i have a 87 iroc with a 305 tpi auto in it. It has flowmaster exhaust, k&n air filters, adjustable fuel regulator and other minor mods. I want a cam that will add power in low and mid range with a rougher idle, but yet drivable. What cam do you recomend that i put in the 305, i would like to use the same cam in a 350 that im building next year. Do the cams need to be made for computer controled engines, i know some say not for computer controlled. Let me know what you think would be good for my car.

 

Call comp cams help line.

 

A cam that will give you better low-mid range will not make the idle rougher. A cam that improves top end power at the expense of low speed torque will do that.

If the car is computer controlled stick with a cam recommended for it. Otherwise the computer won't know what to make of it, and reduced performance can result.

Ideally you want to run a bigger cam in a 350 than in a 305. Bigger engines will tolerate more cam without losing too much low speed torque and having a shaky idle. A cam that is radical for a 305 would just be a good performance cam in a 350, and would be tame in a 454.

 

I have the LT4 hot cam and it sounds like a regular car with loud exhaust. I tune the engine though, I get sad every time that I have nothing to change on the car. With sufficent tuning most cams on a FI car will sound mild. They usually are only rough if you can't tune well or it is a HUGE cam. Go with a ZZ4 cam in the 305, maybe a 204/210 cam. call the cam help lines.

 

On a fuel injected car you can tune the fuel and spark curves a lot better, and compensate for a bigger cam better, provided that you can reprogram the computer.

On a carbureted engine you can tune the same things, but not as precisely, and often you will need more fuel at low RPM, and this can cause you to fail emissions if the car needs to remain compliant.

A properly designed cam can also make the effects of increased flow not as bad as they can be. Most computer controlled cams use a wider lob seperation angle to reduce overlap. They will also use more lift, and less duration (relatively) to get the same flow, but again with less overlap. Overlap is the period where both valves are open. This bleeds off dynamic compression, which makes low end torque soggy, and it also can allow unburnt fuel into the exhaust and exhaust gasses back into the intake. This is what gives an engine with a "big" cam that lopey idle.

Any specific cam grind recommendation that I give you won't be nearly as good as one from a cam manufacturer. There's so much science in that bumpy stick, and those are the guys that do it for a living.

 

I plan on doing a cam swap this winter and looking at the comp Xtreme Energy XE256H cam 212/218 @.050 and .449" and .456" for intake and exhaust lift. It has a 112 lsa. I don't know if there is a roller version or not but I would asume so.

 

That'll be a decent performance cam. I've got a slightly larger Crane hydraulic roller in my truck now and I'm very happy with it. The engine has Edelbrock Performer RPMs, and Edelbrock Air Gap, an Edelbrock 750 carb, long tube headers, Crane roller rockers, and a complete MSD ignition system. It was built as a powerfull street engine, and with only 8.5:1 compression I run 87 octane and still make enough power to push a fullsize Chevy Blazer 4X4 faster than anyone ever thought possible.

 

why not just go with a stock 350 tpi cam same power curve as your 305's just a thought some poeple think that the 305 and the 350 share the same cams the 305 5 speeds got the 350 but not the autos then maybe ever some roller 1.6 roller rockers for some more lift hope i was some help

 

Be careful using 1.6 roller rockers on an engine with stock heads. I've seen them cause the pushrod to hit the head in the pushrod hole before. Typically you need to elongate the hole in the head, which would require you to remove the heads anyway.

With the heads off give them a nice port job, polish the chambers and use a performance cam meant for 1.5 rockers.

The 1.6s are a crutch for a small cam, and can be used for experimental purposes (e.g. to see if a bigger cam would make the car run faster in the 1/4, ect.). The problem with higher ratio rockers is that they impart significantly more stress to the valvetrain. If you look at the Hot Rod Engine Master's Challenge a lot of the entrants ran lower than stock ratio rockers (some as low as 1.3s !). This kept the valvetrain lighter, and reduced stress on the valvetrain, which was very important considering that these engines were built as dyno mules to be flogged relentlessly over and over again.

Any roller rocker is advantageous, even a stock ratio one, because it reduces the tremendous amount of friction in the valvetrain. The stock ball and fulcrum design is terrible in terms of friction. Even Smokey Yunick remarked on this when the small block debuted. He couldn't believe that it didn't have shaft mounted rocker arms.

Another point worth mentioning is that if you drive your car frequently and you do decide to use roller rockers go with the steel ones instead of the aluminum ones. The aluminum ones do not have the same kind of lifespan as the steel ones, and the steel ones are rebuildable too. The aluminum ones are cheaper, but ultimately you get what you pay for. If your car only sees a few thousand miles a year you will probably never wear out a set of aluminum rockers, but if you drive it daily you probably will.