Aaron

How do the pictures and dimensions of a 66mm six bolt crank distinguish it from a 70.4mm 6 bolt crank?

Walt

The flywheel end of the crank has aluminum plugs.

2.0/2.2 have 2 plugs

2.4/2.7 have 1 plug

However you cannot tell if the crank is counterweighted. Odds are it is not based on the engine being a T.

She turns over using a lever arm against the flywheel bolts! I soaked the rings in Marvel Mystery oil for an hour each side.
Now one side gets to soak for days.


I'll have to wait till this weekend to open up the sump and see idf I can determine counterweight or borescope of piston innards.

Going out of town for business (damn the day job).

More to come this weekend!

Richard

Thwarted!
 

So close! yet so far.
Is this screen original?

It sure does a great job of keeping the borescope from being able to bend around and see the underside of a piston :(

I did my best to angle the bore scope to get shots of the pistons themselves through the plug holes, but the bore scope head is too big to actually fit through the plug hole.

The pistons inside are rough surface texture, and you can see the machine work where someone did indeed fly cut the pistons for valve clearance. Can anyone identify the pistons?

I guess it's volume checking time. one cc at a time :)

http://forums.pelicanparts.com/uploa...1324069284.jpg
http://forums.pelicanparts.com/uploa...1324069293.jpg
http://forums.pelicanparts.com/uploa...1324069301.jpg

Richard

Bummer.

Early cases had that screen. I think it got supplanted by a much finer mesh screen which surrounded the area from which the pump sucked. Later pumps had a screen with what looks like the early screen's mesh size permanently attached to the pump suction intake.

Race motor builders using early cases typically discard the screen which is in your engine and use the later style of screen or screens that attach to the suction tube.

Or did you remove a screen with the sump plate and so on? That would make sense, since the screen dividing the engine into upper and lower areas wouldn't catch debris from the valve and rocker area - like an adjuster nut which came loose and got through the return tubes.

I'd say that this motor was not built with a later oil pump. Certainly not something really nice, like a 930 pump. Though in that case you would need a medical grade of small diameter laparoscope or the like to get around its permanent screen and upper plate.

Walt,
Yes I did remove the sump pickup fine screen with the sump plate. and though you are right, I cant get anything past the coarse upper / lower screen, I did creatively put a flashlight right down onto the coarse mesh screen, and was able to illuminate a piston skirt and could actually read some numbers!!

Though I can't read them very well.
One side of the piston skirt definitely reads Mahle the other side there is a 5 digit "number" though what I guessed it to read didn't come up in the pelican search or a google search. My best guess is that it says 82106.

OR if you read upside down, TaDa! Mahle piston number 90L58 !!!

which at least one pelican thread says are 2.7L 8.5:1 CR pistons 90mm diameter.

Which in turn, TaDa! says 2.5L SS motor!!!

http://forums.pelicanparts.com/911-engine-rebuilding-forum/406641-mahle-90l61-pistons-what-they.html

Though that CR won't be right with my ported and possibly modded 2.2 heads with these pistons. where's my pippet! gonna fill up a cylinder today and answer the displacement and CR once and for all!

Playing around today, I did a leakdown on the 69 engine that I believe is a 2.5L SS

Leakdown was about as you would expect for a newly rebuilt engine.
Cylinder % leakdown
1 5%
2 2%
3 4%
4 5%
5 2%
6 10% out the exhaust

I suspect that # 6 exhaust valve was open for 31 years and forms a patina of surface rust, and therefore didn't seal as well as the other ones.

I took a timing cover off to see if I could read any numbers off the cams. Nope, no numbers stamped on the end of the cams. Darn.

Tomorrow I'll check the CR if I'm lucky.

2.4 911S pistons

Corresponding evidence that my pistons are Nickie 90mm.

93mm pistons??
 

I measured everything three times, and I keep coming up with 93mm Diameter pistons, and 66mm stroke.

Here's the method I used:
Measures stroke with two "tools" measuring the distance change from TDC to BDC
Both of them measured 66mm repeatedly, even though the tool was down through the spark plug hole, and at an angle to the piston.
Tool 1 was a 1/4" diameter plastic dowel I marked it at TCD relative to the cam carrier, then marked it again at BDC. Measured 66mm with about 1mm error.

Then just for fun, I used a 1/32" diameter steel cable (Think bicycle brake cable) and held it up against the cam carrier while rotating to BDC. 66mm again.

Volume.
I mixed kerosene and Auto transmission fluid together and poured it in the cylinder at TCD to find the combustion chamber volume I got 70cc once I perfected the method.
I then measured at BDC, and repeatedly got 520cc of total volume.

520cc minus the 70cc gives 450cc cylinder swept volume.
450cc =Pi x R^2 x Stroke gives a radius of 46.5mm = 93mm diameter


Additionally the 520cc total volume divided by 70cc at TDC gives a whopping 7.5:1 CR

So recap. I think I have a 66mm stroke 93mm diameter 2.7L engine with a whopping 7.5:1 CR

Oh and the cams are S type cams...

Thoughts?

Spark plug takes up some volume. Did you account for that?

Yep, I took out the spark plug volume from all of the numbers.

Richard

here are the cam measurements, taken directly at the valve, and duration angles are crank shaft measurement angles

at 1mm lift:
Intake / Exhaust
256 deg / 243 deg Duration

.444" / .403" lift

at .050" lift
248 deg /237 deg duration

The closest I can come to making these match is early S type cams.

Anyone know of other cams that would have been available 30 years ago that might fit these numbers?

Well, the 66mm fits with what Aaron told us - from the end of the crank you can tell if it started life as a 66 or a 70.4mm crank. This is a 66, it seems unlikely that it would have been ground to get some other dimension, and that fits nicely with your measurements.

Despite the obstacles, did your borescope allow you to see part of the crank to determine if it was counterweighted or not? Hard to say if CW is good or bad - some like the non CW crank because of its smaller MOI for race motors.

The CR calculations and swept volume calculations do fall nicely into a possible cylinder diameter - 93mm.

There are flies in this ointment.

1) Although Mahle did (per Anderson) make a 93mm P&C, it was pretty rare I think. Used by SCCA GT2 racers with 914s (1mm overbore allowance for the allowed 2.8). SCCA did not allow twin plugging these race motors back when, and apparently this isn't twin plugged, so that does fit.

2) But the CR - who would build such a motor with such a low CR? 70ccs is the upper limit of what Anderson cites for 2.7 heads he had measured. But your measurement includes the effect of the piston dome, suggesting (assuming there is a dome) that the head volume is rather larger than this, which doesn't make a lot of sense. And 7.5 CR? Would not be a snappy motor.

3) Then there are those numbers cast inside the pistons, which seemed to indicate a 2.7 CIS piston?

Your bore scope through the plug hole ought to let you determine if the pistons are for CIS (which means they are 90mm max), or something fancier, like RS MFI or RSR pistons.

All of which casts some doubt on the displacement determination. I am hardly expert in the use of a burette for measuring, but I did have the ability to grease around the piston top circumference to try to keep leakage to a minimum. I used Marvel Mystery Oil (everyone should have this stuff in his garage, if only for the name) on the recommendation of a local shop. I got readings which I believed, then wondered how to get the stuff out without making a mess. I let it sit for some days. When I pulled the head off to swab it out, it was mostly gone! It had to have seeped by the rings (crappy old ones I installed just for this test) despite the grease, and spread out on the inner surfaces of the case rather than dripping out the open other side spigots. This was only enough for the cylinder filled heads, too.

Encouraged by what CGarr did, though lacking his machining skills and machines, I took an old spark plug and bashed its innards out. I then inserted a clear plastic tube from the junk box into the hole and epoxied it in place. When filling through a spark plug hole I could fill until the fluid rose up into the tube where I could see it. I then marked that spot, removed the apparatus, and measured what it took to fill just the tube to the line. Next time around I measured first so I could draw a line, and filled to the line. So not too hard to account for the spark plug hole one way or another.

Anderson says he has measured 2.7 heads at between 66 and 70cc, with the RSR head at 76cc. He notes that putting Euro Carrera 2.7 (RS) 90mm pistons on a 66mm crank would give a calculated 7:1 CR, though machining the heads could bring that up to 7.5:1.

Too bad that unnecessary stock screen is there, because maybe the difference in cylinder spigot wall thickness between 90mm cylinders and 93mms is something you can tell just by looking if you know what one or the other ought to look like.

Anyway, the effort of 93mm Ps and Cs with that low a CR doesn't make sense outside of a turbo.

That would make a helluva turbo engine!

Visually I can see that the Crank is Counterweighted. Though I can't get a photo of it through that coarse screen.

I suspect that the headvolume not matching the piston crown is what is giving such a crappy CR. That or I just can't measure volume.. multiple times in a row...

<misleading picture deleted>

I can't get the head of the bore scope through the plug hole. It's too big. The earlier borescope pics are the best I can get.

Yep it could be me. On the last two volume measurements I switched from Marvel Mystery Oil to nearly straight ATF to increase the viscosity and minimize the leakage past the rings. Then after getting it "full" as fast as I could, I just rotated the engine over and caught all the ATF in a clean catch pan. Re-measured what came out, and came up with the same 520cc minus 5cc still stuck to the inside and outside of the engine.

I have no good answers either. If it's as I measured, then it's a poor execution, and needs to come apart and P&Cs replaced, or heads replaced to get a better CR. Too bad as someone spent some serious time and money getting these parts to match.
Or the other answer. I did a crappy job measuring.

Last thought. Someone (not me) is going to have to disassemble the heads and P&Cs for two reasons:
1)The Sheetmetal air guide tin was not installed between the cylinders.
2) the beveled thru case washers were not used when the larger cylinders were put on, so I fear the cylinders are resting on the washers and not sealing against the copper gasket.

I have to punt. I could have convinced myself to keep the 71 If the engine was nearly bolt in ready. But the distraction level is too high. it's too easy to play guess the CR for hours instead of earning the daily bread.

I'm going to sand down the primer surface rust on the car, re-prime and sell the 71 and engine either together or separately. :(

AFAIK 2.2 and 2.7 combustion chambers are exactly the same, only difference is a chamfer on the 2.7 heads on the heads of squish area.
2.0 heads have deeper combustion chambers.

Maybe my spotty memory is wrong. can anyone else confirm the 2.2L heads and 2.7L heads have identical shaped and sized combustion areas?
if so then I'll delete my completely misleading picture above. and then go back to scratching my head..

2.2 thru early 2.7 have identical combustion chambers and valve sizes. late 2.7 heads have a deeper spark plug recess and a chamfer. I do not remember what year the 2.7 changed but around 1975.

2.0 liters are the ones with the deeper dome.