Big Block or Small Block in my 70 Duster

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pauly

pauly

MOPAR or no car!
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I'm sure this has been pondered by many, but I have to ask: how much of a pain in the donkey is it to put a big block 4 speed combo in a 1970 Duster? Can I run power brakes and steering or isn't there enough room? I've looked at pics and it seems like a tight fight.

I've got a fresh 440 in the garage - this is why I ask. Otherwise, I have to rebuild the 340 that came with the car or rebuild one of my 360's. I've got the full four speed setup for the small block, but will need to find a BB bellhousing and such for the 440.

What are your thoughts?

Thanks for the help!

The Newbie!!!
 
i went with the big block just to say i have one. if i had to do it again, i'd go with the small block. there are so many nice performance parts for the small block that really wakes them up. way more room with the sb also. just my 10 cents.
 
Last summer I did a 400 into a /6 '71 Duster. It required a swap kit from http://www.engine-swaps.com/ that made life easy. They didn't have at the time the better fail safe mounts so I purchased the torque strap. That required a drilling of one hole.

Next are headers. Exhaust manifolds are possible to use IF you can get the proper units.

Being that money was tight I went to the tech pages over at Big Block .com and looked up the headers I had on hand, used out of my '79 B body car and just simply followed instructions. http://www.bigblockdart.com/techpages/techindex.shtml

Next is a drive shaft shortening to fit to the upgraded rear swap I did. The /6 was a 7-1/4. I went to the 8-3/4. The distance is a bit shorter then stock.

The next required parts you'll need/want are a better radiator and brakes.
 
I agree with Rumble, I did a 440, but used the schumacher headers which he linked to, found them either on this site or at BBD. I did mine with power steering, would not do that again, just taking up space, and there is very little of that in the bay.
 
Too me 450hp and under small block, 450hp and over big block
 
Oh crap! I have manual brakes and steering.
Sorry about that.

I did it because long ago I seem a BB Demon with a old style MoPar hood scoop. His plate read; "Kool." It was a older ride from the early 80's. the 383 power plant looked docile enuff under the hood but it would spin the monster 50's easy enuff.

It had the basics of the time. 750 Holley, Torker intake, larger tube headers on iron heads.

After getting a eye full of it, I said I'm go an do that one day. And so I have started on it.
I'm using a 400 B w/a 727 -8-3/4.
 
Thanks for the input!! The 440 I have should be about 450 hp on pump gas. I' ve got about $3K into the rebuild - was going to put it in a truck project that never materialized. It's 9.25:1 with forged pistons, .480 lift 284 duration cam, Performer RPM intake with 750 Edelbrock carb, 452 heads with stainless valves. etc.

I think I would be OK with manual steering - would like power brakes. My car has factory power discs on the front. Will probably add discs to the back too.

Did you guys upgrade the torsion bars to account for the extra weight in front? Mine seems to sit pretty low with the /6 bars in it. Obviously subframe connectors will be a must!!!

Would love to see some engine pics with the big blocks installed! Might help me make a decision!!

Thanks again for the help!
 
I do not have any pictures on my I-phone, sorry.

With P/B, you'll have clearance issues with the booster and vavle cover. It is simply a pain to get to and install.

You do not have to swap away bars for ride height. Just turn in the adjuster screw in the lower control arm to raise the car up. Though I really suggest swapping bars for a good ride and control for the street.

The /6 bar is a must have for the strip or the thinner "Drag bars" for racing.
 
Spend the money get k alteration front end with R&P

More room for PS, Zbar & headers

Go with 440

You'll like it when done. These are not daily drivers, since we are doing this we must enjoy a challenge. What the hell if you don't have any room.

Sure wish I had went with the 440 I had

Took me all night laying on the floor to change the starter on a factory 383 PS dart back in the 70s. A lift or helping hand (dad got home at midnight and helped with it) would have made it easier
 
i have had both. small block and big block abodies. to me there is just nothing like a big block abody. they are just bad ***.. anything alumn you can put on a small block you can also stick on a big block. stoker kits. no problem you can do that to either.

power steering is very tight with big blocks.. power braked i find have more clearance then manual brakes because the booster/mc is raised quite a bit..



440 in the demon i had..

41558504.jpg


22629086.jpg
 
Since you already have a 440 rebuilt just sitting there why not use it. Use the Schumacher stuff for the swap it will make the swap a lot easier.
 
oh and moroso valve covers are perfect for a 440 in an abody. they clear the mc and blower motor perfect.
 
will the moroso valve covers clear the booster too or do I need to run manual brakes? reading alot about handling. Seems to be a good consensus to run 340 torsion bars with SS springs.............planning on tying the subframe together as well. What are everyone's thoughts on the 1.03" torsion bars? Do they make the ride too stiff?

Kinda leaning towards a small block for now - just because I got all the pieces parts already! Just need to figure out what to build. 340 or 360? LOL!
 
just my two cents but id stick with the 340 if i was going to do a good amount of street driving. im building mine with a 360 because its what i got. when i do build a BB A body it will be an all out balls to the wall racing motor lol. something like a supercharged 528. On a side note the fastest car i owned i picked up from a legally blind guy(so he never got to drive it) that got it as a present from his nephew. it was a 67 valiant with a dyno blueprinted 360 with 625HP!! (on the motor) i had all the paper work drove it daily raped my wallet on gas. That car was the only car that scared me if i put my foot into it. would break the tires easy at 70mph and i only paid 1200 cash because he had it for 12 years and only ran the motor in his driveway. just wanted it gone and some one to love it.
 
pauly said:
will the moroso valve covers clear the booster too or do I need to run manual brakes? reading alot about handling. Seems to be a good consensus to run 340 torsion bars with SS springs.............planning on tying the subframe together as well. What are everyone's thoughts on the 1.03" torsion bars? Do they make the ride too stiff?

Kinda leaning towards a small block for now - just because I got all the pieces parts already! Just need to figure out what to build. 340 or 360? LOL!
Click to expand...


just about any valve cover will fit with power brakes. the booster and master cyl sit a lot higher then on a manual brake car. you actually have more room with power brakes...

is this a street car? going to see much track time?

if its more of a street car i would go with at least 1" torsion bars, no they won't make it stiff. the just suspensions 1" are the ones i have experience with and they firm the car up but are in no way stiff and thats with a small block. i would also skip the ss springs and go with a set of 6 leafs springs from espo. you can get them in +1" or +2" if you don't like stock height.
 
I have one of each. 340/4 speed hardtop and 440/auto convertible, both 68's.

My convertible is setup for manual, although I have an auto in it. You may want to look at z-bar clearance if you plan to run manual/440/headers. Hyd clutch is an option too.
 
The intention is for this to be a street car - flirting with the idea of the 440 because I have a fresh one in the garage! I may just hold onto that for a while and rebuild one of my small blocks. I've got a solid 360 core and a 340 with X heads. Might be easier on this since this is my first car build - put together a few trucks, but time for a car now.

Are the SS springs a bit on the stiff side?
 
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