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Author Topic: 68 Z engine parts  (Read 1252 times)
68Zproject
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« on: March 13, 2014, 08:19:41 PM »

OK here's my situation:  I have a CE 302 that was rebuilt that came with my car when I purchased it.  I took it to a machine shop to disassemble and check to make sure it was good to go.  I got it back and ran it it for about 4 years.  The only thing I didn't do was check the balance.  Big problem.  Then about a year and a a half ago I pulled some rocker arm studs out when my throttle got stuck to the floor and I had to push the clutch in to get stopped.  So I decided to tear it down and get it balanced as it was winter and I wouldn't be driving anyway.  That was November 2012.  Long story short, I just got my parts back and had to use my spare crank as the one that was in it wasn't properly machined.  So now I need to get new bearings and rings.  So:

What kind and style, brand are you people using or could suggest?  I have gone on Summit but there seem to not be a lot of choices.  My original bearings were Federal Mogul which seem to have been replaced by Sealed Power.  I'm not going to race this thing, but I don't want it to fall apart either.  Middle of the road Sealed Power A series rod bearings?  Clevite?

The other question is rings.  I have the TRW 2210A's.  I was told that the rings that were on them are .062 top and bottom and .124 oil rings.  What style-brand do you suggest?  I was also told to use iron ductile rather than moly because of seating issues.

Input on this would be greatly appreciated as I want to drive my car again someday.
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68Z28
z28z11
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« Reply #1 on: March 13, 2014, 09:08:14 PM »

Clevite/Michigan 77 and ductile rings. Chrome moly rings are great for long life, but are twitchy to seat sometimes. People swear by them, but I've never had a problem with seating ductile rings in the initial startup. Proper honing techniques are all you need.

Cut your own ring gaps to factory specs - I wouldn't trust pre-gapped. Be sure and chamfer the ends slightly to keep from scratching the bores (I assume you are assembling the long block yourself), but don't go overboard.

Bummer about the studs pulling out. Did you pin 'em, use oversize (.002) studs, or drill/tap for threaded studs ? I'm not sure if GM still sells the oversize studs, but you could probably find them aftermarket. At least they'll be closest to originals in appearance if you haven't assembled the heads.

JMO -

Regards,
Steve
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1968 Z28 BRG/W
1969 Z28 X77 LeMans/W
1969 X66 L78 Cortez/BVT
1969 Z11 L48
68Zproject
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« Reply #2 on: March 13, 2014, 09:49:18 PM »

I tried to tap the holes myself with a guide specifically made for the threaded studs that look stock.  I couldn't keep it straight so I quit and had a machine shop do it and then noticed that a couple of bosses were cracked.  I couldn't prove that the machine shop did it as I didn't pay that much attention to them when I took them in.  Had to get the heads welded and everything is good on them now.  That's what made my mind up to do the tear down as by the time I got the heads fixed driving season was over.  

In regards to your suggestion of the Clevite 77's.  Are they that much better than the Sealed Power?  I appreciate your input.  It's just that that's what I had in it and came recommended from the shop that probably cracked my heads.  May say volumes about them.  Also, checking Summit they only ones that seem to be iron are Mahle.  Thoughts?
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68Z28
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« Reply #3 on: March 13, 2014, 09:58:13 PM »

Mahle is good stuff. See if they(Summit or Jegs) can sell you a re-ring kit. You will save $$ and it will have everything needed except main bearings or Cam bearings. Mahle has a clevite 77 bearing
cracked bosses could be from a Big cam? and rockers binding(hitting )stud which will crack them.
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1969 SS/RS 396 coupe Hugger Orange X22 712 bought in 79
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68Zproject
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« Reply #4 on: March 13, 2014, 10:14:12 PM »

What is in a re-ring kit?  All I need is the rings and bearings.  I already have a complete gasket set.
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68Z28
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« Reply #5 on: March 13, 2014, 10:23:15 PM »

It is everything you need plus gaskets. Usually sold in kit form some savings overall on parts. You just order by bore and journal size. Since you have gaskets, I guess you can nix that.But, you may want to compare prices and it still may be cheaper. plus most places stock these over individual parts. It has been a long time since I built anything so things may be different. Last re-ring kit I bought was $50 if that is any indication.
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Putting you First...Keeps me First. Talent on loan from God. Helping the hobbyist and exposing the fraud
1969 SS/RS 396 coupe Hugger Orange X22 712 bought in 79
1969 SS 350 coupe LeMans Blue 713 bought in 79
1969 307 4spd. coupe Daytona Yellow 711 bought in 85
68Zproject
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« Reply #6 on: March 13, 2014, 10:35:02 PM »

Well, Summit has their kit for $88.  Not sure if that's good or not.  Rings, gaskets and bearings.
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68Z28
z28z11
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« Reply #7 on: March 13, 2014, 11:37:19 PM »

In regards to your suggestion of the Clevite 77's.  Are they that much better than the Sealed Power? 

I've used Clevite since my first build (Power Pack 283, '57 Bel Air) at age 16. I used them in my 302 during a rebuild in '75 - used 12.5:1 Manley pistons; at 30K miles the bearings still look pretty darn good. Machine shop warned the high compression ratio would pound the bearings out on the street, but they were incorrect. Can't argue too much with that kind of success.

Cracked stud bosses remind me of poor removal techniques - probably used a 3 pound Ford wrench to try to free them up before they attempted to pull them. Even good shops can hire lousy people -

Regards,
Steve
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1968 Z28 BRG/W
1969 Z28 X77 LeMans/W
1969 X66 L78 Cortez/BVT
1969 Z11 L48
68Zproject
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« Reply #8 on: March 14, 2014, 11:05:09 AM »

My best guess is the guy's son did the work and either ran the tap too fast or used a dull one and the heat build up cracked it.  I pulled them out but didn't notice the cracks at that time. 

Thanks for the recommendations and I'll see if I can get this sorted out and order some parts today.
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68Z28
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« Reply #9 on: March 15, 2014, 03:18:25 PM »

My best guess is the guy's son did the work and either ran the tap too fast or used a dull one and the heat build up cracked it.  I pulled them out but didn't notice the cracks at that time. 

Thanks for the recommendations and I'll see if I can get this sorted out and order some parts today.
I'd be very surprised to believe a dull tap caused that much heat to cause cracking or the cause was tapping too fast, but I've been surprised before.
Now, I do not know anyone who rebuilds those mouse motors with that weak link still intact, i.e. pressed in studs. You stated a balance issue but not sure how bad that was and how you found out or the crank was not machined properly, are you referring to the past engine build where you ran it for 4 years or recently they machined it incorrectly. What was wrong with the crank? Now I'm not picking as you sound just like me some years past. Smiley One of the first things I would do is find a reputable shop that knows engines and has the capabilities to do their own machining. Our original 68 302 did 362hp at 6700 rpm, and that was with a crane blueprint cam purchased new in 1983 and stock heads and manifold. Was everything easy, no! Why, the first time it was rebuilt with different hands they messed things up. Example, had the heads checked and valve job done at a local NAPA that does a lot of machine work. Later when I took the heads to the new engine builder they pulled a vac. check and two seats on one head and one seat on the other leaked. Cause, seats had chatter. The engine machine work done many years ago (engine was never fired) was more upsetting as our original MO was stock bore and did not need bored so it was lightly honed back then yet they used a ridge reamer at the top of the bore. Guess what, they cut in so deep on some cylinders the top land was going to very close so we had to bore .03" over and purchase new pistons. All of this was carefully shown to me by who I now use and swear by.  So your discussion brings up memories as I've been there and done that.
That is why I'm suggesting you hold off any purchases and find yourself a reputable shop. Find out exactly what you have, and what you need and why. Ask them to show you and explain. When they rebuilt our 302 I was there for the short-block assembly. When it was broke in and dyno'ed I was there which to me gives credibility to the shop.
Good luck 68Z brother.......
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68Zproject
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« Reply #10 on: March 16, 2014, 10:56:35 AM »

surprised to believe a dull tap caused that much heat to cause cracking or the cause was tapping too fast, but I've been surprised before.
Now, I do not know anyone who rebuilds those mouse motors with that weak link still intact, i.e. pressed in studs. You stated a balance issue but not sure how bad that was and how you found out or the crank was not machined properly, are you referring to the past engine build where you ran it for 4 years or recently they machined it incorrectly. What was wrong with the crank? Now I'm not picking as you sound just like me some years past. 


The machine shop I normally use is one of the best, but he was closed for a few weeks and I couldn't get the heads to him in time, so I went with the guy who put the engine back together after checking it out 4 or 5 years ago.  I have since heard that he's had many issues with doing bad jobs.

I stayed with the pressed in studs, originally, because I never planned to take it over 6k.  When the throttle stuck and I had to push in the clutch, I watched in horror as the tach went to 8500.

The engine always seemed to shake and not feel very smooth and I suspected it hadn't been balanced. The only way I found out about the balance issue was because when I found the head to be cracked I knew it would be a while before I would be able to get them back on.  Since it was approaching winter I decided to tear the engine down and check out if everything was ok because of the rep with the guy that did it.  The good machinist is the one that found all the problems.  He said it was the worst out of balance he had ever seen.  Of course with hindsight, if I had just gone to him in the beginning, all I would have had to do was put the screw in studs in the head.  He said he uses a new tap on every job and said if it gets too hot while tapping, it can crack the bosses. 

He showed me the crank and it had rub marks on the sides of the counter weights and the rod journals were rough around the inside edges.  He said it was welded (badly) and the machining process was sloppy and gouged the inside of the journals which is why my bearings were grooved.  It also was wearing unevenly.  So the combination of the bad machine work and the out of balance really made the engine shake at idle and above 5k.

Everything is good to go now, but I'm having a hard time getting all the parts needed from one place like Summit.
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68Z28
z28z11
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« Reply #11 on: March 16, 2014, 12:35:23 PM »

"He said he uses a new tap on every job and said if it gets too hot while tapping, it can crack the bosses".

Admirable, but before I would start the tap, I would make sure the starting hole size is correct for the thread limits. Too small of a starting hole size can put too much pressure on a thin walled part or feature, which could cause cracking (or usually tap breakage). Force it, and somethings got to give. Should be using a bottoming style/blind hole tap as well - a plug will tend to torque into the part, another accident waiting to happen.

Tap speed is actually pretty low in surface feet/minute - if the hole size is right, and you use Tap Eze or a tapping lubricant of any type, cutting zone temperature are cool to the touch. Heat should come out with the chip -   

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1968 Z28 BRG/W
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1969 X66 L78 Cortez/BVT
1969 Z11 L48
68Zproject
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« Reply #12 on: March 16, 2014, 04:51:21 PM »

Like I said, the guy who did the job could have done all the above wrong, I just don't know for sure. All I did know at the time is I didn't remember seeing any cracked bosses when I took them off to be done, but all is well with them now.
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68Z28
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« Reply #13 on: April 02, 2014, 02:40:05 AM »

  In the old days a lot pf shops would just pin the studs. It was a cheap alternative to the machining and tapping for screw-in studs. I don't know if it's even done anymore, but your problem made me recall that a lot of studs got pinned in the '60s and '70s. Good luck and I hope everythnig is good now.
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68Zproject
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« Reply #14 on: April 02, 2014, 09:32:50 AM »

I got all my parts a week ago but am held up because I need to use a ball hone and can't find anyone I know that has one.  I'm not in a position to be able to go out and buy a $70 hone to use just once so I'm looking for one still.
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68Z28
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