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Another 2.7 vs 3.0 question - 2.7 experts please chime in

I need help from the collective wisdom here. I've read Wayne and Bruce Anderson's books and just about every thread here on the 2.7 vs 3.0 debate. However it's 2018 now and finding a good cheap used 3.0 motor is not as easy as it was back in the day. So I'd like to remove the "just buy a good used 3.0 and forget about rebuilding your motor" argument for now.

Here's the deal.

I have two motors -
1. My 2.7 that's original to my '75 911. Appears to be 100% original, never rebuilt. It runs well but it smokes and leaks more than my weird uncle Stu.

2. A '81 3.0 motor that appears to be solid but has 1 broken head stud. This motor was reported to a good runner and appears to have had a top end rebuild at some point, but they didn't change the case studs to steel ones.

Here are my assumptions - what would you do?
1. I assuming that both motors will have to be rebuilt with the case split. I might get away with just a top end on the 3.0 but I would want to split the bottom end to check condition since it doesn't appear to have been split.
2. I know the 2.7 will require more expensive machine work than the 3.0.
3. The 2.7 is the original motor to my '75. My '75 is undergoing full bare metal rebuild and steel backdate. It's going to be a really nice car but not stock original. I'm looking to build a fun and solid driver that I'm going to keep forever.
4. I plan on keeping the bottom end stock and going Megasquirt EFI and EDIS with cam change. Not sure if I want to change pistons / CR at this point as I'm trying to keep some money in the bank account. I'm looking for 200-225 hp with excellent drivability and reliability.
5. Seat of the pants fun, great mechanical 911 sounds and throttle response are my primary goals over HP and speed.

I know that financially the 2.7 will be more expensive to rebuild. However there's something awesome to me about a hot 2.7 vs a stock 3.0 in my book. Also, the 2.7 is the numbers matching engine to my 911 so from a value perspective, I think the added rebuild cost of the 2.7 may be recouped IF I ever sold the car.

I realize that the 2.7 is the "harder way" vs the 3.0 with similar power. However the 2.7s I've driven seem to "rev better" and better throttle response than the 3.0s.

I realize this is like the blondes vs brunettes question.. but what you do?
Old 02-10-2018, 06:35 AM
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I scrapped my 2.7 from my '77 and installed a 3.2 built from an '80 3.0 over 20 years ago. It was built by famed local racer/builder Rudi Bartling and was from a car that had been stolen but subsequently recovered. I has lots of torque and is fun to drive. Supposedly it has about 220-230 hp but I've never had it dynoed. It was twin plugged but I've always just used it with a single plug distributor. If I ever want to spend the $3000 or so I could convert to the twin plug distributor which would allow me to use regular gas, but wouldn't change the output. This engine is an old school mod that was done back in the '80s and still uses CIS. Along w/ a Dansk/SSI combination, it sounds great and pulls very strongly even after 100,000 mi.

As I said, it's old school. Today there are other, maybe even better ways to do this, but I still like it!
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Last edited by Paulporsche; 02-11-2018 at 08:03 AM..
Old 02-10-2018, 07:06 AM
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gshiwota,

After all the changes you are talking about, you will not have an original car - so don’t try and save something just because it was stock. If you’re backdating the body, you no longer have a stock car, and there is no benefit to keeping the original engine.

You can always store the 2.7 as the original engine for resale and build the 3.0 as you want. It also sounds like whichever engine you build will not be stock either. Once the car is not stock…….it’s not stock anymore.
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Old 02-10-2018, 07:06 AM
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Quote:
Originally Posted by Walter_Middie View Post
gshiwota,

After all the changes you are talking about, you will not have an original car - so don’t try and save something just because it was stock. If you’re backdating the body, you no longer have a stock car, and there is no benefit to keeping the original engine.

You can always store the 2.7 as the original engine for resale and build the 3.0 as you want. It also sounds like whichever engine you build will not be stock either. Once the car is not stock…….it’s not stock anymore.
What he said. Matching numbers is the cherry on the top of an original car. A modified car with the same engine case as the original doesn’t really add any value. Buying a modified car is done because you like the mods, not because you think it can be converted back into a concours survivor car.

There is no replacement for displacement.

Shelve the 2.7 If you can and you’ll see at sale time if anyone is interested in paying extra for it to get the original case.
Old 02-10-2018, 07:44 AM
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I went thru this myself maybe 6-7 years ago. I replaced the 2.4 with a 2.7 in my 72 and ran it for years. I wanted performance and was looking for 10:1 power/weight. I went thru a weight reduction program ( much cheaper than adding HP). The car now weighs 2200 lbs. I was told that to build a 2.7 to over 220 hp would require some case work as well as the other upgrades $$$$$

My research showed that the only problems with the 3.0 was the case studs. I purchased a 3.0 out of a wreck. I bought Waynes book and decided to do it myself. With the help and advise of Mike Bruns at J&B racing I began my rebuild. You know when you are there you find some little additions that make sense since you have the engine open, so I made some reliablity and performance upgrades. A special cam with lower torque peak but still makes HP (214 ft/lbs @ 4400 and 250 HP @ 6900 rpm tuned on a engine dyno after two days). I only used J&E 9.5 pistons but cut the heads for twin plugs. I still have Webers but had them opened up from 40mm to 42mm.

This engine has been bullet proof, which was my objective. It has 20,000 + miles so far and I just run the s**t out of it and adjust the valve and change the oil once a year. What more can you ask. Oh, my car has 241,000 miles on her.
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Old 02-10-2018, 08:15 AM
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Go 3.0-3.6 if you’re going to slash the value and cut the car up.

Maybe sell the car in original form and buy an already backdated car. Addressing the leaks and new P&Cs might be all it needs. Not all of these have pulled studs/need case halves re-worked though it is a wise thing to do. 2.7 being mag is lighter.
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Old 02-10-2018, 08:37 AM
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My background: I've got a '75 Targa that I acquired with a "frankenmotor" - 2.4 bottom end but 2.7 heads & CIS. I rebuilt this into a stock 2.7 CIS motor. The car is not a bare-paint resto by any means - more of a rolling "lightweight" project. Engine runs very well, revs freely (and likes it) and is a hoot to drive.

If I had to do it over (and was counseled by others to do so from the beginning but didn't listen), I would go with a 3.0 (or bigger) and build it the way you're suggesting with more modern engine control. The slight edge on lower-end torque provided by a 3.0 is a valuable asset for daily-driving on the street. I'd also look at taller 5th gear for highway cruising.

Porsche did have a few improvements between the 2.7 and the 3.0 and those are worth it. Thermal control isn't as much an issue (but doesn't go away either). EFI and EDIS properly done on a 3.0 will make that bulletproof and fun to drive.

Last but not least - if you ever have to sell the car - the "stigma" of an installed 2.7 (no matter how well done) may actually bring lower prices (even if original) than a well-built 3.0.

Best of luck.

Last edited by fanaudical; 02-10-2018 at 12:35 PM..
Old 02-10-2018, 12:30 PM
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Quote:
Originally Posted by gshiwota View Post
I might get away with just a top end on the 3.0 but I would want to split the bottom end to check condition since it doesn't appear to have been split.
You can pull a rod bearing or two without splitting the case. If the rod bearings are ok you know the mains are.

Buy new rod bolts for the ones you pull out.
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Old 02-10-2018, 04:13 PM
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The 2.7, built right, is an awesome engine and one of my faves to build into a hot rod motor. I'd stick with it.

regards,
al
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Old 02-10-2018, 09:27 PM
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I know two local guys who are running EFI/ITB on a rebuild 2.7 with CR of 10.1:1 (JE pistons) with DC20 cams, single plug. These engines are very strong and extremely fast revving - perfect for a narrow body hot rod in my opinion.
Old 02-10-2018, 11:42 PM
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It's a no brainer to go with the 3,0.

If you are at all worried about resale at some point, put the 2,7 in a crate and save it.
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Old 02-11-2018, 01:16 AM
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Agree 100%. Pressure wash/steam clean the 2.7, spray every nut/bolt with Kroil Aero, and crate it, rebuild the 3.0 from the bottom up...
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Old 02-11-2018, 02:24 AM
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I had a good 3.2 and the stock 2.7 in my car when I was racing it. I went through a similar conundrum. I did a top end build on my 2.7. The formula was 9.5:1 JE pistons shimmed to 9.8:1, DC40 (Mod S) cams, early exhaust, recurved distributor to RS spec (easier and cheaper to do with Edis and I can give you the table from a subsequent build), ported heads to 36mm like a 2.7RS, Weber Carbs with 34mm chokes (I also have 36mm), PMO manifolds. This dynoed at 215 at the wheels and would do better with the 36mm chokes. Also I have the 7300 rpm rev limiter.

I expect you could sell that 3.0 to cover your costs.
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Last edited by unclebilly; 02-11-2018 at 03:52 AM..
Old 02-11-2018, 03:49 AM
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2.7 or go 2.8 even, all day. My shop is about 2 miles from Road Atlanta so we have a wide variety of every manner of modified 911 engine coming through here. The 2.7-2.8 engines rev better, sound better, and just plain drive better imo. I’ve driven umpteen zillion of both. The juice is worth the squeeze. 3.0 is a quick and easy way to go but they don’t check all the right boxes unless you dump a fortune into building one with very light internal components so they feel and sound lighter. Good luck and keep us posted!
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Old 02-11-2018, 05:47 AM
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Quote:
Originally Posted by fanaudical View Post
Last but not least - if you ever have to sell the car - the "stigma" of an installed 2.7 (no matter how well done) may actually bring lower prices (even if original) than a well-built 3.0.

Best of luck.
This is changing and part of the reason is so many people have replaced middie engines with SC engines in the last 30 years. Numbers matching 74-75 in particular are being recognized in their own right.

Gshiwota,

I am right in the middle of this same exercise. I've got this 74 here with an 85 engine in it. However, it's on the original CIS and the seller of the car said it was a 3.0. It's a mystery really, but the red fan might be an indication of it's roots.

Project one has been acquiring everything to build a 2.5SS on a 7R case. I'm far enough along that I'm starting to ship off stuff for machine work. I'm hoping to have t assembled and in the car by end of summer. I'm back and forth on Webers versus MFI. I have gotten both and will likely install both at some point.

Then I've got a new core to play with. Assuming it's built as a 3.0 I will keep the crank and rebuild it as a 3.2ss and maybe EFI it. My 75 has a 2.2e engine in it, so I need something else for it long term.

I'll let you know the results of myjourney in 2-3 years?
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Old 02-11-2018, 05:54 AM
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Thanks for the feedback so far, this is a really good debate.

I'd love to hear more from those with experience owing a 2.7. I've daily driven several 3.0 and 3.2 cars so I'm pretty sure I know what to expect with the bigger motor. In my brief seat time with my current 2.7, it felt sharper and lighter.

Anyone with EFI on their 3.0 want to chime in? I imagine EFI improves the throttle response and wakes up the motor.
Old 02-11-2018, 06:08 AM
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I always preferred the mag 2.7, especially the 7R case with S cams, pistons, and a real exhaust. Webers on that package were a lot of fun, but it sure sucked down the fuel.
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Old 02-11-2018, 06:46 AM
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My 75 911s all original but heat exchangers deleted have been making 3.0L and 3.2L work very hard in order to see my tailpipe.
Old 02-11-2018, 07:43 AM
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I haven't done this but I've driven both enginges and my advice would simply be - don't backdate car if you gonna stick with 2.7 - actually don't back date at all!!
Build that hot rod 2.7 numbers matching in the original body work - maybe do glass bumpers to get weight off but middies have a real specific non-flared impact unique beauty!!!!!!
That said, if u neeeeeeed to backdate then go 3.2SS all day long
Old 02-11-2018, 07:59 AM
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I've been running an MFI 2.7 for years, its a great motor, but if I were going to use EFI, I'd go for the 3.0.
I have a friend who built a high compression 3.0 running K-Jetronic and it was fabulous. He is a very experienced engine builder so I'm sure there was some trick stuff.
If I had a 75, I would not backdate, make an IROC 3.0. Cheaper and a great driver.
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Old 02-11-2018, 11:30 AM
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