a VERY DIFFERENT approach to porting

Topic: a VERY DIFFERENT approach to porting (Read 4813 times) previous topic - next topic

a VERY DIFFERENT approach to porting

Reply #15 – March 23, 2012, 12:16:05 PM

craigslist lol i come across E6/7's all the time for $50 or less

a VERY DIFFERENT approach to porting

Reply #16 – March 23, 2012, 05:10:56 PM

I workbench ported my 2.02/1.60's on my 355 and noticed a decent gain in power. It wasnt enough to get all giddy about. the 70 belair is a 4500 pound tank after all.. But I did notice a that I freed up some low end that the car was lacking. It felt qucker off the line went from snail to turtle in my book. I hogged out the valve bowls, made the exhaust ports a humanly large as I possibly could without taking away to much and made them as smooth as I could using what I had. I hogged out the intake ports quite a bit also. I didnt go crazy on the intake side though. I deepened the port so it was almost straight down to the valve seat with maybe less than 1/4 inch lip and left the ports semi-rough.

I noticed a big difference in how it ran ,of course tuned to my liking and timed where I wanted it. So if I can do it. Just about anyone can do it. the sad part is I didnt realize how hard to find FACTORY 2.02/1.60s are for a SBC Im really glad I didnt fudge em up. Porting is easy and its a very easy power gain if you have the air power and the know-how to do it.

a VERY DIFFERENT approach to porting

Reply #17 – March 23, 2012, 06:47:52 PM

I only skimmed through the article. From what I read, he is right and wrong. Too large of ports will kill low end torque. Too small of ports will kill HP. 4V Cleavland heads are not so good for quarter mile due to the huge ports. SB Chevys seem to out perform SB Ford due to larger ports. One must keep a happy medium. From what I have been told on porting, you are not supposed to remove much. Only enough to straiten the air flow. What I have been taught in school was be leary of port and polish on intake side because it will take away much needed turbulance.

a VERY DIFFERENT approach to porting

Reply #18 – March 23, 2012, 07:08:39 PM

Velocity is what you want. It kills me when someone suggests you need backpressure for low end trq on the exhaust side! Backpressure is very bad, the correct term would be velocity needed, which smaller ports/exhaust gives, not backpressure.Kinda unrelated,Large overlap on cams is what causes the engine to run rough at idle and low rpms because there is not enough velocity to make it flow like it should, you get reversion in the intake tract etc.As the rpms increase, velocity increases and the engine starts making power. I get into exhaust technology and stuff like this. Sorry for the sidetrack.

a VERY DIFFERENT approach to porting

Reply #19 – March 23, 2012, 08:53:33 PM

yes, too large of ports will kill the low end.. as for 4V heads, i wouldn't recommend them on a stock bore/compression motor.. on a 10.5:1+ motor with at least .030 taken off the cylinder walls and a considerably high lift/long duration cam, the 4V's will kick a$$ on the track.. that being said, i wouldn't want to drive said motor on the street everyday lol

a VERY DIFFERENT approach to porting

Reply #20 – March 23, 2012, 11:00:02 PM

Quote from: V10KLZZ71S;385018

Velocity is what you want. It kills me when someone suggests you need backpressure for low end trq on the exhaust side! Backpressure is very bad, the correct term would be velocity needed, which smaller ports/exhaust gives, not backpressure.Kinda unrelated,Large overlap on cams is what causes the engine to run rough at idle and low rpms because there is not enough velocity to make it flow like it should, you get reversion in the intake tract etc.As the rpms increase, velocity increases and the engine starts making power. I get into exhaust technology and stuff like this. Sorry for the sidetrack.

I was referring to the intake side.

a VERY DIFFERENT approach to porting

Reply #21 – March 23, 2012, 11:05:04 PM

Quote from: Shadow;385030

yes, too large of ports will kill the low end.. as for 4V heads, i wouldn't recommend them on a stock bore/compression motor.. on a 10.5:1+ motor with at least .030 taken off the cylinder walls and a considerably high lift/long duration cam, the 4V's will kick a$$ on the track.. that being said, i wouldn't want to drive said motor on the street everyday lol

I agree completely. If you build the out of the bottom end and cam the sh#t out of it, you will have something totally awesome. Not recommended for daily driver.

a VERY DIFFERENT approach to porting

Reply #22 – March 23, 2012, 11:22:56 PM

Quote from: Chrome;385053

I agree completely. If you build the out of the bottom end and cam the sh#t out of it, you will have something totally awesome. Not recommended for daily driver.

no one wants to run race gas on the street everyday LOL.. well, price wise anyway lol i'd love to run race fuel and high boost daily, if the price wasn't through the roof :hick:

a VERY DIFFERENT approach to porting

Reply #23 – March 23, 2012, 11:41:57 PM

I knew that Chrome, but the same theory works on the intake side, velocity is what you want to try and create at low rpm's. I kinda get all over the place, just yakking. LOL

a VERY DIFFERENT approach to porting

Reply #24 – March 24, 2012, 12:11:01 AM

with cams, timing and other things of the sort, you adjust accordingly to build stronger low-end torque, while reaping the benefits of the larger ports above 2krpms

a VERY DIFFERENT approach to porting

Reply #25 – March 24, 2012, 08:42:19 AM

I think the loss of bottom end torque is due to loss of velocity. A port job will straiten the airflow and increase velocity. Funny thing is, this guy is basing all this on motor cycle motors. Although a motor is a motor, with such a small motor, little changes will cause a big effect. His theorys should be looked into, however, we must remember car motors and motorcycle motors have totally different behavior due to size.

a VERY DIFFERENT approach to porting

Reply #26 – March 24, 2012, 10:11:36 AM

Most modern sport bikes have 13-1 compression and run on pump gas. My Yamaha has almost 13/1 comp, while my MV Agusta does. If they could design car engines like that. My 5 valve Yamaha is lacking on low end, but screams mid to upper rpm.

a VERY DIFFERENT approach to porting

Reply #27 – March 24, 2012, 10:17:30 AM

The new Coyote 5.0 has 11.1 compression, but also has variable cam timing and runs on pump gas.

a VERY DIFFERENT approach to porting

Reply #28 – March 24, 2012, 11:13:09 AM

i read SOME of it while laying here, waiting for my pills to kick in.. i can kind of see where his 'adding material' would help, if put in the right place.. IF there was a way to gain the volume somewhere else.. now let me elaborate..

in most windsor heads, when the top of the intake port comes to the valve guide, it bubbles a little more than half way around the guide, then shoots (almost) straight down, probably at a 75-80* angle with little to no 'gradual transition.' it's almost like the flowing air/fuel mix ishiznitting a wall, before being pulled down past the valve.. i'm willing to bet, if there was a smooth, gradual transition there, it would improve flow.. BUT, only if you can make up for the loss of the runner volume on the bottom/side walls of the port

a VERY DIFFERENT approach to porting

Reply #29 – March 30, 2012, 05:11:15 AM

glad to see some nice discussion got rolling. Upon a lot of thought I think a few key points make his ideas possibly work in my head. (keep in mind he says this is all of 4v heads and he doesnt even know if it'll work on 2v heads that we base almost all our opinions and experience on)
The up and down action of the piston leaves room for gases to enter AND exit the cylinder. He refers to his porting's ability to stop this as back pressure but I call it anti-reversion, a principle proven to work on the exhaust side. How much flow is required to fill a cylinder? Ive never read a tech article or seen a formula that can accurately tell me. But the very foundation of making more power is increasing flow and this is realized at high RPM's where the piston is moving its fastest and giving the shorted time span for the cylinder to fill. Its also a point where the engine creates the least amount of vacuum on the intake. The more we raise top end power, the more vacuum we loose on the bottom as well. Right around here is starts getting kind of confusing what we're trying to accomplish exactly. Is FLOW the only thing that matters? Obviously not because top flow sacrifices almost every other bit of efficiency and efficiency translates to power.

Truthfully I figured something out a long time ago that I really hate about engine design. The way to best tune an engine for ultimate performance, is to engineer it to run at one specific RPM. You can tune the intake cross-section, length, 180 degree pulse tuning the exhaust. But it only works best at one specific rpm and fairly well in the near by range. Racing is completely dependent on trying to keep the vehicle in the right gear to utilize that specific range as much as possible. Maybe in all that rush for power, we're forgetting a few things that might be just as important. We know a huge flat torque curve is best. But its a side thought for some reason, maybe we should forget flow and concentrate on producing that perfect torque curve and design our ports to create the curve and our engine internals to raise it as a whole.

Dont get me wrong, I love a strong pull at 3k rpm, or 8k in my yamaha's case. But I'm thinking I've been chasing the wrong dragon. Trust me I've spent ENDLESS hours on a really nice engine simulator i stole online tweaking numbers and producing absolutely sick power out of nothing. I knew almost every dynamic of the 4.6 engine and could have built a far better intake manifold than any manufacturer out there because the number's dont lie. When ford redesigned the 5.0 I was astonished to find they had near cloned my parameter's for 4.6 streetable engine and came out with nearly identical power... So this is getting long, but now that i've seen the ins and outs of tuning the known, I want some CAD-type software I can do variable vacuum airflow with.