HamadUP

Its not my '71, but I'm talking about my '70 Z, it has a freshly built 355 with a Lonati 60102 mild flat camshaft, of course I did the 20 min. break-in procedure and used a API-SL mineral oil with a ZDDPlus additive and it was running fine for about 200 miles, but yesterday night while driving it, all of a sudden it lost power and a loud ticking noise came from the engine and when ever I hit the gas it backfires from the carb, I could barely reach home as it has almost no power at all, my no. 1 suspect was a wiped lobe, but would that have to be gradually rather than immediately? , is it because of the dye that I put in the oil to detect a leak few weeks ago? I still didn't passed the shock as its the first time I experience a wiped lobe!

'75

Sounds like you have an exhaust valve not opening. I've seen plenty of wiped cams back in the early 80's, but wasn't driving them, just fixing. Pull the valve covers and look for bent pushrods or a colapsed lifter causing the problem. Then look to see if all the rockers are moving the same amount. Hope it's something simple.

billla

Did you put cam lube directly on the lobes before installing it?

Did you replace the lifters at the same time as the cam?

Did you correctly adjust the valves cold before break-in?

It's not all that common; usually the cause is either lubrication or incorrect valve adjustment.

I wouldn't worry quite yet - plenty of things to check First is just the valve adjustment, as you may have had a rocker nut back off.

BLOCKMAN

Most companies out there don't use a P-55 cam core which is considered a performance cam core, So far thats all we use when ordering a HYD or solid flat tappet cam shaft.

Also make sure you know who's lifters they are selling as most compaines just rebox.

Hopefully your oil filter bypass was plugged if you lost a lobe, We just seen an engine at another that lost some lobes and it took out the rods and mains from non filtered oil.

bobs77vet

why dont you think its timing chain related?

learje

yep dont panic yet...this just happened to me, had my car a couple months, got a tap and loss of power. worried about the cam lifters and all kinds of horrible possibilites

pulled the valve covers and one of my rocker arm nuts had backed off. i could tighten it by hand. probably used too many times - no self locking capability left. i adjusted all the valves and installed posi loks. ez, cheap fix. found about half the rocker nuts could be turned by hand...

Ralphbf

Right additives and happened to fast.

Also sounds like too much power loss for a single lobe to me.

I have the same cam.
First I used a break-in oil additive from Comp Cams then after 500 miles
switched to Amsoil 10/30.
Can't remember which one right now but it was high in zink and phosperous.

Also I went with a high pressure oil pump.
I know for extra money you can get a hardened cam too.
I have 1200 miles on mine and she runs pretty sweet so far.

I put new push rods in when I added roller tipped rockers and bent one and
popped off the other one on #8.
It made it home pretty easily and she still idled on it's own.

Yours sounds like it is running a lot worse than mine did.

Ralph

bucky katt

do the heads have screw in studs or just press-fit? my 71z did the same exact thing and one of the pressed in rocker studs had pulled out. if that is the problem you can either drill and pin the rocker studs or just convert the heads to screw in rocker studs.

RobbSalzmann

Just a word of caution, if you switch to a high volume oil pump its usually a good idea to run an oversize sump oilpan. at higher rpms, that HVOP can suck a stock pan dry.

Kerrmudgeon

I had a small block backfire once, and it blew the rocker right off one pushrod, which it bent. Pull the covers and have a look. Might be simple to fix. I used an old pushrod I had from an old motor, and it's still running strong in my truck.

Ralphbf

I've seen that happen, that is a heart breaker.
I always use a stock volume pump and put in a high pressure spring.

No use cruising down the freeway with your valve covers full and your oil pan empty. High pressure is the way to go 90% of the time.

Thanks for the heads up.

Ralph

pauldana

good luck... been there, done that..... pray for a broken spring, stud or backed off rocker nut.

Check the oil!! got mettle? if so... bad.... if not..good:-)

mine took out the back two... and then the shavings took out a few other things, like the pistons, rigs, and every bering in the engine... 500 miles.... Went full roller after that... will never go flat tappet ever again.

first 300 miles on rotella and break in additive, changed out to mobile 1 10W30 (mistake, did not read billa's oil write) and that was about it... same description as you are giving...

good luck my friend...p

bucky katt

so Rotella isnt compatible with a gasoline fueled car/truck engine? it know that it is used by many vintage motorcycle owners that have an engine/trans that share an oil supply because it has a zinc content higher than even the better motorcycle oils and it's about 1/3 the price of any of the oils from the Japanese manufacturers. it makes for much smoother shifting and it doesnt have any friction modifiers that will destroy a clutch that sits in an oil filled clutch compartment. thats good to know that it isnt compatible with automotive engines. i love learning new stuff, the prospect of learning something i didnt know before is what gets me out of bed on really painful mornings. where is the oil thread mentioned? i'd love to go through it for myself.

Ralphbf

I know an auto mechanic that clams to have over 200,000 on his car and uses Rotella It has to be compatible.

Ralph

Ralphbf

"(did not read billa's oil write)"

So where is this write up?

Ralph

bucky katt

ok, i've gotten mixed opinions on this, but 200k miles running the Rotella tells me that this diesel oil would work. thanks much for clarifying that for me.

L88Plus

Old Wive's Tale, won't happen. Oil galleys, etc. will only hold so much oil. If a standard pump will keep 'em full, a high volume will pump no more. Any oil that can't be run through the system at operating pressure is returned to the inlet side of the pump. If your clearances are too loose, it might take a bit more oil, but that is hemorrhaged directly back into the pan from cam and crank bearings, NOT sent to the top end.

BLOCKMAN

x2!!!!!!!!!!!!!!

billla

Pairs with the myth that a HV pump will "move more oil through the engine"...which just ain't so. If the bearing clearances are wide enough that this is the case...then you'll have other problems in short order.

Flat-tappet oil sticky is here...but let's not turn this into an oil thread as the OP used a break-in additive so the point is moot in this case. Hoping to hear good things back from the diagnosis with an easily-fixable issue

http://forums.corvetteforum.com/c3-t...ppet-oils.html

Bugman Jeff

Could be as simple as the timing slipped? Or maybe one of the cap hold downs popped loose?