Parts came up, need help to decide 2.7 build options
 

Hi guys,

First and foremost, I have limited engine building experience. I've torn down and rebuilt a v8 with help but never a Porsche engine. I apologize in advance as I only have basic knowledge of engine building, but I'm mechanically inclined and willing and excited to rebuild my 2.7. Having said that, I found a local seller with some juicy parts:

JE 90mm 10.5:1 Pistons, rings and nikasil Cylinders part 261664 (New)

DC racing 911 E cams (New) 3.0-3.3 mm

Rebuilt heads with standard bore from a 75.

It's difficult to price these items out so I'm wondering what you think ballpark you might be inclined to pay for all of these items. The heads are standard so I believe 32mm. Should I port them to 36mm?

A little about my rebuild goals. My car is a 1975 911s California engine 655xxxx type 911/44

I've removed the emissions stuff and am running SSI HEs. I've rebuilt the fuel system and cleaned up the motor but it's got 153k miles and I only put a front mount cooler on last year, so most of those 40 years have been without a front cooler. One through bolt is stripped in the back. It leaks at the case split and a bit at the heads in some places. all in all, it's quite worn and no matter how hard I try, I can't kill all the leaks.

I'll be running 91 gas with primarily street use and some possible future DE

I want to use my numbers matching 7R 2.7 case. I plan to ship to ollies to have it machined with the typical upgrades (oil bypass) etc

My rebuild budget is about 10k. I will do the tear down and assembly. A local shop will tune.

Intake will be webers for first phase with maybe some nicer pmo / efi option down the road.

I plan to keep the SSI. it's running to a hacked 2/2 bischoff muffler.

I like Bruce Anderson's recommendation for a street use 2.7 but he's using 95mm euro Carrera RS p/c, 911e cams, and webers.

What would you recommend?

I guess I would probably need race gas and twin spark for that high of a compression. Perhaps I should be looking for 9.5:1 Pistons

Yes, twin plug. Nice package for a racish motor though.

I would hold off on those pistons and cylinders, until you have totally disassembled your motor. Chances are you could re-use your cylinders and just buy some JE 9.5 pistons.

10.5 to one would require twin plugs. That is a nice option IF you have the budget for the ignition upgrade $$$.

My main concern, if I was you, would be the condition of the case. 2,7s are known to have problems with those mag cases and can require some expensive work to get back in spec.

What cams are those? DC 30s? That would be a good choice, depending on your other mods, especially the compression ratio you want to run.

Does your budget include the Webers? Do you have those already?

36mm for the intake ports is probably what you want.

If I was in your position, I would look at the possibility of boring your cylinders, if they need it, and building a 2,8 or 2,9.

Do you have Waynes book, "How to rebuild 911 Motors..?

Yes I have Wayne's book.He has a recommended 2.7 upgrade and that is the 2.7RS spec which has 90mm pistons and the S cam with 40mm webers. My budget did not include the intake.

I was shying away from boring the cylinders because I was under the impression that a 2,8 or 2,9 would be much more expensive to build for some reason. If it isn't, maybe I should look into increasing the displacement, wont that help with low end torque after all? Better for a street car.

I have Ollies price list, but not sure what the total cost will be to ship, and do the case. I'm ballparking 3k. is that realistic?

Wayne’s book should give you a lot of great information. I had Henry Schmidt at Supertec build my 2.7 with RS pistons/cylinders, S cams, running Weber’s and an Electromotive crank-fired ignition. It makes 199.5 hp at the rear wheels, so you should have a fun engine.

Just be sure that the case is properly prepared with Casesaver and sealed well.

My point is it depends. If you have Mahle nikasil cylinders that are in spec, it is a no brainer to go 2.7 with JE pistons.

However if your cylinders need to be bored, honed, or re-plated, I would go up to 2,8 or 2,9. No more money, since you have to have the cylinders redone anyway. You are already buying new pistons. IMO a 2,9 would be a dream motor, if done correctly.

Correct me if I'm wrong- stock 2.7 will have fire ring, do you believe it to be safe to go beyond 90mm? I was under the impression that to do this, he would be looking at alternative cyl regardless, then to simply re-nikasil.

I should be receiving my case back from Ollie's within the week. You are spot on with that price. Virtually $2900 shipped for all the goods. If I can remember, I will post pics of the work he performed on my 7R case.

I was VERY leary of using the mag case as you will read- there are seemingly infinite opinions recommending the later generation with alum case. I called Ollie's to quiz them a bit as I plan to track, spirit drive often and perhaps even roll it west to CO to visit fam etc. He assured me that provided the case is done correctly with Shuffle pins and case savers, oil mods etc (down the list as you have seen as well), that I would have to beat it to death before I need to stArt to worry. I spoke to Ron most often, guy is clearly knowledgeable and well worth an ear.

Good question on boring the cylinders. I don't know the answer to that. I do know a guy who is running a 2,9 based on a 7R case. He is a pro, and claims it to be a bullet proof setup. PM me and I can give you his contact. He runs a shop in NorCal.

@ImRevin7: What did you have done at Ollie's that cost $2900? I have a 2.7 that needs a rebuild and wondering if that was just for machine work to the mag cases.

Thanks

Look at my Garage. I covered off the 2.7 build I did for my track car there.

http://forums.pelicanparts.com/dto_garage.php?do=viewvehicle&vehicle_id=8702

I have a 2.7 with 9.5 JEs. I shimmed the cylinders / heads to get 9.8:1 compression.

I ported my heads to 36mm like a 2.7 RS.

At 9.8:1, you can run single plug. I ran 91 mixed with race gas at the track and straight 91 on the street.

I am running MSD, early HEs, and 34mm chokes in Webers with the PMO manifolds.

I have DC40 cams, you will want something like this as opposed to the E cams which are too peaky.

On the Dyno, this was within 5 HP of the engine in Magnus Walker's 277 car (2.6 short stroke with 10.5 and twin plug built by Andrew15). My torque curve was also a lot flatter.

If it you do go twin plug, do yourself a favour and use 2 EDIS distributorless ignition systems. You can do this all in for around $500. Either way, you will want to run an RS ignition curve.

Your trombone cooler will no longer provide enough cooling so you will need to add additional cooling.

Can you post your dyno results? I find it interesting that you say an E cam is peaky compared to a DC40.

I will dig them out. I was sandbagging (previous years gas and not tuned up yet) as the Dyno run for for power / weight classification.

Sorry for the delayed response. I would have to dig up my receipt for precision- but I will rattle off what I can think of at this moment.


removal of original studs and someones hacked time certs (gag)
some inserts for timing chain guide bolts (mine took some material when backed out)
Mains bored
cases shaved to fit original bore dimensions (crank bearings)
Case savers
spigots cut true
Trans mount inserts (they are known to pull)
Inserts # 1&7 mains
oil bypass
Truffle shuffle pins (I definitely did the dance when I saw the craftsmanship)
all case bolt and nut surfaces cleaned up
new case oil plugs
Hot tank and media tumble

I think there was some "hardware" charge in there somewhere too. Anyhow, the case seems very well done. Looks immaculate compared to how I sent it to him haha. Burned oil, discolored and lacking love..

DoooooWHAT!? As ^ said, yes please try to find your Dyno results. That is insane. Care to share complete breakdown? I am astonished that single dist, 2.7 made that beautiful of a tune basically off higher comp, Port job, mild cams and RS ign curve. Magnus was on MFI, and HUGE ports and gnarly cams comparatively, additionally- 3.2L... Please elaborate so that I can stop pounding MY head as well!!!???- "to go new cyl so I can punch out to 2.8 or to just leave 2.7" "Do I donate a kidney to get MFI and Twin plug or no" etc etc... And I quote-

"Naturally-aspirated 3.2 liter short stroke flat-six boxer engine built by Aaron at Rennwerks; J.E. pistons; single plug ports; 39 intake/38 exhaust; Hi lift Mod S cams; stock rods with ARP rod bolt;s AASCO racing valvesprings; Titanium retainers; stainless valves; 1-5/8″ headers; M&K twin pipe R muffler; mechanical fuel injection; stacks bored and port-match from 46mm at the opening tapering to 41mm; throttle bodies bored to 41mm; throttle plates port-matched; 69E injection pump re-calibrated for 3.2; isolated oil supply; solinoid delete; thermostat delete; red vent cap; Elephant Racing finned external oil cooler lines; Carrear front mounted oil cooler; long-filler neck fuel tank; Rennline battery kit w/ lightweight Optima battery..

I think that's two different cars. The 277 car has the short stroke 2.6 and the "STR" car has the 3.2.

I agree though, Uncle Billy your motor sounds solid. Did you do a build thread on it? I searched your post history and coudln't find anything specific.

So I was thinking I might do my build in a couple phases.

1. Upgrade ignition to MSD on current motor
2. Throw on some weber carbs - I see these on the classified: The problem is I know very little about carbs. Bruce Anderson recommends 40 IDA-3C webers with a 34mm ventuir, f3 emulsion tubes, 135 main jets and 145 air correction jets. so...say the above linked carbs don't have those specs. What's the cost and trouble of converting. And what is the 3c1 vs the 3C?
3. Full engine rebuild, put carbs and msd back on.
3. Upgrade to EFI with rassant and EFI TBs

I like the idea of Uncle Billy's with the 9.5 and 9.8:1. Wondering how long the motor has been going and the reliability of that motor.

Thank you all for the help.

I'm confused... You have carbs and you want to go to MFI? Or you have MFI?

If you go with E cams, you really don't need to shuffle pin the case. E cams will pretty much run out of breath short of stock red line. Shuffle pinning isn't needed for non-race builds.

I have neither. I am running the stock CIS at the moment. Ultimately I want ITBs with an efi setup. I thought Carbs might be a short term upgrade though that I could resell when I went to ITBs.

I was actually confusing mechanical fuel injection throttle bodies with carbs. I wasn't familiar with how the early MFI porsche systems worked. I thought they were actual carbs, but the name should have told me everything.

What is the price of Webers/PMOs today? 4.000$?

Have you seen the recent ITB thread (technical forum)? I've used the Bitzrace EFI kit on Clay's ITB setup. Al Kosmal also has some really nice kits including complete engine managment (ignition and EFI) as well for a very affordable price I think (4.000$). I gained 20HP on my EFI conversion alone - for 1800$.

Just an idea.