Author Topic: 1969 302 DZ Heads  (Read 8006 times)

Jerry@CHP

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Re: 1969 302 DZ Heads
« Reply #15 on: March 12, 2007, 03:28:53 AM »
Fixing cracked cylinder heads is dicey at best.  Most of the time when it's important, the "cold lacing" process is about the only thing that can be done......and that doesn't work all the time. 

We are trying to save a 1969 Z28 original block now.  One of my clients bought a car and when we got the engine apart, it was cracked in the lifter galley.  Botched repair and the whole nine yards.  It's a mess but we will do our best.

Jerry

firstgenaddict

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Re: 1969 302 DZ Heads
« Reply #16 on: March 12, 2007, 12:55:39 PM »
Sounds like it froze... that happened to my boat when I didn't winterize it one year... made the 454 a nice anchor... live and learn... I was being lazy and it cost me... BIG TIME...
James
Collectin' Camaro's since "Only Rednecks drove them"
 
Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
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1968RSZ28

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Re: 1969 302 DZ Heads
« Reply #17 on: March 12, 2007, 05:39:48 PM »
Because there's VERY little metal left between the valve seats on 2.02" heads as it is, and it's very easy for a shop not intimately familiar with these castings to go through into the water jacket when cutting the recess for the seat, at which point the heads are scrap. The seats are NOT necessary unless you're towing a trailer at 100mph all day long or the engine's going in a boat.

Thanks John.  I've never heard that before!  My car has been stored for 26 years and I have not "fired her up" because everybody tells me to install hardened valve seats before I do.  So lets see... I need to change all the fluids and install a new battery...   ;D

Paul

melav8r

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Re: 1969 302 DZ Heads
« Reply #18 on: April 25, 2007, 02:05:36 AM »
Is using a certi machine all that's required when openong up a set of 1.94's to 2.02's? Is there any additional unshrouding required?

GaryL

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Re: 1969 302 DZ Heads
« Reply #19 on: April 25, 2007, 04:17:18 AM »
delete
Gary

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JohnZ

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Re: 1969 302 DZ Heads
« Reply #20 on: April 25, 2007, 04:40:30 PM »
Is using a certi machine all that's required when openong up a set of 1.94's to 2.02's? Is there any additional unshrouding required?

The heads built as 2.02's at the factory had an extra unshrouding cut on the chamber wall adjacent to the intake valve; if you convert 1.94's to 2.02's and don't make the unshrouding cut, they'll flow less air than they did with the 1.94's. Photo of a factory 186 2.02" chamber below.
'69 Z/28
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melav8r

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Re: 1969 302 DZ Heads
« Reply #21 on: April 25, 2007, 07:57:01 PM »
I understand that but does the certi machine cut that extra material or is additional unshrouding necessary after using a certi machine?

olympic69

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Re: 1969 302 DZ Heads
« Reply #22 on: April 26, 2007, 05:18:48 AM »
I understand that but does the certi machine cut that extra material or is additional unshrouding necessary after using a certi machine?

I believe it is all about how it is set up- the answer being yes, maybe or no! The Certi machine makes cuts, not grinds so it is just another part ( step) of the operation, but might not be done if not specified ( sorry about the crappy explanation- its late!).The bottom line is it needs to be done if you go to 2.02, so see that your machinist knows that- the Chevy Power book says you need to go for a 2.34" total profile width. Also, David Vizard has an excellent book on working the -186 casting for performance.

Good luck-
Rob
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68Zproject

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Re: 1969 302 DZ Heads
« Reply #23 on: April 27, 2007, 03:55:11 PM »
Would this Vizard book work for the 291 68 Z heads?  Were the chambers the same for 68 and 69 Z heads?
68Z28

olympic69

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Re: 1969 302 DZ Heads
« Reply #24 on: April 27, 2007, 05:51:02 PM »
It is a very good book, applicable to all of these late '60's- early '70's 64 cc heads which we are speaking of, with flow figures, Mods., a really good book plus has some great stuff on the aftermarket heads as well.

ISBN is   0-87938-547-2

How to build and modify small block Chevy Cylinder heads David Vizard , 1991 MBI Publishing Co
Rob
Olympic Gold X33

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