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New Anti-reversion devices
http://racingfuelsystems.myfunforum.org/viewtopic.php?f=22&t=1281
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Author:  Mattax [ Sun Sep 11, 2016 4:30 pm ]
Post subject:  New Anti-reversion devices

Got these 4-2-1 anti-reversion devices made for my car. Some of you may have seen the 340 header thread over in ST Very pleased with how it runs (and fits). Right now its seat of the pants evaluation, but the engine seems happier. One autocross, then returned to full time driver for the past several months. So no full throttle runs, just idle to mid rpm, although plenty of long part throttle hills, some pretty deep into the throttle (3-4"Hg on the gage).

Coloration suggests that the exhaust temps are uneven - distribution ?

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Unfortunately the spark plugs are old (and the engine is burning some oil) so am having doubts about their value. I do have more photos if that would be helpful. As always, open to suggestions.
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Author:  tuner [ Sat Oct 01, 2016 12:13 pm ]
Post subject:  Re: New Anti-reversion devices

It looks richer on the 1-4-6-7 side than the 2-3-5-8 side.

"the wind pressure is greater on the box side than on the neck side" (A. Guthrie)

I forget, is that an LD-340 intake? The big Mopar book has some stagger jetting information about it.

Is the exhaust heat open or blocked?

Author:  Mattax [ Sat Oct 01, 2016 2:11 pm ]
Post subject:  Re: New Anti-reversion devices

Exhaust crossover open. Oil splash baffle installed in the valley.

Yes. Intake is LD 340 that someone removed all the markings from, pictured below. Marked the cylinders each plenum feeds so I can keep it straight in my head.
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In the Engine Speed Secrets book there are a couple of racing setups for the LD340 although none with a list 3310. The closest is the the "outdated" tip using a 4553. The 4553 is not on the Holley List but I'm guessing it was a vacuum secondary 4150 based on the nearby list numbers. So maybe it can be assumed that at least the primaries should be stagger jetted with leaner on the driver side and richer on passenger side. That would fit what the plugs are suggesting.

Bracket Racing: LD340 modified by boring the risers for a Thermoquad and then cutting down the divider to 3/8".

Super stock: LD340 with divider cut down to 3/8" with Holley list 4788 (830 cfm double pumper)
This is a stagger jetted and notched setup - which I have always assumed is specific to the opened up plenum.
Front of Engine ^
Booster notches 3/16" h x 3/8"w facing to the sides on all four boosters.
PMJ 82 78
SMJ 88 86
(No power valves)

Under "Outdated Jetting Tips" there's the following.
340 with Holley 4150 List 4553 on LD-340 manifold (cold) with headers.
PMJ 77, 80
PVCR .093" .093"
Secondary 88, 88

305-340 with LD-340 manifold full race engine, no aircleaner, 830 cfm Holley carb
PMJ .081, .080 (probably editing errors and should be #81, and 81 sizes ?)
SMJ .088, .086
PVCR .093

*Found an original typed Carb-Manifold tip #34 on-line and its dated 1977. So the "outdated tips" must have been from an even earlier bulletin.

Author:  tuner [ Sat Oct 01, 2016 2:36 pm ]
Post subject:  Re: New Anti-reversion devices

Do you have a set of plugs that only have WOT time on them, at least track time with no street time? The part-throttle is going to be different than the WOT. Can you see the fuel rings down on the side of the ceramic?

In some 4150 carbs the .093" PVCR is used in metering blocks with the emulsion tube. The Hemi Cross Ram carbs and some short track Hemi 780 carbs have metering blocks with the tube (and L-88 & ZL-1 carbs and some Ford skunkworks, as well as the R-4575 1050). Because the E-tube adds some restriction to the well, the blocks with the tube need a larger PVCR than without the tube, but, because the tube is shorter and the end is just above the PVCR, it doesn't restrict as much as the idle tube which extends the full length of the well down to the jet, .

Author:  Mattax [ Sat Oct 01, 2016 4:00 pm ]
Post subject:  Re: New Anti-reversion devices

Quote:
Do you have a set of plugs that only have WOT time on them, at least track time with no street time?

Unfortunately not. Not too hopeful I will before the tracks close for winter - waiting for a new radiator, core leak that I've been holding with ginger. It lets go occassionally but then plugs up again - I wouldn't risk that on anyone's track.

Quote:
The part-throttle is going to be different than the WOT. Can you see the fuel rings down on the side of the ceramic?

I'll take another look in good light. Dark, dreary and wet today.
- Matt

Author:  tuner [ Sat Oct 01, 2016 4:05 pm ]
Post subject:  Re: New Anti-reversion devices

Mattax wrote:
Quote:
Do you have a set of plugs that only have WOT time on them, at least track time with no street time?

Unfortunately not. Not too hopeful I will before the tracks close for winter - waiting for a new radiator, core leak that I've been holding with ginger. It lets go occasionally but then plugs up again - I wouldn't risk that on anyone's track.

- Matt


Your local drug store might have some Sodium Silicate (Water Glass). An ounce or two of that will stop a lot of cooling system bleeding.

Author:  Mattax [ Sat Nov 12, 2016 1:32 pm ]
Post subject:  Re: New Anti-reversion devices - now fuel distribution

Here's a fresh set of plugs with with about 300 miles of street driving. I got caught in some traffic, so a little of everything. There were some roads with brisk low to mid rpm driving and some long hills with a part throttle load. On these the rpm would be in the 2500 range and vacuum as low as 5", but usually either around 8" or 12". Interstate highways never much about 3000, 2700-2800 more typical, with 16" Hg on some upslopes, 17.5" typical, around 20" on downslopes.

New spark plugs are Champion RN12YC which are a few steps hotter than the RN9s that had been in there.
Looks to me like the nose of the porcelain on 6 and 7 show some color; while the top of the shells of 4 and 6 have the least soot.
Are either of these useful indicators of idle to part throttle combustion?

PS. The quality of the plugs was a little disappointing. Most notcible was that the outer electrodes were not consistantly positioned over the center. I tried to straightened them out when regapping them all to .044"

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