Limiting factor for RPMs?

TC · July 11th, 2012 12:37 AM

Originally Posted by OldMachinist

Thanks for finally answering a straight question. Now everyone on here sees how pointless this whole discussion has been.

Pointless probably, informative, very much so.........

And you think this is bad, just wait until we have the Cam Spec thread on this build........

**dieselgeek** · July 11th, 2012 06:30 AM

Originally Posted by TC

Pointless probably, informative, very much so.........

And you think this is bad, just wait until we have the Cam Spec thread on this build........

how about we have more discussion on "this build" when it's done, sometime in the next 3 decades? this thread wasn't informative, this thread was you trying to change your story for 29 pages. You may think it's fun but everyone else here thinks it's stupid.

TC · July 11th, 2012 10:13 AM

Originally Posted by dieselgeek

how about we have more discussion on "this build" when it's done, sometime in the next 3 decades? this thread wasn't informative, this thread was you trying to change your story for 29 pages. You may think it's fun but everyone else here thinks it's stupid.

That is how you see it, but then your a closed minded individual........ But then I wouldn't expect you to understand the type of information I got out of it since you have no experience in engine building..........

**dieselgeek** · July 11th, 2012 10:29 AM

Originally Posted by TC

That is how you see it, but then your a closed minded individual........ But then I wouldn't expect you to understand the type of information I got out of it since you have no experience in engine building..........

Trust me, the vast majority here see this entire thread as a complete and utter waste of time. Entirely your idea.

Experience comes after "success." How about you post up a video of your project cars that feature engines YOU built? As you probably guessed, I don't believe there's a single one. But you could shut me up by posting, instead of what you're "gonna do" what you "already did." Nobody would hassle you when you try to act the expert if you could show something for all this work you claim you did.

So how about it - SHOW US!

TC · July 11th, 2012 10:33 AM

Originally Posted by dieselgeek

Trust me, the vast majority here see this entire thread as a complete and utter waste of time. Entirely your idea.

That is your opinion, others may be smarter.........

**dieselgeek** · July 11th, 2012 10:42 AM

Originally Posted by TC

That is your opinion, others may be smarter.........

Words whose definition TC does not know:

Theory
Fact
Opinion

feel free to add to the list.

Meanwhile, I'd just like you to put up or shut up: show us a running video of a car you "built"

**dieselgeek** · July 11th, 2012 12:20 PM

Crickets chirping. I just discovered how to make Alex shut the hell up - PROOF PLEASE

**The Outsider** · July 11th, 2012 12:58 PM

Originally Posted by OldMachinist

As has been repeatedly proven over the past 100 years, 4-valve engines tend to have drastically more valve curtain area and low-lift flow, relative to bore size.

`Nobody is going to deny the flow advantages of 4-valve heads or the RPM potential of OHC engines with their lighter valvetrain.
There are significant disadvantages though regarding cost ( 2-valve 5.4 engines cost $800 more at the factory level than 5.3 LS engines) complexity and overall dimensions. OHC engines were produced in the 20's or 30's so they must be vintage also. I believe in the KISS principle so if the simpler cheaper and smaller dimensionally engine does the job why change? The hated LS is so much more popular in swaps than the Mod because it is easier to fit. With the LS3's redline at 6600 you would think the 5.8 Mod would redline at 9000 being so superior and lighter in the valvetrain instead of 7100. I suppose if Ford had designed its 4-valve heads with a direct acting camshaft position over the valve instead of rocker arms with hyd. lifters it would RPM higher but that would require more maintenance via buckets with shims or some such arrangement.
According to Chevrolet advertising the ALMS Corvette engine had to be de-tuned to be accepted in its class which explains why its RPM is kept so low. Maybe the 2-valve is still viable in high performance applications

The Chevy "detuning" ad is about the supercharged ZR-1. The ALMS Corvettes are unsupercharged. In other words, advertising slight- of-hand in comparing prunes to raisins. Obviously a relatively big, slow-turning two-valve "obsolete" engine has worked sufficiently well in the intake-restricted world of ALMS. Without the competition equalizers, "Government Motors" would be a distinct disadvantage to more advanced powerplants.

Moreover, there are plenty of series in which pushrod engines are "crutched" or completely protected by the rules, from the three big NHRA pro categories (which ban overhead cams), to NASCAR, to WOO. Thus, there are legions of pro engine builders who know nothing but 2V pushrod mills.

Where DOHC and other forms of valve activation are on an equal footing (no handicaps), DOHC is virtually universal. Even when Penske and Ilmor achieved the last great "clean sheet" pushrod engine triumph (Indianapolis 500 1994) Penske's "Mercedes" had more cubes and more turbo boost than the DOHCs http://www.nytimes.com/1994/04/18/sports/auto-racing-penske-s-engine-has-opponents-singing-brickyard-blues.html

Noone wants this thread to degenerate into another pointless LeSs versus DOHC thread. Suffice it to say that there are a large number of Luddites who will go to their deaths clutching their beloved pushrods and hating on multi-valve DOHC engines. Meanwhile, the vast majority of engines in production today and for the foreseeable future will be multi-valvers. That's not by accident.

Finally, the basics of DOHC design were first penned 100 years ago (not in the the "20s and 30s") by Ernest Henry for Peugeot, who designed a long-stroke 7.6-liter four-cylinder, sixteen-valve DOHC powerplant for Grand Prix racing. Cost has always been the primary knock on DOHC 4-valvers. But in the age of CNC machining, even some of the dirt-cheapest cars in the world use overhead cams and multiple valves for maximum "power density."