Tests like this are what sets this channel a part from the others. Pitting two top shelf (for most guys) heads against each other and letting the cards fall where they may. No sponsors getting in the way, just an honest flow of information from Richard to the world. Thank you.
@cuzz63 Жыл бұрын
fact....I find it funny that if Richard makes a video that doesnt agree with someones claims they will claim he isnt independent.
@richardholdener1727 Жыл бұрын
I wonder how sponsors actually get in the way of a dyno test? The results are the results.
@LucasMullins-j4y Жыл бұрын
@@richardholdener1727I think he means that we the people appreciate that you don't push or favor a specific product unless it's just a better product.
@ryandoyle4344 Жыл бұрын
@@richardholdener1727seems sponsors like positive results
@cuzz63 Жыл бұрын
@@richardholdener1727 you mean you dont put your thumb on the scale?
@johnprince7510 Жыл бұрын
The AFR has different valve spacing. The intake valve is moved about .090 (I think) inwards over the stock LS3 design.
@gavwilldo Жыл бұрын
Both the tfs and afr use a 12 degree valve angle over stock ls3 15 degree, both have identical valve spacing to each other.
@highwaymen1237 Жыл бұрын
I have a Superflow flow bench with the wet option that uses fluorescent dyed liquid that shows flow direction coming out of the intake valve into the combustion chamber. Many two valve closed chamber heads have swirl flow (hemi heads have tumble flow unless the intake port is asymetrical). At different valve openings the swirl pattern can move around in the combustion chamber. If the swirl pattern moves over the spark plug it can cool the spark plug and change or clench the combustion rate. Also the ingnition spark intensity is dependent on the temperature of the sparkplug because electron transport needed to generate a spark is temperture dependent and related to the Edison Effect (see WIKI - Thermonic Emission). The wet flow bench can give an idea where that's possibly occurring. The intake port contour directly before the intake valve is extremely critical. This is why two different heads with identical airflow numbers can have completly different performance.
@Demoralized8811 ай бұрын
I think this is it. You have to remember that Gasoline kind of burns/expands like shit and extracting the most work out of it is highly dependent on a lot of factors.
@dennisrobinson8008 Жыл бұрын
The 529 ft-lb of 6.2L is incredible out of the TFS, it shows incredible efficiency.
@vikenlink Жыл бұрын
Hello Richard… great video. Im glad that you used a more less stock LS3 for the testing. Shows more real world results for the average person that doesn’t have a monster cubed engine. I’m guessing it’s minor differences in combustion chamber shape design, plus the minor differences in port volume between the heads explains why the AFR shines.
@spikymikie Жыл бұрын
So were talking about a 2% increase (approx). Maybe valve spacing , or subtile differences in the cnc work . The AFR heads are obviously moving more air at higher RPM. But again, barely 2% difference. And that is about the difference in intake port volume. So, math and stuff.....
@evcass69 Жыл бұрын
From what I've read, Tony Mamo was the lead head specialist at AFR, and his manual porting designs of their cast heads made it into these castings. So effectively the AFRs are cast versions of Tony's manual porting techniques. When Tony left to create his own company, Mamo Motorsports, he's spent a lot of time porting the TFS260s also. From forum posts, it appears he sells more ported TFS. IIRC, his ported TFS have better CoD than off the shelf AFR.
@johnprince7510 Жыл бұрын
I believe you are referring to his TFS LS7 head. Since AFR does not have a LS7 head Tony uses the TFS casting.
@barryfoster62657 ай бұрын
I called Tony when it was time to order heads, and he got the AFR and his thing with those.
@popeye0895 ай бұрын
Read several forum posts by him and he is using the AFR for the ls3
@jonathantrimble93694 ай бұрын
Running Tony's heads, they're a good deal for what you're getting.
@gwilson9445 Жыл бұрын
Had both on the flow bench and the AFR’s were superior to TFS in our tests. TFS weren’t as advertised.
@rustysausage69 Жыл бұрын
Lower than advertised I assume?
@gwilson9445 Жыл бұрын
@@rustysausage69 yes lower. So were Mast.
@atheplummer Жыл бұрын
I would check the short side radius on the intake side of both heads. I suspect the AFR's are probably a little straighter (less of a curve). If that's not the case, I'd then look at the 'pinch point' where the boss for the intake valve goes through the port. Might be slightly smaller on the Trick Flow.
@Saddedude Жыл бұрын
I was thinking either that or valve angle.
@pbadasay8 ай бұрын
Love how any time I think of a comparison or want to learn something, Richard already has a video out on it haha great guy, keep up the great work and one day I’ll have my motor built
@jhutch1470 Жыл бұрын
My thought is that if everything else is the same, the AFR with the slightly more port volume made slightly more power. That was the only difference between the heads.
@TheRdub82 Жыл бұрын
Maybe the small difference was the port volume 🤔?
@ericsmcmahan Жыл бұрын
The air speeds in conjunction with the lay back and height of the short side radius on the afr heads is where the difference is.
@TurboDog73TX Жыл бұрын
The difference IMO is port DESIGN, and chamber design. AFR has usually excelled in these areas over "most" of their competition.
@Hjfvvdst Жыл бұрын
Springs may play a part. Rocker geometry. Valve job. Valve angle.
@cedricwilson2055 Жыл бұрын
That would show up in more or less flow. They were neck in neck
@mr2hard2see Жыл бұрын
This vid is golden this is exactly what I’m shopping for right now.
@DragonFireEngneering Жыл бұрын
While the flow bench numbers may be nearly the same the port shapes (intake and exhaust) on the AFR heads may be working better with the intake and exhaust manifolds. It certainly appears they are flowing more air at higher RPM with the only difference being tested on an engine with intake and exhaust systems.
@michelcote Жыл бұрын
David Vizard would look into Port energy this is flow velocity time the mass flow and valve shrouding could make the difference you are looking for.
@lucascb750 Жыл бұрын
LS3's are over valved relative to their bore size, not that its bad. That is why porting them and not killing torque below 4k rpm is tricky. So I would say the difference is really due to where the engine is making power, relative to each heads runner size. It's just able to pull better on the AFR and achieve higher port energy with it. The TFS may catch up or surpass with more displacement, compression, or rpm if it were made available, but port energy, average port speeds, cannot be discounted or ignored.
@kellyheath8547 Жыл бұрын
AFR did their homework. A couple years ago the talk was about wet flow (maybe from edelbrock). Maybe AFR did a little more work with wet flow in mind. Or maybe that 69cc is actually 66. Maybe the port length is a little shorter moving the powerband up just the little bit to carry torque and hp higher.
@dannytravis7118 Жыл бұрын
I read an article years ago about AFR heads and there's more to heads than just air flow. AFR heads also tries to maximize air flow while maintaining a good balance of air flow speed and turbulence to better mix the air and fuel. That works great for carburetor engines, but I don't know about fuel injection. I can understand it working the same way if the fuel has to go in through the intake valve, but direct injection has the fuel injection straight into the cylinder and the heads only flow air. With your history and knowledge does that make sense from the testing you have done.
@JamesStover-gr3hw Жыл бұрын
Love back to back tests like this
@GroovesAndLands Жыл бұрын
I'd like to know what valves and hardware the heads both have. That modest power difference could perhaps be explained If the valve/retainer package on the AFR heads is a fair bit lighter than the parts on the TFS heads. Theoretically, any work put into compressing the valvesprings should be given back to the cam when the springs expand again on the closing ramp. This would be totally correct except for the bit of heating effect on the spring when compressed/strained - and also the inertial forces of the valve trying to hang open (newtons first law). The differences are small, but again, if the AFR valve package is notably lighter, I think it could explain what we're seeing here. It jives the effect only becomes notable at higher RPM.
@boydw1 Жыл бұрын
My guess would be that the AFR has better turbulence & swirl behavior.
@HeadFlowInc Жыл бұрын
Since both heads have very similar measurable flow numbers the difference in power has to be related to port swirl and atomization. Both heads have the same chamber cc but are there any differences in shape to alter the flame front? 🤔🤔🤔
@cedricwilson2055 Жыл бұрын
He didn’t mention a change in timing
@richardholdener1727 Жыл бұрын
both wanted the same timing
@stephanM58 ай бұрын
I'm going to go with valve grind and seat angle difference between the two head brands. Both heads are amazing btw.
@brendavanorden95508 ай бұрын
There are many reasons one could think of. Most are already stated here. Shrouding if the valve has been move to solve this. Spring rates, better valve to cam geometry, Cam spec'd for the head/combo, better exhaust alignment. Flow is not everything. Port design/alignment to it's counterpart makes the best combo. The day and time you ran the dyno? Was the atmospheric pressure the same. Water grains and so on. Push rod length to the exact will give a little. Shit the list goes on. But for the $$$'s spent on heads the stock ones sent to Texas speed would be my pick.
@genemounce8302 Жыл бұрын
Sunday morning video..... wuuuuuuuuut? Appreciate it R.H. !
@takeit2-11 Жыл бұрын
Thank you for another informative video. You know what I want to see... how much power can you make with the crate or junkyard 360 magnum, stock heads and a turbo! turbo magnum! turbo magnum! turbo magnum!
@shane-222 Жыл бұрын
Swirl / combustion efficiency will lift torque everywhere. That really looks a lot like higher port energy.
@jacktupp14272 ай бұрын
Ok, im 1.15min in to this & you have asked a question. 🤔 is it retorical... nar. Assuming all the info you have given us is correct & they for most part in the features you have identefied. I'm going with (valve) trumpet maybe seat cut, something valve 🤷♂️
@nilsthemis Жыл бұрын
Maybe differences in deck thickness and water jacketing make the AFR heads retain more heat.
@CypHill Жыл бұрын
My guesses would be either the shape inside the ports or valve chambers or perhaps if there is variation in the surfaces of the intake ports.
@drivinwithdrew7676 Жыл бұрын
Check valve angle, valve spacing, and chamber shrouding
@GapdU4 ай бұрын
Difference is between valve back cut and undercut. Could also be that the AFR heads use lighter valves.
@crashbandit9949 Жыл бұрын
Just out of curiosity what's the swirl ramp look like behind the intake valve on the two different heads?
@dennisrobinson8008 Жыл бұрын
Maybe the difference in power was the camshaft favored the AFR with the exhaust split. Perhaps TFS did not need as much exhaust split. AFR Flow numbers: LIft Value Intake CFM Exhaust flow CFM .200 159 112 .300 234 158 .400 293 207 .500 336 235 .600 366 248 .700 384 255 TFS Flow numbers: Lift Value Intake Flow CFM Exhaust Flow CFM .200" 146 113 .300" 231 171 .400" 294 215 .500" 334 240 .600" 363 252 .700" 382 258 AFR also has 13 more cfm on intake @.200".
@dennisrobinson8008 Жыл бұрын
I had time to think about it. I believe the .100 and .200 lift points of the afr had more flow enough to let the camshaft act slightly bigger due to more effective flow at low lifts. This increased power at higher rpm. I'm also curious as to the intake port entry vs the manifold.
@japjoem40776 күн бұрын
Would be cool if you compared the Frankenstein heads too
@benwingo6675 Жыл бұрын
The afr head has better flow most likely because of valve angle they have less flow restrictions because they have less shrouding when the intake vale pops off the seat.
@davidshields302 Жыл бұрын
AFR relocated the valves in the combustion chamber thus reducing their shrouding.
@logician7517 Жыл бұрын
Would like to see a similar test on a SBF between TFS 170 11R and AFR 165 Renegade. Maybe a 331, about 220 degree duration cam and Performer RPM intake.
@chipcurrey653 Жыл бұрын
True it was really important whether you made 350hp or 360hp back in 1995
@sounddevicesmike Жыл бұрын
I also want this, but I wanna see it on a 306 and a 331/347
@logician7517 Жыл бұрын
Yes, I'm sure that they would be close to each other, but is one actually superior or the other? Is one better on the low end? High rpm? And people do actually still build these, as well as 350 Chevys, 383 Mopars, etc. If these don't interest you, then stick with the LS, Gen III Hemis, or Coyotes. I happen to like all of them.
@SlingSalsa Жыл бұрын
valve angle? TF has always played with valve angle and spacing, I remember when the first set of twisted wedge heads came out for the old 5.0....
@andyharman3022 Жыл бұрын
Which way does the 2-3 cfm flow difference go between the AFR & TFS? Is it always in favor of the AFR? A 2-3 cfm difference at low lifts (and therefore flow rates) can help significantly. But anyway, for a stock displacement LS3, aftermarket heads are not a good value in terms of Dollar per HP. 40 HP (max) gained per $2600 for a set of heads. That's $65/hp. The best value is to spend $5-600 on a cam and springs, and you get 50-70 HP.
@maybelive765 Жыл бұрын
Very true. Whats your thoughts on Carb conversion? worth it for the money saved?
@allenbrixey1122 Жыл бұрын
Valve train is the difference. It takes less horsepower to run the AFR's valves and springs.
@michellee8369 Жыл бұрын
Alloy disperses heat sink better than iron which equals more timing but maybe one alloy head disperses better than the other alloy head. Interesting to see the timing graph overlay between the two alloy heads cheers Richy from 🇦🇺
@richardholdener1727 Жыл бұрын
same timing on both
@brokejoebuilds5165 Жыл бұрын
My guess would be air speed difference over the short turn or more of a variation port to port for whatever reason. 😅
@jarrodburke4685 Жыл бұрын
Hey brother, I work for a performance shop and one question I’m super curious about and we’ve never had a back to back test is Frankenstein’s and Brodix heads in the mix. That would be awesome if you could do that. Thank you sir for all your hard work!
@loundclear9279 Жыл бұрын
Frankesteins wont out flow brodix heads not in mid flow not in max flow. but would be nice to see i got a set of brodix heads bx 300 , we had frakinestiens befor changing over
@richardholdener1727 Жыл бұрын
you need a lot of motor for those heads
@jarrodburke4685 Жыл бұрын
Yeah, most of the setups are the supercharged motors.
@loundclear9279 Жыл бұрын
@@richardholdener1727 Facts we switch over because we felt the mid range was soft for a 434 tall deck lsx twin 85mm turbos. pick up big time everywhere on the brodix heads.
@1kjoseph Жыл бұрын
@@loundclear9279switching from what head to Brodix??
@johnginnitti4452 Жыл бұрын
Could be the valve shape, gow air flows off the short side, fuel distribution or combinations of all.........
@picklepee2771 Жыл бұрын
I would honestly like to see the differences of a ported head and cam on the ford fiesta's 1.6 ecoboost, because there have been zero documented runs with a head and cam 1.6 eco boost.
@jmflournoy386 Жыл бұрын
did you try swapping the valves? touch up the valve jobs valve job analysis valve analysis stem coatings. finish, materiel, shape? TI option Inconel option common sizes chamber analysis' any differences in guide materiel, seat materiel? (like for HD) velocities? which? blower I've wondered why not a canted valve head with a semi rotated chamber cheers
@GrandPitoVic Жыл бұрын
Valve cut can make a difference. I've read the 823 heads had a 3 angle valve grind and the 821 had 2 angle. I'm not sure how true it is. You know how the internet is. Valve angles do make a difference for flow.
@Ws6Ms Жыл бұрын
The 821s are better
@aphil4581 Жыл бұрын
Johnprince got it. Moving the valves closer to center for more valve relief. Saw this on a head porting chanel. ls3's like valve relief! Looks like you used the stock intake for low rpm. Is the valve pic showing the afr head intake valve moved over the centerline between the two valves?
@timothycraft5448 Жыл бұрын
I’m going to say valve springs. Everyone always forgets about valve train. Springs make a difference.
@clueless4wat322 Жыл бұрын
This is great information, this will be one of my last mods after I go blower/boost for better efficiency and not cranking up psi. I wonder how much of an increase we will see if this was running on 10 psi, you think it will be similar 40hp gain or a lot more?
@cedricwilson2055 Жыл бұрын
He has tests up for what you’re asking. More na hp more blower/ turbo hp.
@bannerrecording Жыл бұрын
What about oil pressure? I don’t remember this being mentioned but my thought is maybe if the way the oil flows through the heads is different there may be slightly more resistance. Or is that a long shot? Possibly the same idea with coolant through the heads. More heat, less power.
@stevenbelue5496 Жыл бұрын
Valves, tulip or back cut variances or valve job variances. Port shape or finish, where are those 5 cc'?, chamber shape, finish, afr lends itself to better swirl and tumble or better quench for better fuel mixture/atomization.
@stevenbelue5496 Жыл бұрын
Maybe bowl and throat percentages
@jeffg4008 Жыл бұрын
Was the valve spring package the same? The AFR may have been slightly better at controlling valves (bounce at the seat). Maybe it had lighter valves and retainers or a little more appropriate spring for the combination.
@cedricwilson2055 Жыл бұрын
Valve float dyno curves don’t look like that
@jeffg4008 Жыл бұрын
@@cedricwilson2055 Where do I say float? i didn't say valve float, I said bounce. Clearly the spring wasn't in full float but a proper spring/valve comb is worth power on a like for like situation.
@edwardwood3622 Жыл бұрын
Because Brian Tooley doesn’t work at Trick Flow anymore?
@circleprecisiontool7645 Жыл бұрын
Intake and or exhaust port alignment.
@kylemilligan752 Жыл бұрын
Looking back at your previous LS3 tests, it seems the baseline was down on power. After valve jobbing LS heads with some heat cycles, there's always a couple valves not sealing 100 percent
@richardholdener1727 Жыл бұрын
that was mentioned
@LT1fieroman Жыл бұрын
Perhaps the valve guides are more streamlined in the AFR
@aaronliddell4280 Жыл бұрын
Now do this TFS vs AFR on a SBF pretty please 🙏
@Calvotuned Жыл бұрын
Richard, do you have any comparable data or anecdotal information how the AFR and TFS heads compare to stock heads that have been CNC Ported? For example the TSP CNC porting on LS3 heads.
@richardholdener1727 Жыл бұрын
only compared to stock
@jimstover6747 Жыл бұрын
1 1/2 * of valve angle. TFS is 13.5* VS AFR 12*
@martygrajeda3457 Жыл бұрын
Thank you, Richard, for the information 😊
@peteJoseph-x3h Жыл бұрын
Did you mention they’re both 12 degree heads? The AFRs are 5cc bigger and have a different shape in the ports.
@johnsheetz6639 Жыл бұрын
I'm going to guess valvetrain control on the most minuscule scale. A little wobble somewhere.
@nemofoss98873 ай бұрын
Valve location? Maybe afr are further from cylinder wall?
@davidresar8256 Жыл бұрын
Maybe valve shape? Maybe valve angles?
@keithhuhn2245 Жыл бұрын
What is the water jacket size on the 3 sets of heads? There could be a heat difference. 😊
@tylersmith7054 Жыл бұрын
Is it valve angle? I believe the TFS allows a little larger cam due to altered valve angle. With that in mind, if you ran the largest cam you could in each would the tfs then come out on top? I’m curious how my ported LS3 heads would stack up to these two. As usual we have answered a question and have new questions.
@cedricwilson2055 Жыл бұрын
Depends on who ported them. But in his ls head shootout stock heads CNC ,’d didn’t out power aftermarket heads
@shaneshane1379Ай бұрын
Velocity or chamber size. Is the valve spacing the same? Runner height?
@KNS_Racing Жыл бұрын
Thanks again Richard for these tests. Quick question, would the afr head be good for a stock bottom end LS3 with mild cam and a eaton tvs2300 PD blower to achieve a power goal of 650 to 700whp?
@richardholdener1727 Жыл бұрын
you don't need ported heads for that
@KNS_Racing Жыл бұрын
@@richardholdener1727 the shop and tuner I'm working with said that because I'm constrained to using only 93 pump gas without methanol or e85 fuel, getting maximum flow without restriction to keep boost down would be needed to make over 600whp with a 6.2
@CLEEPER110 ай бұрын
600 should be easily accomplished @@KNS_Racing
@jaysgarage4802 Жыл бұрын
I wonder if it has something to do with one these heads Possibly having a swirl ramp? I don't know much about LS3 heads but I know 5.3 heads have a swirl ramp
@3foxstangs Жыл бұрын
Maybe valve spring rates were just that much different? Or the combustion chamber was a little different?
@jasoncole5020 Жыл бұрын
I feel the Trickflow is stalling, air speed is definitely a factor here in my opinion, short turn radius ill bet the afr heads short turn is layed back alot further than the Trickflow, either that or minimal cross section pinch being the culprit
@impalasamsgarage Жыл бұрын
What about the exhaust ports? Is there something there that could lead to the difference.
@RobertHanna-j5h Жыл бұрын
What injectors did u use? For the price of the heads i would sick with the stock head
@SHONTONGA063 ай бұрын
Don’t AFR’s come with a hollow stem valve vs TFS coming with solid SS intake valve?
@utahcountypicazospage5412 Жыл бұрын
Let’s look right above the valves I bet afr is more direct
@johnmelton7877 Жыл бұрын
Difference in valve jobs? Slightly different angles?
@Fatt-billy.racing Жыл бұрын
You should have ran a bigger cam why have a head that peaks at 700 lift and not use it. Especially with that big ci.
@Tariq.4548 ай бұрын
Great vid, Thanks sir. I don’t know why AFR is better but I will give all this vid viewer an advice: Do not buy TFS in any case I tried them on 2 cars and always rocker arms are moving from their location, intake valve not open and making a big misfire in the engine. Bad quality heads unfortunately.
@richardholdener17278 ай бұрын
we never had issues with either
@Tariq.4548 ай бұрын
I can share with you the picture 😢
@starperformanceauto8347 Жыл бұрын
Difference was valve angle
@genelong1748 Жыл бұрын
Agree.
@bricewiese5082 Жыл бұрын
One has better valve job and guide clearance ?
@studbolt5627 Жыл бұрын
You should ask David visard but my guess is different port velocity
@stephenhodge6441 Жыл бұрын
Well it comes down to doing the research on the airflow. Some may call it the "air flow research". Lol
@isidrosevier1125 Жыл бұрын
Could maybe be valve materials and or weights
@bobqzzi Жыл бұрын
Are the chamber shapes different? Discharge coeficient?
@regsmith7604 Жыл бұрын
How could you not have Mast Black Label heads?
@chipcurrey653 Жыл бұрын
Because they dont donate them for testing
@richardholdener1727 Жыл бұрын
Mast Black label heads were tested many times in the past-see the big head test videos
@regsmith7604 Жыл бұрын
@@richardholdener1727 Ok
@martygrajeda3457 Жыл бұрын
Richard, I'm building a 6.0 LS 408 stroker with twin VS Racing 7875 turbos and Texas Speed Titan intake. And really don't know what heads to run. I'm not trying to set it up for the street just the track. Should I run the Rec port or the Cath port? And can you received what ones to run?
@richardholdener1727 Жыл бұрын
after market heads with thick decks if you plan to turn the 7875s all the way up
@martygrajeda3457 Жыл бұрын
AFR or Trick Flow?
@martygrajeda3457 Жыл бұрын
Thank you so much for your reference
@randallsavage3795 Жыл бұрын
gotta be the valve spring pressure
@chuckyz2 Жыл бұрын
Little smaller CC or a little more compression and a little more air flow equals a little more power.
@richardholdener1727 Жыл бұрын
chamber size was the same
@chuckyz2 Жыл бұрын
@@richardholdener1727 You were feeding a little nitrous after 5500 rpms? Idk. Tell me.
@kimmorrison9169 Жыл бұрын
Curious what the cost and availability difference is between these two very nice heads?? Thanks for a great video!
@richardholdener1727 Жыл бұрын
just go to Summit racing-they sell both
@jodysmith3662 Жыл бұрын
Port volume, even though it's only 5cc. Shows up top.
@mikeeaton9822 Жыл бұрын
I think it maybe the angle the valves were ground.
@dennisrobinson8008 Жыл бұрын
Chamber design maybe?
@lcxu10517 ай бұрын
I think you will find that TFS fudge their numbers on flow. Have heard that from a few cylinder head shops in Australia.
@richardholdener17277 ай бұрын
we flow tested both
@lcxu10517 ай бұрын
@richardholdener1727 so you can confirm that they flow what TFS say they flow. As a few companies here in Australia have said AFR are just about spot on and TFS are out by upro 15cfm
@natelsx Жыл бұрын
What was the amount of timing for each head ? Curious on the differences.
@richardholdener1727 Жыл бұрын
SAME
@natelsx Жыл бұрын
@@richardholdener1727 how much ? Or is that a trade secret ?
@richardholdener1727 Жыл бұрын
30 degrees at the hp peak-there are no secrets here
@arminmihandoust94694 ай бұрын
Richard, have you done any testing with the Frankenstein M311 heads?
@richardholdener17274 ай бұрын
no sir
@arminmihandoust94694 ай бұрын
@@richardholdener1727 I just bought a set that I'm putting on my 416" LS3 with a D1X and a Holley Hi-Ram pushing 17psi. I made 940whp with that set up on the stock heads. Hoping to see a decent gain with these M311 Boost heads. Btw I made my choice for intake manifold based on your great videos! Kepp up the great work.