Well I did a complete engine change from my 1970 f100 short bed and now with the new motor there is excessive vibration. I removed the I6 motor and trans and installed a 302. Also I changed the engine perches since the I6's are different. From the moment the 302 has been running I just can't figure the vibration out. It was sitting running when it came out a 74 grabber 4 years ago but sat in a garage until it went into my truck. We sprayed the cyl, changed some parts and painted it before install. Also it has the old point's system in the distributor in it. I have done compression test, changed point's and now I'm putting in a procomp ready to run distributor The point gap has been set at .017 but not the dwell. So what I'm getting at is that when adjusting the timing by hand the vibration seems to go away but then it is very hard to crank. Also there is a lot of backfire/pop out of the exhaust. I've tried the valve-metic by gunk to see if there was a sticking valve but no change yet. I've been told that the backfire/pop from the exhaust is from the old point's system and go ahead and upgrade. Also I've heard that the harmonic balancer might have shifted or thrown off since it was painted to. Has anyone out there ran into any of these problems. Most of the vibes are at 2000rpm and 3000rpm. Depending on the timing it does it at an idle to. The vibes are when the truck is in park and driving....not sure about this but any ideas would be helpfull

 

Did you use the flywheel from the 302 ? Also take out the #1 spark plug turn the engine by hand and try to determine when th #1 piston is tdc then look at the timing marks to see if they line up on the harmonic balancer. Kenny Nunez

 

Yes we did TDC and timing light with settings from chilton book

 

Which flywheel/flexplate did you use? The 6 is balanced different than the 8.

 

I used the same spacer and flywheel from the 302/c4 trans. I had a c6 in it with the I6 motor and parts where different. So yes I have the 302 fly wheel but only difference is the c6 trans. But I'm gonna double check. Never thought of that

 

So, the flywheel is what was behind the motor originally? That's good. There is two different 302 balances depending on the year. 28 oz and 50 oz.

You say you did a compression check and all the cylinders were about the same? Good?

Timing could cause the popping, but could be a sticky valve too. Advancing the timing will make it hard to crank(it is trying to fire before the piston gets to top dead center).

Might want to pull valve covers and watch rockers to see if one is hanging up. Put your finger on the tip and "feel" it move. You'll notice if it is "jumpy" or smooth. I don't put alot of faith in those magical "fix all" additives. They usually don't work instantly.

Have you rechecked your firing order?? That will also cause a pop out the exhaust if it tries firing a hole when the exhaust valve is open. There is two different firing orders depending on new/old small blocks.

 

I've checked firing order about six times now with the chilton manual. Everything is good there but I just might have used the I6 flywheel because of the bigger c6 trans... I can't remember so I'm waiting on my cousin to call me back??? I think I might have used the i6 because it fit the bell housing and starter. I will check and get back to you. Thanks

 

Ok, we did use the same fly wheel from the 300 I6 on the 302. I called napa and advance and they are different part numbers that year. It makes sence of why I would have a vibration. From what I have read is that the I6 fly wheel/flexplate was internally balanced and the 302 was externally balanced. So then comes the new problem Which fly wheel/flexplate do I use. I read that up 1982 it was balanced at 28oz and after 82 they went with a 50oz fly wheel. I'm still not sure where to go with this so hopefully you guys can recommend what fly wheel to use. The motor is a jasper and came out of a 1974 mavrick/grabber with a c4 auto but I'm using the C6 auto now in the truck. Hopefully changing the flywheel will take care of the vibes. Also is there a certain way to mount the fly wheel ???? There are no keys but maybe some way to line it up from the balancer or dosen't it matter? Thanks guys

 

The bolt pattern for the flywheel is slightly offset so that the flywheel can only go on one way. Hopefully you still have the 302 flywheel , you probably have the earlier version of the 302. Jasper is pretty good about suppling the correct engine for the application. Good Luck, Kenny Nunez.

 

I ran Procomp Electronic distributor in my mopar it sucked. It would not hold the set time for the engine then it just blew apart. I have one for my 390 but will not run it, You may have done nothing wrong - just bad part

 

sorry did not red the rest of your post backfire/pop sounds like timing. the whole 28oz and 50oz fly wheel thing is when ford started the roller engine in the 80's If you don't have an "HO" Eng and you have a 70's c4 it's prob going to be the early fly wheel. If it is the flywheel it will idle horribly and there will be a vibration threw all the rpm but it will smooth out some. Its Mechanical because it bolted to the engine. The will always be off balance it wont go away only change.Sounds like you have more of a "on off problem" like timing
new here
hope it helps some

 

i had a vibration in my 302 as well. i took out an old 302..put in another one. my truck is a standard. the engine came out of an automatic. i ended up with a vibration. i blamed it on the changing of the flywheel and the balancer. i solved this problem by buying a med. sized "L" bracket. i put in the vise, bent it around to make a kind of circle at one end....then i put a bolt and nut through the circle, simulating weight. then on the front crank pulley...the four bolts holding the pulley on.....i took off one bolt..put on this counter-weight...bolted it on...started her up......checked how bad/good the vibration was.....if it was worse....i put the counterweight onto the next bolt.....aftere my third bolt....it was gone...!!....my dash board doesn't vibrate no more...hope this helps.

 

i am new on thios site. i figured out how to reply to other peoples troubles...but how do i add a question for myself.....???

 

Go to the year type truck and post a thread. It took me a bit to figure it out to. Add me as a friend on here if you like

 

It was the flywheel. I used the One off the I6 which has no weight and the 78 motor called for a 28oz balanced flywheel. It work out perfectly. Thanks for the input though