[Skip Fix]

I'll chime in some thoughts here, I actually think most parties are in agreement.

We'll start with the original question velocity vs cfm- unless you map the entire port with a pitot tube and measure velocity we are guessing what the decrease will be. Will the decrease in that velocity be made up for in performance in the added airflow?? We don't have real numbers for what the size is of the 310 vs 320 KRE heads, we do know they are larger than the 185cc out of the box KRE head. Yes in theory a smaller port flowing the same CFM wil have more velocity and be more effecient, but will other choices in the combination negate that? Just because it has more velocity doesn't always mean it will perform better. Does it tumble worse or have better swirl?

Just because it has more velocity is fuel staying in suspension? The shape of the ports can make a big impact there, even a small port.A good even burn pattern over the pistons and chambers. Deck height and quench, intake runner size, length, plenum size, header diameter, tube length, collector size and length all play into this. Then you get the chassis variables -convertor, gear ratio and its multiplication, tires, springs-the list goes on.

But the biggest things has been touched on by Jim, Steve, and J Schmitz-its about the whole combination. Even with iron heads, E heads and now the new KRE heads we can see the choice of other components rock the performance one way or another. If the components aren't matched perfectly the whole theory goes out the window. Kind of like Superflow's Hp formula/cylinder hp= cfm @ 10"x0.43 for the IDEAL combination!

Cliff Ruggles with also a very consistant combination with alot of street miles and track time and not too different from Jim's. It has run faster with the larger cc KRE heads over his iron head combo, made more hp on the dyno over the iron heads back to back. So in that particular combination the larger cc ports and slower velocity did not hurt performance.

I think what Steve was saying about the "feel" on the street won't be noticed for most of us, maybe measured at the track but not felt definitively. That can also be described about Cliff's impressions using a Holley intake on his car he has posted before. Seat of the pants felt faster , but it wasn't. So our "feel" is really hard to tell us what the track can. Another Pontiac friend "felt" swapping an UD 288/296(RAIV spec) cam over an 068 made his 428 TA car slower, but it picked up 0.3 seconds and mph at the track! So a feel of .1 second, or 0.3 in my friend's car, is going to be hard to feel for most of us, not that we want to lose time just hard to feel.

Unless you do back to back swaps on the dyno and in the car like Jim and Cliff have it is all really theory for every other combination, specific ones like Jim's and Cliffs have showed different results with the same swap, that shows me there are more variables than just the cc of the ports even on well scienced out combinations.

Shoot if we look at what the NHRA stockers with 1978 smogger low compresion 400s, factory weight, restrictive secondary intakes, NON ported heads are running low 11s what do we need ported heads or aftermarket stuff for anyway?!! Those 74 350 GTOs are in the mid 11s also!

[Jim Hand]

Skip,
What kind of heads did Cliff have on before his swap? Do you suppose changing from 220 peak flow to 260+ might also have had an effect on power? In other words, Cliff's change to KRE heads was a totally different deal then mine. And they work great on Cliff's car, just as they did on mine. But I already had good heads and excellent performance history with them. And there is no doubt whatsoever that the larger ports on the KRE heads cost performance on my car!

Cliff changed from basically unported heads to the KRE heads. How would he or you possibly know what effect the various parameters of airflow, port volume, velocity, etc., had on the change?

I agree that the total combination of parts is what determines how each car performs. But Cliff's change proved nothing at all about the effects of port volume on performance. How do you know that smaller ports wouldn't have made it even quicker?

Jim Hand

[P@blo]

I think the NHRA stock class run a 5500 stall torque converters so they may not act very good in daily street conditions. It has also been suggested that NHRA guy's that run these times message the ports and then peen them for a stock look. In any event I bet any of the port work they do doesn't stray far from a stock volume port which again supports what Jim is saying.

[Skip Fix]

Jim I think you just stated my main point-on Cliff's car it used a bigger port and more cfm and got better performance, not a decrease, over a smaller port, lower cfm head. The increased cfm made up for the decrease in velocity of the larger ports in performance! I don't think Cliff has felt a decrease in bottom end street performance going to the "bigger" heads. So the statement a bigger head will kill performance is not the whole story as I've stated(and you), it's the whole combination.Cliff improved with bigger ports and more flow-others may also.The better designed chamber might be a factor also, more variables as you've pointed out than just port size, cfm was a factor too, his wanted more.

Yes maybe an equal cfm flowing head with a smaller port may get a decrease in performance as your car did. But as has been discussed before we have to use the same flow bench, or its apples/oranges. I've flowed heads from good reputation Pontiac porters that don't flow the same on my bench or a Superflow bench as they did on the porters bench. Some lifts more, some less. One "280 cfm" D port couldn't keep up even in the low lifts with an out of the box E head.

Jim most folks don't have the advantage you do of flowing them on the same bench and having such a consistent car.Most of the 260+ cfm D ports aren't going to be done as meticulously as yours to keep the port volume small or the same as stock, unless it's on a Super Stocker where they have to keep the ccs for tear downs. I'll bet just their port and special valve jobs cost more than a set of KRE heads for the time involved to get there. Not the "standard" ported iron head most guys out there get for $5-700. Shoot I think Larry Navarro said his ported D ports are 185cc, not the 154cc NHRA specs are for most D ports.

Pablo-the reason the port work stays close to stock is that's the rules, they get torn down and measured, iff too big disqualified. It would be much easier(and cheaper) to get the flow without having to weld or epoxy back up the port.Stockers can't port. Neither can touch the combustion chamber to improve flow. My point there was the stockers(nor Super Stockers) have poorer flowing heads than Jim and most of street/strip guys yet their combination can out 60 ft and go faster than alot of "better" combinations, because it's the whole package. And yes a 260 @ 0.050 cam and 5000 stall are not as streetable but then we get into the debate of what the definition ofstreetable is.

[Larry Navarro]

Originally Posted by Skip Fix

I think Larry Navarro said his ported D ports are 185cc, not the 154cc NHRA specs are for most D ports.

Close, but they measured 181cc.

I have been reading this topic with some interest, however the real proof is on the track.
We can talk about theory all we want but I have seen a few moderate to extensive ported iron D-ports just in my area.
Lee Atikinson and Dave "Torqjunki" Sober have proved that it doesn't take an "exotic", high-flowing head, or ROLLER cams, to run some serious track numbers and be totally streetable.
I'm sure most here are familiar with Lee's combination and it's a mid 11 second car.
Dave just ran some 11.60's in a heavy 2nd gen bird with 2800 stall convertor, 3.42 gears, full exhaust, a 236/244 flat tappet hydraulic, 750 VAC. SEC. Holley and set of moderately ported 6X-8's!
I'm envious as hell as this car incredibly tame on the street as compared to my car.
Sure it takes alot of experimentation and technical skill but isn't what this hobby or sport is about?
Yeah, the aluminum stuff is great too. You want to go racing with serious impact? Then great, go with what needs to be done....Aluminum can get you there.
To me it's all personal preference. I see a set of KRE's in the future for my car, cuz it looks cool..

[Larry Navarro]

Originally Posted by Skip Fix

Most of the 260+ cfm D ports aren't going to be done as meticulously as yours to keep the port volume small or the same as stock.

I'll argue this statement.....or Dave will.

[P@blo]

Skip, I totally agree with with your statement on peoples definition of a "street car". Look at the Mighty TA or the Dudes 8 second street cars, I'm betting I won't see them fill up at the local gas station on there way to work.

Great topic guy's

[Steve C.]

This might be of interest: http://www.wighat.com/fcr3/engine.htm


( I knew it wouldn't be long before the "don't waste your money" bantering or "you don't need fancy parts to go fast" comments would work it way into the conversation )

[Jim Hand]

Skip,
I have never stated or claimed that higher flowiing heads with bigger ports would cause a performance "loss".

What I have said, am saying, and have proven conclusively is that larger ports with similar airflow capability will lose power as compared to similar flowing heads with smaller ports.

The fact that Cliff ran better with the KRE heads over his stocks heads is obviously a result of the added airflow and 50# lighter weight. And the modern chamber design also helps.

Let me make this as simple as possible without all the unrelated "possibilities"!

I ran iron heads that flowed 255 @ .6 lift, had 165 cc port volume, and had 10.08 static compression for about 6 years. I have excellent records on their performance with a range of cams. With no other changes of any kind including the cam, I switched to a set of KRE heads that I had specially prepared to duplicate my iron heads in regard to valve size and angles. After cleanup and opening the ports to match my previously prepared RPM intake, the KRE heads flowed 273 @ .6, and the exhaust flowed an honest 76.9 % of the intake as an average of each lift point. The final port volume averaged 186.5. The finished chambe size of the KRE headds made the engine 10.38 static CR And I might add that they lightened the car by about 50#.

And they "felt" great" The car launched well with no misses, stumble, bog and so on. And yes, it had good low end power!. But since my car does't spin, even on the street, I can't relate how far the tires spun!

But at the track, something went amiss. The car didn't launch as hard, even with that great feel on the street! The ET was almost .2 seconds worse. Yet the MPH increased by one to two MPH! Oh well, maybe it was the track, or the weather, or something else - at least that is what I wanted to think after about five runs.

Went back a few days later and exactly the same, if not worse, performance!
Went through all the normal timing and mixture checks - no difference.

Went back a third time - this time there was simply no doubt - my new higher flowing 50# lighter aluminum heads were just not making as much total power as the 255 iron heads. Yet, the car was running faster MPH which indicated it was recognizing the added airflow, and that indicated we had no unexpected engine problems of fuel delivery or ignition problems.

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.

Since the KRE heads had lost significant 60' time, had Bullet grind a custom cam of 233/235 with max possible lift on 108 LS in order to pick up the 60' time. It worked - did pick up almost .1 in the 60' but in the process lost 2 MPH, and the final ET was still .1 to .2 off from the iron heads.

Went back one more time for the fifth trip to the track with the new heads. It was a little warmer and the car would barely break into the 11's! That was enough for me!

I left them on while I did a little more work on the 6X heads that were on temporarily after one of the 64's developed a water leak after 6 years service. Since my engine recognized the added airflow of the KRE heads, I added flow to the 6X's. Since it lost so much low and mid range power due obviously to the 186.5 cc port volume, I was very careful with the re-porting of the 6X to keep the ports as small as possible. The result was average flow of 265 @ .55 with port volume of 170.

Off came the KRE and on went the 6X. Again, good street feel, strong low end, good throttle response, and all the other benefits associated with good fresh properly sealed heads with good airflow. Went to the track and what do you know? Even though the car was 50# heavier then with the KRE heads, and had about 8 cfm less flow, it ran quicker by almost .2 seconds, and was just as fast in MPH! And it picked up almost .1 second to 60'. (Last time out ran from 11.49 to 11.56 at 115+, 1.62 60', with 3.31 gear and hauling 4050# on 92 octane pump gas).

Skip, you can write as much as you want, you can quote others, you can estimate what Cliff's car "might" have done, you can tell me for the 10th time that chevy's use bigger ports, but I have the numbers! Bigger ports with equal airflow will give up power as compared to smaller ports with equal airflow! It is that simple. You have read it in most every good technical material, including McFarland, Vizard, Circle Track magazine, PHR Rod magazine, and countless other reliable sources. And Tom Hand wrote and posted a postulation about this subject with help from Harold Bettes of Super Flow in about 1999, and was 100 % correct. He compared the expected performance of stock E heads against my ported iron heads on my wagon, and the results he came up were exactly what happened with my current tests!

As I had since made the engine larger, I thought it could handle the relatively "small"port increase to 185 as compared to the 216 of the E heads, but unfortunately, I was wrong. As Tom wrote, and I have dozens of times, new heads of any kind will likely make any car run better, both on the street and at the track. But I am not talking just about running better, but rather what the real effects of port volume are on total power production. I am talking about what is the ideal combination of port size to RPM, the required flow, and all the other factors we both know that affect engine VE.

And I have also said dozens of times that any new head will likely add performance. The real subject of this topic is not that, but rather what effect port volume has on total power production throughout the entire RPM range. The fact that many cars aren't loaded at lower RPM due to converter selection, or manual clutch, does not enter into this discussion of actual engine power production. The fact that E heads allow us to spin our tires on the street is totally immaterial to this discussion. I once owned a 6 cylinder Studebaker with4.56 gears and OD that would spin the tires through the entire first gear, but still couldn't beat am El Paso city bus (loaded) across an intersection!

Also, the "amount" of lost power is not that important in this discussion - rather the fact that power is lost. Even with the loss, most cars that install KRE heads will run far better then they ever imagined. But again, I am talking about real technical effects of design attributes on performance. I recall several years ago a post that was copied off another unnamed board that stated port volume was not important. What wasn't discussed was that it came off a PRO Stock source - from the world of .9" valve lifts, and RPM that is never under about 7000 RPM and runs to almost 10,000! Sure, who cares about power at 2000 on an engine that won't even run under about 2500 RPM. But for those of us in the real world, 2000-3000 represents the typical cruising RPM and that is where we want and need optimum power and throttle response.

Finally, you can be sure that if I could have found a way to make my car run at least as well with the KRE heads without changing RPM, and associated converter and gear requirements required with added RPM, they would still be on. They are an excellent head, but did not match my car setup as well as my iron heads due to reasons noted above. And because most don't or can't prepare heads like mine (if true) does not change the fact that port volume does indeed affect total power production!.

Jim Hand

[P@blo]

Jim,
Great information and always look forward to reading your posts.

[Steve C.]

As always great tech material.

Theory supported, and indicates how and why a 0.1 sec differance in ET can be important.

Thanks.

[Skip Fix]

Larry, I'm not talking Dave's port jobs, I know he does some flows it etc, I'm talking the normal port jobs from commercial shops out there. Most knowledgeable guys like Jim, Dave etc that have access to a flow bench usually spend ALOT more time doing their own stuff than a shop would. Most of us are pickier than a commercial shop on our own stuff, just look under your own hood and how nice it looks.


Yep the experimantation and tuning is what most of enjoy about the hobby. That's what gets the best out of every combination, some of like Dave and Jim are better than others of us. But bigger isn't always bad.Your hogged out D ports should then be really slow then, I think your mph shows they are working pretty good(get rid of that stick and times could be faster!) and Cliff's non posted small D ports were slower than his non ported bigger better flowing KREs.Shoot if you remember my little "big iron head port" RAIV 400ci Q jet HO intake ran pretty close to Lee's car when it had a 455 Torker II and a Holley.

Only a consistant combination like Jim's or Cliff's can tell us what a back to back swap can do, throw a little bigger cam in the equation in Jim's motor and the outcome may be different, the bigger heads may make a difference more either way, but that shifts the rpm range where Jim doesn't want to.

To even look at rpm ranges I believe Steve Coombs with a similar E head motor to mine but a larger(but conservative) street roller had a HP peak around 5700(correct me if I'm wrong Steve), my smaller flat tappet hydraulic peak HP was 6200, that doesn't equate with current theory either, smaller cam higher rpm peak? Variables!!!

Shoot even talking track time does the track prep the same? otherwise 60 fts can be way off. My last outing a drag bike racer was spinning at Sequin that has NEVER spun there before, and had no changes to the bike.

[slowbird]

Jim Hand
Have you ever tried a 45* seat? I know that the KRE heads were designed to use a 45* seat.

[Steve C.]

Skip- 254 street roller peaked at 5700-5800 rpm / 507 ft.lbs. TQ at 3200 rpm, 589 ft.lbs at 4400 (peak). Shift light at 6,000 rpm.

Recent change to 248 cam and it goes south big time at about 5600 rpm on the track, combo can't get out of its own way now

( potential spring pressure issues and possible gearing mis-match clouds the overall picture )

[Jim Hand]

Slowbird,
Only on a flowbench, and I didn't like what I saw for my low RPM engine. A bit more flow above about .35, but considerably less below that point.

And note that the 273 cfm flow with the 30 seat is more then most are reporting with 45 on the KRE 87 cc head. But again, I used a 15 degree top cut, medium wide 30 seat, and 50 and 65 blend cuts into the bowl. No porting other then blending the last cut, and opening the ports to the gasket size I listed for you yesterday. And the valves have a 15 degree cut towards the stem off the seat.

Jim Hand

[JSchmitz]

Jim, do you think that 10.08 iron vs. 10.38 aluminum is a good apples to apples compression for comparison? I would like to know what your car would have ran with closer to a full point increase. This could explain the apparent loss of low end. Have you done a similar test with E-heads? I know the headers are different. But, real numbers would be interesting.

I have an interesting story that is relevant. A friend of mine is a huge big block Chevy fan. Always bragging about rectangular port heads, going off on the "poor" Pontiac ports, etc. Well, he went along with me to my engine builder one day (Jim Moran @ MBJ Machine). We got to talking about the "great" rectangular port heads. Jim proceeded to tell my buddy how, "back in the day", they used to take rectangular port heads off and replace them with oval ports. They supposedly ran much better. My buddy was crushed.

[slowbird]

Jim,
I know that on the flow bench the numbers dont look as good, but we dont race flow bench. I have personally had really good result with 45* seats on our 62 heads (both on our 406 and 462). It would be great to see you try it and post the results. As you and your car work great as a test bed for parts and things like this.

[Jim Hand]

JSchmitz,
I wish I knew what the optimum difference is for compression between iron and al, but I don't. As I run pump gas, wanted to be sure the KRE heads would handle the 10.38 before making a bigger jump, and they did. And for sure, adding CR will add power at all points providing the gas can handle the compression. But after the results I obtained and the effort I expended, did not wish to continue trying to find ways of making the heads equal my iron heads. And milling is a permanent change - too much and you are in doo-doo!

A late issue of Car Craft tested "similar" iron and al heads and found no difference in power due to the heat loss - so no added CR is needed! I am not sure I buy into that, but it does illustrate there is no specifiic or given required difference in CR to make equivalent power.

Jim Hand

[Skip Fix]

Jim we were posting at the same time.We've had this debate before. Your car proved on YOUR particular combination the bigger heads reduced performance.I think we both can agree that smaller ports same cfm will have better velocity and should be more efficient IF they don't have a fuel distribution difference or other problem somewhere else in the equation.NO ARGUEMENT!! Even the Pro Stockers accept this. Case closed.

The original question here was "will the 310 vs 320 KRE heads(or similar E heads) have less streetability/low end". As I stated and I don't know how you can disagree -he can't tell without doing a back to back trial on HIS particular combination like you have done so many times and stay in his same exact rpm range.My track has inconsistant preps and my 60 fts can chage 0.2 seconds without a change inthe car.His combination COULD be like Cliff's and like the more airflow more than the loss of velocity change.Yours went slower with the same part, Cliff's went faster-other variables are the difference not the port cc by itself.I think any statistical analysis would hold that up.Without exact port volumes posted for the different cfm KRE heads(none yet) we really can't even tell how much cc difference there is either to begin to guess at the velocity change.Are the intake exhaust ratios the same when using the same cam with different heads(iron or different KRE ported)?


Like Cliff's motor the increased air flow may overcome the loss of velocity(and faster than the weight difference would make). When we start looking at different combinations(his was not completely listed or his rpm range/goals since the choice of 310 vs 320 I'll assume a higher rpm range than an iron D port) we can't tell which works best without many trials as you have done, and that still assumes the parameters of design(rpm range as an example for yours) stay the same.The combinations and variables(I didn't even mention the heat transfer loss of HP of aluminum vs steel) in them are what makes "feeling" or measuring the difference the dificult part.
Most of us don't have the set combination parameters to stay with when we get the "go faster" bug, so shifting at 5500 vs 6000 may not make a difference to the owner.

I've done the stay ion the same parameter deal when I was NMCA racing the 400.Shelf full of cams, different advance/ retard runs, different intakes, carbs,headers, mufflers, shocks, springs, convertors. It went faster and had more bottom end with a cam no one says should have made it do that , more intake duration than exhaust.Maybe not as many passes as the wagon but alot for me at alot of tracks all over from Dallas to Atlanta over several years. It was always consistant for it's current combination like the wagon. Individual combinations take individual parts to optimize. Each is it's own "apple" to "orange".

My new combination I just wanted to go faster period. 239/247 @ 0.050 flat tappet hydraulic, more intake ratio than exhaust, 0.030 455 6.625 length rods(another potential variable) with 320 cfm E heads peaked at 6200 on pump gas. So Steve's roller combo peaked at lower rpm, but different dynos. On a poor track it's only time out spinning 11.34 @ 122mph 1.7 60 fts shifting at 6000(tach issues that night). So no long term dial in yet, 3 passes total.The convertor change made more drivability change than anything between the two motors, another variable in the equation. Then we have 4 link A body vs leaf spring F body variables.It drives like a stocker around town, only lumpy in gear at idle with regular lifters.

[Skip Fix]

As far as the difference in aluminum vs iron compression, I think I saw a magazine dyno test that results questoned the 1 point difference. Don't remember where.