Following up on my latest video of managing high compression. Covering off a few points including why quench is important.
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Following up on my latest video of managing high compression. Covering off a few points including why quench is important.
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The way to beat having high compression and management problems is to go big block, 9 to 10 CR is all you need.
I have a question about quench, wouldn’t the quench height change on a hot engine vs. cold engine? Do you compensate for this?
I really enjoy Ben Alamedas channel. He is letting alot of racing secrets go lol. You are very knowledgeable as well as Ben.
Running high compression on pump gas ⛽️ is waste of time.
Tight quench with long duration cam n anything is possible. I run my Big block chevys at 32-35 quench
My father was a drag racer and a very accomplished engine builder .He taught me as a general rule ,each point of compression increase over stock /starting point is on average 2HP per cylinder per point of compression increased over your starting point .
Hey AG,
Tim here. What a great tech vid…..LOTS of smart thought…..my Poncho 462…..has a quench of .040, cuz i use i stock style flat top piston, yes i have 4 valve reliefs, so i have 0 deck, and .039 compressed head gasket, and 2 valve reliefs in quench area, netting a 3 cc loss, over all creatting a .040 quench……(#'s are close not exact)……my static is 10.44:1, modern heart shaped chamber, i run 31° of total…..my Kauffman guys said i can even go to 30°…..its an efficient chamber, yet i STILL have detonation symptoms on my plugs, as tiny white deposits… i was runnin 93 pump gas, i changed to 90 non ethanol, got mildly better, added 1 gal of 110 to 4 gal of 90, netting 94, and its happy… must look at camshaft…. i have no card, its a custom grind done by my brother and his dude (Larry Hansen Racing) all Pontiac nerds….. but i have a bigger cam i was gonna put in, and wanna look at the intake closing event, and see if its within ur window….. NEAT stuff, i got alot to sort out, my 11:07 shud be a 10:98……so i'm workin on it….sorry so long, i ENJOYED this vid immensly!!!!…PEACE to you sir!!
A lot of this stuff has to do with resonance frequency, everything has a resonance frequency, A tube with a fixed cross sectional area will have a resonant frequency. An intake manifold will have one too and the engine will make max torque at that RPM a ( standing wave pattern) The pulse stacked behind the intake valve closing when it becomes stationary will make max torque…… but the runners are not equal so you will get a band of max torque. instead of a single value. When you have a whole series of pulses stacked behind the intake valve you will have a slight forced inducted effect
327 Chevy, 14:1 compression
Bp-98 octane (RON)
Pump Fuel
Water injection works well with high compression as David Vizard says…
AG, .040" to .045" is good as the standard. Quench depends on how much piston rock you have to makesure the piston doesn't hit the head or barely touch. Rpm is involved also AG.
Good information. How much cranking psi for 87 octane gas in a properly managed sbc 350 engine for a pickup truck
aluminum head’s definitely not iron and lots of camshaft. Also this is why heart shape chamber works so well makes mixture go to the center
run off the shelf cams and they from CC and they are very low dynamic compression. and for the fun Cars wanting 13:1 compression there is GOGGLE And VP/Sunnco. etc 120 + race gas for that 38 degrees of fun time
Just my opinion. Since Obama, and then covid. A large majority of the USA population have figured out how to not work for a living. So they breed in they're Mom's house or aunt Margaret's home for free. They also mooch off of other's internet, an become keyboard warriors. Looking mostly at pictures, an reading between pictures. And become experts on conversation. But never turning a wrench or driving cars they build. I ignore them. They're easy to spot. Anyways, please keep feeding us knowledge Allen, please. Don't respond here because of any negative impact on your channel. But many of us appreciate your time and knowledge. Thank you A.G.
Deck height is affected by block material and piston CD.
An Al block will expand more as the engine warms up so cold deck height can be a bit less. A tall CD piston will expand vertically more than a short CD piston which will require more quench clearance. Of course parts will stretch a bit as the RPM goes up and more as the rev limit is increased.
All these things need to be balanced.
Thanks Allan for the video. I really appreciate you going back to cover the quench topic. An old engine builder told me that in the high performance muscle car days, engineers tried very hard to focus the quench in the combustion chamber to eliminate knock and pre-detonation. When the smog era hit, the engineers threw it out the window and started casting open chamber small valve heads. Great video and thanks again, I really enjoy the channel!!
Great channel. doing a great job. and yes can learn alot over on bens too. Another channel everyone should swing into is Uncle Tonys Garage Keep up the good work buddy love your channel. many things to learn..
This is exactly why i love this channel. He takes on direct questions being left here and takes the time to explain..
The snow is almost gone where I live, almost time to pull out the old car!!
Quench dimension is relative to Bore Diameter, Valve placement(ie: opening backside of cylinders or on center)… and Intake/Exhaust Flow ratio as it relates to scavenging.
Just say'ing for example…..
FAR more going on…. one size does NOT fit all… and that saying .040"/.045" or even.050" quench is optimal(maybe on a sbf or sbc 4.00" Bore) ….or that "closer is better" is erroneous as to application ?
and fails to capture the above parameters that may indeed result in over-scavenging a cylinder with a gifted Exhaust Flow blowing perfectly good incoming A/F charge right out the exhaust !
I've personally documented on the Dyno a gain of 35 hp peak(820HP TO 855 HP) by merely INCREASING the quench distance from .055" to .085" on a 4.500" Bore 540 Inch Wedge…. NO OTHER CHANGES THAN HEAD GASKET THICKNESS right on the Dyno…. which lowered Compression/Increased quench distance and resulted in the gain.
We can also run HEMI's very close to 200 psi dynamic on 91 Octane with NO quench given the design with no detonation well past 950 hp.
"why not keep going with the compression?" – We do!! That's why we use turbo's, blowers, super chargers, etc.! They all equal higher and higher compression, hence more and more power developed!!
Good info! Thanks for sharing!
Use Marvel Mystery Oil to wet the charge. You can also delay the timing advance curve instead limiting your total advance. If you still get detonation lower your spark plug heat range or use water/meth injection. I have a BBC 15:1 and use 91 octane +MMO, 20 degree initial (manifold vacuum so vac adv is included in initial) 36 deg total 52 degree cruise.
common sense 10 hp will not be felt keep it happy easy on the wallet too, great advise there will always be someone quicker,
I have a 385 SBC with a .000 deck AFR 195 using a copper head gasket.042 2 eyebrow pistons. It's a 11.25:1 . It has 185 lb of cylinder pressure.. It runs pretty good. All cam specs are done using David Vizard s 128 formula. Again GREAT videos.
ben is so good even talking about iron heads verse alloy
common rail diesel use injection timing to light the fuel they can fire the injectors 7 times per stroke.. usually they do a really lean squirt of fuel so it lights up and then they fire the many charge. the actual quick way to set it to single fire and hear the pinging is to disconnect the air flow meter .. it will go into limit mode or base tune and will ping like old noncommon rail diesels. don't recommend this you'll need a scan tool to get it out of limp mode
United Engine & Machine suggests adding 15 degrees to your intake duration @.050 when figuring static compression ratio. On "my" particular engine it's accurate when determining intake closing point.
Will flatter pistons let's say 11.5:1 not have a better flame travel and timing will be more advance and still out of detonation, and with a tighter cam will achieve the same 200psi cranking pressure and run as fast as the 13:1 with all opposite things of what I mention, plus it will be cheaper to build and last longer?
Good morning, Bob again. Building my 1964 283 I am looking at crankcase ventilation options. Of course the motor is set up with valley ventilation through a downdraft tube but I don't think that is the right option. I can purchase the adapter to PVC or use the valve cover PVC ports. If I use the PVC system I am assuming then I would old have ventilation on on valve cover and not connect two. The other option would be valve cover push in breathers. What is your opinion? And who takes care of your beautiful landscaping by your driveway! Great look. I am inspired to pick up my game a bit!
Does anyone know what the actual bore measures in a 350 ? I heard it's not actual 4.00" …it's 4.0030?
I'm really enjoying this series of compression discussions, thanks for going so deep into this subject! I'd love to hear your thoughts on an engine I'm planning, especially if you have anything to say about the functionality of water injection for preventing detonation in high-compression naturally aspirated engines (not really talking about water/methanol injection for forced induction). It's going to be an air-cooled Porsche flat six, so we're talking aluminum SOHC hemi heads with twin spark plugs, sequential port fuel injection, 4182cc (255 ci), with a MoTeC computer to handle fuel, spark, knock sensors, and (if I add it) water injection. This would likely be on a cam with 302/294 advertised duration, 282/268 at 0.050", intake closing 58 degrees after BDC. I'm considering compression ratios up into the 14:1 to 15:1 range. Fuel would be 93 octane pump gas. Do you have a method to estimate a ballpark compression limit for a setup like this to run without detonation on 93 pump gas alone? And if so, do you have any thoughts on how much additional compression would be safe with 93 + water injection (no methanol)? Some of the elements I am considering here are: (1) Hemi heads are usually found to resist detonation better than other combustion chambers; (2) Aluminum heads resist detonation better than iron heads; (3) Twin plugs should be able to make the same power at any given timing as single plugs with more advance; (4) The combination of 3D (RPM-throttle position-manifold pressure) fuel and spark mapping together with knock detection should make it possible to set up an engine that retards ignition or even cuts fuel under knock-prone conditions (such as lugging) while still running aggressively advanced timing at high RPM. I'm wondering if all of these elements would make 93 pump gas alone completely workable at 14:1 or more? On the other hand, would the carbon-cleaning and hotspot-cooling (especially in an air-cooled head) make water injection worth it to avoid developing unexpected knock over many thousands of miles?
You need to do a 351-C build and compare it to your SBC. A 351-C with the Closed chamber 4V head. I never see any ford builds on your channel. I think you could build a monster SBF with your knowledge.
Yes Allen. I was wondering about quench in your last vireo as well. Is .030 too much? I'm refreshing an 84 vette using the stock TRW forged pistons, ,022 in hole wiith.015 gaskets, That gives ,037 quench Too? much