strange sound in engine part ll

[paul cass]

hi everyone
i finally got around to tearing down my daughters engine. for a recap, this is a roller 302 fuel injected for a full size bronco that developed a knocking sound within 3000 miles. it appears that one side of the engine was getting way to much fuel. the drivers side cylinders were pretty clean. however, the passenger side was where the problem was. number 4 was really scuffed up on the bottom side of the cylinder and the piston skirt was worn away. the other side of the piston skirt was just fine. the other 3 cylinders showed some wear but all on the bottom side. the other pistons were ok. there was a lot of carbon build up on the pistons and between the top ring and middle ring on the pistons. my concern is what caused this washing down of the cylinders. the engine did not run hot and had excellent oil pressure.

could it be possible that the problem was with the cam profile? 2 different cam companies sent 2 cams. each company admitted that they sent the wrong cam at first. the second cam wasn't much better. i asked for a cam that would provide low end torque and was very specific that this was for a roller 302 in a full size bronco. i also was very clear that the original engine was a flat tappet 302. the first cam each company sent turned out to be for a mustang. the bronco ran terrible and got lousy fule mileage. even now with the 4th different cam the bronco gets worse mileage than the old 250k got. is it possible that the computer misread the cam and dumped to much fuel into the engine causing the scuffing. its still puzzling why one cylinder was ruined and the other 3 showed signs of wear on one side of the block and all cylinders on the other side are ok. all damage is on the bottom of the cylinder walls. all clearances except for the one bad piston and cylinder are within specs. also the rod bearing show some peculiar spots, like the oil could have been contaminated with fuel. i don't want to build the engine again and have the same problems. most of the parts are new, computer, injectors, etc. i have been told that a cam with less than 200 duration would give the most torque. i was tempted to go back with a motorsport cam but the advertized duration for a bronco is at least 220. hmmmmmmm. any help would be greatly appreciated. these electronic engines are not my cup of tea. if i can i will post pics of the parts. no luck, says that my pics are to big. help!!!!!!!
thanks,
paul
grrrrrrrrrrrrrrrr!

[lovehamr]

Originally Posted by paul cass

is it possible that the computer misread the cam and dumped to much fuel into the engine causing the scuffing.

Paul, to answer your question; yes it could but there's not allot of info to go on here. What year bronco? Is it mass-air or speed-density? You said that it has a new computer; what type and how about O2 sensors? What sort of other mods were done? New injectors? Things like these could change the nature of the beast quite a bit.

Steve

[paul cass]

hi steve
it is an 88 bronco with a throttle body. the computer is new for an 88, and the injectors are new and for a roller 302. they are supposed to be for a bronco, but like the mix up on the cams they may be for a mustang. don't know if there is a difference. o2 sensors are new. no mods to the engine.
paul

[CHANMADD]

If you look at the side of the piston it will be apparent that the piston pin is not located exactly in the middle of the piston. I have had pistons back from machine shops fitted incorrectly on the pins. What happens is more pressure is exerted on one side of the piston and the piston cocks in the bore causing wierd types of wear and the like.

[paul cass]

hi chanmadd
the piston pin is centered. i think the problem is to much fuel. but i'm not sure. i think that one of the cams confused the computer and made the engine run to rich. the first cam caused the bromco to get only 12 mpg on the highway. the next cam improved to 14 and now the last cam is just over 15. the original engine got around 16-17 mpg. will the new original computer that controlled the flat tappet cam work with a roller cam? if someone can contact me via email at fia28950@aol.com i can email the pics of the engine parts. when i tried to load them it said they were to big and i don't know how to downsize them. i'd like to know what to do by monday.
thanks,
paul

[lovehamr]

Paul, it being a 1988 I’m assuming that it doesn't have a mass air meter, right? If this is the case then just about anything you do that alters the amount of air that the engine can digest will negatively affect the way the thing runs. An engine using an open loop fuel injection system uses temp, throttle pos., manifold pres., RPM and a couple of other factors to mathematically figure the pulse width of the injectors based on tables loaded in the computer. If you change the engines requirements w/o changing the injection tables or the system to go along with it, it'll never run right. A "mass-air" system on the other hand uses a measurement device in the intake tract to "measure" the amount of air going into the engine. The computer uses this extra info in an algorithm to alter the air-fuel ratio, spark adv. etc. I know Ford used to market a conversion kit to change over Mustangs from speed density to mass-air but I have no idea about the trucks.

At this point I imagine that no more people are joining inn this discussion just because there is no way that this could be diagnosed over a web site or telephone because so much has been changed. To my limited self it looks like kayos theory! Too many changed factors to take into account. Who knows, maybe that’s the way your computer feels as well!

I would research the computer and engine combos to see what would work together befor I was to proceed.

Steve

Steve

[paul cass]

hi steve
thanks for the reply. the engine is electronic fuel injection with no mention of a mass air meter. the original computer conked out and was replaced with a new one before the installation of the cams. really, all that was changed was the block. went from a flat tappet to a roller 302 block. everything else stayed stock. the only reason i went with an aftermarket cam was to inprove the performance of the vehicle. both cam companies were given all of the info about the engine, tranny, wheels combos. i still think that the first cams that were designed for mustangs caused all of the problems. i guess i'll try ford on monday to see if they can tell me if the current computer will work on a roller motor. i don't see why it shouldn't. i may end up going back with the motorsport cam. anyone know the right number for the cam. when i called the dealer here they listed 4 different cams. go figure. thanks again for the help steve. i'll post once i'm done. have a great weekend.
paul

[paul cass]

i know a little more than i did a week ago. the original engine was controlled by a map sensor. the cams that were sent were ment to be controlled by a mass air flow sensor. now what i'm trying to do is to find a roller cam that is controlled by a map sensor. i know that roller 302's were used starting in 86 and that all were run by map sensors until 93 when they switched to mass air flow. seems that it shouldn't be that hard to find a cam to work in the bronco i've contacted a couple of friends that fool with computer cars and i'm waiting to see what they come up with. tried all kinds of sites on the web but no one seems to know anything-good or bad. we'll see what happens.
paul

[351windsorsnake]

http://sbftech.com/index.php/board,20.0.html
Paul I am sure this guy will sort your problem or at least point you in the right direction