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Author Topic: 4053 DZ carburator  (Read 612 times)
cam69aro
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« on: February 06, 2014, 08:02:00 PM »

i read on the internet a few years back ( i know, don`t believe what you read on the net) that DZ carbs were milled out to a true 800 cfm by Chevrolet. i would guess the reason being truth in advertising ? was wondering if that rumor is true ?
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Eldon W
1969 Black Z28
X77 03E 38,000 miles
unrestored
Ed Bertrand
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« Reply #1 on: February 06, 2014, 08:10:15 PM »

Read THIS, especially footnote number 2.

Ed
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ko-lek-tor
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« Reply #2 on: February 06, 2014, 08:10:33 PM »

I have had a couple of these carbs and have seen no evidence of such. I'll stick my neck out (until proven otherwise) that this is a bunch of "horse hockey". These cars were mass produced, not blueprinted.
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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
cook_dw
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« Reply #3 on: February 06, 2014, 08:48:28 PM »

Honestly we are talking about 20 cfm.  When working at Holley; there were/are variances when flowing a carb that will be as much as a couple 100 cfm.  Usually you use the mean of a batch and come to your cfm flow.  USUALLY..  Has there been carbs that have been manufactured that were suppose to a certain cfm and fell short?  Of course, its like any testing batch testing.  All the tolerances that are used (especially back then) if you had a base plate that was at its min tolerance and a venturi  at it max then you will not get optimum flow because you will create turbulence.  When testing you want best case scenerios to get the best results possible.   
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Darrell Cook

1967 LeMans Blue SS/RS L35 clone
1968 Rallye Green SS L78 - unrestored original
1968 Matador Red Z28
Mike S
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« Reply #4 on: February 06, 2014, 09:07:03 PM »

 I'd be very surprised if a stock 302 could flow 800CFM when using stock exhaust manifolds.

Mike
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67 LOS SS/RS L35 Hardtop - Original w/UOIT
67 NOR SS/RS L35 Convertible - Restored
z28z11
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« Reply #5 on: February 06, 2014, 09:42:23 PM »

Hard to say if they would flow all of 800, but the combination of large valves, small chambers, big cam and the 472 intake could handle quite a bit. One problem that I know mine had (until I swapped it out for a 850 DP) was a noticeable hesitation, almost a bog, due to the small accelerator pump shot off idle. Fix turned out to be swapping the squirters, or drilling them: ultimate would be to use a Reo 50cc pump and cam, which would give enough fuel to get through the flat spot.

I ran the 850 for years - never a problem with loading up, or bog - of course, the 12.5:1 Manley's and the Sig Erson stick I installed in '75 may have stilted the results somewhat. The 302 would rev to near 8000 in stock form; I did this numerous times, until I snapped a stock spring on cylinder 4 (changed it in the parking lot of my dorm). Still have the spring, and no, it didn't drop the valve. Dang lucky -

Regards,
Steve
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1968 Z28 BRG/W
1969 Z28 X77 LeMans/W
1969 X66 L78 Cortez/BVT
1969 Z11 L48
69Z28-RS
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« Reply #6 on: February 06, 2014, 11:16:59 PM »

And...   it was a tiny percentage indeed of early Z28s that ran the 'stock exhaust manifolds' more than a few days to a week... MANY were swapped out the first or second day of ownership.  I have a 'first day' take off set that I plan to install when the 302 goes back in..

That brings up a question:  What is the best way to preserve such *perfect no pit manifolds* in such a way as to get full points at the Camaro nats in the original classes?  I've used Calyx (temporary solution but looks too black) and Eastwood Stainless Steel paint (in the past on other manifolds, but neither of those give a totally correct 'look' in my view, but is there something better?
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
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cam69aro
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« Reply #7 on: February 06, 2014, 11:33:41 PM »

i guess foot note #2 pretty much summed it up, thanks for the heads up on that Ed, that is one of the reasons i joined this site. The reason i asked was my carb had been milled at some point before i got the car. I bought the car with an 850 Holley and single plane intake but the seller had to have it back and gave me the stock carb and intake in return but it is still in need of rebuilding. I brought the carb to a race car driver/engine builder and he noticed the milling right away. He said the shafts that the butterflies went on were milled down. I had read the rumor about that time and thought it was how it should be. Well i guess not, so now it`s time for the carb to go on a visit to Jerry M to get it back to how it should be.  I am running an out of the box 750 cfm Holley for now so i can use the car but want it as it should be. Thanks for the input guys, stay warm. Im freezing here in Minnesota and can`t wait to get my Z out for some summer fun.
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Eldon W
1969 Black Z28
X77 03E 38,000 miles
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Vince
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« Reply #8 on: February 07, 2014, 06:23:04 PM »

I read in an article in a car magazine or book that Holley rated the 4053 at 780 cfm and GM rated it at 800 cfm.  It didn't go into any further detail why each company rated the same carb differently. 
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Azure1969Z/28
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« Reply #9 on: February 08, 2014, 12:16:40 AM »

I have had a couple of these carbs and have seen no evidence of such. I'll stick my neck out (until proven otherwise) that this is a bunch of "horse hockey". These cars were mass produced, not blueprinted.
"horse pucky" or "bull pucky" not "horse hockey" Smiley at least where I'm from
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