Author Topic: Factory Freaks.  (Read 2486 times)

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Offline motorhead

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Factory Freaks.
« on: September 21 2016, 02:41:23 PM »
We haven't had a good BS session in a while.

I've been reading a lot about factory parts variances/manufacturing tolerances lately.  The subject also came up in some Youtube videos and even during Drag Week.

It is interesting to hear that there are some pretty wide and acceptable ranges that will pass QC testing for the Big 3.  Without going too far into it, my brother is a production engineer and does the validation for production line machinery.  But, the kinds of things that slip through would astound some people.  I am not just talking about casting, core shift or minor machining issues - rather things like cranks and cams ground with variables that would enhance or detract from vehicle performance.

I believe this is where certain cars out perform their assembly line sibilings simply because of a combination of the "right parts built wrong" coming together.  Some of the discussions I have seen include cranks being ground off enough to impact where TDC lies, and then you can compound this with cams that are also ground a few degrees off; next thing you know you either have a dog or a racehorse in factory stock trim because suddenly the stock fuel/timing/airflow tables are less conservative.

Obviously this is where things like blueprinting or parts-bin hunting for 1-in-100 components that have favourable specs that can give a performance advantage in classes which require stock parts/part numbers.

I know in the case of the LS1 that came in our '02 Camaro, it had an LS6 block with better bank to bank breathing - which is worth an estimated 10hp over a standard LS1 block.  But, this was simply a question of circumstance as the LS6 blocks were substituted as the LS1 blocks were unavailable (no real method to employing them).  Regardless, we ended up with a very strong running car.

Anywho, we have seen this time and again where some cars just run harder than others right off the showroom floor.
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Offline TexasT

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Re: Factory Freaks.
« Reply #1 on: September 21 2016, 02:54:21 PM »
Just the amount the pistons are"in the hole" vs zero deck makes a pretty big difference. The crank, how it is ground, the rod, the piston compression height and difference on block deck height. I'm sure your brother calculates for a worst case scenario so the piston cant hit the valves. This can mean that piston is way down and the Cr isn't anywhere near advertized. They aren't building one like we do. They have to build thousands on an assembly line and I'm sure not one of the people assembling them could care less about how it performs. They are daydreaming about the 420 break or something else.

This is why those stock engines that run so well unopened are so rare.
The blueprint means a lot of different things to a lot of different builders. And it is hard to explain  even to some car people why measuring and checking all the aspects is so important. A lot of people cam put an engine, transmission and rear end together but not near as many get it together and adjusted/tuned so it runs well. With the advent of computer and computer control it adds a whole new wrinkle.
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Offline daveismissing

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Re: Factory Freaks.
« Reply #2 on: September 21 2016, 03:24:54 PM »
Aren't the parts measured and binned (computer time costs nothing) then matched up during assembly so the offsets cancel as much as possible?
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Offline motorhead

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Re: Factory Freaks.
« Reply #3 on: September 21 2016, 03:52:37 PM »
Aren't the parts measured and binned (computer time costs nothing) then matched up during assembly so the offsets cancel as much as possible?

I have a childhood friend who is management at the engine plant in St. Kitts; I should ask him about this.  But, I doubt it.  Chances are that if it is in the bin, it is good to go.  The speed at which these things are churned out is pretty alarmining - the 80% solution is still very profitable.

There were the ringer muscle cars from the factory in the 60s/70s; Ferrari sends a team of techs with their flagship cars to ensure optimized performance.  I just get the impression that the 1 in a thousand cars require a little examination.
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Offline earlbrown

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Re: Factory Freaks.
« Reply #4 on: September 21 2016, 04:31:21 PM »
This was a big deal back when I was racing motorcycles.   The rules for productions based engine got a little gray...

Mr. Manager at Honda could walk back in the back and alter the length of the rods to the long side of spec, grab a couple hundred for the race team, then put the program back to middle of spec.

Make the deck height a little shorter, then the compression height a little bigger, the cam lobes a little taller...

It was against the spirit of the rules but technically 'legal' production parts.
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Offline Charlief1

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Re: Factory Freaks.
« Reply #5 on: September 21 2016, 05:14:36 PM »
Years ago I was on an FF1600 racing team. The engine was the Ford cortina 4 cylinder and we had very tight specs that the engine was built to. No after market heads but there was 1 spec intake we could use. We bought 20 intakes and flowed all of them so we could find the one with the best flow. The headers were the same way. The carb was the Holley Weber progressive 2 barrel and it had no restrictions except that the venturies couldn't be modified, of course, everything else was. :player:
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