Briggs & Stratton 993cc "Big Block" engine conversation thread

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Stuffengineer

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Sorry to hear that Ken. Hope your better soon.
Stripped down a 40 so no flywheel or stator/regulator all tin starter etc. Only thing I left on was the intake and EFI components, oil cooler/filter and full oil.
Weight was 80.5 lbs 36.4kg.
 

Vigilant1

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Ken
You might just ask Arrowprop directly about their prop hubs and the B&S 993 tapered shaft options.
 

Ken Powell

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Stuffengineer - that is great info on the taper. Now I know what to ask Arrowprop. Did you strip a 40 HP engine or a 40 cubic inch engine? Longblock weight of 80.5 pounds would give me 20 lbs for prop hub, ignition system, exhaust, intake and carbs.
 

Stuffengineer

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Stuffengineer - that is great info on the taper. Now I know what to ask Arrowprop. Did you strip a 40 HP engine or a 40 cubic inch engine? Longblock weight of 80.5 pounds would give me 20 lbs for prop hub, ignition system, exhaust, intake and carbs.
HP. Engine still had intake throttle body harness injectors etc.
 

Ken Powell

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PTO is 2.25 taper per foot
3.8” total length.
I do not have the engine yet and I am trying to confirm the taper dimensions. And yes, I need to make a few phone calls to confirm engine crank taper and Arrowprop capabilities. On your engine: What is the 'large' diameter of the crank before the start of the taper? Where does the taper start?
 

Ken Powell

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I have ordered an engine.
61E377-0027
This engine has the 'pink' valve springs (and I think the steel pushrods) and shares many parts with the 40 HP Marine engine.

I also ordered:
J609B Shaft Sleeve Adapter 7/8" Tapered Shaft Into 1 7/16" Diameter Straight Shaft
J609B Shaft Sleeve Adapter 7/8'' Tapered Shaft Into 1 7/16'' Diameter Straight Shaft Keyed | Tapered Shaft Sleeve | J609B Sleeve

The idea is to be able to use either a tapered prop hub or a 1-7/16" taper lock hub.

The Arrowprop website has disappeared. I'll give them a call tomorrow to see if they are still providing prop hubs.
Question: What prop flange pattern for the hub?
1. 75mm Rotax
2. 3-1/8" 1/2 VW
3. 4" VW
4. SAE 1
 
Last edited:

karmarepair

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Ken Powell

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What I really need is a hub with an inside taper to replace the flywheel. My 9" Southbend lathe (built in 1932) does not have a taper attachment (but is tight and will hold a 0.001 runout tolerance). Any ideas on where I might find a flywheel hub for a 993cc? Maybe ARC?
 

blane.c

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Yes hub taper is short and compound will do it. The taper can be divided into 3 sections, the small end and the large end and a section in the middle. The middle section does not have to have contact with anything, it doesn't matter. The small end and large end need to have proper contact.
 

Stuffengineer

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I wouldn’t put prop on flywheel side. Check into what bearings are in that particular model. I think it is only a sleeve bearing on flywheel not sure about pto end.
 

Stuffengineer

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Each different model build will have something different. OEM’s will have there own model number and can spec what bearings crank etc. They have more choices than you buying one off the shelf.
 

rv7charlie

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I wouldn’t put prop on flywheel side. Check into what bearings are in that particular model. I think it is only a sleeve bearing on flywheel not sure about pto end.
Most use sleeve bearings on both ends, but the PTO end is designed for bending loads.
Lyc crank:
Lycoming crankshaft.jpg
'industrial engine' crank (flip the image to align the pto end with the Lyc's prop end):
Generac crank.JPG
 

Ken Powell

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The prop will be installed on the PTO end. I am removing the flywheel and starter. I plan to use an aluminum disk on the flywheel end for the HEI ignitions (separate ignitions for each cylinder and 2 pickups for each HEI system. One pickup at 12 degrees BTDC and the second at 28 degress BTDC. Start on the retarded pickup then switch to the advanced pickup.
 

Ken Powell

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I'm a real amateur when it comes to machining and had not considered using the compound to cut the taper. I have some 2" 6061-t6 aluminum round stock to use for practice.
 
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