221 pistons

I have stripped the 221 completely, it needs pistons as 3 look terminal. As the 221 is kinda a orphan which pistons can I use? Are they 221 only or will 200 pistons work too? Thanks Craig

xpcoupe221":2luzhzei said:

I have stripped the 221 completely, it needs pistons as 3 look terminal. As the 221 is kinda a orphan which pistons can I use? Are they 221 only or will 200 pistons work too? Thanks Craig

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200 pistons work, but the best bet is likely to be Silvolites 3327H, a 8.5 cc dish piston with a chamfered dish with its base 2.967", 71 thou deep, which works out to 8.5 cc. Thats 3 cc's more dish than the piston you have in your 221, if its stock.

All 221's and 188's ran early 200 XM-XP-XR pistons with a 5.5 cc dish about 2" diameter at its base, the stock 200 US piston from 1963 to 1983, listed on Page 30 of the Silvolite pdf catalouge. (No's on pdf files differ depending on how you veiw them, but the page number on the sheet is 30 for the 3327H

The Aussie replacements are from the later XY-XF range from 1971 to 1993. There used to be of many types, from flat top 0 cc, to 8.5 cc, to cross flow pistons, which were 15.5m 22.9 and 27.9 cc. Page 30, 33 and 34 of the Silvolite catalouge shows these Aussie pistons in 0 cc flat top and 8.5 cc form.


Deap dish pistons allow a non cross flow engine to take bigger lift cams, stopping piston contact at lifts above 470 thou at the valve.

Australian experiance says "Don't use slotted oil relief pistons in an I6 your going to accidently over rev, even if they are high silicon".

Sadly, most aftermarket Small six pistons have a fully slotted oil relief. Some people run the 0 cc flat top Tempo Sivolite (was #489p) pistons in the 200 sixes, and do 13.5 second passes in 200 plus hp applications, just like some people here, like Crosley, and Mike1157, run low quality cast iron D8 American rods instead of the better earlier forged conrods that aal Aussie sixes used. Its about good workshop practice, with good machining and attention to detail.

I've seen 10 psi blown 280 hp Holdn Re202 engines ccope with "Rotating assembly comprises a fully polished crankshaft with “blue” connecting rods, ARP bolts, ACL cast pistons (7.7:1 compression ratio) that were ceramic coated and a Ross billet damper modified to accept the 3-inch blower-drive pulley."


If that's all it takes to make an Aussie cast piston live under a setonation prone envirnment like that, then a cast hyper piston should do it for you.


See viewtopic.php?f=1&t=72669&p=559015#p559015

I've seen forged conrods crash through camshafts and cylinder blocks, and the cast pistons with slotted reliefs crack and take out blocks.

Silvolite in the US now makes replacement Aussie pistons which have all the durability tricks learned from the Super Sedan and oval tract racers from the late 60's and 70's, when Ford sixes always kept it together.


viewtopic.php?f=1&t=72474

xctasy":2luzhzei said:

Australian experiance says "Don't use slotted oil relief pistons in an I6 your going to accidently over rev, even if they are high silicon".

Back in the dark ages, Holden XU1 GTR 202 engines got triple CD 175 Strmbergs, 312 degree racing cams, and in 1973, triple DCOE 45's with one barrel taken out, bascially three 45 mm carbs with 40 mm chokes. The engines went from 216 hp to 235 hp flywheel , and pistons (already marginal) then started to fly appart all the time, An ex Ford development engineer Harry Firth remembered Mahale from Germany made slipper skirt cast alloy pistons with drilled oil holes that didn't come apart at 7500 rpm, for the RS2600 Cologne Capri. Through Repco, these High Performance # 9931326 / # 9931327/6KRY 2585 pistons were made. They gave sensational results

See the similarity to the 2800 Colgne pistons.





V4'S, V6's and I6's don't have the same ability to run V8 style pistons...a V8 isn't subject to the torsional vibration an I6 is under, and I6's tend to have harmonic vibrations of a low to medium order that V8's don't . The common I6 cranks aren't really that good, and a piston in an I6 is under different loads to a 90 degree crankpin counterweighted five bearing crank. So the German Mahale based casting became the high performance Holden and Ford 6 in line piston.


The Silvolite cat lists the Aussie 3327H and 3328H hyper flat tops as American made on page 29 and 33. http://www.uempistons.com/catalogs/silv ... atalog.pdf

See http://www.gmh-torana.com.au/forums/top ... 1-pistons/

and another view of the type of piston skirt differences.

Replacement Speed Pro pistons are designed to run with tighter piston-to-wall clearance than typical forged pistons. This is largely due to the slots running the length of the piston, isolating the skirts from the crown (left). The Speed Pro race pistons are much more ridged, with drilled oil-return holes (right), and therefore need to be looser in the bores.

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http://www.hotrod.com/how-to/engine/mop ... z3M3ahKM7n

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I'm not sure what sort of build you a looking for with your 221 but I've just buttoned up the bottom end of my 221 and used Hypatec PFO250FT6 pistons from Precision International. They are hypereutectic flat top's and have a greater compression height at 1.547" compared to most others around 1.500". I then only needed to take .005" from the block deck to get zero deck height, this got me to 11.0:1 compression

Cheers