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Old 08-03-2018, 01:12 PM   #1
92smokeaccord
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Arias piston and bisi rods question or Two.....

So long ago...(about 6 years or so) I acquired a Bisimoto piston and long rod setup. Long story on that short is piston went bad and now Iím using the bisi rods with the arias shelf Piston for the f22a. I noticed that my pistons pop out the bore hole at tdc. I never noticed this on the old set up. Are they supposed to do that and if so any body know how many thousands they are supposed to? To give a idea of how much they pop out, you can rub your fingernail over it and clearly catch the lip. If I had to put a number on it Iíd say itís about 15-20 thousands.
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Old 08-21-2018, 01:57 AM   #2
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sometimes they will, but you wanna make sure that you have the piston to head clearance. you will want a minimum of .040"-.050". you can make that up with a head gasket. or have them shave the top of the piston. or have a piston relief bored into the head.
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Old 08-21-2018, 04:46 AM   #3
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It may state the clearances on their site and recommend how much to shave? (for an OEM f22 setup)
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Old 08-21-2018, 01:07 PM   #4
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You cannot use those pistons with your rod set up. If you increase the length of the rods, then a piston will naturally protrude from the bore, right? So the piston needs to be shorter than standard to compensate for the added length of the rod.

When Bisi "developed" this kit, all he did was take a combination that had been tried by a few enthusiasts already and passed it off as his own version of online college engineering. He's using H22A rods which use the same big end and wrist pin bearing dimensions, only that are 143mm vs. the F22A/H23A1 141.5mm. That will net a 1.51 r/s ratio vs. the standard 1.49. Not huge, but it's an improvement. The benefit of that rod is that it's already available from the OEMs, as well as the aftermarket. In Bisi's case, he just purchased Chinese rods for the H22A and touted them as his own. In defense of the rods, the fact that they are Chinese rods hasn't seemed to negatively effect too many people. Many people have put big power on them in many different types of applications, and you just don't hear about premature failures on them.

The pistons are a shelf item made for DSM applications with 100mm strokes. They are a 28.7mm compression height, if I remember correctly.

So, if you have an existing rod/piston combo height of 172mm (141.5mm rod length plus 30.5mm compression height), and you add 1.5mm to the rod length, then your pistons are now 1.5mm too tall. You cannot use OEM-spec F22 pistons for this application. You need shorter pistons.
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Old 08-22-2018, 07:56 AM   #5
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This would be a good set of pistons to buy. I don't know what your cylinder walls look like, or what the machine shop who bored it to fit the 86mm Bisi pistons set the P2W clearances at, but it's a start.

These pistons have around a -4.45cc dish that could calc to around a 10.2:1 CR in the long rod F22A application.
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