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December 16, 2017, 08:18:59 PM
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   Author  Topic: 1970 292 rebuild  (Read 141 times)
GaWajn
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1970 292 rebuild
« on: October 2, 2017, 09:07:38 AM »
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OK ... so a friend of mine wants to rebuild a 1970 292 for his Black Dot project. I get the engine and tear it apart. The bottom end is toast. It had spun the bearing in the case quite badly ... it has sheared the woodruff key ... been welded up and ground anew ... very badly ... so I tell him to find a 1971 Elan bottom end and he will be good to go.

The problem with this engine is really the top end. There was a Wiseco TNT piston in it that measures to about 75.75mm. Would this be correct? Anyone have info on this?

The cylinder measured to about 76.1mm and needs to be bored to 76.5mm to be ably to clean it up nicely.

I have seen information that states that people have been using Oly pistons for the larger rebores. The problem I am seeing is that the Oly pistons I have in my stock have non centered transfer ports. The Elan/TNT crankcase from the original has straight transfer ports.

Does anyone know of a 76.5mm first over Oly piston that has straight transfer ports?
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1970 Ski Doo TNT 292 Bogie (Restored)
1974 Ski Doo Elan (Habs - custom)
mikesskidoo
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Re:1970 292 rebuild
« Reply #1 on: October 2, 2017, 11:41:26 AM »
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oly pistons have the angled cut out, will work just fine on the tnt engines! the 71-72 292 used the angled cut out anyway. not a big deal IMHO    you can also use a 70' 640 blizzard piston, they are the square cut out on the skirt, the wiseco versions of these seem to be pretty easy to find.
« Last Edit: October 2, 2017, 12:46:41 PM by mikesskidoo » Report to moderator Logged
Bones
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Re:1970 292 rebuild
« Reply #2 on: October 2, 2017, 08:10:33 PM »
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Quote from: GaWajn on October  2, 2017, 09:07:38 AM   


Does anyone know of a 76.5mm first over Oly piston that has straight transfer ports?

Well it just so happens I doo know of that piston 
Snomax 17732 starts at 76 mm and goes to 79 mm.
It is the exact same piston dimension as a 67/70 - 292 other than it has 2 "R" rings.
I believe Mikes is correct, you can use the angled window pistons with great results....... The 71 - 292 cylinder has the transfers more toward the exhaust side like the 72 engine has, uses the 72 style piston, but, the sleeve in the 71 jug is actually the same as the 70 sleeve / centered windows 
Also as Mikes says, a 640 Blizzard piston is fine, but, it has the higher crown like the 71/72 pistons so if using a 640 Blizzard piston you will need a 71/72 - 292 head or use two head gaskets or something as the Blizzard piston with stock gaskets will hit a 70 head.
Bones
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