Its FI, MAF kit installed. I will get specs for cam tonight
Thank you

 

What does it matter?
I already said it was different and anything further is nothing but a side show.

 

I must have missed the post when you said it was different.


brushtrooper, with the small 5.0 and no power adder, it'll take a loose converter AND gears to get it going from a dig. How loose and how much gear depends on how fast you're looking to go. But guessing you already know that. Tire size will depend on ride height and taste, I prefer at least a 30" tire to fill the opening.

 

Motor has a B cam, when the E4OD was rebuilt a few months back I had a street/strip converter installed so it should be 2500 stall I believe. Truck is stock suspension currently and I am sure we will make upgrades. My son likes the look of the drag packs and large tire to fill the wheel well in the rear. Playing with gear calculators it appears we could go 4:88's running a 32" tire and turn 2700 rpms at 75 mph. Does this sound right?

 

The formula I use shows you will be at 3843rpm w/ 4.88 gearing.
The E4OD overdrive will lower rpm to around 3193rpm

4.56 should get you 3591 rpm in 3rd & 2941rpm in OD @ 75mph
4.11 should get you 3236/2586 respectively

RPM = (mph x axle ratio x 336) / actual tire size

I believe OD is a ratio or percentage but I figure ~650rpm reduction to get close.

 

Hopefully when it was rebuilt they modified the valvebody for faster shifts. Or you will be making friends with the rev limiter every time you run the truck hard.
That post I put above, I have been witness to a b-cam 302 in a truck with an auto. Super sluggish till 3-3200 then it revs quick to the shift point but the trans can't shift fast enough. So it sounds like a 2 step between gears. Only thing that may help low end is staying with the mustang intake. With the smaller cross section of the runners it may keep port velocity up.

 

You are correct. 4.88:1 axle gearing, 0.71:1 OD in the E4OD with lockup converter. I get 2690 RPM at 75mph in OD and 3843 RPM in 3rd.

 

I didn't know there was that much difference with overdrive. Wow! (I guess doing the math would be a smart thing to do)
I could have sworn mine was about 650 difference. Good to know.

I see that I will need to pay more attention to my tach next time I'm rolling down the freeway.

 

I would like to ask for more input, I have been out of the game for a bit of time. The truck will be a daily driver around town and short runs to town. No out of town trips, vacation trips etc. He really wants it to perform good from a dig, road manners will be 2ndary and dealt with.
4:11
4:56
4:88
These are the gear options we are looking at and truck will have a 2500 stall. I am thinking we will go with MT 31x16.5x15LT for the tires. How would you figure RPMs at the end of the track? I am thinking you want to come across the line at the upper end of the RPM range being in 3rd(drive). Is there a way to calculate this for a best guess estimate?
I really like the idea of 4:88's but do not want to run out of motor at the end of the 1/4
Open to ideas and suggestions

 

What are you running for induction?
If you are running on the truck computer, a 4.56 will max out at rpms in 3rd at 110. But, 110 is a bit optimistic for a 5.0 powered truck in the quarter.
And 4.88s will max out in 3rd at 95.

 

You have to know your motor, when coupled to that brick-in-the-wind pickup truck. We can guess, but don't know. Seems like racing (especially drag racing) is a lot of testing and tweaking, including changing ratios to suit many things.
Here's another one of the many calculators out there: https://www.yukongear.com/calc_rpm.aspx
I don't know quarter-mile tech or strategy, but expect a lot to depend on how the engine is built, like Mudsport was asking. Gearing and tire size are going to get you your rpm levels at given speeds, but only you know how the engine is going to be breathing at those speeds.
Like you were thinking then, if you don't want it to run out of breath before you reach the trap (and won't that vary by day, temps, track, lane, etc. every run anyway?) you need to build the gear a little taller.
But like all racing, it's a balance that has to be struck. Not just one gear choice based on what we think might be best without knowing anything more about the truck's overall performance. That is something only the end-users/drivers/racers will be able to figure out in the end. And it might change after the fact, even then.
I think all the recommendations and suggestions given so far have been pretty spot on when they can be.

For calculating chart purposes, any way to find out what the actual height of the tire is? And of course, for that final bit of fine-tuning your calculators, you'd need to know the exact rolling diameter of the tire with the full weight of the truck on top of it at normal air pressure.
If we assume a 30" tall tire for now, a 4.56 gear ratio will put you just over 5200 rpm at 100mph in third. Do you want to use overdrive in drag racing? I'm wondering, since OD is often the weak link in a transmission, auto or manual. But with a built tranny? I don't know.
At that same ratio on the street cruising along at the 75mph I think you mentioned originally, you're only pushing just under 2700 rpm in overdrive. That's no problem for the engine, but what is it doing with all that frontal area trying to push through the wind? Dunno, but you're going to find out!

I guess the bottom line is that with an overdrive trans you do have some leeway, especially on the street. You could go to 4.88's and be at 5600rpm at 100mph in 3rd gear, or cruise along nicely at about 2900 in 4th at 70mph.
The question remains though, do you think you'll be pushing 100mph at the end of the 1/4, or some other speed? More? Less? It's a lot of truck even for a warmed up 5.0. But with low gearing and the ability to rev above 6000rpm without doing any harm, and you could be dialing it in.
You're going to have to know your motor and trans build more than just about anything else then. Notice on that page I linked to up in the address bar you'll find links to other charts/calculators that will let you start with different categories. So you can start with a target rpm, and see what gear ratio will put you there with your tire size. Plus a couple more choices of starting point.
You'll have to make some assumptions initially about how fast you think you'll be traveling at the end, but that'll be easy... After the first couple of runs that is!

Good luck.

Paul

 

^ Good post, 1TonBasecamp.


Starting to think maybe the OP wants the truck,"to be fast from a dig", and have a decent cruise RPM and not so much actual drag racing at the track.

 

This is correct. It will see more street racing on the back roads than time at the track.
Maybe 4.56 is the better choice and fine tune with tire size. Trying to stay with in budget as changing gears multiple times is not feasible.
Thanks for the help

 

Here is place you can play with numbers and get rough estimates:

Wallace Racing - Automotive Calculators

They have calculators for tire size, RPM, ET, HP, all kinds of stuff. Gives you some ballpark information.

 

If this is really the case, you will be miles ahead doing suspension work vs worrying about the best gear. If you are running a stall and have a built engine traction is going to be an issue with a truck.