Topic: Cobra motor disassembly and rebuild

[BPellerine]

Centre popping the rod numbers on two halves is bad practice, if you decide to do it the rods must be resized after, if you find a set of rods done like that carefully check the big end for roundness with the rods torqued up to spec to make sure the person resized round again.

my rc rods like bills appear to have been ground on the big end,original rods were 3 green and one brown,the rc rods plastigauged to all green,shells marked std were found in the rc rods.bill

[Jerry Rxman Griffin aka MuthaF'er]

Go big or stay at home!!! Screw a 10 second ticket, put the striker crank in there and run some 9's.

Just do it!! Oh, but put new bearings on the rods first. You'll be pulling the bottom end apart a lot for maintenance so at least start with a fresh set to begin with.

Why don't you throw some fuel on the fire Frank 

[Bill/BentON Racing]

We going big!  Gotta calculate 73mm bore x 70mm stroke hmmm. ,Bill

[dragracer]

Go big or stay at home!!! Screw a 10 second ticket, put the striker crank in there and run some 9's.

Just do it!! Oh, but put new bearings on the rods first. You'll be pulling the bottom end apart a lot for maintenance so at least start with a fresh set to begin with.

Why don't you throw some fuel on the fire Frank 

Jerry, you know I don't  miss an opportunity to stir the pot. This time Benton will have a few months to get it together, make some test passes and be ready for setting a new record in super eliminator. Its low hanging fruit right now for anyone to pick. Y'all better go after it at the first race. It won't be so easy by the Memphis race.

[gschuld]

We going big!  Gotta calculate 73mm bore x 70mm stroke hmmm. ,Bill

That would be 1172cc Mr. Bling

George

[johno]

Centre popping the rod numbers on two halves is bad practice, if you decide to do it the rods must be resized after, if you find a set of rods done like that carefully check the big end for roundness with the rods torqued up to spec to make sure the person resized round again.

my rc rods like bills appear to have been ground on the big end,original rods were 3 green and one brown,the rc rods plastigauged to all green,shells marked std were found in the rc rods.bill

Bill P 
All honda std rods prepped by RC ( or contractor) ie larger bolts , crack tested , peened, small end bushed etc etc the big ends were always resized to std diam and zero out of round.   They were a good option in those days, as I remember it was them or alloy rods !
Alloy rods went higher RPM but didnt last as long , the steel rods couldnt do as high RPM but lasted longer kinda of thing.
The modern steel rods like Carillo and falicon  are a lot lot better than the old prepped steel rods, its all about the surface area of the parting line and the bolts which prevent the big end from going out of round at high RPM and effecting the oil clearance.

We have a couple of forum members who have been testing the boundaries of stock rods and been getting away with it , Dennis LSR bike is one, pewe I think is the other in europe with his top end and big dyno RPM.   Certainly the weight of the pistons contribute to what is reliable, a nice 900 piston is about the same weight as a std 750 piston but I guess when you run big boy pistons the weights increase and start to stretch the rod and reliability factor on the std honda rods.   Big ARP bolts like RC use are good and would help the cause though.
cheers johno

[Bill/BentON Racing]

Yah, going with a new set of bolts, bearings, and the best 4 rods...no matter what number! Lol. I only meant to say usally with RC rods they etc put them on originally on the same numbered rod journal. Here's another example...1 is on 1,2 on 2 etc.

[dragracer]

Was that crankcases full of water at some point???

[gschuld]

Frankie has also been doing an unofficial long term durability(torture) test on RC prepped big bolt factory rods. To really give them a solid test, he has been running them on 72mm high compression 1970s MTC pistons.  I have a set of identical pistons on the shelf and they weigh 246 grams bare!  Add 43 grams for the pin and 23 grams for each set of rings, you get 312 grams per piston yanking on those rods at 10,000-10,500rpm shift points in a ported f head, big bore, mid 10s all day long drag motor  Now that is a LOT of pressure on a set of modified factory rods, or ANY rods.  Pretty much a worst case scenario for our old N/A sohc motors.

I don't know if that should be seen as a solid endorsement to the durability RC(and others)managed to put into those factory rods (with the shot peening, heat treating, bushing, and big rod bolts) or a testament to Frankie's ability to beat the odds.

And we're not talking a season or two, I think those same rods and ancient super heavy pistons have been raced for MANY seasons(with regular tear downs and freshening, bearings and rings).

So no concrete and reliable conclusions can be drawn from this, but it sure is an interesting data point.

George

[Bill/BentON Racing]

Last night! Old cases were clearanced just not quite enough! Time for the steel's. Case is not finished clean , yet, but working clean. Bill

[BPellerine]

thanks johno and George,I did not really pick these rods,they kind of picked me,ie good deal,and yes the modern stuff is better,but no denying dragracers success with them,they are  in a henry abe 890 engine for the street,that I am building so not the lightest pistons but not high compression ,most likely will never see racing rpms,plus they are cool!!billp

[gschuld]

My guess is that if they are the full RC super rods(big rod bolts and bushed small ends), they have no defects or signs of previous damage, they should hold up to anything your mid level 890 engine can throw at them.

George

[BPellerine]

My guess is that if they are the full RC super rods(big rod bolts and bushed small ends), they have no defects or signs of previous damage, they should hold up to anything your mid level 890 engine can throw at them.

George

yeah they are big bolt and bushed,very nice condition.bill

[Bill/BentON Racing]

First set small end bushings a little scarred. These are nice.

[scottly]

Drum roll, don't ask me how.  F me silly. It was the cut off head of a tie wrap...smh!  , Bill

Do you mean the plastic bit damaged the combustion chamber, or was the damage from a prior incident?

[hotdog]

My guess is that if they are the full RC super rods(big rod bolts and bushed small ends), they have no defects or signs of previous damage, they should hold up to anything your mid level 890 engine can throw at them.

George

yeah they are big bolt and bushed,very nice condition.bill

Just butting in for a second here - are these rc rods what Cyclex super rods are based on. ?

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[754]

I doubt it, they are a stouter casting.. The rods shown above are modified stockers..

[gschuld]

Yes, that's my understanding.  It's more likely that the Cycle X super rods were copies of something like the 70s Action Fours rods.

Action Fours had steel rods made, looked just like the factory rods, but we're beefier all around.  Weighted a bit more as well.  Certainly not the top end choice like Carrillos, but certainly stronger than stock I'd think.

George

[gschuld]

For reference, RC catalog, 1978

George

[MRieck]

Yes, that's my understanding.  It's more likely that the Cycle X super rods were copies of something like the 70s Action Fours rods.

Action Fours had steel rods made, looked just like the factory rods, but we're beefier all around.  Weighted a bit more as well.  Certainly not the top end choice like Carrillos, but certainly stronger than stock I'd think.

George

I rebuilt a 750 engine with the Action 4 rods. The engine had spun a bearing which ruined 1 rod.....so much for the set.

[Medyo Bastos]

i have a nos set of rc super rods 

[gschuld]

Did you get them from Billy, who got them from me a while back?

George

[Jerry Rxman Griffin aka MuthaF'er]

I have a 'set' of less than excellent RC rods in the basement too

[Medyo Bastos]

Did you get them from Billy, who got them from me a while back?

George

no, this is stuff i keep under the bed

[Bill/BentON Racing]

The good stuff, yeh, send em , we'd be even!! Lol, , Bill