ran across this on C-list
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Porsche 2.7S Complete Motor
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Reply to: anon-25489837@craigslist.org
Date: 2004-03-01, 4:05PM PST
Motor is complete including the fuel injection, distributor, flywheel, wiring harness. It ran until one cam went bad with a flat spot. The cam has been replaced and the motor is on a stand now. I would like $1,200 obo, or interesting trades.
Exhaust and oil cooler are not included, thanks for looking
it's NOT ok to contact this poster with services or other commercial interests
25489837
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Went looking on Clist and found this:
Reply to: brettvining@yahoo.com
Date: 2004-03-02, 3:28PM PST
73 914se completely restored to showroom quality. Green/black.
$30,000 I have all receipts. This car is a must see!
Dave,
What heading did you find that under?
Stay away from the thermal reactor 2.7S engines. Huge issue with heat warping everything. 1200$ is a decent price... but approach with caution.
B
How the hell do you eat a cam lobe on a Six? Only way I can think of is clogged oil passages--which means Bad News for the rest of the motor....
--DD
It had WebCam lifters in it...
B
The 2.7 sixes are reliable as long as they're not run with the stock thermal reactors. If it was just pulled from a '75-'77 911, however, it's a core engine that almost certainly needs a rebuild. The thermal reactors were perhaps the dumbest idea Porsche ever came up with. It sounds like this engine had some serious problems, and it was only patched up.
N'kay, someone wanna tell about the thermal reactors?
I have a 2.7 in the garage- going to a new home soon- but I like to know all I can.
I've worked on a few /6's and know my way around stuff- but without sounding stupid (too late?) what and where are they located?
The 2.7 I have had many upgrades and was well maintained and running when removed.
TIA
Bob O
CA-spec 75-77 911s. Possibly 76-77 US-spec? Not sure on that.
They're part of the exhaust. They heat up the exhaust gases a lot to finish burning off any leftover hydrocarbons. Sometimes, at night, you can actually see them glowing a little underneath the car. They generate enough heat that they tend to cook the engines attached to them....
--DD
I think they were used on all US '75-'77, not just CA. Federal regs got a LOT tighter in '75, and CA switched to tighter still standards that same year. If you look, you'll notice that very many cars suddenly had catalytic convertors in '75, like the 914 itself.
Thermal reactors were what a very few manufacturers chose to use instead of catalytic convertors. None of them used them for long, partly because they didn't work as well as catalytic convertors at removing emissions, and mostly because they generated such incredible underhood temps. Big cast-iron things designed to get hot and stay hot, like 900-1100dF hot. The idea was, where early catalytic convertors use a platinum catalyst to promote reaction of HC and CO with O2 to create H20 and CO2, the thermal reactors would do the same thing, but with heat alone.
Why a bunch of German engineers ever thought it was a good idea to take an air-cooled engine already stretched to its limit and place a 900dF cast-iron block next to it, I don't know. The '74 2.7s worked fine, as none of them had thermal reactors. The later ones expired with pulled studs, worn-out guides, etc in such a short time that Porsche got a very black eye with many US owners. To make amends, they stuffed the Turbo case in the '78 3.0SC along with catalytic convertors and very mild tuning, and as a result, the 3.0 is one of the most durable 911 engines of the entire series.
If you ever wondered why mid-70s 911s are cheaper than earlier or later cars, now you know. If you're just looking for a core to rebuild, the 2.7 is generally cheaper than others, and costs about the same to rebuild, so they're a good deal as long as you're going to fit them into a car that doesn't require you to run the stock thermal reactors to meet local emissions regs. If you're looking for a Six you just want to plonk into a 914, I'd use a 2.2 or a 2.4. They're much lighter than the 3.0 (magnesium v. aluminum block), and generate plenty of power for the light 914, and they're going to be cheaper than the 3.0 or 3.2 engines, to boot.
Not cheep for free.
Ask yourself: "Where did the lobe (s) go?"
Perhaps this was true in PA, but not in CA. All but a very small handful of cars sold in CA in '75 had catalytic convertors. Unleaded gas had to be widely available by that time.
Figuring out the engine management wasn't really Porsche's doing. Bosch was doing all of that work. The '74-'77 cars all used CIS, as did the '78-'82 catalytic convertor cars. The difference was the later systems used an O2 sensor, where the earlier systems were open loop. The earliest catalysts available didn't require a fully closed loop system (and suffered for it, dying relatively early). Given the 914 never used thermal reactors, but used catalysts from the start (in 1975, with L-Jet rather than K-Jet/CIS), the knowledge of how to use them was readily available to Porsche from both VW and Bosch. Hindsight is 20/20, but given the public reaction, and given Porsche's reaction to that (the SC), I'd say that they didn't realize at the time how bad the problem was going to be, and regretted the decision.
Company politics was no doubt involved heavily. This was also the period the 928 and 924 were being introduced, and factions within Porsche were seriously trying to kill the air-cooled rear-engined cars completely. They certainly didn't realize at the time that it would be another 20 years before that happened.
Of course, we need a Pic. This is a thermal reactor off a 76 turbo.
The inside of the barrel part is supposed to be filled with some sort of system of ceramic plates -- which heat up and do something passable with the exhaust that comes out to make the smog folks dance in their booties -- but imagine having one of these suckers placed up nice an tight below the cylinders generating massive heat ....
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