I got a call to come over to my friend's house tonight because he couldn't get his new motor to run right. The motor in question is a 1972 351W that was rebuilt by an "engine builder". After doing the basic messing around with carb and timing, I knew something was up. It was back firing through the pipes with any initial timing under 20 degrees, and when it idled for prolong periods the headers started glowing. I had him pull the covers and found this; Every single rocker was cranked down all the way, and smashing into the valves. He had regular 3/8'' washes stacked on top of the pivot nuts because he ran out of threads and the rockers were STILL loose. It scuffed up the top of the retainers a bit. What is wrong here? I know a part is miss-matched, but I'm not a ford expert. The pushrods measure out at about 8 3/16, which appears to be the stock size for that year motor. I'm assuming the valve springs have a higher installed height than stock, and will require longer pushrods. Just checking before we got that route. Here are the rocker arms that were on the car.
OK, Those are rail type rocker arms which are correct for that vintage 351W. It also appears to have the correct corresponding long stem valves for said rocker arms. One thing that is out of place are the aluminum retainers which I believe are the culprits. For one thing the diameter is too big for those stock rockers. I am pretty certain that the rocker arms are hitting the retainer and are interfering with the valve action.
Yeah, but I can't see them being cranked down all the way to the point of the rockers bottoming out on the studs, no?
A real engine builder wouldn't let that out of the shop with aluminum retainers! And he would have checked the valve train geometry and installed the correct length push rods. Find a better engine builder.
Oh, and he didn't have a guy build this motor, he bought this motor already done from this guy who apparently is a professional engine builder. Like I said the guy actually came over to the garage and said he couldn't figure out why it wouldn't run right, he said my friend must have bought the wrong balancer and the timing was off. So can I solve this buy getting a pushrod length checker and buying longer pushrods that allow the rocker to sit off the retainer and get proper adjustment?
I would try to match up what you have with real 351W parts, a friendly parts counter guy should be able to help out. Match up the rockers, and the pivot ball & pushrods for a start. The retainers are getting marked up due to the rockers being at that bizarre angle. Bob
For starters push rods to short from looking at pictures.The tupe of retainer should have no bearing on the problem.
I'm not a fan of aluminum retainers myself, but they've come a long way in recent years. They should work fine and are not part of the basic problem here. Bob
Like I said the pushrods are the stock length for this motor, I think the valve installed height is higher than stock.
The valve spring height looks about right, something you can check with a scale once you know the number. I'd be more suspect about the rocker studs, where did they come from, are they possibly for roller rockers? It definitely looks like a grand mis-match of parts. Bob
They do have their place. If you want to reduce valve-train weight and expect to change them periodically, they're fine. I wouldn't use them on the street though. Again, there's a weird mix of parts there. I would expect to see roller rockers to go with those retainers especially since the stus are so long. Bob
Ford 302 and 351 of that era need the nuts run down all the way. If the hydraulic lifter cant take up the adjustment, run good, and be quiet, different length pushrods were available from the dealer. I have used very thin flatwashers under the nuts for adjustment.
Come on you Gm & Fomoco mechanics. Those stud mounted rocker should never be tightened down till you run out of threads. Just a half turn once there is no push rod end play.
You're absolutely correct for adjustable rockers, expect to see a few threads above the nut, not much more. Bob
Those aren't positive stop rockers. They are definitely adjustable. The pushrods might be too short, but it seems to me that there is no fulcrum "ball" in those rockers. The OP mentioned there were regular flat washers under the nuts, which makes me believe the fulcrum has been left out! I'd go looking for those...
I thought rail rockers were discontinued before the 351 came out? arent they on early 260 and 289s before 66? Fed
Nah it had the balls, with washers on too. I'm going to get a pushrod length checker and set the valve train geometry like I would normally with some proper length pushrod length.
Nothin' beats a picture to get someone in the right direction. I have never ever seen odd washers added to rocker arms. I'd be interested in how those studs measure up against some stock 351 W studs. Bob
I had a 351W 1979 and had rockers like Post #23 there is no adjustment needed,just turn down to stop. The one on right
Yes, there are 2 types. The ball type should be adjustable, the rocker type gets torqued to a spec. With the ball type, I'd be highly inclined to set the valves the old fashioned way, once the component compatibility snafu is cleared up. Bob
That's the way to do it. What year are those heads? and are they 351W heads? The positive stop studs were used in 1968, and later windsor's, unless someone replaced the positive stop studs with the early adjustable studs.
The studs could be an inch or a foot long, and would not change anything. The rockers would still be in the same location to take up the slack. The motor probably had roller tip rockers on at one time and might have needed shorter pushrods. Rebuilt with stock rockers and short pushrods, and this is the result.
Is this what you believe to be the issue? If so, then longer pushrods are the fix... There is more to setting this geometry correctly. You will want the to rub centered on the valve tip throughout the lift of the cam. You can see how dramatically pushrod length alone will have on geometry..
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