You get what you pay for -cracks!

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JT68
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You get what you pay for -cracks!

Post by JT68 »

A 311 buddy asked us to elaborate on exactly where the cast roadster pistons crack. It is almost always the same place. A picture is worth a 1000 words, so here is about 5000:
crack3.jpeg
crack2.jpeg
crack1.jpeg
crack4.jpeg
crack5.jpeg
Note those are 5 different pistons, from 2 sets, so it's not an anomaly. These cracks locations are specific to the OEM roadster 2L and 1600 design-and obviously any aftermarket piston that copies the design specifically. From an engineering perspective it's a fundamentally flawed design.
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LT/JT
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devauxmidwest
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Model: 2000
Year: High Windshield-68-70

Re: You get what you pay for -cracks!

Post by devauxmidwest »

Ouch...
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redroadster
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Re: You get what you pay for -cracks!

Post by redroadster »

Detonation a possibility back in their day
It at least had 94 octane
Also decelerating on 20w50 cold
JT68
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Joined: Sun Jan 27, 2013 9:43 am
Location: Cumming, GA

Re: You get what you pay for -cracks!

Post by JT68 »

Agree, detonation would be the nail in the coffin, but it's really a design issue. All the R,H,U cast pistons crack. Lots of better engineered AL pistons never crack.

One of the (many) problems is the difference in thermal expansion between the steel pin reinforcement and the casting. The aluminum expands at a much higher rate and degree than the steel, so the joint is always under internal stress. Literally every time it goes through thermal cycles.

A good analogy is bonding fiberglass to steel body panels, a few thousand days in the sun, they will crack every time. It's just a matter of time and physics always prevails.
LT/JT
Datsunrestorationproducts.com
Only the very BEST parts for your Datsun- 10000's of items in stock