68 mustang fastback motor options

[cooperscobra]

I just purchased a 1968 mustang fastback and am trying to decide what to do for a motor. The car currently has a 351 Windsor and it does run fine. I ultimately want a reliable mid 12 second car that can be driven often without too many worries. My first thought was doing a motor swap, possibly an 03 cobra motor. When I discussed this with my shop the owner felt that I would be happier by doing modifications to the 351 that is currently in the car. Told me I would end up spending a lot less to get what I wanted that way. He recommended an EFI kit to make the car more reliable and efficient and random parts like heads and a cam to get the power I wanted. Still trying to decide which direction to take on all this and would love to hear everyone's input.

I was also looking through some old threads on this site and saw someone warn a user about mating a 351 Windsor with a T5 transmission. Said that if you run through the gears hard the engine would not hold up to the T5. He did not elaborate anymore on this. If I keep the 351, I would want to upgrade from the top loader four speed the car currently has to make it more highway friendly. Any ideas on this? Thank you all in advance for your time.

 

[rbohm]

i would also build the 351 in the car. with a few mods that engine can easily push the car into the 12's with no problem.

as for the trans, you have a few choices here;

1: keep the top loader, and set up two pumpkins. one with a 3.00:1 gear for daily driving/freeway driving, and the other with say 3.89:1 for running at the track.

2: get a "Z" series T5 from ford motorsport. this will handle the power of the 351 quite well.

3: get a T5 modified by a company like G force who puts in stronger gears.

4: use a tremec 3550 trans, it is an overdrive trans also and stronger than the T5.

5: get what i think is the best trans, either the richmond 4+1 or the richmond r.o.d. six speed. these are arguably the toughest transmissions on the market today. the 4+1 is 5 speed trans, no overdrive, but you can select your first gear ratio so that you can run a 3.00: rear gear, but the car would launch like it had a 3.89 or 4.11 gear. the r.o.d. is a six speed trans and sixth gear is an over drive, and you can still selesct your first gear ratio.

6: you can get a T56 six speed trans that has two overdrive ratios.

 

[D.Hearne]

I second the 351 build. Or one better, go with a stroker cleveland. As for the engine not holding up to the T-5, I think he's got that backwards.

 

[BubbaB1966]

Jumping on the Windsor bandwagon. The Cleveland would take more money and engineering to convert to EFI, the Windsor could be done with junkyard parts.

The Cobra motor, although nice, would require the front swap to Mustang II suspension.

If money is no object, go Cobra. If you are broke like the rest of us (me anyway), rebuild the Windsor, say into a 408 Stroker, convert to EFI, slap in a well built World Class T5.

 

[68EFIvert]

I also would go with a 351 based stroker and go with EFI. I suggest you also look into a T56 6 speed swap in the car. I have done it and love having 2 overdrive gears. I had a T5 for a while and worried about it not being able to handle my power. The T56 is stronger and keeps the engine at a better RPM while cruising. You will have an overdrive gear at .75 and .64 IIRC. The T5 goes from a 1:1 in 4th to .62/.64 in 5th. For me it caused a pretty big drop in RPM when I wen't to overdrive.

 

[wicked93gs]

351s make too much torque for a T5 to reliably hold...I would stick with the toploader and do the pumpkin swap approach, sounds like a good solution, otherwise a TKO would be the best solution(the T56 is an awesome tranny, but the 6th gear isnt any lower than a T5....and with TKOs, you get to choose your gear ratios from some vendors, so you would be able to choose as low a fifth as they offer and be able to take up to 600ft/lbs(double the torque rating of a WC T5, they offer a 500ft/lb and 600ft/lb variety) also a TKO is cheaper(new anyway) than a T56, the only real advantage a T56 offer is closer gear ratios...which is only an advantage on a NA car, if you decide to boost the engine, every time you shift you will loose boost pressure(unless you powershift)....so on a boosted engine a wider gear ratio is more desirable and makes for a quicker car(the longer you can stay in boost the faster you will go) also on a boosted car I would never go with a 6 speed...thats just another gear(another loss of boost when you shift) on an ideal boosted car I would actually go with a wide ratio toploader, too bad I cant use a toploader on my car...I just dont have the option....anyway as to engine choice, stick with your 351w and boost it....its the easiest way to get a reliable 12 second car with zero drivability issues...I'm doing the DOHC 4.6L swap myself and wouldnt wish this headache on my worst enemy, a far better investment of the money you would spend for the Mustang II kit would be that TKO tranny...with a highway friendly 5th gear

 

[68EFIvert]

What I like about the T56 is the extra overdrive gear. You can keep the engine in the sweet spot. Another thing I like about it more than the T5 is first gear. I found that my 3.7 gears with the T5 was useless. I get to use 1st gear for a much longer time now. Here are the ratios for each tranny.

WCT5
3.35, 1.99, 1.33, 1.0, .68
TKO600
2.87, 1.89, 1.28, 1.0, .64
T56 for windsor
2.97, 2.07, 1.43, 1.0, .8, .62

 

[wicked93gs]

off the topic, but do you happen to know the gears for the t45?( I ended up with a t45...not the best option for a 4.6L but it will work for a year or two)

 

[68EFIvert]

I think the T45 is 3.37, 1.99, 1.33, 1, .67 which is almost exactly the same as the T5.

 

[classic boost]

definately go with the 351 option. if money is tight, stay with a carb. remember, all cars came with carbs once, and they drove all over the country. get a 750 vacuum and it will be fine.
a tko 5spd would be a great choice.

 

[classic boost]

btw 68efivert,
i can stare at that pic of your car all day long.

 

[latamud]

The Viper T56 has a .50 6th gear.

 

[A66Auto]

I vote to stay with the 351w. Even if you want something more exotic and can afford the custom work, it still would be my choice. You can do tons with them.

 

[wicked93gs]

I just saw summit sells a t56 with a .50 6th too...for 5.0 and 4.6 applications, so I retract my previous statement, the t56 is now the best option...temped to get one now myself...even though it would mean more hacking on my car