There is so much information available through resellers, OEM's, people, friends, etc. on "the best" cylinder heads that one can't help but feel overwhelmed and confused because nobody's account really confirms somebody elses account. How does one objectively compare these, this is opposite of subjectivley. Some subjective evaluation examples are: great "race" head, lots of power on a 402, my grandma ran a 10.37 sec pass at the track this weekend with them...and the list goes on and on).

Since it is not likley for anyone to take every variable of an engine and dyno test every combo (cams, heads, intakes, exhausts, etc.) how can head performance be quantified. Common data available is, intake flow rate, flow pressures, exaust flow rate, runner volumes, valve sizes. Is it possible to compare apples to apples when you really have an apple, two oranges and a watermellon? Maybe some sort of relationship between instantainious flow rate and cross sectional area? Anything available short of a full blown CFD analysis?

 

CFD doesn't even tell you anything... a good cylinder head porter can tell you between head a and head b which one is better after some measuring of the port and some time on the flow bench.

Your next example is back to back tests on a dyno with only changing the heads, that means the same valvesprings and compression as well to make them 100% equal. Then if one doesn't shine well over another one, the track is the last and final place to go.

Bret

 

well.. from my experience with heads

it all starts off with what kind of gas you want to run in it first

 

I have a hard time because it seems flow numbers do not equal horsepower. Just lurk through the threads and see what kind of power people are making with what and make your own objective decision. That's the best method I've come up thus far, and all that has netted me is indecision on what heads to put on my 408...

 

i understand what hes asking, and i understand what you guys are saying...but is there a way to look at certain numbers from the heads an "deciphur" those into a language that the simpler minds such as myself can figure out? i can figure out my dcr with a certain combination of parts, and i can figure out my valve events (although im still learning how to interpret them as what characteristics they will give my motor), but with all the different heads out there, how do you decide whats best for you?

for example; brand x has a stage 8 head, and brand y has a comparable head. both are very similar, yet both have their own unique features...what do you look at that tells you how they will affect the characteristics of YOUR particular setup? ive seen the thoeries behind why certain individuals design a cam a certain way, but what should i look at in my decision on heads to make the most out of setting up my motor to do what i want it to do? a good example off the top of my head: Patrick G had a cam ground to make more torque down low. he also chose a set of heads for certain reasons...what features in a set of heads should i look at to help me make a decision?

i hope my questions make sense, im just trying to pull from the wealth of knowledge i see around here.

squealingtires - sorry for the hijack, seemed lik an appropriate thread to ask in...

 

Umm...are you sure (perhaps you are considering every aspect of internal combustion engine theory). With a CFD package one could apply the Navier-Stokes equations and set up the geometry as well as the boundary conditions for any port geometry and engine conditions. Would I? Well no; I lack the time and experience with with the software to be able to simulate all of the conditions correctly (it is not a steady state problem of flow though a round pipe, but rather, it is very complex (transient solution, heat transfer considerations, combustion analysis(not CFD), exhaust flow, scavenging, etc.)

Wolfy--you interpreted my post correctly. I just want a better way of comparing cylinder heads. I want to filter all the information that is available and make some engineering generalizations from the commonly available data for cylinder heads.

1.) Trying every head on my car until I arrive at my goal. That's crazy and $$$
2.) CFD - only the OEM's can afford that kind of research. Out of the question
3.) Pick something similar to what someone else has (maybe the most reasonable method), but I can't help to think about all of the money that has been wasted by people who fork over top dollar for high end parts capable of making 800hp and their goal was to only make 500hp. get my point. I wouldn't want to waste money on a set of $2500 heads if I could get the 90% solution with a $400 CNC job on my existing heads.

keep the comments coming

 

Navier-Stokes equation you must be an engineer! You do not see that or boundary layers talked about by the average person. I am a Chemical Engineer so I no a little about flow. I just keep my mouth shut most of the time.

 

Combination, 1st and last. You must compare apples to apples like you said.

I would never try to use my profilers off the Pro-Mod engine on a DD.

I would never try to use old truck oval ports from a tow vehicle on my Pro-Mod.

If I get what your asking, there is only a handfull of heads that work with each combo.

It is much easier to compare 5-6 heads than 78. Figure out exactly what you want, drag, DD, street/strip ect ect then you job picking a head is much easier.

I agree with the idea, but I don't think a simple formula will ever balance the difference between intake volume, int flow, ext flow, runner length, ect ect with each company. Especially once you take a grinder to something. It would be great if there was a single simple scale to use. The companies would find a way to fudge the results, I'm sure. Like flow numbers with 25 instead of 28. Using a 4.6 bore instead of the 4.35 the head will be used on ect ect.

What is wrong with using a tried and tested combo, let them pay for all the testing, and you get 500, 600, 1500 HP you wanted and for the least money.

Sorry if I'm missing it.

We have checked many websites for info on crate motors, and have had buddies use their ideas and built their own versions with great results. Good luck all.

 

6 heads with 3 different CNC options each. So 18 heads lets say average about $1600 each is a lot pile of money. Trial and error is expensive and not for the daily driver crowd. I'm trying push this notion of trial and error aside for people who want to know what it takes to reach their goals at a minimal cost (meaning: don't buy more than you need). For an extreme example; lets say I build a 400hp engine and spent $10 grand on it but why, when I could have built another 400hp engine for $4k. How about somebody spending money on forged pistons with the intent of never using nitrous. Get my point a little better.


I realize that there is no such thing as an apples to apples comparison between parts with some sort of analytical "model". What I'm really struggling to grasp is some sort of trend that can be studied within head performance perameters. These trends would be used to compare 2 given heads.

This is what everybody blindly (blind is too strong of a word, maybe slightly blindly is a better combination of words because of the qualitative information that can be extracted) uses to quantify the performance of parts. Most people don't pony up the cash all at once to buy a crate engine. They might say something like these heads supported xxx horsepower on xxx platform. But outside of that specific platform which it was tested, tune, engine, cam, intake, etc they can only guess whether the performance on a different platform will be higher or lower.

So back to heads, could we start with generized statements about some of the accepted factors that affect performance and then build/trim/modify them as testing has shown.

Maybe something like:
Overall head performances is increased by increasing the volumetric flow rate of the incoming air charge while reducing the runner volume.

Keep in mind there are always exceptions to the rule.

Keep 'em coming

 

i agree that combination is everything. and i understand that you wouldnt use certain heads on certain combos, it just wouldnt be the most efficient way to make the power you want the way you want...

and comparing 5-6 heads IS easier than comparing 78, but what im trying to figure out is the best way to compare those for the intended purposes of MY combination; to make the most efficient power for what i want my combination to do.

the example i come back to is Patrick G. he wanted to achieve certain goals for his combo, so he optimized his setup on paper before he went out and spent alot of money on a setup. he designed his cam a certain way to reach his goal of more tq down low and still keep the top end, basically to keep the power he had on top end, but optimize it to make a better/more fun daily driver. i nderstand why certain individuals design a cam for theyre setup, but i dont understand how to chose a set of heads. i guess maybe im looking for a general guide, ie. flow #'s in x range do this for your power band vs flow #'s in y range, porting a inatke a certain way produces this result vs porting another way...does that make sense? in all honesty, im looking for a way to compare apples to apples. the best way way for the average guy to chose between 5-6 sets of heads is to compare bits and peices of them until he finds a set that meets his needs/goals. if you break the heads down into catagories (flow numbers thru the range, cc's, port designs, porting methods, etc.) and be able to understand what characteristics each catagory gives a motor...

the problem with the "tried and tested combos" is they arent for everyone. what some people call a good daily driver cam isnt what other people will consider the same. and not all setups are optimized...there is a guy here running an ms3, with tsp stge 2.5 heads and all supporting bolt ons. that setup was recommended by tsp. what kind of power should he make? 400 rwhp? 425? 450? i know what he makes, and ive got a good idea what it should make. i want to optimize my setup to make it perform EXACTLY the way i want it to. you cant really do that with an off the shelf combo. they all have issues that i have to "compromise" with...if i can maximise the setup i choose, my compromises wont be as big...

 

ttt for me waiting for an answer...

 

My comment about tested combo's was meant for professional engine shops crate motors. I know very very few guys I would trust to design an engine for me. Schmidt, R M, ect I would trust. Not joe bob from the track I talked to twice. Plus Schmidt probably did try several heads per size & power level he wanted to make.

I would never try to judge tiny differences in heads, cnc programs ect. I would try to make the most informed judgement and live with my decision. Yes, I'm sure you could drive yourself nuts thinking I wish I had changed this a little. Like it was said, it is way too expensive to buy 18 heads, 18 cams, 18 carbs, 18 intakes ect.

One day you have to pull the trigger and live with what you decided.

I still wish there was a simple formula with a scale that would give us a perfect answer for every option we are trying to design. Sorry there is no perfect answer. There is no way me or most of the guys here are smart enough to know every combo possible for every engine make, model, size ect.

I still say if you know exactly what you want and how you will use it, a tested combo is the cheapest way to go. Yes, adding some changes is the intelligent way to get exactly what you want, for the least money. I don't like internal oil pumps. Yes, my cars are now set up for dry sumps, so it's not that big of deal for me. Some cars just don't have the room. I also like tunnel rams to make my scoop more stable, besides the free HP you get with it. There are reasons for and against every option we try. There is nothing wrong with borrowing info from someone you trust, when making a decision.

I personally still think the only answer any of us can be sure of is it's all in the combination. I just never see a way to make a scale or a rating system.

Good luck everyone, great thread.

 

I'm encouraged that I'm discovering "the secret" in engine head selection from experienced professionals, however I'm disappointed that "the secret" I've been seeking is nothing more than an educated guessing game based upon experience. I was convinced that there was something that could be drawn up in conclusion. I was hoping for some sort of physical/mathematical/geometric correlation between the data commonly recorded during head testing and torque output.

My last thought is that there be similar data with heads as is available for camshafts. Think about all of the specs of a camshaft, its easy to determine engine performace changes based upon changes to the lobe profile, duration, lift, lsa,ivc, etc.

 

Too many variables. However this WEBSITE is the best method Ive found. Let the masses test different new combos and work out the kinks. Then go with the tried and true "winner".....Seems to work well. Right now based on trolling around the boards the Trick Flow heads are the clear leader. Consistently high results, especially when you see it happening with independent average garage mechanics and not sponsor affiliated numbers. But you have to ask yourself the question....how much are you willing to spend for that nominal gain between quality after market casting top-gun A head and CNC budget performer B. To me the $/hp justified a great performing CNC production head.

 

If you're looking for people on this site that reply to this thread to answer your questions and in the span of a few pages you're going to be very disapointed.

Cylinder heads and engines are just a lot more complicated than that and maybe 5 per cent or less of the posters on this site know enough of the background info on heads to really help you.

It's great to want to learn these things so don't think I am knocking anyone but there is no ""physical/mathematical/geometric correlation between the data commonly recorded during head testing and torque output"" that you can simply look at and know an answer.

In fact most of the heads people talk about on this website are damn near the same anyway and the power differences are not always even do to the heads.

 

I agree that so far from real world testing the TFS heads seem to work great as well and so have the AFRs and so have the ETP for us.

Heads and cams basically need to be sized to the cubic inches you have and the rpm you are going to turn. Also flow numbers always seem to equate to power for me usually but then again I know when numbers are real or not and whether the engine is large enough to see any benefit out of them.

 

.

Welcome to the exciting world of throwing all our money away on some damn cars.

.

 

Unfortunately is NOT easy to determine performance changes with cam changes in the real world without testing the combination. We appreciate your desire for a easy way to simply quantify something that, because of the complexity of an operating engine, is not easy to quantify. Ah, tht engines were that simple!

The only truly accurate method is to ask the "Ultimate Expert"...Mother Nature. The problem is She is results oriented, and gives you performance information without any explanation as to why or how the parts worked.

Early on I wondered why we speak of Mother Nature, and not Father Nature. Many years of working with (or against) Her enlightened me as to her gender.

The folks who have the best understanding of "how the world works" seem to do the best job porting heads, as evidenced by the results achieved by engines equipped with their work. Some of the very best of these work in or own "captive" shops where they only work for their team or themselves, not for the general public. Others' work is for sale if you have the time and the money. Choosing the best of these can be daunting. Your engine builder might be a good place to start.

My $.02

 

You compare cylinder heads at places that sell cyl heads. We all can tell you what combos we have used in the past but if that is not going to be your exact set up than, there all merly guesses. If you ask the question "Whats the cheapest way to come up with 400hp using decent parts" you might get more of a answer your looking for. If you call the head manufacturers and say to them what you want to do and whats the most you need to do it, then i think youll get your best answer. But as mrdragster states, be prepared to throw money at it. Matter of fact some of us are in the process of throwing close to 8000.00 at cylinder heads alone. Sometimes it comes down to how fast do you want to go, is relative to how much you have to spend.