2.4 Crank in a 2.0 Case

gsjohnson · 01-19-2009, 07:05 PM

I will be performing a performance build for my 72T (The matching numbers motor will be stored away) and I'm trying to piece together a couple of different motors that I have into one. I have a 73 2.4 and I also have a 2.0 motor with 2.2 E pistons, cylinders, and E cams. The simplest and most inexpensive build would be to drop the 2.4 crank into the 2.0 case. I've performed a search as well as researched Wayne's book and have not found the answer. Will a 69 T 2.0 case accept a 2.4 crank without modifications? If not, what modifications would be required? Wayne mentions that the 2.4 crank is a no mod drop in for the 2.2 case, but there is no mention of this mod for the 2.0 case. Can someone clarify this for me?
Thanks

Jim Dorociak · 01-19-2009, 07:53 PM

I would think the best motor would be the 2.4 case with that crank matched up with the 2.2 E P/C's. The book from Bruce Anderson really does a great job describing all the performance upgrades and issues with all the early cases. Oil by pass modification comes to mind, unless you have the aluminum 2.0 case from a 65 or 66 911 I would stay away from the 2.0 mag case. The 7R case is the strongest. Have fun reading keep searching most of this is covered somewhere as it has all been done before. Jim

YTNUKLR · YTNUKLR's Garage

You could use an early aluminum 2.0 case. I would recommend using a 2.4 case. I have a 72T case in excellent cond. in L.A. 69 is generally not the best unless you have a 69 car, needs a few updates.

gsjohnson · 01-20-2009, 04:47 AM

I have a 73 2.4 case, crank & rods. Are you guys saying that the 2.2 E cylinders, heads, etc are a direct bolt on to the 2.4? And which rods would I use? Again, thanks for the imput.

Bobboloo · Bobboloo's Garage

Yes, the 2.2E P+C's will bolt up to your short block 2.4. The 2.2 and 2.4 heads are the same. Use your 2.4 rods with your 2.4 crank.

Is your motor MFI or CIS?

gsjohnson · 01-20-2009, 08:24 AM

Quote:

Originally Posted by Bobboloo

Yes, the 2.2E P+C's will bolt up to your short block 2.4. The 2.2 and 2.4 heads are the same. Use your 2.4 rods with your 2.4 crank.

Is your motor MFI or CIS?

I have a set of Webers for this project build.

djpateman · 01-20-2009, 08:52 AM

Are you sure the 2.2 pistons can be used on a 2.4 rod? I'm not sure of the relative pin locations. At the very least, the compression ratio will be bumped up a fair bit. Maybe too much.

Zeke · 01-20-2009, 09:27 AM

Quote:

Originally Posted by djpateman

Are you sure the 2.2 pistons can be used on a 2.4 rod? I'm not sure of the relative pin locations. At the very least, the compression ratio will be bumped up a fair bit. Maybe too much.

Depends on the piston. Yes, the 2.2 S piston would be up around 10.5:1. Use E pistons for comparable S compression. The cams and clearance are critical here. I wouldn't just throw something together from the grab bag.

gsjohnson · 01-20-2009, 02:36 PM

Still looking for more imput. Thanks

gsjohnson · 01-21-2009, 06:29 AM

I will be running the E pistons, so am okay with using the 2.4 rods? Any pitfalls?

911pcars · 01-21-2009, 09:39 AM

To answer your original question: Will a 2.4 crank fit into a 2 liter case w/o mods?

Yes, but the case should be brought up to specs (line bored, oil squirters, proper head studs, TimeCerts, etc. However, I'm not sure what happens when you try to connect the 2 liter con rods/pistons to a 70.4mm crank. Anyone?

With 2.2 and larger P/Cs, the 2 liter heads must be flycut to accept the wider cylinder sealing surface and gasket. Larger cylinders require the crankcase spigots to be enlarged. Pistons and piston-to-valve clearance depends on the valve dimensions and the camshaft of choice.

The best cases for ultimate strength is the aluminum type and the later 7R reinforced mg. case. Any case can be shuffle-pinned for added regidity.

Sherwood

Grady Clay · 01-21-2009, 10:23 AM

Good advice above.

I would make sure any case is straight and undamaged before investing any time and money.

Using the 2.4 case is your best choice. It already has piston squirters and will clear the 2.4 rods. You will want to install case inserts, new cylinder studs, insert for the main case studs and the studs at the jackshaft bearing boss. The ‘oil bypass’ mod is a must.

The 70.4 mm 2.4 (2.7)crankshaft must be used with 2.4 (2.7) rods. You cannot use 2.0 or 2.2 rods on that crankshaft (and vice versa).

You may have a 5R or 7R 2.4 case but that is FAR better than the mag 2.0 911T case. In any event, the 70.4 crank rods won’t clear the 2.0 case at the cylinder spigots without removing some metal. You should also pay attention to the rod clearance to the cylinder spigots. Your piston skirt-to-crankcase clearance should be OK with the 2.4 case but you should still check. The piston skirts with the 70.4 crank and rods will not clear the 2.0 case at BDC without removing some case metal.

I understand that you can use 911E cams with this conversion but I would still measure the valve-to-piston clearance and the piston-to-head clearance. I suspect you cannot use 911S cams in this configuration.

With this high compression ratio (you should measure each cylinder), you might consider twin sparkplugs. In any case, this high compression will require high octane fuel.

I recommend you do a lot of research before lighting into this project.

Best,
Grady