85 mph brick wall

67coupestang · Apr 11, 2004

thats crappy too!!

351W + tremec in OD + 2.8 gears = top speed of about 85!

granted it'll do more in 4th but man that sucks!!

I still think my 750 carb is too big (anyone want to trade) but gears have got to be a lot, she dont sound healthy at 60 in 5th

think 3.50's would be too much??

taylor4g63 · Apr 11, 2004

if you have OD, i would suggest 3.73's or somewhere around there. They seem to be the best all around gear. If you want more performance, go to a 4.10, want better gas milage, a 3.5 or so would be better.

SadbutTrue · Apr 11, 2004

i know with fox bodies, due to the 2.8s in the back and the .63 top gear ratio, they top out in 4th with the 5 speed trannies cause htey can't rev in 5th. I'd get 3.73s as the above said, as long as there isn't anything wrong with the engine otherwise.. does it pull hard in the other rpms?

67coupestang · Apr 11, 2004

oh hell yea it pulls! i was just worried about 1st gear 3.35 first + 3.50 gears...

SadbutTrue · Apr 11, 2004

nah, that'll just make it more fun

I'd go with ~3.50 for sure... just as a question, what is the top gear ratio in a 3550?

zookeeper · Apr 11, 2004

So you guys really think you need more gear to run big speed with an overdrive 5 speed? Wow, I'm sure glad I didn't know that before! My wife's 5.0 GT with a ton of miles on it will easily run faster in 5th than 4th. Your 351 should easily pull top gear with 3.0 gears due to the massive torque those motors are capable of, even stock. Since the lower gears work as torque multipliers, making it easier for the engine to do the work, I'd think that whenever the motor is put under a strain, it's struggling. That's a sign of too little total timing, so whup out your timing light and scope it out. For checking total timing, leave your vacuum advance plugged in and wind the motor to about 2,700 or so, then hold it steady and see where the marks on the damper read. Although I'm not sure what your particular motor is happiest with, I'd suspect around 32-34 degrees would be a nice start. Then slowly advance it 2 degrees at a time until performance starts falling off (or pinging) then back it up to the last good reading. Hope this helps.

65fastback2+2 · Apr 11, 2004

5th gear is for cruising, has very lil pullin power, if i want to go in my dads 5spd vw, it'll pull really well in 4th and slowly in 5th. Gears are important, and i know this sounds stupid, but on any gran turismo, even on a 1000 hp car, put 5th really up there and you will actually lose 5mph shifting from 4th to 5th.

zookeeper · Apr 12, 2004

I hate to be a jerk, but what are you basing these "facts" on? Please tell me that your entire engineering experience isn't based on the data acquired by topping out Dad's VW. Read this gentlemans' post: he states that it doesn't sound too good at 60mph, and will not pull past 85 in 5th gear. This is not normal, regardless of what anyone thinks. Also, what 1000 hp cars have you ridden in lately? What was their final drive ratio? What was the high gear trans ratio? All these factors, plus the coefficient of drag (hardly important at 85 mph) will determine top speed. But none of these problems apply to the current problem, it's a sour motor, plain and simple.

STSFCTN67 · Apr 12, 2004

My 67 pulls really hard in 5th gear and 85+ and I never downshift to 4th. The only problem I have is that the front end really starts to feel too light and floating at higher speeds. I had 3.00 and upgraded to 3.25 and the 3.00 were a noticable difference on the highway. It could be your carb just flooding you out. I had a 750edelbrock and I had to nurse it to get to 85.

68 & 00 GT · Apr 12, 2004

my 2000 pulls plenty in 5th. I seldom have downshift it on the highway. Few cars can keep up w/ me just rolling the gas in 5th. Oh and yeah it's a Tremec w/ 373 gears.

67CoupeDriva · Apr 12, 2004

Well if it lacks power at low RPM but wakes up at a higher engine speeds, assuming you don't have an inappropriate cam or heads (e.g., Boss 302 = torque dog), I'd say you are overcarbed. One of the biggest factors in low-rpm power is airspeed through the carb to atomize the fuel; if it's too big the air isn't moving fast enough until the rpm comes up.
The gears will make a difference but if the engine is mis-tuned it's just curing the cough while leaving the cold.

67CoupeDriva · Apr 12, 2004

Well if it lacks power at low RPM but wakes up at a higher engine speeds, assuming you don't have an inappropriate cam or heads (e.g., Boss 302 = torque dog), I'd say you are overcarbed. One of the biggest factors in low-rpm power is airspeed through the carb to atomize the fuel; if it's too big the air isn't moving fast enough until the rpm comes up.
The gears will make a difference but if the engine is mis-tuned it's just curing the cough while leaving the cold. At the risk of sounding sarcastic, my bone stock 4.0 Explorer would walk right by you at 85 in overdrive with the air on and a boat behind it, so your 351 isn't living up to it's potential.

BAD67FUN · Apr 12, 2004

Can't bust 85mph? Sorry... that's a huge problem that might warrant a five hundred word response that I just don't feel like writing. You should be hitting that mph half way thru third gear!!! Something is really wrong.

65fastback2+2 · Apr 12, 2004

zookeeper said:
I hate to be a jerk

look, you prolly know I am 18, i dont have alot of experience, so I posted what I do have experience in, give me a lil break.

sand1man · Apr 12, 2004

while I agree there should be no problem gettting obove 85 in 5th it may just be your settup all together, may want to post some more info about motor, using a 225 60 15 tire and not know wing if 5th in yours is a .63 or a .83 OD if it's a .63 OD than if your using said tire your only turning a tick under 2K rpm I could see where this may be a problem if you don't build any power to say 4k

zookeeper · Apr 12, 2004

65fastback2+2 said:
look, you prolly know I am 18, i dont have alot of experience, so I posted what I do have experience in, give me a lil break.

I didn't know your age, and to be honest I really never considered it. But while I do apologize for the harshness of my response, here's why I feel so strongly about giving half-truths or incomplete answers to fellow Mustangers problems: lets suppose that this gentleman didn't know your age (I didn't) or experience level. Your advice could have sounded reasonable to him, and he then spends several hundred bucks on your say-so only to find that it was a fouled plug or a loose vacuum connection, don't laugh I've seen it happen and it's sad when it happens to you. So while I agree that each of us has the chance to make a valuable contribution to help solve each other's crisis, we all need to think before we send a friend down the wrong road in search of the Holy Grail answer to the headaches we all find from time to time. I've come to the advice well of this forum many times and have had tons of good advice given by people I'll never meet and get to thank, so I feel the best way to thank them is to give quality advice to others. There, now don't we all feel all warm and fuzzy about being part of the Mustang Brotherhood?

67efivert · Apr 12, 2004

well before u do anything tell us a little more bout this engine it could be slap wore out or simply to high of a powerband for 5 to pull with those gears? let us know

SadbutTrue · Apr 12, 2004

not for all five speeds, but on a T5 and on most standard 5 speeds 4th gear is 1:1 and 5th is about .65-.6:1. This doesn't sound like a huge gap, but proportionally it is. So without a very powerful engine, or a very high rear gearing, the engine won't be able to rev into 5th gear. Many people re-gear 5th to about .8:1 so they can actually use it.

this is all assuming like, as he says, the engine seems healthy at all other rpms and gears. yes, 5th should still be more worth more than 85 imo, but i do occasionally hang out on the 5.0 forum and as I said several of them say that the 5.0 tops out in 4th, not 5th. This would be why.

SadbutTrue · Apr 12, 2004

not for all five speeds, but on a T5 and on most standard 5 speeds 4th gear is 1:1 and 5th is about .65-.6:1. This doesn't sound like a huge gap, but proportionally it is. So without a very powerful engine, or a very high rear gearing, the engine won't be able to rev into 5th gear. Many people re-gear 5th to about .8:1 so they can actually use it.

this is all assuming like, as he says, the engine seems healthy at all other rpms and gears. yes, 5th should still be more worth more than 85 imo, but i do occasionally hang out on the 5.0 forum and as I said several of them say that the 5.0 tops out in 4th, not 5th. This would be why.

skywalker · Apr 13, 2004

sadbuttrue: I know it is not true for every T-5, but for all of the ones that I have seen, the gearing for 4th is ineed 1.00 as the top gear is in basically every non-overdrive transmission (at least I've never seen one where it wasn't) and 5th in the T-5 is the OD gear and all the ones I've seen the ratio for 5th is .68 or .63. That can be changed, and other gearing is available in the T-5, but that's what you should see most of the time...

Sounds to me like he maybe lacking in power at the lower RPMs. I have no issues with my car which has very minimal upgrades for power, at getting past 85 in 5th, going up a hill (I have a T-5). It sounds to me like his engine either needs some tuning or has some serious issues.

85 mph brick wall

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