US 820?

[Tom Day]

Tom, K Prec. doesn't always have all the rotating parts. A lot of us do not like the tapered end crankshafts, as the 3/8-24 threads are weaker. We want the old style 55/8" to 9/16" stepped crank wit the 7/16-20 LH threads. I have never seen the clutch from an old style West Bend running down the track at 65 MPH with the end of the crank in it. I bet I've seen fifteen Mac cranks broken off at speed in the last 60+years! Also, the single ring piston still has a 1/16" ring. We need thinner rings for less wall friction and more RPM. I don't know where Engine Masters was getting his .030 rings, but that, or Louie Figone's 1mm ring Arias piston was the hot ticket. Someone should resurrect the old Wiseco/Victor/Fuller pistons with the .024 rings. Ted

It sounds like the 820's will be coming back, Liz had a long discussion with Dave Bonbright, he is going to help her get back on track, the previous owners drove US Motor down (pocketed the money and did not deliver product). Dave talked to her about the steel rings, rods, cranks, pistons, blocks, etc.  Liz got the cylinder tooling back that Dave designed for the new block. It may take a little time for her to get things going but it sounded like we will be seeing 820's again. Dave is pushing her to use the good rod bolts in all the engines as that is the weak point in a rod that has a removable cap.

Hi Ted,Just wondering what are the good rod bolts you are talking about?   Tom Day

[ted johnson]

Tom, MS Aerospace was making the 250+KSI socket head screws of a super cobalt alloy called MP159. They can be torqued to 110-115 inch-pounds, and can be reused. Never reuse ordinary rod screws. The "good" screws look like socket heads except the alloy is a different color, and they have a small radius fillet under the head.
Anyhow, now that Dave Bonbright is helping the new owner, it looks better for vintage karting. Ted

[Tom Smith]

Tom, K Prec. doesn't always have all the rotating parts. A lot of us do not like the tapered end crankshafts, as the 3/8-24 threads are weaker. We want the old style 55/8" to 9/16" stepped crank wit the 7/16-20 LH threads. I have never seen the clutch from an old style West Bend running down the track at 65 MPH with the end of the crank in it. I bet I've seen fifteen Mac cranks broken off at speed in the last 60+years! Also, the single ring piston still has a 1/16" ring. We need thinner rings for less wall friction and more RPM. I don't know where Engine Masters was getting his .030 rings, but that, or Louie Figone's 1mm ring Arias piston was the hot ticket. Someone should resurrect the old Wiseco/Victor/Fuller pistons with the .024 rings. Ted

It sounds like the 820's will be coming back, Liz had a long discussion with Dave Bonbright, he is going to help her get back on track, the previous owners drove US Motor down (pocketed the money and did not deliver product). Dave talked to her about the steel rings, rods, cranks, pistons, blocks, etc.  Liz got the cylinder tooling back that Dave designed for the new block. It may take a little time for her to get things going but it sounded like we will be seeing 820's again. Dave is pushing her to use the good rod bolts in all the engines as that is the weak point in a rod that has a removable cap.

Hi Ted,Just wondering what are the good rod bolts you are talking about?   Tom Day

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  Screen Shot 2018-08-11 at 2.33.13 PM.png (Size: 376.66 KB / Downloads: 17)      MS Aerospace rod bolts.

[ted johnson]

Cool shot, Tom, but the MS drawing I have shows a standard socket head cap screw, but with the fillet under the head. I haven't the foggiest idea where I stashed the drawing, since my previous computer passed into the "other realm". I may have lost it like hundreds of other files and photos. The Bonbright bolts I have here look standard, except the fillet and the color of the material. I also have the earlier bolts with the splined or multi point heads. These hit the crankcase and stuffer, but they ARE made of the MP159 alloy. Ted

[ted johnson]

Tom, I was afraid of that. Looked everywhere on this and my Pro/Engineer computer, but I believe that MS Aerospace drawing is on the defunct computer. If I ever get rich enough to have a hard drive recovery done, it'll show up. Guess I could get it from Dave. TJ

[Tom Day]

Tom, MS Aerospace was making the 250+KSI socket head screws of a super cobalt alloy called MP159. They can be torqued to 110-115 inch-pounds, and can be reused. Never reuse ordinary rod screws. The "good" screws look like socket heads except the alloy is a different color, and they have a small radius fillet under the head.
Anyhow, now that Dave Bonbright is helping the new owner, it looks better for vintage karting. Ted

Ted,are those screws available anywhere?

[ted johnson]

Tom, not unless someone has a set stashed away somewhere. The 12 point set I have, I got from Terry Ives he had them put away and I bought 'em. Dave Bonbright doesn't have any for sale, and I imagine anybody who has any is keeping them for themselves. My Bonbright 610 and my Libberton have them, and thank goodness they can be reused. I remember when I could call Engine Masters (Bonbright) and get a set any time. Jeff K. at K Precision advertises a high strength screw, but one of the guys I know had the head pop off one of them on the workbench when it was just barely tight. Most socket heads are 170KSI tensile, but Unbrako screws are 180KSI, so maybe you can find a box of these. Don't torque them past 90 inch-pounds. If someone has a better solution, please post it! I keep hearing of a screw that the Bennett folks have, but I don't know any more about those. I'm retired from aerospace now, so I'm out of that loop. Ted