T-5 swap into a turbo application

[andrew3]

Im still mentally building my future engine and a "partially rebuilt" 65 200ci on ebay for $25 caught my attention. So I thought I would bring a few questions to the experts here:

1) Does it really make a difference if I use a 7-bolt main with the 2.77 bellhousing instead of the 3.03 bellhousing on a 67+ engine? Will the smaller clutch matter or is it splitting hairs? Since I wont be to the engine phase until this summer, should I just wait to find a 3.03 setup?

2) I see lots of recommendations to use the 4 cyl T-5 becuase of the better first gear ratio. Is a 4cyl T-5 weaker than the V8 T-5 in a way that will become apparent when used with a turbo? With a 3.50:1 locking 9" rear, would the V-8 first gear be atrociously short and unusable?

Edit: Oh, and the future build would include the FSPP head so the more restrictive 65 head vice a late 70s head wouldn't be an issue.

Thanks for the help!
-Andrew

 

[XFlow_Fairlane]

my opinions...


4cyl trans and a 3.50 geat sucks. the 4cyl OD is weak (around a .86) so with a 3.50 gear you still spin alot of R's on the highway (I do 99% of my driving on the highway so it matters to me......someone driving mostly in town may not mind it) others have commented a 3.25 is a better all around gear with the 4cyl box. also I think with the added power you will find that first is pointless to have on a warmed over six.

the real weak point in the 4cyl is the gearset/ratio. because of the lower first gear you end up with a smaller gear on the cluster shaft which then can't handle the higher torqie loads. you can swap these out if you rebuild the box (basicly turning it into a v8 box)

I would go with the 3.03 bell so that you can put in a 9" clutch (from a 2.3L car) which is more common plus it gets you away from the recessed flywheel.

 

[Bort62]

Well, I have a 4 cyl box behind my stock 200 w/ 3.89 rear end. First gear is way too low really - I start in second most of the time.

If the motor made any more power, the 1st gear would be really pointless. As it is I top out at about 5mph in it... haha

 

[andrew3]

Ok, I will pass on this engine and wait till a good deal on a block with the dual bellhousing patterns pops up.

T-5 Options seem to be:

Donor 1st 2nd 3rd 4th OD TQ rating
2.3L 3.97 2.34 1.46 1.00 .79 240
5.0L 3.35 1.99 1.33 1.00 .63 300
T-5z 2.95 1.99 1.33 1.00 .63 330
http://www.allfordmustangs.com/Detailed/349.shtml

So, obviously the T-5z would be the best way to go since "It has the best of everything. Hardened gears, short throw shifter, steel front bearing retainer, and tapered output shaft bearing. Best of all it has a torque rating of 330ft/lbs. This T-5 can handle up to 450 hp if not drag raced."

That low 2.95 first gear would probably make for the best driving experience with the 3.50 final drive ratio.

Downside is that it will definitely be harder to find used and will be more expensive.

Thanks for the advice!

 

[XFlow_Fairlane]

you can put a new cluster gear and input into a 4cyl box along with a refresh kit and a couple other bits and upgrade it to the Z specs or farther even. is this going in a drag car on slicks?

 

[andrew3]

Nope. Ultimate goal is to build a fun, driveable mustang with good fuel economy and power on demand. Plenty of math and compressor mapping to do, but my goal is to set a boost threshhold around 2500 rpm so I can drive with relatively normal economy around town, but added torque is available when I need it.

I may one day look at open tracking or autocrossing the car, but I doubt I will be going to the dragstrip. Desired horsepower peak would be around 300rwhp, pushing 7-8psi. Depending on rpm, I dont know exactly what torque levels that would translate into, but it should be well over 300. So I want to make sure I have a tranny that can stand up to some spirited driving.