Hi.
I have a Mercury Montclair from 1956 with a 312. The engine is out from the car for renovation of the heads and general overhaul of the engine.
I will keep it stock, but perhaps upgrade the camshaft one step from stock if possible. 
What i have is:
Stock 312 from 1956  225HP
Engineblock: Stock ECZ 6015C
Heads:Stock ECZ- C comp.9,0 :1
Intake manifold : ECZ 9425-B singel 4 barrel.
Exhaust manifold: Stock
Carburattor  : Edelbrock 1404 cfm 500
Rockerarms : ECG 6564  ratio 1.54:1
Distributor : from  y-block 1961 with Ignitor
Transmission : Merc-O-Matic 3-speed
Rear axle: stock with gear ratio 3:15

If i choose a new camshaft with stock spec. which brand has best quality (US made) and type of ? same for the lifters.
If i want little more out of the engine can i go for Isky 3000444 (E4 ) with the spec. above? or is there any camshaft in between stock camshaft and E4 with good quality?
I prefer a low and mid range camshaft , i only use the car for street and crusing, and it is importante with good idle.

E4 is good, watch the deck height and thickness of the head gasket (important) Isky or Johnson lifters are good.

Take a look at Mummert's 57+ cam. It has more lift (Ted says Y-blocks like lift) than the E4 and a wider lobe separation angle (111). Ted has recommended an E4 ground with 112 LSA vs. 108 for off-the-shelf E4. 

I ran a regrind of the 57 Blower cam for some time. Still have the engine stashed away. A bit more radical than the stock 57 cam but a good mild street cam. Not sure exactly how this compares to the Isky E4.

Oregon Cams, out of Vancouver Wash, can make a copy the 1957 Cam, which is a step up from your 1956 Cam, assuming that your engine wasn't overhauled at some point previously?. I mention that because Ford's factory replacements after '57 were actually '55 cams or according to Mummert, close to truck spec's.. A  '57 cam has more lift & duration than the earlier Cams, but not enough to cause issues with the auto trans.. .


Paul

Ok, tanks for info. do you think it is special valve springs for a -57 stock camshaft?

For whatever it’s worth I have an Isky E4 in my 312 and am very happy with the low to midrange performance. I have a 55 T-Bird w/T-86 3 speed OD and non OD 3.78 rear. It wakes up around 1,000 rpm.

1955 312 T-Bird Warwick, NY

The cam grinder/manufacturer will recommend spring specs, which are usually found on the cam card. The stock cam has about .400 lift at the valves. As the lift goes up, so should the spring pressure. Usually cam and springs come from the same source, but not always.

ther is a cam grinder in vancouver  canada,he has the 57 312 pattern works well re the3 lifters I have a set of regrind lifters(the top for higher lift cams,5,00 each
have had great results with blocking the return tubes and  having pressure lube for all valve train.ofcoarce at least removing  rocker shaft core  plugs  and cleaning out the sludge that accumulates back from  drain tubes.if your heads are redbuilt and new valve seals no issues. also is you take .030 off the heads and use thecmposition gaskets you will be the same compression as the old shim gaskets.measures a set of commission gaskets after use and they wher .030 thicker than steel ones cam grinder is Shadbolt cams Vancouver canada. 604 732 9505

Ken Heard of Oregon Cams will be happy to answer any questions you might have. Ken, and Jerry Cantrell of Schneider Racing Cams have been most helpful. Although I've yet to install it, I ended up purchasing Schneider's 258 Y-block cam. If you have some idea what you want, you can go to Oregon Cams' website, click on "Mechanical Cams" and take a look at their numerous grinds. For your particular application, Ken might suggest a custom grind. They can either regrind your cam or supply a new one. They also regrind y-block lifters. Tim McMaster (y-blockguy.com) has used their products.