rebuild on 1990 302

[gregor]

I am just starting to rebuild the engine in my 1990 eb (302 efi ). When i removed the heads i noticed that I had two broken pistons /emoticons/[email protected] 2x" width="20" height="20" /> The two that broke were right next to each other and were broke in the exact same spot. I am going to replace all of the pistons but i was wondering if anyone else has seen something like this? I am trying to find a good rebuild kit, if anyone has any info. on any that they used i would really appreciate it.

 

[BLADE262US]

Look closely at the head gasket that was between those 2 cylinders if its blown out . If it is it was allowing the cylinders to crossfire and this is what broke your pistons . If this is the case you will have to have that block decked as the crossfireing will have eroded a grove between the cylinders and you will also have to have the heads milled to ensure a completely flat surface for the new gaskets to seal on . /emoticons/[email protected] 2x" width="20" height="20" />

 

[gregor]

The head gasket was blown, that is why i was taking it apart. When i got the heads off that is when i saw the broke pistons.

 

[BLADE262US]

Then you will have to figure on some extra money to rebuild that block . /emoticons/[email protected] 2x" width="20" height="20" />

 

[fourbybuilder]

have you thought about replaceing the302 with a 351 used 351 should run about same as a good rebuild if not cheaper

 

[Broncoholics]

Most times you can just replace the bad cylinders. If you want, replace all four pistons on the bad side and add new rings and rod bearings. If the cylinder wall isn't scraped up you can go to a rental shop and rent those "little berry" looking things that scuff up the inside cylinder wall with a drill gun for the new rings to seat properly.

If the wall has scrapes you might be able to hone it out or sleeve it. The top of the engine and bottom of the head should be milled down flat.

Make sure you follow the torc specs exactly. Every bolt you take off has a different torc spec. The rod bearings are only like 17# if I remember right. Seems light but thats the torc spec.

 

[BLADE262US]

I would recomend going to a 351 also if you have to rebuild the motor anyway. Just keep in mind that with the fuel injection you absolutely have to change the computer to a 351 computer with whatever tranny you have and you should get the 351 motor harness from the same year as your truck you can use your 302 harness but will have to change a couple pins around and the 302 harness has things you wont use on the 351 like the knock sensor and mine had a power steering pressure sensor I didnt have to use when I changed to the 351 . All of your accesory brackets will work from the 302 to the 351 so your all set there . and you will need the injected 351 intake manifold upper and lower as they are different than the 302 . /emoticons/[email protected] 2x" width="20" height="20" /> Any other questions about the swap feel free to ask .

 

[gregor]

I was wondering how much would the gas mileage change with a 351? $-) I have been thinking about upgrading but if the gas mileage is ot that great then i might not be able to.

 

[BLADE262US]

I havent noticed it being any worse with the 351 than the 302 besides your not driving a bronco for the gas milage . LOL /emoticons/[email protected] 2x" width="20" height="20" />

 

[gregor]

I think that I am going to stick with the 302, the main reason is that I really don't have a lot of money to spare. I found an overhaul kit that comes with: rod bearings, main bearings, ****** washers, cam bearings, pistons, rings, and the gaskets. For the kit the total price is $239. I was wondering if this is a good price or should I keep looking. If I would get this kit is there anything else that I would need? Thanks for the help, >-

 

[Broncoholics]

All depends on how the crank looks when you take off the rod bearings and such.

Look at the valves on the bottom side of each head to make sure they are not showing signs of leaking. The will be recessed up inside instead of being flush. A machine shop can add case hardened valve seats cheaply. Other than that I think you are good to go for that price.

 

[gregor]

I am taking the block to the machine shop this week and I was wondering if I should get it bored over at all? If I do, how much of a difference will it make? Would I notice a change in power? I have never done this kind of thing before so any help will be appreciated.

 

[BLADE262US]

You wont really notice any power difference between a 4.00 block and a 4.030 block if the two were new fresh from the start . What you will notice if you have it bored is an increase in power and a lack of gas milage for awhile till it breaks in from it being tight again . Just like a brand new vehicle the gas milage will be terrible for awhile till it breaks in . /emoticons/[email protected] 2x" width="20" height="20" />