[Region Warrior]

Skip, are you saying what works for one engine, may not work on another "very similar" engine?

[Skip Fix]

Mainly saying by your definition of variables there aren't too many "similar" Pontiac motors to compare.

Shoot hard to compare a stock rod vs a Eagle rod on a Pontiac as that changes the whole possible rpm range possiblities.That alone has probably made the biggest difference in our Pontiac hobby-reasonable priced rods choices over the past 10 years. Don't have to drop $1000 for Crower or Carillo like we used to for insurance.

I'm also saying "in general" motors regardless of make do respond the same to changes, but even similar Pontiacs don't always because there are no absolutes. Everything is specific application dependent(system analysis) because of these many subtle variations you listed that can add up and act differently, or the same. You just have to try it whether its a 455 Pontiac or a 383 Chevy, each individual engine has its own set of new variables. That's why trial and error are the only way to really see what works.

Two quick examples
1) KRE heads from 6X heads(I know different flow numbers) on Jim's vs Cliff's-different results same part changed.

2)My 1/2" 4 hole Q jet spacer off my RAIV 400 on Lloyd's motor-same carb model(both are virgin as far as bleeds) same intake casting-72 HO. round port heads so similar intake lengths, port size, exhaust port size,chamber shape-different compression ratio, different CI but same rod length, 230 ish cam specs @ 0.050 but one a solid one hydraulic so alot of the same specs even you mentioned to be the same, RAIV picked up hp, 455 HO lost hp.Same part changed different results. How many others have picked up with spacers to prdict a HP and torque loss on Lloyd's?

[Skip Fix]

Jim a new LS1 head from AFR you and I would both like 5cc smaller than stock but much better airflow by 70 cfm!(It's still 205cc on a 325ci motor, I know EFI different block etc etc drive a new CHevy truck they don;t shift over 5500). Shape difference got both flow and small ccs. So shape is just as important as just the size.

[slowbird]

Here is an interesting post by a well known head porter. Notice where he says that the higher flowing head has less cc's but it is still slower. This is just a part of his post:

just a Month ago, i had 2 pairs of identical castings
1 pair Flowed 404 CFM
1 pair Flowed 375 CFM

which of the 2 pairs would you choose ??
the 404 CFM pair ?

actually the 375 CFM pair Runs at least
2 Tenths ET faster and 2+ MPH faster
than the 404 CFM pair....yet the 404 cfm pair has a smaller CC volume
and on paper looks much more efficient .

there's a lot more to Cyl-Heads than Port Volume CC's and Flow Numbers
like actual Velocity Profiles, Port Shape, Flow Direction,
Chamber transition, shape, and burn pattern + rate,
Spark Plug placement/location, mixture suspension/attachment/quality

Sure i'd like to have the 404 CFM head with the 375 CFM velocity profile,
...the 404 CFM heads would be faster , but sometimes you can't because
you are limited by the casting.

its sort of the same with SuperStock castings/Rules,
everyone has the same casting number, valve sizes, port volume CCs,
to use according to Rules, but the HP , Torque, RPM points of Peak
HP and Torque are different between whoever ports and shapes these
Heads. HP and Torque can vary greatly between these same castings
even with same FlowBench CFM Numbers/Volume CC/Valve Sizes


Darin Morgan is coming out with an Article just on this Subject.
_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
www.maxracesoftware.com

[johnta1]

HEY!
I was just going to post that.

Here's the link.
Speedtalk

[Skip Fix]

"there's a lot more to Cyl-Heads than Port Volume CC's and Flow Numbers
like actual Velocity Profiles, Port Shape, Flow Direction,
Chamber transition, shape, and burn pattern + rate,
Spark Plug placement/location, mixture suspension/attachment/quality "



Gosh isn't that what I said when the discussion was strictly around port size! More variables!

[Larry Navarro]

Originally Posted by Skip Fix

Gosh isn't that what I said when the discussion was strictly around port size! More variables!

uhhhh, NO!

[Skip Fix]

"Numerous tech articles have shown better flowing heads do perform worse. Jim McFarland has some articles showing same flowing heads that perform differently due to the fuel wash in the chamber from how the port was shaped. Same flow, same size port, different shape, poorer performance. So there are many variables just in the heads from port shape, chamber shape, tumble, swirl that can affect performance of equal flowing and equal sized ports. Many of the high end racers are even using wet flow benchs and learning even new data, like plain flow benches showed us when they first came out."
Here you go Larry, from a previous post.

But I guess since they were talking a 400 cfm head it must not be a Pontiac so it's not valid test(could be a Tiger), unless the smaller one worked better, right.

[Cliff R]

I was recently reminded by a good friend that we "don't race dyno's", or flow benches for that matter. Actual vehicle performance can vary quite dramatically from the simple installation of "better" flowing cylinder heads. There are simply too many other variables involved, most importantly the camshaft. Changing the head flow characteristics often requires a camshaft change to fully optimize the new potential.

I had this discussion recently with Jeff Kauffman when he was prototyping the new High Port heads. They made some KILLER numbers right "out of the box". They were ported in stages and re-tested on the same short block, with diminishing returns. Until the camshaft was changed further port work didn't produce improved results in direct proportions. In other words, once an "optimum" combination or balance is reached, installing bigger heads with more potential didn't help.

Most everything with this part of the hobby is about balance and combinations. It's difficult to evaluate a single part, even with direct testing. We tested intakes and spacers last season, all of which are known or inferred to make more power, and they did. We ran more mph with the Tomahawk intake, and even more when a 1" spacer was added. We also ran more mph when a 1" spacer was added to the iron intake....but...in every case ran slower ET, all else being equal. No doubt we added more hp, but at the expense of low end power. Without making any other changes, launch rpm, gearing, etc, adding more hp did not show an improvement at the track.

Jim Hand saw the same thing with the KRE heads. No doubt they made more top end power, as would be expected with the increase in flow potential, but they still did not run as quick in ET. Like it or not, there was a loss in power at lower rpm's with better flowing heads, simliar to what we saw with our better flowing intake and spacer testing.

One thing that needs to be mentioned. Our testing does not indicate that any of these parts are not good items. Once you find an ideal combination of parts for your particular vehicle with the parts you are using, and dial it in with many hundreds of runs, it's not easy to improve the performance by simply adding a single component. In most cases, several others changes are required.

For example, we ended up running quicker with the 1" spacer on the iron intake. In order to do so, we had to increase the stage rpm right up to the point the tires would barely hold. We also increased shift points to 5500rpm from 5000rpms. We ended up running .02 seconds quicker and almost 2mph......Cliff

[Motor Daddy]

In more simple terms:

You can't move the powerband up, and continue to run in the old RPM range, and expect quicker times!

[gearbanger]

Originally Posted by motor-daddy

In more simple terms:

You can't move the powerband up, and continue to run in the old RPM range, and expect quicker times!

That is what I have been sitting here thinking the whole time! Jim, why did you put a higher flowing set of heads on your car and try to run the same rpm that you were with the restricive iron heads? If you would have put a little bit higher rpm convertor in it and matched up the components of the engine to those heads, I am quite sure it would have gone quicker and faster.

Were you just trying to see if your heads were holding you back?

[Jim Hand]

I posted the following several hundred posts earlier on this topic:

"I had worked hard with the new heads, and added 30 degree intake seats, backcut both valves, and used the same seat cutters as we used on the iron :heads - all to minimize the possibilities of some other change causing problems or significant differences. I wanted to run them - to save weight, to have new heads, to not have to worry about cracks or leaks in the iron due to age or porting. I had considered having the chambers and runners coated, but knew that could hide or distort any significant changes in performance."

I also posted this earlier in the thread:

"So it is not a simple question of little ports are good, and big ports are bad, or vice versa. Rather, it is obtaining the optimum balance of port size/velocity to complement the engine and the load it sees. For example, I have known for years that the 165 cc ports on my 64 heads were limiting peak airflow, and therefore peak power. But I also know that peak power is only one of the factors in running well at a track."

Accordingly, I have traded some top end power loss, due to small ports, for superior torque in the low and mid range. And a bonus to that is not only does it help drag strip performance but also improves throttle feel and response on the street.

Jim Hand

[Cliff R]

"In more simple terms:

You can't move the powerband up, and continue to run in the old RPM range, and expect quicker times!"

It's not quite that simple. Any change to the power curve, or shift in power from changing parts also effects the vehicles ability to hold the power, aside from being able to effectively use it. Most street cars don't hook up well enough to see the dramatic losses in low rpm torque/HP from simple parts changes, such as intakes. For the most part the performance of these vehicles is evaluated by the "seat of the pants". Even with my own vehicle, the MT's slip just a tad on the street, and we ALWAYS believe that we are going to run quicker when installing most parts that improve upper mid-range and top end power or shift power into this area.

At the track we are disappointed nearly every time. It goes back to what Jim has been posting about engine torque, with good traction. When we find good traction, and leave at a relatively "low" rpm, the engine is loaded longer and heavier throughout the lower rpm range. It actually spends very little TIME in the rpm range up near peak HP production. The amount of power produced from the time the engine is loaded to the shift point(s) has a dramatic effect on ET. Broad power and torque will produce better timeslips in most cases with vehicles set up such as ours, vs engines that have excellent upper mid-range and top end power characteristics.

Engines with excellent off idle and low speed qualities, in addition to being very easy to drive, also have an additional advantage, they hit the converter and tires HARD, helping to get these heavy vehicles moving, again helping to make good track times. Have you ever watched a really fast car make a good launch then break early in the run and coast through in the 10's at just over 100mph!!!.......Cliff

[Skip Fix]

As Cliff said good hook is needed to tell that bottom end Jim's car has the advantage of really good traction and why it is such a good test bed.My car is very track prep dependent.

If you are traction limited sometimes a little loss of bottom end can allow the car to hook earlier(why there are staged N2O systems) and pull harder through the rpm ranges. The opposite can be true also, and cause a complete bog that can be hard to tune out. My son's 81 TA with a stockish 400 the factory lockup TH350 copnvertor was so tight it could barely turn the tires on the street and had a terrible bog. Looser convertor and it can spin street tires and get moving faster and no bog.

[Motor Daddy]

It IS that simple Cliff!

When you shift the power band to a higher RPM you MUST increase the operational range to effectively use that power band. If you don't, you will be operating at a lower level of HP THROUGHOUT the rpm range.

Ask Lynn how his car responds by operating closer to the torque peak, versus the HP peak.

This is nothing new! We all want more average power, correct? If you get more power, you need to use it! If you shift the power band up 10%, you also need to shift your operating range up 10%. It IS that simple. If you shift the power band up, and you don't shift your operating range up respectively, you WILL SLOW DOWN!

The idea of keeping the powerband at the lowest RPM range, highest torque is great for steetability and tractors, and heavy weights, but completely opposite of what you want if you goal is to be fast with a lighter vehicle! What would you rather have a big CAT motor (disregard the weight of the motor) that produces GOBS of torque, with a 2500 redline, or a motor that screams to 11,000 RPM with very little torque? You tell me! I bet I know what the next question is!

[J.C.you]

i think Jim just wanted the old low end grunt back and was disappointed with the results, after (guessing, 100's of runs with the dports)? tweaking, optimizing this, that, tuning, conveter, etc.....you get the picture......

i have no doubt that Jim would get more power from the Kaufmann heads if he would keep working with them...... more than the iron heads? maybe, maybe not at 5500 max.

i may be way off the mark on this, but i am sure the Kaufmanns have done alot of flow testing with these heads and could shed some light on the subject.....

i have a few guesses that may help the Kaufmann heads in your combo to 5500 max rpm range. i have never seen a kaufmann alum dport but, reduce minimun port CA by epoxy to maybe the (2.2 range?) to increase FPS close to 300 at the short turn. (he he... this will reduce port volumne also) again, i have never seen a Kaufmann head but, you may be hurting with the 30* seat also....... combustion chamber walls are probably better for a steeper seat angle and since the short turn probably has less of a dog leg than the old iron dports....... and raise compression one full point more than the cast iron dports........ my cents.....

[Cliff R]

MD, sounds great if you live in a perfect world, however, we do not. You want to rant and rave for some unknown reason? I don't particularly like the tone of your post, so have no comment. I'd rather just post usable and accurate information as we know it to be, and leave it at that.....Cliff

[Motor Daddy]

Cliff, I have no beef with you. I think your great. Sometimes I get a little excited because people talk about changing a part that shifts the powerband up, and then talk about how they slowed down when they kept the same gear, and launched and shifted at the old RPM! Go figure!

[Cliff R]

You are correct, we see the same thing all the time. We campaign several cars out of this shop and have logged several thousand runs with them in various configurations. We have one that leaves "soft" and finishes hard that runs mid 10's up near 130mph. It barely outruns my car in 60' times and uses the top end charge pretty well to make for some pretty good ET's.

With my car in particular, we have never been able to install any parts that shift power, or make more power in the upper rpm range, and improve ET. Even with higher shift points and more mph, the slight loss in 60' times is not completely offset by the strong top end charge.

We came pretty darned close testing the Tomahawk intake with a 1" spacer. On a back to back test, we lost almost a tenth in 60' times, and added about 1mph on top end, slower by .08 seconds. With the 1" spacer and a higher stage rpm and shift points, we narrowed the gap to .02 seconds and ran nearly 2mph faster.

One would have to decide at that point if it would be worth a ring/pinion and converter change to try to run quicker? Our converter is about perfect for a daily driven car that sees a lot of strip action. It is coupled near solid above the stall speed, and flashes well past 3000rpm's on the launch. Here's the "catch 22". A looser converter may improve 60' times, but more often than not they are not coupled as well above the stall speed. The lost efficiency for the entire run may have a negative impact on both ET and MPH.....how many times have we seen this happen?

That's really what I wanted to say about your first post. Despite the very best planning and parts selection, we very often end up slowing the vehicle down with changes that shift power and additional changes to more effectively use it. In other words, there can be diminishing returns, we will not always see a performance improvement, or at least not nearly as much as expected.

I'll give you a real world example with a car I used to own. 1970 Roadrunner, 440, 3000 stall, 3.91 gears, 284/484 Mopar cam, stock intake, ran 8 flat in the 1/8th mile with open exhaust and slicks. We installed a Tarantula intake, 4.56 gears, Holley 850, larger Crane cam, same converter. Test drives indicated we were going to run a LOT faster, it was a BEAST on the street, pulled WAY harder than the old combination. I still remember picking up that first time slip......8.50! We never did get that combination to work and I didn't have the money back then for a good converter, so we put it back the way it was........Cliff

[Bruce K]

Originally Posted by Skip Fix

"
My car shifted at 6000, only 455 ci HEI, clutch fan, radio, amps, electric windows 239/247 flat tappet hydraulic E heads a spinning 11.30s @ 122 it first out with no timing,jetting or gearing changes.So it can be done easily with big heads too following a different formula.

559.66hp! (according to Walace Racing calculator, using 3750 lbs.), Wow nice, I'm hoping to rpm 6000+, trying to save my tranny until I can get a Tremec.

I checked out your cam (239/247) on the Lunati (Holley) site. I can't understand why they rate your cam as being more agressive than solid rollers like the 507A3LUN (255/263). Can you shed any light on the subject? Thanks, Bruce