Who wants in on this?

I feel the more educated you are, the better decisions you can make as a consumer and the more involved you can be with the parts that make you go fast.

While I dont profess to be, or dont want to become any kind of guru, I have been doing some research on cylinder head porting, mainly.

I'll post up a couple articles I've ran across and post a few pertinent question for someone smarter and more experienced than me to answer.

1.) How does the valve job affect flow, port velocity, and power output on a cylinder head?

I present for discussion a good article I ran across that mentions Advanced Induction regarding their Newen machine and its capabilities in regard to advanced valve angle designs, and the power that can be had as a result. Read it!

http://www.stockcarracing.com/techar...c_cutting.html



Valve Seat Power
"Part of the seat design involves the form on the valve. A 30-degree back cut, such as the one between the 45-degree seat and the back face of the valve, is essential to strong low-lift flow."




Valve Seat Power
"Many classes call for unported heads, so you could be starting with a production casting (shown) or an aftermarket equivalent. The only avenue open to modification is the valve seats, and how they are cut can be a deciding factor in overall engine performance"



Valve Seat Power
"This mean flow velocity test on a stock high-performance Chevy head shows the significance of the valve seat's role toward flow is higher than the port's up to the circled area (0.390 inch lift). This establishes that the seat's role in overall airflow is higher than generally believed."



Valve Seat Power
"AFR's heads are noted for their good seat science, whether it be on as-cast heads or CNC heads (shown). The radius on the exhaust is an important part of the equation toward allowing this production-style exhaust port to flow an outstanding 240 cfm at 0.700-inch lift. "



Valve Seat Power
"Here is a Newen CNC-machine-generated seat form that proved effective on a production-style head. The top cut (green) is at 37 degrees by 0.020 inch wide. The seat (red) is 45 degrees and 0.060 inch wide. The form below this (yellow) is a radius that joins the seat at 50 degrees and ends at 80 degrees. The blue section is an 80-degree cut that blends into the port. "


And here's a video where West Coast Cylinder Head shop owner Richard is interviewed by Tom Nelson of Nelson Racing Engines. WCCH does all the head work for NRE, and if you know anything about NRE you know they make stupid power, while still promoting reliability and streetability. The vid showcases their work witht he L92 / LS3 cylinder heads, but the principles still apply for us.

http://www.youtube.com/watch?v=YgEKv...eature=related

(The talk related to valve jobs starts at the 5:00 mark in the video)

Above is part 2 of the interview, here is part 1:

http://www.youtube.com/watch?v=xumwF...eature=related


I've got more questions but maybe this one will keep us busy for a while.

Discuss.

 

All I know is I don't have the brain power to counterpoint anything stated from those who deal with this for a living and have been known to produce excellent results.

 

I DO know there is huge power in the correct valve job. There are many many theories on this.

Stock classes have gotten this down to a science, where porting is not allowed.

I think its most affected as the valve is first cracked open, when the valve is shrouding flow the most.

I also think the correct valve job is not an across the board kinda deal. It is more application specific.


One of my questions is, after the valve job is done, how long does the increased flow last? The seats change as the car is run over time.

I have also learned that porting the bowl is where the most flow gain is, most think its the pinch area that slows flow down. In 80% of cases its not.

 

i believe the valvejob also has a big impact of valve timing, especially in induction limited classes (Stock). maybe gizmo could chime in on that though

 

A correction - we run only the highest end equipment produced today, and this separates us from most. While we have at one point or another owned several different seat and guide machines, rest assured we do not utilize a Sunnen VGS to cut valve jobs.

Vizard is a local, as nice as can be, and a handful of us try to help him out by occasionally giving him access to equipment he wouldn't otherwise be around so he has subject matter for articles to write/sell. Keep in mind that when the product is media for enthusiasts, the content is specifically geared towards holding your interest - not educating. Wish some of you guys could spend a little time with vizard; we rarely talk about cylinder heads & he's hilarious. Next time we have time for him to swing by maybe I should get him a webcam and a mic.

Regarding your discussion, I would posit that part of the 'issue' is that everyone keeps asking for "the secret." Is it a magic flow number, a magic valve job, etc. which is somewhat amusing since these are largely side effects of a design and not a design in and of themselves. You are paying for machine work. If you purchase machine work on the usual Sunnen seat and guide machine, or the superior Serdi style machine, it will still not be comparable to our machine work on a CNC Newen seat and guide machine. It isn't flow #'s, it is tolerances and attention to detail. Naturally, this all assumes a 'competitive' passage design in the first place and there will obviously be an exponential difference in the price of admission. A cheap valve job on entry level equipment may start at $100-150, where higher quality work on better machines starts around $250 and can exceed $1k depending on the application.

A high quality valve job that is 'in the ballpark' regarding size/angles/transitions is going to be competitive with, or best, the valve job handed down from the heavens and machined on entry level equipment. However, if the rest of the system isn't also appropriately machined/altered then neither will produce the best result available. This excludes the human variable. There have been examples of horrific work cut on the best machine around, the Newen, that was clearly the result of operator error. In the end, if you want the best valve job, you first need to seek out those with the best equipment. Then, pare those choices down by comparing their pedigree, etc.

I understand and agree that it is important to research and make informed decisions. However, for the consumer, attempting detailed discussions about esoteric details is not typically fruitful. A great many are behind the curve precisely because rather than listen to one proven individual they "educate" themselves from unqualified sources. I can't tell you how funny it is when people call up wanting to discuss intricate details when they haven't the most base understanding of the function or production of the work in the first place. Along the same vein, I'm sure there are threads on webMD etc. where people, qualified and unqualified, all postulate and theorize on medicine. It simply isn't something you are likely to form a useful understanding of by reading an article on the internet. In the end, like it or not, the correct answer all along is "find the best doctor you can afford and focus on what he says to do." Some may take that the wrong way, but it is obviously the safest policy in regards to deciding how to spend your $.

Keep in mind, this isn't to say I don't think it should be a discussion online, or that you shouldn't attempt to learn something about the intricacies of what "cylinder head work" is comprised of. Only to say that to assume any one aspect or area is so critical that you can focus on that to the exclusion of the rest of the system is clearly false. In over simplifying and excluding the majority of variables at play, guys tend to negate the usefulness of any conclusion they may conjure up. It is the proper management of all of the variables at play that will get you where you want to be.

Hope the more philosopical take on this helps more than it hurts.

Take Care

 

Thanks for chiming in AI, I was actually going to email you this link.


Dont misunderstand, I have no illusions of becoming a cylinder head expert overnight simply because of an online discussion.

I have no desire to try and find out the "secret" to "head work" and take my ideas to the local shop and have them experiment on my dime. Wouldnt even do that if I had money to burn.

I've long been an advocate of observing race-winning combos and emulating them for the best success. Thats the main reason I've been in touch with you about porting my heads and we will be moving forward as soon as funds allow (which will be soon).

I however tire of the "what spark plugs are best" and "should I run lomg tubes" topics on here and elsewhere and thought some more challenging discussion to stimulate the brain would be nice.

Sure we'll make mistakes, misinterpret data, buy into marketing claims, misuse nomenclature, etc. Afterall we are just a bunch of enthusiast and backyard warriors.

But if someone learns how to make more informed decisions, and to appreciate the intricate details when they DO see good work, then we all might be a little bit faster.

One could also easily see how discussion of this nature could benefit your company. Being the way to arrive at these intricate valve jobs(which I realize is just PART of a good cylinder head rework) is the advanced equipment and techniques you have...

If someone calls up xyz head porting shop and says "what kind of valve job do I get" and the shop says that they offer a good old 3-angle that their pappy first taught them on a 1938 briggs & stratton lawnmower, now they know theres more to be had than that.

I mean how many LT owners ever even consider how important a valve job is and that it is "one" key to obtaining above-par results?

While I understand your metaphor about finding the best dr and letting him do his thing. You guys also know that just like a CNC. You get out what you put in. It duplicates exactly what you tell it to very consistently. So if you put in a **** design, it will duplicate it as **** over and over.

One reason I like to be leary of cookie-cutter setups you read about on the internet.

Not saying this applies to you guys at all, certainly your results would indicate otherwise.

Maybe you guys could share a little on your thoughts behind the valve job. Not just the accuracy of the machining tolerances, but the actual design of the valve job and how it affects the performance of your work.

Understand, I'm not prying for info. You will be getting my business either way. Just that to some, they "why" and "how" really does matter. It would also help illustrate the difference, and perhaps superiority, over your competitors.

I also apologize, I knew you guys used Newen equipment on the valve job (as stated on your site), not a Sunnen.

Greg

 

I would really like to see some more on this. I'm taking an engine rebuilding class at a local technical school two nights a week. Last night the "teacher" taught us how to do valve jobs. He was pretty unclear on even a three angle valve-job. Needless to say I have a passion for the science, precision and the quality of good headwork. I'm not getting any useful information out of my "teacher". I wish my GI Bill would cover S.A.M. because I'd be on the first plane to Texas getting a real education in performance. TIA

 

I have to agree with Ai on this one. Most guys don't understand basic engine principles much less advanced head flow characteristics. Most guys want to spec there own cams when they don't know enough to make an educated decision and take an educated guess. i have been wrenching on cars for 20yrs and built plenty street/race engines but when it comes to portwork, machining, matching cams, I leave it to the people who do that work for a living. LOL If I were to order a heads/cam setup from Ai, I would give them all my info like gears, rpm range, Cubic inch, compression ratio, goals for HP and let them pickout the parts and services needed, then send the money. Now you should recieve a proven combination of parts that work together without problems. I deal with Lloyd and he does the work, chooses the cam and I pay. My car runs well and I am happy. The end.

 

Good for you. Theres no harm in discussing things more than "flow #'s at X lift" though.

I think you guys who chastise us for wanting to discuss this topic are misinterpreting what we are trying to accomplish. I have no interest in porting my own heads, or stealing anyones "secrets".

I just like knowing what seperates a good performing cylinder head from a backyard machine shop "port polish and 3 angle valve job".

Theres no harm in being an informed consumer. Its not enough for me to know THAT something works, I want to know WHY it works.

As I said before this would be a perfect opportunity for companies like AI to illustrate why their methods are superior, but apparently they dont see it that way.

 

You're asking the wrong person the question. The average valve job to make your grocery getter go down the road bears no relation to anything having to do with performance. Unfortunately, all you'll learn in a normal tech school is how to do that 'average' valve job. In other words, if it runs and the valves don't leak, you're all done.

 

Read this article from Car Craft. I think it sheds some light on your questions and even has photos and flow number comparisons.

http://www.carcraft.com/techarticles...gle/index.html

I just had my motor done and went with larger Manley RaceFlo valves (smaller necks) and 30 degree back cut on the valves with 1.6 rockers. Minimal expense and possible significant increase in flow. Everyone always puts in big cams to get airflow and often overlook these items which also get more air into the cyclinder without significantly effecting driveability. I wanted my car to sound stock mostly but wanted to get the valve off the seat quickly and flow as much as possible over its full range of opening so I wanted to maximize overall flow throughtout the range of travel of the valve. Whether it made any difference we'll find out once I get it on a dyno.

 

I apologize for just jumpin in here, (i'm new), but I would like to recommend "Internal Combustion Engine Fundamentals" by John B. Heywood.

He discusses everything you want to know and more including chemistry of fuels, flows, designs of parts and pieces, and the math behind "why you back-cut the valves at the angles you do." Some of the math equations in the book run out of our typical 26 letters we have in english and then goes through a bunch of greek letters too with integration and stuff. If you can follow what he says, you will be ahead of the game.

Good luck!

~JJ

 

Hey, awesome post Greg. This is the kind of stuff that I love reading, because I think there are discussions on CAI and headers, and than there is this kind of stuff. I am looking forward to reading more. Keep this stuff coming!

 

Thanks Jenn, and thanks JJ. Ill be ordering it !

 

From my practical experience point of view, there are plenty of ways to screw up a valve job so that valves quickly sink into the heads and send your lash all to hell. Maybe not the end of the world on a hydraulic lash adjustment system with adjustable rockers but, on a solid lifter system with a fixed range of shims available, this really sucks.

Fuel selection also plays a role in what you can get away with on a valve job. Leaded race gas is very forgiving, unleaded is brutal and alcohol (yes E85 too) is flat out devastating.

 

gregrob, thax for bringing up this thread. its about time since we had a good informative thread in here to discuss...Subscribing
anyway,,i dont believe in such things as ‘cylinder heads secrets’ actually its all known by the pros and by those who do it for a living. I believe its all about who does it better and perfects it. I ve read several books related to cylinder heads performance and stuff, and they all verify the same basic ideas when it comes to modifying cylinder heads.

 

To the OP, Speedtalk forums have an insane amount of porting/valve jobs/cylinder head tech.

I know that a Serdis or CNC machine is top of the line but the best shop in my area uses a Sunnen. They also don't rush their work, which I believe is why their work is very good. Also checking on their SF-1020 seems to confirm it.

I know people on here talk about 3-5 or more angles on the seat, however I've notice a lot of the times they cut radius valve seats. Don't know what is better but I'm sure it is like anything else with advantages and disadvantages.

Thanks for posting in the thread.