Ultimate 2.7 build (long)

[dtw]

Skip the first two paragraphs if you don't care about the sad history of this car

As some of you know, last year I picked up a '76 Targa basket case. It has had a hard life. Only 86k on the clock with an immaculate unibody, and is actually the nicest 911 I've ever worked on - no frozen/rusty fasteners, etc. The story goes that the car was seized by the DEA in the 80s (it was last registered in 1986), languished in a federal warehouse for years, and was finally auctioned off to a gentleman who set about reviving it. He headed overseas and had to abandon the project, and it ended up with me. As I started going over it, I found evidence of fire damage in the engine bay. What a sad life! This car only ever got 10 years of proper use before 20 more of neglect.

When I got it, Tim Walsh and another 911 nut friend of mine spliced in a new rear wiring harness and put the car right. The engine came with a documented rebuild and zero miles. Longblock and ancillaries arrived in boxes. Despite having invoices from a 'pro shop', a little exploratory surgery revealed massive *****ups. The brown chain ramp was in the wrong position. Half the ramps were not seated/aligned properly. A quick check of the cam timing revealed it was timed to SC specs...a further measure revealed the cams were stock 2.7CIS cams. I fixed all this and more in the top end, checked the leakdown (great), threw the engine in the car, and drove it all summer. The car really seemed happy to be alive again, and treated me well. The transmission was graunching from 1-2 on anything over a 3krpm shift though, and there were issues with the engine. It was overheating badly even in cool weather and low load. It was leaking from...everywhere. The intermediate shaft 'death' stud was pulled, as was one of the transmission mounting studs. The weather was cooling off so I yanked the engine and tore into it. More horrors in the build came fast and furious. The cam tower fasteners were only finger tight toward the rear of the engine, meaning the builder left 'em loose so the cams would turn (heads and case deck were both way away from being flat). Two mild steel washers on two of the head studs...also loose. One piston dropped on the floor with a huge chunk out of the skirt; big scuff action in the cylinder. Rings and lands completely worn out. Chain sprockets (inner and outer) worn to the point that the tensioners were maxed out on travel. Thick layer of goo on the heads and case halves - wayyyy too much sealant. Valves, guides, and springs all out of spec.

Since I had already become upside down in the car beyond my goal of flipping it, I decided to treat the engine to a really nice build instead of parting the car out. Even in its weakened state, it was plenty fast and very well matched to the chassis/suspension. As such, no performance enhancements have been made. However, I am trying to make sure all modifications/upgrades for heat management and longevity are getting made. I've already done quite a bit, and want to get the Pelicaners involved to make sure I haven't missed anything. So far, I've done or am doing the following, ranging from cheap/easy to spendy/complex:

-Updated cylinder cooling tin
-Installed factory oil cooler setup: hardlines/thermostat/trombone. Will likely upgrade trombone to a 44-row Mocal radiator with thermostatic fan prior to reinstalling engine
-Turbo cam tower line fittings (controversial but I like 'em)
-11 blade fan (yeah, this was actually running a five-blader)
-larger crank pulley
-brand-new Mahle piston set and re-plated Nikasil pistons (scored and got this setup cheap from EBS...right place/time)
-tossed out air injection and other BS, installed early HEs
-4-rib oil pump
-DFL on mains/rods, piston skirts, rocker shafts, cams
-CERMET on crowns, combustion chambers
-inserts on headstuds and all other major studs

The only thing that hasn't been done yet is the coatings and the rod machine work, so I'll be ready to build in a few weeks. Your suggestions are welcome! I hope to make this the best possible "stock" rebuild on a 2.7 that can be done.

[Fidalgo911S]

Great read. Sounds like you've done your homework, should be a great engine. I'm on the last few hours of assembly on my '74 911S 2.7. I went mostly stock with the exception of SC cams. I had the motor checked/balanced (crankshaft, flywheel, pressure plate, starter ring, pistons, rods, wrist pins). I also took the heat exchangers and had them Jet-coated. They were rusty on the surface and instead of shelling out $1K on SSI's, I took this route. I bought SSI's before and they were super nice but I wanted something different this time. Also added a M&K Muffler.

Good luck. I'm sure it's going to be a great motor you've built.

[dtw]

Thank you for your comments, Nate. What is great about building these engines is that every time you do it, you learn a lot more. You can start developing your own informed opinions about some of the more 'debated' aspects of 911 engine building. I'm really excited about this build.

I'm surprised there isn't more action on this thread! That must mean my build plan is fine as-is .

One thing that you brought up is SC cams - something another Pelicaner brought up via PM on another discussion right around the same time. I just happen to have an '83 SC motor that I am dismantling right now, so I've got 4-bearing towers and SC cams ready to go. Jamie Novak ran a model of the 2.7S cam versus the SC cam in a 2.7 engine and I was a bit surprised at the results. The stock cam is showing more HP and torque along most of the graph, but with the SC cam peaking higher and later than the 2.7 cam. Assuming the graph is correct, I think I'll stay with the 2.7S cam:

[Fidalgo911S]

Interesting graph. It seems the 2.7S cams have the edge. We'll see how I like the SC cams. If I feel they're less than what I'm used to, I can always go back. But I think just doing the rebuild will bring this motor back to life.

[Ray_G]

Dave,
Were the engine comaprisions above done with otherwise stock engines? Just the cams being different?
As you know I am doing something very similar. I am wondering what you are going to do about your tensioners? I am up in the air about going to the oil fed ones or collars on the new style turbo tensioners.
Ray

[dtw]

Ray - I'll let Jamie weigh in here also, but I believe the engine comparisons above were plotted on an otherwise stock 2.7S engine.

Tensioners - I've got pressure-fed units on this engine and on my 2.4 hotrod engine. If you decide you want turbo tensioners w/collars, I've may have a nice set available for sale, not sure till Friday, though.

[eapcpa]

Dave,

Good thread. I will watch closely and maybe lend a hand after my busy season. I am a fan of pressure fed tensioners with the internal stop modifications. Just a little insurance. Still need to call about parts but I have been very busy.

[Grady Clay]

Dave,

I don’t see any mention about repairing the crankcase (align bore, cylinder spigot surfaces, etc.)

It seems you have done your homework on case studs. Did that include the M8 stud at the jackshaft bearing and the two big M10 (fine) main studs behind the engine oil cooler? I understand many are installing inserts for all the case studs, including the M8 and M6.

Your ’76 should have the ‘oil bypass mod’ from the Factory (that is the first year). Check that it has the appropriate oil pressure relief.

The ’76 was also the first year for the 4-rib oil pump (911.107.008.01). I’m surprised you didn’t have it already. Again, an important reason to check the pressure relief parts.

While you have things apart, lets go measure the actual length of the gears in your 3-rib and 4-rin oil pumps. That is something missing from Wayne’s engine book.

There has been some discussion about the thrust surface (facing the flywheel seal) of the #1 main bearing. It seems that some of the current versions have less thrust oiling or something. I like to enlarge and chamfer the two oil drain holes between that bearing and the flywheel seal.

You hopefully have read my analysis and opinion on the cam oiling restrictor fittings. I think I can argue you out of them. Related is the oil pressure warning switch. Porsche changed the switch threshold from 0.3-0.5 bar to something much lower – I don’t remember the number but I posted it somewhere. They also changed the switch color.

Your ’76 probably has 4-bearing cam housings (47 mm) with 3-bearing cams (47 mm). I recommend you carefully inspect them to see why the previous ‘repair’ appears to have the cams binding before you make the decision about the 4-bearing (49 mm) 911SC cams and housings. Another thing to check is exactly what cams you have. You should have the 911.105.143.00 L (.144.00 R) with intake lift (including base radius) of 38.43 mm and not the .141.00 L (.142.00 R) with 37.90 mm. I think the ’76-’77 Carrera 3.0 (CIS) cams (47 mm) can be fitted with some benefit.

I would like to know the configuration of the 911S-to-911SC cam graph. What engine, P&Cs, induction and exhaust?

I assume you are going to re-do or inspect the valve job. There is discussion about the choice of valve stem seals. If they seal too well, the valve guides don’t get enough lubrication.

I like the mag chain housings but you should inspect for the large tensioner support pin being loose in the casting. This should have the ‘Turbo’ tensioners and the 2-bearing idler arms.



It looks like you are well on your way to a nice and long lived 2.7 ’76 Targa … If only Porsche had built them this way in the first place.

Best,
Grady

[dtw]

Grady - thank you for weighing in. Very glad to have your expertise on this subject. Note that in my original post, I only referenced things being done to the engine relative to heat management and longevity - I'll address some of the other items being done as I respond to your post.

Crankcase - Yes, did the layshaft stud and several others, including all the transmission mounting studs, during the case work. The two M10s behind the cooler have been left alone under the advice of Mike Bruns (he did the case work). I believe he said he's never seen those stud bores fail. The case was already bored first oversize and is straight and in-spec. The case is a factory bypass case. Found correct pistons and weird springs in the case, am replacing all with new. Also faced the spigots.

4-rib pump was actually inside the engine now that I think of it. And, it has been measured and found to be in great shape.

I'd be interested in hearing your specifications (and seeing some pics) for your mods of the #1 thrust bearing. I have Glyco bearings of unknown manufacture date. Can you elaborate on what your oiling mods accomplish?

Actually I vaguely remember that you were not a fan of the Turbo cam tower fittings. Do you have any links to your thoughts on that issue? My understanding is that they primarily only benefit oil pressure at idle/low rpm.

IIRC, I have 3-bearing towers and cams. The towers are flat. The heads and case deck were not flat, however. They have both been machined flat and unfortunately I will be using additional shim stock to space the top end back out. I'm actually netting an approximate quarter-point bump in compression, too. Also, I do have the cams you indicate - I already checked the numbers and measurements against my shop manual.

Grady, what are your opinions on the 2.7S cam versus the SC cam? As far as I know (paging Jamie Novak), the cam graph assumed a stock 2.7 CIS engine w/8.5:1 CR and stock exhaust. The peak HP of the graph with stock cams appears to match the factory spec.

The valve job has been completely redone. This was the most exhaustive (and unfortunately most expensive) head work I've ever had done. All new guides, valves, springs, stem seals, etc.

First I spent an evening exhaustively restoring my magnesium chain housings. Inserts on all the bores, re-epoxied the studs, dressed the mating surfaces, yada yada. Then I picked up a set of aluminum housings . For that matter I am also going with aluminum upper/turbo lower valve covers. Am using pressure-fed tensioners and the updated/wide-bearing idlers, also.

Trying to think if there is anything else I forgot...I think that is it. Do you have any experience with the ceramic and/or dry-film lube coatings?

[jpnovak]

I didn't think that one graph would generate so many questions. The curves that Dave posted were generated using Desktop Dyno. I have used it quite a bit to see how different cam profiles compare on a given engine. The parameters were a 2.7 displacement (90mm x 70.4), 8.5:1 CR, tuned exhaust (read headers), 46/40mm intake/exhaust valves and a head flow of 375 cu.ft./min. If anyone has measured flow data from a stock 2.7 head I would be happy to upgrade the graph.

The program has many limitations but can be useful depending on what you are looking for.

In my experience these graphs are useful for two things: Position of peak HP/TQ and comparison of lift, duration and overlap within a given cam spec. The absolute numbers are not always correct compared to factory specs or even real world dyno numbers. I do see that the position of the peak values is very accurate.

The two curves in the graph have the exact same internal engine specs with the exception of the cam profile. There are major differences in the lift ,duration and lobe center of a 2.7S and 3.0SC CIS cam. Most of the increase in torque, especially at low rpm can be assigned to the wider lobe center (less overlap) and to some degree the short lift of the exhaust lobe. This just means the valves stay closed longer and there is a greater benefit during the burn. YOu really see this effect as the rpms increase and the engine just chokes itself off. At this point there TQ curve drops off very rapidly.

[Ray_G]

Dave,
You might shoot me a PM if you have those tensioners for sale on Friday. I am also all ears as to any cams or grinds that anyone knows of that might benefit me. My engine is going back with stock pistons. I will back date the exhaust and remove the air injection system. My engine came apart because it had an oil squirter plug up on one cam lobe and wiped the lobe out. So, I need to do something with my camshafts. Not trying to crap on Dave's thread, but we are doing almost the same things.
Ray

[dweymer]

What, all this work stuff and no pretty pretty? Where's all the questions about what color oil your going to run? hehe Sorry I will be out of town on the rebuild Dave, but don't fret you can help me do mine later

What are you going to do about CIS fuel lines? I have the plastic ones, and they scare me, just getting old and brittle.

Get your flywheel resurfaced yet, what about a new clutch disk?(I don't know if you did this with the trans or not)

Please outline the sealants your going to use as well.

[dtw]

Hey Donnie, darn, sorry to hear you won't be able to make it.

Heh, my 2.4 hotrod engine can be the pretty one. This one is not getting a lot in the way of cosmetic work. CIS fuel lines - been thinking about that. I have plastic lines in good shape, but a perfectly good '83 CIS system with metal lines sitting in the corner of my garage. Those metal lines are definitely calling to me.

I have a resurfaced flywheel and brand new clutch pack - I did that when I assembled the car from boxes last year.

Sealants - going to try out the Henry Schmidt glue trifecta method. Going with the two Threebond sealants he uses, plus Loctite 574 and also Curil T.

[dweymer]

dizzy rebuild? Injectors sent to witchy? CIS seals? recondition rockers

[dtw]

Distributor appears to be fine. No idea who witchy is but I bench-tested these injectors. All CIS seals were replaced last year. Rockers and cams are fine, rockers are bagged according to original position.

[Grady Clay]

Dave,

Re: the M10 nuts behind the cooler, I think the issues I have seen (and heard about) are from the nuts being over tightened at some point. This was probably a mis-guided attempt to stop a leak from farther above. The problem is you can’t tell if the threads are close to failing. It is sorta like the cylinder head studs. You insert all of them.

I got a disassembled ‘73.5 engine just so I could answer some of these questions. It seems I only got the #8 bearing. I think John Cramer discussed the #1 bearing issue for his 901/05 project.

Did you find the thread discussing the cam oil flow restrictor issues? IMHO, it was a ‘fix’ (at the expense of cam & rocker life) that Porsche came up with to reduce customer complaints about low oil pressure at idle. Don’t use the restrictors and keep the rpm above 3000.

I’ll bet that you have 4-bearing (47 mm) housings and 3-bearing cams. Look carefully. Porsche didn’t drill the oil passage for the 4th bearing in these housings. If really 3-bearing, what are the last four digits of the engine number?

I don’t have any worthwhile opinion comparing 2.7S vs. SC cams – they are both CIS.

The proper valve job is the best performance gain and longevity you can get. While Porsche built great 911 engines, the valve work could always be done better. Valve guide technology has improved and with care you can improve on the valve-to-guide clearance and linearity. The latest valve stem seal ‘improvement’ is for emissions and is counterproductive in our ‘old’ engines.

I’ll trade you something if I can for the mag chain housings and covers. I like them, they are light. With a Turbo tensioner and the 2-bush idler arm, the only failure is the pin press-fit. I’m going to invent some retaining device to prevent the pin from moving to a cantilever position. I can handle fixing an oil leak.

What condition are your mag valve covers?

I need to pick your brain about coatings.

Best,
Grady



Ray,

Where did the debris that plugged the cam oiler come from? Inside the oil tank? Other? You sure don’t want a repeat performance.

Best,
Grady

[Ray_G]

Grady,
I don't know where the debris came from, but I sent the case and crank and cam towers and heads went to Ollies and they were told about it being plugged up. They pulled all the plugs and cleaned everything. I have not done anything about the oil tank or oil cooler. I don't know if it is OK to just clean them out or not. I imagine the tank is ok to clean, but I don't know about the cooler. I do have an ultrasonic cleaner so I can run them through that. I just have not got that far yet. But everything that I touch is getting disassembled and cleanded, I don't want a repeat. Based on the lack of maintence this car got there is no telling how long they went between oil changes.

[dtw]

After all the packages I send out from sales on the classifieds to people, and all the compliments I get on my packaging jobs, I screw up on my own parts. Didn't pack my cams adequately for shipping out for DFL coating. Ended up that one broke in half. Already got a good used pair sent out for coating, but the bad news was that my rockers would have to be reconditioned.

It can cause accelerated wear to mate used rockers with different cams than they were originally mated with. Whenever re-using rockers and cams, make sure to bag the rockers according to original position (Cyl 1 Intake, Cyl 1 Exhaust, Cyl 2 Intake, and so forth). If getting a new cam grind, don't skimp on the rocker reconditioning.

Anyway, Pelican's own Craig Garret (cgarr) refinished my rockers in lightening-fast time, and has also set me up as a guinea-pig with the PermaGlide bushings he's been experimenting with. Read more about these bushings here:

http://gruppeb.org/forum/viewtopic.php?t=4629&postdays=0&postorder=asc

Thanks to Craig for helping make this build 'more ultimate'.

Grady - a true pleasure talking to you a week or two ago. Thank you for all the info. Drop me a line, I can send you some magnesium chain cases and upper valve covers.

[dtw]

SO, it is finally time for an update on the 'Ultimate 2.7 build'. This may be a long post, like the first one! After all the prep work and planning, I set a date for an 'engine build clinic'. Several of my local Porsche friends were invited to join in the build. Some had never done a build before, and some had done one or two complete builds before, so we had a really good mix of experience. I wanted to show the total newbies some of the basics of 911 engine building, and also hoped the more experienced folks would learn from some of the more interesting/advanced concepts being applied to this build. Well, I worked my ass off for an entire week getting prepped for the clinic. Made a big pot of chili and charged 'an interesting beer' as the price of admission to the clinic, and finally got to sleep at about 3am the night before the build. Special thanks due here to Tim Walsh, who drove in from Winston Salem on Friday evening, with his lovely wife Stef, to help me out.

Well after all that planning, the whole deal went to hell.

Simply stated, when we sealed up the shortblock, the crank would not turn. I immediately (and mistakenly) assumed that the crank was bent. Reason: I picked up a used crank from another local friend and Pelican. My original crank was well within spec, but his measured out significantly nicer. When I called the shop that measured it out, they did admit they didn't check runout "because you didn't ask us to check it". Grrrr, ok, my fault. I had my old crank and tore the shortblock apart and reassembled...oh shix, it still doesn't turn. After a week of diddling around, it was determined that the case was simply hosed. Due to all the overheating problems, uneven deck, and wayyyyy overzealous sealant job, all we could figure is that the case massively relieved when I originally disassembled it. Well, I had to hunt down another case and send it out to get worked up, so this set me WAY back - again - on my timeline. Budget? Ha.

I'm pleased to report that I just got back in from a full evening of pounding on the freshly assembled motor. After all the setbacks, I finally got it back together and running. Brad Penn break-in oil for startup and first 20-30 miles, then switched to BP 20W50. Startup oil was remarkably free of debris - very, very clean. Rings appear to have seated very nicely. I drove the car extremely hard after rocker/cam break-in, and this appears to have done the trick for ring seating. Craig's super-secret rocker shafts are running quietly so far. I did use Henry Schmidt's glue-rainbow method. Seems to have worked great so far! All that's left now is to dial in the CIS - right now I've got a 2krpm idle and poor running below 3krpm and no load. Under load and/or over 3krpm, this engine is a freight train. Fantastic transformation from the tired engine I had 8 months ago (which actually ran pretty darn good, for a worn-out POS with terminal blow-by). The compression has been significantly improved by having reconditioned Mahle Nikasil cylinders with brand new Mahle pistons/rings. Also, there is about a 0.5 point compression bump from decking the heads and case - I did not shim all the way back up to 'stock' - I figured 0.5 points was a nice bump without getting too crazy. Also advanced the cams to about .75mm @ TDC, a bit beyond the book specs. This, plus the very-low-friction camtrain, adds up to a really great motor.

Perhaps most notably, after quite a bit of beating today, in 95 degree heat, my temperature never exceeded 205 degF. With the same conditions pre-teardown, I would have been wayyyy over 250 degF, probably 280+ before I would have had to shut it down. The fresh engine is surely a big part of this, but I'm sure installing the biggest Setrab cooler I could stuff under my front fender didn't hurt either .

Special thanks are due to Ray - "Ray_G" above. He's been building a 2.7 virtually right next to me, except he's in Oklahoma. Similar issues (though his also featured an amazingly damaged cam) and timeline, he and I have finished our engines after all our respective setbacks, at almost the exact same time. He beat me by a week getting on the road, but we both fired ours up within 24 hrs of each other. We've been trading build notes and moral support for months now, and he's been the #1 factor in me keeping my sanity through this build. I keep telling myself "never again" a mag-case 911 motor. They are very challenging - both on the budget, and on the mind.

Other big thanks are due to Craig Garret and Mike Bruns, who have lent their services and technical expertise. Mike, particularly, has spent a LOT of time on the phone with me going over crankcase issues as well as other aspects of the build. Thanks to them and everyone else who's had a hand in this build.

Thanks for listening (if you made it this far). I hope this thread will serve to help anyone building a 2.7 in the future.

[dweymer]

Congrats Dave!!

I know what it is like to have it all go to ***** during a project. And the satisfaction knowing you beat it.


D