So I decided to keep the stock 318 in my 72 cuda.
But money being the limiting factor, I seek the wisdom of forum members to help with a "bang for buck" upgrade.

The 318 runs fine, and of course is bullet proof. I seek to add a few ponies to make it run stronger and sound better.

On the table are 3 levels I am considering:

Level I
headers / exhaust
intake manifold
650 4 bbl

Level II
add camshaft / intake manifold package to above
add porting / grinding of cyl hds to match intake

Level III
used head swap with bigger valves (will 340 hds bolts on??)

------------
Any advise regarding potential cost or additional ideas is appreciated.

Thanks.

 

im currently doing a a rebuild on my 318 in my 74 dart swinger i was just going to put a set of heads on and headers, but if your going to rip apart the motor you might as well add a better cam while your at it, summit makes some good cams for some good money make sure you are changing to a set of closed chamber heads if your 72 dosent all ready have them, also check your rocker arms they have a bad habbit of failing and allowing the push pods to punch through the bottom of the rockers if they are a poor cast

 

cuda -

I did the same thing years back, before I went to the big block.

Couple of things to consider:

1. Primary purpose of the car. Pure racing, "street stuff" and will it be used for either highway and or grocery getting.

2. For peak efficiency, ALL the parts really should work together (read - have similar power bands). So, holding off on the cam while understandable dollar wise, may be more practical to do at the same time. For example, a huge cam and stock exhausts may be a nightmare.

I like to figure out the purpose of the car, pick the cam I'll be using and then pick the other components around that.

Your plan sounds very similar to what we did to mine c1980!

Cam (Crane mild)
Old style Edelbrock Streetmaster intake + Thermoquad carb (don't laugh it worked) A 650 is a good size of a Holley depending on the cam, and a DP will get you off the line faster than a vacuum secondary.
Headers (Hooker) and new pipes
And upgraded the election ignition system.

Basic tweaking.

Later we swapped the 318 heads to 340 heads, it was a direct swap. no machine work needed. If you can "work" the heads even better. (Got lucky, even the push rods worked!)

Since you will upping the power band, consider a higher than stock stall converter, if you're running an auto trans. Likewise you may want to consider your current rear gear ratio.

Sorry can't help ya with current pricing, but consider used items if you can check them out before hand and there are "packages" that companies sell that combine compatible components.

Now that you're probably freaking out ... don't. Your plan is fine for starters, just remember the end game should be to have all components playing nice with each other.

Archer

 

Thanks all for the suggestions.

I am rethinking this by the minute, lol.

I do like the idea of just swapping out heads. Used 340 seems best with bigger valves, or should I consider new/rebuilt instead? I would also add headers, so should I add intake as well. Leaving cam alone is fine with me, but is it OK with new heads?

 

Cuda -

The new vs. rebuilt heads is going to come down to your available . The new aluminum heads will out perform any stock heads, but if you're not racing (or want bragging rights) the difference may not be worth the extra $$$.

IMHO, the cam specs are the heart of an engine. FOR MOST OF US How far and how long the values are open determines how much air / fuel can be used and how much flow is required to to let the gases exit.

I figure since the top of the engine has to come apart to do the cam, might was well do the intake and carb at the same time.

You can do the other stuff and leave the cam alone and you will notice some improvements, it just won't be an "optimal" set up. When I was racing, I did better than a lot of guys with "hotter" setups, because I had a balanced set of components.

Sorry if this stuff seems a little sporadic, mostly because it is. We don't know if you're going to have this stuff "done" or if you are going to do it yourself and what your skill set it.

The intake / carb is probably the easiest to do. The cam / timing chain (yes, you'll need a new timing chain) is trickier ( more complicated) and headers might be a royal pain, because the bolts my be stuck in the head and you'll probably need a new set of pipes / mufflers.

So guess the real question is what do you want to "do" with the car?

Archer

 

Thanks again.

More info on me and my plans.

I have some skills having reparied many things automotive, but would certainly need to follow instructions carefully if I got too deep into the motor. Swapping heads included. I am not above finding a speed shop that would do the repair, if I knew of one. I could research it I guess, but I still like the idea of wrenching on it myself first.

So, finding cast iron cyl hds for a 340 seem to be my cheapest bet then.
Assuming that path, will an intake manifold upgrade help much without changing cams? Will the stock 318 cam lift/durations jive OK with the 340 hds?
What kind of performance gain can I expect from the 340 hds, alum intake and 4 bbl carb and headers?

Thanks again.

 

cuda -

I'm not that familiar with the 72 set up (mine was a 74, guess pretty similar), but assuming you're coming from a 2V set up, you will see / hear an improvement, just don't expect it to turn into a HEMI.

You just won't be taking full advantage of the parts without the cam.

On the flip side, if you're doing this as learning experience, then it's probably the best way to go.

Level I *external stuff - have the cam in mind before you pick the stuff out
intake manifold
650 4 bbl
headers / exhaust
Consider the ignition system (box, wires, etc - not a big plus, but couldn't hurt. I'd also oose the A/C, unless it's still going to be a daily driver.)

Level II *internal stuff
add camshaft (again, this will make the biggest change)
add porting / grinding of cyl hds to match intake (might not need it and if you do, wait for the "new heads")

Level III
used head swap with bigger valves

Archer

 

360 heads are a easy swap also. bigger valves. direct bolt on. and easier to come by than 340 heads.

 

Better heads than 340, or just more abundant?

 

more abundant and cheaper - not sure about larger valves than a 340 set of heads.

Whatever you do decide to do for a build-up, you want everything to work together like Archer said. Last thing you want is a set of large, long tube headers with a cam and intake that make power only up to 5500 RPM. You may need to spend a little more to get everything just right, but the outcome will be well worth it.

 

abundant, bigger valves than 318.. same as most 340.

 

So i found a set of 68 340 X heads for dirt cheap.
But what about chamber volume and CR? Will I need to change piston, because I hear the chamber volume is big on the X and my CR will remain low.

Any thoughts.

 

cuda -

Not sure about your rig, mine just bolted on. There are some guys here who can give you the numbers check.

Archer

 

If they are 68's the casting number will be 2531894 and if they are stock heads they will have 2.02-1.60 valve combo. This was the norm until 1970.

I think all the 360 heads were 1.88 - 1.60 valves.

 

I found a 68 CI intake manifold (4bbl) for dirt cheap.
Does that make sense rather than a pricey aluminum aftermarket?
Will it have any long term benefits in terms of resale?

Thanks.

I am ready to pull the trigger on the X heads.
I was concerned about CR, but I read that the 68 340 heads had small 65cc chambers. After a 0.060" decking, I should have decent CR. Any concerns for 2.02" valve clearance to the flat 1972 318 piston?

 

i wouldnt think you would have any problems with the valves..but it wouldnt hurt to check 1st with the clay method

 

OK,
so I got the X heads. They are from 1968. The more I read, the more I think they have far more than only 65cc, as much as 72cc. Dam it. I did not want to have to pull the motor for new pistons.

So my options are decking and nail head valves and thinner gaskets. Will that be enough and what kind of CR can I expect assuming about 68cc (splitting the difference)?

Any thoughts??

 

2.02 valve will work on even a stock bore 318 I have done it a few times, even with 360 heads milled fairly heavily to 60cc no problems, people will tell you diffrent but like I said been there done that so I know it works awesome.

 

Not sure about the cc? - 1 cc of water is the same vol. as 1 cc of air, we use to take a hypo and fill the chamber up with water taking note of how many cc's of water it takes to fill it, 65 cc of water = 65 cc chambers everyday of the week.