CRG Discussion Forum
Welcome, Guest. Please login or register.
Did you miss your activation email?
August 29, 2014, 09:09:43 AM

Login with username, password and session length
Search:     Advanced search
Welcome to the CRG Discussion Forum!
Forum registration problems: Make sure you enter your email correctly and you check your spam box first. *Then* email KurtS2@gmail for help.
103627 Posts in 12179 Topics by 4697 Members
Latest Member: greygoose01
* Home Help Search Login Register
+  CRG Discussion Forum
|-+  Camaro Research Group Discussion
| |-+  Maintenance
| | |-+  1969 Z/28 DZ 302 overbore to .040? Piston Source?
« previous next »
Pages: 1 [2]  All Print
Author Topic: 1969 Z/28 DZ 302 overbore to .040? Piston Source?  (Read 5455 times)
doomer
Member
***
Posts: 45



View Profile Email
« Reply #15 on: July 24, 2013, 10:06:07 AM »

Well, got the bad news this morning that he had to go out to 0.060 anyway. I know this is not good, but can somebody share some wisdom as to what I should do at this point? This is not a trailer queen, I drive her on weekends to local shows and cruise-ins. I want to enjoy my car without ruining it for good. I don't want to put a crate engine in it. I'd rather drive a 'real' Z/28. On the other hand, If that means ruining what's left of a numbers matching '69 Z/28, I'd rather sell her to someone who will make a trailer queen. (A good home, so-to-speak.)

Pretty bummed out.
Logged
69Z28-RS
Hero Member
*****
Posts: 2335


owner since '76


View Profile Email
« Reply #16 on: July 24, 2013, 10:11:37 AM »

You can always 'sleeve' it back to std..   it's expensive, but some racers used to do that with their race engines...
Logged

Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
JohnZ
CRG Member
*****
Posts: 4075


View Profile Email
« Reply #17 on: July 24, 2013, 11:32:24 AM »

My DZ 302 is out and apart for the first time since I got it. The block is already at .030 and needs to go a little further.

    Not trying to be nosey, or reinvent the wheel, but what does the block measure out as ? When I rebuilt my '69 in '75, the original pistons were worn, but the block was great after 50K miles - the high tin/nickel content in the block casting did what GM bumped the percentages up for; kept wear to a minimum in the block, pistons become the wear parts.
    
Regards,
Steve

Not according to JohnZ. All the added tin and nickel was dropped because it didn't improve the blocks.

" the "010-020" raised numbers that indicate the 0.1% and 0.2% tin and nickel content in some blocks; that was an extended tryout where the added tin was to improve machinability and the added nickel was to improve bore wear. It was discontinued when the promised warranty improvements failed to appear, and the added cost was no longer justified."


And, as it turned out after further research with the Saginaw Foundry (now called Saginaw Metal Casting Operations, part of the GM Powertrain Division), the old story many of us were led to believe about the 010/020 describing the tin/nickel alloy turns out NOT to have been true at all, although the magazines thought it was true and continued to publish the tale, and still do today.

Actually, the "010/020" cast into the front bulkhead under the timing cover turned out to be simply the identifier for the foundry pattern for the front bulkhead, which was shared by the 3970010 (350) and 3970020 (307) blocks; it had nothing to do with the iron alloy, which was never altered for any particular production block (although the alloy was altered for some later low-volume GM Performance Parts over-the-counter "Bowtie" blocks).
Logged

'69 Z/28
Fathom Green
CRG
z28z11
Hero Member
*****
Posts: 596


View Profile
« Reply #18 on: July 24, 2013, 06:56:47 PM »



Not according to JohnZ. All the added tin and nickel was dropped because it didn't improve the blocks.

" the "010-020" raised numbers that indicate the 0.1% and 0.2% tin and nickel content in some blocks; that was an extended tryout where the added tin was to improve machinability and the added nickel was to improve bore wear. It was discontinued when the promised warranty improvements failed to appear, and the added cost was no longer justified."

[/quote]

Mine must have been one of the trials - less than .0002 (read as 2/10,000's, not .002) taper in the bore after 50K plus miles - machine shop remarked it was extremely straight, considering the wear on the pistons. BTW - a lot of 010 blocks are around with just that percentage cast on the block surface. Bores usually look pretty good compared to blocks like my 2 - 678's - heavy ring lands that took at least a .030 overbore.

Regards,
Steve
Logged

1968 Z28 BRG/W
1969 Z28 X77 LeMans/W
1969 X66 L78 Cortez/BVT
1969 Z11 L48
z28z11
Hero Member
*****
Posts: 596


View Profile
« Reply #19 on: July 24, 2013, 07:09:46 PM »

Well, got the bad news this morning that he had to go out to 0.060 anyway. I know this is not good, but can somebody share some wisdom as to what I should do at this point? This is not a trailer queen, I drive her on weekends to local shows and cruise-ins. I want to enjoy my car without ruining it for good. I don't want to put a crate engine in it. I'd rather drive a 'real' Z/28. On the other hand, If that means ruining what's left of a numbers matching '69 Z/28, I'd rather sell her to someone who will make a trailer queen. (A good home, so-to-speak.)

Pretty bummed out.

Doomer -

If it's the original, build it and drive it. Or, build a driver 302 motor and enjoy it anyway. Hot trick when I was growing up was to build a poor man's 301 using a 283 block bored .125 over - they usually ran really hot, but if the cores weren't shifted, they would last decently under pretty severe duty (rods and bearings were the limiting factors). Later model blocks didn't seem to suffer the earlier block's tendencies for core shifts - I've known a lot of .060 engines that ran, and continue to run, very well.

Strictly my own opinion,
Steve
 
Logged

1968 Z28 BRG/W
1969 Z28 X77 LeMans/W
1969 X66 L78 Cortez/BVT
1969 Z11 L48
tmodel66
Hero Member
*****
Posts: 1212


View Profile Email
« Reply #20 on: July 24, 2013, 09:16:13 PM »



Mine must have been one of the trials - less than .0002 (read as 2/10,000's, not .002) taper in the bore after 50K plus miles - machine shop remarked it was extremely straight, considering the wear on the pistons. BTW - a lot of 010 blocks are around with just that percentage cast on the block surface. Bores usually look pretty good compared to blocks like my 2 - 678's - heavy ring lands that took at least a .030 overbore.

Regards,
Steve




And, as it turned out after further research with the Saginaw Foundry (now called Saginaw Metal Casting Operations, part of the GM Powertrain Division), the old story many of us were led to believe about the 010/020 describing the tin/nickel alloy turns out NOT to have been true at all, although the magazines thought it was true and continued to publish the tale, and still do today.

Actually, the "010/020" cast into the front bulkhead under the timing cover turned out to be simply the identifier for the foundry pattern for the front bulkhead, which was shared by the 3970010 (350) and 3970020 (307) blocks; it had nothing to do with the iron alloy, which was never altered for any particular production block (although the alloy was altered for some later low-volume GM Performance Parts over-the-counter "Bowtie" blocks).
Logged

Daniel  
'69 SS 350/4 speed  Fathom Green--POP
doomer
Member
***
Posts: 45



View Profile Email
« Reply #21 on: July 25, 2013, 12:41:07 PM »


If it's the original, build it and drive it. Or, build a driver 302 motor and enjoy it anyway. Hot trick when I was growing up was to build a poor man's 301 using a 283 block bored .125 over - they usually ran really hot, but if the cores weren't shifted, they would last decently under pretty severe duty (rods and bearings were the limiting factors). Later model blocks didn't seem to suffer the earlier block's tendencies for core shifts - I've known a lot of .060 engines that ran, and continue to run, very well.

Strictly my own opinion,
Steve
 

Thanks Steve. Good advice, and I'll be sticking to the matching numbers oath, to "do no harm while enjoying the hell out of it". Smiley Going with JE Pistons and rings. Thanks folks, for all the great advice. I'm sure I'll have more questions as I put her back together over the next few weeks.

Shane
Logged
rsr
Member
***
Posts: 103


View Profile Email
« Reply #22 on: August 02, 2013, 08:30:47 PM »

 Sure everybody wants a standard bore block but if you got a overbore .040 -.060 and need .010-.020 more to clear it up for a good fit why not just get custom pistons vs having sleeves installed? Many piston manufactures can easly make what you need and you don't spend the extra cash for new pistons and sleeves??A .125 is 1/8 of a inch! Just a different way to view this problem IMHO.............
Logged
Pages: 1 [2]  All Print 
« previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!
Page created in 0.437 seconds with 18 queries.