Big return hi-tech quench that pro-stockers don't want you to know. 

David, since the mid eighties I have been experimenting with quench. I am a Volvo VISTA tech and have built race engines for Volvo Subaru Suzuki Audi ect. My interest in quench started in the late seventies when Volvo had a severe problem with detonation on the old pushrod B20E engines. The factory fix was a 0.020" thicker head gasket. This was a dismal failure. I found that a thinner gasket actually improved the situation. As we were doing several gasket changes a day i started to experiment with improvements. Swirl was the new thing at the time so I started to cut a shallow 8 mm trench in the quench pad on the head to promote swirl. I thought that concentrating the flow towards the plug would improve detonation control. And it did. I gradually realized that it was actually cooling the exhaust valve area. As time has gone on I have refined the situation on my Honda races engines to the point that no one can touch the output of my engines and they can't figure out why. I've been called an old school mechanic but all of my race cars hold records at our local race track. That includes a 1972 Volvo 142 that has never been bested.

43 minutes was too short, David! Never worry about length if you're filling it with this level of tech!

I attended Automotive High school in Brooklyn, New York from 1982 to 1986. My fellow students and I were taught about quench in engine shop class several times and it amazes me that over the years later I've read many publications about engines and engine building but only your publications and videos have gone into great detail about quench! You are truly a master!!

This might be one of the most valuable tech talks yet.

I would agree that Darrin's page is under very underated and subscribed. I have listened to Darrin in his interviews with DragBoss and the detail he goes into about ports and chamber science is outstanding. I especially loved the stories about him working with my hero Bob Glidden. But I have just discovered Davids videos recently and it is a whole new level of knowledge for me. Thank you David for spending time to allow us into the science of engines and your mind !

DV fine details removes our misakes . WE WANT MORE !!

Only Masters talk about quench. Well done. 👍

While in high school I took Automotives 12, 22 ,32. The one instructor was an old navy veteran who at home was working on H2 fuel engines. This was 1968 to 1971. The other instructor had a friend that raced a stock car in a class that required a 6 cylinder engine. I mostly was involved under his tutelage, to bore and build the engine, a 261 from a truck. He had the head milled 0.090" and the block 0.060" to raise compression. Milling the head that much took all the combustion chamber out of the head on the intake side. The exhaust is recessed deeply with the spark plug. The throat in the port bowl was cut out using a seat cutter. Larger intake valves were installed with the seats recessed so the intake head was just below the head surface. This provided pretty good quench. The racer provided a new cam that appeared to have a fair bit of lift and definitely duration. The only car faster in the first race was basically identical except it had headers. Unfortunately the engine blew in the second heat. Learned a bunch on that project.

I too have a channel that does some cool engineering stuff and my subscribers are less than 1000 subs , it seems that great engineering isn't high on the RU-vid algorithm, DV I love watching your videos and it shows me where I've been right and shows me areas to work on 🤗 thankyou

Your scavenge plato is a stroke of genius.

Thankyou mr vizard allways leaves one wanting more.peace

Another great vid DV The deeper the dive the more interesting for me.

Crevice volume is also a massive contributor to hydrocarbon emissions (more so on port injection IMO). Many manufacturers have moved up the ring pack to reduce crevice volume, only to find that the decreased ring land strength leads to more failures (Subaru EJ25, cough). The use of abradable coatings could not only help power, but also help OEMs meet tighter emissions specs.

We've experienced exhaust valve pre-ignition on our early nitrous motors at a certain nitrous level, no tuning would eliminate it, just improving the exhaust flow with port work and valve size.

Nice grinder work DV You still have a steady hand a groove to the wrist.

Ben Alameda spoke of this crevice gap in one of his videos but he warned going too small especially in a boosted application can actually crack a piston easily. This is great stuff.

Knowing this information 30 year's ago would have helped 😂, interesting information, thanks for sharing, all the best to you and your loved ones

Darrin Morgan, is fantastic and great at explaining.

Another generous lesson. Thanks Dr. Vizard!

,,,,,,,,thanks David ,,,,,,,,,,,,,,,,,,,,,after the prior weeks of doubters ; you are working stronger than ever ; putting out high tech topics ,,,,,,,,,,,,,,,,we all need to know.............

This is very great info DV. Thank you for all the videos.

Thank you for sharing this! I can't get enough!

This is a great video on the charge. Do to the work and shaping of the chamber. Thanks again.

I found that the head gasket had to match the bore exactly,the thinnest possible. This helped detonation problems

Thank you, David. This information is much appreciated!

Thanks David! Wonderful video... In a restricted class with flat top pistons, no touch spec heads and 10.5 to 1 compression rule with a 355 SBC, 1) are these combustion chamber mods with more than the marginal loss of compression they would create. 2) with a no touch spec head rule, could we do the exhaust"soft chamber" modification to the piston valve pocket area instead to gain the same effect? 3) typically how much coating do you add above the top ring piston wall to make a difference there.... Thanks you for all you do with all you videos to educate all us privateer engine builders ass well as a lot of pro's. We all appreciate you and what you do to help us!

awesome stuff again DV, these are the details that separate building a race engine and building a great race engine. Keep up the good work!

Darren’s videos are amazing. Still learning from them each time I re listen.

Thanks for doing this talk David..Iam working on a sidevalve harley which has lots of quench . It gets me thinking and that's a good thing as people with these motor are stuck back in the 40ty and 50tys with there thinking and there has been no change, and I think there is room for change and that is what I am working towards. Thanks again David keep up the good work it does help.

You've been on a roll. Great stuff. Can't wait for more. Much thanks.

LOVED every single detail in this comprehensive video, and no it wasn't too long 😅 this info is 'gold' to me, and I am not even an engine builder, i am a sheetmetal worker. Anything to do with flow i want to know, cheers David. Only just started watching your videos and will be watching all of them. Good job and thanks 😀😀 and sorry for your loss.

Another excellent episode. Thanks DV

Been subbed to Darrin for a while now. Super informative.

Darin Morgan is the traditional Pontiac king he has a customer making north of 1300 Horsepower N/A!

DAVID Thanks man and as always God Bless you

Thank you Mr D.V.

Another great one, can't wait to see the one covering combustion chamber and piston crown shapes. Back in the dark days, playing with small block Chevys, I was always amazed at how much better the approx 1970 and older cylinder heads ran on otherwise the same basic combination. No better flow, just a better combustion cavity / quench situation.

Wow. I had no idea David Vizard was on here. Wish I would've known this guy 25 years ago when I was digging deep into building high horse power engines. I had so many questions I needed to know about volumetric efficiency and I heard you were the man to see. Dude, youre a legend, up there with the best of them like Shelby and other true original greats. I just cannot believe that youre on here and somehow got suggested to me. Well, cheers to you, sir!

That was outstanding, keep it coming!!!

Beautifully done thank you david

DV, a thought, do you have merch? I was thinking you, Andy, Brian, and Darin could benefit a bit financially by offering ball caps, t shirts, sweat shirts, and coffee cups, with your Powertec 10 logo on them. Put web addresses on the back.

Thanks you for sharing knowledge 👍👍

Great video. Thank you.

Thank you again DV

Love your segments im a cummins turbo diesel fan i just started working with the old 12valve 5.9s and ive built a whole lot of different big blocks and small blocks . my first big block was an oldsmobile cause i was a joe mondello student

Your advice about crevice volume is interesting to me as a Subaru owner. Subaru's are well known to have a weak top Ring Land and it was apparently due to the Subaru Engineers attempting to reduce HC emissions by reducing the crevice volume. By contrast, the Top Ring Land in the Mitsubishi 4G63 piston is about twice the depth of the one in the Subaru EJ Engine.

Really great info. Thanks, and 45 minutes wasn't too long at all. Even with my ADHDD!

I have built @355sbc with 12.5:1 cr. Using 492 heads milled to 18 degrees, resulting in 51.5cc combustion chambers with .016 head,I'm using the Summit 1204 hydraulic flat tappit cam with 1.6 rollers

I just built a propane fueled SBC engine in 2023 . It is a 12.1 CR with a set of Vortec heads with as tight a quench area as possible . With propane not needing to be vaporized , vortec head swirl mixing and tight quench I'm expecting good performance . It is unfortunate that I could not get sodium cooled exhaust valves for this build . Good thing propane has good detonation resistance but some better valves would have been nice . Your episode has verified that I am the right track . Thank You Sir !

you should talk a bit about gas porting pistons as well ! i purchased a 1967 Dick Landy 426/383 that his brother mike built in 1968 from what i read in several articles gas porting pistons was not around till the 70s but here it was in front of me a gas ported piston in a super stock motor from the 60s. I always buy 4 sets of pistons and after boring a motor i fit the tightest piston to each bore. then gas port my pistons i was taught to use one extra gas port hole to the outside of the motor .

It's big it's been around specialty,,, one of the can type junkers,,, you got to look at that throat,,, working on quench,,,,thank you for all the videos,,,

Fascinating.

It was very interesting and explained very well. Keep them coming. When are You and Eric putting the gloves on again? Only kidding; don't waste your time. Your brain is like a mega computer!!! God Bless!!! Mike

RU-vid dumped a ridiculous number of ads into this video. Good luck with your channel. I only run NA. Torque and efficiency for the sum of the parts. Started out with air cooled 2 strokes 40+ years ago, melted pistons were always from insufficient squish clearance and lean mixture at full throttle. Before the days of rev limiters, mapping and unleaded. Often see porting being done with the intention of directing the mixture towards the spark plug so not sure where it all went wrong. Buddy, that valve has been closed for best part of a stroke before the spark. Swirl with maximum micro turbulence will get the best economy. Too rich will reduce the header temperature but it's better than aluminium paste in the crankcase. Happy days.

Hi David, thank you so much for the information you’re giving us wish. I knew this a long time ago the video that you did on the quench I’m interested to know just you don’t have to make a big deal out of it. Just answer the question if you could did Pont Pontiac have a better grasp on the combustion chamber shape because it was milled verses cast chambers and if so, why don’t any of the new aluminum head guys machine, the valve pockets and combustion chamber like Pontiac did and using the 30° angles on the seat just something fellow engine builders were talking about the other day in the shop. We tend to meet once twice a week and discuss these horsepower gains that have been lost overtime or maybe just not shared with the public. We very much enjoy your show and look forward to more videos on educating us on the foundation stones that we all need to have to build the best engine possible and then look for more. It’s a way of life at least for me and my buddies. Thank you for your time and I hope that your throat surgery ends up healing faster than it’s been going, thank you from the gang at the machine shop/Dyno/oh and we have one of the older super flows benches. Thanks Dave again best wishes, Joe.

you would spend several days formulating quench positive delta negative delta . most do not realize it but nitromethane will not light on its own very easy much like diesel and once it is quenched inside a top fuel motor the quench is so tight the nitromethane is actually converted from a liquid to a solid fuel ! the nitromethane is about the same rockwell hardness as a piece of charcoal

Wow Great video always good inf

Good video…thanks

Thanks, would really like to see the BMC A head mods. Always guessed that the inertia of the fuel causes the drop out when compressed and that is what piles up carbon in the crevice.

Thank you.

thank you sir , you are my hero .

U find most 2 strokes have a tapered quench to direct the fuel charge to the plug in the center of the chamber and altering chamber shape can effect the power curve quite a lot.. some things are self explanatory when looking for every last ounce of power.. the average joe has no idear how all this relates to making any engine reach maximum potential.. then you find the simple things added up make the best improvements..👍

I can see that direct injection is a massive improvement in regards to crevice volume being full of fuel. I can see that by injecting directly into the combustion chamber there is much less chance of fuel ending up on the cylinder wall. That must be fantastic for BSFC

Thank you

Thanks!

Congrats on the 60 thou , and here's to many more ,,, !,,, Cal DeBruin with Speed Pro division of Sealed Power ,,, .

During my engineering studies, I recall the study material from Chrysler about combustion duration. Eleven to seventeen maximum degrees of rotation drop on the various engine bores, strokes was that determination. These were flat or decompressed pistons. The workup was one of comparatives of decks, timing and temperatures etc. The fuels used were taken into account for control etc. The studies are now old, however showed production capabilites without the fine tuning good engine builders would provide. The surprising part of the study was the time verses completed combustion. -- Your video was a good partner to that. Thank you David.

On a slightly different subject but related, I would love to see the science of why a good 4bbl single plane makes just about the same power as a Ir setup efi or carb. There clearly is lots to the reversion/pulsing into the plenum going on that it takes advantage of. Could you get the same power with a pair of side draft carbs and a clever design inlet? ( hood clearance stuff) Would you place the carbs fore aft or sideways?

There are a few engine master engine builders on utube that use that piston coating. Most master head porters soften the quench.

concerning the detonation discussion, it sounds to me like Vizard is talking about Larry Widmer's Soft Head concepts.

exhaust is always the hottest that is why in a race motor your exhaust valve has .015-.020 lash cause when it heats up it expands and tightens up i usually set intake close to zero lash. cryogenic treated valves are also a lot stronger then treat them with coating. im building a twin turbo 440 /526 mopar entirely cryogenic treated all major internal parts coated im hoping to crack a reasonably reliable 2000hp

🔔😎 Ive never heard the following discussed but it's something that I've always seen as a strong possibility: Singh grooves increase turbulence but if you look carefully the outer smallest end is past the piston edge (.050 from fire ring) and causes a squirt into the piston edge gap/ crevice volume which forces that crevice mixture to tumble out. That seems to me as a good thing.

every 2 stroke since the 80s has been using angled and tapered squish.

The pontiac combustion chamber has that two step chamer.

I like it!

Honestly it is frightening to see how DV open up an already huge combustion chamber! Especially knowing that he increases the chamber volume and decreasing the quench area. I'm not sure if I will do that with heads already out of production and hard or expensive to come by. May radius the edges a bit with sandpaper but scary to do it the hefty way. Double port Panda 30 and FIAT 126 single port heads are a rarity these days. Let alone the 4 cil. 100GL heads.

So that is why the Chevy 409 was such monster-- squish, big unshrouded valves, squish opposite side of the exhaust valve, and 17 degrees less turn for the intake port

Crevice volume reduction between the piston crown and cylinder wall was touched on. Although I would like to know the minimum clearance to ensure once the piston is at operational temperature, clearance is still achieved without danger of scoring the piston and bore. Obviously this clearance would varie with forced induction and or nitrous.

Hello David I would like to purchase the IOP The pay button does not work I am building a 383ci I have a goal of 1.42 lb-ft per 1 ci or better. I have been following you for many many years. Now is the time to put together all of the knowledge.

I have been following you for over a decade. Despite what everyone has told me I'm building a 350 sbc with your advice in mind. It's ment to just be a cruiser with 9:1 compression, 60cc trickflow 175 dhc heads, isky adv 258/258 .050 208/208 with .464 lift and a 107 lsa. I will have it on the dyno next week and hope it's a low rpm torque monster.

I was taught by my turbo friends , i.e.Peter of Andersson Turbo systems, a ten C. lower in gas temp , result ins 100 C lower exhaust temp.... hence INTERCOOL !! (Building 600 hp , 1300cc Hayabusas ..)

I have built @355sbc with 12.5:1 cr. Using 492 heads milled to 18 degrees, resulting in 51.5cc combustion chambers with .016 head gaskets

How do I like this twice?

DV, These videos on quench are becoming my favorite in your library. I'm curious, if one was looking to maximize an SBC in the 9.8:1 range, is it worth the slight loss of compression to include a scavenge plateau to increase flow. I know you were an advocate of "squeezing the hell out" of what you can get in the chamber. My bottom end is set but I can still work on my heads. I like the sound of being able to rev a little higher for a given cam. In general, how does adding a scavenge plateau effect the low end for that cam? Is it like stepping up to the next one in the catalog or just extend the top end? How does this smoother transition not increase possibility of reversion? Thank you for sharing this great information.

I performed all this work and polished the chamber however I ended having to mill 1mm off the head to reduce comb chamber volume to regain comp ratio 10:1

David, you need to re-investigate (for your own satisfaction) the inverted dome in the center of the piston, this where you will reduce the engines dendancy to detonate, not at the exhaust valve. What you will find is the exhaust valve will run cooler and you can run higher compression ratios with leaner fuel mixtures. The leaner mixtures will give you more power and lower B.S.F.C than raising valve lift, Once you start to cut valve reliefs into the piston crown, your power output per pound of fuel will decrease. (But if you are cutting valve reliefs in the very center of the piston crown, that is okay.) It is the piston center that becomes the hot spot, that is why a detonating engine generally melts a hole in the centre of the piston.

Guys just don’t want to go through the hassle of decking a block. (The Expense) Nevertheless that’s going to increase the power and efficiency. I’m going to build a snazzy 4.6 2V .005 out of the deck DV Squared .000 - .005 out I’ll make sure I don’t over exceed the limits

I was wondering David if you have done much work on Fords Cleveland heads, here in Australia 2v+4v heads are still extremely popular. The Ford Australia heads from standard were much better than their American counterparts , i think if you have time to do a video on them it would be greatly appreciated by all. Cheers Australia.

I’m curious why there’s no reference to the Joule effect ( cooling effect on a gas that is ejected at high speed from a nozzle aka a compressed gas being ejected from the squish volume into the initial combustion chamber volume? BTW also curious why the piston surface topography ( shape of the crown) isn’t modified to match that of the curve that replaces the previous step, so as to permit the “scavenging” gases during overlap, from cooling the backside of the exhaust valve, so cooling it more effectively? BTW, many thanks from someone who read your articles in Triple C, when I bought them as remainders from Chris Montague Carburettors in Childs Hill, London.

Awesome show couple questions first would milling the head increase quench area second if you mill the top of the piston the same thickness that you milled the head and deck the block same thickness would that increase quench area even more and is there anything to Gand with that mod third if you thermal barrier the top of the piston would that increase flame front burn speed forth is there a friction reducing coating or micro polishing that would let the compression ring expand faster question five if you use oil shedding coating on the bottom oil scraper rings would this increase the oil scraping flow reducing resistance? Thanks again your awesome

The question for me is how far can you go with a ceramic coating at the top of the piston to cut down on the crevice volume and still utilize a gas ported ring like total seals? As in how much can you limit the growth of the piston with the thermal barriers at the top? The Line2 Line abradable coating looks awesome for the skirts of the piston.

Would be nice to see where water injection possibilities lie as well for an optimized tuning window 17:1+ Cr? Thank you!!!

Usually detonation starts at intake side.

Seems like they could get the piston tolerance to cylinder tighter above top ring and so not needing the extra thick coating.

Thanks David and Andy! Good stuff. I know in the last video you said .018 quench was the absolute minimum on a sbc,would this hold true on others such as Bbc as well?

I have built a cosworth yb turbo engine, running,_7.9:1 CV compresión with minimum quench clearance and its more responsive and fuel efficient than with std quench, running 1.9 bar boost no problem with detonation.Big respect to D V👏👏👏👍

Big D what’s your take on the piston rings that have the spaced out machined slots that force the exploded fuel mixture into the gap at the back of the rings so it forces the ring to push tight into the cylinder wall ??????? Suppose more compression and torque. Will this wear out the walls prematurely either street or strip ???????????

Hi David. This might be one of your best video presentations ever. Thank you. My question is and I have only watched the first ten minutes so far. When you say the exhaust valve can get hot enough to cause detonation. How would that be determined to be a detonation wave verses a pre ignition event with flame flagration but at a less than desirable moment in crankshaft time. Or will detonation actually be achieved if the exhaust valve lighting the mixture is near the time of the spark plug firing event causing two coliding flame fronts? I always was of the thought experiment that with the combination of high static compression as well as a tight enough quench zone and poor water cooling through the head in certain areas. That the quench area could also get hot enough to start a flame front that could depending on when it initiated also might become a detonation wave? Am I on the right track. Or is there anything you can elaborate on to help me. I feel this topic is the most important area of race engine development that is not given enough attention and would love you to expand on this even if just thoughts and ideas over confirmed science. Please respond Sir. Thank you for your contribution and I follow Mr Darin Morgan religiously. Thank you.

Would someone be so kind as to post a URL and/or URI to some of Darrin's work please? I found some content from a decade ago, but I do not know Darrin's face. This is not my field but I've re-built a few engines. I never built any higher horsepower engines but my original training was in industrial machine shop, I understand the things this great man speaks of. I've recently jumped, head first, into automotive power distribution and a bit on CANbus. Mr. Vizard, thank you for furthering my education and expanding my terminology in performance engines. Your cam research is gold!

Darin did my trickflow 11r heads , that everyone said cant be improved , and we are 3th quicker , in bad air , wait for fall air , i'm guessing 5-6 th quicker with no other changes