I flow two AFR 210cc heads with two drastically different chamber sizes.
Пікірлер: 37
@patx35 Жыл бұрын
One thing I remember about chamber sizing and power, with valve jobs and combustion volumes being equal, the engine with the smaller cylinder head chamber volume would make power more efficiently than an engine with a large cylinder head chamber. Something to do with reducing the amount of dome on the piston, while having the same compression ratio, would help increase combustion speed, and would also reduce the ignition timing advance needed to make peak power. It apparently also reduces the octane requirements, between having a faster combustion speed, and having less surface area in the combustion chamber, which both helps reduces the chances for knock. If possible, it's one of the things I would like to see tested on the test mule if that theory by itself holds true, or if there's factors missing on that theory.
@pacman3908 Жыл бұрын
It's called more quench
@flinch622 Жыл бұрын
As I think about it, the stream of exhaust pulses moving down your headers present a net negative signal to the intake during overlap. But the chamber tilts things. So we can think along the lines of vacuum. That means... the combustion chamber behaves kind of like an accumulator: the smaller the chamber, the faster it can equalize, therefore intake charge can begin moving sooner. Thats not exactly what happens of course, :but objects in motion tend to stay in motion, and so it is with the bulk of exhaust gases and their net effect on intake charge. Overlap time is a very small window and it gets smaller as revs go up. If I didn't screw up the math, a 58 degree overlap at 6k rpm's is 3.2 milliseconds [as cam is half speed of crank]. Do valve jobs matter in such circumstances? Oh yeah. Any pros want to correct the math, thanks in advance.
@Baard2000 Жыл бұрын
@@pacman3908 its more efficient combustion. Look at the Trick Flow Ford head making with a specific cam , rockers and springs making 423hp on a 302 according to Trick Flow . Intake airflow is ( by head so I could be off a little) 265 cfm. I have made several 289 cast iron heads ( 1963 to 1966 ) only having intake air flow of 208 cfm as restricted by valve size as per FIA regulations , and designed for endurance ( hours of Spa , Classic Le Mans ) therefore also limited to 0.530 lift as ball rocker will burn if more lift used , but making 438 hp on a real 289 ci engine with dual plane Edelbrock. Main difference is combustion chamber design. Actually....dome height/ size. Thats what makes the power. Whereas for first years working on those 289 aiming for highest airflow with still stable head design as its used for endurance ...I now balance between airflow and dome size to extract most hp. And for some its hard to believe as they want to see high airflow numbers regardless of how chamber shape gets achieving the highest airflow.
@terryenyart5838 Жыл бұрын
Be very interesting to see how the dyno #'s would look between those two heads as CFM is not everything. But great info!
@timrayburn2461 Жыл бұрын
Great video,thanks Eric
@TN_Country_Boy Жыл бұрын
I respect you don't want any drama, so deleted comment , Thanks for the content 👌
@richardboggs260 Жыл бұрын
Very good information Thank you for the video!!
@pizzandoughnutspage7817 Жыл бұрын
Great info Eric, it is amazing the order of operation to make the head come out correctly.
@robertkeime4907 Жыл бұрын
Great video
@racerd9669 Жыл бұрын
So to make the same compression with both heads the 70cc head will need an 15cc dome on the piston. So in reality when the engine is assembled which cylinder will have better flow, the one with the dome or the one with a flat top piston?
@mikasantos3774 Жыл бұрын
I bet the 1 with the flat top
@bengibson8778 Жыл бұрын
There is a great calculator on Wallace Racing Calculator
@xlr8r3VA Жыл бұрын
Great video Eric! I may have missed it, but is there a difference in flow between the stock heads without milling (comparing a 76 cc chamber to 66 cc chamber?) Thanks!
@MikeWolf-4275 ай бұрын
Do you have any advice for switching to an aluminum head? I have a warmed over '69 412 block 427 with 840 heads. Compression is around 11:1 and it's around 500hp. 840 heads are a closed chamber 107cc Rec port. I need to cut some weight without losing any Tq/Hp in my Nova (3650lbs with me in the car)
@kevin_m110 Жыл бұрын
Get holes perpendicular to the deck, not parallel. I’m picking nits but I still love the content.
@donaldhalls2189 Жыл бұрын
So what is the benifit of angle finish ? thanks for sharing, all the best to you and your loved ones
@ldnwholesale8552 Жыл бұрын
Having angle milled fuelies in the distant past 0-80 theynworked well and I had 12-1 with flat tops. Would I do it agauin?? No. A decking the block achieves more for less. B if nesecary use a small dome piston. Big dome pistons are a bigger hindrance to power. Less compression is really preferable
@patrickmoore1017 Жыл бұрын
That's a very substantial flow difference, enough to make a power difference. I flat milled my AFR 220's .030 and ran into that top cut pretty good, about like the heads you have there. Plus, the chamber is shrouded more on the outboard side of the head when they're milled like that, so the chamber needs cut out to the bore size to deshroud it again. How do I fix the valve seats where they're back up to par?
@joshcampbell2503 Жыл бұрын
Greatly appreciate this video sir, I’ve been trying to learn about this a lot as I’ve recently had a set of old rhs pro action factory 50cc heads redone for my small black build and I haven’t been able to find much good info on chamber size
@TheDynotuner Жыл бұрын
Wouldn't doing a radius skim cut on that valve seat to help flow on the angle milled heads? I'd think bumping it on the Serdi would help 🤷
@raykieran754 Жыл бұрын
Does airflow velocity change when valves are opening ,as in piston starting to move when pulling air in past the valve (piston speed) compared to flowing a head on a bench with air at a constant speed or am I overthinking it
@boharris8179 Жыл бұрын
Wouldnt a larger chamber require less material removal to drop the cc volume compared to a smaller one?
@flinch622 Жыл бұрын
Lets say a head will be angle milled to get at a 21 degree setup. How to correct dowel pin holes?
@WeingartnerRacing Жыл бұрын
Great question but I haven’t had a problem with it so I don’t know.
@chriscimino7854 Жыл бұрын
Wouldn't it be easier to get a dome piston
@ragingbull3406 Жыл бұрын
Will a difference from 63cc to 70cc make much difference in efficiency all else being equal?
@DChrls Жыл бұрын
I've been watching your video's and Steve Morris's. One of y'all need to change your voice, y'all sound too much alike. It's confusing me. 😄🤪
@LowDollarDude Жыл бұрын
🤣🤣🤣
@jmflournoy386 Жыл бұрын
Changes in impingement of flow to top of the bore?
@jeffreyknitt7358 Жыл бұрын
Can a head with steam holes be used on a block that don’t have them?
@jeromewieland55 Жыл бұрын
Yes
@robertwest3093 Жыл бұрын
I'm shocked that AFR will mill into the intake seat. I would be weary.
@WeingartnerRacing Жыл бұрын
No worries. Especially since they carry a lifetime warranty