Author Topic: Cobra motor disassembly and rebuild  (Read 107643 times)

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Offline BPellerine

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Re: Cobra motor disassembly and rebuild
« Reply #75 on: December 18, 2015, 09:55:34 AM »
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
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Cobra motor disassembly and rebuild
« Reply #76 on: December 18, 2015, 03:01:58 PM »
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  ;D
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #77 on: December 18, 2015, 03:10:51 PM »
We going big!  ;D Gotta calculate 73mm bore x 70mm stroke hmmm. 8),Bill ::)
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Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #78 on: December 18, 2015, 03:24:22 PM »
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  ;D


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.

Offline gschuld

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Re: Cobra motor disassembly and rebuild
« Reply #79 on: December 18, 2015, 03:42:08 PM »
We going big!  ;D Gotta calculate 73mm bore x 70mm stroke hmmm. 8),Bill ::)

That would be 1172cc Mr. Bling 8)

George

Offline johno

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Re: Cobra motor disassembly and rebuild
« Reply #80 on: December 18, 2015, 03:43:19 PM »
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.
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Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #81 on: December 18, 2015, 05:01:59 PM »
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.
« Last Edit: December 18, 2015, 05:08:06 PM by Bill/BentON Racing »
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Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #82 on: December 18, 2015, 05:11:03 PM »
Was that crankcases full of water at some point???

Offline gschuld

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Re: Cobra motor disassembly and rebuild
« Reply #83 on: December 18, 2015, 05:17:08 PM »
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. :o

George


Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #84 on: December 18, 2015, 05:29:16 PM »
Last night! ;D Old cases were clearanced just not quite enough! Time for the steel's. Case is not finished clean ;D, yet, but working clean. Bill
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Offline BPellerine

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Re: Cobra motor disassembly and rebuild
« Reply #85 on: December 18, 2015, 05:37:14 PM »
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
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Offline gschuld

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Re: Cobra motor disassembly and rebuild
« Reply #86 on: December 18, 2015, 05:43:52 PM »
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

Offline BPellerine

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Re: Cobra motor disassembly and rebuild
« Reply #87 on: December 18, 2015, 05:47:49 PM »
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
« Last Edit: December 18, 2015, 05:55:13 PM by BPellerine »
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Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #88 on: December 18, 2015, 06:21:58 PM »
First set small end bushings a little scarred. These are nice.
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Offline scottly

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Re: Cobra motor disassembly and rebuild
« Reply #89 on: December 18, 2015, 06:42:39 PM »
Drum roll, don't ask me how.  F me silly. It was the cut off head of a tie wrap...smh!  >:( ::) ;D, Bill
Do you mean the plastic bit damaged the combustion chamber, or was the damage from a prior incident?
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Offline hotdog

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Re: Cobra motor disassembly and rebuild
« Reply #90 on: December 18, 2015, 06:46:55 PM »
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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« Last Edit: December 18, 2015, 06:48:39 PM by hotdog »
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Offline 754

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Re: Cobra motor disassembly and rebuild
« Reply #91 on: December 18, 2015, 07:44:51 PM »
I doubt it, they are a stouter casting.. The rods shown above are modified stockers..
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Offline gschuld

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Re: Cobra motor disassembly and rebuild
« Reply #92 on: December 18, 2015, 08:02:30 PM »
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
« Last Edit: December 18, 2015, 08:14:19 PM by gschuld »

Offline gschuld

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Re: Cobra motor disassembly and rebuild
« Reply #93 on: December 18, 2015, 08:25:52 PM »
For reference, RC catalog, 1978

George

Offline MRieck

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Re: Cobra motor disassembly and rebuild
« Reply #94 on: December 19, 2015, 06:22:08 AM »
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
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Offline Medyo Bastos

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Re: Cobra motor disassembly and rebuild
« Reply #95 on: December 19, 2015, 06:58:31 AM »
i have a nos set of rc super rods  ;D

Offline gschuld

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Re: Cobra motor disassembly and rebuild
« Reply #96 on: December 19, 2015, 08:50:08 AM »
Did you get them from Billy, who got them from me a while back?

George

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Cobra motor disassembly and rebuild
« Reply #97 on: December 19, 2015, 09:06:15 AM »
I have a 'set' of less than excellent RC rods in the basement too
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Medyo Bastos

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Re: Cobra motor disassembly and rebuild
« Reply #98 on: December 19, 2015, 09:07:11 AM »
Did you get them from Billy, who got them from me a while back?

George

no, this is stuff i keep under the bed

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #99 on: December 19, 2015, 10:25:42 AM »
The good stuff, yeh, send em , we'd be even!! Lol, , Bill
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