[Jim Hand]

Slowbird,
Want to emphasize again that I shift at 5500 in both gears. Low end power is very important on my car. And low lift flow has tremendous advantage - the better flow at low lift helps on both ends of the valve action. It effectively starts flow earlier in the lift cycle, makes the lobe appear steeper (on both open and close), and allows good amount of air to flow longer. Good low lift flow also holds peak HP up a little longer in RPM.

And yes I agree that 45 also has advantages, especially for peak flow and higher RPM.

And you say you have had good luck with 45 - I have had good luck with 30 also. So I suspect we would not see much difference in total performance on my car.

Jim Hand

[Larry Navarro]

Originally Posted by 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.

Normal port jobs?....define "normal"
Commercial shops?....you mean like Butler, KRE, SD Performance, etc.

Heck, the heads on Dave's latest car were done by Sd Performance, from a previous owner.....Dave didn't touch them.

C'mon Skip....my heads were done by a guy at a commercial shop....AND were not flow tested till after I received them.
Sure those ports are hogged out but I would gladly exchange them for higher velocity, lower cfm rating....mainly because I drive my car on the STREET, than on the track.

[slowbird]

You never know until you try it. My dad swore that we would loss power when we switch. It work so well on the 400 that he did it to his 462 that is in his 69 GrandPrix that weighs 4150lbs. It gets 1.62 to 1.64 60ft times and runs 11.8s shifting at 5600rpm also his heads only flow 240cfm. It never hurts to try things.

[Steve C.]

Larry- regarding your iron heads pictured, you state "sure those ports are hogged out but I would gladly exchange them for higher velocity, lower cfm rating... mainly because I drive my car on the street, than on the track."

Question, on your car do you honestly feel that these larger runner volume heads have issues with idle and low speed driveability, and the lower RPM throttle feel on the street is a problem ?

[Skip Fix]

I'd bet the SD ported heads are bigger than Jim's for the same flow. I've had some on a bench and the out of the box E heads outflowed them in all ranges.

[Jim Hand]

Skip,
As far as I am concerned there is no debate and has never been on the subject of port size vs power and velocity. As I was looking for the Car Craft "test", run across the following several paragraphs about heads. Suggest you read it slowly and then reread it several more times!

From Car Craft Web Site - http://www.carcraft.com/techarticles/116_head_chev/

"While we have separated these heads by port volume, greater size doesn't guarantee increased airflow. The advantage to midsize heads is that they combine increased airflow without sacrificing velocity, which tends to promote strong torque. One way to look at cylinder-head flow is to include velocity when evaluating heads. In other words, an intake port the size of a tennis ball will probably flow tons of air but at a snail-like velocity. Conversely, smaller port volumes will suffer from flow restrictions but offer fantastic velocity. Velocity, then, can be equated with good torque and excellent throttle response.

If there is a magical combination, it would have to be a port with great airflow and outstanding velocity. This is especially true for intake ports. A good example of an extra-large intake port that didn't work would be the '69-'70 Ford Boss 302 engine. The ports on that engine are huge. Those engines made decent horsepower but were infamous for their lack of torque. This is also due to cam timing but mainly to the expansive intake ports. That's why pure airflow numbers can be misleading. You must also consider the application for which the cylinder will be used. For example, it would be folly to bolt a huge 220cc intake port head on a daily-driven 283ci street car."


Slowbird, I agree that actual testing is the ultimate means of resolving ideas and questions.

For the record, ALL of my testing (with the exception of several mufflers) that I have reported in magazines or on any of the boards has been conducted for the express purpose of finding a part that will make my car perform better. None have been done to disqualify or otherwise compare parts/techniques just for data purposes. In other words, if I didn't/don't have reason to believe that something will clearly help, I don't "test" it.

Jim Hand

[Lloyd-TX]

In my nearly six years of visiting this forum, this has to rate as one of the most constructive and informative threads I've had the pleasure of following.

Thanks Jim, Skip, Larry, Steve C. and all who have added their contributions!



Oh, and Larry forgot to post THE most informative pics of his port work, LOL!

BTW Larry, you KNOW I'm just kidding, dude!

[Larry Navarro]

Originally Posted by Steve C.

Larry- regarding your iron heads pictured, you state "sure those ports are hogged out but I would gladly exchange them for higher velocity, lower cfm rating... mainly because I drive my car on the street, than on the track."

Question, on your car do you honestly feel that these larger runner volume heads have issues with idle and low speed driveability, and the lower RPM throttle feel on the street is a problem ?

I can't tell you either way as I really don't have the "experimentation" experience, or the vast array of parts(or $$$) as some of you guys do.
However, given what I have experienced by others who have "less flow...AND less cam", it's hard to disclaim the fact that bigger doesn't always mean better, especially on the street.

Yeah, right Lloyd....thank goodness for archived threads!!
Not my work, "commercial shop".

[Tom Hand]

I’d like to add a couple of things here since I am the reason Dad is in this discussion anyway. I pushed him to try the new heads because we both knew they would have beneficial features and in fact, they already have proven to have many.

Dad worked extremely hard to get things just right and equal and consistent between ports and valves and chambers. As he said, he touched up a few things and then tested the heck out of the heads on his bench to make sure the ports worked like he wanted them too. He was worried about the port size and he knew they would tend to make the engine less responsive down low. However, the weight should help and the better combustion chamber should work well so we figured it would be essentially a wash, no drastic change either way.

The heads went on and he described all of this in detail earlier. He ran it several times and then tweaked to get it as fast as it would go. Remember, he had these parameters to abide by: no added RPM or no changes that would be harder on the car. It indeed ran faster speed but was in fact slower ET-wise. Perplexing at first but he knew exactly why. So, he let me drive it to get another opinion.

My first thought was it was spongy and slightly sluggish as compared to the other set of heads. Please remember that any car that runs in the 11s or 12s or 13s or 14s is still fast and this statement is a relative one not meant to say the heads were junk. They are not. We ware comparing these heads to his that had been carefully setup for optimum efficiency.

I noted the throttle was less responsive right at the point when you nail it. It ran like a scalded dog up top as usual but, it felt different down slow. A trip down the strip once again confirmed what was happening. Dad clicked off times that were slower than with his other heads but the speed was higher. This is very indicative of larger ports/less airflow immediately at the point when the engine first accelerates. No question, no doubt.

Several readers may continue to ask how do you know this was due to the port volume?? Dad has shared it before, Car Craft explains it, Jim McFarland explains it, David Vizard explains it, and the Engine Masters articles clearly explain it. But you know how I can prove it?

The car would not yank the wheels off the ground at the track. **Note, I stage at slightly off idle and come off no higher than 1600 rpm.** With 50pounds or more weight off the front end it should have been easy to do but it would not. Timing did not help, fuel did not help, air pressure did not, chassis adjustment did not, weather changes did not; nothing did. It would not yank them directly after the burn out area and it would not do it off the line. It felt less responsive than it did before with the smaller port heads.

Again I want to make sure all readers understand and do not assume or jump to any conclusion about what I am saying. The car ran like a scalded dog on the top end but it lost it down low, exactly what we know happens and exactly what larger ports do, you lose air velocity and throttle response.

You also all understand that if we could stage this thing higher **Note, I stage at slightly off idle and come off no higher than 1600 rpm.**or run a looser converter and run it harder on top (higher rpm), it may pick up enough speed to bring the ET back close to what it was before. Unfortunately, that was out of Dad’s goals.

So to answer a question someone posted before about who can feel a tenth of a second change? I can and I did. When you lose reaction down slow but then it picks up on top, it is very noticeable. Not pulling the wheels off the ground is even more detectable.

The KRE heads are great heads and offer many benefits for Pontiacs. They work well, bolt on relatively trouble free and work wonderfully as replacement D-port heads. As many are already seeing, they also offer great improvements in race applications. On Dad’s car, the larger port volume hurt the responsiveness as compared to his excellent D-port heads.

The simple answer then is this. Yes, on a car set to have extremely quick throttle response, you can feel a tenth of a second change. I did and Dad did.

By the way, the smaller port heads let it go back to yanking the wheels off the ground first pass when they were reinstalled. It lost a tad mph compared to the KRE heads but he has since got them running faster and very consistent.

[johnta1]

For an interesting discussion on air flow, velocity, etc.;
Air flow

[Skip Fix]

Jim and Tom you both know I feel you have a perfect optimized test bed combination for your preference of parameters and goals. It hauls rear, is easy to drive on the street, I've ridden in it. I know how meticulous in matching port to port you are(not what I've seen on "commercial" porting Larry even on the provided flow sheets or my bench Larry as much as 15 cfm difference from ports) as well as every detail in the entire car to get the performance you have. That's why it is such a good test bed for subtle changes.No where do I dispute the bigger heads did not make a difference on the feel and performance of your car. But it is still just a single combination with no duplicates out there as you point out. Even Cliff's was different as it had different D ports on it. As Tom just said , throw a different convertor in your car, stall it higher , performance could have improved but you get different parameters from what you want in a combination. If the ccs are the whole answer why did Cliffs pick up performance over the whole range- it had a different combination. Not better, not worse just different.My point.If bigger is worse in all street motors how did it pick Cliff up more than the weight change did? So on a different combination we start from scratch, and possibly different goals.

Jim I think you are misreading things into my posts. I've never implied bigger ports will flow better or perform better in every combination. I've read alot on port theory myself and don't think I'm totally niave on the theory either. Your post seems to be implying that. I've had e mail conversations with Jim McFarland on numerous air flow theories, read the Superflow book also. I'm not a novice in the area either. 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.

Even on your combination the only way to isolate out more variables would be using two sets of 6x heads flowing the same, one with a much larger port than the other but keepin the same flow through out the range. Even another D port head has a totally different bowl shape as the 6X in the intakes and exhaust(documented in many of Pete McCarthy's pictures and articles), so we get into port shape variables.They would also have to be the same -4 or -8 to keep chamber size the same. The -8 have a larger diameter chamber so even milling them to the same chamber cc as a -4 head is not the same. The aluminum KRE with different port shape, different combustion chamber shape and being aluminum add three variables to the test against a iron head. FDA sure wouldn't go for that in approving a drug study.

Since you mention SBC heads let's take a look at what the factory has done, and some of the facts referenced in this same article as a whole.I have read it numerous times and looked at all the data there(and in their BBC head article) as I play with those Chevies too. You can see the GM engineers didn't just use port size as their sole parameter.This is easily seen in the changes and performance in SBC first gen block heads listed there(LS1 we'll exempt different shape but bigger 215 ccs on 4.8L truck motors, different block). I think those GM engineers have more disposable time and $$ than any of us. From a 155 cc port they increased port volume on the Vortec street truck heads 170cc and kept low end torque , more hp and as good a flow as their smaller port "Bowtie" heads on a small 350 ci motor that needs to pull trailers etc in a truck so bottom torque end is important. They are the budget performing iron head out there for factory SBC over their older race Bowties and Turbo heads for only 350 ci motors, stated in the article.

The LT4 heads are a whopping 195cc port on a 350 warrantied STREET motor not a 8000 rpm race motor- were the GM designers way off the mark? They still had to have good velocity and effeciency for all the legal emissions stuff and be performance oriented. If the size totally killed velocity they would not have used the big ones.I'll bet their dyno cell time was enormous testing these and others. So I think the GM engineers show here port CC is not the entire story, just a part.

The aftermarket has improved on that in port shape,size and chambers also.As the Car Craft(and Chevy Hi perf articles it was taken from show) some smaller ports can flow more than bigger-it's in the shape not only the size-a big variable I've pointed out here!!!Most of the aftermarket manufacturers have guidelines for cc size. there are 235cc SBC heads recommended for 406ci SBC, these have the same bore and stroke as a 400 Pontiac and aren't considered too big for that motor, and they are lower rpm torque motors, not higher rpm motor like 350s.

So back to the original start of this thread will a 310 cfm KRE head have loss of velocity and performance that can be felt on a street car over a 320 cfm KRE head. I don't think any of us can definitively make a correct answer unless we do a back to back testing on a single particular combination. A 310 or 320 cfm head is already out of the same parameters as any iron D port, and we don't know the difference in cc size.

[Larry Navarro]

Lets not forget the engineers designed better chambers and utilize fuel inject on those modern SBC heads for improved torque.
Its NOT just the port to consider in this comparison.

apples to oranges.

[Skip Fix]

Larry The 170 cc Vortec and 195 CC LT4 are both EFI heads, same bore same stroke, so no apples to oranges there. Bigger than earlier lower performing SBC EFI TPI heads 163cc, so no apples to oranges. All are EFI SBC heads and the last generation was the biggest!If bigger hurts they wouldn't have kept going that way at all. "The LT-4 is substantially different from the LT-1 casting, and the flow numbers explain why. The larger intake ports are definitely a contributing factor. For a production head these babies put up some pretty good flow numbers. " Obviously the GM engineers did not think bigger was bad.

These Vortec heads are used even in carbed motors and pick up over the earlier smaller heads(what Car Craft said and why they are common in factory iron head restricted classes with carbs) so you loose the apples to oranges there also, carb to carb motors. " This head can be seen as a sleeper when compared to other GM production heads. It outflows the LT-1 aluminum Corvette head on the intake side, plus its mid lift numbers are very impressive. This head is perfect when iron heads are required. GM designed this head and put it on trucks as well as on the later Impala SS but with a different intake bolt pattern. As for production pieces these are one of our favorites."


The EFI just makes a more even fuel curve than a carb as teh computer smooths out the circuit transitions rich is still rich , lean is still lean. Good jetting on carb with the same AFR will be close to the same as an EFI dialed in the same AFR. As many dyno have shown torque and HP aren't that dramatic a change just a smoother curve. If it was that dramatic alot more Sportsman class cars would be using it vs carbs.

No more apples to oranges than Jim's vs Cliff's motor ,but they were described as such, which had dramatic difference responses to the same cc port. Cause and effect-if the ccs were the only factor both motors should have lost bottom end and performance equally. They did not, what is the other explanation then???Some one set me straight then. If ccs/velocity are more important than airflow why did Cliff's make more power across the board on the dyno and go faster at the track? What is the engineering reasoning behind those actual numbers? No one has come up with that yet here. Larry you're an engineer if a piece works fine in one application and does not in another is the design of the piece incorrect or the application? You look in failure analysis what were the difference in appications.

Some people think Holleys to Demons are apples to oranges or both to a Q jet.

As I said each combination is unique in itself and "apples to oranges" to the next guy's unless all the components are the same as Jim has said.

[Jim Hand]

Skip,
If you think the results from Cliff's install of his new KRE heads disproves, conflicts with, or otherwise casts doubts on what I have discussed on this thread, I believe you must have missed reading one of my posts above. Will repost the info here and would like you to respond to these items/questions specifically. And did you know that Cliff had some traction problems that disappeared after he installed the new heads? That tells me he saw the same low RPM power loss as I did in some measure!

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

[Larry Navarro]

Geez....its ALL a "fruit salad".....pass the cool whip.

[Skip Fix]

Jim as I mentioned before this whole discussion was based on 310 vs 320 cfm heads that none of us have the rest of the basic combination sought after, obviously as much apples to oranges compares 310 to your 260 cfm heads as Clifs 220 to your 260. Totally different also then. Is a solid street roller a stroker motor , 505 ci considered in this combination that may need more than 260 cfm-we don't know! Your own combination has proven it needs more flow than Pontiac engineers designed into 6X heads. So his combination might need more air flow over yours, as yours does over stock heads! So we just don't know. We also don't have the cc diffeence in the 310 vs 320 cfm -what cc is the minimum to make defnitive noticable velocity difference on any Pontiac head-do we know? Do these have les than that-again another question.

I compared your short block with a fairly close cam duration to Cliff's both with iron heads simnilar casting, both with iron intakes and both with Q jets. If those combinations are that far different I then put out his thinking of using 310 cfm heads is going to be totally different than yours also, and we have to look at all new parameters.

I still think the variables of aluminum vs iron, compression ratio add a variable in your own testing that many experts(Smokey Yunick included) admit loses horsepower 1 point of compression is the widely accepted guidleine. You didn't stay with that the KREs had much less that 1 full point. So you have an added variable in the testing if we are just looking at port size could also be a facor in the loss. Why can new cars can run close to 11:1 on 93 octane-aluminum heads. The equivalent 6X-4s ported big and ported small are the only way to reduce the other variables.

Now to answer your direct questions:

"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!"

Jim as I've stated I think there are enough components in Cliff's combination even his driveline that are similar enough for most of us out there to consider they are similar. But as I've stated I don't disagree the KREs did respond poorly on YOUR car as compared to your similar flowing iron D ports that are smaller, no doubts. I have agreed in certain parameters a smaller equal cfm flowing head will be more effecient, I think the blanket statement that a smaller port on all combinations is incorrect. Cliff has had excellent performance history to compare to also with his previous setup. So we agree here on multiple points.

"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?" " How do you know that smaller ports wouldn't have made it even quicker?"

I'm sure Cliff knew the change would affect all of those parameters, I can sure assume it would also. Are you saying Cliff and I that unknowledgeable that a big change in heads won't affect things like velocity and airflow? But IT WENT FASTER! Can the increased airflow with a bigger port make up for the decreased flow of a smaller higher velocity port- I think Cliff's results definitely can show that definitively or he would have stayed the same or gone slower. Who cares if the velocity is a little less-IT WENT FASTER! Are they as good as the same flow with smaller port and better velocity I agree with you probabaly not(we get into port shape fuel mixture, chamber design variables here as any head designer will attest), but Cliff didn't use your heads on his combination. He used larger but better flowing KREs and went signifigantly faster-my main point! The airflow it needed can make as much or more impact as the loss of velocity.

Could Cliff's have gone faster with your heads-I never said it wouldn't!! I have never disagreed with that possiblity once. Do you have velocity reading to compare percent slower on your tested heads? Was it over the entire port or just certain areas or percent? Not normal testing for most of us, but that's the ONLY way to actually document the change in velocity- as any engineer or scientist would say -you have to measure to tell for sure there was a change. No documentation no change. What percent velocity is lost with what cc increase in size? Idoubt anyone has numbers for Pontiac heads in this area. Dave Vizard had a nice port map of velocity for a SBC in one article.


"And did you know that Cliff had some traction problems that disappeared after he installed the new heads? That tells me he saw the same low RPM power loss as I did in some measure!"

If that is consistant track to track then yes it means some bottom end was lost, BUT if you loose some bottom end and hook better to go much faster is that bad? IT WENT FASTER. Does it mean around town the car is a dog? With the 60 ft it still has I don't think so. Shoot I've picked up traction and 0.2 seconds too with no changes in combination because of track prep, and lost the same, a different variable in the mix.

Lee Atkinson on his 455 iron heads 231/239 @ 0.050 cam when borrowing my RPM over his Torker II felt the slightest bit of a loss with the RPM on the line-does that mean a dual plane loses to a single plane in the bottom end-I think others have felt the opposite.The times he ran were almost identical, so just a bottom end "feel".

I still think Cliff's results can show that if the airflow is needed the car can go faster(fact,measured) with bigger heads even if they are not the Perfect head. Finding that perfect head for that combination is a difficult task, you've done it for yours. I think Ray and many of the other heads up racers would even laugh at a 350 cfm 240cc port and say they need much more flow for their Pontiac like the Tiger , or High Port KRE heads will provide to be competive.The working parameter there is to go faster period. As John Kaase showed that can be done and beat the other makes with overall useable torque and HP with a Pontiac.


I still haven't yet seen an answer how Cliff can go signifigantly faster over the weight change if his overall perfomance was hurt with big heads. If its the more airflow -we agree then airflow can beat out imperfect velocity. If something else let me know so I can be enlightened.


Like all us guys hope, size isn't everything!

[JSchmitz]

I would think that Cliff has dyno sheets for both of his combo's. Lets assume that the iron heads made more low end torque, but less horsepower, than the aluminum heads. Pretty safe assumption. At some point the torque curves crossed. What rpm? His car leaves at around 3 grand. Similar to Jim's car. So, for there to be a loss in short track times, due to torque loss, it would have to be between the launch rpm and the intersection of the two torque curves. It's hard to imagine the small change in port volume affecting the torque at that high an rpm. For Jim's car it would be a 9 percent increase in port volume. Then again, Jim said he (Cliff) had traction problems with the other heads. So, maybe it wouldn't accurately reflect the change. But, my point would apply to Jim's car. The torque loss, that would affect e.t., would only be between the launch rpm and the intersection of the points. Does this make sense? Also, as has been pointed out, port volume is a good rough indicator for comparing two heads. But, there are many more port attributes that affect performance. No one even mentions exhaust ports. A port could be shaped like a funnel. It would have huge volume and tremendous velocity at the end. Not good!

[Cliff R]

Interesting discussion, seems like my particular combination is getting a lot of coverage, so I'll throw out the exact numbers to eliminate confusion.

Our 6X-4 heads flowed right at 232cfm ("bowl hogged"/valve and seat work here on my equipment, very minor blending at the short turn and a gasket match at the intake port.....no porting in the runners aside from knocking out bumps/flash and minor smoothing with a sanding roll), it made 455.4hp and 528tq on KRE's dyno. My heads were not nearly as good as Jim's, the single simple reason why we saw greater improvments. His heads were simply able to move more air and still use smaller runners than the KRE heads. For our 6X heads, the chambers were 91cc, CR about 10 to 1. With the KRE heads, 10.48 to 1, 494hp/549tq, no other changes.

In the car, the best ever 60' times prior to the head swap was 1.69, almost all runs netted 1.71-1.73. With the KRE heads, we ran consistant 1.67-1.69 60' times. With the old heads, best ET was 12.05 at 111.99mph. Typically the car would run 12.30's to 12.60's at Norwalk, the 12.05 run was at VSMP at sea level. After installing the KRE heads and no other changes, we went 11.79 to about 11.84. MPH from 113.60 to 114.20.

We raced with the KRE heads for a full year, and managed 11.64 @ 115.30 for the best run in near perfect track conditions, 60' time was 1.65 (new M/T ET Street Radials) most runs were in the 11.80-11.95 range for the entire year as we had an incredibly hot/humid summer.

My personal assessment of the KRE heads. There is more power at every rpm by the "seat of the pants" evaluation, the dyno also reflects this. Idle quality improved, from the higher static CR and probably some due to the improved chamber design. The engine is equally as smooth right off idle, if there is any loss of part throttle power at low rpm's it is not detectable. I DO feel a loss of low rpm power if a 1" spacer is added, and the track times reflect this with slower 60' times, but we run almost 2mph faster (back to back test).

I may not "feel" any losses off idle and low rpm's simply because we have the cam advanced to 109ICL, and the car is relatively light, 3760lbs with driver, it moves out pretty easily at light throttle. It is also very finely tuned, the carb and distributor settings are perfect, I've never driven a fuel injected car that was eually as smooth for "normal" driving.

Recently, we managed to extract some additional power from the combination, it took a hydraulic roller cam and RPM intake to do it. The info is posted on our cam testing thread. We certainly learned a lot from it. Many folks wonder why we stuck with such "small" cams and didn't simply install a 250/260 flat solid or much bigger hydraulic roller? No doubt we would have seen more dramatic increases in the peak power numbers. Even so, the goal is to increase power in the rpm range we run the engine in, NOT to make the "big" peak power numbers for bragging rights. Any loss or shift in power was not wanted, we leave the line just over 3000rpm, shift around 5000rpm's and go through at 5100-5200rpm's. Leaving "softer" and finishing harder isn't going to cut it, and we were NOT up for any gear and/or converter changes. Also keep in mind that we are testing the unported version of the KRE heads, not the ported versions as mentioned in this thread. Next time around we are up for some port work, but that's at least a year if not two out.....Cliff

[Skip Fix]

JSchmitz- I did mention that the intake exhaust ratio may change between the heads and warrant a different cam(not addressed in the swaps) split.It seems to get lost in the discussion also as intake port voulme seems to be the only factor looked at here.

Cliff has just stated the 60 fts were slightly faster, seat of the pants was better, idle was better, no sluggish feel on the bottom end with the bigger KRE heads-so where is the loss due to poorer velocity? The added airflow needed by his motor made up for it. Maybe a 455 ci motor sucking on a 185cc port changes the actual dynamic results.

Back to the orignal question we stil only have a 190cc port for the 290 cfm KREs nothing for 310-320s.

[Steve C.]

No tech mumbo jumbo, just simple minded here....

what I was getting at on my question to Larry regarding his hogged out heads was not about the impact on his vehicle track performance. Apparantly it has been proven here that Larrys torque production has been impacted with his larger runner volume heads. I was after a opinion about his "seat of the pants feel" regarding any streetability issues because of his loss in torque. Again I will suggest that there is none and his engine is smooth right off idle, and loss of part throttle power at RPM's is not detectable.

My car used to have the potential to run a 10-second time slip. But with the recent change and developments its now a 11.50 second car, an obvious difference in track performance. Yet I can stand and look anyone in the face and suggest the same situation exists as what Cliff stated, If there is any loss of part throttle power at low rpm's it is not detectable to me, dispite the loss in power that effected my track performance. It feels like the same car to me just driving around from stop light to stop light.

But what I really do miss is the feel of power winding it up to 6000 rpm....
this lower rpm weezing out and going around shifting at only 5500 rpm's is boring as heck