Thread: adjusting valves on a 302

Tweet

hi, got a problem with my 69 302, its got the 5/16 studs for the rocker arms, and i ran into a problem, engine was rebuilt not too long ago and i pulled it from the car i had it in to put it in my 66 mustang, while the engine was out, my dad decided he'd re-adjust the valves for me while i wasn't home.... he was told with the setup i have that you just bottom out the nuts... which is false... he tightened my rockers all the way down, and never told me, i was trying to find out why my engine wouldn't fire up for 2 weeks, cranking on it day after day.... now i find out what happened and i adjusted the valves properly, but its still not firing up, and the way its cranking, the engine seems too tight... any suggestions as to what could be wrong?

Most likely, the valves hit pistons. At the very least, you need to pull the heads and see what's up.

If they are non- adjustable do as Denny recommends and then check the timing.

sadly mine are the 5/16 studs with positive stop rocker nuts on them, i loosened them all the way and cranked the engine and it acted very tight, but i figure that would be the valves all being closed, so compression would be at its max.... then i retightened them by the book, and it still seems to crank weak like the engine is tight...

Originally posted by thesals
sadly mine are the 5/16 studs with positive stop rocker nuts on them, i loosened them all the way and cranked the engine and it acted very tight, but i figure that would be the valves all being closed, so compression would be at its max.... then i retightened them by the book, and it still seems to crank weak like the engine is tight...

have you checked the compression? checking the compression would really help with finding the problem. if the valves has hit anything then it should show up.


ps if you dont have any comp. back off of the valve adj. and try it again, to be sure its not the lifters.

I may be way off here - because I paint more than I build engines- but is there a chance of "wash-down" causing the rings to stick- that would cause a tight effect as well as a major drop in compression. A squirt of oil into the cyl.'s would cause enough compression to fire it.
Just grasping at straws here, I hate to see someone have to pull down a fresh motor.

Originally posted by hambiskit
I may be way off here - because I paint more than I build engines- but is there a chance of "wash-down" causing the rings to stick- that would cause a tight effect as well as a major drop in compression. A squirt of oil into the cyl.'s would cause enough compression to fire it.
Just grasping at straws here, I hate to see someone have to pull down a fresh motor.

best i can tell the comp.has not been checked. sure would have saved a lot of time.

yeah i'll check the compression tonite... and i dont think the rings will cause it... the motor isn't super fresh, its got about 4500 miles on it

ok so i checked the compression, came out to factory specs.... and found the result of my problem.... my battery is no good... the battery was tested last week and they told me it was perfect.... but its dropping down to 6 volts when i crank it... which means either the battery is a POS or the starter is pulling too many amps... but the starter is brand new, the battery is a few years old... so i'm ruling it the battery, once its replaced i'll know for sure

Originally posted by thesals
ok so i checked the compression, came out to factory specs.... and found the result of my problem.... my battery is no good... the battery was tested last week and they told me it was perfect.... but its dropping down to 6 volts when i crank it... which means either the battery is a POS or the starter is pulling too many amps... but the starter is brand new, the battery is a few years old... so i'm ruling it the battery, once its replaced i'll know for sure

bet you wish you had checked the comp. 2 weeks ago. if you even think the valve has hit a piston check the comp. first. always

yeah took me a while to find my compression tester, i actually looked for it last week and had no luck... and according to my cousin, a professional mechanic and a hot rodder... since my pistons are fly cut, my cam couldn't put enuff lift no matter what to make the valves hit the pistons... thank god i dont have a zero clearance engine

Originally posted by thesals
yeah took me a while to find my compression tester, i actually looked for it last week and had no luck... and according to my cousin, a professional mechanic and a hot rodder... since my pistons are fly cut, my cam couldn't put enuff lift no matter what to make the valves hit the pistons... thank god i dont have a zero clearance engine

he may be right but it dont take but a min. to be sure. the comp. check can give you a lot of info. about a lot of things you cant see.

Another thing to look for is making sure your pushrods are of the correct length. Using pushrods out of a '74-'77 302 will hang your valves open when used in '68-'73 or '78-up 302 because these pushrods are longer to make up for the additional deck height the '74-'77 blocks had.
Some cam manufacturers use a larger base circle (typically designed for the adjustable valvetrain) and some designed to be used with the tork-down rocker nuts. If you try to install a cam that requires adjustibility, chances are that the base circle is larger in dia. than stock and could hang valves open when tork-down as spec. requires. Are you using aftermarket lockable or locking nuts on the 5/16" studs? Because if you have the 5/16" studs, you're suppose to tork them down......

As far as the bolt-down rockers, they didn't appear in the 302 heads until '77. From '74-'77 they used the tork-down style 5/16" rocker arm nuts. And from '70-'74 it was hit and miss, some had 3/8 adjustable studs and some had the tork-down 5/16" studs

i've got 5/16 studs with the stock nuts, i've properly set them now... my problem was a crapped out battery

yeah it is great news... i ran into a secondary problem tho... my idiot friend, who i've mentioned before on this forum, put my freakin flex plate on backwards.... it got bent to hell and ate my starter with it... luckily i have a few spares and the starter is life time warranty... but its a 150% chance that hes not touching my car ever again