[Jim Hand]

Pontiac intake port too small? Depends specifically what RPM range you want to run! They are certainly not too small for my application.

Pontiac Dude just addressed that subject in a recent post at:

http://216.178.81.108/forums/showthread.php?t=497831

See post 4.

While he was speaking about airflow, in order to change airflow, port volume/cross section will invariably change also.

Jim Hand

[gearbanger]

Jim, I had never seen that information put together just that way before. I would suggest you lost performance because you switched from iron to aluminum and didn't increase the compression ratio enough. It is pretty well accepted that you need a full point more compression with aluminum due to the heat dissapation of aluminum. It's too bad you hadn't gone to 11:1 with your compression. I bet you would have had different results. You were probably about on the edge of being able to use pump gas with your origional combo, but the KRE headed combo would have probably run fine on 87. I just don't see it as a fair comparison of the KRE d's. Still good info, and as always, I love to read about your testing. Very scientificly done.

[ponjohn]

Jim- with the al. heads on your engine, even with the bigger cam is it possible it was still starving ( need bigger cam and non factory intake -rpm?) - hence the poor performance?

[70 lucerne lemans]

Ron H,are you running 93 octane?Im calculating my compression ratio closer to 11.5 to 1 with the KRE 74 cc ,zero deck 468.Hoping to run 93 octane or mix some 100 with it if I need to.

[Jim Hand]

John,
Are you asking that if I had changed the engine and car to run higher RPM, would the heads have worked better! Just as explained above, an engine needs a certain amount of airflow to run to a certain RPM optimally.. And airflow over and above that will make no difference in power. However, in order to get that excess airflow, the ports will have to be enlarged, and that most certainly will affect engine power.

And I did not get "poor" performance from the KRE heads - to the contrary, they performed very well indeed. - best of 11.69/115.5. But just not as good as the small port iron heads did!

I didn't install the heads with the idea of retooling the car to optimize the performance of the heads. I installed them in order to have new modern trouble free parts that would also remove a bit of weight.

If I had wanted to change the RPM range of my engine and car, I didn't need to buy new heads - I could have simply ported my iron heads for more flow and bigger ports!

Incidentally, I was running the RPM intake at all times with the KRE heads. And the cam I was running was my regular cam of 234/244/112, and not the 041. the new custom cam was specifically designed to add the low RPM power lost by the bigger port s on the KRE heads. And it did that, but unfortunately a 108 LS cam of only 233 degrees also quits making good power much earlier in RPM then a 112. Accordingly, what it picked up in the lower RPM, it lost in the upper RPM, besides idling much worse!

Jim Hand

[Ron H]

I am at 4400'. My pistons are .012 in the hole. I have SRP pistons -8cc eyebrows. 4.181 bore, 4.121 stroke.
I will be 50/50 112 with 91 for racing. Otherwise on the street I am ok with normal driving. Though I did detonate a bit on a run this morning again.
Being in Florida I bet you will have to run at least straight 104 unleaded or a 50/50 110 or 112.

[ponjohn]

poor vs the 6x heads.

[Bruce K]

It's difficult to have your cake and eat it too. I for one have noticed a difference from 6x to E-heads. With the ported 6x's and the small roller 224/230 low rpm throttle response was incredible. Now with the big cam 252/262 and 235cc E-heads [email protected] the engine is not happy below 1500 and is lazy up to around 3000 rpm.

I am still trying to work out some carb issues (with a lot of help from shaker455ho) to help idle and off idle response. Even in a perfect world it will not be like the old combo.

Would I trade and go back, I don't think so! The rush from 3750 to 6000 rpm is worth the price of admission. I can deal with a higher idle and a little bucking if I fall asleep and try to drive it like the old combo. The engine is more comfortatable at 2500-3000 rpm cruise than the other engine was. It doesn't make any more temperature than the other engine, but is a lot harder to start and keep running when cold.

It won't cruise happily below 1500 rpm in top gear, more like 2000 to really get things flowing. Even if it did, I would never try to accellerate hard from that low of an rpm in 4th gear. That's what lower gears are for at low speeds.

The Car and Driver 30-50 mph top gear acceleration - what a joke. If I trusted anyone enough to drive my car and they did that test, that would certainly be the last time they drove any of my cars.

I can just see myself going 30 in 4th and pulling up to a Corvette or Viper and nailing it.lol And then they test an auto vs a manual. What a useless test, how about a 30-50 in 1st or second gear, that might be a meaningfull test.

Forgive my ranting and back on the subject. It's all what you want, I happen to enjoy the 12mph I picked up in the 1/4, btw, I think it will be more like 20mph when I'm done tuning, and am willing to give up some of the low rpm friendliness of milder combo. Life is about tradeoffs and think if someone wants that feel of hp and the feeling that your engine wants to keep pulling hard up top it is a worthwhile tradeoff.

[Skip Fix]

Jim I know you don't want to turn much rpm over what your motor does now. Your goal has always been to stay under that 5500 rpm ceiling. That's fine and you've gone as fast as anyone else with your strict guidelines.Alot of good tuning got you there and intelligent selections. I know you've gone even faster with yours in a different configuration. We all have goals and what we want out cars to do, look like. Mine is to keep a Shaker on the motor and go fast on pump gas and be streetable, I don't think there are too may out there that can stay up. I probably could pick up with a Victor, but that looses my main guideline. I'm not arguing that the KREs ran slower on your car or that yes increasing rpm range you could have gone even faster. That wasn't your goal and they didn't meet your needs.

Jim you may not have done it as a head test BUT I think almost EVERYONE here read into your results that the 185cc ports were why it ran slower, and because of their slower velocity and no other variables were possible. "As a result of the loss of low and early mid range power due to the larger ports on the KRE heads" Right there it says the big ports are the only potential problem! It was very strongly implied that any motor with similar cam range(within 3 degrees @ 0.050), D port heads, intake, carb would also NOT benefit from the change using the bigger ports because yours did not. Cliffs is as close to your combination as possible other than not the same exact heads with the same exact flow. OK cam was 3 degrees different @ 0.050. Which is virtually impossible unless we use CNC ported iron heads.Hence the comparison, and discordant results, and no loss in bottom end feel. In fact Cliff's less ported heads should have had smaller ports than yours and gone even slower. Other folks are also going faster. So it is not just the port size for every car! Most other ported D ports that flow similar to yours are going to be closer to 180cc so probably less velocity, so no way are anyone else's going to perform the same as yours using the same logic.

Variables -Put a 6X-4 head next to a 6X-8 and a head gasket against both. They aren't the same chamber. So if your before ported iron and after D ports were different castings we have the potential for a variable. Recent magazine tests even question our 1 point difference in aluminum vs iron compression. But no one questions the loss of heat and HP in an aluminum head vs iron head, unless barrier coated at the saem compression. So that is one vairable on yours eventhough you tried to keep the compression a non variable. So even different castings are a true variable. You can't striclty say the port size was the factor on yours!teh different port shapes in even the ported iron heads much less the KRE head's different shapes add a variable to the cylinder filling independent of the port cc! The chambers are an extention of the port and affect that also and are different so another variable.


I go back to Pontiacs round port vs D port 455 port size which you have never even commented on. How did Pontiac keep their rpm range similar if 30cc impacts them that much, or did the increased flow or different chamber do it? The same difference in the KRE and your heads and fewer other variables. What's the reasoning here?


OK we will approach the concept small ports flowing the same as big ports. You will know all of this as well as I, as much as you read, it's not that simple! or I guess I'm just really dense!

Velocity theoretically would be increased, BUT if it too much vleocity we make fuel fall out of suspension, packing the cylinder with air and less fuel/air combination needed for HP. Most head gurus, Vizard included, feel getting close to sonic speed velocity is BAD. What is the velocity in a small port on a 465ci motor when running? Will ALL the air in the port be able to make all the short turn at the higher velocity? Or will some of it collide or tumble making flow go backwards, easily heard on the flow bench. Vizard has mapped velocity in SBC ports and reccommends porting more in those areas-do we know that for a Pontiac port? Which head's port? What is the velocity in your ports and in what areas? As I've stated before I'll be we don't have a map for any of our heads like Vizard has done. Do you know the velocity was slower over more of the KRE port than your 6X port? That's what we are assuming based just on port cc.

Why are the NASCAR, Pro Stock etc big guys finding even identical flowing , identical sized ports run different? They must run the same but they don't.That's where they go to the wet flow bench. Tom S even talked of having his RAVs wet flowed. Just the slightest difference in port shape chamber shape adds a variable into that and they can see it on the wet bench. On hand porting I'd bet even variables between different cylinders.

I had 4 totally different cams in the RAIV 400 and ALL ran identical to the 0.01 times & mph, only one killed the streetability and increased rpm range needed, a big solid. Different variables were at work.The cam was one, the exhaust header another.

[Skip Fix]

Here's what Lynn just mentioned regarding velocity regarding a Pontiac Iron head with only 180ish cc

"The biggest positive in a race engine will be to keep the maximum flow velocity to 614 feet per second to minimize splitting the fuel out, and not choking down the intake charge.

My SS 455 engine calculates obout 769 fps in the push rod area. It seriously limits horsepower, RPM. "

So to much velocity is a bad thing also!

[Jim Hand]

Bruce,
Exactly! Everything is a tradeoff, and what suits one may not suit another. And that is the beauty of our hobby.

But as this is an information board, all of the related information needs to be posted on any subject, and that is what I am attempting to do with facts, figures, references, and reliable comparisons.

Jim Hand

[Bruce K]

Jim, I have been reading your articles and posts for many years now and will continue to do so. I and I'm sure most here have great respect and gratitude for the time and energy that you have put forth and your willingness to share information is totally unselfish. You could put what I know into a thimble compared to what you know, but I am working on my 4th engine combination now and just thought that I would relay some of my observations to the board. Thanks, Bruce

[Jim Hand]

Gearbanger.
I have also heard that al requires one extra point of CR. However, I have never found one test that has been made that confirms or even hints at that much difference. In fact a recent test by Car Craft magazine tested an iron and an Al head from the same company with all variables on the heads, including CR, as identical as was possible to make and guess what! The two sets of heads made identical power even with the same CR!

If you know of documented tests and/or results that confirm that one full point is required to make equal power, please advise as to where they are and how we can access them.
Thanks
Jim Hand

[Ron H]

I think they just posted that in the Dec Hot rod that you have to make 1 more point of CR with aluminum to equal Iron. I will go home and read it now to confirm.

[Jim Hand]

Skip,
Just curious - at what RPM does Lynn apply a load on his engine, and at what RPM does he shift?

And did you look at the referenced material by David Vizard? I presume you did and you feel his testing is incorrect!

Jim Hand

[speedshopmike]

i believe the aluminum head "1 point rule" is that you can go a point higher in compression with aluminum vs iron heads with otherwise the same combination - ie, more detonation resistant due to the surface heat sinking faster then iron heads.

[JSchmitz]

Originally Posted by speedshopmike

i believe the aluminum head "1 point rule" is that you can go a point higher in compression with aluminum vs iron heads with otherwise the same combination - ie, more detonation resistant due to the surface heat sinking faster then iron heads.

You beat me to it. So, If you can run another point, why not?

Jim, mill the heads and put them back on. We'll give you two weeks to come back with a full report.

[gearbanger]

Jim, the test would be the octane test. If you have to run supreme in your iron head combo, but your aluminum head combo didn't need that. Cliff's car ran quicker and faster with 89 than 93 with 10.5:1 compression.

I think the results of the test that you were talking about is probably because the aluminum heads had design features that improved the performance enough to offset the heat disappation effects of the aluminum. Had they raised the compression of the alum heads to have equal fuel requirements as the iron head, I feel sure that the aluminum head would have outperformed the iron heads.

In your case, your iron heads had been optimised for your combo and 93 octane fuel, so the improvements that the KRE heads have were not enough to fully offset the difference in fuel requirement. You simply needed more compression to exceed the performance of you iron heads. And that would have easily been possible with the aluminum.

[Skip Fix]

Jim I've read Vizards articles. He HAS mapped velocity and measured it. I don't think we have on Pontiac heads.few shops I've been to have a velocity manometer. I've read other experts that agree in some areas and disagree in others. His articles often are abbreviated in different magazines. The same general articles appear in different magazines with different additions or subtractions. Many others now use the CSA(cross sectional Area) instead of port volume to determine how a motor will respond.Intake runners or exhaust pipe cc are just port extensions so they add more variables that CSA. A longer dual plane runner wil make a different total cc than a shorter single plane, but shorter than a M/T crossram.In fact most experts now use that much more than port cc for intake as well as exhaust.

The Pontiac engineers did NOT loose streetability adding 30cc intake port volume. If that is the case why did these motors not loose torque and street manners? Were they wrong? I'll bet they spent alot of devlopmental time and $ testing a totally new port and chamber. Were the factory ratings wrong and really the HO/SDs had less power? They would have to using only port volume/velocity theory we are here.

Yes Lynn uses high rpm compared to your 460 motor but less that other brands in his group. That still does not refute the fact that the cylinder head experts feel too much velocity is bad in whatever rpm range you run for the reasons he and I both mentioned.I believe even Vizard has mentioned that somewhere.

Let's ASSUME your D port motor has 50 more ft lbs at 1000-1800 than my E head motor, but at 2000 its only 10 more, at 2500 I'm 10 above and climbs greater diffeence from there. How much driving/acceleration is in the 1000 to 2000 range? How fast does the motor acelerate through that range? Is the Kaase motor with its huge ports and 100ftlbs over both of our motors at 2500 going to be a no streetable? Maybe because it roasts the hides too easily.

You are also leaving exhaust ports totally out of the equation. Most experts do NOT,including Vizard! It is an average of intake CSA rpm range and exhaust CSA rpm range that determines where the motor likes. What were the CSAs on the intake ports, exhaust ports, exhaust port ccs? All of those also are a big factor.

You still miss my point, there were many other things in your test besides the intake port size that could have affected performance that may or may not affect other motors performance in a similar manner.

Are you stating that port shape, chamber shape do not affect mixture filling in the cylinder but only size does?

[Ron H]

I read though that way of thinking has changed. They said instead of you can run more, you have to run more to equal an Iron head.