Short Block Rebuild Advice
Discussion
Gents, I would appreciate some advice on engine building!
I recently purchased a Mitsubishi GTO (3 litre V6 Twin Turbo) with the engine all dismantled and in various boxes.
This will be my first engine build and therefore I want to keep it standard. I have two blocks, each with a full set of pistons+con-rods. One set of pistons has suffered a spun bearing (ie con-rod wrecked) and the other has had two piston lands break up. The blocks themselves seem OK. I want to end up with one good set of pistons and a matching block.
In one block the six pistons are embossed with a code 72T, the associated con-rods coded 72L and the caps coded 72V. In the other block the pistons are 72N, con-rods 72V and caps 72S. Obviously these codes must be associated with either mass or geometry but it seems nobody on the GTO forums knows anything more than this.
My first thoughts are to use the undamaged pistons and associated block and swap the con-rods across from the other set of pistons. However, this means separating 12 con-rods from their pistions. Is this strictly necessary? Also do you think the block will be coded somewhere corrsponding to the individual pistons?
Of course I will be honing the block, replacing piston rings and bearings etc but I don't want to spend cash on new pistons etc (maybe next time when I know what I'm doing! )
Any help appreciated. Cheers, Robert.
>> Edited by jap-car on Saturday 21st January 00:00
I recently purchased a Mitsubishi GTO (3 litre V6 Twin Turbo) with the engine all dismantled and in various boxes.
This will be my first engine build and therefore I want to keep it standard. I have two blocks, each with a full set of pistons+con-rods. One set of pistons has suffered a spun bearing (ie con-rod wrecked) and the other has had two piston lands break up. The blocks themselves seem OK. I want to end up with one good set of pistons and a matching block.
In one block the six pistons are embossed with a code 72T, the associated con-rods coded 72L and the caps coded 72V. In the other block the pistons are 72N, con-rods 72V and caps 72S. Obviously these codes must be associated with either mass or geometry but it seems nobody on the GTO forums knows anything more than this.
My first thoughts are to use the undamaged pistons and associated block and swap the con-rods across from the other set of pistons. However, this means separating 12 con-rods from their pistions. Is this strictly necessary? Also do you think the block will be coded somewhere corrsponding to the individual pistons?
Of course I will be honing the block, replacing piston rings and bearings etc but I don't want to spend cash on new pistons etc (maybe next time when I know what I'm doing! )
Any help appreciated. Cheers, Robert.
>> Edited by jap-car on Saturday 21st January 00:00
Best thing to do is a trial assembly with no piston rings of the two types of rod / piston assemblies into your block of choice, turn the crank over and check for any mismatch of stroke or crankcase clearance of distance of the piston protruding in out of the block if they both match up and use the same shells and are the same width across the big ends then you should be OK. Other things to watch for is some piston / rod assy's are handed, or have to face a certain way and also piston to bore clearance which can be roughly checked by rocking the piston in the bore and comparing with the other, ideally you'd have all components properly measured to be certain.
Best of luck
Matt
Best of luck
Matt
As Matt said assemble one of each rod/piston set into a block.
The most likely reason you have different code numbers is that one of the engines was a different compression ratio.
This may be achieved with different rod lengths or more likely the height of the piston above the gudgeon pin will be different (easily measured).
Steve
The most likely reason you have different code numbers is that one of the engines was a different compression ratio.
This may be achieved with different rod lengths or more likely the height of the piston above the gudgeon pin will be different (easily measured).
Steve
Hi, thanks for all the replies. I'm going to clean up the blocks and pistons tomorrow so I will try checking out some of the items you've mentioned. I don't think the variations can be down to comression ratio as they are nominally from the same type of engine. Also I have another two pistons+con-rods from yet another engine they again have differing codes.
I'll let you know what I find - thanks.
I'll let you know what I find - thanks.
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