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Trick Flow Series R to Box R Upper Intake Road Block

  • Thread starter Thread starter Habu135
  • Start date Start date Mar 31, 2026
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Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
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Apr 25, 2026
#41
  • Apr 25, 2026
  • #41
Here is a steel 2" cowl:

Mustang 2" Steel Cowl Hood (87-93) - LMR.com

Improve the look and engine bay clearance on your Fox with this 1987-1993 Mustang 2" steel cowl hood!
lmr.com
 
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Habu135

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#42
  • Apr 25, 2026
  • #42
Noobz347 said:
Here is a steel 2" cowl:

Mustang 2" Steel Cowl Hood (87-93) - LMR.com

Improve the look and engine bay clearance on your Fox with this 1987-1993 Mustang 2" steel cowl hood!
lmr.com
Click to expand...
Thanks guys, but I want to retain the stock look of the notchback and that includes the OEM style hood.
 
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Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
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#43
  • Apr 25, 2026
  • #43
Habu135 said:
Thanks guys, but I want to retain the stock look of the notchback and that includes the OEM style hood.
Click to expand...

It was as stock as I could think of and still accommodate your intake.
 
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nicholase

I lubed and pushed, until it was all the way in
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#44
  • Apr 26, 2026
  • #44
Habu135 said:
Worked on getting the troublesome Box R upper to fit under my stock height fiberglass hood (sans cross bracing). I was able to remove the adjustable fuel pressure regulator to get the Box R to sit flat on the lower intake, but the hood won't close with the 1" aluminum Trick Flow mating plate. I utilized a 3/8" spacer which is the thinest that will work with the stock fuel line connectors which otherwise will rub the belly of the Box R. So I'll need to have the 1" aluminum plate milled down to 3/8", or even better 1/4", but also add 1/2" spacers between the frame and k member when I install a tubular k member which will create problems of its own. Maximum Motorsports references these here:

Some considerations when installing spacers between the k-member and the chassis:
• Ground clearance may be reduced.
• The position of caster/camber plate strut shaft spacers may need changing to maintain the strut's proper compression travel and droop travel.
• Transmission mount may need modification to maintain proper driveline angles.
• Pinion angle may need to be adjusted to maintain proper driveline angles.
• Steering shaft will need to be extended slightly (easily accommodated by an MM telescoping steering shaft).
• Front suspension geometry may be altered, with possible consequences to the car's handling.
• A front-end alignment will be necessary.

All of this work is for what, 10-15 more horsepower in the high rpm range? I'm struggling with if it's even worth it.


Click to expand...
It sounds like you have figured out exactly what you need to do for it to clear under the stock hood, which is good work. I like the stock hood profile myself, so I understand that take. Shimming the K member for hood clearance seems like a big hoop to jump through, one of those "the juice isn't worth the squeeze" situations. But if you have to have it, go for it, we've all been there with something.

I'm not super familiar with that intake. I'm assuming its a trade off so to speak. Less low end torque traded for high RPM HP? I think I'd be able to walk myself off that just by telling myself I'd rather have the low RPM benefits for the street.

I thought your old intake looked great BTW.
 
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Habu135

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#45
  • Apr 26, 2026
  • #45
nicholase said:
It sounds like you have figured out exactly what you need to do for it to clear under the stock hood, which is good work. I like the stock hood profile myself, so I understand that take. Shimming the K member for hood clearance seems like a big hoop to jump through, one of those "the juice isn't worth the squeeze" situations. But if you have to have it, go for it, we've all been there with something.

I'm not super familiar with that intake. I'm assuming its a trade off so to speak. Less low end torque traded for high RPM HP? I think I'd be able to walk myself off that just by telling myself I'd rather have the low RPM benefits for the street.

I thought your old intake looked great BTW.
Click to expand...
Thanks. Yes, shimming the k member is a must if I want to attempt (key word here *attempt*) to make the Box R work with a stock style hood. And I may find a number of other issues as a result of the 1/2" shim. That intake will cause a slight loss in low end torque. The great mystery is how much horsepower I'll gain from the Box R. If it's 12 horsepower, going from 401 RWH in my current setup to 413, I'd argue all the additional work and cost isn't worth it. Lots to think about and I appreciate all of the responses.
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
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#46
  • Apr 26, 2026
  • #46
Did the OEM FPR not fit in there without the spacer or was there something else that made the spacer necessary?
 

Habu135

5 Year Member
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#47
  • Apr 26, 2026
  • #47
Noobz347 said:
Did the OEM FPR not fit in there without the spacer or was there something else that made the spacer necessary?
Click to expand...
The Box R upper has no attachment points (holes) in it and requires the 1" aluminum spacer be bolted into it. The spacer has the attachment points. The spacer obviously raises the upper up from the lower clearing the FPR and passenger side fuel coupler. I'd have to mill the spacer down to 3/8" or 1/4" or go whole hog and buy aftermarket fuel lines and an adjustable fpr, but the hood would still hit the front of the Box R.

The little things, OEM fpr and fuel lines, can be worked around. It's the stock hood that requires the engine be lowered and that creates a whole set of problems in itself.

It comes down to the question, "Is it worth it?" Is 10-15 additional hp above 4500 RPM worth it from the installation of the Box R.
 

AeroCoupe

lube between the nut and the face. I know my lubes
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#48
  • Apr 26, 2026
  • #48
You are not going to notice going from 401 rwhp to 413 rwhp on the street especially for the time and money you are going to spend to get it. I mean a CAI or some other bolt on to get 15 hp is low hanging fruit. This whole intake thing is something I would just walk away from or in my case buy a hood but I like a small cowl. It really sucks that this is not just a direct swap but its not like you are at 225 hp any more either.
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
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#49
  • Apr 26, 2026
  • #49
Habu135 said:
It comes down to the question, "Is it worth it?" Is 10-15 additional hp above 4500 RPM worth it from the installation of the Box R.
Click to expand...

I get ya. I had some similar issues trying to shoehorn the Kenne Bell under the stock hood.

I ended up going with a 2.5" Cervinis. I didn't have a ton of options since I'd just put a brand new Long block with a 7qt oil pan in.

Watching to see what you come up with.
 

Habu135

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#50
  • Apr 26, 2026
  • #50
AeroCoupe said:
You are not going to notice going from 401 rwhp to 413 rwhp on the street especially for the time and money you are going to spend to get it. I mean a CAI or some other bolt on to get 15 hp is low hanging fruit. This whole intake thing is something I would just walk away from or in my case buy a hood but I like a small cowl. It really sucks that this is not just a direct swap but its not like you are at 225 hp any more either.
Click to expand...
I was leaning toward waiting to make a decision on this, but if I pivot to my next mod (MM K member and adjustable front suspension) I'll obviously need to do the spacers at that time.

The idea of 1/2" spacers between the frame rails and k member and all the drama that goes with that just annoys me.
 

Habu135

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#51
  • Apr 26, 2026
  • #51
Noobz347 said:
I get ya. I had some similar issues trying to shoehorn the Kenne Bell under the stock hood.

I ended up going with a 2.5" Cervinis. I didn't have a ton of options since I'd just put a brand new Long block with a 7qt oil pan in.

Watching to see what you come up with.
Click to expand...
My Ford Racing Z2363 has the 7 quart oil pan. When first installed, my mechanic put 10 quarts in it as the oil dip stick from Ford was not cut to the right length for the Z2363 engine oil pan. That was a headache trying to figure out why oil was gushing out of the engine at high rpm.
 
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Noobz347

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Apr 26, 2026
#52
  • Apr 26, 2026
  • #52
I marked mine for 6 quarts and keep that as my [full] line.
 
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Habu135

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#53
  • Apr 26, 2026
  • #53
Noobz347 said:
I marked mine for 6 quarts and keep that as my [full] line.
Click to expand...
I drained mine and noticed it was much more than the oil pan quantity. Added 7 quarters, cut the dip stick stalk to length and then called Ford Racing to inform them. Another reason why my daily is a Honda.
 
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TOOLOW91

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#54
  • Apr 27, 2026
  • #54
When you start to mill that spacer you have to watch the upper intake getting Into the distributor cap especially with that big ass stock distributor.

All this to me is not worth on your comvo going from a standard r upper. I doubt you’re going to notice any difference
 

Habu135

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#55
  • Apr 27, 2026
  • #55
TOOLOW91 said:
When you start to mill that spacer you have to watch the upper intake getting Into the distributor cap especially with that big ass stock distributor.

All this to me is not worth on your comvo going from a standard r upper. I doubt you’re going to notice any difference
Click to expand...
Ugh. New fuel lines, adjustable FPR, new distributor, and all the corrections to the suspension and driveline based on adding 1/2" spacers between the frame and k member. Even with all that, the TPS, which is the highest point on the engine, may still not clear the hood.

I'll likely back away from this and focus on the k member and adjustable suspension. I should be able to pick up a few hp just by increasing my overall timing from 32 degrees to 34.
 

Habu135

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#56
  • Apr 30, 2026
  • #56
I'm going to take another crack at this, because ultimately I do want to install this intake and I believe IT IS doable with a stock height hood and OEM height k member.


I was researching past posts on the installation of this intake and stumbled across this Corral.net article from 2018.

https://www.corral.net/threads/trickflow-r-upper-vs-trickflow-box-r-upper-actual-dyno-test-and-analysis.2515434/

Within the post, the author "engneer" talks about gaining 33 horsepower by adding a Box-R intake over his old R-Series on his 331 engine with 190 heads. How did he make a 1 1/4" taller intake fit under his Miata hood? He purchased online and utilized a 3/16" adapter plate https://docs.google.com/forms/d/e/1...thuYNgjruB5kfJ4O853BSsy2Y5BlSA/viewform?pli=1 rather than the 1" plate the Box-R came with. Additionally, he ground the base of the Box-R in order to get the taller 12 1/4" Box-R the same height as the 11" R-Series. This created some additionally problems in itself, but since you all have been so supportive in helping me spend money, I'm going to ask for solutions here again on the following areas:

Distributor: the OEM Ford Mustang distributor is not compatible with a 11" tall Box-R intake. So I'll have to purchase a reduced height disturber. I know Holley makes some. For those who have done this, what is your suggestion?

Fuel system: My existing Kirban fuel pressure regulator hits the underside of the Box-R. A Standard Ignition non-adjustable fuel pressure regulator is considerably shorter, but still hits the underside of the Box-R. I understand I'll have to bend the fuel pressure regulator base plate downward to create more room. Additionally, the fuel pressure return line coupler hits the underside of the Box-R. Other than purchasing aftermarket fuel lines, I suspect much of the return line could be bypassed completely by cutting it and connecting a fuel rated rubber hose from the regulator base to just behind the alternator (see photo). This would give the Box-R underbelly the additional room needed to sit flat on the lower intake without rubbing anything else. If this is unwise though because of the threat of fire, what would be the better option.




So that's it, I believe. Purchase a new reduced height distributor, tweak the fuel pressure regulator downward and remove the return line coupler connector.

If my existing 11" R-Series fits under my stock height hood, then logically a reduced height 11" Box-R would have all the same throttle body and fuel linkage attachment points and should be fine.
 
Last edited: May 1, 2026

Habu135

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#57
  • May 1, 2026
  • #57
TOOLOW91 said:
When you start to mill that spacer you have to watch the upper intake getting Into the distributor cap especially with that big ass stock distributor.

All this to me is not worth on your comvo going from a standard r upper. I doubt you’re going to notice any difference
Click to expand...
TOOLOW, please tell me what distributor you went with for your Box-R install and what, if any, issues you had. Stab and plug? Or what?
 
Last edited: May 1, 2026

AeroCoupe

lube between the nut and the face. I know my lubes
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#58
  • May 2, 2026
  • #58
I would just cut both ends off and have some steel 6AN fittings welded onto them. Find a reputable tig welder and that should be a piece of cake. Then buy these adapters to go from the stock lines to 6AN (other companies make them as well):

https://www.russellperformance.com/ford-return-side-efi-x-6an-fitting-with-black-finish-640873.html

https://www.russellperformance.com/...i-x-6an-fitting-with-black-finish-640903.html

So what I am talking about here is ditching the two hard lines between the fuel rails and the lines they attached to down under the passenger subframe in front of the shock tower. Use the adapters plugs some 6AN fittings and braided 6AN hose to connect to the 6AN adapters on the stock fuel lines and the 6AN fittings you have welded to the stock fuel rails. Black hose and fittings would look really good in my opinion.

Remember, you said to spend your money.
 
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TOOLOW91

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#59
  • May 4, 2026
  • #59
Habu135 said:
TOOLOW, please tell me what distributor you went with for your Box-R install and what, if any, issues you had. Stab and plug? Or what?
Click to expand...
I have a Holley dual sync distributor which will not work with your stock ecu

I built a car for a friend of mine with a box r and stock distributor as well
 

Habu135

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#60
  • May 4, 2026
  • #60
TOOLOW91 said:
I have a Holley dual sync distributor which will not work with your stock ecu

I built a car for a friend of mine with a box r and stock distributor as well
Click to expand...
I have the Holley Terminator X ecu. How much shorter is your distributor? I suspect I'd have to go your route distributor wise if I reduced my Box R's height by 1.25 inches.
 
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