new member, from Pa. 1958 348cid

I have to look for them, but yes I do have them some where. I did check the valve travel when I had the motor apart and when I put the screw in studs as well to make sure that wasn't an issue. there was plenty of clearance in the valve travel for the lift of the lobes. I put shop air in the cylinders to see if they were leaking and all was good. I don't think that's the issue. the cam I put in was maybe a step or two up from stock, I just wanted a little more low end torque for pulling a trailer and for the tri power I have for it. I currently have the 4 barrel and intake on to get it running ok before I put the trips on. the cam shaft clearance (walking) has me concerned right now. when it runs, it sounds great, smooth, responsive and starts before i even get my hand off the switch. I am also getting a little more smoke coming out the exhaust than I'd like but that could be from being new? I have o-ring valve seals on now, don't know if umbrella seals would be better?
 
thk u, 63 .... ordered new rocker arms from summit 2-day, pulled the trans and found the machine shop did NOT put the rear plug behind the cam shaft in properly! Go figure! will be back with results. Original 348's had there problems but I will not let it get me down, and I want it right!
 

Jeffrey Osstyn

Well Known Member
Supporting Member 3
thk u, 63 .... ordered new rocker arms from summit 2-day, pulled the trans and found the machine shop did NOT put the rear plug behind the cam shaft in properly! Go figure! will be back with results. Original 348's had there problems but I will not let it get me down, and I want it right!
So what was the fix for the valve train issues? I also have a '58 348 which was suppose to have only 1000 miles on it. Pulled valve covers found 1 bent pushrod, several rockers arms badly worn on the valve stem side. One was so bad it had contacted the metal oil shedder on the valve spring and cut it in half! Another one was so far off to the side of the valve stem it had almost cut the rocker arm stud in half. Not liken what is going on, other than buying roller rockers and checking pushrod lenghts, how can I get by with the stock rockers for now?
 

62impala409

 
Supporting Member 1
My suggestion is to find a used set of rocker arms and push rods and replace all of them. Anything off a 348/409 truck motor would be fine. Aftermarket rocker arms are a crap shoot as far as quality is concerned. Too much junk has been produced over the years and it is hard to see the difference visually between good and bad parts until the junks breaks.
 

Phil Reed

Well Seasoned Member
Supporting Member 10
So what was the fix for the valve train issues? I also have a '58 348 which was suppose to have only 1000 miles on it. Pulled valve covers found 1 bent pushrod, several rockers arms badly worn on the valve stem side. One was so bad it had contacted the metal oil shedder on the valve spring and cut it in half! Another one was so far off to the side of the valve stem it had almost cut the rocker arm stud in half. Not liken what is going on, other than buying roller rockers and checking pushrod lenghts, how can I get by with the stock rockers for now?

You have more problems than rocker arms or pushrods. When the rocker arm cuts into the stud...the pushrod guide hole in the cylinder head has worn and become elongated. That's what holds the pushrod true in relationship to the rocker arm. Check your heads...those guide holes should be straight...if not you will need cylinder head repair, guide plates or new heads. Post some pictures if you can.
 

Jeffrey Osstyn

Well Known Member
Supporting Member 3
You have more problems than rocker arms or pushrods. When the rocker arm cuts into the stud...the pushrod guide hole in the cylinder head has worn and become elongated. That's what holds the pushrod true in relationship to the rocker arm. Check your heads...those guide holes should be straight...if not you will need cylinder head repair, guide plates or new heads. Post some pictures if you can.
Pushrod holes in head are fine. No apparent wear.
 

Phil Reed

Well Seasoned Member
Supporting Member 10
Pushrod holes in head are fine. No apparent wear.

The pushrod guide hole is elongated...taller than it is wide. The "sides" have to be exactly straight and perpendicular. If not...the pushrod will wander, cause more wear and then start cutting into the rocker arm stud. Just look over the rocker arm and pushrod guide holes carefully that show damage.
 

Jeffrey Osstyn

Well Known Member
Supporting Member 3
The pushrod guide hole is elongated...taller than it is wide. The "sides" have to be exactly straight and perpendicular. If not...the pushrod will wander, cause more wear and then start cutting into the rocker arm stud. Just look over the rocker arm and pushrod guide holes carefully that show damage.
I have experience with SBC engines, nothing on the 'W'. Same principle is used on both for pushrod guide holes in head. Past experience has been if the pushrod is touching the head it will show wear marks, mine are not. The pushrods installed were a mixed batch, some had the pressed in ball ends, some didn't. I installed a new set all with the pressed in ends. Guide holes in head all look O.K.
Lets focus on the rocker arms. What would cause the tips that contact the valve stem to wear excessively? High spring pressures? Poor quality? I tried to do a pushrod length check with a solid lifter and marking the valve tip but it appears the rocker is contacting almost the entire valve stem tip, very wide pattern. I am used to doing this with a roller tip rocker. I also noticed one head has the springs shimmed and the other does not. So assembly quality is probably suspect. These are also early 1958 heads yet the rocker arm studs are pinned, is that something that was done on 409 heads only? Also found wrong length spark plugs installed, had later long 409 plugs. I am worried about the assembly quality again!
I guess the test will be fire it up and see what happens, will not happen soon, dealing with the crankcase vent issues on this type motor. The road draft tube was removed and hole plugged, and nothing else was done for ventilation. I need to install a air/oil separator of some kind in the manifold so I can installed a pcv valve.
Really didn't want to pull the heads off, compression check showed all cylinders to be 135-140, old book I have said 150 is normal, so valves seem to be sealing O.K. That pressure of 150 seems a little low to me but apparently that's normal for low H.P. motor (250).
 
Hey everyone, took me a little to get back here but I seemed to have corrected all the issues I had! keeping my fingers crossed! Motor sounds good, quit and smooth now. I guess after all these years a lot of the parts were like me, getting tiered. This is what I found and did, maybe it will help someone else out. First off the "rockers hopping off", I found it was a couple problems giving the same result. I noticed the rocker studs were pulling up out of the head on the right bank, the left side was fine, I replaced them with screw in 3/8"x7/16" studs. To deal with the cam "walking" I pulled the trans and noticed that when I had it at the machine shop to have the block cleaned, checked for cracks ect. When he put the cam bearings in and installed the rear cam welsh plug he had it flush to the block, I replaced it with a new one and set it deeper into the block, no more cam "walking". The bent push rod issue I had stemmed from the studs pulling up and the adjusting locking nuts were backing off on me. NEW LOCKING NUTS A MUST! Pulled the intake off, took out all the spark plugs and valve covers, spun the motor over and watched the valve train, cam walk was good, rockers were all but one nice and even. The one that was not kept walking off to the side of the valve stem and on to the retainer. I'm not sure if it was a factory error or mine when the stud hole was drilled, I'm thinking mine, but it was just enough to off set it and made it walk to the side. Rather than changing the head I decided to heat that stud (after it was installed) and align it correctly so that it was straight and even, it did not take much at all. Now all the push rods and rockers move evenly as they should, no more cam walking and all is smooth and no visual issues. Assembled everything, it started right up, ran smooth and even, sounded good. I ran it for about a 30/45 minutes to see if it was going to show any more issues, took it for a test drive down the street and back, all seems to be good so far. Thanks folks.
 
@ Jeffrey, I have a brand new set of rockers, ball seats and nuts for 348cid that I got from Summit racing, 1.75:1 ratio, they are stamped, stock type hydraulic rockers. If your rockers are walking off to the side and bending the push rods, my earlier post tells you what I did to diagnose the issues I had. From what I understand, the studs were pinned because of the rocker studs pulling up out of the head, which changes the valve adjustment and alignment and could very easily bend push rods. If the tops of the valve stems are worn to one side, I would suggest replacing the valves, once they are worn like that they will keep on doing the same thing no matter what else you do. The stem and the rocker mating surface need to be square and centered to each other. If they are not the rocker will keep walking to one side and forcing the push rod to the opposite side and damage will done to the valve train.
 
Jeffrey, I forgot to mention, when you replace the push rods, replace them with a complete matched set and the exhaust are longer than the intakes, so make sure you have them in the correct placement.
 

lone 09er

Well Known Member
These guys will tell you what you need to hear, it may not always be what you wanna hear, that's why I love it:)
 

Jeffrey Osstyn

Well Known Member
Supporting Member 3
Jeffrey, I forgot to mention, when you replace the push rods, replace them with a complete matched set and the exhaust are longer than the intakes, so make sure you have them in the correct placement.
Thanks for the update Harvey! That's want I needed, someone to advise me what the fix was (hopefully) on their engine that had the same exact problem. I did indeed change all the push rods, and replaced the rockers that showed signs of wear. I did not change the nuts on the studs, At least not on the rockers I didn't replace, that will be next if my problems are not solved. My studs were drilled and pinned, I guess just like the later 409 heads are. One of my valve stems did show some wear, so I maybe going back in for that. Changed all my parts and spun it over several times doing the lifter adjust, all looked O.K. But the start up will be the test.
Thanks again for the update.
 
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