I have a 911SC 3.0 engine on my 914/6 and trying to determine correct intake manifold size for new 40 PMOs. The stamp for the engine model type is 930/10 which led me to believe it was an 80-83 RoW model. Which means the intake port should be 34mm. However when I measure the intake port it's 39mm.

So when I check the engine serial number, 6382839, according to some prior posts here the third digit means it was built in 1978. And that corresponds to the intake port corresponding to the 39mm listed in Bruce and Wayne's books for 1978 RoW 911SC engine.

I think I'll go with what I measured but I find it very odd.

Any of you experts have an idea of what is going on with this mismatch between the type and serial number?

Thanks,

Peter

Check the model number on the heads.

What's the date on the heads ??

spec numbers are average, you have a 78/79 large port 3.0..

The 1978 & 1979 SC had Large Port Heads

46x39mm intakes with 46 pmo. You can do 40 pmo as well, but unfortunately they don't have an intake that matches. Looks like the biggest is 37mm

A couple of folks have said check the heads for date or serial number. Any pointers where these numbers might be located? I crawled around under the car but didn't find anything.

Also I am told that I must use the PMO intake manifolds versus the old ones used with the Webers. Can anyone confirm this is true?

Again many thanks in advanced in helping me figure this out!

Not sure if this will help.

Pictures of Eng. in my 6 with the 46 PMO's
1978 3.0 SC big-port base (case, crank, rods, oil pump)
Custom JE Pistons, replated Nikasil cylinders, 9.8:1
New valves, 38/37 ports (stock)
ARP head studs & rod bolts
GE40 "Mod-S" cams
PMO 46 carbs & manifolds
JWE custom curve on SC distributor to match the carbs/cams
930 tensioners, idler arms--all rebuilt
Otherwise just everything new or refinished, redone, rebuilt



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You cant see the casting year or number as its on the intake side and will be under the shroud. If the shroud is off you can see it above the cylinder. Since you have measured you know you have large port or they have been ported.

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The big port engines (78-79 us an all ROW) use the 4R cis runner. The US small port heads use the 2R CIS runner. If you looking at installed engine with CIS on this will be the easiest to look at.

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john

Thank you all for your help! Much appreciated. I am taking the measurement at the intake on the sizing of my manifolds.

Appreciate all of the responses

to all of you

Can you double check the third digit of the engine number? By my reading of the PET for the SC a 930/10 engine should have a 1, a C or a D as the third character.