Tech Talk: RB26 Combustion Chambers!

Dave doing a one on one with his thoughts on chamber reshaping on RB26!

[@BrianCrofoot]

So glad I got my RB26 head done by you guys and I can’t wait to get the car running! Engine is starting to go together this week! First hand experience is what you pay for. Can’t wait to find out how the combo works!

[@ericsmcmahan]

David Localio, ur a smart guy and I learn a lot from you.

[@headgames]

So happy to hear! Thank you! Love from afar!

[@finnroen2334]

A wise man once told me; When most people see a man in a shop buying a drillbit they think he needs a drillbit. The truth is that he needs at least one hole. Likewise when someone buyes a performance camshaft or performance head, they do not need a camshaft or a head, they need more horsepower, torque and performance and therefore only products that work as intended. :)

[@headgames]

Very wise!

[@ICTPerformance268]

🇦🇬 In my humble opinion, your reasoning is 100% spot on. Manufacturers invest millions upon billions of dollars on R&D. They have the ability, experience, expertise and equipment to know what works and what doesn’t. There’s a reason why they put those quench pads there. Some careful deburing, deshrouding, balancing and polishing of the chambers go a long way to prevent detonation problems. Enhance, don’t undermine. 🙇🏾‍♂️

[@headgames]

yes!

[@dorifthor]

Dave I love and respect your porting awesome job but here’s my take. My theory is based on the idea that the large quench pads are for combustion efficiency and emissions. The idea of a quench pad much like direct injection is to get a pocket of richer fuel air mixture concentrated near the spark. It works great in many applications but the modern take on combustion chamber design for horsepower is to make the engine as detonation proof as possible. Removing the quench pad and replacing it with a spherical chamber is following this theory. The better an engine can resist detonation the more power you can make.

[@headgames]

Hey I still love you even if we disagree on something. Thanks for the kind words and taking the time to throw your ideas out here!

[@jimlathrop8603]

Another great video. I do think most people fixate on thinking more timing is the answer, but as you state, it's the flame speed that dictates timing. Also some seem to think the quench pads are for emissions. It's there to create mixture motion during combustion. Something 4v heads lack compared to the swirl you an get from a 2v head. A question I have here is, would easing the sharp edge of the pad help? Seems to me that sharp edge probably holds a lot of heat.

[@GroovesAndLands]

@dorifthor Here is why I disagree with your theory: There were two "godfathers of detonation" - guys that recognized that compression makes power, but causes knock; which breaks engines. Therefore the knock must be eliminated. Charles Kettering went about solving it by inventing a way to increase octane - Tetraethyl Lead. Harry Ricardo sought to eliminate it by the shape/geometry of the engine parts. He is the one that discovered that high mixture motion and turbulence decreased knock tendency. He is the one that invented the concept of the high-squish combustion chamber shape, as well as myriad other designs to greatly increase the motion and turbulence of the air/fuel mixture just before ignition. When I worked for GM Racing, I spent quite a bit of time with the combustion engineers. Those quench pads are there to introduce a lot of mixture turbulence at TDC. They are HIGHLY engineered to accomplish it.

[@T51B1]

The biggest difference people will notice taking the pads out is the change in static compression with the usual off the shelf aftermarket pistons. A person could have pistons made to raise the compression back up but then the question becomes why bother other than to avoid any det concern with the pad there. The amount of flow you could possibly increase by taking the pads out is offset by the lack of combustion efficiency with them removed. Besides, the big problem with getting the rb26 head to flow well is the exhaust side. The short side radius is so sharp it's hard to get it to flow well.

[@headgames]

Yes! Glad to see you here sir!

[@mikerieck306]

I whole heartedly agree with your assessment. Also...you shouldn't have to run a lot of timing if the ports and chamber are working efficiently.....you should actually be able to pull timing but maintain performance. I do bike stuff and if you look at modern Japanese or Ducati heads the valve angle is very shallow which allows for minimal chamber CC's. It also allows for dished pistons or at least flat tops The dished pistons are great as they promote great squish and really concentrate charge in the center of the chamber/piston. The only thing that kinda sucks about Japanese bike porting is the small ports compared to cars. The Hayabusa has nice large ports but 600cc bikes do not. 😁

[@paulbuckham109]

You are completely right, I tried this on a sr20det back in 2004 the made good power and if it wasn't for a motec computer at the time they had double the load points of any management on the market you would not have been able to tune this pig I am talking 35 degrees 17lbs of positive pressure 7000 rpm all it achieved was completely kill flame propagation in the transition phase from kernel to complete equal flame front good news no more back sided pistons .keep up the great work and videos

[@headgames]

Great example! They have a very similar chamber design. Thanks for the kind words!

[@danielllewellyn5720]

I like your ideas sir.

[@headgames]

thank you sir!

[@MrJermbob]

What about when your mate sends a split washer through the engine and it ends up munching that area on the head ? Hahaha. Im planning to weld it back up and get it skimmed. The neighbor that was supposed to be a expert RB tuner said just grind it all down. Im glad i saw this.

[@tuercaracing]

Congratulations for showing your work, which by the way is very good, and for sharing your experience. I completely agree, what I do is simply remove the hot spots or sharp edges but nothing more. Greetings from Spain, I hope you can enable the Spanish subtitles option haha 😅

[@headgames]

We can work on that!

[@headgames]

Thanks for the kind words!

[@The_Performance_Laboratory]

I would assume those removing the quench pads on only one side are doing it on the exhaust side, since that hotter edge will be more detonation prone. I'm also a big fan of fast burn chambers and think "soft" chambers are for people who don't understand combustion dynamics.

[@ashleighcurtis]

Thanks for the Vid im just about to do a nice port/polish on a new RB 26 head

[@headgames]

good luck!

[@Grooty79]

Squish is necessary, tight squish helps to make an engine less detonation prone, softening the edge is good but only time i mod the squish pad is to deshroud valves, if your squish pad is covered in carbon then your not tight enough ☺️☺️☺️

[@GroovesAndLands]

Engines always run strongest when the piston hits the head a little...

[@thedeadman3848]

Totally agree about not removing the pads. I actually wish l could make my quench pads larger. What are your thoughts on welding in larger ones (aluminum). I’m personally scared to try, I’m afraid of metal breaking loose.

[@headgames]

Welding it right won’t break loose

[@niall21]

I was actually wondering about whether I should soften that hard edge on my rb20 head. I guess I won't! Thanks for sharing all this good info, it's so cool to see someone so confident in themself as a product that they'll share all these things other people would consider *trade secrets*. One thing I am curious about is your opinion on using a Dremel instead of a more appropriate tool to do some mild port work.

[@niall21]

Actually I saw you mention cleaning up the sharp edge on a comment😅 I guess I will lol

[@headgames]

Yes do it! Just soften it like in the vid. Don’t remove it. Thanks for commenting and watching! I would never suggest using a dremel vs getting a real grinder. 1/4 shank grinders are plentiful and cheap. And then it opens you up for proper tooling that makes your work come out better.

[@0x33_Uk]

Some of the older JDM builds might opt for the quench removal back in the day due to fuel selection. Although hi-octane gasoline was available, its not like today where you can chuck in E85 as easy as now and get spicy with more efficient combustion designs. A lot of older RB's builds I've tuned, I can sometimes note that although power is decent after enough boost, the engines dont feel very efficient relative to how much boost and timing you have to wind through them. I'm not an RB expert by any means, but just what I've noted on some JDM stuff I've seen. Definately seen a head thats had the quench removed on an old JUN engine, didnt matter if you were running 10psi or 35psi of boost, it would take 30 degrees timing lol, any more or less and you lose power and no knock to be found. Made me laugh.

[@headgames]

you seen what I am talking about first hand! It's crazy that people still do it in my opinion.

[@0x33_Uk]

@@headgames I feel like removing it completely is too extreme, but maybe massaging the quench pad a bit I could understand. I'd rather have more efficiency so you dont have to run everthing quite as hard to get to whatever power level in an ideal world.

[@Marko-JZX100]

What was the static compression ratio and cam choice for that particular build? I'm more familiar with jz's and found out that usually after 10psi of boost up to 30psi ish peak power timing is about 14-17deg depending at what rpm it occurs. Peak torque timing with the above boost levels is somewhere around 10-13deg on vvti engines that are not limited by dynamic compression. I've seen high static compression stroker with 76mm turbo, and way too small cams barely having any advance BTDC. Was cured with proper cams and engine was more efficient in every rpm range.

[@0x33_Uk]

@@Marko-JZX100 Im not entirely sure on the specs, all I was told was that it was a full JUN engine built by JUN, sounded like it had 280's in it. Big old T88 on it. Proper old school setup. Most RB's follow a similar principle to 2J in terms of timing, but this engine was different than most. Could of been a few things contributing towards it, but wouldnt suprise me if they did some headwork like Dave has pointed out. I've had other RB's with similar specs in terms of cams/strokers etc, but you would never get away with 30 degrees timing at 35psi on them, you'd detonate way before then. I tune JZ's primarily, but disagree with you slightly. The timing numbers at 10psi vs 30psi are completely different at both peak torque and high rpm.

[@12Senna]

"semi hemi" head dose the same thing in promod and mountain prostock, the quench pad were still remind

[@headgames]

they soften the chamber but they don't remove the quench pad. Is that what you are saying?

[@12Senna]

@@headgames can be benefit both way, edge soften aiming for heat spot prevent （also work as exhaust transition to help port energy for wedge chamber according david vizard [since the cuench out gas were almost hyper supersonic at the exhaust stroke TDC and facing right at the exit port]

[@mtperformanceengines3508]

That's a very interesting conclusion as I ported and made the heads at maatouks racing for years and Croydon's gtr also have hemi chambers they are the fastest rb motors on the planet so maybe at the upper range of 2000+ hp it's needed

[@headgames]

that's why I said, I know people have done it and maybe even did it with success. If I worked there I would either be eating my words or right lol

[@masonsmith2486]

I have done the same to my Honda Gsr head. But I have opened the whole chamber up for my larger 84mm bore. But the quench is still there just softened. But this is why I like Gsr better quench and better attach angle on the valve vs the b16 heads. Should I have left the sides alone or opened them up to Match the bore the head has been machined down so to get about the same cc chamber.

[@headgames]

Your good opening up the chamber size to the bore and laying the chamber back on the quench pad. The b16 head still works great, has a quench pad but its just different than the b18.

[@flattratemaniff7554]

People I've chatted with always mention they are in the way, (flow wise) my personal head on my RB26 has them laid back as you suggest, head was CNC ported by Endyn Energy dynamics way back when, which is no longer in buisness. I see Australians take them out at times as well.. would be interesting to compare the 2 heads on the same engine.

[@headgames]

Larry is a smart guy! That would be a great experiment

[@bennyz1971]

Like this type of video, there are many thinkgs you could discuss, to be honest I want that but also more details 👍🏻

[@headgames]

you like me just blabbing in front of the camera?! lol What other details are you talking about?

[@bennyz1971]

@@headgames yes, its about the content you deliver, the knowlege, do you know David Vizard? He recommended headgames in one of his videos. He is tuning a lot of older Chevy V8s About the details, on quench area, how to see if there is the tendency for knockin and how to change it. On cylinder heads, there is a lot more to talk about 😉

[@headgames]

Yeah I know who Vizard is, he mentioned HeadGames!? that is awesome! Maybe you know which vid? @@bennyz1971

[@bennyz1971]

@@headgames Im afraid I dont know exactly the video, it was about one year or longer ago, but that was how I found this channel 😉 If I find the video, I will let you know

[@simonsays8704]

Merry New Year

[@headgames]

Same to you!

[@CJ5EVOLUTION]

You take a dye grinder and go thru the edges to take the sharpness out of them then go with a sandpaper to get the final touch or leave them as is?

[@headgames]

Or cnc it. Not sand paper, we use cartridge rolls.

[@joeyniemannchristie2678]

It makes sense because if you take tham out it means it needs to fill in more space if you keep it it’s direct and it doesn’t have to fill in extra space.

[@bobirving6052]

How are your results with just removing the sharp corner on the quench pads? I’ve been doing what I Learned from Ben Alameda racing. It is not a “softened” chamber, but it is grooves on the pad which jet the mixture towards the plug.

[@headgames]

grooves are not fixing the problem.

[@bobirving6052]

Yes! You are paying for somebody’s theory 🎉

[@GTRliffe]

the RB26 can rev to 9k with medium cams and springs that's a huge powerband, therefore removing the quench makes it more suitable in that higher rpm?

[@headgames]

The chamber is related to ignition timing, not rpm. The quench doesn't care how much RPM you run.

[@johnbill7968]

Possibly some property done coating on the head and pistons aswell would help the situation?

[@headgames]

Coating doesn’t do anything from what I’ve seen.

[@franccoch4676]

Hi would you have a good advice to port and polish and may be design combustion chambers on vw flat 4 heads?

[@headgames]

man I have no clue on that deal. Don't listen to me, find a VW guy on here!

[@skylinefever]

I do not get why people remove quench pads. Look at the guys who build OHV V8 engines with wedge heads. They seek to maximize quench. They seek out the head casting numbers with the best quench zones. They carefully mill the block deck for ideal squish. I hear a lot of guys saying less quench for boost. Maybe that is why these guys are removing quench from RB26DETT heads? Most of those OHV V8 engines were NA, and are kept NA. The guys building boosted V8 engines sometimes say less quench for boost.

[@headgames]

the V8 guys will soften the chamber, which is essentially what we do by laying the chamber back but they do not completely remove the quench pad. Boosted or otherwise.

[@skylinefever]

@@headgames Thanks. I think about how the guys with a Chevy 350 would often seek out 906 or 062 head castings because that combustion chamber was the best that any iron Chevy 350 head ever had. They might cut a little quench out for deshrouding purposes, but that's about all.

[@michaelgunning347]

They were done for the gt500 , supposedly A restricted engine class changes things alot

[@headgames]

GT500 as in the predator? I think it's more like a cover leaf chamber in those.

[@briantenpow9469]

100% correct!👍

[@headgames]

🤛

[@RocketRaspeed]

I have noticed on my aftermarket 2jz pistons the quench area is about half the width of the oem piston. In this instance is the extra width of the quench pad in the combustion chamber doing anything?

[@davea3881]

I'm getting custom pistons made for mine...na head..and max squish, aiming for no more than 25 thou clearance. Will report back. 🤌

[@headgames]

that's tighter than a gnats ass wrapped around a wagon wheel. Report back!@@davea3881

[@headgames]

it is following the chamber on the GTE head

[@user-yd7sp8dg2t]

Can you do a video for bigger valves and how do I find the ones that suit me?

[@headgames]

how much power?

[@lenwaite5944]

Does the sharp edge on qwench pad cause hot spots ?

[@headgames]

yes sir! That is why we lay it back so it is a gradual edge

[@alexhise968]

I disagree a little. I made a cutter to put a measured cut removing the pads making radial conical pads that were way easier to blend in. Our CR was 11:1 we ran fairly wide cams so the dynamic was 10.3 that engine made great power and responsive to.

[@alexhise968]

Definitely had custom pistons made tho.

[@headgames]

I know there are people who have done it successfully. I get it, because it will work. Just don't think it works as well as the way we do it.

[@GTRliffe]

6 minutes on that alone? 35+psi it doesn’t need to be there, because we’re doing everything to too help high boost (custom piston a must) leave it there for more VE if your chasing low down torque We rev these to 10k rpm so anything that might hinder that should be removed

[@zactrimble4343]

can make 600hp on an unopened engine reliably and 1000hp on a stock bottom end and an un ported head without detonation. If you have your quench set up correctly it is near imposable for it to have conventional detonation your issues lie else ware friend and i would be looking at pistons around the quench area probley find there is no quench and hence detonation

[@headgames]

we run 100psi+400 shot of nitrous on 2jz and don't remove a quench pad. VR38 does 80psi with quench pads in it. I know it doesn't work. But, you do you boo.

[@bobirving6052]

@headgames I think maybe he is saying that the detonation on the quench pads was caused by pistons, not the pads. If the piston does not come close enough to the pad, it can detonate in that narrow chamber. (The way I understand it.)