First off, I'm not doing this. This question has to do with what a mechanic told a friend who is getting his 302 rebuilt. It goes like this.

His truck is a 1987 F-150 auto 2wd. He's having the motor rebuilt. The pistons will be .060 over. The mechanic told him that with the increased displacement the truck will not run right because the computer is set up for 302 cubes, not 302 plus .060. Therefore he is recommending going with a carb.

I told him that I never heard that one before but I would ask around about it. Also told him that I don't believe it and don't think it's a good idea.

Question is....anybody ever heard of something like this?

 

A 60 thousandths overbore will do absolutely little to nothing and a carb swap wont make any difference. Your good to do either carb or stay efi.

 

Worst case scenario, he can use an IAC bypass plate. This will allow more air into the engine at idle.

 

A 302 bored over .060 will be a 310 essentially. It's barely worth noting. If he is going to spend the money to convert to carb then why not just spend the money to retrofit the EFI with bigger injectors and a custom computer. I doubt you'd even need to do it until you get into the 350hp range.

It should also be mentioned that its not the greatest idea to with that big of a piston on a 302. It has been done and will be done again, but a .040 is probably the biggest I would go with if I wanted it to last.

 

The mechanic is wrong, and giving illegal advice. Any vehicle anywhere (regardless of local emissions laws or inspections) with any original emissions components (especially the entire engine management system) removed or disabled is illegal to operate on any public road.

Reman engines run perfectly fine with their original EFI systems intact & unmodified. 0.060" is about 3% increase in displacement, and an even-smaller change in compression. Even the early EEC-IV system can adapt to that.