Author Topic: Are they a worth while investment? (SRM conrods)  (Read 2664 times)

Offline bl**dydrivers

  • Valued Contributor
  • ****
  • Join Date: Oct 2008
  • Posts: 254
  • Karma: 1
Are the SRM hi strength billet connecting rods a worth while investment?

I understand a oil pump would be a worthwhile investment being the lifeline of the engine and just want to hear opinions before pulling the trigger on connecting rods.

The original connecting rods appear to be ok, no damage, but with the cost involved in rebuilding the engine would I be gambling by re-using them?

Don’t plan to be racing, but will have a 357 Cam and NOS 8.25:1 CR Pistons.

Offline Black Sheep

  • Resident Legend
  • *****
  • Join Date: Apr 2017
  • Posts: 644
  • Karma: 6
    • Where black sheep live
Re: Are they a worth while investment?
« Reply #1 on: 20.12. 2017 21:44 »
Hopefully Sluggo will come in here. Generally speaking, a forged rod is superior to a billet rod. However, alloy rods don't last forever and we have no idea just how much of an old rod's fatigue life has been used up. 25%, 50%, 99%? I still have original rods in my A7 and A10 but very rarely exceed 5,000 rpm. Having said that, my Norton 99 had a rod fail while bumbling along at a modest 4,000 rpm. On my way to start a new job just to make it more annoying. 
2 twins, 2 singles, lots of sheep

Offline BSA_54A10

  • Wise & Enlightened
  • *
  • Join Date: May 2008
  • Posts: 1985
  • Karma: 32
    • BSA National
Re: Are they a worth while investment?
« Reply #2 on: 21.12. 2017 00:13 »
Billet simply means machined from a solid lump of metal.
So what they are actually saying is produced with the maximum amount of scrap ( which you pay for ).
I never buy a billet anything if I can avoid it because one has no idea of the grain structure and orientation.
There is no way you can machine a rod from a billet and have favorable grain orientation every where that you need it.

Grain size & orientation in a casting is controlled by use of chills and large sprues and secondary runners.
Grain direction in a forging is controlled by the forging itself
Bike Beesa
Trevor

Offline bl**dydrivers

  • Valued Contributor
  • ****
  • Join Date: Oct 2008
  • Posts: 254
  • Karma: 1
Re: Are they a worth while investment?
« Reply #3 on: 21.12. 2017 03:57 »

Offline BSA_54A10

  • Wise & Enlightened
  • *
  • Join Date: May 2008
  • Posts: 1985
  • Karma: 32
    • BSA National
Re: Are they a worth while investment?
« Reply #4 on: 21.12. 2017 04:27 »
Yes.
Bike Beesa
Trevor

Online Billybream

  • Resident Legend
  • *****
  • Join Date: Jan 2012
  • Posts: 516
  • Karma: 5
Re: Are they a worth while investment?
« Reply #5 on: 21.12. 2017 06:59 »
One of the items on my BSAs Christmas Santa wish list.
1960 Super Rocket, owned since 1966, back on the road 2012 after being laid up for 29yrs.

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 1423
  • Karma: 12
Re: Are they a worth while investment?
« Reply #6 on: 21.12. 2017 07:01 »
Yes.

I totally agree, I fitted billet rods from thunder engineering of the uk, who used to supply SRM. The alternative was crack testing, shot peening, sizing and fitting new small bushes to the OEM rods, cost of which came to half the cost of new billet rods.

Carrillo steel rods may very well be the ultimate rod from strength perspective (but how would you know?), but they are not always available in my experience. I’ve been told they only supply “economically” sized batches to the various BSA parts suppliers we know, and those suppliers don’t seem to want to take risk of having them left in stock for ages.

I found the Thunder brand rods hardly affected the balance factor on my SJ crank, a couple of years I wrote a (rather) lengthy post on the topic......”crank balancing DIY”.

Edit, here’s a link https://www.a7a10.net/forum/index.php?topic=6086.msg41598#msg41598
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, project missing parts, mission impossible?

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife

Offline cyclobutch

  • Wise & Enlightened
  • *
  • Join Date: Aug 2010
  • Posts: 1456
  • Karma: 14
Re: Are they a worth while investment?
« Reply #7 on: 21.12. 2017 08:53 »
I've never really understood why 'billet' anything has much cachet.
Various, including ...
'58 Iron Head Flash Bitza


Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Are they a worth while investment?
« Reply #8 on: 21.12. 2017 09:05 »

 
Quote
....a couple of years I wrote a (rather) lengthy post on the topic......”crank balancing DIY”.

 Yes and I did mine at same time,  and you asked me how I did mine but I'm still working on the reply, I  haven't forgotten the request, just how I did it, and what I did with the info... *conf2*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Sluggo

  • Serial Hoarder, or Eccentric Collector depending on viewpoint
  • Resident Legend
  • *****
  • Join Date: Jun 2017
  • Posts: 639
  • Karma: 11
Re: Are they a worth while investment?
« Reply #9 on: 21.12. 2017 09:22 »
Hopefully Sluggo will come in here. Generally speaking, a forged rod is superior to a billet rod. However, alloy rods don't last forever and we have no idea just how much of an old rod's fatigue life has been used up. 25%, 50%, 99%? I still have original rods in my A7 and A10 but very rarely exceed 5,000 rpm. Having said that, my Norton 99 had a rod fail while bumbling along at a modest 4,000 rpm. On my way to start a new job just to make it more annoying.

<Flattered>  *thanks*   But I tend to sound like a broken record on this........    Blacksheep is correct though about a stock rod.  Alloy rods are springy when new but have a service life, Stan Shentons "Triumph Speed tuning" Bible quotes the Triumph factory engineers as saying the service life of a Alloy rod is one 500 mile race. American top fuel dragsters get one pass down the strip.  You can buy used NASCAR racing rods cheap on ebay as they have usually a one race life.

Our old bikes dont see those kinds of stresses but largely unknown with a used bike WHAT stresses its seen so poor economy to reuse.   That being said... I DO sometimes.  But when I do it gets a full crack inspection, checked for straightness and then resized.  ( A little off the cap joint surfaces and then remachined to true round again, a used rod is NOT round once removed).  But that being said, I will only do that if it looks, tastes,smells good to begin with and then severely RPM limited.  (Same with the rod bolts)

For a Sunday plodder with low comp and mild cam I would say roll the dice after a full rebuild with a competent machinist.  But you mention a perf cam and higher compression so my answer is I would suggest the steel rods (H beam).  I agree with Trevor that Billet rods are kinda iffy.,, If it was for a Small Block chevy from a well known vendor and price was right I would consider it, but not for the BSA Application

I have seen some decently priced rods of the steel variety and similar to the Carrilos or were made by Carillo? (I dont recall) But I know MAP cycles and the owner is Marino and they have been a consistently awesome vendor for decades.  I have used their belt drives and some of their other products and always been very happy.  They support the purchaser with tech and are nice people to deal with.  I was  a dealer acct for them for years and often ordered from them for customer builds.  Plus, they race, and they support racers so,,, I do like MAP..

The problem in the past was that steel rods were really heavy.  Re-balancing is a must but it was a real problem 15-20 years back.  I have not done a survey of rod weights and specs  but my *UNDERSTANDING* is that the newer generation of the steel H beam Carrillo type rods are now made with much lighter weights while retaining great strength.  So,, not as much of a problem.

I will add this,, (Because I am pedantic and a bit OCD) the following:

A) I cant say for preunit BSA Twins for sure, but I CAN say that BSA Unit twins and BSA Singles in my experience tend to have wildly varying piston weights and specs.  The current crop of Asian made pistons out there for BSA tend to be VERY Heavy.  That is something I am looking into for my 2 keeper A65s, It was a problem on my last build.  I have some OEM Hepolight/Wellworthy A10 pistons and plan to do some weights and measures.  The Asian made pistons are overall excellent quality and consistent standards as opposed to some really weird things with the OEM pistons.  But for whatever reasons last 10 years the repops weighed way more than std, something to take into acct.   (Measure twice-cut once)

B) While a static balancing job is better than nothing, in my opinion its next to worthless and a waste of time.  DYNAMIC Balancing is the only way to go.  You cannot fix rocking couple any other way and a Dynamic balancing job for your bottom end is well worth doing, If you cant find a good shop to do it, then find one who will accept the parts being shipped to them.  My guy is 2 hrs south of me and I often shipped him a specially lined box with crank, rods, pistons and any other bit that rotates. I also do alternator rotors for crank mounted applications. (A lot of weight flopping around on the end of that bean stock).   Local vintage Harley guys use him as well and I can point to Panheads, Knuckles and shovels that are so smooth you would think its a sewing machine.  Nortons are the worst for this and have had Not-runs that shook so bad parts fell off L&R and Ernie transformed those motors.  I have built Atlas's that people swore was a Honda they were so smooth.

C) Careful blue printing of the cases and crank will reward you greatly.  Again I cant say for certainty on a Preunit BSA Twin, but I can say from experience that BSA Unit Singles, Preunit singles, and Unit twins all seem to suffer from core shift and dimensional changes. (Or they were buggered from day 1)  My friend Sir Eddy used to blue print engine cases for me and others locally and while some were pretty good, We saw a LOT of them that were way out of spec.  A local guy who used to race Goldstars had repeated seizure and blow ups with his Goldies.  Eddy showed him how they were out of whack.  Eddy tended to value his skills highly monetarily and this guy who had the Goldies,, well lets just say is quite focused on economy and said it was too much $$$$. Promptly seized up his motor next race.   I will know more in the next 6 months about preunit cases for BSA as I have several cases to check, Might write a tech article on how to do it and my results,  But it would NEVER hurt a dang thing to check your cases and parts carefully.

SRM parts sure look nice, But I am not sure they all are worth what they are charging, Maybe they are.  I have no experience with those Thunder rods,, But I do have a BSA B50 Carillo rod sitting on the bench I can post pictures of.  I think they are worth every penny and its well reported that the BSA B50 rods stock had issues so was well worth the dosh in my opinion to buy them.  I worked in manufacturing (Aerospace) and my wife currently does in machine and manufacturing at a large volume shop and I can say the Carillo brand products are EXCELLENT and I would not hesitate to recommend them as good value.  (35 years experience with them)

I have never regretted erring on the side of quality parts and replacing parts I was not certain of. 

"Dammit to hell I wish I hadnt spent so much on new bearings said no one ever".
Remember that any advice received on a free internet forum is generally worth about 1/2 of what you paid for it.
We overcharge every 3rd customer to pass the savings onto you.
You can have High Quality, Low price, and fast turnaround. Pick any 2, Never all 3 at the same time.

Online JulianS

  • 1962 A10
  • Resident Legend
  • *****
  • Join Date: Mar 2017
  • Posts: 971
  • Karma: 20
Re: Are they a worth while investment?
« Reply #10 on: 21.12. 2017 09:26 »
I fitted Thunder Engineering rods about 5 years ago for my peace of mind and because of the quality of new bigend bolt sets offered.

Before the Thunder rods I tried wassel supplied rods made by R and R which were a waste of money - BSA rods are 6.46 inches between centres - the R and R made to 6.5 inches. Not a lot maybe but why use a part made to the wrong specification and reduce piston to valve clearance.

Thunder and SRM rods are made to the right specification.

Offline Sluggo

  • Serial Hoarder, or Eccentric Collector depending on viewpoint
  • Resident Legend
  • *****
  • Join Date: Jun 2017
  • Posts: 639
  • Karma: 11
Re: Are they a worth while investment?
« Reply #11 on: 21.12. 2017 09:37 »
I've never really understood why 'billet' anything has much cachet.

*** SORRY ADMIN, Please forgive my off topic comment here***

Haha!   Well,, I find it amusing some of the rivet counters and "Anal retentive bolt polishers" get all worked up about stock cast pistons when billet or forged ARE better.  You would think Hepolite was Gods personal gift to man kind if some people are believed.  Rods??? Different animal though. 

My wifes company makes some amazing stuff out of all kinds of "Billet" and in very large volumes.  Just depends on what you need it for.     Would you like, alloy,steel, copper,Brass, stainless or????
See: http://www.enochmachining.com/

But in some places "Billet" is a dirty word and reviled.   I know these guys and I really like their events.

See: http://www.billetproof.com/

" Why do you hate Billet parts?
We dont. We respect the high tech side of the hot rodding world. This just isnt the show for those style of cars. Billetproof is for 50’s and 60’s styled hot rods and customs.
-------------------------------
I have an Aluminum intake on my car, can still come to the show?
Yes. Cast Aluminum parts are fine. Obvious machined billet Aluminum parts are not.
-------------------------------
RULES
1964 and prior TRADITIONAL style rods and customs ONLY
No visible billet anything! Especially wheels!
No digital gauges
No IFS on fenderless cars
No trailer queens
No mag wheel styles made after the 60’s
No high tech styled, pastel heart beat graphic, tweed interior, fenderless IFS sporting hot rods
Traditional looking choppers and bobbers ONLY! (No modern West Coast Choppers, OCC style bikes)

(Note: They LOVE vintage bikes as well, anything mid 70s and earlier welcome, especially vintage British)
Remember that any advice received on a free internet forum is generally worth about 1/2 of what you paid for it.
We overcharge every 3rd customer to pass the savings onto you.
You can have High Quality, Low price, and fast turnaround. Pick any 2, Never all 3 at the same time.

Offline Black Sheep

  • Resident Legend
  • *****
  • Join Date: Apr 2017
  • Posts: 644
  • Karma: 6
    • Where black sheep live
Re: Are they a worth while investment?
« Reply #12 on: 21.12. 2017 09:56 »
I have watched Buccaneer main spars being machined from billet. 95% ended up as swarf for recycling. Amazing. Wonderful aeroplanes. Unstoppable. However, they too suffered from fatigue. One had a wing fall of on a red flag exercise. Not so good when you are at 650 kts and 20 ft.
2 twins, 2 singles, lots of sheep

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 1423
  • Karma: 12
Re: Are they a worth while investment?
« Reply #13 on: 21.12. 2017 10:31 »
Here is a link to the thunder engineering web site. They use a good (known) quality billet material, it is true that just because a part is machined from billet, it does not necessarily make it a high quality part.

The thunder rods look to be significantly beefier in section than OEM rods, and 5hey are heavier, which is why I went though the excercise of calculating the effect on using the rods on crank balance factor. Conclusion was a neglible effect, much less than some non OEM pistons and gudgeon (wrist) pins.

I reckon that whilst a new A10 forged rod (steel or Ali) could in theory be better than a billet one, the challenge would be find a supplier of them, at a reasonable price, having said that I do know of people with Carrillo rods, maybe they were lucky.

http://www.thunderengineering.co.uk

New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, project missing parts, mission impossible?

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife

Offline Sluggo

  • Serial Hoarder, or Eccentric Collector depending on viewpoint
  • Resident Legend
  • *****
  • Join Date: Jun 2017
  • Posts: 639
  • Karma: 11
Re: Are they a worth while investment?
« Reply #14 on: 21.12. 2017 10:36 »
While we take many parts for granted, the smallest details can be terminally destructive.  Of course BSAs just ventilate their cases and coast to a stop, but in aircraft its generally unpleasant to have structural parts fail and kill everyone on board.    I studied this in college and tech courses and this is a engineers report on how structural failure can occur related to the Lockheed disaster.  Ironically, the US Navy flies a nearly identical acft with no issues and has for decades of service and thousands of hours service.

See: https://www.quora.com/What-are-the-sources-of-aircraft-wing-vibration

Prior to computer modeling that would have caught this problem this was an issue that baffled all the experts and the final reports are still inconclusive, but the condensed version was the acft and wings passed all testing until loaded with passengers.  Simply changing the propellers slightly moved the vibration signature to a different frequency and cured the fatal crashes. 

The relevance to BSAs is tenuous here, but still relevant (Blacksheeps fault for bringing in a Acft discussion) but vibration can be destructive and a vertical twin has a degree of it, But you can eliminate much of it by Blueprinting the components to optimum, and then balancing it to where the harmful vibrations that remain can be moved to a RPM range not typically seen in the machine. (What my balance guy does)

The above link is a very educational read, and anyone who wants to better understand materials science can learn a lot from it.

If you guys could SEE what happens in slow motion photography what is going on in a recip engine at speed and how much parts flex, bend and beat themselves during the whole "Suck,Squeeze,Bang,Blow" cycles it would freak you out.  Mechanical sympathy is a trait to be cultivated and nurtured.
Remember that any advice received on a free internet forum is generally worth about 1/2 of what you paid for it.
We overcharge every 3rd customer to pass the savings onto you.
You can have High Quality, Low price, and fast turnaround. Pick any 2, Never all 3 at the same time.