RACING ENGINES, A TECHNICAL EXAMINATION

treid

New member
Yes it does I have had my motors dyno'd many times over the years and while I am not real concerned about the number aka California HP but the improvements we are able to find and learn from. Thanks

Terry
 

tabsracer

Crazy about Datsuns
Everybody, great information that is being shared.
One thing that stands out from Ford Boy's comments is that many dyno pulls didn't show HP gains or out right losses.
That reminds me of a quote from a buddy after us trying lots of combinations on a Datsun L series 6 cyl engine over a couple of days dynoing. "Well, we have learned what doesn't work so far"LOL Anybody that has spent many years doing a specific formula to a rules package knows that is the nature of the beast.
Cheers,
Steve
 

fordboy628

Moderator
Staff member
Well, I do dyno testing all the time, and I review A LOT of dyno data. What I can promise you is:

A/ Not all your "bright ideas" are going to add bhp. Neither do mine. My success rate is going to be higher than yours, because I do more testing.
2/ Your buddy's "hot setup" for jets, timing, etc, is NOT going to work on your engine, UNLESS they are IDENTICAL.
d/ Be prepared for dyno testing to be a time consuming test regimen of ALL the "reasonable" permutations. Otherwise you WILL leave bhp
"on the table".

The circumstances above beg the asking of this question: "What is knowledge?"

Is "knowledge" always "knowing what works"? Or can knowledge sometimes be "knowing what does not work"?

I know my answer. And you should choose wisely . . . . . . .

Cheers
 

fordboy628

Moderator
Staff member
Special tools:

Sometimes you just need something that is not commercially available. To make something finicky a bit easier. I admit that I am basically lazy, so I have a batch of "special tools" that allow something to be accomplished "easier".

Since a picture is worth a thousand words:

Ford 1500 flywheel turning tool. For precise cam timing checks. Can easily lock the crank/flywheel in any position.
36

Another view:
37

And a 3rd view:
38


This is a specific tool to fit a specific engine with a fixed size flywheel. The idea can be adapted to ANY engine type and it doesn't require a lot of machining or fabrication skills.

Cheers
 

fordboy628

Moderator
Staff member
Special Tools, part deux . . . . .

So you're thinking your bent piece of coat hanger wire is a good tool for checking cam timing? Think again . . . . .






ROCK SOLID, will not move. Still think your bent piece of wire is good enough?

If you have EVER used the phrase: "I can build an engine as good as anybody." make sure your tools are up to the task.

Cheers
 

fordboy628

Moderator
Staff member
Special tools, part trois . . . . .

Sometimes you can't make what you need. You just have to "bite the bullet" and cough up the big bucks . . . . . .





It was expensive "back in the day". Not sure if this model is still available.

BUT, if you have a belt drive engine, you better have something similar.

Cheers
 

fordboy628

Moderator
Staff member
Special Tools, part quatre . . . . . .

Another special flywheel turning tool. This one is adjustable in several dimensions, because English Ford/Lotus/German Ford share at least 5 flywheel diameters and at least 7 different ring gear types and tooth counts. 2 different pinion types, 5 different axle positions, slot for diameter adjustments, locks for flywheel bolt tightening, etc. Pass-thru ratchet for turning allows easy lock nut tightening with a separate wrench or ratchet.

Again, the idea can be adapted to ANY engine type . . . . . like Datsun L-series or whatever . . . . .











It takes a bit of effort to fabricate one of these gizmos. But once you have something like this, you'll wonder how you got along without it.

Cheers
 

tabsracer

Crazy about Datsuns
You got a "Awesome set of tools" I think that is from Fast Times at Ridgemont High? lol
I have not adapted it yet. But I bought one of those timing wheels that is the size of ships steering wheel! Talk about accurate. lol
Welcome back, lets get some more folks coming back here!
Cheers,
Steve
 

fordboy628

Moderator
Staff member
The Comp Cams cam timing wheel pictured above, attached to a Rover K series 4 valve belt drive, is 11/12 inches in diameter. The smallest size I will use. I prefer the big 15/16 inch diameter wheels, but they can be difficult to fit to smaller 4 cylinder engines. The small 7 to 9 inch diameter cam timing wheels are better than nothing, but I've quit using them because they are not as accurate as the larger ones.

If you are using a 7 inch wheel with a piece of bent coat hanger as a pointer, well, you just don't seem to be serious about your cam timing . . . .

Cheers
 

fordboy628

Moderator
Staff member
Alert for BMC 'A' series racers . . . . .

Recently I have seen and have had additional reports of billet 'A' series "ghost main" crankshaft failures. Some of these cranks were "broken" in service, destroying much of the engine. I suspect that this is occurring due to torsional stresses that result when a crankshaft damper is NOT used. Additionally, low mass cranks are inherently less stiff and twist more under torsional stress . . . . . .

If you are using one of these units, or any crankshaft WITHOUT a damper, you might want to have it magnaflux inspected. Additionally, it would be prudent to log the number of service hours on any "ghost main" or "wedged" BMC 'A' or 'B' series crankshafts. At some sensible service interval, these cranks need to be checked, to prevent a massive and expensive failure.

Yes, I know there are several engine types out there, successfully running without a crankshaft damper of any type. In general, those cranks are "over-designed", which explains their successful usage. Additional mass, by itself, adds damping. The flip side of this is that there are also racing engines out there which will destroy a crank in short order if the damper becomes "loose".

Caveat emptor
 

tabsracer

Crazy about Datsuns
Alert for BMC 'A' series racers . . . . .

Recently I have seen and have had additional reports of billet 'A' series "ghost main" crankshaft failures. Some of these cranks were "broken" in service, destroying much of the engine. I suspect that this is occurring due to torsional stresses that result when a crankshaft damper is NOT used. Additionally, low mass cranks are inherently less stiff and twist more under torsional stress . . . . . .

If you are using one of these units, or any crankshaft WITHOUT a damper, you might want to have it magnaflux inspected. Additionally, it would be prudent to log the number of service hours on any "ghost main" or "wedged" BMC 'A' or 'B' series crankshafts. At some sensible service interval, these cranks need to be checked, to prevent a massive and expensive failure.

Yes, I know there are several engine types out there, successfully running without a crankshaft damper of any type. In general, those cranks are "over-designed", which explains their successful usage. Additional mass, by itself, adds damping. The flip side of this is that there are also racing engines out there which will destroy a crank in short order if the damper becomes "loose".

Caveat emptor
Mark, I have heard the term GHOST MAIN crank but have never seen one. Is that crank style only used in BMC engines?
Do you have a picture of a stock crank and a ghost main crank?
Cheers,
Steve
 

fordboy628

Moderator
Staff member
Mark, I have heard the term GHOST MAIN crank but have never seen one. Is that crank style only used in BMC engines?
Do you have a picture of a stock crank and a ghost main crank?
Cheers,
Steve
I'll see if I can dig up photos of both. Stock cranks, no problem. Might take a bit for the Ghost Main.

Cheers
 

fordboy628

Moderator
Staff member
OK, here are the photos.

First up, std type BMC crankshaft, Mini version. 4 counterweights, beefy connection between rod journal pairs.





And the "ghost main". Note the addition of 2 "extra" non-functioning main journals and 4 extra counterweights.


Although these cranks are not "low mass" per se, the connecting "arms" between the paired journals use a thinner cheek cross section than the standard cranks. These are photos I downloaded from the web, from one supplier. I'm not making any claims about this particular product. This type of crankshaft is being manufactured here in the USA and in various European countries. At this time, I am uncertain of the source(s) of the failed product. Some providers have removed their product from the market while evaluating the component failures.

Inline 4 cylinder crankshafts of 3.200" stroke, have an "undamped" secondary harmonic. If the part is operated in an rpm range of notable resonant frequency and without any external vibration damping . . . . . . well, the inevitable happens.

BTW, 3.250" is the stroke of a 327 cubic inch Chevy V8. No secondary harmonic, and they run vibration dampers . . . . . :unsure:

Caveat emptor

Cheers
 

tabsracer

Crazy about Datsuns
Th
OK, here are the photos.

First up, std type BMC crankshaft, Mini version. 4 counterweights, beefy connection between rod journal pairs.





And the "ghost main". Note the addition of 2 "extra" non-functioning main journals and 4 extra counterweights.


Although these cranks are not "low mass" per se, the connecting "arms" between the paired journals use a thinner cheek cross section than the standard cranks. These are photos I downloaded from the web, from one supplier. I'm not making any claims about this particular product. This type of crankshaft is being manufactured here in the USA and in various European countries. At this time, I am uncertain of the source(s) of the failed product. Some providers have removed their product from the market while evaluating the component failures.

Inline 4 cylinder crankshafts of 3.200" stroke, have an "undamped" secondary harmonic. If the part is operated in an rpm range of notable resonant frequency and without any external vibration damping . . . . . . well, the inevitable happens.

BTW, 3.250" is the stroke of a 327 cubic inch Chevy V8. No secondary harmonic, and they run vibration dampers . . . . . :unsure:

Caveat emptor

Cheers
Thanks for finding that and sharing. Nice looking piece.
I am guessing the Ghost Main is to keep flex down under high rpm?
I have heard about them for a few years now.
Glad I never got the "BMC Bug" lol That is a lot of work to get the ponies out those engines.lol
Cheers,
Steve
 

fordboy628

Moderator
Staff member
Thanks for finding that and sharing. Nice looking piece.

I am guessing the Ghost Main is to keep flex down under high rpm?

I have heard about them for a few years now.
Glad I never got the "BMC Bug" lol That is a lot of work to get the ponies out those engines.lol
Cheers,
Steve
Presumably that is one of the benefits. The issue is that ALL of these ultra trick and/or expensively modified cranks seem to have a high failure rate combined with a "limited" (short) service lifespan.

And the failure in service result is: expensive

Cheers
 

tabsracer

Crazy about Datsuns
Presumably that is one of the benefits. The issue is that ALL of these ultra trick and/or expensively modified cranks seem to have a high failure rate combined with a "limited" (short) service lifespan.

And the failure in service result is: expensive

Cheers
Mark, what is the other option?
Are those Ghost main cranks billet?
If a billet crank is failing where do you go for a quality BMC crank?
Steve
 

fordboy628

Moderator
Staff member
Mark, what is the other option?
Are those Ghost main cranks billet?
If a billet crank is failing where do you go for a quality BMC crank?
Steve
Steve,

In order:

Mark, what is the other option?
The other option is a "standard style BMC" billet crankshaft. Made from EN40B or equivalent and properly nitrided.

Are those Ghost main cranks billet?
Yes.

If a billet crank is failing where do you go for a quality BMC crank?
To a specialty crank manufacturer who is NOT experiencing these failures. Not sure who those are. Plus, keep in mind that eventually, EVERY HIGHLY STRESSED INLINE 4 CYLINDER CRANKSHAFT WILL FAIL. There is no such thing as a "failure proof" part. Re-read posting #21 on this thread, Materials Science and Reliability.

Case in point:
Fresh rebuild of a 600 cubic inch Big Block Chevrolet for X275 drag class, with nitrous oxide as a "power adder".
Billet crank passed magnaflux,
Ran great on dyno, WAY over 1000 bhp,
2 passes at the strip, starts to run "weird",
Out of the car, back for inspection,
When front of crank is rotated, rear crank hub remains stationary . . . . . . . .

Talk to other racers, see who is having this problem, and use a different supplier.

Cheers
 

tabsracer

Crazy about Datsuns
Steve,

In order:

Mark, what is the other option?
The other option is a "standard style BMC" billet crankshaft. Made from EN40B or equivalent and properly nitrided.

Are those Ghost main cranks billet?
Yes.

If a billet crank is failing where do you go for a quality BMC crank?
To a specialty crank manufacturer who is NOT experiencing these failures. Not sure who those are. Plus, keep in mind that eventually, EVERY HIGHLY STRESSED INLINE 4 CYLINDER CRANKSHAFT WILL FAIL. There is no such thing as a "failure proof" part. Re-read posting #21 on this thread, Materials Science and Reliability.

Case in point:
Fresh rebuild of a 600 cubic inch Big Block Chevrolet for X275 drag class, with nitrous oxide as a "power adder".
Billet crank passed magnaflux,
Ran great on dyno, WAY over 1000 bhp,
2 passes at the strip, starts to run "weird",
Out of the car, back for inspection,
When front of crank is rotated, rear crank hub remains stationary . . . . . . . .

Talk to other racers, see who is having this problem, and use a different supplier.

Cheers
Mark,
Thanks for the response. Let's assume the Ghost Main crank isn't failing? Has anybody gotten more power from this set up because they can run higher RPM?
Obviously if the part doesn't have advantages over a standard billet part then there is no reason to use it unless you like to say GHOST main crank is in my engine.lol It is a catchy name for sure.
 

fordboy628

Moderator
Staff member
Mark,
Thanks for the response. Let's assume the Ghost Main crank isn't failing? Has anybody gotten more power from this set up because they can run higher RPM?
Obviously if the part doesn't have advantages over a standard billet part then there is no reason to use it unless you like to say GHOST main crank is in my engine.lol It is a catchy name for sure.
Actually, it IS the "ghost main" crankshafts that are failing at a higher rate than the standard types. I don't have enough data, at this time, to nail down the exact causative factor.

Except for this one issue:
MANY, if not all, "ghost main" cranks are being used in service without a vibration damper. On the other hand, most of the stock and std billet type cranks ARE using some type of vibration damper.

The supposed "extra stiffness" of the "ghost main" cranks was supposed to allow usage of that type of crank without the "weight penalty" of the vibration damper . . . . . There is some confusion here, gross mass Vs "moment of inertia".

My experience is that rotating mass, (especially on a small radius), has less consequence than reciprocating mass, in terms of engine acceleration.

One thing I am sure of though, is that the reason(s) for these failures will be more complex than one issue alone.

Caveat emptor
 

fordboy628

Moderator
Staff member
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 . . . . .

43

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
 
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