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525 knocking after rebuild

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Here's one for ya. I just replaced the stock piston for a wiseco 12.5 high compression piston. After firing it up for the first time, everything sounds good and responds well except for a loud knocking noise coming from the engine. I can't tell exactly where it comes from but it's pretty loud. At first I was worried that the piston was knocking against the valves but I'm positive that the timing is correct. My theorys are that it could be pre-firing due to the high compression ( I used premium gas 91) or possibly I didn't set the valves right. With a 12.5 compression, do I need to run race gas or octane boost? If I did set the timing wrong or slightly off I'm sure it would make a lot more noise than this. Just want to know what to check first before I start tearing it apart again.

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I don't know, but did you make sure you have the right head gasket? Id could be piston hitting the gasket if you used a smaller hole 450 gasket.

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I don't know, but did you make sure you have the right head gasket? Id could be piston hitting the gasket if you used a smaller hole 450 gasket.

Omg gravelfreak, I think you might be right. When I got home from work I checked the kit that I bought and it has a few different sized head gaskets. It sucks that I have to take it all apart again to check but it has to be done right. I don't know why I didn't check this first:banghead: Thanks man, I'll let you know if you were right, hopefully there is no damage.

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Thanks my wise friend, you were right. Opened it up and sure enough the gasket is slightly smaller than the one I pulled out. I don't know why when I ordered the kit they would send me 3 different sizes, considering the one I just bought now was almost $50 bucks!!! Thanks again, I'm truely greatful:worthy: P.S. no damage except my ego

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Haha, good to hear! But don't thank me, because I have not (yet) made that mistake myself, but the others who have done and told about it so we all would remember :thumbsup:

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