mcculloch rod bolt post

[steve welte]

Dave the bolts were at 80 inch pounds. Yes the engines spin at 11,500 to about 12 all the time. Some need to understand we often put more laps on that many people would. It's not uncommon for us to go for a practice day at say Sugar River and run 75 + laps. These were 1" alky carbs on box mufflers engines. It will be some time possibly before we hear anything on the rod bolts. I doubt USMP cares about us or giving a break on bolts. Hard enough to even get an engine from them. The Bennet rods benefit ,I think, from the fact that they have the dowel pin to locate the cap and that takes a lot of stress off the bolt. But that's' my 2 cents. What do I know? I just feel there was a specific reason why the McCulloch Corp. didn't just use any rod bolt in the engines they produced.

[David Luciani]

i agree mcculloch probably had good reason to spec such a strong bolt.
keeping in mind most of their engines were put onto saws running at around 6,000 rpm at most.
it's amazing we get away with what we do in the karts.

[steve welte]

I've walked over at a few events where a rod has broken?. Guy will show the pieces and say the rod broke. Look closely at the parts the cap will be in about 3 pieces and the broken off bolts are still in the rod main beam. Sometimes the main beam is broken sometimes not. I'll say , nope the rod bolts broke, and I get that weird look like, disbelieving.

[David Luciani]

i can visualize exactly what you're saying.
i suppose the bolt starts a twist shear where the head attaches to the shank.
if either bolt head lets go the caps would break into pieces and probably shear off the other head too.
 
i tried once again to search the web for bolt info figuring that the information pool grows daily and something may be there that wasn't.
i also changed what i searched for and long story short i got different info.
heres a blueprint of a bolt that has 220 ksi strength sold as aircraft supply.
the title of this page is
TITLE
BOLT, DOUBLE HEX HEAD
PH 13-8Mo CRES
220 KSI TENSILE


       

i've also found surplus company that has the same.
issue may be cost as it seems like these bolts are priced at 40 to 80 bux each .
probably me not understanding something.
anyway if we could get the actual specs of the mc101 bolt added to this blueprint it would be useful when i talk to supplier.
probably need the size specs on the print for A (dia),C (min), W,H,E (min),V, D (dia),Nom Grip
who knows maybe we'll get lucky

[Randy Dacus]

The right place to find racing fasteners :

They make bolts to your specs if need be !

http://arp-bolts.com/

[steve welte]

Yeah Randy but they don't normally make a special bolt in this size. Special information is pending right now. Anybody got deep pockets?

[Tom Smith]

Good rods bolts are generally made from MP35N, a nickel - cobalt multiphase alloy.

[Vince Rosanelli]

Lots of great information on this thread and lots to learn. If someone would be kind enough to consider posting, I’m curious to know of the bolt specs for each of the Mac spline bolts on the 100cc and 101 series and of those for the West Bends. I tried referring to the parts list for my 101AA but it only refers to the rod bolts as specialty bolts and does not provide the diameter and thread count. It appears that bolts in the range of 220ksi and higher are required, or at least, preferred.

Since there has been lots of discussion on cost, what would one consider a good price per bolt or per a box of 100? Even if they are relatively pricey, as stated, the cost would be nominal in the grander scheme of things as compared to the cost of blowing an engine. We have a locally headquartered aerospace company right down the main road from me. I sold a kart to one of the gentleman there last year and was curious to see if he would be able to source the spline bolts in question and if he can get them cost effectively.

[steve welte]

You can check but a lot of leg work has already been done. It won't be cheap. I look at it in that 2 bolts are cheaper than a $800.00 engine. Some people don't have an issue as many rebuilt engines never see the track to be blunt and honest. For those of us that run hard it is a real problem. I hear of 210K and 220K bolts being able to be purchased but then when I go to the source I'm told about they turn out to be 170 to 180K bolts. Just had this happen in the last hour. So it's pony up or don't get in the saddle. We are looking a 260K bolts.

[David Luciani]

a good price is hard to define.
when the 101 bolts were everywhere they ran about 6 to 8 bux per pair.
re-using them was o.k. but only once if you wanted to be sure.
at the same time the standard mc91 bolts were around 2-4 bux.
those you threw away every time you pulled out the con rod.
bonbrights bolts were something like 14 bux each but were reusable for at least several times.

now mc91 bolts are about all gone and finding mc101 con rod bolts is getting really hard.
i have no idea about current pricing as i've had a big stash but now they are running low.

the problem is getting a bolt that small to be that strong requires special processes and alloys.
typically aerospace or military grade and spec.
if you've ever research something like that you'd find they are NOT CHEAP.

right now the best price i've heard is right around 30 bux each from us motors.
getting them to actually ship some is sketchy at best.
if we get them back around 14 bux each that would be an acceptable price.
the stronger 260ksi bolts can be re-used at least a few times safely .

even if i could re-use them just once that would work out for me and most engine builders.



terry ives figured out a general spec on the bolts that'll fit both motors.
the spec will fit mcculloch rods about 1+ threads past shoulder.
  fits west bend 820 about 1+ thread short of rod shoulder .

both would be well with-in safe spec for motor.
if you were running a stroked mc motor you might have to shorten the thread a tiny bit .

hopefully we'll get a new supply soon.