[J.C.you]

how much would Ray pay for another .10th? i just mite see a .10th somewhere......he he......

[Region Warrior]

Originally Posted by J.C.you

how much would Ray pay for another .10th? i just mite see a .10th somewhere......he he......

Well, the way i understand it, once we have the baseline back, then we can pill-it-up

[Larry Navarro]

Originally Posted by ponchoshop

...What got my attention is mine flow more air with less turbulence up to 600.
The wide ports go further of course, but at a slower velocity.

Very interesting.
Race engines too.

[Skip Fix]

Larry, "with less turbulence up to 600." is one of the key statements.

For street or race QUALITY airflow is the deal. Depending on the shape of the sometimes increase the increase in velocity can induce turbulence which can be counter productive to flow, sometimes it doesn't. It can happen in smaller or larger ports. With the lower port floors our Pontiacs have turbulence is something even Pete McCarthy noted in porting iron heads years ago, I've got a set of 62s I've ported that the low lift numbers are gang busters, but at .450 they go into turbulence and decreased flow. Most heads do decrease in flow with turbulence,if Ray's do go into turbulence some reshaping could remove that and increase the flow. You can hear it on the flow bench when they go into turbulence. Why I quit porting heads! Why some other makes of heads can have good numbers and small ports alot easier, and why the higer port aftermarket heads of many makes(and factory Z-11 409 heads ) flow more without going into turbulence as easy-port shape-no low floors and tight short turns. Better porters like Jim Hand and Dave Sober can get the flow and keep out the turbulence.

[Larry Navarro]

Yes, I(we) know Skip....it's been discussed countless times.
those ports on my #16's look pretty good but, turbulence occurs a little higher than your #62's.

276cfm@.550"

264cfm@.600"

[Skip Fix]

In fact in talking to one head guy recently he felt once the velocity starts getting over 300 ft/sec and definitely at 350 ft/sec all the air just can't make the turns it needs to , and for sure the fuel suspension can't. That's why teh high end guys are using wet flow benches. But as many experts atest we really can't measure what velocity is on a running motor.So is our test at 10", 28" what is really seen in a running engine?

The actual velocity in a running engine has to change constantly as the piston speed changes. A 455 has alot different piston speed than a 400, a 400 Pontiac with its longer rod, different from a 400 Chevy with the same stroke. Even the larger ported Pontiac E heads aren't much different than a GOOD SBC head. That SBC that has less ci, less piston speed to cause actual velocity on the motor to be less than a Pontiac motor would see. My bias thinking.

Back to back testing on a particular engine like Jim and cliff have done are the only way to tell which head will work better for their combination.

I'll help you dial in the carb , but pulling the heads off with the motor in a F body is one "fun" deal I've had too many times!

[Larry Navarro]

Originally Posted by Skip Fix

The SBC that has less ci, less piston speed to cause actual velocity on the motor to be less than a Pontiac motor would see. My bias thinking.

...lets not forget, the SBC needs to REV(greater piston speed) alot faster than our Pontiacs do.
7000 to 8000 RPM is RARELY an occurance on the street.

[Jim Hand]

Skip,
You can attempt to excuse it as many times, and in as many ways as you want, but the fact is my 473 cube engine lost low and mid range power with 186.5 cc ports as compared to 165 cc ports. We shift at 5500 so don't need big ports and the big airflow to run well.

And Cliff did not make a "test" of effects of port size! He simply switched from basically stock iron heads to new fresh stock KRE heads. The combination of new heads, more CR, superior chamber design, better airflow, and lighter weight made his car run quicker and faster. But it proved absolutely nothing about the effects of port volume/size on his engine!

Incidentally, do you feel the fact that the new Chevy small blocks inject fuel into the ports at very high velocity and in the optimum location has anything to do with the design of the current crop of Chevy heads? And maybe that port volume, and possible fuel dropout, is not quite as critical on such setups as with our 40 year old Pontiac design heads? And that much newer port design with optimum shapes can be designed into brand new engines/heads, whereas our stock heads, E heads, and KRE heads still have to have ports that fit into the 40 year old exterior design? In other words, the design, size, and shape of modern head ports of any make have little or nothing in common with our Pontiac port design and optimum sizes!

Jim Hand

[amcmike]

So Jim, what your telling us is that you made an 267cfm with 170cc ports after you published your book? (Since the KREs were still in development as of that writing.)

Do those of us loyal purchasers who paid our $20, get an addendum to the head porting section?

Or even better, head porting by Hand, so I know its right? (I can ship tomorrow).

[OLDFLM72]

I asked last weekend! LOL

V/R,
TY

[Jim Hand]

amcmike,
As you could expect, the porting instructions in my book are fairly conservative, and the work presented and described are from following the instructions. The flow results were then measured and reported - no re-work or fine tuning was done to inflate the numbers.

There is so much variation in wall thickness, interior rusting, and casting alignment, what might be a safe spec on one head could be a disaster on another.

Yes, I have re-ported my 6X heads to 267 @.55 with a port volume of 170, but did it after I tried the KRE heads. I opened up the bowls to about 1.72-1.73 and blended the new size well down and into the short turn. Widened the short turn a little more. Carefully blended/rounded the 50 degree seat blend cut to the actual seat. Pared a little more off the head bolt bulge. Raised the roof of the port opening to 2.17". And as opposed to what I mentioned above for the book exercise, there was some trial and error and rework, as well as lots of measuring! All of this makes the job more risky and closer to water in the ports. I can take the risk, but would hesitate to suggest it to others via my book. Nowever, I was able to get these numbers without breaking into the push rod bulges! Rounded and smoothed and narrowed but no sleeves or breaks! The eight ports average 264 @.5 so they are pretty much full of air at .5 lift, and don't increase much as the lift goes higher - an indication that the port is about as small as possible for that amount of flow.

No addendum planned but a "hearty" thank you for having confidence enough to buy the book!

Jim Hand

[OLDFLM72]

I asked last weekend! LOL

V/R,
TY

[blaktopr]

With all these changes, was the csa at the pushrod increased also? Or is that the same, except for how far in you raised the port. I am curious on how these heads work based on the changes in the shape through the port rather the flow increase.

[Skip Fix]

Jim, I'm not excusing the fact your car ran slower, never have, with different heads. I even stated it probably is related to the port size but you also added other variables-aluminum head, different compression ratio, different chamber shape.So that is not the tenant for "only one change at a time" in the racing,engineering or medical fields to definitively establish cause effect. Four changes I count, but the ccs probably the biggest , but we can;t tell for sure.

I can list a long number of others, including Cliff's car that went faster with bigger ports, KREs or E heads than they did with D ports that were smaller, and didn't always loose bottom end. How can we deny Cliffs car went faster with 185cc ports when it did low end and big end? Cliff stated he didn't change the rpm dramatically either, low rpm torque motor! If cc defintively kills bottom end and over a small cc pocket ported head didn't make it have to use high rpm how does that not show they do not kill bottom end in all motors? What is the explanation of how it did not go slower, that was as much a cc change as your engine Jim? And yes I did say it could have gone faster with a smaller same flowing port, but it still did NOT loose measureable bottom end with the bigger ports.

Are we then saying the Pontiac performance engineers made big mistakes with the HO and SD 455s and they are only high rpm motors? I'll bet most out there aren't shifted high.These have those 185cc ports too. Larry you have always stated once tuned your SDs and HOs had plenty of low end torque even with the bigger HO cam, were they shifted at 6000+? Where were the factory HP peaks listed onthese big port motor, high rpms? I think the factory ratings compared to D ports can show as much an apples-apples on head cc changes as your motor did Jim. They were all factory prepped the same from Pontiac with the same imperfections, and had more HP.

I currently have a 360 hp(conservative dyno) 383 SBC 240/250 @ 0.050 hydraulicin a Camaro that has a HP peak of 5800 rpm,and that's with a Victor single plane. I can lug it in second gear(stick)autocrossing and has plenty of bottom end power. As OTHERS besides me have added in other posts 383 and 400 SBC have the same stroke as a Pontiac 400, the 406s same exact bore and are torque motors in scale with Pontiacs.They aren't HIGH RPM motors any more than a 400 Pontiac has to be.

Jim, the Vortec 170 cc Chevy head is on a basic 45 year old design, poorer valve angles (23 degrees) that our Pontiacs and picks up cars with carbs as the Car Craft article stated. Not fuel injected motors. These new big port heads are on the GM CARBED crate motors.Just pull up their site and see what rpm the torque and hp are even on a small 350. They have a 383 crate motor with these heads check it out. From GM 383ci 340 hp @ 4500, 435 ftlbs 4000, bigger cam single plane intake 383 Fast Burn heads 425 hp @ 5400, 460 ftlbs @ 4500,Fast Burn 350 ci 385 hp @ 5600, 385 ftlbs @ 4000, bigger cam 425 hp @ 6000. Big ports, 40 year parameters on locations,much smaller ci, carbs no EFI! No heads totally designed for EFI manifolds,GM dyno numbers.

www.gmgoodrench.com if you think I'm fabricating numbers here.Then you can look at the article Jim footnoted on head ccs for their heads.

All of these rpms are the same or LOWER as Jim's 470 CI peaks at, with as big or bigger heads and 100 less CI! I think this can just as easily show that big ccs don't require high rpm even on a smaller motor, as well as the Pontiac HO,SD series if we only include Pontiacs.

The DART, Brodix etc 23 degree heads still live with the basic SBC angles port locations etc and make plenty of bottom end torque in 383/406s. The data from alot of others is out there easily accessed. Alot of build ups showing these motors using 215cc + heads are still low rpm motors. Go to some of the dyno guys see what they've seen. Bottom end torque motors can be SBCs too. There have even been 454 SBC in magazines also.

[blaktopr]

Instead of the back and forth stuff guys, how about looking at this a different way. OK, we have port cc, port flow, rpm ranges and....... Skip, you messed with these other motors, take a look at the ports from all the manufactures. They all look different. They can be close in cc size and close in flow cfm, But their shapes are different. CC's....., how about whats their csa's and where. Ever wonder why a Pontiac uses a 2.11 valve, and a chevy sb 2.02 or 2.05? Why does some pontiac heads stall and others not as much, from .450 lift to .550? Do we all REALLY know why the RA4 head is so good?
And Skip, what heads are you running with that 383 combo? ( literally)

[JSchmitz]

I think we have to be careful when comparing port volume from one make, or engine, to the next. Unless the centerline length, cross section, etc., of the port is the same, it's not a valid comparison. I do agree with Skip's argument about the changes in the two cars. The flow is the only difference in Jim's "list" of changes. This, according to the theory, should have only increased the top end performance. It also should have cost short track time. There's much less science (control) here than some believe. This all seems very similar to a carburetor size debate. There are rules, but no absolutes, to this game. Combination, combination, combination.... Don't feel bad. They're still second guessing Einstein.

[Larry Navarro]

Originally Posted by Skip Fix

Larry you have always stated once tuned your SDs and HOs had plenty of low end torque even with the bigger HO cam, were they shifted at 6000+?

The ports on both of those engine were untouched and were shifted at 6000 with limiter chip. Both cars had 4 speeds. The '73 SD clone had a 3.90 gear with a 4 speed and the HO racing cam. It doesn't take much with that combination to feel some low-end grunt.
The HO motor was in the '79 with a mild hydraulic and 3.23 gear/4 speed.

Both engines had Q-jets and stock dual-plane intakes.

Compared to Dave & Lee's "small volume" D-port performance, the SD and HO motors I had, couldn't compare.

....and a comparison of SBC heads/engine to a Pontiac is irrelevant.

[Jim Hand]

blaktopr
Very little work was done at the push rod bulge. The bulge has been flattened, and the chamber side "rolled" smoothly into the wall. As the heads are on the car with the intake in place, can't measure them, but do have a similar head on the shelf with one port finished. The actual width of the opening at the bulge is 1.075". Typically, I try to open the upper part of the port to the maximum width I dare to (without breaking into the push rod opening), while not worrying as much about the lower third of the port entrance. And I did raise the port entrance and blended it in about one inch. I have finally realized the push rod bulge area is not the restriction for this amount of flow. Rather, the turn area and lower bowl area are the critical points.

Incidentally, the port entrance was raised primarily to assist in minimizing the angle from the intake into the head as the air comes out of the intake runners. And the intake runner outlets were also sized accordingly. I have tried the suggestion in the HO books to narrow the intake runner at it approaches the bulge, such that the runner outlet and port inlet (at the bulge) are roughly the same width. However, in ever case, flow through the intake and port together has dropped significantly! So I open the port opening to the dimensions noted above (2.17 X 1.15), and do the same for the intake. I have the intake "interlocked" with nylon adapters such that it is correctly aligned when the front intake bolts are installed.

But it all works - the car is just as fast as it was with the 273 cfm Al D ports, almost .2 quicker, and almost .1 quicker to 60'. And that is with the added 50# of the iron heads.

Jim Hand

[Skip Fix]

The contention here has been larger cc heads HAVE to have more rpm, and are only good at higher rpms, kil low rpms -case in point Cliff's motor-more usable performance all ranges,same overall rpm range. I think that makes the biggest case.Case in point Steve Coombs E head dyno numbers HP peak less than 6000 with multiple intakes. These are both Pontiacs as far as I can tell.

Larry "..lets not forget, the SBC needs to REV(greater piston speed) alot faster than our Pontiacs do.
7000 to 8000 RPM is RARELY an occurance on the street."

My point on the SBC heads is the same-large ports don't have to be only good at high rpm,they have as large ports as D ports and still had similar peak hps on a much smaller motor-not what has currently been stated by everyone here that the SBC with these heads are high rpm motors or only relevant to EFI motors -not so per GM specs less than 5700 hp peaks with carbs. So an incorrect statement. They are making more hp at moderate rpm than the older smaller port camle hump SBC heads!! It can still be used as an example of the theory being stated that larger has to have high rpm. Shape,quality of airflow, and increased airflow is the deal, it makes up for the vleosity loss.


Chevy to Chevy still not relevant, then apples to apples -we can compare Pontiac to Pontiac port shapes,lengths-HO/SD to D ports, look at factory hp ratings for these I listed earlier.Nothing I made up. No one here has still made a valid arguement about this.They in their untouched size larger cc than untouched D ports, and still as large as the KRE's made more hp in a moderate rpm range per Pontiac. These were the Pontiac engineers best thoughts using the Pontiac designs, and they picked bigger ports. The early SD D ports had much larger ccs also. So just saying larger is worse is not always the case, even using Pontiacs to Pontiacs in the same rpm range. Why did a mild cammed factory motor not fall on its face with 1 180cc vs a 155 cc port? What's the answer here?

If we are saying the port shape has to be the same for comparisons a 155cc Dport is going to have a different shape than a 170cc prted D port, and a 180 cc Dport, and probably even more difference in a 185cc KRE head.

Larry I'll bet if your SD or HO motor had Dave or Lee put as many hours tuning as they have their D port combinations they would have run just as fast, you'd have to ditch the stick too! If you remember not that long ago Lee's was a low to mid 12 car-got a time slip where I redlighted to him,tuning and trying different things including convertors, rollbar stiffend suspension, and a solid cam got him where the car is, making a whole combination that works.

Main point -larger ccs don't have to be bad for every combination(can be for some), they could even actually have a better quality of flow(velocity mapping over the entire port, fewer dead spots, better fuel suspension) than a smaller port of poorer design and still make as much bottom end. It's all in the combination whether its a Pontiac or a SBC or Mopar(Tom)!!!! I think as JSchmits said alot more variables than we all really can put a finger one, we just try to elimante as many as possible.

My 383 was a dyno mule I bought from my machinist-041 heads, big hydraulic cam with low lift for stock springs, Badger cast pistons 2 bolt main. He had good luck with Comp 280 and 290 cams in 383s. Not too bad a 360 hp motor for less than $1000!

[J.C.you]

Jim, was wondering if you checked the fps across the short turn apex in the kre heads? if you did, what numbers did you get compared to your heavily modified dports?