84-Z28-Canada

hi guys, new to the game and finding out new things all the time. I did a 350 swap into my 84 z28 last year, and it never really ran right. One day this spring, I was driving home and the car just dies, side of the road style. After a minute or two, I get it started back up and hear a shearing sound coming from the motor. I brought over a few mechanic buddies, each of them had a listen, and each said connecting rod bearing. Fair enough. So, I've removed the motor and i'm disassembling it to take it to the machine shop for all new bearings and rings....when I cam across the lifters for exhaust valves 1, 2, 3 and 4. I have never seen lifters this bad, have you? The bottoms are down right dished inward, and chipped at the edges. and yet....5, 6, 7 and 8 are just fine, along with all the intake lifters....So, still in mind that i will be refreshing the bearings and piston rings...what in the hell happened to my lifters and why?

84-Z28-Canada

Thought i'd give a visual reference

Apeiron

I've seen them worse... to the point where it wears right though the face.

Lubrication failure or improper break-in. You need a complete rebuild now.

5spd-iroc

it can wipe the lobes and lifter if the cam never got a good broke in, not sure how many miles you have on the motor but only other thing i can think of is a loss of oil to the cam

5spd-iroc

ah beat me to it lol

TreeFiddy

Or an interference in the valvetrain, or not enough zddp in the oil. I've had one lifter go like that in each of my 2 last cams due to a slight unnoticed interference, took a gamble that the filter caught the fallout and havent had any problems now years later.

In your case, you have more lifters involved and the engine apart anyway, so make sure you clean the block oil passages completely.

84-Z28-Canada

thanks for the replies guys, I was thinking along the lines of improper lubrication. It's possible that the cam wasn't broken in properly as well, although I did put a generous helping of cam lube on it when putting it in. I also primed the oil pump with an old dizzy and a drill for a bit, trying to get some oil around the engine before putting it in and firing it up. Just means I have to do a better job of it this time. Apeiron, when you say complete rebuild, are you including the rotating assembly? As is all new parts? I already am scheduled to take the short block in next week. I want to get it hot tanked, and put back together with new main bearings, con rod bearings, and piston rings. I was hoping to reuse the crank, rods and pistons....but I suppose we'll see what he says. If it comes down to that...I'll save a bit and go with forged, I see a supercharger in my future...

TreeFiddy

Did you break in properly after the pre-lube - ie around 2000 rpm for about the first 20 mins, NO idling - then change oil afterwards? Did you use a zinc additive in the break-in oil?

LilSki

iTrader: (1)

When you break it in next time you are better off using a break-in oil. Comp Cams makes it and it is better to use than an additive as it can take time for the additive to mix with the oil. A break-in oil has all the zinc you need and it is already mixed.

Also make sure you use the cam grease and not the lube when installing. The lube will run right off the cam and lifters and by the time you get around the starting the engine there is very little left. Use the grease and it will stay on there until you fire it up.

skinny z

I went through the same thing with my old flat tappet cam except this one went tens of thousands of miles before it gave up. Lifters completely concaved, lobes wiped out.
The reason for the rebuild is because all of the material that's been removed from the lifters and cam has made it's way through the engine.
I had to have a re-bore (.020"), crank cut on rods and mains (.010"), new cam bearings and an oil pump.
I put it all down to a) oil formulation (as in no high pressure additives), b) service life and c) I made a step up in valve spring as well as moving up to a 1.6 ratio rocker. All of those contributed to the cam/lifter failure.
For what it's worth, a move to a roller cam will prove to be an economical one if it prevents another failure.

84-Z28-Canada

thank you very much for your input guys, that sounds like exactly what happened. Didn't use the right oil additives on break-in, didn't run at 2000rpm for 20 min etc. I guess you go through these things when just starting out. Ok, so the motor is going into the machine shop next week. This might sound dumb, but if the cylinders have to be bored 0.020, or 0.030 over...does that just mean bigger rings, or bigger pistons too? I'm ok with both, but I will reuse the pistons if possible. I guess I'll be hearing everything from the machine shop guys. Also, I've heard that both Edelbrock and Comp make roller cams for the older sbc's, is this correct? thanks for the input guys

skinny z

Any overbore will means new pistons.
It's entirely possible that you could get away with a honing (minimal material removed so as to allow for a fresh undamaged cylinder wall surface) which should allow reusing the same pistons although with new rings. The crank may only need a polish too rather than regrind. Either way, a new set of bearings will probably be needed.
As you said, you'll get feedback from your machinist.
Be sure to let the shop know what happened. I'll bet they've seen it all before because it's not that unusual. Be sure to inspect the oil pump internals even if the shop overlooks it. Mine was smoked.
There are several cam manufacturers that make retro-fit roller assemblies for the Gen 1 small block. I would think that one is pretty much as good as another provided you stick with quality brand names.