“Max effort daily driver” 318 build vs “Budget” 400 swap

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Charlie_es_cool

Charlie_es_cool

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Hello everyone. I am in the middle of this dilemma right now and I wanted to hear your thoughts and ideas on it.

I have a 75 Dart Sport with a 318 in it. My initial plan was just to rebuild it. But in January I acquired a 400/727 combo and now I’m kinda torn on what I should do.

For the 318 build I was considering around 9.5 compression, edelbrock heads, flat top pistons and going for quench, not going ham on camshaft selection, etc. Also, I have in my possession several intakes to choose from for a small block build. I even have an old edelbrock dual quad one if I wanted to turn the cool factor up as well. My car already has headers which I would re-use. Logistically this build would be very simple.

On the other hand, for the 400 I would be needing to buy quite a few stuff before I even get to start spending on the engine itself. I would need headers, a new distributor, and the appropriate oil pan just to get it in my car. It came with a 2bbl, so I would need to get a 4bbl manifold for it. This eats into my budget so if I were to follow this route, I would keep the factory heads and do some porting on them. Valve guides are good so no need to do a full recondition on them. However, I would have 2.14 valves installed since the 2.08s are sunken from a previous rebuild. And on pistons, I’d be using the crappy cast ones. This means a compression ratio around 8:1 after milling the heads. And yes, I would need to buy new pistons since the block has to be bored.

I did some math and I would spend approximately the same on either of these two builds. My car is a regular driver, and I’m putting in a trac loc 8.25 rear end with 3.21 gears.

What are your thoughts? “Max effort daily driver” 318 or should I let my inner teenager take over and swap in a low compression big block?
 
I'm doing a 318 now and my last car was a 400.. do the 400, the 318 cost will spiral out of control and 400's can make decent power with a cam/intake (depending on what you consider decent power) Personally i love 400's if i had one laying around i wouldn't be messing with the 318 at all

P.S. i had the heads on my 400 milled i think it was .080 (been a LONG time) and it ran great and didn't cost much at the time.
 
I vote build the one that gets it going the soonest. The 318.
 
Im a fan of the BB swap. But I’ve never built a Mopar in PR, so if I was you I would build whichever motor has the better parts availability/affordability.
 
Scrap both and get a 360 built, best of both worlds, fits easily, parts are plentiful, plenty of torque and HP and very street drivable. And maybe even good mpg
 
Spend that same amount on a maxed out 318 or spend the same on a 400 that has room to grow?

Thats a no brainer
 
Charlie_es_cool said:
Hello everyone. I am in the middle of this dilemma right now and I wanted to hear your thoughts and ideas on it.

I have a 75 Dart Sport with a 318 in it. My initial plan was just to rebuild it. But in January I acquired a 400/727 combo and now I’m kinda torn on what I should do.

For the 318 build I was considering around 9.5 compression, edelbrock heads, flat top pistons and going for quench, not going ham on camshaft selection, etc. Also, I have in my possession several intakes to choose from for a small block build. I even have an old edelbrock dual quad one if I wanted to turn the cool factor up as well. My car already has headers which I would re-use. Logistically this build would be very simple.

On the other hand, for the 400 I would be needing to buy quite a few stuff before I even get to start spending on the engine itself. I would need headers, a new distributor, and the appropriate oil pan just to get it in my car. It came with a 2bbl, so I would need to get a 4bbl manifold for it. This eats into my budget so if I were to follow this route, I would keep the factory heads and do some porting on them. Valve guides are good so no need to do a full recondition on them. However, I would have 2.14 valves installed since the 2.08s are sunken from a previous rebuild. And on pistons, I’d be using the crappy cast ones. This means a compression ratio around 8:1 after milling the heads. And yes, I would need to buy new pistons since the block has to be bored.

I did some math and I would spend approximately the same on either of these two builds. My car is a regular driver, and I’m putting in a trac loc 8.25 rear end with 3.21 gears.

What are your thoughts? “Max effort daily driver” 318 or should I let my inner teenager take over and swap in a low compression big block?
Click to expand...

Find a 5.9 magnum with accessories and go have fun.
 
MMissile said:
BB is heavy. Need better parts for suspension and braking.
Click to expand...

A passenger weighs more than the weight difference of the engines.
With alum heads, the difference shrinks.
Front suspension really doesn't require any changes to support a bit more weight. A re-alignment and adjustment of the torsion bars usually works fine. I know my car doesn't dip much when I stand on the bumper, and I weigh far more than the difference between a SB and a BB.

If it were me, comparing putting alum heads on a SB vs putting headers on a BB, I'd be going with the BB and still looking at alum heads. Sell a few SB intakes to fund a BB intake and it's a wash other than the headers, oil pan, and distributor. It's also helpful that the SB is already in the car, keeping it driveable while the new BB setup is being assembled, which means time can be taken to find deals on used parts rather than paying full retail to assemble.

This is how I look at it, at least.
 
Phreakish said:
A passenger weighs more than the weight difference of the engines.
With alum heads, the difference shrinks.
Front suspension really doesn't require any changes to support a bit more weight. A re-alignment and adjustment of the torsion bars usually works fine. I know my car doesn't dip much when I stand on the bumper, and I weigh far more than the difference between a SB and a BB.

If it were me, comparing putting alum heads on a SB vs putting headers on a BB, I'd be going with the BB and still looking at alum heads. Sell a few SB intakes to fund a BB intake and it's a wash other than the headers, oil pan, and distributor. It's also helpful that the SB is already in the car, keeping it driveable while the new BB setup is being assembled, which means time can be taken to find deals on used parts rather than paying full retail to assemble.

This is how I look at it, at least.
Click to expand...
Yeah if the car currently runs and drives and parts are fairly easy to obtain, I’d build the 400 while still driving the car, then swap out the drivetrains one weekend and be back on the road with newfound power!
 
Sounds ripe for a 451 or 470 build.
If I had a choice between a 318, 360 or 400 block, the 400 would be my choice.
 
MMissile said:
BB is heavy. Need better parts for suspension and braking.
Click to expand...
Tree’d by 318WR. My Duster is an4 wheel drum car and it had no problem stopping the extra weight. Brake fade is an issue of used in traffic repeatedly & at lengths of time. But no real worry. Drive accordingly.

I’ve done both and I’ll tell ya the 400 is well worth it.
Rebuild the 400 with some reasonable compression, give it a cam that fits the target goal. If you can afford the aluminum, shower the engine with as much as possible to reduce weight.

I had an iron headed 400 in a Duster and you can feel the extra weight. Change it aluminum and it’ll weigh the same or less than a small block. Parts choice will determine final weight loss.

You can of course get the intake and head made of aluminum but also the water pump housing and the pump it’s self in aluminum. Also, the pulleys can be had in aluminum as well.

On a 400, the water pump housing is on the same side as a small block and I got mine from 440source.com I swapped the 318 out and slammed in that 400 quick and easy. I got a larger radiator from Summit racing since the /6 radiator wasn’t up to snuff for the 318. I had a driveshaft cut down to fit the different length of the 727/8-3/4 from the original equipment/6-904-8-1/4.

Edelbrock or Trickflow heads and TTI headers will allow that thing to rock and roll really well. Go for the 400!
 
When you nail the throttle, torque is what you feel. The 400 is always going to have more......
 
After going through all the comments, I’m starting to lean towards swapping in the 400.

I kinda wanted the 318 build to make more sense since it would be logistically easier. But the more I think about it, the big block makes more sense in the context I would use my car. I will drive it a lot and would spend 99% of the time being driven like a granny.

The big block has a bigger bore and bigger valves. With some porting my cast iron heads should beat the small block edelbrocks easily up to .400 lift. I can have the heads milled to bring compression up to 8.5 and run a small cam on a 108 LSA like an Isky 262, and the big block will make more power and torque than the higher compression 318. I might be a able to run it on crappy 87 octane even. And if in the future I find myself financially able to build a proper big block stroker, the car is already set up for it.

I can always build a small block screamer later for another car. And regarding building a 360LA or Magnum instead, I have thought of that too. 360 LAs are hard to come across here in PR, but there’s plenty of junk 1990s Rams and Durangos I could pull an engine and trans from. It would be an easier swap vs swapping in a big block, and cheaper. But again, a big block would beat it in airflow through the heads and torque.
 
Charlie_es_cool said:
After going through all the comments, I’m starting to lean towards swapping in the 400.

I kinda wanted the 318 build to make more sense since it would be logistically easier. But the more I think about it, the big block makes more sense in the context I would use my car. I will drive it a lot and would spend 99% of the time being driven like a granny.

The big block has a bigger bore and bigger valves. With some porting my cast iron heads should beat the small block edelbrocks easily up to .400 lift. I can have the heads milled to bring compression up to 8.5 and run a small cam on a 108 LSA like an Isky 262, and the big block will make more power and torque than the higher compression 318. I might be a able to run it on crappy 87 octane even. And if in the future I find myself financially able to build a proper big block stroker, the car is already set up for it.

I can always build a small block screamer later for another car. And regarding building a 360LA or Magnum instead, I have thought of that too. 360 LAs are hard to come across here in PR, but there’s plenty of junk 1990s Rams and Durangos I could pull an engine and trans from. It would be an easier swap vs swapping in a big block, and cheaper. But again, a big block would beat it in airflow through the heads and torque.
Click to expand...
Now, if a 5.9 magnum is on the table, I might not pick the low compression 400. If you put an air gap manifold, 750 cfm carb and headers you will be over 1hp per cubic inch easy. Cam swap makes it 400hp.

Stay away from the later transmissions unless you plan to rebuild and upgrade a few things. A regular small block 727 is perfect.
 
Dana67Dart said:
Even against a stroked 360?
Click to expand...
The torque curves come in differently due to stroke.
Am selection becomes critical in an attempt to level the playing field.
For some insight, check the engine masters show on the 383 MoPar vs the 383 Chevy.
MidnightSwinger said:
Now, if a 5.9 magnum is on the table, I might not pick the low compression 400. If you put an air gap manifold, 750 cfm carb and headers you will be over 1hp per cubic inch easy. Cam swap makes it 400hp.

Stay away from the later transmissions unless you plan to rebuild and upgrade a few things. A regular small block 727 is perfect.
Click to expand...
Like! Exactly what I’m doing. But less cam than the MP create 380hp engine.
 
rumblefish360 said:
The torque curves come in differently due to stroke.
Am selection becomes critical in an attempt to level the playing field.
For some insight, check the engine masters show on the 383 MoPar vs the 383 Chevy.

Like! Exactly what I’m doing. But less cam than the MP create 380hp engine.
Click to expand...
Is the MP cam a bit lumpy?

P.S. nevermind just looked it up.. :)
 
Charlie_es_cool said:
After going through all the comments, I’m starting to lean towards swapping in the 400.

I kinda wanted the 318 build to make more sense since it would be logistically easier. But the more I think about it, the big block makes more sense in the context I would use my car. I will drive it a lot and would spend 99% of the time being driven like a granny.

The big block has a bigger bore and bigger valves. With some porting my cast iron heads should beat the small block edelbrocks easily up to .400 lift. I can have the heads milled to bring compression up to 8.5 and run a small cam on a 108 LSA like an Isky 262, and the big block will make more power and torque than the higher compression 318. I might be a able to run it on crappy 87 octane even. And if in the future I find myself financially able to build a proper big block stroker, the car is already set up for it.

I can always build a small block screamer later for another car. And regarding building a 360LA or Magnum instead, I have thought of that too. 360 LAs are hard to come across here in PR, but there’s plenty of junk 1990s Rams and Durangos I could pull an engine and trans from. It would be an easier swap vs swapping in a big block, and cheaper. But again, a big block would beat it in airflow through the heads and torque.
Click to expand...
This is exact how I feel. The short stroke is t a bad thing unless you over cam the crap out of it. Proper converter stall and gear should be thought about and well applied. Same with engine parts complimenting each other.

All in all, the 400 (383 too!) is a good small cubic inch big block. I’ll not argue bigger is better but as delivered, big bore for great breathing, generous valve sizes which are better with an after market head for really good breathing with good intake and exhaust system. It becomes a natural power maker without getting nuts on things.
 
Icetech said:
Is the MP cam a bit lumpy?

P.S. nevermind just looked it up.. :)
Click to expand...
A lot depends on the cam and it’s overlap/LSA.
In general, they’re not bad cams, not at all. Some will argue and split hairs on things and that’s fine. I have noticed one thing is a constant, there’s always a better cam. Unless you sit down and have a program predicting the best part or you have dyno’d a thousand cams for that exact combo, you’ll never really know and everyone’s opinion is just that.
 
one of my favorite motors was my 400 in a challenger... had a little .484 purple shaft and i loved that thing.. i put in a .509 and hated it :(
 
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