I have read quite a bit on shear plates written by Andy Finkbeiner & David Vizard but haven't seen any in New Zealand yet.

I understand which way up they go & that they have a 6-7* taper in the bores but out of curiousity which way is the taper, bigger at the top or bigger at the botton? Cheers

Here's what I'm on about, the lip on the bore goes downward (top two examples wrong way up, bottom plate correct way up) & causes fuel shear which often gives more gain in HP than the minor loss in flow hurts HP.

And they are supposed to retard reversion, hence the groove around the shear lip.

Larger bore is on the "top",.....meaning the larger bore of the venturi sees flow first, as the flow passes thru the larger bore first, the smaller secondary, or tapered section of the bore is designed to contain/control the reversion pulse,....On the topic of AR control (Anti-Reversion)there was at one time an interest also in AR exhaust headers (anti-reversion), that had a reversion cone welded into the exhaust flange that bolted onto the exhaust port section of the head,....AR carb plates, manifolds with AR port designs, AR headers, while offering benefits, are best suited for engines that operate at continous RPM "bands" for extended time

Thanks DAYCLONA, that is the way I thought they would work buy I didn't want to take it for granted.

On the AR header thing David Vizard has positive things to say in his books about it including gains/losses from mismatching ports/manifolds & relationships between AR & balance pipes etc, interesting reading.

I run a factory appearing 383 in my Barracuda & intend building AR fittings into my headpipes in the next couple of weeks. (materials purchased today)

As for the shear plate it will probably be more of a winter (downunder) project as I want to incorporate the shearplate system into an insulating plate rather than an alloy one.

I have seen reversion so bad in some engines that it blew fuel back out through the carb and up into the hood scoop or cowl area. I'm a big fan of running the reversion plates on the larger cubic inch stuff especially the single 4 motors.

Reversion won't always have signs but a couple of others would be soot found in the intake runners or plenum area and on the bottom side of the carburetor base plate. Also any fuel above the boosters.

I run a factory appearing 383 in my Barracuda & intend building AR fittings into my headpipes in the next couple of weeks. (materials purchased today)

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Kevin I assume your running cast iron exhaust manifolds?,...that's possibly the reason your putting the AR cones in the headpipes,....which is ok,...but if you had the time, a sheetmetal gasket .060 (1.5mm) could be fashioned to portmatch the exhaust profile of the head, and individual AR cones could be welded to it to support their placement in the exhaust manifold passages,....IIRC from my studies of AR and the exhaust port head exit, the closer you can get the AR cone to it, the better the benefits of AR scavenging of the cylinder,....also if your running a straight thru muffler design, an AR cone in the inlet, will benefit the scavenging pluse in the main headpipe,.....but when it comes to the actual size/orifice dia, length/angle of the AR cones, best to consult some flow tables/charts that are in close comparison to your engines perimeters, plus your intended operation range (RPMs)

Mike

Thanks for the positive comments guys, I've taken your comments/ideas on board.

It's great to get positive comments especially from a couple of big players,

I get a bit board with some of the negative sh!t from people who have never done anything constructive in their life.

OK, well here is the first attempt at an anti-reversion cone for the inlet of my headpipe (outlet of HP manifolds)