So getting back to the question that sparked this pissing match:grin:, do you ever want the intake port to be bigger than the head port? I've always read that that is a big no-no. The last thing you want is air hitting a ledge of the smaller head port. I would leave the intake ports alone, they look very nice. TA's description of the SP1 says, " In most cases, each runner is capable of flowing more air than the cylinder head can deliver, ensuring that the intake is not a restriction." I suspect this is probably true of the SP3, especially with most iron 350 heads. Bottom line, leave it alone. Evaluate the intake the way it is. I wouldn't touch it until the 350 aluminum heads come out.:TU:
Why do you insist on these thread killing arguments? Maybe if you invested your time into learning hands on and buy the tools to help you learn like the Engine analyzer pro (see graph below) that piggy backs my Air Flow analyzer pro on my flow bench which you also think is flawed instead of taking part info off web sites you would actually learn how things actually work instead of getting in over your head. Note the green line on the chart below, stop over thinking things, this banter only kills thread and stops people from posting and kills threads like my cylinder head thread. Now that the gentleman's thread is completely off track and destroyed. It was a great thread. There is a reason I haven't been posting for along time and this is it and this is a perfect example why.
Friend of mine was just telling me a few weeks ago that while talking to the head porter at Clements Racing a local Busch team and sealed crate engine builder and the one of the outsourced Machine Facilities for Dart products, about his intake for his 1100hp C3 yates headed street car that said porter done for him he aske why it was slightly smaller than the gasket edge/ head port entrance. His answer was that after grabbing the wrong intake in the dyno room he discovered that a slightly smallerintake exit made more hp and TQ, it was marginal but better none the less. And them boys will chance a tenth of a hp like a mad man, so after more testing he concluded it worked and now employs it on their builds, just something to think about
Size is most important, you need a dyno and a flow bench to find any of this. Some of the rules that apply to a actual intake runner/port do not apply to the intake manifold plenum. You can grow old trying to figure it all out. :TU:
Anyways, Here is an example of my friend's ~800HP 545cid BBF, where this setup was tested and shown that there is no significant improvement matching the intake runner to the head. It's a heck of a difference, you can practically fit a tennis ball in the head port! This thread got me thinking about my 455 SPX setup, and since I have it apart I took a look. I need to trim my intake gaskets a bit as they are the narrow point. I'm not going to further hi-jack this thread with my SPX pictures, they're in my project thread if you want to see.
During the intake stroke, the intake valve opens and the piston moves down in the cylinder. This increasing cylinder volume creates a cylinder pressure which is lower than atmospheric pressure to draw air into the cylinder. You probably think the piston is "sucking" the air in, but actually the barometric pressure is able to push the air in because there is less than atmospheric pressure in the cylinder. "barometric pressure" is what aids the filling below atmospheric pressure while the piston pulls it in. Everyone is partly correct.
Thanks! I think they are charging around $379, not sure about GS air cleaner fitting though. Quick update, waiting on parts to arrive Monday afternoon. Everything was mocked up a few times to cut on future gremlins. Finished up under the carb plate, it's not art but it all looks something like this.. And to give everyone an idea of what the heads look like.. Nothing really fancy with the heads, I've learned to be rather conservative after I destroyed my original set trying to overdo it. Get it painted and assembled tomorrow, and possibly driving Monday or Tuesday. Larry, I'm installing as is.. I smoothed some things out but that is about it. And as you mentioned, I'll get serious when the aluminum heads arrive. But everything will be sent to a professional!
Thanks! It could be better I'm sure, but it is a ton smoother then the 90 degree that was there! Still on track for Thursday as long as there are no hiccups. Buick folk will be Buick folk, who am I to interrupt an informative debate on how to improve our hobby :beer:
Justin, RE: rolling the corners on your intake.. anything is better than a sharp corner. As far as port matching, effectiveness depends on how hard you are taxing the intake in the combination. 6 or 7 years ago I did a comprehensive intake test on a 515 HP Alum head 464. Started with a performer, then went to a 70 iron manifold, and then to an SP-1. All manifolds box stock Performer and Iron ran right on top of each other when stock.. Then the performer went into the porting room, which is just across the hall from the dyno. While we tested the SP-1- Bryan port matched the performer. After re-installing it, we were surprised to see it picked up 15HP. Did the same thing to the Sp-1, and it only picked up 8 HP. (was the new style SP-1 with the CNC'ed exits) The bigger SP-1 was not being "worked" as hard as the Performer, therefore the increase in cross section had less of an affect on the combo, with the single plane Sp-1. JW
Jim, Read you loud and clear, thank you for your continued support! Mark, Not a chance my friend haha
I learned this my senior year in highschool physics. Devon is right. There really is no such thing as vacuum. I've had this argument several times, and as a result I've gotten a few cases of beer free! :Smarty:
Got it all installed, looks good! Runs like crap though. It appears to be running off the primaries and not the idle circuit. Puddles of fuel on the primary blades.. and a whopping steady 5hg. Time for some adjustments. No major leaks though, time to backtrack and figure out what I did wrong. Oh and forgetting to put in the secondary rods and hangar is not recommend on first start up. Oops.
Why are you bringing this back up? The sentence that Devon copied and pasted proved I was right! Excuse me for incorrectly using some terminology. The low pressure above the piston causes the air to be drawn in, what he copied and pasted. The piston is after all of the ports. Drawn in, vacuum, sucked whatever you want to call it dude. Its the low pressure in the cylinder at WOT that draws in the air, I wasn't trying to explain what is happening at idle or cruise or with a economy carb. With a cam that has a lot of overlap and tuned headers even more draw(low pressure situation) will happen from inside the chamber AFTER the ports where the "pushing" is just above the piston still after the ports at WOT because opening the throttle allows the low pressure in the intake to be drawn in just above the piston where it is pushing in drawing from the ports where the majority of airflow is concentrated in the center of the port. I wasn't saying to make the manifold port larger than the head port, I was saying if that is already the situation to not worry so much. And then we get Devon the thread destroyer pop in because someone used the wrong terminology, sad! Then he copy and pasted something that proved me to be right to top it off! Here is a answer to that question from elsewhere from how it was originally explained to me but my CRS had a hard time trying to explain it; http://www.onallcylinders.com/2014/...-rectangular-port-intake-big-oval-port-heads/ The above should make this more clear for everyone. Derek
Yup, something's up. You're using the same q-jet, right? It sounds like the primary rods might be stuck in the "up" position. They're supposed to be down at idle. I wish I had a good photo to offer, this is something you can check with a small screwdriver by pushing down on the top of the hanger while the engine is running. Easy to write this, hard to explain without pics. Devon
Thanks for your help Devon, I do know what you mean, but it is a bit too late here for me to start the old girl up and give it a check. It is the same q-jet that Ken re did for me, and before the intake swap and me diddling around with some adjustments it was a great carb. A bit of back tracking and some basics I bet I'll have the old girl singing again. And of course ensuring the primary rods are set as you recommended. Thanks again! Justin
Justin, Thank you for enduring the whole diatribe. Looking forward to your progress! Signed, Killer of All Good Threads
