The Stovebolt Site Forums The Shop Area Engine Shop 261 swap flywheel recommendation needed

I am working on putting a 261 in my 39/40 1/2T truck. I would like to keep the footstarter. I have a 47-53 modified Bellhousing already to accept my pedal assembly as well as mate to the SM420 that I plan to use. The trouble I'm running into is the only flywheel I have is for a 1940 216 which has 3/8 bolt holes. Its also only 9.25". But, it is the correct 139 tooth ring.

I am looking to see what others have done.. recommendations on either a new flywheel I can purchase from rock auto etc or a part number I can post in the parts wanted. I feel like I can get a new clutch kit pretty easy it's the flywheel that's the issue.

I mostly plan to put put around maybe 500 miles a year so is the 9.25" flywheel really that big a deal or should I go with a 10" flywheel from a 235?

The picture posted is the 261 that I have showing the bolt pattern that I will need.

If the bolt and dowel pin spacing of the flywheel is the same as the engine, just drill out the flywheel to fit the larger bolts. The dowel pins carry the driving torque, so you can make the holes a few thousandths larger than the bolts if necessary. The later model engine uses a 7/16-20 bolt. That's only a slight enlargement of the existing hole, so the 7/16" drill should self-center in the existing holes if you use a drill press and align the bit carefully before you drill each hole. I'd suggest using a 3/8" bit to align with the hole, clamp the flywheel to the drill press table and then swap to a 7/16" bit to enlarge the hole.
Jerry

Would you drill them out or would you look for a 42 and up flywheel with the 7/16 holes? If memory serves me correctly, doesn't the later flywheel also have a slightly smaller center bore? That would leave a small gap around the crank flange.

I know it's a bit undersized for the 261 but do you think it'll be a major issue? Obviously I wouldn't want to be romping it.

Unless you're planning to do real truck stuff with an antique vehicle, I don't see a problem with using the smaller clutch. There are plenty of good condition used 235/261 flywheels available that can have the clutch contact surface reground- - - -no point in throwing away good money on a brand new one. Just be sure to get one with the 139 tooth 6 volt ring gear. I'd machine a spacer ring for the center hole if I was doing the swap- - - -just a few minutes' work on the lathe and a piece of pipe nipple.
Jerry

I used a 1951 216 flywheel on my ‘61 261 without any issues. Just make sure you use the correct starter for that flywheel. I’m sure you can find a used 216 flywheel or early 235. Maybe someone knows the year they changed the teeth number so you can find one below that year.

Chris

I think this is the direction I am headed. I posted an ad for a 42-53 flywheel in the parts wanted section just now. I have a good 6v starter for a 139 tooth flywheel. I was told it was good at least lol. I have the 40 flywheel but If I can pick one up reasonably, I can keep the 40 as a backup down the road.

Do you remember if your center bore of your flywheel had a gap around the crankshaft flange? I had read somewhere that the earlier flywheels had a slightly larger inner bore. Where as the 42-53 center bores were slightly smaller (IE fit snug around the crankshaft flange.)

What flywheel options would I have if I moved to a 12v foot stomp starter? I think my limiting factor here is that I am using a 47-53 bellhousing, right? I was under the impression that an 11" flywheel wouldn't fit these. The OD is only about 1/16 larger for the 11" flywheel.

For a flywheel you will have to find a 55 2nd or later flywheel drilled for whatever clutch you want to use. 6V and 12V starter drives are not interchangeable so you have to use the 12 V starter with 12 V starter drive. Flywheel ring gears are not interchangeable either. You have to have a 12V flywheel as the 12V ring gear does not fit the 6V flywheel. Don't ask how I know, it was a long process. Some 6V flywheels are drilled for 9 rather than 6 clutch bolts to accommodate the larger clutches, which are 10-3/4" rather than 11." 9 bolt clutch covers are no longer available so you'd have to have one rebuilt. I have run a 6V starter on 12V for 20 or so years with no trouble. It does spin the engine over faster and sounds different. It is presently starting a 9:1 CR 261 without complaint even at 0 deg. F.

I have the 11 inch flywheel in my 47-53 bellhousing, works just fine. It is the full 11 inch clutch surface, not 10-3/4.

What flywheel and clutch combo are you running on the 6v starter? I'm thinking about moving forward with the 9 1/8 clutch from a later model 216 that has the 7/16 bolts. I haven't figured out the clutch yet.

So are you running the 12v stomp starter then?

It's the 6V stomp starter running on 12V.