Small port heads.

[ozconnection]

I wouldn't have thought a turbo grind would work either...initially.

 

I'm open to suggestions however.  I will pm you Xnke and a call to Isky would be brilliant. If I'm going to this effort, I may as well have explored all my camshaft options. Thank you again for your help and assistance.

 

Ideally, my head should be 'shipped' over so that a custom grind could be researched and developed...who has that sort of time and money? Donations are most welcome lol

[Tony D]

I need to set up a Magic Jack and send it to you with a five year subscription!

Edited May 26, 2013 by Tony D

[260DET]

You Sydney blokes could do a lot worse than have a look here http://www.viczcar.com/forum/index.php/board,12.0.html and particularly at Peter Mc's topics. He is basically banned from this forum. There are a couple of Sydney L6 specialists around too, both are involved in racing, I forget their names. I'm not a L6 person but check this video where my 420whp can't make a clean pass on a Sydney built L6 that absolutely blasts, the red S30

[PMC raceengines]

All the cams you could want are hear in aus , and there is 4 full time Datsun engine shops you can deal with to make shore you get the right cam , in fact if you send me the head  i will flow it and give you a cam, that will do want you want . and will set it up so you can just bolt it on .

[ozconnection]

All the cams you could want are hear in aus , and there is 4 full time Datsun engine shops you can deal with to make shore you get the right cam , in fact if you send me the head  i will flow it and give you a cam, that will do want you want . and will set it up so you can just bolt it on .

That's fantastic Peter! Based on what I've seen of your work with L's, you're the man! I'll talk to you soon and we can discuss my options. Cheers!

[bobafeets]

First. LOVE THIS THREAD! You guys made me happy knowing I can get a bunch more torque out of this sweet motor. 
Second. Found this cool site for people that follows this idea! http://www.superchevy.com/technical/engines_drivetrain/cams_heads_valvetrain/sucp_0902_chevy_engine_port_variations_measuring/viewall.html



Enjoy
 

[ozconnection]

First. LOVE THIS THREAD! You guys made me happy knowing I can get a bunch more torque out of this sweet motor. 

Second. Found this cool site for people that follows this idea! http://www.superchevy.com/technical/engines_drivetrain/cams_heads_valvetrain/sucp_0902_chevy_engine_port_variations_measuring/viewall.html

 

 

 

Enjoy

 

That's a cool article and short of performing the same sort experiments they did with the Chev heads etc, I would be happy to suggest the same trends apply to the L6's.

There's no doubt in my mind that the little Y70 head had done good things to my torque band at lower (less than, say, 4k) rpms compared to the L28 N42/N42 combo it replaced and I subsequently raced against in my friends 330 Cedric (manual shift) Wagon. The concept or idea that you can tune your engine with port size is therefore something not to be overlooked or forgotten about when building a street motor. The article even goes so far to claim that 'too big a port size' will drop power (even when top end power is a priority as in race spec). I've always known that once a port was too big, the only option was to remove the head. Most people just wouldn't do that though. They've spent the money and were assured that the big ports were needed to get to the level of performance they were after. With a small port head, you can be confident that you'll get the best low rpm torque possible and that with a suitably spec'ed camshaft, you'll still keep a decent top end. Considering that on the street, most of your driving is with the engine turning at rpm's less than 4k, response in this range is paramount. Full throttle, max rpm 'stabs' are few on a daily driver. It makes no sense to be fixated on this.

Too bad the article didn't explore using different cams but that would've been a truely mammoth undertaking. I'd sure as hell be interested in those results because the small port theory that I was pondering has already been confirmed by others. However, designing camshafts to take advantage of the smaller ports higher velocity would be a very interesting project indeed.

The search for 'that' cam continues...

Cheers

Edited June 8, 2013 by ozconnection

[Xnke]

The problem with this line of thinking is that even though you are running a small port, and thus have high port velocity, you are neglecting to do the math to figure out what this size port can actually flow. I have no doubt the engine feels torquey down low-I'm sure it does!

But does it really make more torque, or is the power band just flat over 4K?

 

Here's my reasoning:

 

a 30mm port, with the small intake valve, certainly has high velocity...which will promote cylinder filling up to a point. But, that same 30mm port will not flow the same amount of air that a larger diameter port can move at the same pressure differential.

 

The velocities in question are in the 200-300FPS range, once you get over about 275ft/second port velocity, power AND torque will start to fall. By 300ft/s, you'll really notice the hit.

 

In an Ideal port, you would get all the flow you could get out of that port while maintaining a port velocity of about 240-250ft/s. If port velocity never gets to about 190-200ft/s, the engine tends to be soggy and flat...feels like a torqueless wonder. If your port velocity is over 275-300ft/s, you will feel a big rush of torque below this point, but once you get through the ideal range, torque will fall off quickly as the port starts to run into a choked flow region. It's not true choked flow, but that's the best wording I can think of to convey the thought here.

 

In this case, a 30mm port is not QUITE too small...but smaller than optimum. You are going to hit true choked flow (the kind of choked flow that relates to sonic velocity) around 6000RPM, with a 38mm intake valve and a 0.490 lift cam.

[ozconnection]

The summary here on port velocities is interesting and I have no reason to doubt what you're saying Xnke. Indeed, my ports will run out of flow once gas speed approaches V.Max but this phenomenon isnt happening at silly low rpms, at 6000rpm, I'm looking for the next gear anyway.

 

If we look at cfm figures for the small port heads, the intakes flowing about 120cfm, and not allowing for percentage volumetric efficiency losses (100%) on the intake side of things were flowing 720cfm. Thats Holley 4 barrel territory. If we work with 80% VE, then we flow 576cfm. If this is what the engine can flow taking into account flow and  induction restrictions, then its not the ports that are restrictive but the rest of the induction system that's not optimised. (I'm talking Arizona Z car/Clifford four barrel dual/single plane type manifolds here guys, NOT IR intakes!) 

 

This is probably why almost nobody uses these manifolds for racing, they can't flow what is needed to get the power that is seen with IR induction setups. There are other reasons too but that's a discussion for another time.

 

It's a flow thing... The intake port/valve combination is only part of the induction system. Do I need bigger ports/valves when the rest of the induction system can't seem to match the flow potential of the head? Whats the point in putting more effort in the head then? Regardless, the small ports seem to do the job at the desired rpm ranges it most commonly sees. (I might add that during my drag run with Dave, I was hitting the rev limiter in second at 6250rpm. It wasn't a wall there either, just it was time to shift because I'd hit the limiter on my MSD.)

 

In a few weeks, Dave and I are attending a Club day on a local chassis dyno. I can't wait to post those figures up so we can compare the two graphs to see what's happening where through our different engine and driveline combo's.

 

Cheers.

 

 

 

 

 

 

[Tony D]

An L28 Cam has you power-peaked at 5,500... So a velocity peak at 6,000 is a problem how, again?

Most turbo cams are " bolt in " meaning power is maximised below 6,500, and the gearing on most L28 cars had top speed occurring at 5,300 rpms...

 

So....

 

Theory being theory, it has a bench racing aspect to it... But in practical application on cars designed around torque, geared that way, and driven that way, what you realize is you GAIN power/torque on the bottom end of the rev range, while in all practical terms lose nothing off the upper rev range which traditionally is the zone of lightweight racing vehicles...but make for a miserable drive in a larger Saloon car!

 

I drove a few hot Cedrics in Japan...really a strange feeling...unless you ran a 5.60 gear set the car didn't move off the mark quickly at all, and you had to,twist the engine above 3,500 continually to get middling performance with no appreciable increase In Top speed. The same car a year later with a Turbocharged car, 4.11 gear set, and shift points 2,000 rpms lower was a LOT mor driveable.

 

"Strangled" engines with high port velocity and small carbs have traditionally been an automaker's offering when a market didn't support huge V8's. torque peak elevated somewhat through cam work and gearing for midrange , and good cylinder filling to wake it up off-idle. Sure, top end suffers ultimately, but the in-town practical application of the car...where you spend 85%+ of your driving time is greatly improved.

 

I think this is the root of this exercise.

[260DET]

James Flett is the bloke in Sydney who will build you a top motor. He did a drive in drive out job on that red S30 in my video, AU$17k including new carbs, clutch and a track day test and tune. Him or Peter Mac, now that finally some Datsun owners are prepared to spend euro type money we are seeing the benefits.

[ozconnection]

Yes Richard, these guys have a good reputation. Getting the head developed the way I want it is only just a question of money...better start saving!

[Tony D]

It always only ever was!

 

LOL

[bobafeets]

I saw this book on android market. It is called "Engine Airflow HP1537" reading the sample and it is amazing. This should answer all the questions. Check it out.

[260DET]

Yes Richard, these guys have a good reputation. Getting the head developed the way I want it is only just a question of money...better start saving!

 

Yep, I'm a tightarse but really with some things you pay the money and you pay it just once. AU looks retarded for only now 'discovering' L6 power potential but, unlike the US, there was no incentive for the guns to look at the L6. Until now.

[ozconnection]

I was forever telling my mates years ago that "In America, the L series engine..." 

 

Now I can say, "In Australia, we can build..." thanks to people like Peter and co who are finally pushing the boundaries for us 'down under'

 

About time.

[Tony D]

1989 N/A 10 second ZX's... Carboy L-Engine Shootout...

 

We're all retarded, it's just a matter of degrees!

 

"Eeeeyaaaahoooou!"

[ozconnection]

Some more than others, it seems.   LOL

[Tony D]

And Dude, I believe the currently accepted term is "Special"...

You're being very un-Dude, Dude!

Edited June 26, 2013 by Tony D

[ozconnection]

 

We're all retarded, it's just a matter of degrees!

 

 

LOL, but you said retarded Mr D.

 

"Special" is an entirely different thing...DUDE! LOL