MFI Induction Chart

[Bobboloo]

I thought since the topic comes up once in a while that I would post the dimensions of the various MFI setups for the data base.

I measured all the the induction setups with the exception of the 72/73' S/RS setup stacks which I did not have available to measure. My guess is that they are they have the same inner dimensions as 70/71' S stacks.

The stacks were made of magnesium until 72' when they started making them out of plastic.

The 69' magnesium stacks had the same outer dia. on the E and S stacks. The inner bore is what is different. Same is true of the 70/71 mag stacks.


Outer diameters of the mag stacks:

69'

E & S

55mm at the top
47mm at the bottom

70/71'

E & S

55mmm at the top
52mm at the bottom


If you use the 69' stack as the limit for wall thickness. (about 4.5mm) then you can see that the 70/71 mag stacks, E or S can be bored out to be 46mm at the top and 43mm at the bottom. This is what makes them good candidates for large displacement motors. Of course, special throttle bodies would need to be built in this scenerio. i.e larger than 38mm.

The outer and inner dia. are different on all three ver. (T,E&S) of the plastic stacks. The angle of the stack varies as well. This makes the E plastic and especially the T plastic stacks not very useful for modifying for larger ports and cams. Either find the S stacks or get some mag stacks to use. Remember, the 69' stacks won't fit the later TBs' so you'll have to buy those as well.

The throttle bodies in 69' had a stud spacing of 66mm. From 70' on they used a spacing of 72mm. Therefore throttle bodies and stacks can't be interchanged between 69' and the later years. From 70' on they are interchangeable. i.e. You could put a 70/71 E or S stack on a 73' T throttle body if you wanted to.

As you will see in the chart. All the throttle bodies start with a 38mm bore and taper to their respective cylinder port. Therefore you could bore the bottom of a T throttle body from 29mm to 36mm and use it for a 3.0RS if you chose to do so.


In the chart below you see the numbers 1 thru 5. These correspond to the inner diameters accordingly.

1. Top opening of stack
2. Bottom opening of stack
3. Top opening of throttle body
4. Bottom opening of throttle body
5. Cylinder intake port.

This shows the flow pattern going down into the cylinder.

Year..69'.......70/71'.....72/73'

T

1.......n/a........n/a......35mm
2.......n/a........n/a......32mm
3.......n/a........n/a......38mm
4.......n/a........n/a......29mm
5.......n/a........n/a......29mm

E

1.......39mm....38mm....38mm
2.......35mm....35mm....35mm
3.......38mm....38mm....38mm
4.......32mm....32mm....32mm
5.......32mm....32mm....32mm

S

1.......46mm....42mm
2.......38mm....38mm
3.......38mm....38mm....38mm
4.......36mm....36mm....36mm
5.......36mm....36mm....36mm


2.4S, 2.7RS and 3.0RS all use the same MFI setup. The only difference is the space cam used on the 2.4 motors. The 3.0RS setup is identical to the 2.7RS

[Scott Clarke]

Thanks for this great post. Its long overdue!

[Bobboloo]

If anyone has a 2.4S stack and wants to measure it and post feel free to do so. I'll update the chart.

Since the plastic stacks have a flare at the top you can measure the bore by inserting a rolled up piece of paper in the top of the stack to give you an edge that you can measure. Otherwise it's hard to get an accurate measurement due to the bell at the top.

[FA-18C]

Thought I'd bump this info and also ask the guru's a follow on Q. I just picked up a very good set of 72/73E throttle bodies with the 38mm intake and 32mm exhaust bore. I have not yet pulled my 70E bodies, but they look nearly identical with the exception of a small tube at the end of each throttle body that I do not think mine has. Is this some sort of cold start system from later cars? Since I do not have this system, do i just plug this up?

Also, since I plan on swapping them out this weekend, can someone give me a quick synopsis of the steps? Is it best to remove the whole system including the injection lines etc? Also, are there gaskets between both the throttle body and motor as well as the throttle bodies and stacks?

Thanks

[Tim Walsh]

There are gaskets between the motor and t-bodies and between the stacks and t-bodies.

I belive your cold start mechanism is in the airbox.. the 72 cold start is evidently safer but I don't have any hard and fast numbers on that.

[Early_S_Man]

Chris,

If by 'end' you mean ... coming out towards the rear bumper, those two brass tubes provided vacuum, and were joined at a tee and went to the vacuum retard port on the distributor of '72 thru '76 MFI engines! Cap them off!

[FA-18C]

Thanks Warren - these throttle bodies I picked up are in great shape and i cannot wait to see what a difference they make. Any rec's on capping, just a rubber stopper?

[KevinG]

FA18-C:

I believe that the cold start system for 72/73 involved the stacks, not the throttle bodies, but of course I may be wrong.

Bobboloo:

Am I correct in interpreting that my current 2,2S MFI setup could also be used as is in a 2,7RS application, with the exception of the appropriate space cam?

[FA-18C]

BTW- not that this is a thread I saved from last July 2003 - valuable info to print and save for the MFI files.....

[Scott Clarke]

Chris-
Access to the nuts securing the throttle bodies to the heads is difficult. I removed mine while leaving the stacks in place. It can be done as long as you have good long 1/4" extensions with good quality wobbly sockets. If you can remove the stacks while leaving the throttle bodies in place, go for it. the alternative is no picnic.

Kevin-
The 2.2 space cams are not interchangable with the 2.4/2.7 space cams, so the 2.2S space cam is as close as you will get with a 2.2 pump. Gus Phister can make some internal adjustments to the pump that will ameleriorate any shortcomings of the 2.2 space cam with your 2.7. He told me that the 2.2S space cams seem to work with RS replicas, as long as you are using an S cam.

-Scott

[FA-18C]

Should get gaskets by Friday from PP, and am going to pull the system that evening. Is standard satin black paint good enough for the intake stacks or do I need a high temp paint? I do not plan on painting the throttle bodies, but would like to clean up the intake stacks prior to putting it all back together.

[spinmd]

Bobby,

Sorry to resurrect an old thread but it's what I've been searching for for the past 2-1/2 hours and 300+ posts - THANKS!

Hopefully you can tell me if my set of stacks and throttle bodies will work on my 69E engine. From your specs, I see the only difference might be the top opening of the stack if I do indeed have E stacks/throttle bodies.

I'm putting together the MFI for my '69E and have the correct pump and all the extraneous hardware, but the stack/throttle body numbers are not 1969 numbers. I have mag stacks: 911 110 301 0R, and mag bodies: 911 110 101 1R. They appear to be original to each other, i.e., never separated, but I know they aren't 1969 numbers.

Other than pure authenticity to the 69E motor, what are your thoughts on whether these will pose any problem to the operation of the engine/MFI? I may later post a new thread as to whether I should continue to hunt for the properly numbered stacks/bodies in order to maintain premium value of the car/motor combination -- any thoughts on that would also be appreciated.

Thanks!

[rswannabe]

EDITED TO REMOVE INCORRECT INFORMATION


Brooke

[69911e]

spinmd: I ran the stacks/throttle bodies from my 69E on both the original 2.0E motor and a 2.2E motor. The stacks/throttle bodies should bolt right up. I believe there is a difference in the stud spacing between the stacks and the throttle bodies. ie you can't mix 69 stacks with other year throttle bodies.
I do have my original 69E stacks, throttle bodies, and pump. Email me if you are looking for some (edbogue@yahoo.com).

Ed Bogue

[Tyson Schmidt]

The head intake stud spacing is the same from 2.0 up to 3.2.


The real difference is the stud spacing on the tops of the t-bodes for the stacks to bolt to. You can't swap stacks between '69 T-bodies, and later ones.

[rswannabe]

Sorry for the misinformation. Thanks for the correction.

Brooke

[Tyson Schmidt]

Originally posted by rswannabe
Sorry for the misinformation. Thanks for the correction.

Brooke

No problem. You were really close anyway! Easy to make that mistake.

[David E. Clark]

Please take a look at the Ultimate MFI resources thread and add your links and resources. It will make a great resource for all of us.

[jluetjen]

I recently took my intakes apart and made the following measurements which I've used to correct the data in the above table:

In the chart below you see the numbers 1 thru 5. These correspond to the inner diameters accordingly.

1. Top opening of stack
2. Bottom opening of stack
3. Top opening of throttle body
4. Bottom opening of throttle body
5. Cylinder intake port.

This shows the flow pattern going down into the cylinder.

Year..69'.......70/71'.....72/73'

T

1.......n/a........n/a......35mm
2.......n/a........n/a......32mm
3.......n/a........n/a......38mm
4.......n/a........n/a......29mm
5.......n/a........n/a......29mm

E

1.......41.5mm.38mm....38mm
2.......33mm....35mm....35mm
3.......33mm....38mm....38mm
4.......32mm....32mm....32mm
5.......32mm....32mm....32mm

S

1.......46mm....42mm
2.......38mm....38mm
3.......38mm....38mm....38mm
4.......36mm....36mm....36mm
5.......36mm....36mm....36mm

[Mr Beau]

Are there part numbers of the various stacks? Do the plastic ones have different embossed part numbers as the outer dimensions are the same?