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Putting together my 74 302 I just got back from the machine shop. I made sure the cam was put in properly and lined up with crank gear correctly. I stuck the heads on, put in new Melling lifters. I am planning to reuse the rocker arms, pivots, nuts and pushrods. I rolled the engine up to tdc and dropped in two pushrods on #1 and their matching pivots and rocker arms. The pivots drop down below the threaded part of the rocker stud on each like the attached pic. The nut bottoms out on the rocker shaft but the rocker rms and pushrods are still fairly loose and lifter is not compressed at all. ..Cam is a Melling MTF-5. Any ideas welc
ome I wonder what I am missing. A buddy suggested adding washer above the pivots but not sure of that.
Did your machinist replace or recondition your old valves? First WAG is that maybe he installed valves with too-short stems. I think your rocker arms re the rail type, which have sidewalls that extend over each side of the valve stem to locate the rockers over the valves. These need longer stem valves to keep the rails away from the retainers. Push the end of the rocker against the tip of the valve and see if the rails have about 1/8" of gap to the retainer or lock, or if they are almost touching. If the latter, the rockers and valves are not matched, and the valves must be replaced with the correct version with longer tips.
Thanks it looks like 3/8 from the bottom of the rocker to the lock when I press the rocker against the valve stem pic attached.
I tried a washer on the stem between the nut and the pivot that was big enough to slide all the way down the valve retainer stud and now
can adjust the valve but this seems odd. Maybe all my old parts - arm, pivot ball and pushrod are all too worn and together are causing the problem?
It's been decades since I did this on my old 302, so I can't remember whether there was a washer between the nut and the pivot ball. Do you recall if there were washers when you took the engine apart for overhaul? Are you now able to crank the nut 3/4 turn past where you first close up the the clearance in the pushrod?
There were no washers there when I took it apart. None of the manuals I have here mention any washers. If I add the washer I can get the 3/4 turn but it seems odd that I should have to use it. I'm wondering about a slightly longer pushrod to raise the arm a bit. Thanks for the reply appreciate it.
Thanks..my ford buddy was by this morning and thinks I need new pushrods. .he is suggesting 1/4" over stock to get the rockers up to a decent height. he also mentioned base grind difference on cam but it is brand new Melling MTF-5 that I thought was close to OEM.
You don't have any layman's tips for checking valve train geometry do you..thanks again for the help
The simple technique is to paint the tip of the valve stem with a dry-erase marker, install pushrods and rockers to specified clearance, and turn the engine through 2 revolutions to activate both valves, and look at the pattern left in the tips. Ideally, you want the wear pattern in the middle of the tip, as narrow as possible. I think the pushrod length determines where the pattern ends up, while the rocker arm height determines how wide the pattern is. Or it could be the reverse, I forgot, but the two do affect each other. Since you have hydraulic lifters, they will compress when the cam lobe pushes them against the spring pressure with no oil, you might want to get low tension valve checking springs for this test.
The rocker arm studs on a 74 302 head should be positive stop, meaning there's a shoulder that the rocker arm rests against when tightened down. Maybe your machinist replaced them with standard studs that are adjustable
They are positive stop studs. I'm puzzled I rolled 1 up to TDC and threaded the nut down on #1 intake until it could not be threaded down any more. I torqued it to 20 ft/lb as described in my manual but I'm still getting some slop in my pushrods. I tried this with both my old and new lifters and same result. Pushrods are oem length. The machine shop wants me to bring it in tomorrow.
Valve rotators are little cups that go on the exhaust valve tip. They may have been eliminated if you changed your springs. I may be using the wrong terminology
They are positive stop studs. I'm puzzled I rolled 1 up to TDC and threaded the nut down on #1 intake until it could not be threaded down any more. I torqued it to 20 ft/lb as described in my manual but I'm still getting some slop in my pushrods. I tried this with both my old and new lifters and same result. Pushrods are oem length. The machine shop wants me to bring it in tomorrow.
They should be positive stop studs unless they were replaced. The slop comes from the lifters not being pressurized with oil. You should pressurize the oiling system with a drill and socket on the oil pump drive with the distributor removed before firing up the engine. Once that's done, the slack should be gone in the rockers.
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