performance for 318

[comancheman318]

well..im sure everyone is tired on answering performance questions about 318s but i have one...i want 14s in the quarter...thats not asking much is it...this motor is qoing in my 1988 jeep comanche...i figure that its a small truck so it should be capable of 14s...i would also like to know where i can get a different rearend with steeper gears than stock (3.07)that is a posi traction unit that will bolt on and use the same rims i have if possible....my dad tells me stories of his 73 challenger 318 with a 2 barrel, 340 cam, headers, and bored .030 over...with a shift kit in the 904 tranny...would melt his right tire through 2nd gear...well i appreciate all answers...thanks

[comancheman318]

will someone help me out....this is like the third message i have put on here...none of which have gotten any responses...i would greatly appreciate it...thank you

[dbdartman]

Have patience, Grasshopper! It might a few days, but the person that's done it before will probably be happy to tell you what worked. I'm not an engine builder, but I will say that to get the 318 to perform, the first thing you need to do is lose all the weight you can. The less you have to move, the easier it will be to go as fast as you want. I'd guess you need at least 9.5:1 comp ratio, at least a 600 CFM carb & I'd use 1¾ headers. The heads are the key! The best heads are the latest Magnum heads, but converting could get expensive. The "high swirl" heads of the mid to late 80"s are the next choice. (casting ends in "302" I *THINK*) The chassis & fuel delivery also play a great part in performance, if either are not up to the challenge, you may as well throw your money at a Chevy! One question, though. Is this 318 a Mopar engine or is it something I'm not aware of? If it's Mopar, why not go with a 360? It has a bigger bore *AND* a longer stroke which means it will out-perform a 318, dollar for dollar, every day of the week. It is also the same size, shape & weight as a 318, only difference being the way it's balanced (318 internal, 360 external) & there are a number of ways around that.

Hope this helps some.
<font color = 990033>DB</font

[comancheman318]

i appreciate your reply...but my dad has experience with building the 318...and he says to bore it .030 over put a 340 cam, headers, and shift kit in the tranny and it should do fine....what i want is just 14s...i dont know if this will get it...my truck is relativly light...88 jeep comanche...so...

[RAM MAN]

Here's a few ideas:

VORTECH makes a supercharger for your 381 (5.2L)

MOPAR makes a performance Jeep V8 SBEC computer chip (depending on what year you have).

BORLA makes a nice stainless exhaust to free things up there.

There are also underdrive pulleys, larger throttle bodies, extrudehone intakes, better cams, cylinder heads and hi flow cats (again depending on what year your truck is.)

The parts are out there. Tell me what you want and I'll help you look for it.

Good luck on your project.

[The Dartman]

I have some recommendations for setting up your comanche to run 14's.

We really need to know what your plans are with the stock engine componants and other stock pieces. Are you going to keep it all? Some of the ideas won't work well with stock parts in place (computer, throttle body, engine sensors). A 14 second ride is nothing to sneeze at!!

These are all assuming that you are not building a 318 from the ground up, rather modifying an existing motor. A "ground up" motor would require some thought as far as compression, machining, head work, and any other machine shop or parts. These are all "bolt on" ideas.

1. Headers. You will see the most benifit from installing a set of headers on a stock engine than anything else. 1 3/4 are optimal, but you may have trouble finding a set (custom headers cost more than my entire car). Make sure your not choking it off by putting stock mufflers on. I have seen improvements of a 1/2 second off ET by dropping the exhaust alone. This will work utilizing stock componants as well as some of the peices below.

2. Matched cam/intake/carb. If you wanted to remove the computer controlled fuel injection and other pieces, you can get a kit designed to use these optimal parts (cam/intake/carb) together. I always say let someone else figure out how to make HP for you. I imagine this kit would consist (approximately) of a 600 cfm carb, a dual plane intake, and a 274/474 cam. If you want to start out, maybe just a performance carb and intake? If you wanted to improve this area from the stock standpoint, maybe a larger throttle body?

3. Ignition. If you want to keep the ignition system relatively stock, go with the aforementioned high performance computer. This are proven performance piece (although pricey). If you want to convert it to a non computer ignition, try a mopar Orange box system with a nice set of platinum plugs (splitfires are evil). Top it off with a set of 8mm wires. An MSD woiuld be overkill on a 14 second street machine.

4. Cold air induction - Get some cold air in there!! Good for ten factory rated horse on some eariler muscle cars. You can find store bought (or make your own) ductwork induction system from grill or under bumper, too. If you can't do this, try raisng the rear of your hood as much as possible. It will act like a cowl induction and vent all the crappy under hood air out. this should work with both the stock and aftermarket setups.

I have a 12.87 Dart Sport 318 with 12.5 compression, a 517/292 cam, a 750 on a Holley Strip Dominator, in a car that weighs about 3150 pounds.

P.S. We really need to know more about your jeep and what your willing to do to run 14's. And how much money you have!


[This message has been edited by The Dartman (edited October 08, 1999).]

[cudadude]

one thing that i am assuming here is that youhave a pre magnum 318. I think that if this is the case we need to know exactly what year motor you have. All 318's can be built to run strong. Your little truck is going to weigh more than your average rustang or cramaro. I think your best bet is going to do a ground-up build for this project. take a pick on your pistons but limit yourself to around a 9.2:1 nominal compression with your heads you choose to run. I myself would would run an early set of 360's. keep your camshaft on the mild side. Run a split pattern with around 208-218 duration@ .050 . Run a duel plane intake with a 600-750 carb depending on the rest of the parts you choose. I would probably stick to a 1 5/8 header to retain some bottem end torque. A full 2 1/2 exhaust with flowmasters also. If i am not mistaken you have a dana 30 rear diff.. you should call Summit Racing and i am sure that richmond offers a ring and pinion for your truck. Remember that your goal is to get the weight moving so trying to build to much horsepower will result in you having to go steeper and steeper with your ratio to get your cam in its torque band. Another excelant source for info on a 318 is a copy of mopars speed secrets book. It has all the small details that are too long to cover here. Good luck on your truck and let us know how it turns out
CUDADUDE!!!

[9dodge]

I'm gonna through my 2 cents in here, cuz alot of times mistakes are made for noreason and I see alot of people over engineer the wheel.
I run a 318, pre magnum engine, in circle track racing. I know, you all want to go straight, which is great, I started that way. Anyway, my motor is a 60 over 318, with stock crank, rods, KB pistons, stock 318 heads, NO work at all, non, nada, stock valves, adjustable valve train, a low lift hydralic cam( RV Type). Cheap hedman headers, RPM manifold, and a out of the box stock Holley 2 barrel 500cfm carb. For s**t and giggles I took it to the drag strip. This is a 2800lb, 904 stock tranny, stock converter, 3.73 gears and my circle track tires, which are a hard as rocks tire and it ran 14.20's. It's all combo, yes, I have a weight advantage, but this is a no nonsence motor, done right, and it works. I had the motor freshened after 35 races, thats hard miles. All I'm saying here is get the parts to work togther and it will run what you want for little to no money. By the way the above motor cost me $1600 to build, and has won me 2 championships and is the winningest truck in the country the last 2 seasons.

[Christopher]

My first car was a 72 Duster and this is how we setup the 318.Holley 600 vac sec carb,Holley street dominator intake(use a similar part this is not made anymore)stock 340 replacement cam and lifters,340 valve springs,timing chain,1 5/8" cheap headers with 2 1/4" exhaust,Turbo Action shift kit in the 904,stock 2.76 gears.Did a valve job that consisted of knurling the guides and lapping the valves.And that's it.With 3.91 gears out of a buddys 340 Dart Swinger,it ran 14.30's all day long with the exhaust corked up.With the 2.76's it would get 21mpg on the highway.

[Brian Mills]

I had a 9.5 comp 318, 340 heads,then 360 heads, big cam headers all the double roller and high volume stuff etc. Killed 350 camaros regularly. All the above mentioned combos are well proved, check your weight, you may want to lean towards the RV cams. One thing, don't get hung up on headers, they could prove expensive in your application. Go the next best choice, a set of 360 Magnum exhaust manifolds, find a new truck guy going to headers and make him an offer. O ya, 340 and 360 heads are both comparable till you really rev up, the best for street is 1.88 360 valves in 318 head castings, minor porting if you can get it. Stay 9.5 comp, don't over cam and don't over carb 600 cfm 4 bbl, or Holley 500 2 bbl. If carb is a money problem, go factory 2bbl from 360 till you can afford good replacement. You can always start with small carb in this case till it's broke in and dialed in, then step up with more gas.

Good Luck Brian

[comancheman318]

i appreciate everyones info...i really hope i can make this work...i havent ever heard of a comanche with a 318 or any v-8 for that matter....it should turn some heads..also..the weight of my truck is 3000 pounds...not too bad...also..i replaced the radiator the other day and was hoping to use the same one from my 4.0 six when i install the 318...except that i am gonna use dual electric fans...well any other info is greatly appreciated

[9dodge]

Late model 318 heads with casting numbers
"302" with the 1.88 valve is the best setup, the heads give excellent torque.