Vintage Karting Forum

guys, i'm listing a link here with an old rod bolt post for mcculloch engines.
worth reading.
it's hard to believe it was eight years ago this info was posted.
time flies.
heres the original post on Rear in case the links don't work here.
mcculloch rod bolt post 2010

i pasted the post below and the links still seem to work here

Howard ochocke » Mon Dec 27, 2010 1:00 pm
Who is a good source for small quatities of rolled-thread cap screws. I need them for McCulloch head and rod cap application. Does McMaster-Carr carry them?

ted johnson » Mon Dec 27, 2010 4:05 pm
Hillman fasteners is always a good on-line source. Ordinary black oxide steel 180KSI socket head cap screws are fine for head bolts. McMaster Carr's part No. for the 1 3/8" long is 91251A250. For rod bolts, the McCulloch spline head bolts are fine. You can find them from REAR members, and on eBay at times. You'll need the special wrench. If you go for overkill, Dave Bonbright has 310KSI super rod screws, but be aware that they'll cost you. I used them in my modified W.B. 610's, and I have them in my Mc101. If you want to use them in a Mac, Dave can shorten them properly for you. Great insurance.

Dave Bonbright
West Bend 610/820 guru
Enginemasters
557 Este-Madera Dr.
Sonoma, CA 95476
P.O. Box 14,
Vineburg, CA 95487
(707)938-8122
powerbee1@aol.com

Good hunting. Ted

Bill Hermsted » Thu Dec 30, 2010 10:51 am
I just bought six spline drive 10-32 capscrews from GEM. They were $ 3 apiece, but a cheap insurance policy since they should never be reused.
Hope you had a nice Christmas and have a happy New Year!
bill

Bob Towarnicki » Thu Dec 30, 2010 1:37 pm
Comet still lists rod bolts for $1.00 each under "McCulloch Miscellaneous Parts" in their online store.
Bob


ted johnson » Thu Dec 30, 2010 3:35 pm
Bob, the only downside to the ones CKS has is that they're not the 210KSI splined bolts, just regular socket heads. TJ


 Scott Kneisel » Thu Dec 30, 2010 3:53 pm
Yes, I bought a pile of the Comet screws thinking I got a great deal however, they turned out to be regular Grade 8 alloy screws. I ended up paying a buck each for 20cent screws. I called them and talked to someone from the engine shop and they told me that they agreed that they were regular alloy screws but the length was special. OK, that is true. They also told me that they have been using those screws on every Mc9x engine they have built over the years and have never had a failure, they simply change them each time they take the rod apart. That got me thinking about the special rod bolts and are they really needed. I still like to use bolts that have a higher tensile strength than standard alloy bolts so I started looking around and found that Holochrome bolts as well as Unbreako bolts do have about a 10,000L better tensile strength and thay are not as pricy as 101 bolts so I have been using them in all my engines up to Mc91. If I build a modified engine or a 101 I use the 101 screws just to be sure. I have torque tested the Unbreako(UK) and FKE bolts from Tiawan and they start to yield at 120-130inLb so torquing then to 95-100in-lb is plenty safe. I personally use the FKE bolts and have had great luck with them. I also replace them each time I take the rod apart but they are cheap enough that it isn't a problem. I do have to shorten the 3/4" screws but that is real easy.
That is my 2 cents.
The Unbreako and Holochrome bolts are available at McMaster Carr and I think they are about 50 cents apice. The FKE bolts are harder to find, I bought a couple boxes of 100ea so I have plenty but the supplier I bought them from has changed brands so I can't say where to get them at this time.

That is my 2 cents
Scott

 ted johnson » Thu Dec 30, 2010 5:56 pm
Scott, I've occasionally gotten Unbrako screws from McMaster Carr, but most of the time they supply another brand, such as Kerr. These other brands are good screws, but have a 180KSI tensile strength as compared to the 190KSI tensile of Unbrako. Some of the hardware I've gotten from McMaster has even been Chinese. I refuse to take a chance on Chinese hardware in high stress situations after the problems NASA has had with Chinese screws not meeting the MS/NAS/AN standards. If you know of a way to ensure that you get Unbrako brand, please share, as I'd surely like to use them!
BTW, on the getting crankshaft seals from McMaster, I ordered 3 PTO seals for the Mc7's, and they came in yesterday. Lo and Behold-they were SKF brand. I was really pleased. Since it was you who suggested McMaster for the seals, thank you very kindly! TJ


Scott Kneisel » Thu Dec 30, 2010 6:23 pm
TED,
I got the supplier mixed up.
It is MSC direct that gives 4 options of what brand.
Import, Made in USA, Holokhrome and Unbrako

Try this link but if it doesn't work go to the MSC direct website and they are on page 1904 of the catalog.
Give this a try.

http://www1.mscdirect.com/CGI/NNPDFF?PM ... T4TP=*LTIP

10-32 x 3/4" Unbrakos are $20.75 per 100. Even cheaper than I thought. I think I'll buy a box!!

Good luck,
Scott


by Bob Towarnicki » Thu Dec 30, 2010 6:55 pm
Grainger sells Unbrako 10-32 5/8" length.
http://www.grainger.com/Grainger/UNBRAK ... Pid=search
Bob


ted johnson » Thu Dec 30, 2010 7:43 pm
Thanks for the two sources, guys. I added them to my "resources" wordfile. I've used Grainger many times in the past, even in the Lab's satellites and ground equipment. I noticed Grainger is a tiny bit cheaper than MSC, though shipping costs may make up the difference. I will continue using the spline-head screws for Mac rod screws, but Unbrako is great for ordinary use. TJ

Scott Kneisel » Thu Dec 30, 2010 7:54 pm
There are several ways to look at it but you can never go wrong using the 101 spline screws, maybe the $4ea price is worth the insurance against bolt breakage and I have heard that some builders use the spline bolts more than once and have not had a problem.

It is kind of funny, back in the day my dad and I re-used the rod bolts over and over and never had one break. We just didn't know any better. Maybe we were lucky.

A lot has changed in this time. Rod bolts are a real problem. Bolts we thought were good have caused a lot of engine failures. I started using only the Special rod bolts from US Motorpower (West Bend) but the price has become ridiculous. Everyone is basically out of genuine OEM bolts. Several of us are trying to have a special bolt made but the process is taking forever to try to get a bolt that is correct and cost effective. Beware of what you use. The problems are real.

FWIW, Unbrako used to be a tradename of Standard Pressed Steel (SPS), but now it's an Indian company.  That's not to say the bolts will, or won't, work in a given application.

From the Unbrako website: "Unbrako was acquired by the Deepak Fasteners Group in 2008 and has since grown multi-fold with new warehouse facilities in Birmigham (UK), Los Angeles (USA) and Brisbane (Australia). Further a $100 million has been made in the new state-of-the-art manufacturing plant in Bhopal."

...and Jaguar is owned by Tata of India... and Volvo (automobiles) owned by the Chinese... and the new Buick Envision is entirely made in China... etc.

I have been using the Holo Kromes for years with no failures.Still made in the USA I think. Bought a box of 100 but I'm running low.

first i think on us820's you need to use nothing but the best bolt available .
on us820's con rod failures are historically the biggest issue with them.
using the better bolt sold by dave while expensive is still cheaper than a new motor.


no slam against india but i'll be using holochrome with this new information.
the casual attitude companies outside the usa about maintaining specs concerns me.

on their usefulness we've had nearly 8 years of testing at this point so a post update would be nice.
i'd love to see Scott update this post with his current experience.
if he doesn't jump in soon i may just bug him with a phone call and ask him to comment!!

finally,
in my experience unless you're building crazy stressed mccullochs the holochrome was working reliably on the standard motors.
using a torque wrench and not over torquing the bolts is critical.
also tossing the bolts after single use is prudent.
while they are being pulled super hard at 85-90 inch pounds they have the possibility of being stretched.
to me re-using a fifty cent bolt that might be compromised is beyond foolish.

Blew 2 perfectly good 91 to pieces with HoloKromes. rod caps were the broken part with the broken rod bolts still in the rods. The west bend rod problem (the stock bolt is junk) was the rod itself. If one would take the time to look at the rod information I posted on here, On YouTube and our facebook page (Welte racing) I point out the weak points of the rod. the one rod i hadn't seen was the one used in the Engines from the US 820 kart series. After buying up a box of these engines that were blown to bits I see that the particular rod had the slopped shoulder much like the new rod has but has a lower cap that is very weak right next to the rod bolt. Yep, that is exactly where the blown US 820 kart rods were broken. Put the best bolt in the world in one of those old rods and you still got a ticking time bomb. My 2 cents is that all those 180K bolts are never going in my engines. It is far cheaper to use the best bolt than to sacrifice a complete engine to bolts selected out of a box of 100 you paid $12.00 for.

Hooray, Steve!. My take is: If you have a junk engine you don't care anything about, use the lesser bolt and save yourself a few bucks. If you have a good block you've spent time and money on to make it an engine you want to keep, spend the bucks and buy the good bolts from US Motor Power, Dave Bonbright or one of US Motor's dealers. Also, Bender guys: buy the latest rod from US Motor Power or one of their reps. Mac guys, use the '91 rod in your 6" engines. I've pointed it out before: It's a REUSABLE insurance policy. You may still break a bad rod, but it won't be because of bolt failure. Haven't we said enough on this subject? TJ

Good advice guys! I should have noted that all the engines I used the Holo Kromes in were Mac 91's not turning over 12500.

great thread lotta good info.
steve w,
if i may,without annoying you, ask for a little a little more info.
it would be awesome.
what torque did you use on the rod bolts that broke?
and was it an open motor, or over bored, or run up way into high revs?
the more info we have the better we can understand what happens and why.

i know for most of my motors in the mc91 class running them under 12500 is a good idea i don't always follow.
i myself have only run those bolts in the smaller mc49 motor that i built from parts.
it's a loaner on a loaner kart and has held up good.
but i doubt it gets spun up very high unless the owner himself is driving it.  

there was some discussion about producing new rod bolts ourselves but that fizzled out.
if possible maybe buying a few pounds of the good bolts directly from us motors might be an option??

i'd be happy to create a buying pool here on the forum if they'd sell at a decent price point.
i doubt anyone needs a few thousand but i'd be happy with fifty or so if i could get them at around ten bucks a pair.
to get it that low we'd have to buy a BIG pile and that would get pricey i think.
i'm thinking we could do like car clubs and get a better bulk price by pooling our money.
typically those in the pool get a deeply discounted price and the extras are sold off at market value.

there would be no need to actually collect any money till we get enough people to commit to purchase and an agreement from us motors for a bulk purchase.

or who knows what rod bolts are being used in the new repop mc91 rods and what is the spec on them?

there is a guy working with arp right now
im waiting on an update
tk