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Join Date: Jul 2005
Location: Atlanta
Posts: 693
2.8LS build

hey all, Haven't posted pics of this one yet, but it's about identical to one I built not long ago, only this one is for me as it's loading into the 74 Carrera (early RS flares) I'm rescuing. She just had a bare metal respray and of course lots of metal work hence the word 'rescue'. She was a basketcase, but lots of welding and light swearing later and she's where I want her to be. The goal here of course is a lightweight Euro-Carrera-look sleeper.


engine:
39mm intake ports, 38mm exhaust. thanks Craig! (cgarr)
65-66cc ish heads
1mm deck height
twin coil on plug
lightened crank etc
Carrillo rods
92mm 10.5:1 JE shelf pistons
7r case with all usual strengthening machine work
DC65 cam (thanks John!)
964 oil pump
Dansk full-bananas RSR rallye headers and muffler exhaust. may be a bit loud but we'll find out

AEM Infinity 6 brain is in hand but haven't needed to fiddle with that yet. Big ITB injection. Rasant is making a new full-sequential distributor sensor and crank wheel which is more accurate than the AEM hockey puck which I'm told tends to dance the signal around. It will be used once available, should be any week now....

Technical stuff:

Valve springs Craig used were from Cat Cams and installed at about 85lbs seat and 244lbs over the nose with these cams, which is still a bit stiff. I removed those and placed them in another high rev motor running a GE80 cam that needed them right away and they have been great. My company took it upon ourselves to dive deeper into the issue of valve springs to explore the issue as there really wasn't anything on the market that is of modern design. My engineer ran a stasis analysis with various cam ramp speeds, component weights, and lifts, found these engines do not need near the spring pressure some throw into these things. As most of you know many Porsche race motors ran stock springs, but cam ramp speeds were not what they are today, but still the stiffness some sell is just absurd and unnecessary. For my motor, I swapped those for new valve springs my company just had re-engineered and made in Australia which are about the same spec as the Cat Cam springs, maybe a touch stiffer over the nose. These springs will be available to everyone soon

There has been significant advances in valve springs over the past couple decades, primarily material and advances in testing, not just spintron nonsense but far more accurate stress and cycle testing against various ramp speeds. My guy in Australia is a mechanical engineer and does valve springs, and that's literally all he does. We primarily use him for making Ferrari stuff as some of you may know that's one of my professions. He's made springs for everything from 206 Dino engines to flat 12 formula 1 Ferrari engines, there is no one better and more qualified with these multi-million $$ old F1 engines. A couple companies in the EU want to take lead on distributing these but I will make sure US distributors have them as well. Craig (cgarr) has already reviewed them and given them his approval stamp. More info later.

Peak dynamic efficiency should be about 101-102% in the upper 5k rpm range meaning I'm really pushing compression ratio as I'm likely exceeding the already borderline static ratio a touch. We'll find that out too

Anyway, this motor should be good for 280 or so at the flywheel like the last one.

10k RSR tach is about done, can't go without one of those of course

Merry merry all










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Old 12-25-2017, 08:27 AM
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Functionista
 
manbridge 74's Avatar
 
Join Date: Jul 2011
Location: CO
Posts: 4,672
Considered a high tech coating for springs?

I keep hearing about some gains especially in upper rev range. I’d want to coat the rockers, cam and use modern bushings too
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Jeff
74 911, #3
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Old 12-25-2017, 09:16 AM
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Join Date: Jul 2005
Location: Atlanta
Posts: 693
These are coated with something, with what I have no idea. The Cat Cams units had something on them as well.

I should add I used loctite 515 on the webs rather than 574 as sort of an experiment this time. 515 has a higher tensile strength, and if we’re using the stuff on the webs as a form of additional strength for the webs then we should at least use something a bit stronger, but not too strong.
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Old 12-25-2017, 10:05 AM
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Under the radar
 
Trackrash's Avatar
 
Join Date: May 2007
Location: Sebastopol, The Republic of California. Land of wine and redwoods.
Posts: 4,493
Garage
Thanks for sharing. Can't wait to see the dyno sheet.
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Gordon
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'71 911 Coupe 3,0L outlawed
#56 PCA Redwood Region, GGR, NASA, Speed SF
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Old 12-25-2017, 02:50 PM
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