Need advice on my 318
Picking up my 318 on Wednesday...it is already partially torn down. My goal is to get some extra horsepower out of it for a little money as possible.
I'd already planned on a rebuild kit for it, but while it's torn down I was thinking it might be a good idea to give it new pistons to improve the CR, and a new cam/timing chain set.
Assuming I use Keith Black domed pistons, and with the new cam (but not a new intake, headers, or carb), how much of a increase in HP can I expect?
Or would it be better to rebuild it to factory specs with a new cam and replace the intake and carb? Or machine work on the heads even? I'm ok with milling the head as long as I don't have to shave the intake as well.
In other words, of the following items, what should I go with to get to around 275-300hp?
Pistons
Cam
Intake
Carb
Head porting/bigger valves
If a new cam is definitely in the equation, what cam should I go with? I want the car to be a bit aggressive, but nothing too crazy.
To give a good answer on what you need to do we need to know what you're working with already. What all can you tell us about this 318? You said it's partially torn down but that could mean a lot of things. It it torn Down to the short block or are the heads and everything still on it? If the long block is still intact you should compression test it. What year is the engine? What kind of mileage does it have? If you have to dig into the bottom end then things can get expensive. Boring it out and putting new Pistons in isn't cheap. The new pistons won't weigh what the old ones did so a balance job wouldn't be a bad idea either, also not cheap.
Cam choice is dependent on a lot of factors. What kind of gears does the car have? You mentioned that you couldn't use the 318 with your current transmission. What kind of engine and transmission does the car already have? What kind of cylinder heads are with the 318? If you want to have bigger valves installed and have them ported, that wouldn't be cheap. Porting them yourself could save money but you could also hurt flow if you port them badly.
If you want to make a lot of power then you would have to do more to a 318 to reach those goals than you would have to do to a 360. But if you just want to have a peppy 318 that will burn some rubber then that's definitely doable. I built a 318 because I couldn't find a 340 or 360. I did it "on the cheap" too. I started with a stock '68 318. I skipped the machine shop aside from hot tanking the block and installing new cam bearings. I tore it down to the bare block and everything looked pretty good and there was a tiny ridge on the cylinder that I reamed off before I honed it. Kept the stock Pistons and just got new rings. New bearings too. While you're in there it's a good idea to replace the oil pump since it's cheap and easy to access with the pan off. Timing chain was SHOT. The thing was missing half the nylon teeth and the chain was so sloppy I'm surprised it didn't jump when I ran the engine before the tear down. I went with a true roller timing chain for the rebuild. Heads were in good shape and were recently rebuilt so I lapped in the valves and intalled COMP 901-16 springs and the heads were ready to go back on. I found an Edelbrock 600CFM 1405 carb here on FABO and bought it then rebuilt it. Got a performer intake here too (thanks Treblig!! :cheers: ). Cam is a COMP HE268 with .454/.454 lift and 268°/268° duration on a 110° LSA. I think it's 218° at .050" lift but don't quote me on that lol. It's very streetable, works with my power brakes, and it has some lope to it and sounds pretty good! I've also got Hooker Competition headers but you say you're keeping manifolds for now which would still work well with the HE268.
That's the route I took and I'm pleased with the way it performs. Not bad at all for a pretty much stock long block 318. It'll burn 295/50r15's pretty good and sounds pissed through 3" dual exhaust, especially with the electric cutouts open. A general refresh with some upgrades isn't too expensive and in the end you'll end up with a peppy engine that will be fun on the street. Will it make a ton of horsepower and lay waste to everything on the street? No, but it doesn't need to. You said your goal was to get extra horsepower from this 318 for as little as possible and I think this isnt a bad way to go about it. As far as the total costs go I think a re-ring kit is under $300 (I didn't go for a kit. I chose all my parts individually but to each is own) and has most of what you'll need. Go for a double roller timing chain at least. Don't go back with a stock one. Cam & lifters are about $200, you should be able to pick up a 600cfm vacuum secondary (or mechanical if you go with a manual transmission) for not a whole lot. I think I've got less than $150 in mine and it was almost brand new on the inside when I went to rebuild it. Intake, I say go for an LD4B if you can find one since they're for smaller 273/318 ports but a Performer 318/360 will work good and they're cheap. $100-$150 and readily available. You could build a decent performing 318 for under $1,000 that will run for many years, assuming you start with a good engine.
If the 318 you're looking at is in bad shape and needs a complete rebuild, I say find something else. Refresh = on the cheap. Rebuild = not cheap at all. I'm rebuilding a 340 for my Dart right now and I've got more money in the machine work for it than I have in my entire 318 . My cylinder heads got completely rebuilt and milled and that ran about $400, having the rods redone done with ARP bolts added was $175, balancing was $175, turning and polishing the crank was $125. You also have to figure in the cost of everything that needs done to the block and the cost of new Pistons and other parts you'll need which will add up fast. If you want to build the 318 on the cheap then re-ring it and add a mild cam, 4bbl, and dual exhaust. Maybe head porting and a gasket match if you're up for it. If it's too worn out and needs the works then you might want to look at a different engine if you're on a budget.
The more info you can give us on what your car already has, what kind of condition the 318 is in and what parts it has, and what your goal for the car is.. The better we can help you out. I think 318's are very capable little engines with some upgrades and I think it'd do good in your Dart if you want a peppy driver and not a street/strip machine.