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Discussion Starter #1 (Edited)
Hi All,

As I am new to this forum, please be gentle :blabla::blabla:
I am guessing this topic was already discussed but I haven't found it, so i am opening a new post.

I have a 1.5 dual carb, 1992 33 and I'm thinking about putting a 1.7 crank in it to make it a 1.6 and have a few questions:
1. What r the main advantages of it? torque at low end?
2. if i do this what else do I need to change? the main bearings r the same? the rod bearings r the same? what about the head gasket?

I've seen a lot of posts of people who did the opposite - putting a 1.5 crank in a 1.7 block, but her a 1.7 block is rare, so it's not an option for me...

Thanks in advance
 

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Apart from the question of whether the 1.5 block has clearance for a 1.7 crank to swing (I'm not sure it does), the other main difficulty is sourcing pistons with the gudgeon pin hole higher up the piston so it doesn't attempt to punch a hole through the head.
 

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Discussion Starter #3
Apart from the question of whether the 1.5 block has clearance for a 1.7 crank to swing (I'm not sure it does), the other main difficulty is sourcing pistons with the gudgeon pin hole higher up the piston so it doesn't attempt to punch a hole through the head.
From what i've read the clearance is not enough and will have to machined. less of a problem for me.
Regarding the pistons... y do I need to source new pistons? the TDC will be higher now??

One more thing, i've read somewhere that the 1.7 crank has a problematic oiling setup and is much more prone to damage than the 1.5 crank. is this right??
 

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Discussion Starter #5
I can help you with 84 mm pistons( 1500) suitable for 72 mm crank (1700).

Ali
Thanks!!
I would like to make sure first that the 1.7 crank doesn't have an oiling issue before i decide on this setup.
Apart from the pistons what else do I need to change? which main bearings and rod bearings I use? which head gasket?
 

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Other than the stroke I can't think of any difference between a 105hp 1500 crank and a early 1700 8v crank. They were both cross drilled, whereas earlier sud cranks weren't. Some people think drilling out the centre main bearing oil feed helps oil supply to the big end bearings. Only needed for race use though I would think.
 

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Discussion Starter #8
Other than the stroke I can't think of any difference between a 105hp 1500 crank and a early 1700 8v crank. They were both cross drilled, whereas earlier sud cranks weren't. Some people think drilling out the centre main bearing oil feed helps oil supply to the big end bearings. Only needed for race use though I would think.
Thanks for clarifying that point!!!

Regarding the main and rod bearings, I need to use the 1.5 one? the journals r the same size?
 

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Discussion Starter #10 (Edited)
Apart from the question of whether the 1.5 block has clearance for a 1.7 crank to swing (I'm not sure it does), the other main difficulty is sourcing pistons with the gudgeon pin hole higher up the piston so it doesn't attempt to punch a hole through the head.
Can someone please post a picture/link of this pistons so i'll know what to look for?

Thanks
 

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..just an idea..maybe pistons from alfa 145 boxer 1.6 (1.7 crank with pistons reduced at 84mm)..or probably something availale from racing parts..
 

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Discussion Starter #12
..just an idea..maybe pistons from alfa 145 boxer 1.6 (1.7 crank with pistons reduced at 84mm)..or probably something availale from racing parts..
You r asking or saying? I don't know if the head on the 1.5 and the 145 boxer r the same... If they r that's a good idea!!
Anyone knows?
 

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A trustworthy friend of mine from this forum confirmed 33 1.5 and 145/6 1.6 heads are identical and can be swapped. The blocks are identical too. Just that crankshaft stroke is different and 1.6 has lower piston height to not to have pistos smash the heads. And crank journal sizes are same too.

Sent from my SM-J730F using Tapatalk
 

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Is the 145 not a 1700cc block with a 1500 crank? Even so it would need special pistons as the 1500 piston is longer.
We don't get them here, but I doubt Alfa would make special pistons.
Is the 1600cc you refer to not an inline Twinspark motor?
From what I remember only the 1st few 145's had 1700 Alfasud motors.
 
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