3.2 internals 3.o case

[juanbenae]

Has anyone put a standard 3.2 crank and rod set into a 3.0 SC case and used standard 3.2 barrels and pistons with the 78-79 CIS cylinder heads? I have some options in going this route on my early 3.oL build. do the heads need any machining to accommodate this?

I will be going with carbs, likely 46mm so I'm looking for cam selection info as well with this option. will the domes on the 3.2 pistons limit my cam choices to the point the additional displacement gain would be neutered? will employ a recurved distributer, will run pump gas exclusively

ive in the past built as early spec911 3.o that used euro pistons, SC cams, running CA pump gas with 46mm PMOs per class rules. this was a wonderfully live motor that I would not mind replicating with the added displacement opportunity with the 3.2 bits and some more carb dedicated cams.

am I on the right track here for a fun, smog exempt motor that may make as much 250HP as my spec motor did?

[Trackrash]

I don't believe you will have any problems with the 3,2 parts fitting with the 3,0 case and heads.

The weak point are the pistons. What cams will be compatible with the pistons and will they be worth while with carbs?

The stock pistons will also limit your upper RPM.

[juanbenae]

Originally Posted by Trackrash

I don't believe you will have any problems with the 3,2 parts fitting with the 3,0 case and heads.

The weak point are the pistons. What cams will be compatible with the pistons and will they be worth while with carbs?

The stock pistons will also limit your upper RPM.

per my research all will work, only need to confirm the head fitment. looking for something more definite than an "I believe" when it comes to this opportunity.

your second point simply re-asks my question regarding piston/cam options. or am I missing something there?

ive never required high RPM car to have fun driving a 911. other more accomplished spec racers that watched my race video over the years stated I drove pretty fast for being a short shift sally...

t

[juanbenae]

love the pelican knowledge base. I was reached out to being reminded i'd need a 3.2 dizzy or swap of the drive gear to maintain the current SC diz. keep the insight coming... please.

[Trackrash]

Others with more experience than me should chime in. However, I considered using a 3,2 crank and rod set in my 3,0 build, as a 3,2 set was available. However I had a perfect crank and rod set, so did not take the chance with an unknown set.

For me it is not worth using the stock 3,o or 3,2 pistons.

Your cam choices will be very limited. Either stock, 964, or Web 20/21. You may as well stay with the fuel injection with those cams. It is more fuel efficient than carbs, and runs just fine with mild cams. JMO. Now if you are building a spec motor, that may be a different story.

[juanbenae]

I must note, and I should have done so earlier to maintain context. this 3.oL has a motor meister past.... so it's likely to come way down. mileage unknown, the painted and impressed numbers in each side of the case after stripping to longblock seem to indicate it was split at some point. do not know the condition of the crank or rods yet as it will come apart this week. heads look fresh and appear to have new guides in place.

has a terrible oil leak at #2 that is high enough to not see from below, or high enough to declare from above after my taking it down to longblock.

[emcon5]

Originally Posted by juanbenae

love the pelican knowledge base. I was reached out to being reminded i'd need a 3.2 dizzy or swap of the drive gear to maintain the current SC diz. keep the insight coming... please.

Can't run the 3.2 distributor, it is a different animal than the hall sensor unit on the SC and won't work with the stock CDI ignition. Swapping the drive gear is much easier.

The way I see it, if you need to replace the pistons and cylinders, it makes sense to go to 3.2l simply because a set of 98mm pistons and cylinders is only a couple hundred bucks more than a 95mm set, and there is no cheaper way to get more power out of a 911 engine.

This image from Bruce Anderson's book spells it out:





The problem you can have is on higher compression engines with 98mm bores, you kind of need twin plug, because the spark plug is off to one side, and the piston dome can get in the way of the flame propagation. Steve at Rennsport had an article that talked about this on his site, but I don't see it now. If the piston dome is designed with one plug in mind, like the Max Moritz, then single plug will work, provided the compression is reasonable, I would say under 9.5:1.

You could also combine the two and make a 3.4, using the 3.2 crank and rods (replacing the rod bolts, the stock ones are made of string cheese), sending the cylinders from the 3.2 off to get bored to 98mm and replated with nikasil, (EBS Racing in Reno does this, or at least used to) with JE pistons, they have plenty of valve clearance for hotter cams.

You would probably need to address the exhaust though, SSIs are marginal for 3.2, they would be too small for 3.4.

rdane got 219 HP at the wheels with his 3.4 on CIS with 20/21 cams, I expect with Early S cams and carbs it would be way above that. The again I expect it would be way above that even at 3.2L.

[Walt Fricke]

Well, I can't confirm head fitment, but since there will be no bore change, and the stud spacing is the same, it is hard to see what the problem might be. The heads are hemispherical. If the volumes are the same - '78 vs '84, the shape ought to be the same. The 3.2 heads, of course, had larger ports, so you are looking at some machine work here, aren't you? Especially to fit the 46s? When you are test fitting the assembly of the engine you will be checking piston to head clearance as well as valve to piston clearance, and if you find issues you can deal with them by having a little machining done.

You may be lucky, and find someone who has done exactly this modification. But maybe not.

The 3.2s don't use the CE ring. Look into Wayne's book to see if the 3.2s had a slight angle on the seating surface of the 3.2 heads. However, 3.0 cylinders, with the CE rings, will work just fine here.

Hunt around with the search feature to find a chart showing head volumes - the difference between the SC and the 3.2, if any, will allow you to calculate easily enough by how much the CR will go up with the longer stroke. You can compensate for that a bit with thicker cylinder base copper rings, if you think you need to. Valves are the same size. Consult a cam grinder for the best grind for a carbureted 3.2 motor for the use you intend.

One way to deal with the distributor issue is to convert to crank fire. The HPV1 system, which should be available for a price competitive with what you will have to do for a distributor (especially if you spend $ on recurving and so on)used. These are basically bullet proof. You don't have a lot of settings, but you don't need a lot and you won't find yourself endlessly fiddling searching for perfection (i.e., more time to drive the car). If it is fuel economy you want, well you'd be looking at Megasquirt or something, wouldn't you?

[crashtest22]

just because I am curious why not use the stock 3.0 crank, rods, heads and just get 98mm P/C?
that is what I am currently doing to a 3.0.
I went with the Nickies and JE's but there are other options and would save using a new/used 3.2 crank and rods.
unless I missed why this was not an option.

[crashtest22]

and as for machine work if you do need to get the heads opened up to match the carbs I would recommend Ted at German Precision in Santa Clara. that is if your actually bay area

[Wayne 962]

Originally Posted by crashtest22

just because I am curious why not use the stock 3.0 crank, rods, heads and just get 98mm P/C?
that is what I am currently doing to a 3.0.
I went with the Nickies and JE's but there are other options and would save using a new/used 3.2 crank and rods.
unless I missed why this was not an option.

Yes, that is a good option (short stroke 3.2 or big bore on 3.0 internals) - the rod bolts on the stock 3.2 are a bit weaker than the ones on the 3.0L.

-Wayne

[emcon5]

So Wayne, now I am curious, is there anything special that would need to be done to the heads from a 3.0 to mate them to a rotating assembly and cylinders from a 3.2?

[KTL]

The heads will fit no problem. The difference in the SC heads is in the port sizes and that's it nothing else. The combustion chamber is the same size between the 3.0 SC and the 3.2 Carrera, and same shape and uses the same valves.

Walt is correct that the head volume is the same at ~90cc. I put that ~ in there because it's completely common for head volumes to vary a bit. If doing a detailed build, not a bad idea to do a little bit of grinding around the spark plug port to get all the head volumes the same, to theoretically get all of your compression ratios for each cylinder near the same.

Also agree with Walt that as long as you're doing it, do it right and make the port sizes of your head match your manifolds. In other words, get the right carb manifolds to match your '78-'79 intake ports.

The cylinders from the 3.2 are indeed the better ones to use since they don't use that pesky CE ring that really doesn't do much good anyway. This is especially important if you did happen to bore the cylinders out to 98mm. If your 3.2 cylinders are KS Alusil, that's not necessarily a bad thing if you were going to get different pistons for them. Seems that the cool thing to do has been to plate them with nikasil and use some CP pistons. The KS cylinder is supposed to be a better material from a thermal stability (lower expansion rate) than the alloy in the Mahle cylinders. The Carrillo pistons are really nice and offer an X design to the skirt and pin bore bracing. This is standard on the CP whereas JE pistons this X design is their "forged side relief" design you pay considerably extra for.

Make sure when you swap the distributor drive gear that you use a new circlip on the crank. All the crank distributor gears are not the same width, which is pretty silly but whatever, and that's why the circlip is offered in various thicknesses. In other words, don't just blindly reuse your circlip to install the new distributor drive gear. You take a circlip from your collection of various sizes and see which fits best.

I suspect you could measure the "depth" of the crank snout from the seat up to the circlip groove and then subtract the intermediate shaft gear thickness, distributor drive gear thickness, and the spacer thickness, and that would calculate your circlip size. Or you have all your stuff installed on the crank except the circlip and use a stack of feeler gauges to measure what clip size you need. I feel like it's easier to have a bunch of different clips and fit them one at a time (no need to actually install, just slip the clip along side to check for how much play or no go) for best fit. But most would probably say screw that you dummy, then I have a bunch of left over clips I don't need.

Stroke is a big deal when it comes to building these engines and it's really effective at making more power. The 3.2 crank's 74.4mm stroke (3.0 is 70.4) gets you more stroke but the 3.2/3.3/3.6 rods are a bit of a step back from the 3.0 in terms of their big end size and of course the rod bolt decrease when they went from 10mm diameter down to 9mm.

The reason 3.2 crank and rods and pistons can drop right into a stock 3.0L with no issue is because of the combination of four things. Stroke, rod length, piston compression distance (distance from piston pin center to top edge of piston) and then finally dome volume. But dome volume is mostly about establishing the compression ratio. Watch the math.

3.2 Carrera assembly theoreticals:

1/2 of 74.4mm stroke = 37.2mm
Rod length = 127.0mm
Piston compression distance = 32.8mm
Target deck height (distance from top edge of piston to top of cylinder) = typical 1.0mm

Total above = 198.0 mm to top of cylinder

3.0 SC assembly theoreticals:

1/2 of 70.4mm stroke = 35.2mm
Rod length = 127.9mm
Piston compression height = 34.0mm
Target deck height = 1.0mm

Total of above dimensions = 198.0mm again

What I mean when I say the dome volume is more about establishing compression ratio is this. Yeah the two above math exercises show that each configuration ends up at the same point in the combustion chamber at the top of the stroke. But they travel different amounts. So in order for them to have equivalent compression ratios, one piston has to have more dome volume than the other.

Generally speaking, in order for both configurations to have the same compression ratio? The a 3.0 SC assembly needs to have more dome volume because it has less stroke than the 3.2 Carrera. So that means a 3.2 Carrera assembly will work under 3.0 SC heads no problem because it's piston has less volume than the 3.0 piston when they're both at top of stroke/TDC

Make sense?

[syncroid]

The tear down is beginning.

[syncroid]

Starting to remove the valve train. 7 out of 12 rocker shafts installed backwards. Center rocker shaft bolts stretched far enough that the large allen end has the bolt halfway into the nut. Rocker faces look like they were "re-finished" on a belt sander. Rocker face to camshaft mating areas not flat.

[crashtest22]

lol thats cute. I love it when people "Know" what they are doing

[emcon5]

Originally Posted by syncroid

The tear down is beginning.



]

what are we looking at here, is that a casting artifact in the case? Or a crack?

What is the story on the red head studs?

Originally Posted by crashtest22

lol thats cute. I love it when people "Know" what they are doing

Well it is motormeister, so they should know what they are doing. They just chose not to do it right from the looks of things.

[Trackrash]

What do the pistons and cylinders look like?

[syncroid]

Cam shaft thrust washers and shims were installed backwards. Shims were against the cams and the thrust washer installed after the shims both sides. Non-updated flimsy cam retaining plates.
Cylinders look like 3.2 that have been bored out to 100mm. Also, cylinder #4 looks like it is losing it's plating. Not sure what kind of pistons these are. Maybe JE?

[syncroid]

Originally Posted by emcon5

what are we looking at here, is that a casting artifact in the case? Or a crack?

It looks like a casting artifact . I should have clarified what I was pointing at. I think the main oil leak was from the case through bolt o-ring area.