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Regarding pistons 21253
- Thread starter Aggudabbu
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BlueMax
Jedi Warrior
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If your piston is a 21253 AE/Hepolite it should have a pin height of 1.252” with a 3mm oil control ring with slots behind it, which I have experience to be very good quality piston. This piston can have a possible compression ratio of 10 to 1. To determine your static compression ratio you’ll have to know your bore, stroke, deck height, combustion chamber volume, piston volume and gasket thickness. Your AE/Hepolite is a great piston for street and rally racing, this piston is not for heavy loads and high compression ratios over 10 to 1 or high sustained RPM’s. FYI, a good source for a lot of calculations https://www.rbracing-rsr.com/calculations.htm
OP
Aggudabbu
Senior Member
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Well, the thing is that i'm looking for and have not bought new pistons jet.
And what you're saying is exactly what I've heard but i was wondering if all 21253 are AE/Hepolite (or nural or what they're called now)
and since i found these on ebay https://cgi.ebay.co.uk/Classic-Mini-1275c...=item4aa7dd0fb5
which would be cheeper compared to mini spares
https://www.minispares.com/Product.aspx?ty=pb&pid=37864&title=
but I know minispares are hepolite/nural and wouldn't want to ask the ebay seller since I wouldn't trust that id get a straight answer that's why i'm asking here
And what you're saying is exactly what I've heard but i was wondering if all 21253 are AE/Hepolite (or nural or what they're called now)
and since i found these on ebay https://cgi.ebay.co.uk/Classic-Mini-1275c...=item4aa7dd0fb5
which would be cheeper compared to mini spares
https://www.minispares.com/Product.aspx?ty=pb&pid=37864&title=
but I know minispares are hepolite/nural and wouldn't want to ask the ebay seller since I wouldn't trust that id get a straight answer that's why i'm asking here
Hap Waldrop
Yoda
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I use more of these to build 1275 engine that you can shake a stick at, the 21253 gets it's increased compression ratio from a slighty higer compression height, on virgin 1275 block deck the deck normally with the AE 21253 works out to be about .015". The AE 21253 piston also are built much strudier in the oil contol ring area, meaning less slotting, more material holding the bottom and top of the piston together. These are the pistons I used in both Ray and Drew's motors, I also used them in 11.0 t 1 SCCA limited prep H production race motors when a guy didn't want to budget $900 for fancy piston and ring set up, so they hold up quite well to racing as well.
The 21253 is great little piston, has the same dish as the 21251 just more comp. height, it's a nice way to spend a few more bucks and get a good piston and a CR boost to boot. I highly recommend them. The only exception would be if soneone build a hot rod motor for the stock compression height piston by decking the block, this could make the 21253 stick proud of the block, this is why one would never go the route of making a higher CR engine with lower CR pistons, it will come back to bite you or someone else later.
The 21253 is great little piston, has the same dish as the 21251 just more comp. height, it's a nice way to spend a few more bucks and get a good piston and a CR boost to boot. I highly recommend them. The only exception would be if soneone build a hot rod motor for the stock compression height piston by decking the block, this could make the 21253 stick proud of the block, this is why one would never go the route of making a higher CR engine with lower CR pistons, it will come back to bite you or someone else later.
Spridget64SC
Jedi Trainee
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AE 21253 is a very good piston. Like Hap, I've used these in many LPHP race engines for SCCA. The Hepolite "moniker" is not used much anymore to describe these pistons. I'm not aware of multiple manufacturers using the 21253 designation usless it is a simple "Re-sale" application. There are a few piston manufacturers that may make something an awful lot like the AE product, but they won't "Brand" it the same. AE uses the same basic mold to make a number of piston configurations 21250 through 21253. All use the same crown shape, but different compression heights, ring groove configurations and oil ring groove machining and skirt designs.
AE, which used to be part of the same conglomerate as Payen, Ferodo, Glacier and Vandervell got bought back in the 90's by Federal-Mogul. Because of USA SEC restrictions (where FM is based), they divested various parts of some of these companies. That is why Vandervell bearing have gone through various periods of availability.
I digress. Back to the AE21253 piston. Great piston! Compression height is 1.527" versus the stock of 1.497. So, account for the +0.030" change. Can't just replace in an existing block without check where the ring ridge falls. Also have to factor in compression ratio. Head gaskets can vary nearly 1 cc. Make sure block hasn't been decked or you may need to trim pistons. Make sure you have good little ends on the rods and do the right job pressing the new pistons onto the rods. These are slipper skirt pistons and use a short pin. Alignment, proper lubrication and the right tools go a long way to a successful installation. Stay a bit tight on the piston to wall clearance or you will have larger ring gaps than desired. There are ways to correct, but stick to the clearances stated on the literature in the boxes if doing this for a street engine.
HTH,
Mike Miller
AE, which used to be part of the same conglomerate as Payen, Ferodo, Glacier and Vandervell got bought back in the 90's by Federal-Mogul. Because of USA SEC restrictions (where FM is based), they divested various parts of some of these companies. That is why Vandervell bearing have gone through various periods of availability.
I digress. Back to the AE21253 piston. Great piston! Compression height is 1.527" versus the stock of 1.497. So, account for the +0.030" change. Can't just replace in an existing block without check where the ring ridge falls. Also have to factor in compression ratio. Head gaskets can vary nearly 1 cc. Make sure block hasn't been decked or you may need to trim pistons. Make sure you have good little ends on the rods and do the right job pressing the new pistons onto the rods. These are slipper skirt pistons and use a short pin. Alignment, proper lubrication and the right tools go a long way to a successful installation. Stay a bit tight on the piston to wall clearance or you will have larger ring gaps than desired. There are ways to correct, but stick to the clearances stated on the literature in the boxes if doing this for a street engine.
HTH,
Mike Miller