Author Topic: Rod bolt balance pads  (Read 614 times)

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Offline pcunder

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Rod bolt balance pads
« on: November 18, 2019, 11:31:31 am »
Im building a factory spec 69 B2 motor & thinking about using the best ARP bolts in the OEM rods but was wondering if OEM C3AE rods become unusble after the balance pads on the caps are ground down so far...

Comments, opinions, wisdom?...

Thanks guys.

Phil

66 Mustang-A  Emberglo GT Fastback 4-spd, AC, C8AM, 9", Konis
69 Mustang-G  Blue Shelby tribute, modified, 3.50-TL/CR, resto
70 Mustang-G  Lime Metallic, #2 owner, 3.50/WR, Paxton, repaint
D1ZE block, steel 289 crank, TA rods, Clevor top; need Ford car

Offline gt350hr

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Re: Rod bolt balance pads
« Reply #1 on: November 18, 2019, 03:37:14 pm »
    Phil,
       "I" feel the Ford bolts are fine but the Ford rod nuts aren't fine. I replaced the nuts only for 40+ years and never had a bolt failure. I just spent a few days talking with a former Ford engineer that had test reports from Boss 302 warranty claims ( from back in the day). Besides the well known piston skirt issue there was a serious problem with poor heat treat on assembly line rod nuts. ARP or Mr Gasket rod nuts solve the problem
    As far as balancing rods, it should be done by "grooving the pad rather than "flat grinding" it. If you have rods flat groun , they have lost critical strength needed to keep the big end round.
     Randy
« Last Edit: November 19, 2019, 09:14:23 am by gt350hr »
'66 GT350H (6S477)1of 18 white w/blue side stripes - drag raced mostly w / Boss 302 power for 35+ years
68.5 Cobra Jet fb  white w/blue c stripe 4spd
sorry never owned a Boss car just engines
cover Car Craft July '77 with my Boss powered GT350
cover/article Mustang Illustrated Fall 1987 w/all aluminum SK 351 Cleveland powered Mustang II
cover /article Modified Mustangs Feb 2011
cover Mustang Monthly  June 2014

Offline TACoupe

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Re: Rod bolt balance pads
« Reply #2 on: November 18, 2019, 05:05:58 pm »
If you want to change them consider using ARP wave loc Rod bolts.

https://www.summitracing.com/parts/arp-150-6404/

   Roy

Offline Bossssssss

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Re: Rod bolt balance pads
« Reply #3 on: November 18, 2019, 06:47:19 pm »
....and if you do use the ARP bolts (150-6004 or 250-6404) then you need to make sure the rod bolt hole has a chamfer of .040" as both of these part numbers have a .030"-.035" radius on them regarding the fillet under the head. 

Offline scotts216

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Re: Rod bolt balance pads
« Reply #4 on: November 19, 2019, 07:59:38 am »
My engine is out and I was just about to make a post on this very topic...... Any part numbers or sources for the nut only??? Although the ARP bolt/nut complete set seems cheap enough just to replace all. Interesting that I noticed that my rods had been balanced by "grooving" as Randy said.....

Offline JohnSlack

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Re: Rod bolt balance pads
« Reply #5 on: November 19, 2019, 09:15:52 am »
The correct way to remove weight from the rod cap is to use a radius end mill that doesn't take up more than 50% of the width of the balance pad. The depth of the balance pad correction also has limits. These limits sometimes create what is technically an unbalancable set of rods. I have seen rods where in order to remove weight the caps have been sanded down to a ridiculously thin thickness. I have seen rods where the sanded areas are blue from the heat. I have seen rods where extra weight was removed by too much sanding on the rod bolt "side casting area". These are all signs of a not good balance job. The balance of the engine may be right on, however...at what material cost?
John
Have you driven a Ford Lately?

https://youtu.be/C2fY6-Ggfoo


2010 Mustang GT Red Candy Metallic
1970 BOSS 302 Mustang Lime Green Metallic
1969 1/2  BOSS 302 Mustang Calypso Coral
1962 Porsche 356B-T6 Silver-Black interior (It's a Porsche that is what they should be.)

Offline gt350hr

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Re: Rod bolt balance pads
« Reply #6 on: November 19, 2019, 09:27:40 am »
    "Grooving" as I described it retains the ribbed portion of the cap which is where the strength comes from.

    As Bossssssss mentioned , wave lock bolts REQUIRE heavy chamfers on the rod and cap as the rod bolt "moves" material as it presses into the rod. Ford found this out the hard way with rod failures when the wave lock bolts were used on 460 truck rods on the initial 521 stroker 460s. AER did the engines and the rod caps would not fully seat after bolt replacement. This resulted in many failures from spun bearings despite proper torque values on the rod nuts. Ford solved the issue by going to a capscrew rod to save face when it was a simple installation problem they didn't want to admit.
    Randy
'66 GT350H (6S477)1of 18 white w/blue side stripes - drag raced mostly w / Boss 302 power for 35+ years
68.5 Cobra Jet fb  white w/blue c stripe 4spd
sorry never owned a Boss car just engines
cover Car Craft July '77 with my Boss powered GT350
cover/article Mustang Illustrated Fall 1987 w/all aluminum SK 351 Cleveland powered Mustang II
cover /article Modified Mustangs Feb 2011
cover Mustang Monthly  June 2014

Offline pbf777

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Re: Rod bolt balance pads
« Reply #7 on: November 19, 2019, 10:39:22 am »
     
.................the ARP bolt/nut complete set seems cheap enough just to replace all.

     As Randy stated, it was/is frequently practiced to replace the rod nuts at each engine renew, if all else appeared good.  But today, with so many different fastener manufactures available, I would be hesitant in mixing products, as concerning the truly accurate tolerance and compatibility of the threading, as no one in the position of knowing stated that the tread dimensions of two different manufactures were properly compatible.      ???

     As an example, we received a Ford Racing block that accepted the O.E.M. threaded fasteners, but would not other fasteners tried?    :o    In discussions with F.R., apparently they established that someone in production had utilized the wrong tooling in the treading operation.    OOPS!        ::)          And just running a tap into the already worked hole to make the new fastener screw-in, doesn't mean the newly created tread engagement will be proper.       ;)

     
    the rod bolt "moves" material as it presses into the rod. Ford found this out the hard way
    Randy

     Typically, the rod bolt bores are not accurate enough in sizing or surface to permit the proper utilization of the "Wave-Loc" shank profile, and the ability and associated costs to rework a connecting rod not engineered for such originally, and provide a proper bore in reality is not effective, in my opinion.  But of course, I've never been impressed by the serrated bolt shank surface of the "Standard Hi-Performance" product either, which I believe is what they were trying to address with the "Wave-Loc" design.      OOPS!       ::)

     Scott.
 

Offline JohnSlack

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Re: Rod bolt balance pads
« Reply #8 on: November 19, 2019, 11:18:20 am »
Typically I don't know what the history of a set of used factory rods are anymore. This causes me to choose a set of aftermarket rods, my brand of choice has been Crower rods the last few years. They arrive ready to inspect and use. If anything is out of specification I contact Crower and they are fixed.
John
Have you driven a Ford Lately?

https://youtu.be/C2fY6-Ggfoo


2010 Mustang GT Red Candy Metallic
1970 BOSS 302 Mustang Lime Green Metallic
1969 1/2  BOSS 302 Mustang Calypso Coral
1962 Porsche 356B-T6 Silver-Black interior (It's a Porsche that is what they should be.)

Offline gt350hr

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Re: Rod bolt balance pads
« Reply #9 on: November 19, 2019, 01:20:35 pm »
   Factory Boss rods certainly have a power and rpm limit. Above 7,000 rpm ( repeated use , road race , drag race) the pressed pin becomes a liability. Going to a "floated" modification of the small end eliminates that problem and allows 7,500 to 8,000 rpm use before the big end design is compromised by sheer piston weight. Aftermarket rods solve the problem. Unless you are really racing or have stroker , the stock rod will do the job with a simple nut replacement. Taking a used rod set in and having the bolts replaced and the rods resized plus adding small end bushings is often ( if not always) more expensive than aftermarket NEW rods ( though offshore in origin) that are stronger than the stock rods. Sometimes the decision is tough on which way to go on a "street performance" engine.
   Randy
'66 GT350H (6S477)1of 18 white w/blue side stripes - drag raced mostly w / Boss 302 power for 35+ years
68.5 Cobra Jet fb  white w/blue c stripe 4spd
sorry never owned a Boss car just engines
cover Car Craft July '77 with my Boss powered GT350
cover/article Mustang Illustrated Fall 1987 w/all aluminum SK 351 Cleveland powered Mustang II
cover /article Modified Mustangs Feb 2011
cover Mustang Monthly  June 2014

Offline pcunder

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Re: Rod bolt balance pads
« Reply #10 on: November 19, 2019, 09:16:29 pm »
Wow, all good info. I guess I opened a can of worms.

Since this is just a factory rebuild, I'll likely use them IF the balance pads aren't over-ground. 
I'm not sure how to tell myself and I was hoping to post pics but that's no longer possible...

They already have floated pins and smooth ground beams.

Stupid question: If these rods are already within 1 gram of each other, is it safe to say NO more grinding for balancing purposes needs to be done?

Thanks for the plethora of knowledge and experience.

Phil
66 Mustang-A  Emberglo GT Fastback 4-spd, AC, C8AM, 9", Konis
69 Mustang-G  Blue Shelby tribute, modified, 3.50-TL/CR, resto
70 Mustang-G  Lime Metallic, #2 owner, 3.50/WR, Paxton, repaint
D1ZE block, steel 289 crank, TA rods, Clevor top; need Ford car

Offline gt350hr

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Re: Rod bolt balance pads
« Reply #11 on: November 20, 2019, 08:17:18 am »
   Yes Phil if they are that close , leave them alone. There is no such thing as a "perfect" balance , and it is certainly not necessary . "Most " think it is but an engine is not a wheel and tire that simply rotates. A "perfectly" LOL balanced engine could shake if one cylinder was "weaker" or not firing at all , despite being "balanced" . Pull a plug wire on a running engine and see what I mean.
'66 GT350H (6S477)1of 18 white w/blue side stripes - drag raced mostly w / Boss 302 power for 35+ years
68.5 Cobra Jet fb  white w/blue c stripe 4spd
sorry never owned a Boss car just engines
cover Car Craft July '77 with my Boss powered GT350
cover/article Mustang Illustrated Fall 1987 w/all aluminum SK 351 Cleveland powered Mustang II
cover /article Modified Mustangs Feb 2011
cover Mustang Monthly  June 2014

Offline pbf777

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Re: Rod bolt balance pads
« Reply #12 on: November 20, 2019, 09:48:51 am »
Since this is just a factory rebuild, I'll likely use them IF the balance pads aren't over-ground. 
I'm not sure how to tell myself and I was hoping to post pics but that's no longer possible...

They already have floated pins and smooth ground beams.
Phil

    The proper procedure is to take the rods to a competent machine shop and have them inspected by those who are knowledgeable.  The rods should first be given a cursory inspection, then magnafluxed for cracks, checked for straightness, then the big ends and small ends checked for roundness and size, if all proves "O.K." then they should be re-bolted  and resized, if for no other reason than you don't know of their history. The observations made may decide for you, whether you should reuse them or not.     

     My personnel opinion is to avoid used connecting rods which have been "worked" to the degree you describe, as it would tend to indicate the aggressive intentions of a previous owner, and if you know not of their history, you know not of if all nine lives have already been utilized.      ;) 

   
Stupid question: If these rods are already within 1 gram of each other, is it safe to say NO more grinding for balancing purposes needs to be done?
Phil


     It's nice that the rods would be within one gram, in overall weight, but that still fails to establish the end-weight values.  Generally, when I balance connecting rods, I achieve end weight sum variations of plus or minus one tenth, and hold the overall rod weight to something less than five tenths of a gram.  And yes, such effort is probably needless, as as soon as any other revolving masses are attached, well lets say I haven't witnessed any such effort in the balancing of these units, but at least I'm comfortable in the fact that I did my job anyway,.......... and if it shakes don't look at me!     ::)

     Scott.     

Offline gt350hr

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Re: Rod bolt balance pads
« Reply #13 on: November 20, 2019, 03:02:32 pm »
 it is important to respect the fact that Scott does this "everyday" at his business and has for as long as I can remember. He and his Foxbody drag car "Super Trooper" were legendary until some S.O.B stole it. I don't do it "everyday" but have done it allot over the last 50+ years.
   Randy
'66 GT350H (6S477)1of 18 white w/blue side stripes - drag raced mostly w / Boss 302 power for 35+ years
68.5 Cobra Jet fb  white w/blue c stripe 4spd
sorry never owned a Boss car just engines
cover Car Craft July '77 with my Boss powered GT350
cover/article Mustang Illustrated Fall 1987 w/all aluminum SK 351 Cleveland powered Mustang II
cover /article Modified Mustangs Feb 2011
cover Mustang Monthly  June 2014

Offline pbf777

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Re: Rod bolt balance pads
« Reply #14 on: November 20, 2019, 06:33:06 pm »
   Factory Boss rods certainly have a power and rpm limit. ........................before the big end design is compromised by sheer piston weight.
   Randy

     And this example is why one should not search for, or use the old, yes I know, "period correct", TRW or other relatively inexpensive (over weight!) piston in their intended to be high revving BOSS 302 engine.

     Randy can sell you a set pistons w/ pins not only of better quality but lighter by,.............O.K. Randy, jump in, how much weight (approx.)?; and it would be money well spent for this and a number of other reasons.           ;)

     In a conversation with a bearing manufacturers' engineering representative decades ago, he stated that it was the 351C (probably not enough BOSS 302's to get their attention) that caused them to increase the eccentricity dimensions on their performance rod bearings to sums greater than otherwise practiced at the time, as the otherwise early on excessive bearing failure rates had been concluded to be the result of the excessively heavy pistons utilized in the 351C and the generally higher R.P.M.s practiced with the engine, caused the rod to pull inward at the parting line and pinch the bearing, causing an unacceptable loss in the oil film clearance sum.  A.K.A the dog-gone pistons were to heavy!      :o

     Scott.