, centerline: 108 BTDC
Overlap: (-6), separation: 114.75 {extremely wide}

80-82 US (ROW not S) M28-13/14/15/16 (09/10), [email protected]/[email protected] (HP229/TQ271)
Stamped: 173.01/174.01
Intake opens: (-12) BBDC, closes: 48 ABDC, duration: 216, centerline: 120 ATDC, advanced: 8.5
Exhaust opens: 32 BBDC, closes: 6 BTDC, duration 218, centerline: 103 BTDC
Overlap: (-6), separation: 111.5 {moderately wide}

80-83 ROW S M28-11/12, HP300/TQ263
Stamped: 187.03/188.03
Intake opens: (-9) BBDC, closes: 52 ABDC, duration: 223, centerline: 120.5 ATDC, advanced: 6.5
Exhaust opens: 37 BBDC, closes: 2 BTDC, duration 219, centerline: 107.5 BTDC
Overlap: (-7), separation: 114 {wide}

83-84 US S M28-19/20, [email protected]/[email protected]
Stamped: 203.00/204.00
Intake opens: (-11) BBDC, closes: 46 ABDC, duration: 215, centerline: 118.5 ATDC, advanced: 8.5
Exhaust opens: 25 BBDC, closes: 2 BTDC, duration 207, centerline: 101.5 BTDC
Overlap: (-9), separation: 110 {moderate}

84-86 ROW S M28-21/22, HP310/TQ295
Stamped: 211.00/212.00
Intake opens: (-6) BBDC, closes: 54 ABDC, duration: 228, centerline: 120 ATDC, advanced: 10.5
Exhaust opens: 43 BBDC, closes: 4 BTDC, duration 227, centerline: 109.5 BTDC
Overlap: (-2), separation: 109.5 {moderate}
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Old 05-24-2011, 08:40 AM
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Bob Devore ran the 944 heads on his 16 valve monster.
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Old 05-24-2011, 09:58 AM
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Pulled from 928 Specialists Technical Info Pages:
77-79 - 3-auto (US) 4.5L-16v M28/04 219 245 8.5:1 K-Jetronic 140 8.5 16 3373
77-79 - 5-man (US) 4.5L-16v M28/03 219 245 8.5:1 K-Jetronic 143 7.5 15.5 3285
77-79 - 3-auto (Euro) 4.5L-16v M28/02 229 250 8.5:1 K-Jetronic 140 8 16 3197
77-79 - 5-man (Euro) 4.5L-16v M28/01 229 250 8.5:1 K-Jetronic 143 6.8 15.5 3197
80 - 3-auto (US) 4.5L-16v M28/14 220 265 9.0:1 L-Jetronic 140 8.5 16 3385
80 - 5-man (US) 4.5L-16v M28/13 220 265 9.0:1 L-Jetronic 143 7.5 15.5 3351
81-82 - 3-auto (US) 4.5L-16v M28/16 220 265 9.0:1 L-Jetronic 140 8.5 16 3385
81-82 - 5-man (US) 4.5L-16v M28/15 220 265 9.0:1 L-Jetronic
143 7.5 15.5 3351
80-82 - 3-auto (Euro) 4.5L-16v M28/10 229 271 10.0:1 K-Jetronic 140 7.7 16 3197
80-82 - 5-man (Euro) 4.5L-16v M28/09 229 271 10.0:1 K-Jetronic 143 7.2 15.5 3197
80-83 S - 3-auto (Euro)
4.7L-16v M28/12 300 263 10.0:1 K-Jetronic 152 7.2 15.5 3197
80-83 S - 5-man (Euro) 4.7L-16v M28/11 300 263 10.0:1 K-Jetronic 155 6.6 15.2 3197

So if 928Specialists have their data right, with the same compression, the Euro 4.5L makes an extra 10hp and 5lbft of torque over the US engine. Even when US engines are raised to 9:1 compression, the earlier 8.5:1 Euros build more power, and still have the power and torque edge in the 9:1 compression version as well.

What makes this power difference if pistons are the same, compression ratio is the same and apparently cams are too? I thought it was a cam difference. Learn somethin new everyday!!
EDIT
Saw a similar thing to what you found on rennlist about cam timing:
Intake Lift Exhaust Lift Intake Duration Exhaust Duration
78-79 .435 .395 227 216
80/83Euro .472 .432 223 215
84/86Euro .472 .432 228 219
944Turbo .472 .434 228 220
87.944N/A .472 .473 228 228

Interesting stuff right?
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Old 05-24-2011, 10:18 AM
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I say go for it and post the details.
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Old 05-24-2011, 10:26 AM
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Go for it.

For data, use the tech spec books and WSM (incl 944).
See AO's signature line for links to tech spec books. ( I'll look for the 944 ones in my files).
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Old 05-24-2011, 10:28 AM
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78-79 are rated for 219bhp, not 229

What negative's are there to running a cam lobe offset to the lifter? No idea, not worth the risk IMO.

84-85 EuroS heads have the same size valves as the 951 head, why bother with the conversion?

Yes DEVEK installed 944 heads on a 928 engine, DEVEK also had custom cams available. I have yet to talk to anyone that knows for a fact this setup was run with stock cams. It could have been, but this question has been bounced around for 20 years.
It's very possible they built that motor before the EuroS heads were available.

FWIW I handed Turbo Todd a 951 and EuroS head, asked him in a blind taste test which one he would use. For more than a few reasons he found the EuroS head to be superior.
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Old 05-24-2011, 10:33 AM
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grind a flat crank and use the 944 cams and towers too!
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Old 05-24-2011, 10:51 AM
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Notice how the 944 Turbo cam and the 84/86 928Euro S cams appear to have the same timings in my above post?? If that data is correct I would speculate that those of you wanting to hot-rod your 4.7's or 5.0's could use a 944 cam tower with your 944 head, and use a 951 cam. Then we wouldn't be worried about this offset lifter crap as everything would line up, and you'd have the same cam timing as the EuroS and the same head/valves ports etc. Thats just speculation though because the cam snouts could be different. And isn't there a difference between a regular v8 and a 'flat crank v8'? That could be an unforeseen problem. Also - the cam specs for a late model 944 N/A are even hotter than the EuroS / 944T...

Here's what I'm going to do - since I already have the 928 heads out on the OB, and 944 heads on the shelf, I will take pictures and measurements of both, including measuring the cams with a degree wheel, and take pictures of how the lobes sit offset on the lifters, what the headgasket for a 4.5 looks like on the 100mm bore of the 944 head etc. I'll post all those pictures to this thread. Seems like the answer is "possible" but we are speculating and I haven't found any definitive answers on rennlist so lets see if I can post some!! Just may take a few weeks to get it all up here.
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Old 05-24-2011, 11:36 AM
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Originally Posted by Hacker-Pschorr View Post
What negative's are there to running a cam lobe offset to the lifter? No idea, not worth the risk IMO.
As long as part of the lobe is on center, being offset is a good thing, that's how to induce rotation.
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Old 05-24-2011, 12:38 PM
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Originally Posted by pjburges View Post
And isn't there a difference between a regular v8 and a 'flat crank v8'? That could be an unforeseen problem.
a wee problem indeed.

Your 90 degree crank is not compatible with the 4 cyl bumpstick.

Hence the flat crank reference.
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Old 05-24-2011, 01:27 PM
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Originally Posted by Mike Simard View Post
As long as part of the lobe is on center, being offset is a good thing, that's how to induce rotation.
IIRC they are not evenly spaced out, some lobes are closer to center than others with this combination.

One difference I remember is the valves on the EuroS head hare further away from the wall of the combustion chamber (valves closer together). The 944 head a lot more crowded (with the same size valves).

Todd made a comment he could fit a larger valve in the EuroS head than the 944
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