Big hidden HP - from anti-reversion mods

In this, episode 142 of PowerTec 10 DV and crew delve into the little spoken aspects of power robbing flow reversions. Follow through on this and your typical V8 could be up in both low speed torque and hi-speed power. We are talking 25-30 lbs feet and at least as much in HP.

[pkuudsk]

The Yamaha YPVS was a similar idea. I can listen to David all day long, nothing is "new" anymore only a different way to do it.
This Legend carved his own way.

[masonprophet]

Truly grateful for people who have years and years of experience with things like this who are willing to take their time to sit down and make an easily digestible video for people like myself who are eager to learn these things. Thank you, sir.

[JC-gwyo]

I do remember back in the late 1970's, Cyclone Headers sold a set of "Anti- Reversion" headers. Instead of your anti reveversion "lip", their header used a short cone welded to the header flange. Their design was said to increase touque in the lower RPM range

[boomersuperbike]

You're spot on about the exhaust port. On our world Superbike spec engines the Akrapovic exhaust systems have this anti reversion built into the head spigots for the exhaust headers. Good stuff Dave. Thank you. We make more power on our Superbike engines usually when we flow the ports and build the floor with epoxy. We make over 225 rear wheel hp with 1000cc four cylinders turning 14-15, 000 rpm

[mblunch]

If I learn 1/10th of what this gentleman knows in my lifetime I will be happy.

[cliffwright]

This reversion is more evident in larger V8's with large cam overlap. John Kasse made a point to never use old, rusty inside headers. He figured out why his friends were getting oxide in the cylinders and killing their new engines.

[jeremiahfiek]

I did some of your anti-reversion mods to my riding lawnmower and it made a huge difference in working torque. After that I also bumped the timing up a couple degrees and then I narrowed the intake port about 30% and now that little 15.5hp ohv briggs single will mow 2 foot tall grass at about 1/3-1/2 max speed in my field without barely bogging at all and throws the grass out the chute 6-7 feet. I feel like they engineered these things to always leave you wanting more!

[blueyhis.zarsoff]

I remember an article in Hot rod many years ago with anti reversion cones built into the header flange at the head.
It all made sense.

[gavinpruden]

I built AR headers thirty years ago after reading an article by Dean lowery and of course David Vizard. The ones I built followed the work of Jim Fueling with AR cones in the first set I built for FE rail. Later street headers I built I just dropped the bottom of the header away and put a shelf parallel with the port bottom. With close lobe centre cams the engines would rev quite sharply and had a good low rev operation. Step headers do something similar. In the intake manifold the runners stayed very clean I noticed. I think I had to lean the carb or it would run rich with the cones.The magazine was popular hot rodding may 1980. I have followed you David since the English hot car magazine days and have learned a lot from your writings. Thanks.

[Christopher-rehl]

Thank you for your great knowledge Mr. Vizard. Great minds think alike and Mr. Brian Salter is also very knowledgeable sharing the same laws of flow dynamics. I always look forward to new videos from the both of you.

[talljohnsfunshop]

It's good to hear Jim's name mentioned. He was good friends with my auto shop teacher so I got to meet him a couple times. I was just out of high school when he was working on the old quad four program. He gave a set of headers that he made to my shop teacher that he had used for testing what he called AR cone and they were used on a SBC. I do remember a small improvement in milage and not much gain was felt by the seat of the pants but the shop teacher said it was noticeable when starting to pull a hill. He made the cone the same size of the port al the way around and the expanded the tube at the cone to go around it. I'm not sure if this is coming out right cause I know what I'm thinking but not sure if that's what I'm saying. All that typed it's something I haven't thought about for along time and DV you hit it perfectly what he told me. I hear people saying stuff like we're just old school but sorry this is old news to you and me but valuable new school that work for many. PS I own Jim's old motorcycle dyno. And another PS, when I was racing stockcars I needed a crank for my mopar chrysler called a kellog crank, nobody had one and when jim found out he called Kieth Black who I believe made them and arranged for me to go to his place and pick one up the next day. So that day I sat in kieths office for 15 minutes talk about stockcar racing and left. The price...free thanks to Jim. Anyway you knocked another out of the park

[ducssnv]

This is why we watch your videos, thanks DV.

[gerrypaulson]

I always learn so much from your videos even though I'm not racing anymore for the time being. But knowledge and information is always good.

[daledavies]

Chevy 6 guys use something similar. The ports are low to the deck surface on both intake and exhaust, causing a huge flow restriction. Their solution is a "lump port" kit. These are a lump of cast iron that fits the port floor on the short side turn. This gives a larger radius to the turn. Then the roof can be ported to increase the area.
A hole is drilled through from the rocker area that does not have coolant and through the deck surface. An Allen head bolt secures the lump in place. The hole is taped with a pipe tap from the rocker side to seal the rocker area from the port.
I think most V8 heads have coolant above and below the ports, so this would not work.

[driverjamescopeland]

This was the entire principle behind GM's "Fast Burn" SBC ports... and they were considerably effective. It allowed you to get big cam revs without excessive duration. The revised exhaust ports alone were worth 10-15hp, and gave an easy 100rpm to the sweep of most street performance cams.

[SuperRockinRobert]

Wow, that was interesting. I had a 03 Yamaha FZ1 and had installed an Ivan's Jet Kit. Well after some playing around the bike ran well but still had a lot of pops on deceleration. In an effort to reduce this I made a cone (never heard of this before) from some steel pipe to increase back pressure and get rid of the decel pops. I installed it where the four pipes meet as one. After some playing around I had a smooth and fast running machine. More importantly, during taking it apart, adjusting (bending) and putting it back together multiple times, I had accidentally broken one of he four "leafs" of the cone. The broken, or non restricted, area ended up at the bottom of the pipe. I noticed the difference immediately. Only thing is, I had no idea what I had done. Now I know. Thanks David.

[randywl]

The location of the plate is very well explained and makes perfect sense.

[bobpaff]

David. In the late 80's I experimented with anti-reversion with some astounding results on my SB chev. My dad's 8hp Briggs & Stratton garden tiller and a friend's SB mud racer also went nuts. Life changes stopped me from continuing. I am so happy to finally see you took this seriously, whereas everyone else has leaned on high-tech for simple solutions. I would love to talk some more.

[Ron_Presley]

David Vizard has as much knowledge I bet as anyone out there that builds engines like he has in his lifetime. Amazing man. Love for him to build me SBC for my pro 2300 lb pro street car. Thank you David for your hard work and time sharing this stuff with us.😊

[sjcottsi]

Off the subject but you are the perfect guy to tell Steve Morris the cam specs for his Big Black Hemi, 903 cubic inches. He has a video on it.