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TOPIC: Newbie needs camshaft ID help!

Newbie needs camshaft ID help! 27 Jan 2017 15:21 #19514


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  • Kermit928S's Avatar
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Help, I have a dumb question! I'm new to Porsches and am working on my first 928S. I used to rebuild Mustang fastbacks back in the day ( '79 to '84; yeah, I'm old) before I knew very much about Porsches. But, I must admit that I find the Porsche part number scheme a bit confusing at times. In the case at hand, I'm jumping right into the "euro hybrid" thing (yeah, probably not what should have been my first Porsche 928 project). I have an '85-'86 block with crank, pistons, rods, etc., and have a pair of cams "lined up." The question involves the casting marks on the "euro" cams. Among euro cams are the (1-4) 928 105 187 03, and (5-8 ) 928 105 188 03. The cams I have found have part numbers 928 105 187 0R (or OR), and 928 105 188 0R (or OR). I have the Service Manuals, PET, and "Models Dimensions Tolerances" manual, but I have found NO listing for a 928 105 187 0R (or OR) nor 928 105 188 0R (or OR) in any of these sources! What gives? :blink: Does anyone know the significance of the 0R or OR designation instead of the 03 designation? Does this indicate a different grind?

Thanks in advance of sharing any sage comments.
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Newbie needs camshaft ID help! 02 Feb 2017 12:48 #19522


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Hello Kermit928S,

Sorry, I don't have the cam identification information that you requested. My 1979 Euro Track car has a "hybrid motor" ... I'll explain what that is, at least in my application.

Until model year 1987, the Euro/ROW Porsche 928s weren't fitted with catalytic converters and had different engine control. The Euro "S" versions where higher powered than the US counterparts.

Displacements varied too:

1. 1978 - 1983 Euro/ROW: 4.5 liters with K-Jetronic CIS injection
2. 1978 - 1979 US: 4.5 liters with K-Jetronic injection
3. 1980 - 1982 US: 4.5 liters with L-Jetronic injection
4. 1980 - 1983 Euro/ROW "S" type: 4.7 liters with K-Jetronic injection (300 HP)
5. 1983 - 1984 US "S" type: 4.7 liters with L-Jetronic injection
6. 1984 - 1986 Euro/ROW: 4.7-liter 16 valve LH-Jetronic fuel injection (310 HP)
7. 1985 - 1986 US (and Euro no-lead fuel optioned) 5-liter 32 valve LH-Jetronic fuel injection
8. 1987 - 1991 world-wide: 5-liters 32 valve LH-Jetronic fuel injection
9. 1992 (ROW) & 1993 - 1995 GTS: 5.4 liters 32 valve LH-Jetronic fuel injection

The 16 Valve non-S motors had smaller valves than the S heads. Thus, in addition to a more aggressive cam profile, the Euro S motors had the larger valve sizes (same as the 944).

So my hybrid has the following attributes:
a) 1985 5-liter block
b) 1980 Euro S intake manifold and throttle body (larger non-S and US-spec)
c) 1980 Euro heads (with larger valves) and more aggressive Euro S cams

The benefit of all of these items are:
- more displacement (5-liter vs. 4.7 or 4.5 liters)
- more airflow into and out of the cylinders
- higher compression ratio

The pistons in the 1985 block were designed for 32 valve heads, so to accommodate 16 valve opening the pistons have to have special recesses cut into them.

There may be some benefit in installing Euro cams in a US engine, more power due to the cam profile. However, the higher power of the Euro engine came from several things:

- higher compression ratio than US engines
- larger throttle body and intake tubes
- larger valves
- more aggressive cam profile

There are some technical problems to create a complete hybrid motor based on an L-Jetronic fuel injection system. The L-Jet air flow meter was not designed to interface with the larger Euro S throttle body. So the smaller diameter AFM must be machined to better flow to a larger throttle body intake. The L-Jet hybrid would require the use of the 1985 - 1986 intake runners to accommodate the fuel injectors.

This is why I kept the CIS injection system in my 1979 928 even though I could have upgraded it to L-Jetronic.

I hope this helps everyone understand the "hybrid" concept.
Rich
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1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue
1979 928 5-liter track beast
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Newbie needs camshaft ID help! 02 Feb 2017 18:34 #19523


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Thank you very much Rich!

I have Euro S heads, with new valves (Swiss "Intervalve" 40mm/45mm), Euro S cam towers with 928Motorsports cam gaskets, and a Euro S spider with throttle body to go with my '86 5.0 lower end. So, I'll be trying to accomplish what you did. I especially appreciate the info on the MAF and L-Jet; that sounds like a good solution. I have read that others have actually put the largest Chevy MAF on with a special interface system for CIS, but I don't know the details about that.

What did you use for engine gaskets and seals? I have read that these are Porsche's "weak link," resulting in "inevitable" oil leaks. Did you go with OEM or aftermarket German parts or something else? If you don't mind, I would also appreciate any other info about the technical issues regarding your Hybrid engine build and parts selection between 5.0 or 4.7 parts before something goes sideways (timing belt & tensioner, OEM or O-ring or steel composite head gaskets, etc.), and where did you have the fly cuts on your 5.0 pistons done? Hope all that isn't too much of a bother.

If anyone else has done the Hybrid engine build, I would also appreciate your input.

Again, thanks for the help Rich.

Pete (Kermit is from my daughters' idea that the H4 headlights up make the shark look like a frog).
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Newbie needs camshaft ID help! 07 Feb 2017 22:30 #19528


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It took a while to look at history. I used 928 Motorsports Multi layer steel 0.065 thick 100 mm bore head gaskets. Other gaskets used were OEM Porsche.
Rich
Membership Chairman
Charter Member
1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue
1979 928 5-liter track beast
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Newbie needs camshaft ID help! 08 Feb 2017 07:57 #19529


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Thanks very much Rich, I really appreciate your taking the time to dig up the info. :) I think I'll go with the 928MS steel head gaskets too.


Pete
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