I’m new to the Mopar world and was seeking some advice. I bought a 1975 Duster body and a low mileage 318/727 out of a 1977 campervan for it. I was looking for some info on cheap, easy mods to make it run better. I have a set of long tube headers and was considering swapping heads to the newer 302 style 318 head and a thinner head gasket. I planned on using an aluminum intake and 4bbl carb but don’t know what the best intake to use is. Also thought about changing camshafts and wanted some feedback on what would be a good choice. I’d like to stick with the stock torque converter and I’m planning on running a 3.23 rear.
Cheap 318 performance mods.
- Thread starter Calhoun
- Start date
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- Weiand Action Plus is a good intake... but so are many other dual plane intakes. IF keeping the coil mounted to the intake, then make sure the intake you use has the bosses for the coil mount.
- Many "cheap" head options.. .including using the heads you have. Good valve job and cut them .030 for a slight bump in compression and a good head gasket seal
- Keep the cam small ... like 204-212 @ 050, lift around .427-.455.
- Add new valve springs with the cam (if you install a cam).
- Add a good timing chain set to the list - I have had great luck with the Edelbrock double roller, and it's affordable
remytherat
Well-Known Member
Ant
Well-Known Member
Diy porting the heads is cheap. If by some chance you can get them flow tested, the flow numbers will help when selecting a cam.
Cleaning up any casting slag or imperfections in the new intake manifold and in the ports of the heads.
Timing recurve, you can get lighter springs for the distributor and then try and find the sweet spot for total advance.
Headers and dual exhaust(this may or may not be cheap)
That's very cheap power
Cleaning up any casting slag or imperfections in the new intake manifold and in the ports of the heads.
Timing recurve, you can get lighter springs for the distributor and then try and find the sweet spot for total advance.
Headers and dual exhaust(this may or may not be cheap)
That's very cheap power
The most important item for performance is the torque converter. I don't care how much you do to anything else the converter is the most bang for the buck. 3500 stall no less.. The 2500 low stall converters are for plow trucks and RV's . While the engine is out that and a front seal would be first on the list.
If leaving the 302 heads stock, I wouldn't bother, time and money for no real gain.
You a least want to gain head flow if doing a swap, A magnum head or milled 360 swap keep/gain cr while giving more flow, if willing do some porting can add 273/318 heads back in the mix but you can also port the magnums or 360 heads.
But really you can skip all that if it's a decent runner just the basic tune, cam, 4bbl and headers can do a lot especially with gears and a stall.
Here's a stock low cr 318 with 4bbl, headers and comp cams xe262h for 282hp @ 5000 rpms.
https://www.motortrend.com/articles/mopp-0312-318-long-block-bolt-ons/
You a least want to gain head flow if doing a swap, A magnum head or milled 360 swap keep/gain cr while giving more flow, if willing do some porting can add 273/318 heads back in the mix but you can also port the magnums or 360 heads.
But really you can skip all that if it's a decent runner just the basic tune, cam, 4bbl and headers can do a lot especially with gears and a stall.
Here's a stock low cr 318 with 4bbl, headers and comp cams xe262h for 282hp @ 5000 rpms.
https://www.motortrend.com/articles/mopp-0312-318-long-block-bolt-ons/
| TORQUE SUPERFLOW 901 DYNO-TESTED AT WESTECH | |||
| RPM | BASE | MOD 1 | MOD 2 |
| 2,000 | 292 | ||
| 2,500 | 287 | ||
| 3,000 | 287 | 338 | 336 |
| 3,500 | 272 | 335 | 340 |
| 4,000 | 248 | 326 | 330 |
| 4500 | 218 | 309 | 319 |
| 5,000 | 188 | 285 | 296 |
| 5,500 | 250 | 258 |
| HORSEPOWER SUPERFLOW 901 DYNO-TESTED AT WESTECH | |||
| RPM | BASE | MOD 1 | MOD 2 |
| 2,000 | 112 | ||
| 2,500 | 137 | ||
| 3,000 | 164 | 193 | 192 |
| 3,500 | 182 | 224 | 227 |
| 4,000 | 189 | 248 | 252 |
| 4,500 | 186 | 265 | 274 |
| 5,000 | 179 | 271 | 282 |
| 5,500 | 262 | 270 |
dmopar74
Well-Known Member
In 10 pages we'll be talking about either a blown methanol powered 318 with a 500 shot of nitrous or buying a stock 360 lol.
Don't forget about the doom and gloom from the CR and velocity police
I tend to agree with 318willrun, weiand action plus or edelbrock performer manifold ( the weiand is probably the better intake but not much between them). Vac sec carb around 600cfm (holley or carter/edelbrock - whatever you are most familiar with for tuning purposes), headers and dual exhaust. Re-curve the distributor.
The comp XE250H works pretty well in a stock/near stock 318. Much bigger on the cam and you should probably look at bumping the compression ratio up a bit.
The comp XE250H works pretty well in a stock/near stock 318. Much bigger on the cam and you should probably look at bumping the compression ratio up a bit.
For a nice cruiser I have to say id rather do the 302 heads over 360 heads and just clean up the nasty in the heads (light porting) as yeah I know, 360 heads on a 318 have been done forever but a 318 is a bit low on compression anyway, I certainly wouldn't want "less" which is what plopping 360 heads on is gonna do for you...
Not if you mill the 360 head.
One of the best cheap mods you can do is recurve the distributor.
Welcome aboard!
318 Willrun covered it well.
I’ve done a few 318’s over the decades. My advice?
Don’t bother with the 302 heads, use what you have. The 302’s aren’t that good as cast but can be ported out really well. In my opinion, skip porting them UNLESS you can port them yourself! Otherwise I’d just use an aluminum head. You’d be much further along in head flow for power and money invested.
Use .028 thick gaskets.
In the future, head selection can vary. Ether port your own heads and move to 1.88/1.60 valves or spring for aluminum heads.
Any dual plane will do well with the mild modifications planned. Even a OEM cast iron 4bbl. Just use one with the least amount of emissions as possible. In a pecking order…
OEM iron or a Edelbrock Performer will be fine.
Weiand Action Plus or Stealth.
(These lack a coil mounting provision. You’ll need to figure out where to mount your coil.)
RPM- RPM-AG
Carb wise, a 600 AFB or an 650 AVS or equal Holley.
Headers - I very much so highly suggest a set of Summit headers and there 2-1/2 exhaust kit. It requires minor cutting at the tail pipe end, but can run as is.
Cam duration @.050 w/3.23 gears and a stock converter should really not exceed [email protected]. Use a split duration cam, 4-6*’s split. Grab the matching valve springs and a new timing chain.
Add in a shift improver kit to the transmission & add a cooler with a deep pan. You’ll be set there.
Then move to suspension. Shocks and springs!
ESPO.com for springs. I’m running regular Q1A shocks in all 4 corners.
Enjoy!
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junkyardhero
Well-Known Member
4bbl manifold, pretty much any dual plane (even factory!) and a 600~650 carb along with headers and a good ignition curve will do wonders.
if you have 302 heads and they require very little investment, then sure, why not. if you don't have 302 heads, there are better options. any of the "small valve" 360 heads would be good.
the key here is to find some that are in great condition, otherwise you're spending $$ for something mediocre, and that $$ would be better spent on good aftermarket heads. or magnums if you wanna roll that way.
if you do the cam, keep it small. the range that @318willrun posted upthread is a great guide.
if you have 302 heads and they require very little investment, then sure, why not. if you don't have 302 heads, there are better options. any of the "small valve" 360 heads would be good.
the key here is to find some that are in great condition, otherwise you're spending $$ for something mediocre, and that $$ would be better spent on good aftermarket heads. or magnums if you wanna roll that way.
if you do the cam, keep it small. the range that @318willrun posted upthread is a great guide.
michiganpat
Well-Known Member
magnum heads, comp XE256 cam
Skip used Magnum heads. IMO, skip them in full unless they are the MoPar R/T Magnum heads, (LMAO - Good luck finding these hens teeth.) or use Edelbrock Magnum heads. A readily available and very good choice.
SSG_Karg
Enhanced member
^^^^THIS^^^^
360 head over a 318 because flow trumps compression every time and has been proven over and over again and again.
To that end, ai’d walk right to an aluminum head over a cast iron 360 head.
Heads are basically the number 1 component for NA hp especially streetable hp, look to the LS 5.3l same basic displacement, smaller bore not overly high stock cr.
In dyno trim (headers, tune, no accessories) stock cam makes 350 hp and with a 218 @ fifty cam well into the 400 hp range and most of that is due to the heads and still pretty streetable.
Good heads can still pass a decent amount of air thru an engine even with a moderate cam, duration is just the time frame air can pass thru head determines how much air will pass thru.
Saying that a stock 318 head can pass enough air for 250-300 hp with moderate cams, which is enough hp to get an A Body down the road at a decent pace. Like I said before don't have to do it all at once, can always do more upgrades in the future, enjoy it as you go one stage to the next.
In dyno trim (headers, tune, no accessories) stock cam makes 350 hp and with a 218 @ fifty cam well into the 400 hp range and most of that is due to the heads and still pretty streetable.
Good heads can still pass a decent amount of air thru an engine even with a moderate cam, duration is just the time frame air can pass thru head determines how much air will pass thru.
Saying that a stock 318 head can pass enough air for 250-300 hp with moderate cams, which is enough hp to get an A Body down the road at a decent pace. Like I said before don't have to do it all at once, can always do more upgrades in the future, enjoy it as you go one stage to the next.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Best bang for the buck is a higher stall convertor. I like the 2800. It gives a nice jump off the line with those 3.23s.
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Do this FIRST and you will never regret it. Then install a semi-auto shift kit, and maybe your teener will bark the tires going into second.
With your planned mods, you're gonna have to do this anyway, as the factory stalls are just too low, and with any loss in cylinder pressure they will stall even lower, making taking-off an exercise in patience.
Before you take anything apart, do a compression test. Yur gonna need those numbers later after the mods are done, to help you chose a new convertor.
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Do this FIRST and you will never regret it. Then install a semi-auto shift kit, and maybe your teener will bark the tires going into second.
With your planned mods, you're gonna have to do this anyway, as the factory stalls are just too low, and with any loss in cylinder pressure they will stall even lower, making taking-off an exercise in patience.
Before you take anything apart, do a compression test. Yur gonna need those numbers later after the mods are done, to help you chose a new convertor.
send a pm to Halifaxhops here on FABO - he's right there in PA. He does a great job of checking out, repairing (if needed) and recurving your distributor. Wait until you figure out what all you want to do and send him the details on the engine, gears, etc and how you want to use the car and he will figure out what you need and deliver.
Dartfreak75
Restore it, Dont part it!
In my experience nothing "performance" Is ever cheap. Its a never ending rabbit (money) hole. I started off similar to you was going to take an 80s 318 and clean it up regasket it add a small cam a 4 bbl intake headers etc. Well I pulled the heads to find that it needed to be overbored pulled the cam it needed new cam bearings. The heads needed a valve job due to worn seats etc etc. So I figured since I needed all this machine work I'd step up and build a 360 instead. About 3 grand later my budget was blown and I had one heck of a stout 360 lol. Long story I know. Sorry. But if you can get away with it and you have a good 318 core that doesn't need new pistons or worn cylinder walls (unlikely) I would get a small cam, a four barrel intake I'm a fan of the factory 4bbl spread bore with a thermoquad on top. And a set of magnum manifolds from a 5.2 mag. If the 318 is worn out and need machine work. I'd follow some advice I got from here and never followed, I'd find a 5.2 or 5.9 mag in a junkyard or marketplace and start with it. Speedmaster has a good intake for the mag heads.
Dave999
Well-Known Member
Carb
headers
sort the ignition curve for modern fuel
new cap new rotor new leads new plugs properly gapped
clean bulkhead connector on the ignition side at least
clean earth straps
check battery clamps
make sure you see battery voltage at the input to the ballast
this alone can create a seat of the pants noticeable improvement in performance on an old car
check oil level
get 2 filters and a do a double oil change i.e another after 500-1000 miles when hot clean out the last guys gunk.
set timing
tune carb
reset timing
tweak carb/ idle rpm
go go go....
if you can get it so it has a clean tail pipe and the guy behind's eyes are not watering when you sit at the lights 99% there
that will make it "run better" even if its just getting you back to where it was 1000 miles after it left the factory
once you have a baseline plan the next move, which is usually $$$
Dave
headers
sort the ignition curve for modern fuel
new cap new rotor new leads new plugs properly gapped
clean bulkhead connector on the ignition side at least
clean earth straps
check battery clamps
make sure you see battery voltage at the input to the ballast
this alone can create a seat of the pants noticeable improvement in performance on an old car
check oil level
get 2 filters and a do a double oil change i.e another after 500-1000 miles when hot clean out the last guys gunk.
set timing
tune carb
reset timing
tweak carb/ idle rpm
go go go....
if you can get it so it has a clean tail pipe and the guy behind's eyes are not watering when you sit at the lights 99% there
that will make it "run better" even if its just getting you back to where it was 1000 miles after it left the factory
once you have a baseline plan the next move, which is usually $$$
Dave
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