The Stovebolt Site Forums The Shop Area Driveline 11 inch flywheel

Would anyone know whether the 11 inch 6 bolt flywheel, clutch and pressure plate used a different bellhousing then the 9.5 and 10.0 set ups?

There are 2 different sizes of bell housings used with the different size clutches. Mostly the cars used the smaller ones & the trucks the larger ones. There is an overlap though but I am not sure of the applications.

George

George,

I don't believe that's correct. Trucks came with either 9.5 or 11 inch clutches, and looking at the parts listing (attached) there's no mention of differences do to different size clutches. The flywheels were the same diameter, just the clutch disk and pressure plate were different. The 11 inch pressure plate and flywheel used 9 bolts to attach the two together. The 11 inch clutch is fairly scarce, usually used on big bolts.

My 11 inch, 6 bolt clutch and flywheel fit the original bellhousing that came with the 216 in my '52.

A 216 in 52 could have had the heavy duty 10-3/4 clutch from factory in a 1 ton truck (I have many of this exact configuration)
And that flywheel and pressure plate measure exactly 11 inches across so you could swap out the clutch disc with the fancy new big boy 1954 11 inch disk that actually gave you that extra 1/8 on the radius for a full 11 inches across without changing any other parts.
-s

I think I am going to have to try and get my hands on a 6 bolt 11 inch late 56-62 flywheel to see what the measurements are between the holes for the pressure plate. I don't have one in my stash of stuff to see if the measurements might work with an aftermarket pressure plate and clutch.

I have a steel flywheel that I purchased directly from Jack Clifford in 82 or so on my current 261 motor. They were made for Clifford by McLeod but not too many were ever made so profoundly rare. I spoke with McLeod and they were not willing to go to the trouble of making any more of them, other then at an outrageous cost (you don't want to know what they ball parked it at. Sort of the old, I will do the job only if you pay silly money). The McLeod flywheel has held up like no one's business and after all these years of me punishing it, not a mark on it. Would love to have a second one. My youngest son is in the middle of building a 261 and the 9.5 inch clutch is just not doing it for me. So its sort out something with an 11 inch flywheel, or some other alternative.

One thing I don't know, again because I don't have any in my stash of stuff to compare, is whether the 235 and 261 cast flywheels are the same as the small block flywheels, just with the additional dowel pin holes. Having a small block steel flywheel drilled for the additional dowels might be an option if they are.

Another option, Mike Norcia at Ram Clutch tells me that they can probably make a steel flywheel up but would need a sample. Standard 10.5 steel flywheel, using standard pattern GM pressure plates and clutch plates, and thus able to use aftermarket pressure plates with higher clamping forces, decent clutch plates with stronger materials.

Mike, I have an 11 inch that came from a total loss wrecked 1954 Corvette. I was pretty surprised...people all wanted to buy what was left of the engine but the flywheel was just sitting there. I used it when I converted to the T5 and it has been the best flywheel I've ever had. The extra 1 inch makes a notable difference. A friend of mine adapted one of the SBC flywheels. I didn't see it after he finished but he said he ran into some problem he didn't expect. I'd ask him what it was but he is no longer with us. Good luck in your search.

Best flywheel in what way? Clutch grabs better?

Its more efficient. Larger face on the clutch plate and flywheel so more surface area for the clutch to get hold of, more ability to not slip under heavy load (even when the clutch is a little long in the tooth), better ability to dissipate heat.

Probably apples and oranges, but my 168 tooth, GMC 302 flywheel is an alternatively drilled BB Chevy flywheel, made by McLeod. They still offer the BB flywheel and I would assume they could have the blank drilled as necessary.

They tend to feel more like a new clutch for longer. Overall quieter and more well-mannered if that makes sense. Interestingly the T5 I got (from an Astro Van) was mated with the 11 inch clutch if the larger passenger capacity option package was chosen. So an 11 inch disc wasn't all that hard to find.

I have been thinking about the SBC flywheel and I think I was told the center section (where it mounts to the crankshaft) wasn't the same size as the 235. Jerry (HRL) would know and might even have one he could look at for comparison. I don't think it was smaller than the 235, however. I think it was larger.

Been considering the Astro 14 spline clutch for my T5 swap. Would I have to have the 11 inch - 235 flywheel to make that work?

No...the T5 won't care what size flywheel you have as long as the clutch disc and the pressure plate are the same size and the spline count matches the input shaft. I did have to make a new connecting link for my clutch. A couple of other folks have told me they had the same issue. The short throwout bearing didn't provide enough length to let the linkage adjust right and the long bearing wouldn't fit. I just used some 5/16" steel rod and all was Jake after that.

I could check the GM Heritage page site. I think the Astro Van came with a 10 inch clutch and 11 for the extra passenger package. Edit...just looked and GM says 9.125" for standard Astro Van.

I didn't measure & calculate the extra contact area but the area of a 10 inch circle is 78.5 and the area of an 11 inch circle is 95 just for comparison.

Poorly worded question there. RockAuto lists the 2.8 v6 versions of the 1988 Astro Clutch as 11 inch disk. Would I need the bigger 235 flywheel to use that disk?

Are 1 ton trucks that rare in the USA?
A 1 ton truck that is the correct voltage for your desired starter in 47- about 56 model years

It will have all the parts you need to run an 11 inch clutch
Or you could just use the 10-3/4 it comes with assuming it’s usable or hasn’t been replaced with a smaller disk yet.

My info is based on what all the Canadian 1 tons had from factory, maybe USA used different clutch setups?

The clutch and flywheel in the 47-mid 50s is the same regardless of engine size, there was no “235 larger parts” you find the same transmission bits behind 216 and 235 in that’s time range if it was a 1 ton.
-s

I’ve run across these two different flywheels during my 63-66 C10 journey. Both are 168 tooth. Car flywheels have 153 teeth IIRC.

Summit Racing sells a 14 spline 10.5” clutch disc specifically made for th T5 market. Not cheap but it solves the problem for many folks.

Is there any reason to believe that “this here” flywheel᠁..


᠁..would not accept “this here” clutch?


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I’m not very familiar with how one goes about matching these components. That is a 1962 C10 flywheel and a 1988 Astro van clutch. Both are listed as 11 inches. Seems to be the “match” should be based upon the bolt circle diameter, but I’m not sure how that really works or how you tell based on the various specs they list with each component.

JW51,

Should work but the pressure plate bolt holes need to match the holes on the flywheel.

There are raised and flat diaphragm options. Does anyone happen to know which would be needed here?

Sorry...I missed this question. That flywheel is not for the 235. The 235 flywheel has 6 mounting bolt holes and 3 spaced dowel holes. Please see the attached image. I think that flywheel Rock Auto shows is for the early SBC models. The mounting flange for the SBC is (as I recall) 3.58 inches and the 235 is 3.875 inches, so there is that problem first off. The crank mounting flange is smaller by about 1/8 inch on all sides. So there is no precision there for you. Next you will have to have three dowels drilled to match the 235 flywheel (and get them perfect or you will shake more than Elvis at any speed since the flywheel wasn't made for that crank). And then I don't know if the bolt holes match, either. I mentioned a friend did this once. He finally got it done but when I asked him about the work he just shook his head and muttered something under his breath.

FWIW Rock Auto's flywheel listing by application includes a flywheel for 235/261 L6. I ordered one and got the correct part number in the correct box but it's the SBC flywheel and can't be readily adapted to an I6 235/261. I sent it back with an explanation of the error in their application listing. That was 2 years ago. Chevrolet made a 262 V8 listed as 4.3 as is the 261 L6. That's probably where their parts people got confused.

I was looking to replace my 9-bolt 10-3/4" clutch with the still available 6-bolt 11 inch clutch. It was a no go on my search for a flywheel so I had the 9-bolt flywheel resurfaced and all is well. The machinist who did my flywheel suggested that When the time came to replace the clutch that I just have the 9-bolt flywheel re-drilled for 6 bolts.

Also note from the parts books, that the 54 flywheel is unique to that year and the bell housing changed in 54 also. So you can't use a 54 bellhousing in earlier trucks because the frame crossmember is different. The 54 flywheel has the 6V tooth count on the ring gear and 6 clutch bolts so you could use it in earlier trucks with a 6-bolt, 11" clutch. 55 and on flywheel has 168 teeth for 12V starters and 6 clutch bolt holes so you'd have to change starters along with the clutch and flywheel to use that flywheel in 54 and earlier trucks.

One of the parts they list (happens to be out of stock)᠁.has the 6 bolt holes and 3 dowel holes like Jon G described.

That was good info. I’ve not laid eyes on my flywheel and had no clue. Typically have pretty decent luck with RockAuto. Sounds like they have major issues with this particular flywheel application.

For what it is worth around 2002 or 2003 I tried to find a new flywheel for the 235 (a friend wanted one). Suppliers said they had them, but if you bought one (it had to be special ordered and paid for in advance) they'd return your money with the explanation they were sorry but it turned out to be unavailable...even though they showed in inventory and there were even pictures of them you could see in the parts catalogs.

A fellow I knew who owned a machine shop here also tried his sources but couldn't find one. He said one place (think it was McLeod but he never mentioned them by name) told him they could custom make it but the cost would have been something in the neighborhood of $500 or $600 plus an additional charge for balancing/shipping and he was going to add 10% to that for his effort.

Turned out a used flywheel resurfaced by Wade Transmission & Gear was ok after all.