2.7 Rebuild – To bore or not to bore and other questions
 

Hi all, I’ve started to tear down a ’76 2.7 motor for a rebuild that’s going in my ’71T. This is my first engine rebuild.

My goal is to have a streetable hot rod motor with a target redline of about 7,200 RPM that can do some AX and track days here and there.
I’ve read the books and I’ve read the posts and now I need to pick a direction but I’m in need of some guidance...

Here’s my plan so far:

Reuse my cylinders and bore to 92mm
Pistons would be JE 9.5 to 1
Stock 2.7 cylinder heads
PMO 40mm carbs
DC40 camshafts
4 rib oil pump
Single plug
Casework by Ollies
1.5” European headers

Please chime in with any suggestions!

My biggest question right now is about the heads…will they need a chamfer with the 92mm pistons? Are the stock port sizes ok? Stock valve springs/retainers ok?

Here’s the beginning:

http://forums.pelicanparts.com/uploa...1609462771.jpg

The exhaust came off without breaking any bolts. And, I was surprised to find 930 tensioners in here. I guess I will keep these and forgo the pressure fed tensioner upgrade…


http://forums.pelicanparts.com/uploa...1609462798.jpg

Something not to overlook: Be sure to ask Ollies to check case twist and crank bore alignment. Many of these older 2.7 mag cases need to have mating faces shaved and then crank line bored back to round. Oversized bearings can sometimes be hard to find.

I just finished the same build on my 1971 911T with a 2.7 mag case. Only difference I went with 46mm PMOs due to my larger Intake port. I bought the 92mm J&E 9:5.1 pistons and cylinders from EBS Racing . Car pulls like a Banchee after 3500 all the way to 6000 for now while I break in. Only have 50 miles on motor now. Having a little stumble from 2800 to 3400. Went to Richards at PMO yesterday to talk about the transition circuit. He recommended a little change in jetting. That what I'll be doing today. Nice build though I love how motor revs quick and pulls hard with MoD S cams. I do run aluminum flywheel and aluminum Pressure plate. No problem with stalling. http://forums.pelicanparts.com/uploa...1609525027.jpg
http://forums.pelicanparts.com/uploa...1609525027.jpg
http://forums.pelicanparts.com/uploa...1609525027.jpg

Nice headers, who builds them?

Henry, these are Brian's at M&K RSR headers

This is on my list for sure...thanks for the advice!

Henry, I'm wanting to use your Supertec head studs for this build...any other suggestions?

I've been to your shop by the way...you and I chatted while your dog chased rabbits or goats or something.

Thanks for chiming in 911 SLANT...I love your build! I'm basically following your "recipe". If you don't mind me asking, did you chamfer the heads for the larger pistons? Thanks!

No, didn't have to. The J&E pistons cleared just fine.http://forums.pelicanparts.com/uploa...1609543012.jpg
http://forums.pelicanparts.com/uploa...1609543012.jpg

This is a fantastic combo. I’m figuring your ports are already 36mm?

I had the same combo and was a great engine.
However the bottom end did not hold up with your planned usage. The case was not dowel pinned. It’s replacement is (a 2.8) and has been a great runner. Maybe the first had some other issue undetected?

The experts can chime in on what the latest method is — I know there has been a bit of debate on whether or not and how to pin these cases now.

Alternatively you could build a short stroke which is a lot easier on these old cases.

I would also include a 4-bar oil pump and as much cooling as you can get.

Perfect, those pics are worth a thousand words...thanks!

Thanks for the advice!

Yes, the ports are 35mm (+/- 34.7mm measured). Interesting to hear your experience with the bottom end and dowel pins. I was going skip the dowel pins, but maybe it's a good $500 investment.

I did consider a short stroke, but decided the trade off in torque wasn't worth it.

An upgraded oil pump is definitely on the list.

The tear down continues...

Here's where I'm at now. The chain housings (left is mag and the right is aluminum) are worse for the wear and will need to be replaced.

http://forums.pelicanparts.com/uploa...1610164168.jpg

http://forums.pelicanparts.com/uploa...1610164573.jpg

This rocker shaft looks like it walked out pretty far...hard to tell from the pic, but it's sticking out about a quarter inch.

http://forums.pelicanparts.com/uploa...1610164226.jpg

Ward, you seem to have a really good grasp on your rebuild. I'd recommend calling William Knight though to pick his brain about your build. I'm working with William right now on a similar 2.7 build for my 911 at the moment. Super knowledgeable guy and extremely helpful.

http://forums.pelicanparts.com/porsche-911-technical-forum/129421-william-knight-superhero.html

Leave a message or send him an email.

Will be a screamer that will want to run past 7200 RPM redline. Anything you can do to lighten the valvetrain is recommenced.

Chris
73 911 E 2.4 with 9.8 CR and DC 30's

Fab engine! Make sure the intake and exhaust ports are opened!

Rather than considering shuffle pins for the case halves, you ought to think of bushings - tubes around the through bolts. Like what Porsche does for the #1 main bearing. There is a trick which allows you to drill these holes larger one by one with the case otherwise bolted together, so the tubes line up perfectly. Cgarr can do it for you, as can other machinists. Pretty straight forward. A good idea for a race motor, whether tracked or not, and especially for a mag case.

Myself and a friend just had our jugs sent out, he used millennium, I used US Chrome. Both sets (his a 3.0 and mine 3.2) had one bad cylinder returned with excessive pitting. I was able to source a set of jugs for free but it still cost me an additional $220 to get the 7th one bored and plated. Just a word of caution when considering new jugs vs boring existing.

The pitting being from exposing porosity in the cylinder casting or a bad plating operation?

Great advice, I will do that!

I appreciate the input!

I am concerned about this, too. I exchanged some emails with John at Dougherty Racing Cams (aka "camgrinder") about my build and intended use and he suggested that titanium valve springs and retainers would be good insurance for any revs over 7,000. So, these are now on my build list.

What port size do you suggest? They are at 35mm now and I'm concerned if I open them up too much more that this will become a full race motor and not streetable.

Thanks! I've seen this done, but wasn't sure if it had any advantages over dowel pins.

Good to know about this. Where was the pitting? Any pics? Thanks!

Current progress.

At this stage, I was introduced to “Murphy’s Law of Wrist Pin Circlips” when I removed the first piston. This law states that if you leave any openings in the engine case uncovered, a circlip is required to automatically fly in there when removed from the piston. Fortunately, I am now aware of this law and will comply with it during the reassembly process.

http://forums.pelicanparts.com/uploa...1610668798.jpg

http://forums.pelicanparts.com/uploa...1610668798.jpg

My friend built a engine very similar to what you are planning. It had good power everywhere. We used my 914-6 to break it in and get some miles on it. Mod S cams, Stock ports, Valve retainers and springs. Springs set at 34.5MM height. Rev-limiter was set at 7500RPM. Pulled very well and smooth to the rev limiter. His for sale post has some more details. Dynoed at 204 at wheels and probably could have got more with some tuning as we were a little lean on top. I am planning a similar engine but with more compression, twin plug and EFI ITB. I might even go up to DC44 cams.

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/1074394-911-engine-sale.html


john

Because you asked....here are is some shameless advertising.
Wide idler arms are a must. We modify stock arms for a reasonable price or you can by factory late style (wide) arms from our host.


http://forums.pelicanparts.com/uploa...1610818633.JPG
http://forums.pelicanparts.com/uploa...1610818633.JPG

Supertec case sealant kit, available from our host

http://forums.pelicanparts.com/uploa...1610818633.jpg

Twin plug distributors

http://forums.pelicanparts.com/uploa...1610818633.JPG
http://forums.pelicanparts.com/uploa...1610818633.JPG

Custom made engine harnesses

http://forums.pelicanparts.com/uploa...1610818633.jpg

We also make a pretty cool front pulley.
http://forums.pelicanparts.com/uploa...1610819288.JPG

Replacement fan pulley to renew a worn pulley and retrofit late pulley with our early replica. Rivets included.

http://forums.pelicanparts.com/uploa...1610819379.JPG

Draw, in the pictures, the pistons are upside down that you are removing or did you drop them in place for photo?
Bruce

Holy cow!!! I wasn’t even paying attention to that when I pulled the heads off. Those pistons are still attached to the rods in the pic. That’s how they were installed and it looks like it was able to run like that, too. (I bought the motor after it was already pulled from another car and I’ve never seen it run.)

I run 39mm intake ports, 38mm exhaust, and a DC65 cam. Twin plug. 92mm. It is perfectly streetable. 37-38mm intake ports certainly wouldn't hurt your motor.

Been chipping away at the teardown over the last couple of weeks and today I attacked the head studs. Wayne's book suggests using the Snap On collet tool, which I thought about but I couldn't find the Snap On CG500-43 collet on ebay and Pelican doesn't sell it any longer.

So, I went with propane heat and the pipe wrench and double nut method. Wayne's book suggests 10-15 minutes of heat, but I'm too impatient for that. I used a laser thermometer to check when the case got to about 230 degrees (which took about 3 minutes) and then I loosened the studs with the wrenches. I've got 12 studs out so far and no problems yet. I ran out of time and propane...

http://forums.pelicanparts.com/uploa...1612662258.jpg

Thanks for sharing, that's a nice looking motor...

Thanks Henry, I will definitely stop by for those wide idler arms.

Thanks for the advice. I'm considering opening up the heads to 36mm for both the intake and exhaust.

2.7
 

Great thread, following intensely and thanks everyone for the valuable input!

Maybe he has a camera that takes things upside down!

Nothing gets past our Bruce!!

Success!!! The case is split!

I removed all of the head studs without breaking any and without too much drama. I did have a brief magnesium fire that I was able to put out quickly. It's amazing how fast magnesium shavings catch fire.

I'm not so sure any case sealant was used during the previous rebuild. So, after I remembered to remove all of the case nuts in the various hidden locations, the case came apart pretty easily.

http://forums.pelicanparts.com/uploa...1613266458.jpg

http://forums.pelicanparts.com/uploa...1613266458.jpg

The crankshaft looks pretty good to the naked eye. I plan to take the crank to Marine for inspection, cross drilling, grooving, etc.

http://forums.pelicanparts.com/uploa...1613266458.jpg

Thanks!

That's funny! The other side had the pistons backwards, too. At least the previous engine builder was consistent.

It's amazing what experienced eyes can see!

Now watching this. It looks like I'll be building myself a hot street 2.7 over the next couple of years. It will be twinplug, I have 40 IDA's with MSD and a Patrick dizzy OR an aftermarket EFI with ignition to choose from.

It will be for a 914/6 conversion.

This is excellent. I am planning my first 2.7 engine rebuild myself. I'll probably keep it fairly stock but looking forward to your progress...

I wrapped up the teardown of the engine this weekend. By following Wayne’s book, and the wealth of knowledge here on Pelican, the process was fairly uneventful and fun.

The second to last project was to tackle the camshaft housing/heads. I used my lift table for my workbench…

http://forums.pelicanparts.com/uploa...1614573659.jpg

My Harbor Freight long 5mm hex bit didn’t fit through the rocker shaft opening, so I struggled with the 5mm “L key” until I remembered I had a Craftsman bit in my tool chest. This fit through the openings and made the job go twice as fast. I’ve seen some people cut down a longer bit to fit, and I’m glad I didn’t have to go there.

http://forums.pelicanparts.com/uploa...1614573659.jpg

Everything came apart without much drama. Unfortunately, the previous “mechanic” trashed some of the rocker shafts on the previous installation, which gouged the housings. So, I may be in the market for new housings…

The last project was to breakdown the rods from the crankshaft. I reattached the flywheel, stood the assembly on its end, and started removing rods from the top down. Things went great until I got to the last rod (cylinder #3). When I saw this, my heart sank…

http://forums.pelicanparts.com/uploa...1614574096.jpg

http://forums.pelicanparts.com/uploa...1614573659.jpg

The bearing has a groove that catches a fingernail. The rod journal itself looks good, so I’m not sure what to think about this yet. I guess I’m going to be stressed out until I get the crank inspected…

Now this is done, it’s time to spend $$$...yikes!

Thanks for watching! Sounds like a cool motor!

Thanks! Rebuilding an engine is certainly a worthwhile experience.

I saw you mentioned above about titanium valve springs and retainers. Some builders recommend against titanium in the valve train for a street engine. Titanium can wear, and is sensitive to failure once it does. In a race engine that is apart more frequently, it gets noticed before it is an issue. Most people will tell you the stock valve train, or some aftermarket steel springs, are easily good for 7000 RPM.

Well, a couple of years after taking the engine apart...

It's time to take the case out of the box from Ollie's.

http://forums.pelicanparts.com/uploa...1698626891.jpg

I apologize in advance if it's "bad form" to post how much the machine work cost, but here's the invoice.

http://forums.pelicanparts.com/uploa...1698627016.jpg

The case was pretty twisted, so it was line bored back to standard. The case lost 0.035 during the process. I'm going to need some thick gaskets for the chain housing. Any ideas where I can get those?

http://forums.pelicanparts.com/uploa...1698627449.jpg

Shuffle pins added.

http://forums.pelicanparts.com/uploa...1698627503.jpg

Right side of the case.

http://forums.pelicanparts.com/uploa...1698627657.jpg

One area I may have overlooked was not having the chain housing gasket surface fly cut.

http://forums.pelicanparts.com/uploa...1698627793.jpg

What do you think? Should I block the gasket surface flat with sandpaper or is it good as is? Also, the studs don't seem to be the correct length. Does anyone know the correct sizes? The PET lists some sizes that don't quite make sense to me.

There's some grease left around most of the case studs, so I'm going to remove all the studs and clean out the threads. On to cleaning!