[Jim Hand]

Intake Tests
May 4, 2005

Went to the local NHRA drag strip in Kansas City, MO last evening (May 4, 2005), and completed testing on my modified iron stock intake vs my modified Performer RPM.

Briefly, the RPM was about .05 second quicker and .3 MPH faster. Full details follow.

The test vehicle is my ’71 LeMans wagon with a 473 CI engine, T-400, 3.31 rear gear, Continental “tight 10” converter, and MT ET Street radial tires that are 28” tall by 11” tread width. With friend Kevin Kirk driving, the as raced weight was very close to 4075# with the stock intake, and 4060 with the RPM.

The engine has 10.08 CR, runs exclusively on 92 octane pump gas, has a 234/244/112 hydraulic cam made by Bullet Cams (to duplicate the no longer available Wolverine 5059), Rhoads variable lifters, HS 1.65 rockers, a Cliff Q Jet, 6X heads ported by owner to approximate 260@.55, and with 170 cc port volume. The engine is shifted automatically at 5500 RPM in both gear changes. We staged last night at 2000 RPM, and the converter “hooks” at 3200-3300.

Each intake has been especially modified/optimized for this car setup. Both have very similar mods to the plenum divider – the idea is to retain the great primary throttle feel and response of a true dual plane intake, but provide some of the added carb flow of a single plane. The cutouts between the secondary throttle bores allow air to flow from both sides of the carb when the secondaries open, just as does a single plane. The spacers are home made. We have found through extensive previous testing that optimum carb calibration is identical for both intakes.

The test procedure was simple: Drive in off the street with the iron intake on, unload any loose items from the car and make enough runs for a consistent baseline. Then install the RPM and repeat. It turns out we only had to make two runs each, as you will see below.

RESULTS:
MODIFIED IRON STOCK INTAKE:
First run:
1.62 60’, 7.31/93.36 1/8, 9.59 1000’, and 11.55/115.13 1/4

Second run:
1.63 60’, 7.33/93.42 1/8, 9.61 1000’, and 11.56/115.17 1/4

MODIFIED PERFORMER RPM INTAKE;

First run:
1.62 60’, 7.28/93.84 1/8, 9.55 1000’, and 11.49/115.51 1/4.

Second run:
1.63 60’, 7.29/93.70 1/8, 9.57 1000’, and 11.51/115.42 ¼

The average differences were;
None for the 60’ times
.035 second/.37 MPH in the 1/8
.055 second for the 1000’
.055/.30 MPH for the ¼

Most analysts would read those numbers as “statistically insignificant”!

In true power evaluation, deduct about .01sec/.1MPH for the 12-15# lighter weight of the RPM.

As we have always found in our intake testing completed since 1992, all intakes are RPM sensitive. Each design works best when the engine is loaded in a certain RPM range that is compatible with that intake design. The stock intake is designed for best power between idle and 5400/5800, depending on engine size. The RPM is factory rated for 1500 to 6500. All intakes will “work” or “run” at any RPM, but all have a design range where each will develop the most average power. And average power, not peak power, is the important factor in making our street/strip cars drive and run best. This is not necessarily true of a real race car/engine however, as the race car engine spends most of its time at the upper RPM range.

In this case, the relatively long time my engine spends at lower RPM (due to the 3.31 gears and heavy weight of the car) makes the RPM work harder in that lower RPM range. But the mid and upper RPM range we run is well within the Performer RPM design range. The result is similar launch capabilities with the intakes, but a little better power at the higher ranges with the RPM intake. That is evident by the slight improvements in both ET and MPH as the car moves down the track.

We had been running an original 041 grind cam (230/240/113.5) until this season. The car with otherwise similar setup, including the iron stock intake and Q Jet, except about .2 less CR, ran a best of 11.67 with that cam. In back to back tests, we have seen between .07 and .1 second ET difference and .6 to 1 MPH difference between the 041 and the 234/244 cam.

Photos of these two intakes are posted at:

http://forums.performanceyears.com/g...1/m/4121083811

None of this is meant to rate intakes, nor how to build your car. But I have been interested to see how the two intakes compare after I added a bit more airflow with the 6X heads to compensate for the change from 462 to 473 displacement. Now I know!

Jim Hand

[Jim Hand]

Intake Tests
May 4, 2005

Went to the local NHRA drag strip in Kansas City, MO last evening (May 4, 2005), and completed testing on my modified iron stock intake vs my modified Performer RPM.

Briefly, the RPM was about .05 second quicker and .3 MPH faster. Full details follow.

The test vehicle is my ’71 LeMans wagon with a 473 CI engine, T-400, 3.31 rear gear, Continental “tight 10” converter, and MT ET Street radial tires that are 28” tall by 11” tread width. With friend Kevin Kirk driving, the as raced weight was very close to 4075# with the stock intake, and 4060 with the RPM.

The engine has 10.08 CR, runs exclusively on 92 octane pump gas, has a 234/244/112 hydraulic cam made by Bullet Cams (to duplicate the no longer available Wolverine 5059), Rhoads variable lifters, HS 1.65 rockers, a Cliff Q Jet, 6X heads ported by owner to approximate 260@.55, and with 170 cc port volume. The engine is shifted automatically at 5500 RPM in both gear changes. We staged last night at 2000 RPM, and the converter “hooks” at 3200-3300.

Each intake has been especially modified/optimized for this car setup. Both have very similar mods to the plenum divider – the idea is to retain the great primary throttle feel and response of a true dual plane intake, but provide some of the added carb flow of a single plane. The cutouts between the secondary throttle bores allow air to flow from both sides of the carb when the secondaries open, just as does a single plane. The spacers are home made. We have found through extensive previous testing that optimum carb calibration is identical for both intakes.

The test procedure was simple: Drive in off the street with the iron intake on, unload any loose items from the car and make enough runs for a consistent baseline. Then install the RPM and repeat. It turns out we only had to make two runs each, as you will see below.

RESULTS:
MODIFIED IRON STOCK INTAKE:
First run:
1.62 60’, 7.31/93.36 1/8, 9.59 1000’, and 11.55/115.13 1/4

Second run:
1.63 60’, 7.33/93.42 1/8, 9.61 1000’, and 11.56/115.17 1/4

MODIFIED PERFORMER RPM INTAKE;

First run:
1.62 60’, 7.28/93.84 1/8, 9.55 1000’, and 11.49/115.51 1/4.

Second run:
1.63 60’, 7.29/93.70 1/8, 9.57 1000’, and 11.51/115.42 ¼

The average differences were;
None for the 60’ times
.035 second/.37 MPH in the 1/8
.055 second for the 1000’
.055/.30 MPH for the ¼

Most analysts would read those numbers as “statistically insignificant”!

In true power evaluation, deduct about .01sec/.1MPH for the 12-15# lighter weight of the RPM.

As we have always found in our intake testing completed since 1992, all intakes are RPM sensitive. Each design works best when the engine is loaded in a certain RPM range that is compatible with that intake design. The stock intake is designed for best power between idle and 5400/5800, depending on engine size. The RPM is factory rated for 1500 to 6500. All intakes will “work” or “run” at any RPM, but all have a design range where each will develop the most average power. And average power, not peak power, is the important factor in making our street/strip cars drive and run best. This is not necessarily true of a real race car/engine however, as the race car engine spends most of its time at the upper RPM range.

In this case, the relatively long time my engine spends at lower RPM (due to the 3.31 gears and heavy weight of the car) makes the RPM work harder in that lower RPM range. But the mid and upper RPM range we run is well within the Performer RPM design range. The result is similar launch capabilities with the intakes, but a little better power at the higher ranges with the RPM intake. That is evident by the slight improvements in both ET and MPH as the car moves down the track.

We had been running an original 041 grind cam (230/240/113.5) until this season. The car with otherwise similar setup, including the iron stock intake and Q Jet, except about .2 less CR, ran a best of 11.67 with that cam. In back to back tests, we have seen between .07 and .1 second ET difference and .6 to 1 MPH difference between the 041 and the 234/244 cam.

Photos of these two intakes are posted at:

http://forums.performanceyears.com/g...1/m/4121083811

None of this is meant to rate intakes, nor how to build your car. But I have been interested to see how the two intakes compare after I added a bit more airflow with the 6X heads to compensate for the change from 462 to 473 displacement. Now I know!

Jim Hand

[slowbird]

How much time would you say you have in porting each intake? Do you think you will ever test the new Tomahawk intake?

[Jim Hand]

SB,
My car work is a hobby. I can manage to make a 10 minute job last for hours (sometimes by intent, and sometimes by accident!). But essentially, the ports on both intakes are opened to the gasket size. And the cutdown section on the RPM divider is minimal work.

The stock intake obviously took more time - it has evolved over the years with work done at different times. But it has been a great development tool to learn about intake theory.

The new single plane intake appears to have been designed for higher RPM performance. I would expect it to work similar to the original Torker and Dominator. And both cost my car significant performance. Accordingly, I will not be trying it on my low RPM setup with street 3.31 gears.

Jim Hand

[Half-Inch Stud]

Jim,

Excellent data record, and performance. Thanks.

Can you describe the Q-Jet Top-plate (Part-Throttle Enrichment Circuit or not), Mid-body stamping #, Pri rod/jet.spring, Sec Rod/hanger?

Primary Baseplate angle that initiates the Secondary opening if you got it.
.
.
6x EXH-crossovers are aluminum filled..right?

Some day, maybe this year, I gets to run the Offyl Dual-Q-JET DUAL-PLANE for a pump-gas data point. HIS

[Half-Inch Stud]

Jim,

Even thou you got a 1/4Ton more and 1/2sec faster, I'd suggest you don't be too shy on the Tomahawk.

Still gots me 1 TorkerI left, so I PLAN to evaluate the Dual-Quad against that Baseline.

If a fella handed you or me a Tomahawk and carb...why not.

Paintless in PA. HIS

[slowbird]

Have you done much porting in the runners on the stock intake besides the port match?

[Jim Hand]

SB,
When I work on the runners, I open them to full gasket size, and that includes as far up the runners as is necessary to maintain that size.

HIS, since there is no data on how the new intake runs on a car, and especially on a heavy low RPM car, we should reserve all comments until we see such data. However, the theory of intake operation does not change. Large diameter runners with relatively short lengths will favor high RPM operation. And while I have not seen one in person, it appears that describes the new intake.

Jim Hand

[455firebird1969]

Jim,

I have opened my @62 heads intake openings to the Felpro 1233 gasket size. My RPM intake runners are untouched, in other words the intake runners are smaller than the head openings. I did this because my theory is a smaller intake runner feeding a larger head opening will not hurt flow or performance.

What is your opinion on my theory?

I do not think opening up the intake runners to match the 1233 gasket size will help.

Thanks for sharing info...

[Jim Hand]

455FB69,
It is a good plan to keep the intake runners just slightly smaller then the head port openings. That makes it easier to align the intake.

However, the real concern is the airflow through the entire intake system of carb, intake manifold, and head intake ports. Most would be shocked at how much most intakes attenuate the head flow!

So by enlarging the intake runners, just as was done with head porting, we can find more system flow. The real key to all of this is how much total airflow your engine needs. If your complete intake system is furnishing enough air as is, enlarging the intake runners will make no difference in how it runs.

You are correct that opening the head ports to a taller gasket size makes very little difference in head airflow. I carefull ported four ports on one head to 250 with standard gaskets. I then cut the ports to the tall gasket size and blended it well back into the port. The difference? Only one cfm average @ .55!

However, with most of our intakes, the air has to make a sharp turn at the intake/head junction. And it appears that raising the port/runner opening at that junction does help air transfer from the intake to the head. So if added airflow is needed, that enlargement may help a little.

HIS, I want to clarify my comments on the new Tomahawk intake. It will fill the needs of a lot of cars that don't have room for current performance intakes. I admire the guys who are fighting to get it out to the customers. The point I tried to make is that various car/engine combos need a range of intake designs for best performance of each. As my car is setup for max grunt early in RPM, and needs to maximize it through the mid-range, I suspect the dual plane will do it as well or better for my specific setup.

Jim Hand

[mchell]

Jim,

You should market the design of your modified cast iron intake, in aluminum of course. What I like about your modified cast Iron intake is :

1. Modified Duel Plane design
2. Water Crossover removed
3. Has a PCV port
4. Has Exhaust crossover ports removed
5. Ports Modified for somewhere between race and street
6. Readily accepts Qjet throttle linkages
7. Low height

Where can I buy one??

[grandville455]

Excellent info Jim!!! I agree with mike you should market that design of your's into a aluminum version ..I know I would buy one How much did you gain by just cutting the secondary's open?

[Jim Hand]

GV.
I can say with certainty there is no Al version of my iron intake originating here!

The odd ball pieces and slots in the RPM are a result of various tests of fully open divider, fully closed divider, and the present partially open divider. The last provided the best gains and is a solid .06 to .08 difference in ET.

While that amount of ET change may not sound impressive to folks looking for changes in seconds, it is very significant with a good running car. And it is essentially free with no down side in drivability or reliability.

Jim Hand

[Darrell]

Thanks Jim excellent information!
I know this is going out on a limb but Jim could I buy a template from you to trace on my intake and spacer? I am afraid I will screw up!!! I want to do your modification from the book in the worst way. I am taking pride in not going to a aftermarket intake staying with iron heads and using a Q-jet.

[Larry Navarro]

As usual...great info Jim!
I have yet to tweak the divider on my RPM but hope to do so very soon.

[Jim Hand]

HIS,
The Q Jet I use was prepared by Cliff Ruggles. It is PN 17057232. I was running 74 primary jets with .041 primary rods, and custom made .038 secondary rods. The hanger is a "K" model.

I have been known to clip/stretch the primary rod spring to find desired operation, so no idea what it might be. Additionally, the part throttle adjustment used on the later model carbs has been adjusted for optimum street performance.

That is about all the info I have readily available on the carb.

Jim Hand

[Bill Eveland]

Thanks again Jim for posting your results.
Would the same modifications be beneficial on the later egr intakes as well? Is the secondary opening the only major drawback to these intakes and have you done any airflow testing on the egr intakes with opening up the secondaries? I was thinking of working with my extra egr intake I have for a 9.5:1 400 street engine with unported 670 heads, 230 duration /480" lift. Thanks, Bill.

[PMDRACER]

Thanks for sharing the info Jim!

[Silver Judge]

Thanks for this excellent info
You are very kind to share your knowledge and experience, this is a great supplement to the info in your new book which we all have of course

[Rocky Rotella]

Bill, not to hijack Jim’s post but we performed a flow comparison of several stock intake manifolds. The results appeared in a 2-part article in consecutive issues of High Performance Pontiac magazine a few months back. In that story we compared a ’67 iron, ’68 iron, 71 aluminum, 73-74 iron w/EGR, 73-74 SD-455, and a 75-79 style. We concluded that with head flow in the 210 cfm range (typical of most d-ports with 2.11 intake valves), no one manifold was noticeably better than the others. This included the restricted secondary 75-up manifold. As head flow increased, however, we saw the manifolds with the larger runners (the aluminum RA/HO and SD-455) flow more air than the other d-port manifolds.

Keep in mind that the “D” shaped secondaries can only be a restriction if they reduce the amount of air the engine wants to consume. And unless you have a high winding engine with heads with increased airflow, I don’t think this manifold would measurably affect performance. So with the unmodified d-port heads in your combination, it should perform the same as any other stock or similarly modified early manifold.