So I wanted to get your guys opinion on a trans/gear ratio swap: After my engine rebuild I may do a trans swap and/or gear ratio swap. What would be ideal for a highway setup? Its my daily driver and I need to be able to cruise 60-70 a little better than my current gearing. I dont want to lose my lower gear pull to much though, as I may have to use it to tow smaller things.

 

Your truck has likely already got 3.55 gears in it. Those are the most common gear ratio for the Dodge trucks, period.

If you put a trans in the truck that has OD, 3.55's would be fairly nice on the highway since you have a 2WD and don't have big tires on it.

 

Well to all the carb size talk, it well kill everyone to know what size carb that I run on my 318. To start with it all has to do with your set up. I have a 750 Holley on mine and do not recommand anyone else doing it unless your motor is built for it. I do run a 600 cfm Holley on my everyday 318. A good build for a 318 in a truck is a Weiand Stealth intake, Holley 600 cfm carb., Comp cam # CL20-210-2 or my fav # CL20-212-2 (these are cam and lifter kits), new valve springs, summit racing true roller-double roller timing chain, summit racing headers with what ever muffler you what with 2.25 dual pipes with an H pipe installed, MSD Street Fire coil and CD Ingition Box, and a B&M Tork Master torq convertor 2000 rpm stall. When you take you motor a part be sure to check the wear on your rockers, shafts, and push rods. Replace all of one thing that is wore, not just the one that is. If you have the money replace them all so you will not have to later. Now you were talking gears, older 2wd Dodge trucks most come with 3.21 gears factory, some had 3.55's most factory 4x4's and 3.91's. You can look for a tag that is under one of the bolts for your rearend cover that should tell you what gears you have now. Also, what size tires do you have or are you going to be using.

How for everyones use =

To come up with the size carb you need for your sit up the formula to use is (max RPM/2) x engine displacement / 1728= plus 10% will equal the cfm carb you should use for the best performance from your motor.

To come up with your RPM with a 1:1 ratio trans the formula to use is MPH x gear x 336 / tire size = RPM, you wil have to add some for the slip in the torq convertor like about 5%.

 

i get 368cfm before i add the 10% 405cfm after the 10% using a 318 with max of 4000rpm so the 390cfm Holley would almost be perfect for most 318 truck applications.

 

It is a Dodge, dont drive it like a grandpa. So, you never go above 4,000 RPM's. A rv/towing cam will turn 5,000 RPM's easy. My 82 D350 with a 318 had a factory cab 4 barrel that was 500 cfm's. I had a rv/towing cam, factory intake, 600 holley carb, dual exhaust with factory manfolds and it had no problem turning 5,500 RPM's. The 318 in my truck sees 6,000 RPM's every so often. If you put a cam, intake, and dual exhaust, I would hope that you would step on it every so often. If I pull out in triffic with it in drive and kick it and let it shift itself it will shift at 5,500 RPM's in my 78 with a 318. If you pot a cam in it look at what it says the RPM of the cam is and use that RPM pluse 10% for your max RPM.

 

my engine never goes over 4000rpm. i have been doing nearly 90mph and my tach told me my engine was only turning at 3400RPM. i give my truck hell off the line every so often but it will usually shift into the next gear at around 3000RPM even if my foot is to the floor.

 

my 78 with factory 350 cfm 2 barrel carb would shift about 4200 RPM. After I put on a 600 cfm carb and made sure that my kick down linkage was adj. like it should be it would shift at 5500 RPM's. I know I am new here and no one knows me. But, I have never had any problems or complains from anyone that I have built a motor for. You might want to check your kick down linkage if your truck is shifting that soon if you have it floored. It sounds like it is too loose.

 

with the noises my 318 make over 2000 RPM i would not want to take it up to 4200 RPM. plus like i said. by the time i hit 3400 RPM and my truck is usually moving 90mph. do you seriously need to go faster than that in a daily driver?

 

You eather have over drive, tall tires, or like 2.77 gears to be doing 90 at 3400 RPMs. When I take off, half paddle it shifts from 1st to 2nd at like 3800-4000 RPMs. Floored, it shifts from 1st to 2nd at 5300 RPMs to 5500 RPMs. You must also have a bone stock wore out tired motor that needs rebuilding if it is making noises after 2000 RPMs. Like I said look at what your cam that you are putting in your motor list its RPM range to be like 1200-5500 RPMs. Take the 5500 and add 10%. Then do the formula with that number. That is your max RPM the motor is good for, dont use the RPM that you will be crusing at. Now that is only if you want to get the most out of your motor that you have took the time to build. Also, your stock 2bl. carb should be like 350 cfm. A 600 CFM 4bl. carb works like a 2bl. when you are driving like grandpa and only opens up to a 4bl. when you kick it. That being said the 2bl. part of a 600 CFM carb. is only 400 CFM. That is only 50 CFM above your stock 2bl.. Also, the 600 carb. cost less than that little baby 4bl. that you are talking about using.

 

for street daily driver, get no more cam than .420-.450 lift at valve, and no more than 268 degrees duration, that is advertised, not at .05 lift. any bigger can and your MPG goes out the window. you do NOT need a 4 barrel carb, with this cam on a 318, ie money saved. the cam specs i listed on a chrysler 300L 413 engine makes 360 HP. and very streetable, same MPG as a new yourker. a new yourker with a smaller cam. had 340 HP. my 4200 lb 124 in wheelbase, totaly stock went 15.xx sec in 1/4 mile. the Pontiac gran prix JS was hard to beat. but the caddys was easy to beat. but the new cadys look like they go fast.