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View Full Version : How do I choose a carb, cam and intake manifold for my 318?



TurbododgePirate
02-27-2008, 11:55 AM
I am new to working on carbed V8's. I have a 1985 Dodge D150 pickup with auto tranny. Stock it had a amazing 140 hp!!! Well, that just plain sucks. So, I am getting a pair of summit headers 3" cats and 3" mufflers. I am keeping the stock heads right now, but within a year will be getting a pair of heads form a 340.. I think they have 2.02" valves.

Anyway, I have no idea what to get for a carb, intake or cam. I want to tow my charger with the truck, but I would also like to take it to the strip and not have it be a total turd. If I can keep mileage above 10mpg it would be nice.

I want to do bolt-ons, no machine work. Any suggestions?

Turbodave
02-27-2008, 12:42 PM
I think a simple dual plane 4bbl intake like an edlebrock performer would work well for you. That plus a an edelbrock carb are pretty much good to go right out of the box. I believe they offer a performer Cam that matches that setup as well.

As far as exhaust, Dual 3" pipes might be a bit much. If it was me I would run dual 2.5" pipes to help retain some of the low end your going to want for towing. Bigger is better doesn't apply to a naturally aspirated engine in the same ways as our turbo cars. Even going from a single 2.5" pipe to a single 3" I noticed a loss of low end on my 96 318 powered Ram.

turbovanmanČ
02-27-2008, 04:20 PM
Phone Comp Cams or whichever cam line you want, they will tell you what cam you need.

The heads suck on 318's, if you can, upgrade to Swirl or 360 heads. 2.02 intake valves are probably too big for a 318, your going to have to deshroud the bores. You also need to replace the pistons or mill the heads to bring the compression up if you using old style 360 heads.

You want a 600 Holley Avenger type or Edelbrock Performer carb, I haven't used the Holley but use the Performers all the time, plus there a snap too tune.
Edelbrock dual plane intake is the ticket.

3 inch is waayyyyyyyy too big, go 2.5 inch dual exhaust, X-pipe or regular H crossover and mandrel bent. I love Flowmasters. Also, extend the header collectors aprox 12 inches, this boosts low end torque. You can buy them that bolt to the flange or just cut, add and weld. I would also install Flowmasters ball/cup joint kit, they never need gaskets and don't leak, plus you can make small movements on the exhaust.

Get the Orange Mopar ignition box too.

I have a 75 B250 Camper Van, 360 with X heads, 10:1 compression, headers, 2.5 inch exhaust, edelbrock intake and carb, RV cam, made over 400 ft/lbs to the rear wheels but only gets 9mpg but easily tows a 6000 lbs trailer with 3.3 gears, :nod:

TurbododgePirate
02-27-2008, 05:31 PM
X heads... those are the ones my friend has. Are they good? 2.02 inch intake valves and 1.60 inch exhaust valves. I was planning to just go headers, cats and then the purple hornies. You are saying I should do a H pipe?

turbovanmanČ
02-27-2008, 05:54 PM
X heads... those are the ones my friend has. Are they good? 2.02 inch intake valves and 1.60 inch exhaust valves. I was planning to just go headers, cats and then the purple hornies. You are saying I should do a H pipe?

X-heads are the best flowing, out of the box, old style heads and yes, they're 2.02 valves. You need to check for clearancing, as I bet there going to hit the cylinder wall.

Yep, do an X-pipe or just install a normal cross over, if not, those crap mufflers are going to BRAP, :(

TurbododgePirate
02-27-2008, 05:59 PM
Hahahahaha Okay. I'll look into a crossover... and maybe better mufflers..:)

Hey, that begs to ask another question, I was planning to do the exhaust first, will the headers and exhaust yield any real performance gain?

Okay, Found a nice one from summit. Summit SUM-642125 $84.95 X pipe. I guess thats cheap. $99 for headers, $85 for the X pipe, Gotta find cheap cats and cheap mufflers.

turbovanmanČ
02-27-2008, 07:14 PM
Hahahahaha Okay. I'll look into a crossover... and maybe better mufflers..:)

Hey, that begs to ask another question, I was planning to do the exhaust first, will the headers and exhaust yield any real performance gain?

Okay, Found a nice one from summit. Summit SUM-642125 $84.95 X pipe. I guess thats cheap. $99 for headers, $85 for the X pipe, Gotta find cheap cats and cheap mufflers.

Why do you need cats? state law or emissions?

Headers and exhaust will make a huge difference, I did mine in stages with my 318 before it got replaced with the 360.

TurbododgePirate
02-28-2008, 04:39 PM
State laws. We have a visual inspection of the cats.

karlak
02-28-2008, 04:58 PM
340 heads will fit on a 318 but due to chamber size ( 340 piston is a lot bigger ) it will perform like a dog. Place a 318 head gasket on a 340 head and you will see it. Go with a good set of 360 heads. Or do a engine transplant.

turbovanmanČ
02-28-2008, 05:09 PM
This has great info-

http://www.allpar.com/mopar/4bbl.html

moparzrule
02-28-2008, 05:16 PM
X or H pipes aren't really necessary with dual 2.5'' pipe on a mostly stock 318. Yeah if you were 300+ HP I'd say go for it, but he's gonna be making 200 at best.

Edelbrock intake and 600 carb are great additions. Cheap headers are fine, the $150 ones work just as good as the $300 ones. Dual 2.5'' pipes, mandrel bent won't make any difference on this setup.
If you want decently cheap mufflers that will last awhile, go with these-
http://www.jegs.com/i/Flowtech/387/50322/10002/-1
Used these on a 383 stroker chevy pushing 425 HP, sound great and didn't blow out.

I'd go with the hole ignition kit, that way everything is new-
http://www.jegs.com/i/Mopar%20Performance/312/P3690426/10002/-1

For the heads, the stock 318 heads are THAT bad for ~200-250 HP. Stock valves are 1.78/1.50's which is larger than a 350 small block chevy's 1.72/1.50. 360 heads will KILL your compression, and if you have them milled so much to bump the compression up you will have to mill the intake manifold to get it to seal correctly. Most 360 heads had 1.88/1.60 valves, so the valve sizes are good for a 318 but you really need flattop pistons with 360 heads.

The Pope
02-29-2008, 12:51 AM
compression is too low, you have a low VE short stroke engine. You need to increase low lift flow a ton and increase your VE at the same time. The short stoke engine needs more cylinder pressure as well to increase VE with low overlap and static compression. You also have issues with the flat tappet cam going flat with todays oils.

Hughes lifters with push rod and cam face oiling holes
magnum heads with rockers and hollow push rods
magnum intake manifold, dual plane
625 AFB carb
orange box ignition
Comp high energy 268H cam and roller timing chain
1 5/8" headers, full length
2.5" dual exhaust with H pipe or 2.5" to single 3". Dual 3" will hurt power.

The magnum heads flow much better, and have a smaller CC combustion chamber for higher compression. Magnum heads also have a higher ratio rocker to increase lift a hair. They require the oiling type lifter which you need to oil the cam face and the push rod. The Comp cam is a proven heavy puller with the 318. It has low overlap and lift and gets the power from the duration and high velocity. There are different intakes but the MP dual plane is the best bet. Add the better ignition and the 625 carb and you can get real mileage, a 750 is just too big and will hurt power pulling.

X and J heads have huge poor low lift flowing ports, and they have a big combustion chamber. So they'll murder low RPM torque and power. 3" exhaust is too big and can cost a 318 up to 30 HP. NA V8s are a ballence of flow to create power. You don't have a long stroke, 3.31" for a 318 vs 3.65" for a 2.2 4 banger. Then you have low compression open chamber heads and pistons. The mag heads flow great at low lifts even with a poor VE engine. The cam will run in the right power range for the compression ratio and the head flow. 1 5/8" headers and 2.5" exhaust will give a tuned backpressure at the exhaust valve keeping the exhaust flowing one direction. Higher VE engines with more stroke have more choices, a short stoke engine doesn't. Most of the time you screw them up and make less power, a big reason the 360 is so popular and the 440. It just takes more understanding to make a 340, 318 and a 383 run right. Bigger is not better with short stoke. Mopars DO NOT LIKE big cams. They like real high velocity low lift cams, a customer of mine with a 3,880 race weight and a 130 shot of nitrous runs 10.1 @ 132 with a 284 duration hydraulic MP cam and my ported 906 heads with stock valves. In your case you want a raging mid range, better mileage and will pull a house. Thats the combo have fun with it.

moparzrule
02-29-2008, 07:47 AM
Yeah I didn't even think about magnum heads, good point Pope. This might be the first time I ever agreed with you.
I've also run the comp 268H cam, very nice torque cam with good mid range power too and large increase in top end over a stock cam thats for sure.
On the hughes lifters, I've never run them because I'm quite sceptical on their longevity. I just ordered a cam and lifter set from comp.
As for the carb, the carter afb 625 used to be a great street carb, but now the edelbrock performer 600 is a better carb out of the box. Plus you gotta love the throttle repsonse mechanical secondaries, vacuum secondaries is the reason I hate holley's.
Also instead of getting just the orange ignition box, get the whole kit that I posted the link too up there, you will thank yourself in the end because it replaces the ignition wiring harness and the distributor.

mario03SRT
02-29-2008, 08:08 AM
Edelbrock!

TurbododgePirate
02-29-2008, 10:21 AM
compression is too low, you have a low VE short stroke engine. You need to increase low lift flow a ton and increase your VE at the same time. The short stoke engine needs more cylinder pressure as well to increase VE with low overlap and static compression. You also have issues with the flat tappet cam going flat with todays oils.

Hughes lifters with push rod and cam face oiling holes
magnum heads with rockers and hollow push rods
magnum intake manifold, dual plane
625 AFB carb
orange box ignition
Comp high energy 268H cam and roller timing chain
1 5/8" headers, full length
2.5" dual exhaust with H pipe or 2.5" to single 3". Dual 3" will hurt power.

The magnum heads flow much better, and have a smaller CC combustion chamber for higher compression. Magnum heads also have a higher ratio rocker to increase lift a hair. They require the oiling type lifter which you need to oil the cam face and the push rod. The Comp cam is a proven heavy puller with the 318. It has low overlap and lift and gets the power from the duration and high velocity. There are different intakes but the MP dual plane is the best bet. Add the better ignition and the 625 carb and you can get real mileage, a 750 is just too big and will hurt power pulling.

X and J heads have huge poor low lift flowing ports, and they have a big combustion chamber. So they'll murder low RPM torque and power. 3" exhaust is too big and can cost a 318 up to 30 HP. NA V8s are a ballence of flow to create power. You don't have a long stroke, 3.31" for a 318 vs 3.65" for a 2.2 4 banger. Then you have low compression open chamber heads and pistons. The mag heads flow great at low lifts even with a poor VE engine. The cam will run in the right power range for the compression ratio and the head flow. 1 5/8" headers and 2.5" exhaust will give a tuned backpressure at the exhaust valve keeping the exhaust flowing one direction. Higher VE engines with more stroke have more choices, a short stoke engine doesn't. Most of the time you screw them up and make less power, a big reason the 360 is so popular and the 440. It just takes more understanding to make a 340, 318 and a 383 run right. Bigger is not better with short stoke. Mopars DO NOT LIKE big cams. They like real high velocity low lift cams, a customer of mine with a 3,880 race weight and a 130 shot of nitrous runs 10.1 @ 132 with a 284 duration hydraulic MP cam and my ported 906 heads with stock valves. In your case you want a raging mid range, better mileage and will pull a house. Thats the combo have fun with it.

Thank you very much for this post. I read the mopar buildup of 400hp on a 318 on pump gas, and they did a very similar build. Magnum heads, magnum carbed intake, KB flat top pistons (They used a forged 273 crank I believe) I think that will ultimately be the goal. A 400hp 318 on pump gas doesn't seem too bad. Thanks again.

BIGBRUDDA
02-29-2008, 10:37 AM
I've had several small block motors,smog to 340 sixpack.And several in trucks, vans to Ramcharger wagons.
The trucks seemed to like the Edelbrock "Torker" with a 650 cfm carb.I ran both Holley and Carter ,and actually preferred the Carter for street use.
The best combo was a Carter AFB on said torker. I ran it on a 1976 Ramcharger with a 318 bored .030 over to give it 336 cid I believe. A mopar "purplestripe" hydraulic cam. Stock heads,dual exhaust.
The thing had loooooong legs,(31 in tires) and loved to cruise at 70 plus, towing boats,loaded down with people and gear. Would still hang wit euro trash highway high beam flashers.:bolt: And got 15 MPG.:amen:
If you're gonna buy used heads. Try to get them MAGNA FLUXED first. Small block heads are notorious for a crack in the exhaust(EGR) crossover:banghead:

moparzrule
02-29-2008, 12:06 PM
A torker intake is a single plane, not sure why you would want to run that. And edelbrock carbs are way better.

BIGBRUDDA
02-29-2008, 12:23 PM
Torque is the name of the game when rigging a truck to pull. The RPMs never got over 4000, in normal driving. The cams effeciency range nestled right in there . I wanted a wide flat torque band.:thumb:
Edelbrock carbs are Carter carbs. They we're bought out "yarz ago". :nod:
Now I'm showin mah age!:o

turbovanmanČ
02-29-2008, 01:25 PM
You beat me to it, Carter and Edelbrock are NOW the same carb. The older AFB's are virtually identical and I've swap parts out of both to make one. I believe Weber is the manuafacterer.

I happen to have a Torker intake for sale, :nod:

moparzrule
02-29-2008, 02:51 PM
The same company makes them but there is differences. I thought the carter has vacuum secondaries? Did that change?
They aren't the exact same carb, one is 600 and one is 625 so that right there's proves that wrong.

turbovanmanČ
02-29-2008, 02:54 PM
The same company makes them but there is differences. I thought the carter has vacuum secondaries? Did that change?
They aren't the exact same carb, one is 600 and one is 625 so that right there's proves that wrong.

Both have mechanical and the 25cfm difference isn't even measurable. The castings are identical-except for where they picked up 25cfm? I've worked on both side by side and swapped parts back and forth. My B250 did use a Carter bottom and Edelbrock top, ;)

BIGBRUDDA
02-29-2008, 03:43 PM
Carter AFB carbs came in several "sizes",usually specified by the car manufacturer. Non the less most I have seen are between 625 and 730 cfm.
AFBs are, were manual or linkage secondaries.
Another Carter model was the AVS or air valve secondary. Which worked similar to a Quadra jet. Manual sec throttle blades, with an spring regulated airvalve(chokeplate) to induce fuel flow. I believe those were 695 cfm. another Carter
"ICON" was the Thermo-quad. A phenolic bodied ,spread bore, airvalve design. Not sure about CFM rating. In escense,CHRYSLERS answer to the Quadra jet. To give you that BO.....WAAAAAHHH!!!! feel.:bolt: All 3 were penstar mainstays.
Early on Chrysler used Carter WCFB carbs on its Red Ram and Firepower HEMI motors. Those flowed around 525 cfm.
I've tuned all 4 ,plus Holleys,Rockchesters Autolites, Strombergs, Zeniths, Webers, and Amals. Carters top plate design is the only one that allows access to all fuel metering circuits :nod:without dousing yourself ,and the motor in gas.:wow1:

moparzrule
02-29-2008, 04:28 PM
Carters top plate design is the only one that allows access to all fuel metering circuits :nod:without dousing yourself ,and the motor in gas.:wow1:


OK so first yout guys claim edelbrock and carter are the same, and then say carter is the only one with this feature? Hows that possible?

My old chrysler Newport with a 440 had the thermoquad, it's been awhile but I do believe it was something about 780 CFM.

turbovanmanČ
02-29-2008, 05:15 PM
OK so first yout guys claim edelbrock and carter are the same, and then say carter is the only one with this feature? Hows that possible?

.


The OEM Carter was called an AVS, Air Vacuum Secondary. Now there both AFB's, made by the same company and one flows 25 cfm more and Carter uses a different numbering system for the metering rods.

WVRampage
02-29-2008, 05:22 PM
I wound use the performer intake but a little smaller than a 600 carb,Im rung the 600 on my 400 and its just about right so I would think you would want something a little smaller and the mechanical secondarys are nice for pulling.

turbovanmanČ
02-29-2008, 05:37 PM
I wound use the performer intake but a little smaller than a 600 carb,Im rung the 600 on my 400 and its just about right so I would think you would want something a little smaller and the mechanical secondarys are nice for pulling.

600 is just about right. I bet if you put a 750 on, you'll pick up more power everywhere on the powerband.

moparzrule
02-29-2008, 06:15 PM
To get the CFM you need you have to take engine CID X the max RPM / 3456, and for a street car you usually take 80-90% of that.
Example-
400 X 6000=2400000/3456=694 80%=555.56

He's fine with a 600 carb on there, and only if he has a cam and headers etc would a 750 help him.
For a 318, he's almost right. For a stock to mild 318 you really only need the 500 carb. But since the thread starter wants 400 HP, the 600 is what he wants. For 6500 RPM it's almost dead on 600 CFM, take 80% of that it's only 480 CFM. So since a stock 318 isn't even going to be spinning to 6000 RPM, 500 is plenty.

moparzrule
02-29-2008, 06:17 PM
The OEM Carter was called an AVS, Air Vacuum Secondary. Now there both AFB's, made by the same company and one flows 25 cfm more and Carter uses a different numbering system for the metering rods.

I wasn't talking to you, I want an answer to what I quoted too.

TurbododgePirate
02-29-2008, 06:50 PM
Yeah, lets keep this on topic...... what was my topic again? :)

moparzrule
02-29-2008, 06:53 PM
I was keeping it on topic, I was explaining how a 600 cfm carb is good for what you want. ;)

Turbodave
02-29-2008, 07:56 PM
OK so first yout guys claim edelbrock and carter are the same, and then say carter is the only one with this feature? Hows that possible?

My old chrysler Newport with a 440 had the thermoquad, it's been awhile but I do believe it was something about 780 CFM.


Carter and edelbrock are pretty much the same. Carter has been out of buisness for a while, and I think Edelbrock bought their technology and moved into their own manufacturing plants. So while there are minor differences between them, the overall design is the same and many of their parts will interchange.

http://www.chrysler300country.com/carter_carburetor_company_2.htm

Anyhow, Heath, if your just looking for bolt ons, the edelbrock performer package is probably the best plan and will probably result in something with 200-250hp by my guess. I ran both a Torker and a performer intake on my 340 Roadrunner, and it did well with both. The performer had a little more down low which I think you would like on a truck. The Torker pulled nice through the midrange and with 3.23 gears the car felt like it would never run out of steam.

If your looking to get a little more into it then doing a magnum head swap and the work pope Rob described is a good plan of action.

moparzrule
02-29-2008, 08:03 PM
The Torker is a single plane intake, not good for a truck.
If you are expecting to get up there in the RPMs I'd go with the Weiand Stealth intake. It's kinda like a hybrid, still a dual plane but a different design that offers high end flow of a single plane, it's meant for an RPM band of idle-6800 RPM. The Performer is meant for idle-5500, and the torker is 2500-6500 rated.
I also like the Performer RPM air gap, ran that one before on a 383 stroker chevy pushing 425 horse.
Although if you are going with magnum heads your intake choices are going to drop dramatically!

Birddog
03-01-2008, 04:34 PM
If you want to do heads go for the Iron Ram replacement heads. They made a big mid and upper rpm difference on my Dak and they have pressed in valve seats so no cracking issues like the standard Mag heads.
http://www.hughesengines.com/partDetail.asp?partID=11900
I've been finding myself getting a lot of stuff through Hughes lately... Good guys to deal with!

I'm a big fan of the Stealth intake too, but the Mopar intake is pretty fine as well. Why not keep things simple and get a Holley 4150 vacuum secondary carb?

BIGBRUDDA
03-03-2008, 09:51 AM
OK! First:Carter IS now Edelbrock,(as previously mentioned).The difference is they're now chrome plated.
Torker manifolds are designed to build torque in the widest USABLE rpm range.(as previously mentioned).
Ya can't wring out a tow vehicle to 6000 rpm , without serious problems. Ya build for max torque in the 2500 to 4000 range. So it feels" like it would never run out of steam":amen: Tanks Dave:D

moparzrule
03-03-2008, 04:23 PM
Ya can't wring out a tow vehicle to 6000 rpm , without serious problems. Ya build for max torque in the 2500 to 4000 range. So it feels" like it would never run out of steam":amen: Tanks Dave:D

Yeah I know that why I'm not sure why you are suggesting the single plane torker intake, thats a race car intake not truck for towing intake!
The Weiand Stealth is about best of both worlds. Dual plane intakes are meant for low end torque! A single plane will also KILL his fuel mileage.
I've run a single plane intake on my 77' W100 before, not good results.

TurbododgePirate
03-03-2008, 05:21 PM
Well, looks like I am going to save up and do the mopar buildup for a 400Hp bolt on motor. I figure that ought to be good enough. For now I'm just going to toss on a set of decent dual exhaust and maybe a 4 barrel. A buddy of mine has a 4Barrel carb and intake.

moparzrule
03-03-2008, 05:24 PM
if you just do the headers and dual 2.5'' now it will be re-usable when you swap the engine. Unless you use magnum heads I'm not sure there, do magnum heads require different headers? I'm not too familiar with the magnums.
I had headers and dual 2.5'' in my W100 with the stock 318, and 2 other engines too all used the same exhaust setup.

turbovanmanČ
03-03-2008, 05:25 PM
Headers are the same for Magnum heads too.

moparzrule
03-03-2008, 06:13 PM
Thanks for clearing that up, just wasn't sure enough to say they were the same.

TurbododgePirate
03-04-2008, 05:33 PM
That's good to know that they are the same. One less expense when I get to that point.