Just finishing up rebuilding the top end of my 87 D100, was missing and slight back fires out the exaust I came to to conclusion it had to be a burnt valve or a bad lobe on a cam. I took it all down got the heards checked and redone by the local machine shop (pressure checked and magnaflux'd, valve job etc) put a new summit 6900 cam and double roller in, but now I have it all back together but when i turn the crank to find TDC It will not tuen all the way it turns about 180* in either direction then hits something. I loosened the rocker shaft to see if I was hitting a valve. it now spins freely I tightened the drivers side shaft up to see if I could narrow it down any further and it hit that spot and clicked one if the valve springs kind of jumped. I am not sure what went wrong when I put the cam in i know it was lined up the the crank '0' at 12'oclock and the cam at 6'oclock now that I have dug into it further I have found people doing it both at 12 oclock... as in this one
http://www.moparmusclemagazine.com/t...2/viewall.html

 

There is really no difference. A crank turns twice for every time the cam goes around once. That means you have two times the piston is at TDC for every revolution of the cam. One TDCs purpose is compression and one is exhaust. Putting the alignment dots both straight up like that instead of pointing at each other makes those two TDCs switch purposes. The engine doesn't know any different.

Could you have left anything in the cylinder when you put the head on? Could anything have fallen in the spark plug hole? I would pull the head.

 

im positive nothing was left in there i.e a socket, and I highly doubt anything fell in through th spark plug holes I had them plugged up until i put the plugs in... could it possibly be a timing cover bolt that is too long? i tried to back the ones out that I thought could cause that problem but no luck... thank you for clarifying the 12-6 or 12-12 oclock "problem" though! is it possible the distributor gear could be binding I primed the oil pump then dropped the gear in but had a hard time telling if it was in the pump and correctly meshed with the cam? I really want to try to eliminate some other things before I pull the intake and heads off... again.

 

Make sure the push rods are in the lifters correctly and not catching the edge of one. which could cause much more lift makeing the valve hit the piston.

Dave

 

Dave you had me excited because that sounded exactly like what could cause that especially with the spring 'jump' like the rod snapping into the lifter/rocker, i went and checked immediately but no success its dark here though and i will triple check tomorrow morning. I will also pull my rockers/shaft all the way off and see if I can get a full revolution as of now it only will turn 180* before stopping, thanks again for everyones help

 

this may be a dumb question but I soaked my hydraulic lifters for a few hours then primed my oil pump running it at 65, i dont know if this would pump the lifters too full of oil causing them to keep the valve open too long or too far?

 

You can't pump a lifter too full. You can get trash in them and have them bind up. Did you reuse the old valves, lifters, or the push rods or are they all new?

I don't believe you could get the distributor to seat correctly if the drive gear was not seated properly. If the distributor drive gear were binding you couldn't turn the engine over at all. You can install the drive gear in the wrong position so that the distributor rotor will not point to where all of the books say it should. The slot in the drive gear should be aligned with the #1 cylinder, in other words it should point at the #1 cylinder.

Did you remove the rocker arms from the rocker shaft at any time? If so could you have reversed the intake and exhaust rockers? They are different. This would cause binding and bent push rods. This might also stop the push rods from seating in the lifters properly or at all.

 

Ok so 'too full' lifters was a dumb question haha. I did replace the lifters and push rods, machine shop checked and reground the valves, the rockers are stamped LH RH, they are in that formation unless they vary from "front of engine" to "rear of engine" they are in the right order.

One thing i did notice was when looking for replacement push rods sum mits website and rockauto had the same push rods, they were label 'w/out hydraulic lifters' which i have. On one of those 2 sites i cannot remember which one I thought I had seen "w/out hydraulic roller lifters" checked the specs and they were the same. And i know they changed to roller lifters soon after mine. but when i got the rods they were thicker around than the originals and the ball on the end looked bigger but i coulnt be sure. I am thinking now this could be my mistake, and the other thing is i already tossed the originals because they were so gummed up, now that i pulled the rocker off and marked it with lube the push rod does not sit all the way into the rocker and It does not seat fully into the bottom of the lifter, probably close to an 1/8 or a little less on each side which would almost be 1/4 of an inch all together.

http://www.summitracing.com/parts/SLP-RP-3194/

these are the pushrods I got (from rockauto.com though)

 

These are pictures I took of the push rods I saved 1 of the originals as you can see the new push rod is quite bigger, I had not noticed it when putting them in, trusting they were the right ones, they are the right length but not the right size/diameter. ? causing them not to seat properly and actually making them "longer" ?

 

I don't believe any question is dumb if you don't know the answer. We are all constantly learning.

I would say you found the problem. Those are solid rods, they don't have lubrication holes for the upper end of the valve train. They would also make the lifters more solid by trapping the oil in the lifter and taking away the lifters shock absorbing quality.

I still believe you will probably have to pull the heads but once the pushrods are replaced you might be able to get away with just doing a compression test to check for damage.