Topic: RC Connecting Rods VS. Carrillo

[754]

Well they certainly should not  have the problems of old forged aluminum rods..
 They are fat though.. not sure of weight..

[gschuld]

Mike, maybe the rods were polished for show in the catalog.  But the 3-4 sets I’ve had in my hands over the years, none were smoothed or polished.  Dunno…

Everyone else:  IMHO, the golden rods aren’t necessary shelf art.  Plenty are still running around today.  Having said that, aluminum rods carry their own risks as aluminum fundamentally fatigues more rapidly than steel rods.  And often enough, used RC golden rods are out of spec and no longer realistically serviceable.  This is likely more the result of having a rough life, being raced to death, surviving a few minor oil starvation events, blown pistons, who knows.

I’ve spoken to the lead engineer at Bill Miller Engineering…

http://www.bmeltd.com/rods.htm

…about our RC Golden rods.  I showed him the specs, usage, etc.

His general take on them overall.  They were designed for 1000cc plus supercharger/turbo/nitrous/Nitromethane (take your pick or combination) fed drag racing use.  We are talking 250hp engine output here.  He said at that power level, you will likely see the rods weaken in time from the sheer stress and loads being fairly close to their designed limit.  But at N/A power levels, even racing N/A power levels, the loads are under half the designed loads.  The rod bolts that can handle 250hp aren’t even functionally stressed at half that.  So in his opinion, RC Golden rods, if NOS or damn near perfect, should have a LONG service life in about any street or racing engine as long as they are assembled correctly, bearings sized right, and the engine gets plenty of quality oil(like all rods need)

The Sorcerer ran two engines with a blower force feeding both of them with a heavy Nitro diet.  Reportedly around 500hp total.

At 500hp across 8 cylinders, that’s 62.5hp per cylinder(rod).  A rip snorting 13:1 compression, ported to the limit, giant cammed 1000cc N/A race engine will produce around 125hp.  That’s 31.25hp per cylinder.  Exactly half the HP/rod it was intended to successfully handle.

A top level STREET gas 1000cc engine(MRieck) is producing around 105hp, or 26.25hp per cylinder.

The Engineer wasn’t even thinking the rod would stretch any amount worth worrying about at such a low HP/rod level compared to what it was designed to handle.  We discussed ideal fresh rod bolts, which none exist that I could find off the shelf.  ARP sells flanged 12 point bolts identical in dimensions other than the flanges are slightly too wide.  A careful flange trimming on the lathe and they work great(these trimmed ARP bolts went into the Triple engines and Sorcerer engines).

All that said, one never knows what kind of life a set of RC Golden Rods had(often a hard life), unless of course it’s an NOS set.  Before using ANY used set of Golden rods, I’d have a real pro (Mike?) examine them and give his stamp of approval before going ahead.  IMHO, never buy a used set of goldens without being OK with them being designed shelf art if they don’t measure up (and I have the shelf art to prove it🙂). No one will see the bling once the engine is closed up anyway😎

Golden rod weight:
286 grams no bearing shells
318 grams with bearing shells

George

[newday777]

Thanks George
I'll have Mike check the RC rods out. The friend that had them is Kurt Jordan (Jordan Engineering). He has been a long time race engine builder and worked for Action Fours in the 70s. I've known him for several years and is a wealth of information and highly reputable engine builder. He answered my question on their condition before buying them as being good so we'll see when Mike looks them over. They are due here today.

[PeWe]

Those rods can be OK for 836-900cc, but not 1000cc?
CycleX super rods an alternative too. Rather heavy though.

If RC Golden rods are up in the rod comparison:

I read somewhere that alu rods have a built-in dampening shock absorbing effect, good for hard pounding nitro engines.
Must apply less stress on wrist pins too.
I searched again and found similar info.
https://www.dragzine.com/tech-stories/five-things-you-need-to-know-about-aluminum-connecting-rods/

Wrist pin offset
A coincidence that I talked to my local tuner yesterday when we compared 2 pistons,  forged JE, 70 vs 71.25mm. (both stamped "71M" inside). The latter with wristpin displaced just a little.
Must also make less stress when banging hard from above, piston will tilt a little. Less noise and vibrations.
I joked that pinging will sound less.
https://blog.wiseco.com/what-is-wrist-pin-offset

Yoshimura stated in an old article that stock rods cope with 836 and max 8000rpm.

Different if racing at a constant high rpm or street where you might shift at + 9000rpm now and then followed by cruising at 6000-7000 rpm. Very hard engine braking must stress too.

Higher compression will punch the rods more.

My K6 836cc ran fine for years on stock rods, often shifted gear at 9000 rpm. About 80whp. Compression rather modest when I ran it as hardest.

That crank with rods sit in my K2 where I often shift at +8000 rpm. 58whp on dyno, runs better now with Dyna-S.

I did not use the F2 crank bolts and nuts I purchased some years ago.

1000cc build must torture the rods more when it is very fun with more displacement and less need to gear down.
Just cruise on 5th gear and twist.
My almost stock K2 need more work with the shifter pedal when passing cars, 1 and mostly 2 steps down.

RC295 profile will give your build better power. My 1000cc ran with DP315 for a few years. Changed to RC295 profile and got much more, from bottom to top.

Latest setup with Megacycle 125-75 that gave a nice even torque all the way up from low.  101whp on dyno.
Might have given more if I had focused on the squish area, pistons outer flat ring vs head. 1.25mm, 1.0mm with thinner base gasket should have kicked the graphs in correct direction.

I should not run this engine with weak rods.
The additional cost for a set of Carillos is small compared to what a broken rod will do with the engine,  risk for my life and the entire bike. It is an insurance.

But it is possible to damage a Carillo rod.
One guy I know dropped a valve in his CB750 vintage racer and did not shut off direct when engine started to sound bad.
Cam tower came  loose.
- Replaced cam,
- Restore head welding chamber, new seat, new guides, valves for that cylinder  (5mm stem version)
- New JE 62mm piston and sleeve.
- Replaced crank and 1 Carillo rod.

Cases OK what I know.

[754]

Geez i must have made 500 pasees in 1/8 mile with stock rods in 836 cc.. shifting at 10 or 11 K always..

 Long rods from 900 with  spacer, in our 750s.. its been done right ?
 My buddy did it to a big bore stroked XL 350  and it increased hp and torque,  but went to longer rod.....makes more power than his CR 450... over 50 hp at rear wheel..

[Don R]

 I have a set of MTC steel rods that have pistons but they need to come off. I can add a pic of those if anyone is interested. It appears the APE and CycleX steel rods are out of stock these days.
 My Hot Rod 836 also has a set of steel RC engineering rods in it, but I don't want to take it apart until I have parts to rebuild it. Not sure if it has the big rod bolts or not.

[newday777]

Thanks for posting that Don, it gave me a chance to re-read all the replies this thread in my early morning awake time.
As an update, I still haven't had time to get down to see Mike with the RC rods for his looking them over for verification to Kurt's telling me before purchasing them that they were within spec and look good. If good, I'll probably get better rod bolts with 12 pt nuts fitted to them to replace the stock size bolts and 6 pt nuts they came with from RC as per the RC catalog pictures the George posted.

Back in the summer of 77, I had my K6 built by a friend who I worked with at the Honda shop who built race engines, with an 811 Yoshi kit, Action Fours 3/4 race cam and valve springs(IDR which number cam now), ported the head, and we used the stock rods, I even kept the stock rods when I had it rebored to an 836 17,000 miles later. I regularly ran it up into the 9,000 rpm range on the street and sometimes to 10,000. When I sold that bike in 1983 at 45,000 miles there were some bottom end noises to it, it had a hard life on the street going cross country 5 trips, with lots of wrist action wheelies the last 30,000 miles fully loaded in which I broke a number of spokes on the 16" hog wheel so I know from experience the stock rods hold up well to a built 836 motor, rode hard and put away wet.

When I started this thread a bit over a year ago I was thinking about building an 849-900cc motor until I met Mike a week later and he showed me his billet block motor, I was drooling 🤤. I haven't gone much further in the build yet as the money didn't come in last winter to do a build, then this past spring I was offered 6 project 750 carcasses by a friend as he was getting ready to move to California for work, so I had to enlarge my rented 10'x11' storage room into a 11'×36' shop in my friend's barn, all while working to pay the bills. Now winter is settling in again and I'm looking for a pellet stove to help fight off the deep freeze that will be here in NH shortly. I did get some 4" foam sheets to insulate the walls a couple weeks ago and got them up this past week.
I have been helping another friend that has dementia coming on the past week to start clearing out his garage and yard of tools and good lumber he's collected as they are moving south shortly to live near his son. We filled one dumpster already of unworthy stuff, sorted out scrap metal to be hauled away separately. Still more to do on this clean out for the next couple weeks. I've gotten some good tools and 12 new LED shop lights along with a bunch of lumber. I even found a long lost elusive 10mm socket on his garage floor. 
Life keeps getting in the way of having fun on the bike projects but It's all good.

One of the motors I got this spring in the package of projects is an 836 K5, that had been in a chopper my friend had bought but didn't know anything about it's condition, so I need to open it up and inspect it, hopefully this winter. I did peek in the ports and saw it's intakes have been polished and it has a SS2 cam, better springs and titanium keepers. Hopefully I'll have a warm shop and a bit of time this winter to open it up fully and get it running again (and painted) for spring in one of the project bikes.

I really appreciate all the input that has been given here by all who have taken the time to write in to answer my questions. Thank you. 😊

[Don R]

 I remember them talking about small block ford rod bolts way back when. It seems like modifications were required. These MTC's were in the turbo bike, the 836 has the RC steel rods.  These were the drag bikes I bought last year.

[newday777]

I remember them talking about small block ford rod bolts way back when. It seems like modifications were required. These MTC's were in the turbo bike, the 836 has the RC steel rods.  These were the drag bikes I bought last year.

Now that you mentioned it, I remember reading about the SB Ford rod bolts being a modification.

I take it that those MTC pistons(picture w/MTC rods) are bigger than the 836 with RC steel rods.

[dragracer]

26 years later and the RC rods are still inside this engine. Lots of full throttle passes down the 660 and 1320. It's been rebuilt many times and I've never replaced the original rod bolts or nuts.

[newday777]

26 years later and the RC rods are still inside this engine. Lots of full throttle passes down the 660 and 1320. It's been rebuilt many times and I've never replaced the original rod bolts or nuts.

1078(6 point nuts)or 1081(12 pt nuts) rods?

[dragracer]

26 years later and the RC rods are still inside this engine. Lots of full throttle passes down the 660 and 1320. It's been rebuilt many times and I've never replaced the original rod bolts or nuts.

1078(6 point nuts)or 1081(12 pt nuts) rods?

12 pt.

[newday777]

26 years later and the RC rods are still inside this engine. Lots of full throttle passes down the 660 and 1320. It's been rebuilt many times and I've never replaced the original rod bolts or nuts.

1078(6 point nuts)or 1081(12 pt nuts) rods?

12 pt.

Thanks  for your input

[Don R]

Those rods and pistons were in an 836 also, if I could get the rings out of the grooves they would go back in. The PO raced it a lot for many years on the strip and street until he got a Hayabusa. These look heavy but are apparently worth any weight penalty. 
 He did stick a stock rod through the top of the case once on the turbo motor, I also got a melted 812 piston in the parts, totes so he did lean on it. As long as neither end is blue or rusty, I'd feel pretty safe with a good set of any of the aftermarket steel rods.

[gschuld]

Ok, this should be cleared up.

First image is a KO OEM rod on the left with 7mm OEM rod bolts, and on the right is the RC modified OEM  rods with the 12pt 11/32” bolts.  The rod obviously required machining to install the MUCH bigger bolts.

The second pic is OEM 750 DOHC rods with their OEM 8mm rod bolts compared to the same RC rods from the first pic with the 11/32” bolts (8.84mm).

The 7mm rod bolts are quite tiny.  FWIW, even the KZ750 4 cyl ran 8mm rod bolts.

[newday777]

I like 👍 those comparative photos and explanation.  Thanks again George

[RAFster122s]

Tip for those in cold climates. Get a sheet of 1 inch white styrofoam sheet and glue a sheet of cardboard to the top and bottom for durability. If you stand on it when working in an unheated concrete floor in winter the ground will not suck the heat from your feet and you will feel and be much warmer as a result.

[newday777]

I just watched this video on comparing Steel vs Aluminum vs Titanium vs Carbon Fiber rods.
Interesting 👀

[grcamna2]

subscribed

[bubbafun101]

If Mike is doing parts of your HiPro engine I would use whatever he recommends especially if u go the 1000 cc route.  Lots of potential conflicts mixing and matching parts and Mike has seen it all. Good luck

[newday777]

If Mike is doing parts of your HiPro engine I would use whatever he recommends especially if u go the 1000 cc route.  Lots of potential conflicts mixing and matching parts and Mike has seen it all. Good luck

Yes indeed, but if there aren't any billet blocks I'll probably be at 849cc to 900cc.

[PeWe]

If Mike is doing parts of your HiPro engine I would use whatever he recommends especially if u go the 1000 cc route.  Lots of potential conflicts mixing and matching parts and Mike has seen it all. Good luck

Yes indeed, but if there aren't any billet blocks I'll probably be at 849cc to 900cc.

970cc work fine too
CycleX has rather low priced sleeves. OD 74.5mm, ID 69mm.

Only 0.3 mm thicker (cylinder area) than their stepped sleeves for 836-900cc.
OD 74.2mm, ID 64mm.
Depending on your top case, it might need som grinding.

74.5 mm all the way need top case machining.

Then find a set of 70mm pistons. I was lucky to get a set of older never ran JE 12.5:1 pistons that could be milled to fit cylinder and chamber. 
Flat top type of piston made that possible.

Important that the bore guy mill a wider lower part for oil seal between sleeve and cylinder with a very tight sitting o-ring covered with sealer.
I think I used 65x1.5mm o-rings into 74.5x1.25 mm grooves.

 I used Hondabond type.
1.25 mm wide groove, ca 5mm deep.
Another cylinder I have (890cc) has Wurth Super RTV only. I'll see if that will due or if I should place an o-ring at the bottom first

[Jerry Rxman Griffin aka MuthaF'er]

EXCELLENT video Newday. Thank you.

[Don R]

 I've lost the picture taken through the bottom of the engine, but I saw it last week and the RC rods in my RC836 bike have the 12 point bolts. I'm kind of disappointed that they are modified stock rods though.

[MRieck]

If Mike is doing parts of your HiPro engine I would use whatever he recommends especially if u go the 1000 cc route.  Lots of potential conflicts mixing and matching parts and Mike has seen it all. Good luck

Yes indeed, but if there aren't any billet blocks I'll probably be at 849cc to 900cc.

You want to go 900cc Stu.....it really makes a big difference.