Think what ya want,ya will anyway.

 

dude, your not saying he should limit lift because the head don't flow anymore if he lifts it higher?

Bret

 

No but if ya go buy max flow like I always do--So does Crower-- with lift it would be around.400/.450 lift

That's a tiny cam lobe with 1.5 rockers.

 

Grammerman/Michael needs to chill out.... you might want to take the same advice. You've posted up all this about porting your own heads and your not making a ton of headway here.... the best thing you could do if you want to learn this is go to SAM to get the basics.

Larry you need to do some research on curtain area and the formulas for finding max lift for a application. It has to do with Mach numbers so i'm not going to get into it, but EVERYTIME I use that it will tell me exactly where my HP peak will be with a good port, so I've come to believe it. Going by max flow is a little TOO old school for me, and it doesn't work when you look at the rules of physics. .450" lift is about enough to get a stock LT1 to peak HP around 5000rpm. Right about where the stock valve, stock lift and stock HP peak is. Seriously do YOURSELF a favor and do some reading on that, it will really get you where you need to be in that department quickly.

Bret

 

Bret, if you're going to continue the engine dynamics/physics discussion then how about jump back to post #9 in this thread. This is stuff that rarely gets discussed and could use a little coverage. Particularly the port design for high manifold vacuum power.

As for chilling out, I've seen you get riled up a time or two when people jump on your case and especially when they criticize your work in a manner that you think is unfair. There are absurdities being passed off here as experienced, logical criticism and I'm kind of tired of it. My goal was never to hit a 280cc peak flow target. Let's hear what you have to say on this since I'm not making any headway. I laid out the best analysis I could think of between my ports and some of the pro ported stuff rather than just lumping ported heads of any volume together. Clear things up since you're the site expert.


I'll say it again, for optimizing part throttle response with reasonable top end pull I think my heads will work excellent. My experience has shown that a small CSA port with moderate to low volume works best for part throttle power and response so this is what I went with. If you have a convincing argument that says otherwise I'm interested, but I'm working off of considerable empirical data so theory alone isn't going to get it done.

1racerdude, that is a real sportsmanlike approach. Sure, lets race my $3500 small cammed daily driver against your $10,000 huge cammed race motor. What about we come up with something "fair" that's based on your own words. You run the strange parts list you're on record as saying would outperform mine. That would be a stock set of LT1 heads and one of your custom .400 to .450 lift cams (with similar duration to mine to give me at least a small chance). I'll race you for pinks and I'm dead serious. Put up or go away.

 

Everybody needs to show some respect. We don't need people here who cannot act like grown-ups.

Michael, If you cannot get your point across without being insulting, leave.

 

Michael,

"Do you think that mid/low lift flow are of little importance when part throttle power is of high importance to the end user? What about port volume as it relates to part throttle power?"

No mid and low lift flow I don't think matter in high vacuum conditions at all, the port is not being sucked on at it's maximum so it doesn't matter since you aren't using the ports maximum ability. One reason that a stock motor at 5% throttle opening can make the same TQ curve as a well done max effort street motor in the same displacement range.

As for the cross sectional areas effect, yes the smaller the better since its going to be hard for you to keep the velocity up to a decent level with such low volumes moving thru the port compared to what it SHOULD be designed for in a performance situation, and that's WOT.

You size the port for what's going on at WOT, not part throttle unless that's all you care about. Even then some OEM designs don't do that.

You really need to look at other applications out there, small highly effective head ports with a 23° valve angle are hard to find. Super Stock heads would fit that though since they have a volume limit. The problem is they are extremely expensive and the best guys in the country are the only ones who master them, Larry Meaux is a good example. His stock valve size, 160-170ish cc volume port that moves almost 260cfm is an extemely good example, so much so that it puts a 3200lbs '68 example in the high 9's and the SS/HA class record.

If you want to learn how to do this better, read a lot from good head porters, get a flowbench and pitot tube and start learning where taking out head flow is going to help you make more power, not just flow.

Bret

 

Grammer, as you have been told before(but for some reason you didnt listen) head porting IS a black art..the reason, SO MUCH INFO AND LEARNING INVOLVED. It's kinda like wet sanding and buffing a fresh black paint job you just paid $2500 for...would you break out the sandpaper and sidegrinder with a buffing pad on it? I wouldn't, I would PAY the old guy who has ALREADY trashed his fair share of paint jobs to KNOW what NOT to do.

No one builds engine packages for part throttle torque and response, oh wait, well yes their is.....when the car come STOCK it is designed for the balance between part throttle and wot, and they spent millions getting it right.


I had about $875 in the last set of LT1 heads I had, they flowed 260 CFM, made about 380rwhp with a 224/228 on a 114 cam(90 mph in the 1/8 in a 3700lb car) with a home ported intake, 1 5/8 shorty headers and a mail order tune. In the summer.

#1 Save up, send the heads off, have a fast car, be happy.

OR

#2Do as Bret said, buy a flow bench, the correct tools, and a probe. Learn the trade.

MUCH cheaper to do#1


BTW Pops gave up 10 lengths and a "bulb"(.5 seconds) dont think its a fair race? Your part throttle responsive heads will not come into play here.

David

 

That "old guy" was a Mark Twain fan, unless you are VERY old and knew Sam Clemens personally.


"It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt."

Mark Twain
US humorist, novelist, short story author, & wit (1835 - 1910)

 

I am a BIG fan of Mark Twain. He could make more sense in one sentence than most could make in a book and come right to the point.

 

Bret,
I understand the curtain action thing and the valve in the air flow.
I also understand that is not the most practical for anything but a trailer queen. Ya don't (I do) run that type of lift on a customers street engine unless ya got very small valves to keep the lift within reason for guide and spring wear. Most don't want to change springs ever 1000 or so miles.
I do and will use a few thousands(.050-.075) over MAX flow for the cut off point for lift. I do expect MAX flow to appear on a flow sheet somewhere upwards of .500 though. I also get acceptable wear by doing it and some pretty dam good running engines.
As ya know ya can help small lift with duration and valve timing events.

 

I tried to edit out the flames, but this thread got out of control.