I am looking at a 1986 F-150 4x4 with either a 289 or a 302 in it. The truck origionaly had a 300-6 in it. The dealer said that the truck needed a new harmonic balancer. How tough is it to replace one of these? Will it hurt to drive the truck home without fixing it? I live about 1.5 miles from the dealership. Also, while i have your attention...how can i tell which engine i have? All the stickers under the hood say 4.9L. Thanks for your help.

Jon

 

It's fairly easy to replace if you have a puller. Remove your belts and the pulley (4 bolts) and also the bolt into the crank. You will probably also need to remove the fan shroud. If you're lucky you might have enough space to do the change without pulling the rad. While you have it out, you might consider replacing the seal in the timing cover while you can get at it.

The 302 and the 289 used the same block. The only way to tell the difference externally is by the casting number (above the starter) I think the 302 came out in 68 so if the number starts with C8 or has a D for the first digit it most likely is a 302. I think the 289 and the first 302's also had only 3 bolts for the crank pulley but I'm not sure.


1979 F150 Custom: 75 351W, Edelbrock & Holley
1987 F150 XLT Lariat: 88 351W EFI
Chevy 454: waiting for a truck (Mazda?Nissan?)

 

You need to know specifically what crank you have. 302's underwent a major balance change between 81-82. The newer 5.0 cranks have one piece rear main seal and a much different balance offset than the older 302s. I know you can make a 289 or 302 out of the same block, but I read recently that there are actually some differences between original 289 blocks and 302 blocks. I understand that you can't interchange the newer cranks in the older blocks w/ 2piece rear main seal, so if the block casting is pre 81 you probably have the older 302 balance. If you look at the part of your balancer that has the offset weight, it should be obvious comparing a new balancer because the change in weighting is significant between the two types.... the flywheel/flexplate also has offset external weighting, and on them, the difference is 28oz..... older pre 81 and 50oz newer 5.O As far as telling a 289 from an older 302, I'm not sure.... the 302 has 3"stroke the 289 is 2.87". Are you aware that in the late 70's early 80's that there was another member of the smallblock family that looks virtually identical? the 255 or 4.2L? It is like a 302 w/ 3" stroke, but w/ a reduced 3.68" bore instead of 4". Finding a casting number and date code on block would probably narrow it down so you know what you have.

BBT

 

Thanks for y'alls replies...they were very informative...but i think that i'll pass on this truck. It seems a little rough for me and i was going to use it as a beater...