This is my first post.

I have a 71 Dart Swinger in storage. It has a beat 318, 727, and 8 3/4 with 3.23's. I am looking to restore it in the next few years, but am researching the available engine options. I am keeping the 727, but rebuilding it with a manual valve body and better clutches as well as rebuilding the rear end. I am going to guess the car weighs 3400-3700 lbs.

As for the engine I have no specific HP goals. I am not looking for a dyno queen, this car is going to be driven 98% on the street and 2% at the track. I am not going to put a cage in it. My 1/4 goal would be something around, but slower than an 11.50. I want a fast, but easy to drive street car. I also want decent mileage since I plan on driving it a lot.

I am not new to turbo's though I have never had a turbo V-8. I have been looking at compressor maps for several different turbo options. On paper, specifically Squirrel Performance's turbo calculator, a GT40 or GT45 look like decent options. I have not yet plotted the numbers myself. Some searching on here and other forums shows that the GT45, while enough to support way more than I am looking for, spools anywhere between 3000 and 3800 rpm on similarly sized engines. This seems like a decent rpm for a street car. I plan on using Megasquirt.

As far as the engine is concerned, I am thinking .030 over, forged pistons, rods, and crankshaft. I am still wondering about Milodon's 4 bolt caps or just using studs. This should easily support the 500ish hp needed to run an 11.50. I used a quick ¼ mile time calculator for a 3600 lb car. For heads, I like the Edelbrock's for the 360, though I am concerned about valve to cylinder clearance. This car is going to be a driver, but I am not going to beat the living piss out of it.

So, with all of this said, I would love to hear comments from everyone. I have been lurking on here a few weeks and really enjoy reading about everyone's build ups. Again, I am not new to turbo's but am very new to turbo V-8's.

 

Since 318's, 340's, and 360's all cost the same to build, the first consideration is always why not a 360? Since all you have is a core anyway and sounds like you'll be buying a turbo (i.e. you don't already own a turbo sized to a ~318 engine)

 

You are right, but I already have a 318. I am open to the idea of a 360 as well. But for gas mileage reasons, generally the smaller the engine, the greater the gas mileage. I am not looking to equal a Prius though! By the time this car is done premium may cost 5$ or more.

Why does everyone always recommend the 360 instead of the 318? Aside from the difference in cubic inches, what benefits does it have over a 318?

I do not have a turbo yet. I am exploring the options.

 

the 5.2 and 5.9 mags in trucks at least return about the same mpg. Your car will be lighter so you may see a slight mpg gain from the 318.....
It might actually be a little cheaper to build the 360 as more people are building them, may offset the price of a 360 core. We still have a couple cores, but you don't have a location on your profile.

 

I am in Iowa. I am moving to Pensacola FL soon.

From my Summit racing research, it seems that cranks and pistons for the 318 and 360 are the same price. Either motor will most likely get the Edelbrock heads.

The machine work is what I am worried about. I can get a machined 318 block from PAW for 495$, the 360 is a 650$. I am worried it is going to cost me more to machine a block than just buying one that is already done.

 

small world, while I'm in Chicago, our stuff is in eastern Iowa, 52205.
We've got some 340 stuff as well, not sure if we have any forged cranks left. The 360 cores we have were all mid 70's truck engines.
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if you're interested in what we have- definitely not looking to get rich off it, it's just stuff that has been collected as parts of other deals and is just sitting.

 

Built to the same power level the 360 will be more reliable (lower rpm required to make the power) and more streetable than the 318 and probably get the same mpg.

 

Thanks, but as I stated I am here to research. I want to know the benefits of a 360 over a 318.

Are you saying more reliable since the 360 will not rev as high and therefore, in the long run, will last longer?

 

If I was building a 318 turbo car with a goal of slower than 11.50 , I think topfueldart has a great combo going , I would just follow it, very effective and proven

 

Yes. The 318 will require either more cam or more boost to make the same power as the 360. If you go with more cam that means the powerband moves up in the rpm range, and there is an inverse relationship between rpm and reliability (as one goes up the other goes down) generally speaking. If you go the more boost route you also run into less reliability because of the effects introduced by higher cylinder pressures. Either way, the 318 will need to be a bit hairier to match the 360's performance.

 

I chose a 318 over the 360, for the durability of the forged crank. I'll take the better crank over a couple cubes... My car ran mid to high 11's last year, I just changed the converter, and hope to have better numbers soon...

Buy the kit off my car so I can put on my Indy heads and start over...

 

I am not buying anything anytime soon. Sorry.

I am still leaning toward the 318, after what I put mine through way back when in high school, I think she is still up to the task. After a rebuild of course....

This is what I thought you were getting at.

Generally speaking, my car won't see boost on the street on a regular basis, if I can pick the right turbo. I still need to crunch the numbers, but at 65 mph I do not want to have the turbo spooled completely. I want to drive "under the boost" for a majority of the time.

This was my original thought.

 

put the new hemi in it

 

I have an 09 Ram with the newest of the Hemi's. It has MDS and VVT/VCT. I can only imagine the nightmare of trying to trick a PCM/TCM/ETC into thinking my 71 Dart is a Ram.

If you just meant a non-MDS Hemi, I read into it, but it looks to be more than what I want to spend.

 

if you're concerned about having the turbo boosting your engine while you're cruising you can stop worrying about it right now. When maps and calculators tell you about boost v.s. rpm what they're actually calculating the boost against is an estimated air flow in lb/min. Therefore because while cruising you're only under partial throttle you can run at 4000rpm cruising and still be in vacuum. However when in that rpm range if you punch the throttle you will build instant boost, because though the turbo isn't producing positive pressure it will still be spinning.
To me that's the beauty of the turbo, allowing you to cruise using minimal hp while getting better mileage. But when you want it you have more power. Hope that helps.

 

Thats a lesson I just learned. Thinking back its obvious how it works this way, for some reason I had it stuck in my head that 3k = in boost while cruising.

 

I should have reworded my previous post. I know I won't have positive manifold pressure at part throttle highway cruising rpm. You are right.