I need help please!

Azhi23

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Oct 26, 2022
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I’m very confused on what to do and sometimes I have troubles explaining things so sorry in advance guys! So I got my hands on a 85 fox body mustang. I don’t know much about the building world but it really interests me. It has the 5.0 GT motor and it’s a 5 speed manual. I don’t know much about it however it’s a carbureted one. I bought it off my uncle after he blew the trans. It has shortie headers and dual exhaust don’t know much else. When buying the transmission I didn’t do A LOT of research I just knew I wanted to achieve at least 500-600hp so I instantly went and searched for a transmission which could hold it. I ended up finding and buying the Tremec TKO 500. However I didn’t realize I would maybe have to swap out the rear end to match with that transmission. Like I said I don’t know a whole lot of the more in depth side of it. It fast but it seems like it tops out quick and doesn’t want to push further at a certain speed but it feels sluggish to me and seems like it’s reving high. The speed cable isn’t hooked up yet so I can’t tell which speed or rpm’s I’m at right at the moment.. so for the sound of the revs that it’s giving and the speed it’s possibly going it feels like there’s still a little more it could give on the top end and that’s where it feels sluggish. It has no problem getting up to speed which is fun. It just doesn’t feel like it’s giving the same amount of juice it sounds like it could while being at said rpm’s. it kicks sideways and will burn the tires from dead stop but only a light strip a few feet I like to see it a little darker so would even setting in a different rear end give it more power to the tires? The backs are 265 width with 17” rim but I just can’t remember the sidewall maybe 45 maybe 50 not at the car right now and its 11pm while raining. I want it fuel injected, and I don’t know what I want to do if to rebuild that one and convert it or just get another motor and swap. I’m very lost. Any help would be greatly appreciated if you guys can make since of my rambling on haha.. thanks!
 
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General karthief

wonder how much it would cost to ship you a pair
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If I were in your position I would get a Ford assembly manual, you can get them from ebay for your specific year. That way you can repair and decode certain parts. Then I would look around here on stangnet (other sites too) for 85 mustang gt specific builds mostly because that is the last year for the carbureted V8.
Don't know what your budget is or the intended purpose ie: dailey driver/drag or show.
 
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Azhi23

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If I were in your position I would get a Ford assembly manual, you can get them from ebay for your specific year. That way you can repair and decode certain parts. Then I would look around here on stangnet (other sites too) for 85 mustang gt specific builds mostly because that is the last year for the carbureted V8.
Don't know what your budget is or the intended purpose ie: dailey driver/drag or show.
Thanks for the quick reply. I did forget to mention the intent on my build ha. I would like to have it so I could drive it around during the summers. It’s stored during the winter and colder seasons here in Canada. Only plays in the warm weather haha. I’m not looking to go the drag way. though I may take it maybe once just for the fun of it after the build is finished. What would be a realistic price tag to get those 500-600 numbers because I haven’t set a budget right yet. Didn’t think about it I was just going to go until I got the right set up that I felt comfortable with. The body, and frame of the car is good I’m just focusing on drivetrain and power right now, and work my way around as I go.
 

Noobz347

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I would like to have it so I could drive it around during the summers. It’s stored during the winter and colder seasons here in Canada.


I would just like to add that sure... You can cruise around in a 500 HP Fox body all day long but no matter how you slice it, you're just a throttle blip away from a scary full-blown monster that will just flat-out scare the poop right outta you.

350 to 390 HP in a 3300 lb car is a [lot]. Especially for a an ermm... 4-link with no mods.


If it were me an I were after looking for a power cruiser, I'd shoot for 400ish HP, accept 350, and put the rest into suspension, brakes, and aesthetics.

This, coming from somebody that owns a 500 HP, 3300 lbs go-kart already. :D It can be scary to drive because of what it can do... And what it can't :oops:
 
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Mstng93SSP

You have a nice rear end there Dave.
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Find out what your rear end gear ratio is. You can do this by jacking up the car and making a mark on the driveshaft (Can use masking tape). Then you rotate the rear tire ONE revolution. In that one revolution count how many times the driveshaft rotates. If it rotates 3 1/2 times, 3:55 gears. 3 and 3/4 3:73's and so on. What part of the Trudeau dictatorship are you in?
 
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General karthief

wonder how much it would cost to ship you a pair
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Well, coming from a 'long hauler' (my new term for getting old) 500-600 hp in the new rides spoiled the youngsters of today, hell a mini van or a common (what we used to call) econo-box has 325+ hp, so get real, if you want 500-600 hp you will have A: an unruly, hard to drive through a parking lot or down a residential street and you won't be able to afford, let alone want to drive long distance. B: modern engine swap sitting in your garage that you'll have a lot of money in parts and time, that's if you have the space and some fab skills, that may run with the modern econo box or mini van but now it won't turn or stop worth a damn.
The 350 hp mentioned above is good advice, it's more fun than you think when driving around town or hitting the twisties out in the country, alot less money and there are many builds here that are just like that.
If you need some help finding a few to read about we can help you out.
 
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AeroCoupe

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You need to address the rear gear situation ans see what you have in the car like Mstng93SSP said above. To expand on that (being you are new to the game) go here:


Once you have that determined then you are saying it feels like the car is sluggish. The 1983 -1985 Mustang GT came with a Holley 4180C four-barrel carburetor from the factory (as did alot of the V8 motors from the early to mid 80's) and looks like this (I just did a Google search is this site has a lot of info on this carb):


From there you need to know a few things about the motor itself. Can your uncle tell you much about the car like what intake, heads, cam and if its been rebuilt with what parts? This helps in knowing what we are dealing with motor wise.

When was the last time the engine had a tune up (distributor cap, distributor rotor, spark plug wires, and spark plugs)? You may also need to look at the fuel system to ensure you are getting enough fuel when the engine is demanding it. This would be the fuel pump and fuel filter. Fuel pump is mechanical and on the front of the motor more specifically mounted to the timing chain cover on the driver side. You should be able to see it kind of behind the power steering pump. The pump does have a return line back to the fuel tank so if you do replace this make sure you get the correct one. Fuel filter is in the Holley carburetor where the fuel line from the pump attaches.

Holley_4180C_Fuel_Filter_Location_photo.jpg


All of this is assuming the car still has a mechanically driven fuel pump and the original carburetor. We need more info from you to really go any further than this. Pictures are great and if you need help posting them just ask.

I will say that a hell of a resource is www.foureyedpride.com. Site is dedicated to the four headlight fox cars and there is a wealth of info on there. The picture of the carb showing the fuel filter location came from there.
 
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AeroCoupe

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Would also say that my Coupe has 360ish to the rear wheels and it regularly puts a beat down on today's 400-500 hp cars. They are heavy, most cannot drive them, and they are heavy. Just work with what you have and see about getting the combo sorted out and I think you will be impressed with what it will do. Again, you need to know what you have now (stock parts or did your uncle spice things up) so folks here can help / make suggestions.
 
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Azhi23

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Oct 26, 2022
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He didn’t mention anything about upgrades I only noticed the headers and performance exhaust system under the car from what my eye balls seen. Thanks everyone the information, and opinions and advice it’s helping out a lot!! What I’ve done so far to the car is bought a tremec transmission. Like I said before above I’m new so wasn’t sure what I was doing just needed a trans and I searched up and it brought me to that one I looked at it while searching it’s potential and I got highly interested. not knowing anything about the gear ratio I wasn’t sure what to exactly go for while wanting it to get real good pull for playing around while still being able to drive it. The car has some power however I haven’t dyno’d it so don’t know what it’s exactly pulling to the wheels getting bored of low power lol but I wanted some information from people who knows waaaaay more than I do with upgrades, and what not. The car just seems like it tops out quicker and doesn’t want to pull after so far doesn’t seem to give you the big kick like it used to with the old trans before he blew it up lol. It had the T5 manual trans before I got it and bought one.
 

AeroCoupe

Founding Member
Oct 28, 2001
547
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Again, without knowing what the current engine combo is (stock, bolt ons, cam change, etc), what carb is on it, rear gears, etc. its going to hard to help.

My guess is the car had a non world class T-5 with the following gear ratios:

1st 2nd 3rd 4th 5th Rev
3.35 1.93 1.29 1.00 0.68 3.15

The TKO 500 has the following gear ratios:

1st 2nd 3rd 4th 5th Rev
3.27 1.97 1.34 1.00 0.68 3.00

I would say that you should not notice any difference between the two as close as the gear ratios are.

As far as the 7.5 ring gear rear end goes they can handle quit a bit of power as long as you do not run slicks. I wouldn’t worry about swapping to and 8.8 ring gear rear end until you break the 7.5 or want to change rear gears.
 
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slow84lx

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Azhi23, welcome to the Mustang world! The group here can help you through anything that your car needs.

There is solid advice above, especially regarding horsepower. The newer cars have much more power because it is needed due to the much heavier weight. 300-350 hp in a 1985 5-speed Mustang will put plenty of smiles on your face.

What you should consider before trying to increase the horsepower is to verify that your car is in a proper state of tune, the suspension is in good condition, has good tires, and that the brakes are working correctly. Build on that platform.

Brake upgrades on these cars are a requirement if you plan to drive it hard and should be one of the first things that you do.

The 1985 Mustangs are prized by many for the carburetor, 5-speed, and cool front nose. Changing over to fuel injection has its advantages but may take away a little bit from the cool factor of the car that you own.

Jonathan
 
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Noobz347

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Yeah, I have an 86 and I like my fuel injection, don't get me wrong...

I'd never convert an 86 to a carb or an 85 to FI. There's just no reason.

Well...


FI are a [lot] easier to Super Charge :D Yeah, I'd do it for the SC.
 

CAMTWO1070

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Thanks for the quick reply. I did forget to mention the intent on my build ha. I would like to have it so I could drive it around during the summers. It’s stored during the winter and colder seasons here in Canada. Only plays in the warm weather haha. I’m not looking to go the drag way. though I may take it maybe once just for the fun of it after the build is finished. What would be a realistic price tag to get those 500-600 numbers because I haven’t set a budget right yet. Didn’t think about it I was just going to go until I got the right set up that I felt comfortable with. The body, and frame of the car is good I’m just focusing on drivetrain and power right now, and work my way around as I go.
A realistic number for an engine built that stout and built right would be between $8-10k usd......If you plan on mostly cruising in the summers in Canada building a ridiculously quick off the line vehicle wouldnt be too efficient even with that TKO500 as I would of went with the TKO600 with the 2.87 1st gear and .64 overdrive and build an engine that has way more torque than hp....

In a high torque engine thats gonna be a stickshift I use nothing less than shaft mounted rocker arms...............

IMG_20220317_193008.jpg


Youre gonna find that with that 3.27 1st gear ratio your car is gonna be a quick short shifting vehicle...My 410w with TKO600 w/ 2.87 1st and .64 overdrive has so much torque I shift from 1st to 4th in less than 100ft and do it shifting at 3000-3500 with the 3.55's and detroit locker my engine doesnt bog down,,,,,

It doesnt take high lift cams and double springs to do it either...Alls it takes is a camshaft with under 220 duration then put some 1.7 rocker arms to increase the lift.

Im also running Edelbrock E-Street heads with the small valves too and my intake manifold is designed to enhance torque by 40ftlbs on a bone stock 351w but between the dyno data with carb at break-in and the EFI w/ Edelbrock intake #3881 on a chassis dyno at 5200 my engine is making 59ftlbs more torque ...LOL.

With the .64 overdrive my engine revs out in 5th gear @ 1900rpm's and cruises on the highway around 65mph.........

A properly built street engine will still put a smile on your face when you plant your foot but be more realistic for the roads and not raise an eyebrow with the local fuzz too...........I have a 4 speed muncie in a 69 olds with a 454 chevy that has a .600" lift solid lifter camshaft with 11:1 compression with a 125hp shot of laughing gas and if you dont put it in the sweetspot every shift it would load up pretty badly...Needless to say the car sits more than its driven because Ive gotten so many tickets in it its ridiculous getting tickets for speed contests or speed prudent and improper tickets because the camshaft and the 4:10 rear has the engine screaming 4500-5500 rpm's every shift to keep it in the zone....LOL

69 olds rearend shot.jpg


Good Luck with your choice and make a build thread too so all can keep abreast of the progress too,...

Pay lots of attention to how to properly align a TKO up to a fresh build then space the slave cylinder correctly aswell as get the driveline angle right....Improperly aligning the bellhousing centerline will cause harsh vibrations and putting the wrong amount of slave cylinder spacers will cause too much excessive pressure plate pressure on the clutch disc or poor gear engagement if too loose........

I like the Robb Mc offset dowels...They have a locking screw that locks the dowel in so it wont come out when its time to change the clutch and will save you time from having to realign the bellhousing again...

Industry standard is .010" but Tremec recommends .005" TIR.........Mine was almost perfect after installing .007" offset dowels............

IMG_20200928_223348224.jpg
IMG_20200928_223532125.jpg

IMG_20200928_223646130.jpg
IMG_20200928_223813025.jpg


I find going with 3/8" of space is better than what they recommend as a minimum which is 1/8" because I found out the hard way that the clutch and pressure plate expands a lil more than 1/8" and with 1/8" of space thermal expansion bypasses that and causes the clutch to slip under heavy acceleration causing your engine to peak high really fast possibly floating the lifters and the valves......

In a Mustang the TKO is higher than a T5 so if you dont cut and raise the trans/driveshaft tunnel you'll have the trans at too much downward angle at the rear and that will cause the TKO to shift sloppy and notchy especially if you run solid motor mounts that are a tad higher too...

Tremec has a driveline angle finder app in google playstore..It turns your phone into an inclinometer to get the driveline within specs...It takes trans angle..driveshaft and pinion angle all into consideration and lets you know if your good or bad...

Another good piece of advice is to break-in and dyno test the engine before doing the alignment check as you have to spin the engine over many many times which knocks the ridges off the honejob making the break-in of the rings not fully effective at getting a proper seal during break-in and dyno testing........

I also have a method to adjusting hydraulic lifter preload without guessing if you're on the base circle correctly and have been using the method since seeing it in a Super Chevy Mag I think back in 1983.....Someone made a vid using a sbc but i posted the pairs for ford...

Screenshot 2022-10-30 221218.jpg



View: https://www.youtube.com/watch?v=LIfZmC_KwGg&t=1s


Take care and have fun..
 
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2000xp8

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The 1985 mustang gt was barely 200hp and ran 15's.
Is there a chance you are expecting too much?

CAT, nothing less than shaft mount rockers? Maybe on a race car or an extreme high end build.
Any other time it's a serious waste of money.
 

CAMTWO1070

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The 1985 mustang gt was barely 200hp and ran 15's.
Is there a chance you are expecting too much?

CAT, nothing less than shaft mount rockers? Maybe on a race car or an extreme high end build.
Any other time it's a serious waste of money.
Yep thats what I said and thats what you see...right?...Overkill I think not....My powerpackage is in a much heavier F250 and to each his or her own when building their engine and making their statements because shaft mounted rockers are the best of the best and in a stickshift more than an automatic equipped vehicle as it limits valve deflection which reduces power with a trans thats virtually dead linked to the drivetrain unlike an automatic that operates under hydraulic fluid power and gives a 15-20% power loss from the engine.....

I built a same exact identical but gloss black 408w with same compression heads and camshaft plus stroker kit and bearings etc but I used these stud girdles and 7/16" studs on that engine with 1.7 ratio Comp Cams Magnum full roller rockers............

IMG_20201008_120700301.jpg

IMG_20220509_163255.jpg


You'd think identically built engines except rocker arm choice and a small 2cuin difference in displacement would produce identical results....................Nope ......The 408w s torque came on 460rpm's later with lesser power also the max torque didnt carry as far and laid over quicker and finished 43ftlbs & 27hp less at 5200 and both tests were done on same dyno with same carb.............

Even with the stud girdles and 7/16" studs with engine mounted in the vehicle and chassis dyno tested there was no contest as the stud girdle acts like a tuning fork which affects the other rockers theyre attached to through a thing called vibratory harmonics....LOL...Take a buzzer put in in your hand and try to do normal tasks.....Thats what your valvetrain is doing.....LOL

I guess you dont realize that stickshift vehicles are deadlocked to the driveline unlike automatics and the shifts are way more harsher and in a stickshift lots of power and duration is lost through the valvetrain due to all of the vibes the stickshift unit picks up and transfers into the crank.......


IMG_20201006_154120528.jpg