CRG Discussion Forum
Camaro Research Group Discussion => Maintenance => Topic started by: vabeach56wagon on December 12, 2018, 02:57:30 PM
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Is that PV absolutely necessary or have others plugged it?
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It's not necessary per say, but if you block it, you have to jump roughly 6 jet sizes in the rear to compensate for it.
I've run mine with and without. Quite frankly I like mine with the rear power valve in place. The throttle transition from primary to secondary is much smoother, especially when you whack it, and I liked the AFR a little better with the PV while at the same time not having such a big spread in jet size from primary to secondary.
With the wide band, and rear power valve removed, and jetted 6 sizes up on the rear, my WOT AFR was 12.9 Being at 5,000 ft that's a bit too lean for my liking considering that number jumps a full point at sea level. When I went back to stock rear jetting and reinstalled the 6.5 power valve, the WOT was hovering around 12.5 So it would appear that removing the PV and jumping the rear jets 6 sizes really wasn't quite enough to give the same results.
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I'm at sea level. Current Street Avenger Holley has a 6.5PV on primary with 70's; 78's on secondaries. Plugs clean and milk chocolate.
What would you suggest be the starting points with the 4053?
Stock Z intake; stock exhaust manifolds; chambered exhaust; cold lash at .026; 16* initial 36*total at 2200; 19*vacuum; RJ127C's at .040. Stock 11-1 and std. bore (to my knowledge).
paul
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The original 4053 jetting was 68 front and 76 rear. 6.5 PV up front and either 6.5 or 8.5 rear PV.
With what sounds like a fairly stock description of a 302 with a more aggressive timing curve, they do respond pretty well to a little more front jet, even with the manifolds in place. Bumping the front up to 72's works pretty well at sea level. I'd probably leave the rear alone with maybe the only change being a purple or long yellow secondary spring.
If you find this works well for your combo you can dig deeper. The early Z intake runner design responds to stagger jetting. Every engine might be slightly different as to what it likes, but mine showed best results when jetted up 2 sizes on the driver side of the carb. I also found mine needed the idle feed restrictors enlarged slightly, even up here at 5,000 ft, which gave it a smoother idle, produced more vacuum. It's fed 91 octane with ~10% ethanol, that's the best we have. I found this gas just needed more idle fuel to make mine idle happy.
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How much to Jet-Up when removing a Power Valve imho depends on the AREA of the Power Valve Channel Restrictions in the Metering Block. One method to determine how much to Jet-Up when removing a Power Valve is to Measure the Diameter of the Power Valve Channel Restrictions that are in the Metering Block behind the Power Valve using Pin Gauges, Welding Tip Cleaners, or Number / Letter Drill Bit Shanks, and Calipers. Calculate the AREA of 1 of the Power Valve Channel Restrictions, Pi (3.1416) times Radius Squared, and add that AREA to the AREA of the original Jet Size Hole Diameter to determine the "correct" New Total AREA and Jet Size with the correct increased Jet Hole Size that has that increase AREA.
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Our Holley 4053 repro carb showed up yesterday: jetted 68 primary; 76 secondary; 6.5PV primary; 8.5PV secondary. I haven't opened up the secondary vacuum can to check the spring. I did find that the inlets are for 5/16" lines and fittings. I switched out the 3/8" inlets from the current Street Avenger. Were the original fuel lines 5/16"?
Thanks
paul
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Secondary spring will most likely be a stock plain steel spring.
Yes originally the inlets are 5/16. 3/8 line from pump to brass "Y" block, and 5/16 line from the "Y" block to the carb.
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To be "correct" I guess I should step down the lines from the Y block....Nah, I'll keep the 3/8".
paul
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I think the two 5/16" lines to the carb can MORE than handle the fuel coming thru the 3/8" feeder line from the fuel pump. :)
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Gary is correct. I've gone 11.40's at 118 mph through the factory 3/8 to 5/16 feed line setup on my 454 chevelle so it would be more than enough to feed a 302.
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I am at a loss as to why the PO of this car ran 3/8" inlets...but he did. Am still trying to figure out which application has a 3/8" Yblock.
(http://pic20.picturetrail.com/VOL15/632342/24816460/414097764.jpg)
paul
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You can buy the larger stuff that "appears" factory from Inline Tube. I just did a complete 1/2" line setup, feed and return, in stainless for a 455HO Formula I'm restoring, complete with spring wire, from Inline Tube. Looks stock(ish) and fits nicely. Other places like RobbMC offer fuel tank pickups with 1/2" or 5/8" that work with the stock 0-90 ohm gauge. Can even take it further, as I did with the Formula I mentioned, with a Tanks Inc fuel tank baffled for an in-tank electric pump to support bigger HP, also larger for 3 gallons more capacity and still "appears" stock, but runs quiet and OEM reliability.
Lots of sneaky stuff can be done ;)
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Hmmmm.... I like sneaky stuff like that. :)