What do you think about this 318 stroker build?

[arsinist01]

So I've been doing some research about building a 318 up to a 390(ish). Here is what I've come up with so far. Let me know what you guys think.

4 inch crank
new rods and pistons (flat top, hoping for 9.5:1 ish CR)
Cam 256/262 duration with 454/475 lift
Weiand dual plane intake
670 cfm 4 barrel carb (comes with intake and cam as a package)
Edelbrock performer RPM heads (2.02 intake 1.6 exhaust, 63 cc combustion chamber)
Long tube headers (either hedman, hedman is way cheaper so those may win out, or TTI)

My whole goal here is to keep it a fairly mild stroker build. Hoping for around 400 hp anything more than that is just gravy. Wanted a good increase in tq too (450 lbs or so), hence the stroker kit (that and it's always fun to be a little different). Hoping this will be very streetable, and still be able to get 20 mpg on the hwy (I have gotten a max of 27 so far ). The mpg worry is one of the reasons why I am hoping I can stick to this carb, and I doubt I'll be winding this motor up a whole bunch. Maybe a couple stop light to stop light jumps here and there lol.

I will most likely do the headers first. Then the top end package (cam, intake mani, and carb). Then do the stroker and heads at a later time. Another reason I like this build I can do it when I can afford it and still drive the car!

 

[rm21h8a]

Stroker is the only way to go for a small block. I built a 416 out of a 340 with w2 heads and was very impressed with the way it ran. I see no issue using a 318 block. Id probably use a 318 magnum block so you can run a roller cam.

 

[arsinist01]

My whole goal though is to stick with the original block. For 1 it will save me money and for 2 it is the original motor that the car came with so it is also kinda nice to keep it around for that reason.

 

[Southernman]

My whole goal though is to stick with the original block. For 1 it will save me money and for 2 it is the original motor that the car came with so it is also kinda nice to keep it around for that reason.

Arsonist, I think you have a good plan for that 318. They make great street/strip engines. The only thing I'd question is the choice of heads (assuming you're on a budget); The aluminum Edelbrock heads will flow considerable air over the stock 318's and 360's and they can use more cam than you have specified if you want to take advantage of them.

Given the cam you've spec'd, I'd just clean up a good set of 360 heads, do a little porting 1/2-3/4" into the ports, and screw it back together. I've ran the 360 heads with the .508 cam on many occasions (4 spd) and they screamed. I only share this because the Edelbrock heads are a considerable investment, but they also give you something to build on later if you choose.

Good luck with the build and let us know how it goes.

Southernman

 

[Meep-Meep]

I wouldn't go less than 112 lobe separation on the cam and expect good mileage and street drivability. The carb choice is also important and I'd go with an AFB. Or if you go with a Holley then you may consider getting an aftermarket metering block that is dialed in for your combo. I think there is a lot left on the table in terms of carb tuning and a dyno tune will be the only way to sort it out.

 

[arsinist01]

Arsonist, I think you have a good plan for that 318. They make great street/strip engines. The only thing I'd question is the choice of heads (assuming you're on a budget); The aluminum Edelbrock heads will flow considerable air over the stock 318's and 360's and they can use more cam than you have specified if you want to take advantage of them.

Given the cam you've spec'd, I'd just clean up a good set of 360 heads, do a little porting 1/2-3/4" into the ports, and screw it back together. I've ran the 360 heads with the .508 cam on many occasions (4 spd) and they screamed. I only share this because the Edelbrock heads are a considerable investment, but they also give you something to build on later if you choose.

Good luck with the build and let us know how it goes.

Southernman

The only reason I picked those heads is because quite frankly I do not have a ton of experience in building engines. As a matter of fact this will be my first lol. I will probably have the bottom end done by a shop. I'm not that familiar with what specs I should build 360 heads out to so if you could give me a little more info on what I should do for them (exact specs) that would be great. Otherwise I may just toss them to a machine shop and let them know what I am doing and hope they get it right lol.

I wouldn't go less than 112 lobe separation on the cam and expect good mileage and street drivability. The carb choice is also important and I'd go with an AFB. Or if you go with a Holley then you may consider getting an aftermarket metering block that is dialed in for your combo. I think there is a lot left on the table in terms of carb tuning and a dyno tune will be the only way to sort it out.

Unfortunately I am not sure what carb comes in the kit I am looking at. It just gives the specs not the brand name. Although I am sure that I could call and probably find that out. I did look up the specs for the cam again and it has a 112 lobe seperation. As for a dyno tune that sounds like a good idea, and I know a shop that will be able to do that for me. I just hope they won't go making huge adjustments to the jets in the carb lol. I'd really hate to go under the mpg I want.

 

[Belvedere]

Sounds good. Only things I would do differently are: If using alum heads build for 10.5 comp ratio, use 750 vac. sec carb, and get the RPM heads and matching cam from a reputable source. I recommend Dwayne Porter. Wish I had done the 318 in my Belv like yours.

 

[snakeoil24]

Building a 318 to a 390 sounds nice, but building a big block is just easier.

 

[Powerflite]

Small bore and large stroke is a good combo for mpg because you get a large amount of low rpm torque for the given displacement. Then couple it with high gears to keep the rpms low. 390 cubic inches isn't very small though, and it will be a lot harder to keep your foot out of it afterward ;)

For a street car, I prefer the original AVS style carb or fuel injection.

 

[Coronet 500]

Sounds good, I would go 10-10.5 compression with the aluminum heads. Find a real Mopar engine builder, don't trust any machine shop you come across. Piston to head clearance is important for quench and mixture turbulence to prevent detonation. Good main cap studs before line honing, block oil modifications and a baffled pan are good insurance.
I don't mind that 670 carb, but I would probably go with the 750 and bigger cam for my own build. The heads are a good idea as many have said after putting money into 40yr old heads might aswell by the Ed's, I did. Get good valve gear and measure your pushrods last before purchasing them. Good Luck.