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Old 05-04-2020, 07:20 PM
aaronkl84corvett aaronkl84corvett is offline
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Default stagger jetting for stock DZ302 with headers?

I know a good baseline jetting for a stock cam/stock head DZ302 is 72-76
i just installed headers and wondering how much I should jump to compensate for the new headers and Spintechs mufflers - essentially an almost no back pressure exhaust?

i also have heard of stagger jetting to compensate for the Z28 intake runners.... any suggestions?

Stock 4053 holley

No drag race plans - just a good street driver -
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Old 05-04-2020, 08:28 PM
x33rs x33rs is offline
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I've likely went over this before, maybe here, not sure.

Yes stagger jetting for the DZ302 if using the stock intake is worth while. I have mine stagger jetted and this particular intake likes the driver side up on both front and back. How much is dependent but I found on mine it liked 2 sizes up on the driver side.

So for me, I'm running headers and a 2 1/2" mandrel bent Pypes transverse exhaust system. I'm also up at 5,000 feet elevation and I routinely drive down near sea level. So I look for a happy spot where the AFR's are a little richer up here, and still safe at sea level so I don't have to keep opening up the carb.

I run 70-72 front and 76-78 rear, with the passenger side of the carb having the lower jetting. I keep both power valves at 6.5
This keeps the engine a pinch on the rich side up here but nothing horrible as the plugs look nice and it still returns good mileage with DA's in the 7,000 foot range. When I drive down to sea level where DA's are around 3500 feet everything is nice and happy.
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Old 05-04-2020, 08:36 PM
aaronkl84corvett aaronkl84corvett is offline
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Great thanks - thats pretty much exactly what I was thinking -
I have 72-76 now in it - so a little tweak should help

Thanks
Aaron
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Old 05-04-2020, 08:47 PM
x33rs x33rs is offline
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72-76 square is a pretty good spot to be, these engines respond to it.

I assume you are somewhere near sea level or where DA's don't get out of control. If so, and with headers and free flowing exhaust, it will likely respond to 74-78 on the driver side.
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Old 05-04-2020, 09:06 PM
aaronkl84corvett aaronkl84corvett is offline
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I'm in Michigan - so we're at or below sea level LOL
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Old 05-05-2020, 07:11 AM
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GaryC GaryC is offline
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A little bit of info from the CRG site.

http://www.camaros.org/forum/index.p...pic=2196.0;all
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Old 05-05-2020, 01:24 PM
RALLY RALLY is offline
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Quote:
Originally Posted by aaronkl84corvett View Post
I know a good baseline jetting for a stock cam/stock head DZ302 is 72-76
i just installed headers and wondering how much I should jump to compensate for the new headers and Spintechs mufflers - essentially an almost no back pressure exhaust?

i also have heard of stagger jetting to compensate for the Z28 intake runners.... any suggestions?

Stock 4053 holley

No drag race plans - just a good street driver -
I run 74-78 jetting on my stock 302 intake. Runs great. Stagger jetting works well if you are looking for some drag strip competition and looking for a bit of an edge over your competitor. Just my two cents.
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Old 05-05-2020, 03:03 PM
x33rs x33rs is offline
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I'll elaborate some more since mine isn't "as built" from the factory.

I built mine with intention to run pure stock per rules here
https://www.psmcdr.com/rules

I've done a few engines this way with a few liberties taken to keep them as nice street engines.

Without getting into all the details it's essentially for all purposes here, a stock DZ 302. The cam is "tweaked" a bit and compression is exactly 11:1. Stock heads, intake, carb etc...no porting.

We only experimented with stagger jetting to see what it might be worth. Looking at the intake runners, both front and rear from the driver side are longer, so it made sense to jet that side of the carb up. It was worth a pinch of power on mine. After going 2 sizes I tried 2 more and didn't find any more gains. So I stayed with the 2 size differential.
This shouldn't let any secrets out as it's really not all that hard to look at intake runners and figure out where more jetting might be beneficial. I've been stagger jetting BBC's for years with decent results so I thought I'd experiment on the little DZ and was pleasantly surprised.
On power valves I like the 6.5's front and rear. I've tried blocking the rear and going up 4 sizes in the back and even 4 sizes wasn't rich enough to compensate for not having the power valve. WOT AFR's went from 12.4 to 12.8. Still safe and ran fine but if you're trying to keep the same air fuel ratio without the rear power valve you might want to step up 6 jet sizes.
I ended up going back with the rear power valve but either way works well.
So as I mentioned I ended up with 70-72 front jets and that's because I spend most of my time running around at 5000 feet elevation. When I go to the track I'll likely bump that up to 72-74 or maybe more depending on the weather, but may just leave the back alone as I have WOT pretty rich as it is at this elevation.
Keep in mind this is actually primarily a street car, my wife drives it daily to and from work, I'm just a fanatic about tuning and I like my stuff to run. With this carb setup the throttle is crisp, clean and quick. I run a fairly aggressive timing curve as well, with 18 initial, 18 centrifugal, for 36 total, all in at 2600 rpm, and I have an adjustable vacuum advance with my own modifications welding the slot for a specific movement I look for that limits total vacuum advance to about 10 degrees, and it starts pulling around 6 inches of vacuum, done around 8 inches, so it's rather quick, again since I'm up at 5,000 feet the engine makes 3-4 inches less vacuum up here. Idles around 9-10 inches, where at sea level it's 12-13 inches.
This setup runs perfectly on our crappy 91 octane and has logged over 30k miles to date. Hope this helps.
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