symptoms of flattened cam?
 

what are the symptoms of a flattened cam lobe?

heres the backstory, ive got a freshly rebuilt 350 in my 70 c20. i had a local machine shop do the long block and i assembled the rest. the cam is a crane hydraulic flat tappet with matching lifters. i had the engine broken in at the machine shop in the chassis. it was ran between 2000-2200 for the 20 minutes. since the rebuild ive ran nothing but valvoline vr1 with a bottle of zinc additive. changed the oil after break in and repeated. the engine now has about 250 road miles on it and ran great until tonight. i was over visiting family and when i went to leave i got the old "do a burnout!!" so i whipped it around in the culdesac and went on my merry way. on the way home i noticed the engine was running rough and had an obvious misfire. after checking all the plug wires and all the obvious when i got home i also noticed a ticking/clicking noise coming from the valve train. so i pulled the cover and discovered the rocker on the intake valve for #5 cylinder had come loose and was no longer on the valve where it was supposed to be. the nut on the rocker arm didnt seem to back off because it had about the same threads showing from the stud as the rest of the rockers did. so i went through the procedure to reinstall and adjust the rocker. now to get the right adjustment on the valve the nut is almost bottomed out on the stud and has about twice the threads showing as the rest do. so i put it all back together and fired it up and still had the same ticking/clicking noise coming from the valve train. so in disappointment and disgust i slammed the hood and pulled it back into the garage. i should add that on the way home i noticed a plume of smoke coming from the left tailpipe, like a bluish white (maybe burning oil?) after taking off from an idle. any advice on what to look for or check next would be great!

Re: symptoms of flattened cam?
 

Either you flattened lobe or pulled a rocker stud. The runability could also be a number of things ranging from a burnt valve to a blown head gasket. I would double check your rocker stud lengths and do a compression test.

Re: symptoms of flattened cam?
 

the heads are from 1978 and were also completely rebuilt. i believe 1978 would be screw in instead of press fit, correct? i didn't think the threaded in studs had an issue with pulling out.i did pull the rocker off and look at the stud, it wasn't loose but i didn't measure it either. i will double check tomorrow, thanks for the suggestion.

Re: symptoms of flattened cam?
 

Collapsed lifter?

Re: symptoms of flattened cam?
 

I would be betting ( unfortunately ) on a pulled stud.

Ask me how I know this? re-adjustment and fresh oil change fixed my issue. P.S. too much zinc is a bad thing...done way too much research and affirming the levels in regular ZR1 is enough for 70 k on a Comp Cam and Lifter set up.

Hope it goes well, with no major damages. Please let us know, plenty of folks here to help.

Also betting on those heads have press in rocker studs. Get the casting numbers to verify.

Re: symptoms of flattened cam?
 

Not that I know of. I'd check them.

Re: symptoms of flattened cam?
 

Screw in studs are obvious as they have a nut built into the stud st the base. They were only standard in hi po engines. Put a straight edge across the studs to see if one pulled out.
Hammering it back in won't solve the problem so it will need to be pinned or tapped for screw in stud.

Re: symptoms of flattened cam?
 

Exactly as randy500 said above ^^
And if the heads have been degreased in an oven at too high a temperature it can relieve the press fit on the studs making them pull out easier.

Also ... if using Valvoline vr1 why add a bottle of zinc additive? More is not better. In fact, too much ZDDP can create a corrosive condition and is source of many cam/lifter failures.

Re: symptoms of flattened cam?
 

I'd get that truck back to the shop that did the work.

Re: symptoms of flattened cam?
 

x2!

Re: symptoms of flattened cam?
 

x3

Re: symptoms of flattened cam?
 

Usually a lot of glitter in the oil. Pull valve covers, check the corners of heads. Dip your finger in oil, rub around. Look at finger, if you see the glitter and the bigger the particles, quicker its denigrating.
If not, as stated above.

Re: symptoms of flattened cam?
 

upon further inspection tonight i pulled a rocker stud out of the head. didnt even think to check that last night because i always assumed i had screw in studs. now the trick is to get the stud out.. some of the threads appear to be galled up and stripped. this is gunna be fun. could be worse... i guess. i appreciate everyones help

Re: symptoms of flattened cam?
 

I have been following along...and have some suggestions....

1/ Back to the shop that did the work, especially the head work....the remaining pressed in studs will most likely work their way out...symptomatic of too hot a cook when the heads were tanked...the press in studs need to be all removed and the stands machined for screw in studs...pinning them and or set screwing them will just weaken the stand...

2/ Make sure the push rods are not bent...

3/ Make sure the valve springs have not collapsed ...

4/ Make sure the valve stem seals have not collapsed...some shops just use umbrella style seals, rather than fixed style. This could be the smoke when taking off after idle...

5/ The cam lobe and that lifter could also be damaged from the lack of lifter contact pressure...the lifter is kept in contact with the cam by light pressure from the valve spring and the internal valving inside the lifter...

6/ Also the oil pump needs to be checked for metal contamination...

Personally, I would be pulling the engine and replacing the heads with an aftermarket set of alloys...use studs instead of head bolts and replace the cam and lifter set ....



:chevy::chevy::chevy::gmc2::gmc2::gmc2:

Re: symptoms of flattened cam?
 

Right. Why put any money into smog heads anyway.
Make the shop fix it, that's obviously your first move.
Or buy good heads and make the shop install them.

Re: symptoms of flattened cam?
 

Lots of good advice! My take- I've threaded a head for an individual threaded stud in the past, but that was mostly on old iron, not necessarily something that had been to the machine shop. I'll be honest and admit that I've never heard of a hot tank being too hot, but even with some raised boiling point from the lye, the tank can't be hotter than 260º, which temperature I've seen even big blocks survive, if the coolant was kept liquid. I've had mine to 230º while towing my trailer up a long hill, with no ill effects. Both metals have essentially the same thermal expansion coefficient, though, so I have reservations about that one being a stud pulling reason.

Re: symptoms of flattened cam?
 

really appreciate the response. this has all ran through my head already. last night i was so ticked off i was ready to pull my dad's 427 off the shelf and drop that in the truck. i wont be going back to the shop that did the machine work. it was the first time i had used them and did not have a good experience with them, AT ALL. long story short, when i had this engine rebuilt i was fairly uneducated on how to make an engine really make power... hence why i have rebuilt crappy smog heads on my fresh engine.. after the reconditioning of the heads was all said and done i could have had a nice set of aluminum heads for about 100-150$ more. why the machine shop did this to me still baffles me, but probably because they had a larger profit in the machine work and shop labor than they would have if they just sold me a new set of heads. im just going to take my lumps on this one i dont want to be had again. ive already thought that if this stud issue happens again (which im sure it will) i will be removing the engine and giving the top end some new heads. and like stated above i dont want to put any more money into a set of garbage heads than i have to. id like to stick with iron heads so if anyone has some suggestions on some good 64cc iron heads let me know! for right now though i think i will flush the oil and stick a bore scope down the pushrod hole and look for damage. i didnt see any metallic on the dipstick or my finger last night when i checked it while it was hot. there was no apparent damage to the pushrod, rocker, or valve stem.

Yep. Move on. So I'm in a similar situation
I have an original '70 350 runs great. Previous owner took the heads off and sold me the truck with '78 smog heads on it. He was upfront about it when I bought the truck and since become somewhat friends.
I don't want aluminum and going to buy these cast heads from summit racing. They are made by Dart and seem like a good value.
Mine truck or just a nice driver. Gets up and really goes already but I want to put better heads on it next winter.
Cool thing is summit racing in Ohio is 40 min from my house. Not sure if free shipping applies to heavy time such as this.
Here's the link

https://m.summitracing.com/parts/sum-152123/none/images
Posted via Mobile Device

Re: symptoms of flattened cam?
 

You'll need a different intake, but for the price you can't beat these http://www.jegs.com/i/JEGS-Performan...14005/10002/-1 Vortec heads are by far the best cast iron head for the money, they will support over 400hp right out of the box. Summit has their version made by dart for like 85 more than these. These are jegs house brand, but im betting they are re-boxed GMPP or Dart, I'm sure a quick inquiry to their tech line would let you know, I asked some questions on them a while back before I found a smoking deal on set of vortec heads and intake near me or else these would be on my engine. And yes free shipping applies to them.

Re: symptoms of flattened cam?
 

If your buying heads for a small block , vortecs are the way to go , dart iron eagles are nice also , check your combustion chamber volume , the heads you listed are 72 cc[low compression , most performance 350 heads are 64 cc

Re: symptoms of flattened cam?
 

Use a hammer, put the stud back in, drill a hole at an angle to the stud and put a roll pin in (commando style was just to break the drill bit off)...

Re: symptoms of flattened cam?
 

Only for the lonely Captain! Love it, fricken funny man!

Re: symptoms of flattened cam?
 

I did exactly this (even the commando style) back in '84 when I was dead flat broke, to the '71 350 in my K10 and I got an additional 80K trouble free miles before I spun a bearing.

Re: symptoms of flattened cam?
 

Bore scope will only give you a visual of the top of the lifter cup...I have seen these lifters mushroom out on the bottom from the pounding by the cam lobe...

I would be removing the manifold...and try to pull the lifter out of the bore...check the bottom really close...if its pitted or you cant pull the lifter out of the bore...dont waste your time...just pull the engine and put it on a stand...you could have a real mess internally...

Iron Vortec heads are great street heads...you will need a different manifold but they are plentiful in aftermarket...and different rocker covers..Vortec are center bolt...

But watch out for Vortec truck heads...the ones with the hardened exhaust seats...they dont flow well at all...

and you end up with screw in studs...

:chevy::chevy::chevy::gmc2::gmc2::gmc2:

Re: symptoms of flattened cam?
 

this has been a great thread! way more responses than i ever anticipated. i appreciate everyones help!!!