SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

[kenimpzoom]

Just put a new cam in the Vette along with a rebuild. Everything was running great for 80 miles, then a loud tick and slight backfiring. The number 6 intake rocker was loose. I tightened it back up but it was evident the rocker nut was down much further than the other rockers.

I am certain it is either a collapsed lifter, or a wiped out lobe.

Anyway, I noticed while cranking the engine with the starter that the other valves were opening as normal, but when I stopped cranking, the lifters would bleed down and the valves would close somewhat. I assume this bleedown is normal?????

For sure the suspect lifter would not bleed down.

I am hopeing this leads to a collapsed lifter and not a wiped lobe. I am thinking some junk plugged up the lifter and now I gotta pull the intake and get the lifter out.

What do you guys think? Cheer me up so I can get the gumption to work on this freakin motor as I am a little but bummed out.

Ken

 

[WizeOne]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

I assume it is a flat tappet not a roller cam? No real way of knowing which issue is correct. Suffice it to say that with oils currently available, wiped out cam lobes are becoming epidemic. Did you use the high zinc content break-in stuff?

 

[kenimpzoom]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

Yep normal hydraulic cam. 1976 small block 350.

I used STP oil treatment. And coated the lobes with the molly grease that came with the cam. I looked for GM EOS but couldnt find it.

 

[Mkos1980]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

Hows your rocker stud? Is the rocker stud even with the rest of them or is it getting pulled out?

 

[a70eliminator]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

If you wiped a lobe it would have happened in the first 15mins of running not after 80mi. another thing if you wiped a lobe simply removing the lash wouldn't make it better, but if you have any doubt just indicate your lift and you'll know for sure.

 

[kenimpzoom]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

Forgot to mention, yep I checked the stud, it was not pulled out. Heading to the garage now, wifey just gave me 30 min to work on it. Yipee!

 

[WizeOne]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

...I looked for GM EOS but couldnt find it.

I hope that is not the crux of the issue. I read that the EOS or equiv is essential with current zinc free oils. Your description of time and mileage are classic for modern era, short term cam lobe wipeout. I don't agree that it would necessarily happen in the first few minutes, especially with the compounds you did use.

Another possibility is the cam itself. I heresay that there are a lot of cams offered (vendors unknown) that have improper hardening on the lobes. Did you say where you got the cam??

 

[kenimpzoom]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

Wife gave me 30 min, but I took 60 min!

Lifter definately collapsed, lobe looks ok using a dial caliper. All the lifter plungers were at the top of the lifter (when valve closed) except this one.

Now I gotta investigate why lifter collapsed... to be continued.

One note, dont know if this is coincedence or not, but oil pressure rose by about 8-10 lbs at the same time I noticed the engine wasnt running quite right. Is it possible the entire lifter galley was plugged and only one lifter collapsed?

Ken

 

[WizeOne]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

Lifter definately collapsed, lobe looks ok

Whew!

 

[kenimpzoom]

Re: SB Chevy New Cam - Collapsed Lifter or Wiped Lobe?

I pulled the old lifter apart and couldnt find anything wrong. It was stuck all the way down. I put it all back together and filled it with oil and it seemed to hold on the bench. But I replaced it anyway (3 bucks for a new one). Broke in the new lifter with molly lube and all is well.

Car is running great. Wifey is happy again.

Thanks for the support guys.

Ken