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Post by davejohansen on Mar 1, 2007 14:24:43 GMT -5
For my bus I'm going to build a new engine from the case up. How much does a stock case need to be clearanced to handle a 76mm crank. I see some cases as stock and other stated clearance for a 86mm crank. Do I need the clearanced case or can a new stock case handle the 76mm crank? Also, what is a "flanged crank" that requires additional machining?
Dave
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Post by riffraff on Mar 1, 2007 15:18:20 GMT -5
A stock case MAY be able to take a 74mm crank without clearancing. For a 76, you will need to clearance.
The flanged crank sounds like it may be wedge mated?
If so, it is a taper machined into both crank and flywheel so that there is a tapered mating surface similar to a tie rod end. It is much stronger, but not required unless you plan to push serious HP and launch off the start lines for the 1/4 mile.
(I always wondered why they don't machine splines or Woodruf keys into them??)
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Post by davejohansen on Mar 1, 2007 17:16:00 GMT -5
I guess there isn't much cost difference it seems for a extra clearance to the bigger crank size (about $65) rather than trying to have another case machined. I take it a crank like the 4140 forged crank isn't a flanged type www.cip1.ca/ProductDetails.asp?ProductCode=C13%2D8122Dave |
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Post by bullyboy on Mar 1, 2007 19:46:43 GMT -5
Just make sure to buy the full flow oiling option ;D filtered oil is a good thing  There would be minimal clearancing with the 74 or 76. An 8 dowel crank is fine unless you want your breadbox to do wheel stands  Just buy the best quality crank you can afford. Its probably the hardest working part in your motor. Besides, do you want a cheap crank you have to send to the machine shop to have polished and journals resized? Balancing is another thing to consider. Lloyd at Lethbridge Engine Rebuilders is the only person the hot rod guys in town recommend in Southern Alberta. Cost me $200, done in one day. Balanced to 7000 rpm. I just have to make sure I pop the 3000rpm pill in the MSD when Dorinda is driving it  yuk yuk yuk |
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Post by rareair on Mar 2, 2007 19:30:18 GMT -5
A flanged crank is different then a wedgemated dowelled one. The flanged crank uses a flange just like the T4 that uses bolts to hold the flywheel on. Not necc. for a small stroker like a 76mm one.
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Post by davejohansen on Mar 5, 2007 19:49:44 GMT -5
Okay, now a question about the pistons. I was planning to go with 90.5 x 76mm stroke based on a suggestion to me. When shopping for pistons, must they be specific to the 76mm stroke? I haven't come across anything on the net where they list that combination. I've found pistons for the 69mm stroke or 82mm stroke. Is there any difference?
Dave
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Post by dpeters81westy on Mar 5, 2007 20:48:30 GMT -5
I'm looking for more information on this subject too...
My brother's 69 CW crank is toast...and he's looking into a stroker crank but doesn't want to replace his current pistons.
- Doug
Guys like Trevor will have some answers to this...and Riff Raff knows what it's like to have a garage full of drag racers giving advice on engine part combinations... heh heh heh..
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Post by bullyboy on Mar 5, 2007 23:58:16 GMT -5
90.5 x 69 = "A" piston
90.5 x 76 with A piston = need barrel spacers
90.5 x 82 = "B" piston
90.5 x 76 with B piston = choose rod length carefully ;D
Difference between A and B pistons:
wrist pin is located higher in the piston body to compensate for the longer stroke of the crank.
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Post by riffraff on Mar 6, 2007 10:04:28 GMT -5
Yep, a garage full of drag racers can be a little overwhelming!! I am significantly more schooled in the inner workings of the drag racers mind now though!!! |
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Post by riffraff on Mar 6, 2007 20:37:44 GMT -5
BTW - my understanding is that 74mm stroke is the longest you can use with "A" P&C's
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Post by rareair on Mar 6, 2007 23:18:12 GMT -5
I am significantly more schooled in the inner workings of the drag racers mind now though!!! It's a scary place,... aint it!? (insert evil laugh) ;D |
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Post by bullyboy on Mar 7, 2007 1:06:33 GMT -5
Lots of 90.5 x 76 combo's on the CLF. It just depends on how much farting around you want to do. But anything beyond 1600cc is gonna take some thinking and some research into a good combo of internals for your application. I selected my piston size / stroke and then went to K-Roc and asked for heads and what he recommended for a good combo that worked for my application. He filled in the rest |
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