RACING ENGINES, A TECHNICAL EXAMINATION

fordboy628

Moderator
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".

Cheers
 

tabsracer

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.

Cheers

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!

Steve
 

fordboy628

Moderator
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)

45

51

46

47

48

50

49

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 . . . . . .

Cheers
 

fordboy628

Moderator
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
63
And, the tool in use
64
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.
65
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?
OR
2/ Multiple failures of this nature? (Remember, this example is costing $700.00 to $1100.00, JUST FOR THE PARTS!)
OR
d/ ? ? ? ? ?

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

Cheers
 

fordboy628

Moderator
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:


ANYTHING
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 . . . . . .

:cheers:
:dhorse:
 

TopGearTech

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!
 

fordboy628

Moderator
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!

:cheers:
:dhorse:
 
Top