camshaft won't last wtf !!!!!

[royo]

Ok so your saying that they checked the retainer to valve guide clearance

[DubDubU]

Here is some more reading on oil. http://www.lnengineering.com/oil.html

[kamkam1]

Well after the machinist has checked everything from top to bottom on the heads and after careful inspection of the lifter bore, I swapped sides of the engine with the heads and got a used cam and lifter set with 5000 miles on it from a good friend, installed the cam and lifters ( matched to the lobes that they came from) with LUCAS cam lube and Valeline 20w-50w oil. When the engine fired up it started poping through the exhaust again so I shut it down waited a few minutes and fired it up again and the popping was not as bad but still there. Shut it down again, then fired it up after about 10 mins. and the popping was gone and the engine is running great. So I have not found out a damn thing, but my engine is running good with no issues. The used cam is a Lunati voodoo series and I got it CHEAP. Anyways I'm going to the track to see how it runs and will check back later. Thanks for everyones help and opinions as they are greatly appreciated, Later Kirk...

[d10s69c10]

good luck.

[kamkam1]

The old '68 was running good last week, but I started it this morning and what do you know, it started popping thru the exhaust and then started backfiring thru the carb. I don't know what else to do other than swapping heads. The heads that are on the truck have bronze valve guide sleeves. They are not the all bronze guides. Could these be giving me this problem. Later Kirk

[manimal]

do your valves look scorched on the stems? if so they could be starting to seize on the stem/guide liner. Good Luck
-Lance

[kdrodworks316]

The problem is the valve spring, I had the same problem. I had one spring that was alot stiffer than the others, I wiped 13 cams out and CRANE bought all 13 till the problem was solved with a new set of CRANE springs they bought. Mine would only last about 250 miles each before it was flat. on the #6 exhaust valve. I would have the machine shop, or you if you have a spring rate gauge tool, and check all they springs. I belive they should all be really close to the same, I dont recall the specs on mine. That truck has long since been sold, but still a daily driver on the same engine. Good luck and I hope this helps.

[kamkam1]

Well Summit warantied the cam and lifters and sent me a new cam kit. The valve stems and guides looked ok when at the machine shop. Its goning to be a while before I can get back to the ol' 68 do to lots of overtime on night shift, so I'll update in a couple of months. Later Kirk

[1bad chevy]

after reading all the post my 2 cent's would be the spring's are bad.iwould try a new set i've seen this problem a few time's with what they call z28 spring's buy the complete set of (cam, lifter's, spring's) and see what that doe's

[Rodms]

I ate two cams and two sets of lifters in the past 1 1/2 months and it was popping like you said yours is and found out the lifter pockets are not working correctly and ate up 4 and 5 cylinders both times

[djracer]

What's a lifter pocket

[d10s69c10]

^

[85sqbdy]

I had a similar problem years ago with the valve guides being to tight on one cylinder. It ended up with both valves seized in the open position, wiping out the cam, both lifters, both push rods, the piston, con rod, crank, pretty much went from the burn out box to the tree and locked up. Anyway, the machine shop bought everything but the block. Dart makes a killer block. Make sure you research your local machine shop before you give them all those expensive parts.

[Rodms]

Originally Posted by djracer

What's a lifter pocket

Block problems,where do they go?My borrowed block did not work right,I'm giving it back ,mines in the machine shop, don't like 60 over but go or blow,

[olblue81]

Had the same problem with my 355. When I installed the freeze plug in the back of the block (the one by the last cam journal) I drove it in too far preventing the cam from going far enough back in the block.
I killed 2 cams before getting frustrated enough to get a second opinion. Pulled the motor, took it to the shop I bought my parts from and they diagnosed it.

[chas350]

Any updates?
kamkam I would carfully examine the rocker arm slot, make sure it has enough travel without binding. Rocker stud bent? Check the rocker ball under the nut, how is the mating surface? Maybe the lifter bore needs honing?

[MylilBowTie]

What about break-in rocker arms?

[watahyahknow]

just keep the parts together the ball part to the dish part of the rocker , should be ok oh keep the pushrod and everything below it to the same rocker as whell , its a little extra work keeping it at the spot you take the part out of but its a little extra insurance at no extra costs

[Lx3]

Check out Brad Penn 1 racing oil. Good Luck

[BarryB]

Did you ever get this problem fixed? What type of valves are you using? If your using stainless steel valves with out bronze valve guides. It is possible the two metals are fighting each other and binding up as it gets hot. Stainless doesn't like regular valve guides.

[kamkam1]

Well it’s been 11 years, but I finally figured it out. I put 1.6 rockers on exhaust valves, which caused coil bind. #7 and #4 exhaust valves have shims under springs and that compounds the problems. Cam lift was to close to spring lift max, so the 1.6 rocker caused the coil bind. Thank you everyone..

[PGSigns]

This is what I use on a non roller engine. Get it from my race engine builder. He uses it to break in all the flat tappet race engines. Works great and you really need to follow the instructions.
Jimmy
https://performancebyie.com/blogs/ie...eak-in-oil-faq

[scottofksu]

Originally Posted by kamkam1

Well it’s been 11 years, but I finally figured it out. I put 1.6 rockers on exhaust valves, which caused coil bind. #7 and #4 exhaust valves have shims under springs and that compounds the problems. Cam lift was to close to spring lift max, so the 1.6 rocker caused the coil bind. Thank you everyone..

Good on you for circling back to provide “the rest of the story”!
I guess the take away is calculate total lift (I.e., cam lift + rocker lift), and see if you are close to the max lift for your springs. Finding you are close, (<.05?) measure everything precisely.

How’d you figure it out?

[scottofksu]

Originally Posted by kamkam1

Well it’s been 11 years, but I finally figured it out. I put 1.6 rockers on exhaust valves, which caused coil bind. #7 and #4 exhaust valves have shims under springs and that compounds the problems. Cam lift was to close to spring lift max, so the 1.6 rocker caused the coil bind. Thank you everyone..

Good on you for circling back to provide “the rest of the story”!
I guess the take away is calculate total lift (I.e., cam lift + rocker lift), and see if you are close to the max lift for your springs. Finding you are close, (<.05?) measure everything precisely.

How’d you figure it out?

[kamkam1]

Scottofksu, I was talking to one of my friends at work and he was telling me how much he liked big block chevys. We were just talking and I was telling him how good my small block ran and I mentioned the 2 cams wiping out the same lobes. We were discussing how it was built and when I mentioned the 1.6 rockers on the exhaust valves, it hit me, I never done the math to see if my springs would allow enough lift...