1970 Duster 360 build help

-
J

Johnlow151

Member
Joined
Jul 30, 2019
Messages
7
Reaction score
1
Location
Massachusetts
I am building my 1970 Duster from the ground up and am looking for help on the engine, I want to build a 360 magnum for around 450 horsepower. I plan on keeping it on pump gas and want to keep it for street use primarily. Looking to throw a carb on it as well. Any suggestions for which route I should go on the 360? Stroker crank or no? Im 16 and I’ve been working at a dealership as a mechanic for a while and have saved some money for the project, around 4000 for max price
 
Is there an ET your looking to go for?

450hp in a track only car can be made several different ways. The opinions and suggestions can and will be MANY!!!!

Perhaps a click into the racers forum section where there are stickies up top to run the 1/4 (sometimes the 1/8th is listed) would be a helpful guide.

You don’t need a stroker to make 450 HP. It can be done with a 318!

Contact Tony here at FABO
( 70aarcuda )
Tony runs really well without Exotic Parts in a 360 cubic inch engine. You can flatter him by following his Recipe.

4K is a little light on the budget.
 
Like Rumble said 450 is easier with a track car
big cam- no low end really loose converter, low gears over rev it so it does not bog when it shrifts

So forget big numbers for on the street- just lie
what gear and cruze rpm- much freeway driving?
much stop and go
daily driver or Saturday night special
what gas and is mileage important- like a long commute
what compression to go with the gas and heads question
stock heads or something with a more modern combustion chamber like late model 360 or Magnum , Engine quest or some aluminum
we need a lot more details
but think of a big fat torque curve that you can drive at a large range of rpms
 
I’m mainly using it to drive street, but i want to be able to do some 1/4 mile for fun. I’ve already built a 727 torquflite and have built a 318 and a bunch of small block chevys so I have some experience building motors. I would rather build my motor than buy a crate engine because it’s fun to do and is more respectable. I’m looking to run on pump gas, maybe 10.5 to 1 compression with a 62cc combustion chamber?
 
gears? stock converter?
HP converter? (what diameter converter?)
62 cc chamber but which heads
early stock ones or 508 or ???
the early ones take more timing which shows they are not as efficient
do you have access to a machine shop or auto shop class so you can do your own valve and seat work?
power is in the heads so start there?
if stock heads with no work you are lift limited and flow limited which leads to longer duration cams to get power which hurts your low end
I would not put any money into early stock heads
go aftermarket
If you can do your own work it's easy to make old iron work about as well as OTB aftermarket- for less $$$ and make your HP goal
 
I’m looking for a fairly decent cam, at least 500 lift. And I was trying to decide between w2 and edelbrock performer rpm heads
 
In a sense, the W2 can be cheaper and better to build than the purchase of Edelbrock heads, here’s why.

1: Once you get the E head, more money to check them out.

2: Will the valve springs be enough? More money?

3: The W2 comes bare so the valve train, springs, retainers and locks will need to be purchased but they will be for your set up. Not limited to the as delivered springs.

The draw back is valves to purchase and more slightly more expensive rocker set up. Also a Dedicated W-2 and take. But they can be found relatively cheap on eBay or before.

But you’ll have a much nicer and more powerful head in the end.

It is a bit of a catch 22. You can still run really well with Edelbrock heads.

The cost of good heads done by a competent machinist will eat up your budget. At approximately $1500 for the pair delivered......

IMO, go for the new Trick Flow heads and the rockers needed. Use a high lift camshaft to take advantage of the cylinder heads air flow potential.
 
On the street;
A stock Magnum 5.2 does pretty good with something like 4.30 gears and a 2800TC.
The point is this; on the street your car is a one or two gear deal. You don't need 400/450 hp to have a good time. Wind resistance sucks power so if you want to hit 100 mph or more in the quarter, that's gonna take power; and the right rear gears with the right TC. So the 4.30s and 2800 are already a step in that direction.
Remember the lowly early 70s Duster/Demon/Darts with 340s. They were advertised at 275 hp, and some actually made ~300. In those days, I never heard one person ever say their 340 was a turd, and very few of them, in stock form, broke 100mph trap. Those cars were super fun with 3.91s to 4.10s and the factory ~2500TC.
Jus saying.
 
Well the point of making the 450 horse is to make it something special for the most part, and some nice tire shredding power. I do think I might go with the w2 heads, can anyone recommend and parts for the rest of the motor? Pistons, cam and springs?
 
still the question can you do your own head work makes even more sense with W2 or pulling new edelbrocks apart to check the guides and then seat concentricity
forget "lapping" the seats move when they get hot
If w2 think about the 11/32 conversion guides and think long chevy valves
nice 7 angle valve job then blend the bowls yourself
have your special w2 manifold in hand ahead of time
dual plane for the mostly street and no huge race carb
you will have more HP and mid range torque than edelbrocks or trick flows and spend less
rockers for the W2 will be adjustable and you will need shaft spacers- go the B3 website and read the three tech articles
you will need this tech if you use any roller tip rockers or special length valves unless you really plan ahead example (550 lift with a .050 longer than stock valve puts the mid lift right at stock with iron rockers)
B3 Racing Engines LLC - Mopar Rocker Arm Geometry Tech

cost out the rockers and manifold as part of any W2 build
 
450 is special allrightee, but I bet in 12years I mighta whipped mine a couple of dozen times. Mostly they are just grazers. I mean any more than 4 or 5 seconds at WOT and I'll be speeding anywhere in Manitoba, and since the tires (Either 295s or 325s) are spinning, the horses got it easy. With 3.55s; top of first gear (manual trans) is 50mph, and top of second is over 80mph.
I had every bit as much fun with the previous combo that would only do 106 in the quarter, which maths out to ~340 hp. And that combo was exponentially easier on gas. Actually I had more fun, cuz the bottom-end, and some of the midrange, was torquier.
But hey, if at your age you got the cash, then whatever; just make sure you don't neglect the suspension, steering, and brakes. And bolt your seats in properly with well-anchored belts.
Here's a tip; but on your full-face helmet,and your racing gloves, then run as fast and hard as you can at a brickwall, and don't hold back.At the last second, just try and stop your face from grinding into the bricks using your hands and arms. Ok how fast were you going when it started to hurt? Well if you're really,really fast that would be ~27feet per second, meh about 18mph. What's the point you ask? Well, if you have to ask, then you don't get it.
7seconds at WOT will get you over 80plus mph; maybe into the 90s. If you can't stop when you need to, you should at least be able to steer around whatever is in your way, minding it's own business. You'll need the maximum amount of sticky tire that you can fit on that Duster;front and rear just to save your azz when things go wrong;and they will go wrong. That's not a curse, that's a prophecy.
 
:rofl: what AJ said, Run at the brick wall... Funny this is, Foot LB's is what spins the tires not HP. I'm more happy with the 400 FT LB and 375 HP out of my mild 340 build, sure gets off the line quick. But tell you what the FirmFeel upgrades to the front and better brakes makes the car a ton more fun than not having that 75 extra HP...
 
If you need an engine and tranny to start with, buy a 94-95 ram or durango or dakota with a 5.9 and rh42 or eh46.
They are $400-$1000 around here with a bad motor or a bad tranny. Usually bad tranny good engines.
 
Scody21 said:
:rofl: what AJ said, Run at the brick wall... Funny this is, Foot LB's is what spins the tires not HP. I'm more happy with the 400 FT LB and 375 HP out of my mild 340 build, sure gets off the line quick. But tell you what the FirmFeel upgrades to the front and better brakes makes the car a ton more fun than not having that 75 extra HP...
Click to expand...
Exactly; 400ftlbs is a funtastic experience. Sure you can get that with a 450hp 360, or a 375/340 or maybe a 300/318 or any stroker. But getting it at 2800 well, that kindof limits your options. Still, slam some gears in it and 400 at 3600 is still a blast. And it only takes a few microseconds longer to hit 65mph. And for kicks; perhaps 95% or more of your street-engine's life is gonna be spent below ~4000rpm ............... So why build a 7000rpm engine for the other 5%? For that; just install a nitrous system, and let her buck. Ok here's an idea I pulled off the backburner; run an Offy DualPort over/under, and a spreadbore. Set it up for say 350 on gas and a 150/200 shot; whoa! ............... Get yur own filling apparatus. Ok wait, I think I've had better ideas,lol.:poke:
 
If you are serious about a W2 contact Krooser on this forum
He has a knack of building economical W2 builds
again you will need seat and guide work
but you do not have to do much with W2 to have them work better than any Edelbrock or other standard rocker arm LA head
 
Ok, taking your 450 hp goal to heart, I would buy a 4” scat cast crank rotating assembly with the dished piston. A foundation that will live very happily at your performance level. You can then either do an “temporary” head choice. Meaning making the heads you have mechanically sound and choosing a cam that will work with those heads without hurting anything and enjoy the car knowing you will be leaving a bunch on power on the table until you swap over to your “final” head/cam choice. Gives you time to save more for better heads but still enjoy the car or just save up so your budget can cover the “final” head choice from the get go. If you think you are going to start chasing power then maybe forged crank. 450hp on the street is a bunch, for me there is no such thing as to much power! That being said my car will KILL ME in the blink of an eye! This is not just talk, things happen VERY quickly at that power level. Little things like painted lines on the road matter, my car shifted down with one tire on the fog line, Caught it halfway through the breakdown lane. Make it stop and make it turn then make it go.
 
No dual planes for W2’s unless there is actually a MP intake stuffed somewhere in a back room. Make sure it is a standard deck intake as there are 3 different deck heights to look for when shopping for an intake.

The best street intake for the W2 is the Holley Street Dominator. It is an narrow runner version of the strip dominator.

A suggestion on building a street W2 head?

Smaller valve guides from 3/8ths down to 11/32. Tall +.100 (give or take) stainless steel W2 valves @ 2.08/1.60, have them ported. It doesn’t have to be a max effort porting job. Though more cfm the better.

Harland Sharp has bolt on rockers, TD rockers are better and worth the expense and headache of the extra work involved.
Go with a 1.6 ratio rocker.
Use with 3/8 pushrods.

As for a cam, I’d go straight to a solid flat tappet to keep costs down on your small 4K budget.
 
I heard that the stock magnum 360 heads flow pretty well too. Is there any point in having those ported or are they junk?
 
Yes and no. The as cast OE Magnum head flows fine and for an everyday driver to a light bracket engine, there just fine. A great example is the old MoPar crate engine. The 360/380hp. Porting just helps more air in and out helping that air pump make more power.

That is a stock long block with an upgraded cam, M1 single plane intake to be finished off as per what MoPar said to do, (IIRC) 1-3/4 headers and a 750 carb. These routinely dyno’d in the 410/420hp area.

Not bad for a stock head on a 9.0-1 engine huh? I met a bunch of guys at E-Town running mid rolls 12’s with those crate engines.

I think everyone’s hang up on porting a stock iron heads is expense and the ultimate flow numbers. I still find porting and iron head a completely fine and very slightly cheaper valve able route than new aluminum. After all, you already have the head!

And that’s were people have fits. “But the aluminum is only $*** more and you get better flow. And I save 50lbs.!!!!” As always, a better HP making part is more money. Your call. Is 50 lbs. worth it to you who is rarely or never at the track? Even if you go to the track, the weight loss is great for sure, but is it going to get you a Victory just because it is aluminum? The way some people talk about it you would think it would!

How many heads up racers are out there at the track competing everyday for money? It is mostly bracket racing where Consistency counts!
Let’s get serious here for a second, the 50lbs. Diff, you will NEVER EVER FEEL.
Even when you do all aluminum parts on your iron block, while it helps a good bit in the search for speed, your never going to know in a street ride if it is aluminum or iron intake & headed. And at the track, all that counts is crossing the finish line first. NO one gives two craps what your running.
 

rumble is pretty close to spot on
you can get 400 hp out of stock magnum heads
problem is cracking so Pressure test and mag any used head
as with any factory head if they have already had a valve job then inspect closely to see if ex seats are needed the electro/induction hardening in not thick
Read the DIY porting sticky at the top of the page
Basically on a street build I let the SERDI do most of the work and then blend the transition from cut to stock port
anything else, including short side, starts to cost real money so DIY
no use enlarging the port entrances, that's not where the restriction is
 
Cracked heads are over rated on causing worry needlessly among the crowd. Not for nothing, you don't know there cracked, not until you look. The Damm engine will run fine.

You cause to much worry Wyrm. Ya gonna freak the kid out.
 
You must log in or register to reply here.
-
Back
Top