I am trying to decide between a comp cams 306 or 503.does anyone have experience with either of theese? my 93 LT1 is basicly stock other than magnaflows and 3.73 gears. I will be installing a 2500 stall convertor and headers. I love the idle of the 306

clip of the 306 at idle
http://video.google.com/videoplay?do...49787895002018

 

I run a 503 in my motor. I've got a bit more stall (3000), but less gear (3.23). It drives very nice. My car is not a daily driver, but it could be if it had to. Gets 15-16" vacuum at 900 rpms, yet still has a nice lope to it. The 306 is a bit more agressive, about the largest you can go on stock heads. You might need a bit more converter if you end up going with the 306. I would go with the 503.

 

And if a factor , from all accounts the 503 will pass emisions were as the 306 won't.
With stock heads you will probably not see the full potential of the 306

 

It won't? Tell that to my Vette. Passed fine on the Im240 emissions dyno.

The 306 was DESIGNED for stock heads. It's all about getting the most out of a crappy exhaust port.

Now with that said, I still don't like the 306 cam and am going BACK to the 503 this fall. The 306 is great for spinning the motor to 6500, but sucks for cruise.

-- Joe

 

Here's a 503 sound clip from my car if it helps.

Click here to watch 1988-PC-corvette001133--000-4531-sedited

Note: in this clip, car was started cold. Coolant temp was around 100F. Also, in this recording its idling primarily on the warm park table at around 750 rpm (due to some intermittent RFI on the speedo), this is slightly below my normal 800 rpm PID target, so its a bit choppier than my normal hot idle, but is still acceptable.

 

why does it suck on cruise?

 

I have a CC306 cam in my iron headed 383 and it is still a perfect daily driver in the city or highway. 14 mpg in town and about 25 mpg on the highway. It also does well on a high speed cruise >70 mph. Don't necessarily know how it "sucks", since the cam does very well in my Vette, but I guess different strokes for different folks.

 

Because on my setup, the dcr is too low (like 7.3). So on cruise (1600rpm) on normal highway speeds in overdrive, OR normal backroad speeds in overdrive (35-38mph) the motor will often have surges.

If I was running more compression, or had iron heads, OR had more geer and cruised above 2k it wouldn't be that much of a problem. The cam has 74 degrees of overlap.

Saying 1 cam or the other is great is a whole lot of crap, until you sit down and calculate the whole package. Even then, real world might behave differently than your on-paper calculations.

-- Joe

 

how much vacuum will the 306 make ?

 

On my 383, it pulls about 13.5 inches of vacuum at a warm 900 rpm idle. It will probably pull less than that if you are still running a 350.

 

11hg on my 358.

-- Joe

 

If you want a very aggressive idle and peak HP go with the 306. But, if you want overall driveabilty and still a strong cam get the 503. This is especially true with a stock engine and an auto trans.

 

Thats how a vette should sound. Very nice.

 

Gator, there are many other great cams out there that can give you the sound you want and not be to big of a cam. Typically if you look for cams with LSA of 110 or lower you will get that 60s style lope. You might want to call one of these H/C places like LE or AI . They will be able to help you find a cam. Listen to my cam in signature, its similar to hot cam with a 110 lsa but it sound badass.

 

Notice that the 383 guys are saying the 306 is tame while the non-stroker guys talk about surge and one even talks about going back to the 503?

That's because the bigger displacement makes the cam seem smaller/milder.

With a stock LT1 you'd probably like the 503 better. If you have good heads, LTs, better exhaust, gears and a stall the 306 may be the better choice.

Mike

 

I have 3.73 gears and am going to install a 2500-3000 stall and long tubes. I already have magnaflows and an X pipe. decisions decisions.
I really like the sound of te 306 and have seen dyno results of 355 rwhp with just the cam and bolt ons. to me that is impressive. I just dont want to go to big and have driveability problems. if the idle is rough thats ok I just dont want it stalling. thanks for the input

 

Well if you choose a 503 I see them on ebay once and a while. If you choose a 306 mine will be for sale shortly.

-- Joe

 

how soon and how many miles on it? pm me

 

300 miles. heh

I dunno. I kinda wanted to drive the car until the end of sept/ or mid october..

I need smaller injectors first. I need to find someone that will trade me some 30# for my 36's. My 36s just idle ok with the cc-306 cam, I imagine with the 503 it will be soo fat it will foul.

-- Joe

 

From my own personal experience, I initially had 365 hp/368 ft-lbs to the wheels on my 10:1 compression, iron head 383 with the CC503 cam. Back then, the Miniram was unported. A bit of tweaking and tuning, I was able to attain 372 hp at 5600 rpms / 378 ft-lbs at 4000 rpms to the wheels. The motor also pulled about 15" of vacuum at an 850 rpm idle. So it was a nice street motor with an almost factory like idle, but the goal in mind was focusing more on slightly more top end power.

Now over to the CC306 cam, I initially had 382 hp/378 ft-lbs, same setup, just with that cam swap. Power peaked about a 900-1000 rpms higher than the old cam.

After some more tuning and also some head work as well as port matching the Miniram to the heads, I've made 397 rwhp at about 6500 rpms and a flat 380ish ft-lbs from about 3500-5500 rpms. Oh and I LOVE the way the cam sounds at idle! With an open exhaust, it sounds like a cammed big block!

Since me and a friend do the work, it was nice to know that there is about a 20 to 30 hp difference between the cams. With the CC306, you have about an extra usable 1000 rpms on the top revs. So far, this cam is 100% perfect for a street cat when it is used in a 383. I read all the time about people hating on the CC306 cam for a daily driver because they probably have limited access to tuning as well as not having the cubic inches for it.