Stock rod bolts - how much can they take?

[Garrett]

How much power can stock rod bolts take?  I am building a 1915 using stock reconditioned rods.  I'll assume they are using the stock rod bolts too.  How much power / rpm can these take?   Were these components over engineered from the factory too - like the rods?

Thanks!

-Garrett

[mmccarthy]

anything will work for a little while,but save your money up and buy a set of rods, Those I beam rods  with 3/8ths bolts look like a great buy.JMO                                   Mike

[Garrett]

I hear you.  Stronger is most-usually better   

I guess what I am asking is....will a 130-140 hp cause problems with the stock bolts?

I was looking at the CB Unitech rods....they seem to be priced pretty well ~ $130 (with 3/8" ARP bolts).   I have the short block already assembled with sealer and the rod bolts red lock-tited.      

Just wondering at what point is it necessary to move up to stronger components....

-Garrett

[louisB]

According to Seume's interchange manual stock rod bolts are only good for a mild street engine that is not reved over 5000 rpms. It may be a PITA to split the case, but I think it would be worth it for the peace of mind and step up to better bolts/rods.

--Louis

[bones65]

I had a 1776 with a FK-87, lots of head work 48’s and VW rods. I twisted it to 7800 rpm’s regularly (at least every time I drove it), never had a rod or rod bolt failure. The big problem was the big end of the rod getting out or round. I had 3 sets or rods and would change the every 5k. I would rebuild once and change rod bolts at that time. I think if you kept it under 6000 rpm’s you would probably never have a problem if the rods were rebuilt with new bolts.

[Islandbugs]

Two things
1. 165 to 200 hp many years, several engines stock VW bolts revving 7000 to 7500
2. Why would you have to split the case to change rods? Tricky at times but far from impossible.
Wayne

[Garrett]

Why split the case?  Well, obviously I'd rather not go that route.  I was just thinking about getting the rod bolts un-loctited without making a mess inside the case.   

I'll need heat fur sure - then what about all the little crusty loctite crap that'lll fall everywhere when I take em off?  I could probably stuff the case under the rods with paper-towels I guess.....that should catch (most of) it.

In knee-jerk-fashion, I went to cb's site this morning and ordered a set of their unitech's with arp bolts

-Garrett

[sandshark]

I have personally run stock rods in engines producing 150 horse (est), revving to 6000 rpm with no problem. The shop car where I used to work (sand dragster) ran stock type "stroker vw rods" in a turbo car producing in the range of 350 to 400 hp for many abusive years with no failures.

Here's how  I see it... VW rods are a known commodity...

But most all of the "affordable" aftermarket rods available nowadays are Chinese imports built in factories with little to no quality control... it's a crapshoot what you're gonna get.

I work in the auto industry and many of my suppliers (of several different commodities) are now based in China... not a damn one of them is any good.

Chinese equals SH*T - no exceptions... at least that's been my experience.

Until I can afford to run Carillo's, I will stick the with trusty, tried, and true VW rod...

[turbodon1776]

I ran stock rods in my turbo 1776 for a while then stepped up to cb h-beams. but they did survive some hard street pounding and 20 lbs. of boost at the strip. If im not mistaken all the machine work on the cb rods is done "in house "  I spec'd mine out before installing them and they were all right on the money.

[louisB]

I don't think the issue are the rods, but the stock bolts. Stock rods with better quality bolts have been run by many for years with good success. While it seems some here have had good success with stock bolts in stock rods I just think it is cheap insurance.

[Mike Lawless]

You'll need the rods resized again after pressing out the old ones and installing new ones.

Makes a good case for these kinds of decisions before the machine work is done and the motor's together

[A.J.Sims]

my 1835 turbo made over 220hp on 24lbs of boost and ran 11.44 @118mph at 8,000rpms with stock rods and stock bolts. the motor was close to 6 years old at that time. Should some else try this? NO!!!
Rods are so cheep now so just spend the $$$ for "I" or "H" beam with ARP2000 bolts and a strech gauge.

[Greg G]

Just have the short block up side down on the engine stand, then any loctite that falls out can be easily vacuumed out of the case. I don't think you will need heat to take the nuts off.

[Bruce Tweddle]

According to Seume's interchange manual stock rod bolts are only good for a mild street engine that is not reved over 5000 rpms.

That claim is laughable.  Stock rods and rod bolts are very reliable to rpms well beyond that.

[Greg Ward]

1915cc Stock Rods(rebushed), stock bolts, 8000+ rpm street and track.

You won't have any dramas so long as they are reconditioned and stay on a stock stroke.

Most claims of failure will be from something that is not a stock stroke engine, and/or lack of attention to detail when putting it together.

[jays57]

Call Rimco and order a set of their super rods.  They are stock rods, better bolts, shotpeened, everything you would want to do to a rod to make you feel comfortable that they will hold up.  You can't go wrong with them , I would trust a set of these way more than a set of aftermarket i-beams.  They hold up to rpms and last a long time.  Or call Gene Berg and order a set of "done-up" stock rods from them.

[dangerous]

When I first started racing, all that was available were stock rods or expensive rods.
That meant Carrillo, Pauter, Crower, Jet or other quality rods.
I found the stock rod to be reliable at rpms up to 7000, but were always out of round at freshen up time.
With the ARP bolts (must re-size) to suit the VW rod, they were even better.
I used them with my 1776 blower engine for years (10.65@127@1750lbs)

For Garrett's proposed use they will be fine, but there are many options out there these days
that will cost less than a set of properly reconditioned stock rods.

An added note if you choose stock rods, is to get a couple of sets
 to find a set that are closer to each other in end for end weight,
and have those reconditioned. This saves removing excess material.

[James2]

I just worry about the bolt, on stock rod you don't know how many times it's been torqued. You can get good bolts, but they are almost as much as a cheap I beam rod with the HD 3/8 bolt.

99% of the problems with rods can be traced back to the bolt, either it stretched and let the bearing spin or it broke and threw the rod out the case.

If you look at the rod, it's two big chunks of metal connected by two bolts that are a little more then a 1/4 thick. At 5000 rpm, the load on the bolts is over 6000 lbs. Now cycle that load over 10000 times a minute.

It's just my opinion, that the I beam with the bigger 3/8 bolts are cheap insurance. I've ran the stock rods past 7500 rpms before also. But not since I discovered $150 I beams with 3/8 bolts. They are damn near bullet proof.  I got one set that has been in three engines, still in perfect shape.

[JCquick]

I've put over 200 passes on stock 311b rods at 8k plus I took those rods out and out them in a mild 1776 that has been running for 4 years now.
I have a set of jap copies that have 3/8" rod bolts, shot peened and ready to go that I'll sell cheap. cause I  just don't trust them.

[ErikTheRed]

Have you ever compared a stock Chevy 350 V8 rod to a stock 1600 VW rod? Damn near identical. IMO, VW way over-designed the rod for these engines, giving us a nice advantage with being able to use them for more high-performance applications.

This also seems a good place to bring up another issue, something I heard or read awhile back but still dont know the real deal.......can anyone either verify this or blow it outta the water?

COMPRESSION strength, as in the forces exerted upon the rod during a compression stroke, is greater with an I-beam design. Therefore, one should opt for a quality I-beam rod when the compression load will be great but RPM's kept reasonable, such as in many turbo applications. H-beam design rods have a much greater TENSILE strength, or pulling strength, which makes them more desireable for high-rpm applications. 

[Carbon Dave]

Berg ran sock rods in some high HP applications.

That being say and as James pointed out...that was well before decent quality "CHEAP" I beam rods with good bolts. It is going to cost as much for a properly rebuilt stock rod and new bolts. Go China....

[Bruce Tweddle]

This also seems a good place to bring up another issue, something I heard or read awhile back but still dont know the real deal.......can anyone either verify this or blow it outta the water?

COMPRESSION strength, as in the forces exerted upon the rod during a compression stroke, is greater with an I-beam design. Therefore, one should opt for a quality I-beam rod when the compression load will be great but RPM's kept reasonable, such as in many turbo applications. H-beam design rods have a much greater TENSILE strength, or pulling strength, which makes them more desireable for high-rpm applications.

There's no difference between compressive strength and tensile strength.  The yield strength of the material doesn't depend on which direction the forces are applied.

[bufferman]

for a few of you old timers remember bad news old race bug just talked to him he is running stock rods redone by rimco  leaves at 8200 and shifts at 9000 same rods for five years still round and good motor still going today have a $92.00 berg 69 mm crank yeah had it a while fk89 cam 1835cc motor .042 deck 13to1 old stock oem stuff does work and last he is up in snohomish wa. for those of you that know dyno don  he knows the car ask about it  a low budget build up

[bugnut]

Just curious if, in the last three years plus, what peoples' thoughts are on stock versus aftermarket rods.  I've got a set of stock, German rods that I'm likely to have reconditioned and stroker clearanced for my 2017cc build up, but just wanted to see what other folks thought.  Particularly with stock bolts.

[Busstom]

There's no difference between compressive strength and tensile strength.  The yield strength of the material doesn't depend on which direction the forces are applied.

Wrong.  (Or should I say.....now THAT's laughable  )   Nominal compression strength is almost always greater than tensile due to an increase in the effective cross section under compression.  Open your Machinery's Handbook and work some formulas.  

On the other hand, other forces encountered in compression, i.e. buckling, can cause failure before theoretical ultimate failure is reached for a given material.  

On those CB H-beams, I too just spec'd a set, and weighed them on a recently calibrated scale at work (aerospace), and they were within .3 grams of one-another.  If you're curious of what amounts to .3 grams, it's about two post-it notes....I don't know what country they're forged in, but these things are dead nuts...can't wait to run these babies!

[Bruce Tweddle]

Wrong.  (Or should I say.....now THAT's laughable  )   Nominal compression strength is almost always greater than tensile due to an increase in the effective cross section under compression.  Open your Machinery's Handbook and work some formulas. 

The argument is moot.  Rods don't fail that way.

[Bruce Tweddle]

Just curious if, in the last three years plus, what peoples' thoughts are on stock versus aftermarket rods. 

  The last 3 years don't mean much.  Stock rods have proven their mettle from back in the 70s and 80s when all we had was either stock rods, Porsche rods, or mega buck Carillos or Jet rods.
Here's another for you.  My old 2 liter went over 80k miles.  With stock rods, my rev limiter was set to 7200 rpm.  I touched it EVERY DAY. Those rods are still in a box somewhere, wanna use them?

[bugnut]

  The last 3 years don't mean much.  Stock rods have proven their mettle from back in the 70s and 80s when all we had was either stock rods, Porsche rods, or mega buck Carillos or Jet rods.
Here's another for you.  My old 2 liter went over 80k miles.  With stock rods, my rev limiter was set to 7200 rpm.  I touched it EVERY DAY. Those rods are still in a box somewhere, wanna use them?

Thanks for the reply, Bruce, I appreciate your directness and input on this.  I appreciate the offer, though I do have a set of stock rods I just need to get checked for spec.

[Darren DVKK- K-Roc]

Bruce isn't lying about hitting the rev limiter every day, when we worked for the same company many years ago he usually was the "driver" at lunch time. Sideways at 7000 RPM into the shopping mall parking lot was just another day for the old Yellow late model.

The really fun rides were in the Rusty Blue Super Bettle that he attempted to debead the tires at every corner.............Damm Maniac.....

[David Ward]

That claim is laughable.  Stock rods and rod bolts are very reliable to rpms well beyond that.

Totally agree.   Quality rebuilt 311b's work very well in most applications.  We had a 74x90.5 that regularly saw 7500+ without failure running Berg clearanced rods for many years.

I think the issue today is simply that by now many of these rods are well over 30 years old and may have seen many years and miles of service.  Sure they can be checked out and such, but a new set of 5.400" I-beam rods with 2000 bolts for under $190 is worth considering.  Still, I'll soon be assembling a 69x94 engine for my Thing project and I'll be using a nice set of stock 311b rods.  No worries.
 

[lamar chambers]

whats the differance between the 311B rods and the J311 rods?
i ran a 1850cc 76x88 with the J311 rods stroked with NOS and single 48IDA that was built in 1975 and lasted forever. i still have these rods and pistons and i think they came from CB.  just wondering if they are the same.  thanks  Lamar