Staff member
Wow, that is some carnage!
Just to note, it did NOT break at high rpm and full throttle, otherwise the carnage would have been much worse. The report was it began to "rattle" in the pre-staging area, and low rpm, so they did the sensible thing and shut it down.

Even so, the experience is financially "unpleasant" for the owner.

Racers need to be "realistic" Vs optimistic about the fatigue life of parts. Critical part "retirement at a service interval", although expensive, is far less pricey than the cost to replace broken and damaged components. And that does not include the repair costs to other components which can be "salvaged".



Crazy about Datsuns
So you think you're having a bad day?

600 cubic inch Big Block Chevrolet on Nitrous Oxide . . . . . WAY over 1000 bhp . . . . . VERY high quality USA made billet crankshaft . . . . .

At 4.625" stroke, NO crankpin to main journal "overlap, as you can see in the photos below, creating "weak spots" where stresses can "concentrate".

Uses 8" diameter, heavy vibration damper . . . . .

View attachment 43

View attachment 44

LOTS of collateral damage to the block, 2 rods, 2 pistons, etc, etc . . . .

Note the classic evidence of a "fatigue" failure (the rubbing marks) up until the final overload break off.

"Gee, the damper kept coming loose, every run. It was weird the way we had to keep re-tightening it."

Be aware of the signs that something is going "wrong" with your engine, before it's too late.


Yowza! But good point about a damper that is constantly loosening up!
I know a guy that went to adjust his valves and one intake valve was way out of spec by .060. They adjusted all of it out to proper spec.
In a few laps his single long 6 cyl cam became 3 variable cams! Game Over!



Staff member
Special Tools, part cinq . . . . .

Continuing along the lines of: "Sometimes you have to buy what you need" . . . . .

If you make the decision to "play with" a "newer" engine type that has "technological advancements", be prepared to fork over dough for the specialized tools required to service one of these Teutonic gems.

Pictured below is a BMW M52tu with Dual Vanos (dual variable cam timing)








The tools pictured are produced by German Auto Solutions. And they are very affordable when compared to the cost of the genuine BMW tooling for this engine. You can even rent them for one time use, if the ride is your daily driver. But if you are in "competition" with one of these 6 cylinder marvels, you probably need to own a set.

And yes, a clever individual with way above average machining talent COULD make their own set.

But why re-invent the wheel? Especially when it is reasonably priced . . . . . .



Staff member
Once again, down the same "rabbit hole" . . . . . .

I confess I have no idea what some racers are thinking. To blissfully continue to make the same assembly error, over and over, and over again. It can NOT be a case of repetitive error, by the third instance, it has to be "active denial" about the "process" that causes the failure.

I, personally, am a fan of the kind of deductive logic used by 'M' and George Smiley:

Once is an "occurance".
Twice might be a "coincidence", if you believe in such nonsense.
Three times is definitely a "pattern".

Readers get to make their own choices about such events.

There are not going to be any photos of the "carnage" in this post, to do so would identify the "victim". And in all reality, there is no need, as this "failure" is on the rise AGAIN, making it somewhat common.

I've just had to perform a "post mortem" on a small 4 cylinder inline engine where the rocker arm adjusting screw locknut was "stripped out" from over torquing. The resulting loss of proper valve lash, took out the rocker arm, pushrod, tappet, camshaft and valve. There was some "collateral damage" to surrounding parts as well. Total cost to repair this fiasco? $700.00 to $1100.00 in hard US currency. And it could have been worse.

My point? Completely preventable!

The solution? Special tools: part six

This is an offering from LSM Racing Products, a "drag centric" specialty tool manufacturer. It is designed specifically for torquing the rocker arm adjusting screw nuts which are the norm in overhead valve drag race engines.

The tool and its' parts
And, the tool in use
YES, it is expensive @ approximately $175.00 USD. Available from Summit, Jeg's, Speedway Products, etc.

It is also very "trick" as it is torque adjustable up to 26/28 foot pounds of torque. It can be adjusted for 1/4" to 3/8" and 6mm to 10mm.

However, this "torque adjustment" feature requires the use of a torque wrench calibration tester. Contact me for access to an accurate unit. Or purchase your own, as shown below.

This is an Intercomp Racing Digital torque Wrench Tester, just like the one I have and use.
YES, it is very expensive @ approximately $545.00 USD. Also available from Summit, Jeg's, Speedway Products, etc.

And now readers, here comes the "tricky bit" . . . . . . . (this is the part I really like!)

So, ahhh, my question is: What is more expensive here?

A/ A couple of "trick tools" worth $720.00 USD of your hard earned cash?
2/ Multiple failures of this nature? (Remember, this example is costing $700.00 to $1100.00, JUST FOR THE PARTS!)
d/ ? ? ? ? ?

Every racer gets to choose who they want to be. "Choose wisely."



Staff member
This is not intended as criticism of anyone's opinion or point of view, and it is not directed toward any specific person. It's just a "brain dump". I do it less often now, as the "brain bucket is nearing empty" . . . . .

I don't know much, but I do know one thing for certain:

that impedes fulfillment of "piston demand", in any normally aspirated engine, decreases power produced. It is as simple as that, back to the "air pump" analogy.

Worst example analogy, from an empirical point of view: If the "transfer area" of a flathead engine is completely "blocked", there is NO FLOW.

Increasing the "transfer area" then, increases flow, up to the point of "diminishing returns". Where this point of "diminishing flow returns", intersects with compression ratio could be modeled with various formats, (such as CFD) but in the finish would need to be verified by dyno testing.

This, in and of itself, is NOT news. This concept is well known and well documented. Re: the Harley work by C. R. Axtell is one source, and there are others. It pays to "dig up" older research and investigate the results. If for no other reasons, than to prevent "re-invention of the wheel" . . . . . . Older engine engineers were not "dopes". Almost without exception, they were very clever and insightful guys who had some sort of limitation placed upon them. Financial, material spec, delivery period, etc. Those guys did the best they could, with what they had. Pretty much the same as today, for engineers who are "passionate" about their work. Physics does not change, it is our understanding of physical application that, evolves, mostly due to "changing of limitations", or perhaps "clarity of understanding".

As I said, that was the "worst example analogy". The "efficiencies" rise as combustion chamber and port shapes evolve. Hence, the potential for "gains" becomes "more limited", the higher up on the internal combustion "evolutionary chain" that an engine design occupies. There could be "reasonable disagreement" among racing engine engineers about what the pecking order of engine designs should be. But let it suffice to say that inlet port flow capability Vs. piston demand is what separates the "performers" from the "pretenders". My opinions about about what designs should go where on that evolutionary performance scale are already formed, and it would take some serious data for me to reconsider the order. For instance, a horizontal port, bathtub combustion chamber will always be "outperformed" by an angle port, 4 valve, pent roof combustion chamber engine. It is a simple matter of flow potential.

Applying concepts to various engine types can be simple, or more complicated. Any bar stool racer can present any theory or opinion. It is the precise, and effective, application of theory, backed up with test data, that is the "difficult and expensive" part. Which is why these things are not done more often, and why persons who "invest" in "testing theories" are less than willing to share their results with the average bar stool racer . . . . . .



VRO Principal
Staff member
I love this: Physics does not change, it is our understanding of physical application that, evolves, mostly due to "changing of limitations", or perhaps "clarity of understanding".

Well said Mark!


Staff member
Once again, down the same rabbit hole . . . . . . part 2 . . . . .

Well, I confess: I'm getting tired of a being a "racing engine coroner". . . "It's like deja vu, all over again." Yogi Berra

No photos of these bits either, a courtesy to the owner. However I know the owner is a "reader", and perhaps may post photos of the "carnage".

This past Monday, a third party brought by the shards of one of the latest BMC 'A' series engine failures. It wasn't a typical failure, as it was a breakage involving "premium quality parts". The failure was a broken, aftermarket "Carrillo style", H beam connecting rod. I think it was in fact, an actual Carrillo (or CP Products now) produced part. Atypically, the rod broke just above what rod manufacturers call the "shoulder" of the rod. This area is just above the "big end", where the beam of the rod narrows heading up to the pin end. This narrowing is required for the rod's big end to clear the bottom of the cylinder walls as the crankshaft rotates. Needless to say, when the rod separated into 2 pieces at high rpm, BAD THINGS happened as a result! The remains were in at least 4 large pieces, and many smaller shards.

The question became: "It's a Carrillo rod, how could this happen? ? ? ?"

Well, let's do a bit of thinking about this question, and this failure . . . . . .

It seems that there is a presumption that, somehow, premium quality aftermarket parts are "indestructible". This is, of course, untrue. But after racers pay out their "big bucks", however, most racers would like to think: That item is "forever".

You are not buying a "diamond"! ! ! (And despite what De Beers claims, even diamonds are not forever . . . .)

OK, OK, I'll get back to reality then . . . . .

A/ H beam connecting rods are usually used because they can be made LIGHTER than I beam connecting rods.
It's a fact that the rod set in question was made for maximum lightness, ie: minimum weight. Premium quality material and premium quality 5/16" rod bolts were used. The ONLY reason to do that is a quest for minimum weight. There can be "advantages" to minimum weight. There are also "disadvantages" . . . .

2/ Note that lighter components are usually LESS durable than heavier parts.
These Carrillo rods are sub 490 gram total weight each. Compare that to the ultra-heavy stock BMC rods weighing 680 grams each, using 3/8" rod bolts. I'm not going to cover this topic again. Go back and re-read reply #21 to this thread. It concerns materials science and reliability.

d/ And there are "other" factors.
I have seen this type of failure previously, on several occasions, for several reasons:
1/ The previously mentioned durability cycle/lifespan reasons.
2/ Unknown inclusions (defects) in the beam of the con rod. Quality manufacturers x-ray every rough blank con rod, and reject those with this type of defect. Lesser manufacturers may not do the same. And there can be "mistakes", despite the best intentions.
3/ Mechanical interference: H beam rods are wider than their I beam counterparts. I have seen engines where inadequate clearance existed between the "shoulder" of an H beam connecting rod and the bottom of the cylinder. Even slight contact between the shoulder of an H beam con rod and a cylinder with inadequate clearance, results in disaster.

So what's the answer?

Well, if you are racing for money or prestige, the lightest weight (mass) components can give you an advantage. This is merely the math, and professional racers accept the risk and the cost of periodically replacing components. This is why ebay has countless "slightly used, but cast off" components for sale. Professional teams use these components for a set number of miles or hours, then discard them. The idea is to prevent a component failure while perhaps leading a race. Statistical analysis proves this to be a sound methodology for success, in spite of increased cost.

But what if I'm racing for "fun"?

If that is the case, then your decision criteria are probably different. The final decision about component weight and the resulting reliability gets to be made by those whose "checkbook does the talking". The decision is: "unlimited" component life Vs. the perceived advantage of light components.

Caveat emptor!



Staff member
Well OK, I guess I need to keep pounding this "nail" . . . . . .

Once again, down the same rabbit hole . . . . . . part 3 . . . . .

Well, AGAIN, I confess: I'm getting tired of a being a "racing engine coroner". . . "It's like deja vu, all over again." Yogi Berra

I've seen a few cams lately that did not die . . . . They were killed. Absolutely a case of "murder" by their well intentioned builders/owners. MOST Vintage and Historic racing engines use flat tappet camshafts. It is just what was used "back in the day". These items require different lubrication and "bed-in" Vs modern roller tappet camshafts. A LOT DIFFERENT. Read this ad from Driven Performance, published in the January 2015 issue of Engine Builder magazine.

If you are having problems with cam/tappet failure, let me know and I'll post my procedure to resolve these issues. Be aware though, that it IS NOT a simple procedure and your particular problem MIGHT require a more complicated "fix".

BTW, Joe Gibbs/Driven is what I use and recommend for most flat tappet camshaft engines. YES, it IS expensive.

BUT, what is your cost for a new cam and tappets? And what is your cost for the other, inevitable engine damage that occurs when your camshaft fails?

It's your choice . . . . . . but it's kinda like the old Fram filters commercial: "You can pay someone now, or you can pay someone later."



VRO Principal
Staff member
Thanks for posting Mark. I run the Driven "DT50 air cooled formula" in my 914.

I remember back about 12 years ago when I had my 993, everyone was running Brad Penn in the air-cooled cars (for the ZDDP), but that hype seems to have died down. Are you familiar with that stuff? I think I remember Steve Bonk telling me it was a really old school oil (could have been called Kendall originally).


Staff member
I am going to start off by saying I am NOT a chemical engineer or a chemist. So there are far more knowledgeable guys out there with respect to this subject.

There is a lot of similarity between certain types of oils. VERY basically, there are 2 main groupings, those with a mineral oil base stock, (as in "from the ground" crude), Vs those with a synthetic base stock. And their properties vary for these reasons, and also because of the differences in the "additive packages". These "differences" can be tiny or massive, and whether the completed product is suitable for use in your engine, depends on a number of fairly complicated factors and engine "requirements".

And since I have started off by explaining my limitations, I'm going to finish off by promising to post a more authoritative article, written by folks within the industry. I just have to dig through my records to find it.



Staff member
As promised, oil info from the oil experts.

There is horsepower in using the correct oil for your application, BUT, it may require you to revise your engine's specification . . . . .

In any event, a COMPLETE reading of the article should be done to gain the most benefit and knowledge.

Source is again Engine Builder magazine from the January 2015 issue.

As mentioned in the article, oil is cheap, even the most expensive synthetic oils, especially compared to all the parts, machine work, assembly, etc, that is INVESTED in your power source. Also note that oil filters need to be considered as part of the "oil system". I am a firm believer in large oil filter capacity and that racing engines should NOT use filters with a bypass valve. Your filter medium should filter all of the oil . . . . . . This does however, require the utmost care in plumbing connections and flow direction, especially through filters with anti-drain back "flapper-type" valves. I have seen more than one engine destroyed by well meaning mechanics who thought that flow direction through the filter did not matter. US Oil filter industry convention is: oil entry through the outer section and oil exit through the center of the filter. BUT, there are exceptions. KNOW how yours should be flowing.