Muncie to T56 swap

[Differen T]

Differan T,

What you have said is very valid. The 383 stroker I just had built, I gave up a lot of horsepower at higher rpms so that it would be a torque monster at low rpms. Peak HP is a modest 320 at a low 4050 rpms. Torque is 516 lb/ft @ 2800 rpms. Car weighs 1790 lbs, so if I'm not totally nuts, a perfect canidate for gears that tall. As it stands now, I can climb out of steep mountain canyons with slow to 25 mph curves in top geat at 1000 rpms and pull decently and smoothly up the grades. I have checked the other gears of each transmission, 1st gear is still low enough, 62 mph @ 5500 rpms with 2.88 rear gears, 31" tires, and 0.64 OD.

Bob

If I understand you correctly your Muncie and 2.88 gears with 30" tires pulls good from 1000 RPM's. What you are proposing is 1250 RPM's with a 2.88 and a .5 OD for a final ratio of 1.44 to 1. using a six speed. To get the same results your torque needs to double from 1000 to 1250 RPM's. Take it out and drive it in fourth gear from these RPM's on level and inclined roads to get a fell for the torque increase. And as stated wear and tear is tremendous under low speed high gear acceleration. You can also increase low speed torque by advancing the cam if you have the piston to valve clearance. With 383 C.I. I would not decrease the exhaust below 2.5 ins. in dia.

Al

 

[Ted Brown]

As far as squeezing the pipes down, check it out on a dino, see it for yourself at low speeds and values... This is not a supercharged engine, it requires back pressure at lower RPM

 

[Ted Brown]

Ted,

I have used tires in the past to attain a more favorable gear ratio for my needs. Back 20+ years I had an old tired Ford van that by DMV rules needed to be tagged commerical. I also have a CDL, and believe it or not was within the rules towing triples behind that van. An 18' flat bottom boat, a tent trailer, and then a little 10' shovel nose hydro boat. Just needed to be under 65' overall. The 351W in the van was a bit tired for pulling all of these over the summit to Tahoe and I needed new tires, so went to 50 series radials. Problem cured. If I go from 30" to 33" when I need rear tires, that will get me a little closer and will also give me a much needed 1 1/2" more clearance for my oil pan. I will probably go with the 5 speed and take things in steps. You and I have talked about restricting the exhaust, my question is with the way this engine was built, will it still increase my torque and/or lower the rpm the torque peaks at? Also, as you know, I'm not running any kind of tuned exhaust and wonder if an H pipe (cross over pipe) would be a good thing to add? The V10 Viper is geared the way I would like to gear, do you think at its weight it is a better canidate to cruise 65 mph @ 1250 rpms?

A cross-over adds some good/free HP do it before any squeeze in pipe size, like I suggested a bolt-in flange with different sized holes will give you a quick easy testing, drive it and see for yourself the difference all the different size holes will make, start with 1 5/8 ID and go up from there to where you get the best performance you like best... Works great for me... heck my big block idled at 1200 at times..

 

[deckofficer]

Mike,

Looking at the photo at the beginning of this thread, where would you put the X pipe?

Al,

Current rear gears are 3.54. I was only thinking of 2.88's with the 0.64 OD of the 5 speed. The 0.50 of the 6 speed gets my rpms right where I want them for hwy cruising with the 3.54. You and Ted have both mentioned how rough it is on an engine to pull hard from such a low rpm. I don't think I have done that. The pulling out of the canyon is at a throttle position that is just past idle (very light throttle) and the engine seems VERY smooth and surpriseingly quiet. Mike, help me out here. When knowledgable folks like Ted and Al feel that I'm possibly abusing engine bearings and pistons by running at low rpms, it concerns me. If I need to pick up speed quickly, I always downshift. On the 2007 Mustang (unmodified) with its 5 speed automatic, with light throttle I can get the torque converter to lock up at about 43 mph in 5th. I then if needed can slow to 38 mph, and as long as I pick up speed slowly that car will pull smoothly from about 1100 rpms. I would think if Detroit thinks the 3600 lb. Mustang can do this, why not my 1790 lb car with an engine truly built for low rpms?

 

[2old2fast]

d.o. I would spectulate the problem in your comparisons brtween the the 'new' stangs & your ''t'' is ,the t does NOT have a constantly monitered & adjusted OBD fuel injected engine...... i.e. no detonation............ just sayin'

dave

 

[Screaming Metal]

As far as squeezing the pipes down, check it out on a dino, see it for yourself at low speeds and values... This is not a supercharged engine, it requires back pressure at lower RPM

Agreed....all he has to do is insert some removable baffles (in the ends of the tailpipes), wrapped with fiberglass, to bring up his low end, along with the crossover....

 

[deckofficer]

T back on the lift. Everything is so low in the frame rails, an X pipe, which would be an easy project is going to take some thought. For an X pipe to be effective, I would think it would need to be as close to the engine as possible. About the only place I have any room is aft of the tranny and forward of the rear end. My mufflers are currently in that position. On to the trans swap, I do want that 6 speed, but being 4" longer than the Muncie will be a headache with the driveline. Right now, driveline is 14.5" and each yoke to driveshaft angle is 4.5 degrees. The 5 speed is 1.5" longer than the Muncie. With engaging more splines, might only need to take off .75" from the driveline.

Bob

 

[Screaming Metal]

Hey DO, with a crossover pipe, you could run one right behind your trans crossmember. As long as you don't go any lower than the crossmember, just follow your contour that will match your member, you should be good to go. The size of the crossover pipe isn't as important as having one....you could actually go a little smaller....might help with limited amount of room under your car. A good exhaust fab. guy can do it with the size you got now. Be tough, but is do-able....Ted, Mike, what ya think?

Just hug really close behind your crossmember right under your tailshaft housing. Every place else on your car is fairly cramped for a cross-over....

 

[Ted Brown]

No room to run a 2" crossover in front of the oil pan deep section?

 

[Screaming Metal]

Looks kinda cramped up there but I haven't see a good view up there yet. Yea, if he's got the room. I'd put heat wrap on it in that area....throw a good bit of heat to the pan without it....

 

[Ted Brown]

Looks kinda cramped up there but I haven't see a good view up there yet. Yea, if he's got the room. I'd put heat wrap on it in that area....throw a good bit of heat to the pan without it....

Most all the old stockers had the cross-over there, with not much of a heat problem, but heat wrap would be a very good idea...

 

[Mike]

Well, if wishes were fishes, you would have a set of 180° headers. :nod:

But, since they're not, right aft of the crossmember is likely going to be your best bet. It would be nice to do it with some flanges, so you could drop the crossover out to do trans/clutch service.

The bottom line is that there just isn't a lot of room under a T to accomplish everything one would like to do.

I remember I helped a pal put a 302 in a Pinto, back around 1781 or 1782. The headers on it were certainly different, as they swept forward and then down, rather than back and down. There just wasn't any room to bring them back, short of cutting the fenderwells and I would have been afraid of the whole front end falling off the car by doing that! :wow:

I don't recall what your headers are like, but that might give you some options, swapping the headers side-for-side.

 

[Lee_in_KC]

I don't recall what your headers are like...

IIRC, he has ram's horns.

 

[Screaming Metal]

Mike Said-
But, since they're not, right aft of the crossmember is likely going to be your best bet. It would be nice to do it with some flanges, so you could drop the crossover out to do trans/clutch service.


What he said! Thats a good idea....better to have it than not to have it! :thumb:

 

[Differen T]

T back on the lift. Everything is so low in the frame rails, an X pipe, which would be an easy project is going to take some thought. For an X pipe to be effective, I would think it would need to be as close to the engine as possible. About the only place I have any room is aft of the tranny and forward of the rear end. My mufflers are currently in that position. On to the trans swap, I do want that 6 speed, but being 4" longer than the Muncie will be a headache with the driveline. Right now, driveline is 14.5" and each yoke to driveshaft angle is 4.5 degrees. The 5 speed is 1.5" longer than the Muncie. With engaging more splines, might only need to take off .75" from the driveline.

A crossover pipe is going to change the sound of your exhaust as well as increasing torque. Some of that thump you love is going away. I feel that restricting the exhaust is a not a solution for a nearly 400 cube engine. Depending on your engine combination advancing the can may not be a problem As a rule of thumb 1 degree of advance lowers your whole torque curve 100 RPM's. Torque at all RPM's can be increased by adding higher lift rockers. Long tube headers with long collectors will also increase low end torque.

With a standard trans you need to drive it at the lower speeds in direct drive to get a feel for the torque difference. The percentage increase in torque from 1000 to 1250 RPM's must be about the same as the same as the decrease in gear ratio of the overdrive. Wih an automatic the torque converter has slipage factor the is not found in a stick.

Using your 30 "' tires and 3.54 gears a 5 spd with a .64 OD at 1250 RPM's cruises at 50MPH and a 2.87 to 1 first gear has a starting ratio of 10.16 which is lower than your Muncie (2.20 low= 7.78, 2.54 low= 8.99). With a light vehicle there is no gain with a six speed. I'm sure as was already said, save that grand for something else.

Al

Bob

 

[deckofficer]

Going with the 5 speed TKO 600 0.64 overdrive from this outfit as they seem to have the best prices on clutch and pressure plates as I will need to upgrade in this area too due to the new torque.

http://www.americanpowertrain.com/cart.htm#ecwid:category=175688&mode=product&product=994890

Of course I still need to do a BBB search for their grade, and has anyone had any dealings with American Powertrain? It seems everyone sells this box for the same price, $2195.00. Plan on ordering on Monday.

Bob