Does it need Bored over?

[WickedShelby88]

Okay I'm about to go gung ho on a 2.5 I have. One block has over 200k on it and was in a bone stock dodge shadow with an auto. The other is an N/A block with a little over 100k. If I hone the bores and use good moly rings wouldn't I be better off time wise to just use the turbo block? This is only going to be a mild engine. Not looking to go over 18 psi boost or push over 300 hp. And with the high mileage should I be weary of not boring it over? I can't really afford to get it bored over right now and buy a new set of pistons. Any suggestions?

[mcsvt]

I would measure the bores to make sure they are still in spec. I bought some bore gauges from Harbor freight and they ended up being fairly accurate. If the bore is within spec, hone and go :thumb:

[shelby zed]

i doubt it will be, but if it is you could use the turbo block and hone it, clean everything up and throw parts at it, one thing though is youll most likely need the crank machined

[mpgmike]

A natural phenomonon that occurs with metal is that it is melted to pour into a casting. The molecules are moving around like scared rabbits then suddenly... freeze frame. There is lack of order, there is stress, and there is chaos in the way these molecules are positioned in relation to each other as the iron solidifies.

Start the engine and it heats up, making it a little easier for the molecules to find a more comfortable position in relation to each other. Do this over 100k to 200k miles with thousands of thermal cycles and the end result is mild distortion. But what you have is a well thermally seasoned block.

Rebuilding a high mileage block will give you a better-than-new engine that will last longer for that reason. In the big race field, the builder will take a brand new block and have it thermally seasoned (a heat treating process) before machining and building. This reduces the amount of distortion the block undergoes as it heats and cools, and lasts many more races between rebuilds.

For a mild application rebuilding the stock block with stock bore is fine. I do it all the time. For a long term serious minded project, re-machining everything will compensate for the thermal distortion that naturally occurs over thermal cycles and give you that better-than-new engine.

Mike

[Rattlesnake]

MPGmike is absolutelly right! Also, during machining heat is transfered to the casting causing upsetting of molecules. After machining is done I usually get my parts cryo treated. This type of heat treatment(yes, cryo is part of the heat threating processes) will re-posicion the scattered molecules giving the piece a stronger molecular structure.

Reinaldo Moloon

[WickedShelby88]

Since this engine may be coming back apart again sometime in the near future I will just leave it stock for now. Its going to be more of a daily driver so if stock will do for now I will go with that. As far as my shelby charger project is conscerned I will go all out. Thanks for the advice guys. At least now I have more of an idea as to what steps to take to ensure the engine holds up better.