287 Rocker arm questions
 

I have a 1955 GMC with the 287 based engine. About 5 years ago I had the engine rebuilt and have not really run it much since then. I would start it every few months while I was restoring the rest of the truck. I have now discovered that apparently only my push rods are oiling and I am getting no oil coming through the oil galley in the heads that leads to the rocker studs. The engine is still assembled in the truck and the last thing I want to do is disassemble everything to find the source of the problem.(cam journals) So I am trying to see if maybe I can replace my rocker arms with ones that have a hole in them so the oil coming up the pushrod tubes will run down and oil the rocker balls, and if I could find some that had roller tips for reduced friction that would be nice also. Thank you.

So here are my questions:
1. What is the ratio of the 1955 287cu. rocker arms? 1.52? 1.65? or what?
2. Does anyone sell a replacement roller tip rocker for this motor?
3. Can I keep my stock size rocker studs and change arms, or do I have to put larger ones in?

ratio is 1.5

go with a 1.65 rocker of any type

keep your rocker studes but watch your rpms

keep them below 5800 rpms

Rocker arms
 

I have a set of PRW 1.5 Sportsman rockers and the stud holes in the rocker balls are too big(7/16) and my stock studs are 3/8. Also when I set the rocker on the push rod the rocker tip is past center on the valve tip. I am trying to find out if there is something that will be a stock replacement, or little modification.

I wouldn't see a problem with drilling the factory rockers ?

Those early rockers are diff from later.First they use stud oiling,im sure they are pressedin studs.I have used the comp roller tip rockers after replacing the studs and went to pushrod oiling.You have to be very aware of the geometry so new push rods might be in order.Non roller tip late rockers wont work.Tom

55 pontiacs were a 1 year only adjustable rockers.
In 56 and later they were just torqued to 20 lbs.

If you search through this forum, there are some fellows running small block chevy rockers which are pushrod oiled on these old engines.
Hope this helps, Bud

replacement rockers
 

So if I am hearing correctly, if I change my studs to 7/16 I may be able to use these sportsman 1.5 roller rockers?

I apologize if my questions are to basic, but I have not found a person locally that is knowledgeable about this engine design and it is quite unique as you know. Plus I am not certain what the machine shop changed or did wrong when it was rebuilt. I am not going to just start taking things apart to figure it out unless I know what I am looking for or what to expect.

The shop is closed down now so I can't just ask them. They were primarily known for building high performance dirt track race engines. The problem seems to be I got what I paid for, but I did not know what is was getting!

What I know:

*I do know the valve springs were changed to beehive and the head MAY have been machined a little to allow them to sit down, but I do not know what the spring rate is or the height.
*When I turn the oil pump with a drill the rocker studs do NOT have oil coming out of them but the push rods do.
*I think the valves may have been ground but not replaced.
*It has the original rocker arms, pivot balls, and push rods.

Your heads probably should be removed to be machined for the 7/16 studs. I wouldn't attempt to remove the studs and hand tap while the heads are on the car unless you had some type of jig set up.

I'm trying to find a set of 59 389 heads for a guy for the reason of the studs are all at differant angles when it was converted to screw in rockers because someone tried doing it by hand.

The path for oil to get to the galleries that feed the bottom of the studs and eventually up to the rockers is blocked a large percentage of the time by the #2 and #4 camshaft journals. The cam has to be in just the right position (once per camshaft revolution, and then only for 5-10 degrees (my estimate) of camshaft revolution. And I'm pretty sure the hole in #2 and #4 do not align (to let oil pass) at the same time. Look here: http://chevy.oldcarmanualproject.com...5559mm435.html
for the explanation of how this works from the '57 GMC Maintenance Manual. (GMC used Pontiac V8s from 55-59.

So in order to have your oil pump primer pump oil to the rocker studs on the driver's side head you have to have the camshaft rotated to exactly the right position to align the #4 journal holes with the holes in the #4 cam bearing and to pump oil to the passenger's side you need to have the camshaft rotated to exactly the right position to align the #2 journal holes with the holes in the #2 cam bearing. Otherwise no oil to the studs.

The bad news is that I don't know where the alignment takes place (i.e. TDC, 37 degrees after TDC, etc) nor if there is actually a standard.

Good point Bill, very good point. I am baseing my lack of oiling speculation on a couple of things though:
1. you can remove the valve covers with the engine running and unless one of the rockers is loose and letting oil shoot past the pushrod there will be no mess created by oil. There is never much oil accumulated in the heads that runs back down.

2. It never looks like there is any oil accumulated in the rocker ball area.


Even if I were to replace my studs with 7/16 I think the distance from the pushrod to the stud to the valve tip is incorrect. Somewhere on this site i remember someone making a reference to this spacing also but, I don't recall where or a clear resolution.

I guess the only way to verify the stud oiling is to remove the coil wire and the sparkplugs and just turn it over with the starter, with the rockers removed, until I either see oil shoot out or I give up, huh.

They are too hard to drill. A solid carbide drill bit will just burn itself up- I tried this about fifty years ago. If you have access to an EDM (electrical discharge machining) mill, oil holes could be created in the pushrod sockets of the original rocker arms. BUT(!)- I'm not aware of this ever being done, so it would have to be considered an "experiment". One aspect I'd be leery of is the [hydraulic] lifters not having the appropriate oil restriction for through-the-pushrod oiling, and way too much oil being delivered to the rocker chambers (?). Also, the durability of the upper pushrod ends might be compromised by the oil hole edges (?).

It will never "shoot out" while cranking the engine. Read Bill Hanlon's post again, regarding the narrow "window" of oiling to the studs. A freshly assembled stud-oiling Pontiac will very slowly build a small puddle of oil in the ball-pivot portion of each rocker arm over the first few minutes of initial running.
What I've just said assumes your stud oiling system is a-okay. But I, too, would not be confident that the shop thoroughly accessed and cleaned the complete oil paths to the rockers. So changing to pushrod oiling might be the most expedient route [I need to search old notes to remember which rocker arms worked for me].

Jack: In your opinion as a machinist, what would EDM do to the "cyanide hardened" surface (1955 Pontiac Shop Manual, page 6-3, first full paragraph) of the rocker arm?

The same replacement lifters (SEALED POWER Part # HT951) are listed by the parts houses as compatible with 1956 316" through at least 1978 400" engines, so the oil flow up the pushrod shouldnt be a problem.

I have already ruled out drilling my rockers as an option for me, some of mine are unevenly worn(one is completely ruined) and I know drilling would be very difficult. So, if I can find a set that is the proper ratio and spacing from the pushrod-stud-valvespring I need to change them out. Of course I would prefer to not have to change the studs to the larger 7/16 and keep the original size, but if no one makes a set that will pushrod oil with the correct spacing that may be my next easiest option.

yea, its the 55 LIFTER that is the odd man out, not the push rod, rocker or stud,

and stud oiling was used up until 64.

I have several engines that have the stud oiling set up. they are covered in sludge the consistancy of cosmoline, I am certain they would wear considerably or even fail in short order if I waited for oil to show up on the rocker. The system works well but requires oil changes at reasonable intervals and while these engines dont, as a rule have PCV systems, the vent tube system works well if the filter is also servicedat reasonable intervals. failing this, the engine sludges up at an accelerated rate and will cause several valve train problems.

How do you mean, when I sat the 1.5 prw rockers I have on the studs, if the push rods are in their pocket the roller tip contacts on the outer edge of the valve stem. Is that because the pushrod holes need to be elongated or maybe the push rods need to be shorter to use them??

You will have to get differant lengh pushrods to make the
geometrie right. You want the roller tip to set on the center
of the valve stem, the correct pushrod will align the tip and
the stem.

GT.

which ever rocker you choose you will want to follow installation instructions, also whats not written in the instructions is check valve train geometry.

its no big deal as most rockers fall within specs. but if you go with the 1.65 rockers you will cant to make sure ther is no interfearance with any other part, the main concern seems to be the cylinder head wher the push rod go through. severla good points mentioned by others above,

my statement re the lifters is that for some odd reason, all speculation aside, the 55 lifters are unique. Lots of piffle banter and blather on what the difference is but no hard facts. cams seem to interchange, push rods ditto. but something about those lifters that allow vendor to ask, with a streight face, 350 bucks plus for them.

I'm betting that if someone did there home work, like those damn oil pumps, the price would adjust accordingly(downward).