5.0 Rebuild

[smittys7up]

Hello,

First time poster and excited to be here.

Picked up my first Mustang - 1990 5.0 with a 5 speed a few months ago. It appears to be a 7up edition but have not verified this. So I've only drove it about 45 minutes home after the initial purchase and then around the block a couple times. After parking it I found a decent amount of oil leaking onto the ground, and most of the engine, trans, underbody seems to be saturated. With winter now set in here in Michigan I figured this is the time to tear into it.

So upon pulling the motor I've found the valve cover bolts to be finger tight lol. Assuming this was the source it since oil was caked all over the engine bay. I've picked up some Explorer parts including upper/lower intake and GT40P heads. I mocked up a set of BBK shorty equal length headers and they may work with 90 degree boots. I also have a B303 cam, 24lb injectors w/ calibrated MAF on the shelf. I have read the A9L ECU can handle these sort of changes, I hope this is true. Just going for a close to stock or mild build.

So today I disassembled the GT40P heads. Need to extract the broken intake bolt I found. But other than that, the disassembly went well. I tried cutting a deep well socket and using my drill press to remove the valve springs. Definitely paid off. I do have the hand crank spring compressor tool and after doing 1 spring by hand I'll go witht eh socket/drill press method from here on out!

I'll attach some photos of the car/engine/heads. I did a dry and wet compression test and then a leak down at 100psi. I'll attach those notes as well. Figure the results weren't horrible and the car was running fine, but any opinions on the results or anything else is this build are welcomed! Would hate to miss some simple stuff while I'm this far in.

TIA
Jake

 

[Mcmahst]

Welcome. Nice find. Should be a fun project. Good luck.

 

[gkomo]

Keep us posted with progress and pictures!

And yes I believe the stock computer can handle all that you have planned.

Hell I ran a H/C/I 331 with 24lb injectors and calibrated MAF, no ‘tune’ or chip, just the stock A9L and it ripped.

 

[revhead347]

Looks like a really clean car. Are you going to change all the gaskets on the engine while it's out. I'd do a rear main seal, a nice one piece oil pan gasket, front seal, etc.

Kurt

 

[AeroCoupe]

Timing chain, new oil pump with pickup and hardened ARP oil pump drive shaft. What are your plans on the GT40 heads? At a minimum you will need some decent springs for the cam. If you have not already thought of this then these are probably the most common setup for a stock iron head:

https://www.trickflow.com/parts/tfs-2500100#overview

 

[Praetorious]

Man what a nice car,the interior is in great shape,body is straight and the paint looks good too, for what i assume (by your location) is a northern car it must have been garaged most of its life cause it still has its body,lol, what a fantastic winter project.

I used to have one of those hoods on my 91 but mine didn't have the grilled inserts, not sure why i got rid of it but its been a couple of decades,
i wish you lots of fun with the car and the guys here are top notch when it comes to knowledge, they got you covered.

 

[Noobz347]

This is just for reference and includes my current list of off-the-shelf cams for GT40P upgrades.

I included the B-303 in the last line just as a reference to the others.

Oh, and I assumed a 3:55 rear end gear (N/A setups respond very well to this).

302 / GT40P Street Cam Reference Table​

Camshaft	Duration @ .050"	Valve Lift (Int/Exh)	Recommended Springs (GT40P-friendly)
Trick Flow Stage 1 (TFS-51402000)	221° / 225°	.499" / .510"	Comp GT40/P spring kit or Alex’s Parts Max Output II
Comp XE264HR (35-349-8)	212° / 218°	.512" / .512"	Alex’s Parts Max Output II kit
Lunati Voodoo 20350711	221° / 229°	.549" / .565"	Lunati LT73100K2 or LT74820K1 spring kits
AFM N-41	~222° / ~232°	~.512" / ~.512"	Alex’s Parts Max Output II (for lift margin)
Ford E-303 (M-6250-E303)	220° / 220°	.498" / .498"	Comp GT40/P spring kit or Alex’s Parts Max Output II
Ford B-303 (M-6250-B303)	224° / 224°	.480" / .480"	Comp GT40/P spring kit (easy clearance)

Notes (Important for a GT40P + 3.55 build)​

1 “Best match” for your combo?
With 3.55 gears, long-tubes, and GT40P heads:
Trick Flow Stage 1 or Comp XE264HR will feel perfect on the street — fat torque, EFI friendly, no drama.


2 Lift limits on P-heads:
Above ~.510" lift, check retainer/guide clearance.
The Lunati cam is a monster, but you’re into “measure everything” territory.


3 B-303 vs modern grinds:
The B-303 is useful as a comparison point — but the newer profiles absolutely walk it in torque and drivability.


4 Idle personality ranking (mild → rowdy):
XE264HR → E-303 → TFS1 → B-303 → N-41 → Lunati
- The last two generally require a tune.
- None of these setups require 24 lb injectors so, save yourself some money. Even if you have them, it will run better on 19s without a tune.
- If you add boost later, you'll likely need some #42+ injectors.

 

[nickyb]

I'd be a little Leary of those compression numbers, seems like 20% .

 

[Noobz347]

I'd be a little Leary of those compression numbers, seems like 20% .

Send It!

 

[smittys7up]

I'm sure it was fine to "send it" as Noobz347 suggested lol.
The block just went out to get honed, crank polished if needed, mic'd for bearings, degreased etc.. It all looked clean and probably recent rebuilt. Only thing that stood out was the amount of carbon and build up on the pistons.
I found a double roller timing chain and cam stamped '0319'. Also #6 rod was missing and replaced with another #7 rod and cap.
Noobz347 - I'm agreeing with your cam choices, thank you for the detailed info. Think I'll sell the B cam and pickup a TF Stage 1.
Is there a recommended rebuild kit for 1990 roller blocks, or recommended rear main seal and bearings?
Keep the great info coming guys!

 

[Qtrhrse23]

How many miles? Those pistons ARE CLEAN IMO for a 36 year old. YES 36 years.

Whats wrong with the stock cam? Everybody WANTS the chop chop, but cam wont give you alot more power, AND the stock cam drives so smooth. But since you are rebuilding, I guess my arguement is MOOT.

 

[Qtrhrse23]

Good move on the cam change. I HATE THOSE (4 LETTER WORD) LETTER CAMS.

So its been rebuilt before, thats why those pistons look like they did.

Looks like you know what you are doing, BUT pay attention to the little stuff. Like oil pump shaft direction AND head gasket oreintation. AND lifters before heads. Things like that.

Speedpro pistons are fine with regular ring package, but a more expensive piston with thinner rings means less friction AND less heat.

I usually do Felpro 1011-2, 1250, 1415. Head intake header gaskets.

 

[keel]

Noobz347 - I'm agreeing with your cam choices, thank you for the detailed info. Think I'll sell the B cam and pickup a TF Stage 1.

+1 for the TFS1 cam, I've got one in my car and it's awesome. Great sound and driveability, even with no tune.

 

[smittys7up]

+1 for the TFS1 cam, I've got one in my car and it's awesome. Great sound and driveability, even with no tune.

Stock ecu and injectors? What other parts are you running it with?

 

[keel]

Stock ecu and injectors? What other parts are you running it with?

Stock bottom end with GT40 intake manifold and GT40 3-bar heads with upgraded valve springs. I ran it for a few years like that with basically everything else stock (injectors, throttle body, airbox/intake, MAF, ECU) and it ran good.

I recently went to a bigger throttle body, calibrated MAF, and 24lb injectors and it probably picked up some but to be honest my butt dyno didn't feel any difference.