How big is too big of a cam?

streetstang67 said:

What are the limiting factors of cam size? Besides stall and piston to valve clearance, whats to stop me from putting some cam in with .7 lift and 300* duration in a relatively stock 289? Whats the biggest/best cam for a 289 with stock heads, performer intake, 600cfm carb....provided I get a stall to match it?

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Problems:

The ability of the intake to flow enough air and fuel to feed it (def)
The ability of the heads to flow enough air and fuel to feed it (def)
The ability of the heads to flow enough air to get the exhaust out (def)
The ability of the fuel pump to flow enough gas to feed it (maybe)
The ability for your starter to crank the motor when it floods and you need to restart it with 1/4 gallon of gas in one cylinder (maybe)

Losta limiting factors.

Heads/intake/carb/cam all need to be a matched combo for optimum performance.

If you put a .7 lift with 3 duration cam, you are running a very aggressive cam that won't make power for you until high RPMs, if you match with stock heads, crappy intake, and too small of a carb you get a dog. A lot of people do this and then piss and moan that they have all this 'stuff' on their car but run 15s at the track

You need to pick all your compoments to operate in the same general RPM range and flow similar CFMS...just like a 1050 CFM carb on a stock 289 headed motor, a huge cam on a stock headed motor is also wrong.

For what its worth, the performer is a nice intake for a mild build...but it pretty much dies at 4500 so there are not too many more aggressive cams out there that you will be able to run without swapping at the very least the intake.

What’s to stop you is the small intake, heads and gear. A big cam will typically want big RPM’s and your set-up isn’t ready for that. If you went to a Weiand Xcellerator intake, 3.50+ gears, and had your heads fitted for good valves and springs (or better heads), then a cam would make sense. A big cam in your set-up would be a big disappointment unless you upgraded.

As a point of reference I ran a 230/235 .510/.515 107 LSA hydraulic cam in a 302 with a 600 Holley, an Edelbrock RPM and 3.89 gears and it was very well matched. And that was with stock heads (new valves and springs). That is starting to be a cam on the big side for a hydraulic. It might have been a little too grumpy for some peoples taste, but I liked it. But to put that cam in your current set-up might not work too well; it would probably underperform. Like DodgeStang said, you have to match parts to make them work.

streetstang67 said:

What about roller cams? Would that be worth the extra money in my application?

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You'll have to retrofit roller lifters in the 289. You'll either have to machine the block, and/or purchase retrofit roller lifters and they aint cheap. In the long run, it is less expensive to start with a roller motor. I'm not saying it can't be done, it will just cost you one way or the other.

I just installed a comp mechanical lifter cam thats 236/236 duration @ .50 .528/.528 lift on a 108 lobe. So far it runs great and seems to make more power then the old isky I had. My setup is very similar to yours, edelbrock 600 carb , performer manifold, stock heads and springs, short tube headers, and stock gears. I cant wait until I can drive it more and really get on it! I hope this helps.

hey hummer 784 are you running that cam with a stock bottom end

A cam's ABDC spec will affect the engine's Dynamic Compression
Dynamic CR

Dynamic CR calculator

A cam is "too big" when it hurts power, drivability, and possibly hardware.

You have a stock longblock 289 with a Performer intake, vacuum secondary 600 carb, and headers. On top of that, a C4 behind it with I assume a stock stall converter. All of those are going to limit your cam selection to something around .480-.520 lift with a relatively wide LSA and relatively short duration to keep the vacuum acceptable. The heads probably run out of flow around .500 anyway. A roller cam will allow a more aggressive profile without hurting drivability, but there again, the rest of the engine and driveline is the limiting factor.

I have learned that the cam should probably be the absolutely last thing purchased. The reality is that it is often the first thing purchase because a lumpy cam is cheap and makes the engine sound good, even if it wrecks the good traits of the mild combination it went into.

streetstang67 said:

What are the limiting factors of cam size? Besides stall and piston to valve clearance, whats to stop me from putting some cam in with .7 lift and 300* duration in a relatively stock 289? Whats the biggest/best cam for a 289 with stock heads, performer intake, 600cfm carb....provided I get a stall to match it?

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For one thing, you'll never get a .700 lift cam to function due to the limitations os the stock valve train and heads. Massive machinework would have to be done to accomodate that much lift without the springs binding. Once you did all this, you could have had premium aftermarket heads for less money.

dodgestang said:

Heads/intake/carb/cam all need to be a matched combo for optimum performance.

If you put a .7 lift with 3 duration cam, you are running a very aggressive cam that won't make power for you until high RPMs, if you match with stock heads, crappy intake, and too small of a carb you get a dog. A lot of people do this and then piss and moan that they have all this 'stuff' on their car but run 15s at the track

You need to pick all your compoments to operate in the same general RPM range and flow similar CFMS...just like a 1050 CFM carb on a stock 289 headed motor, a huge cam on a stock headed motor is also wrong.

For what its worth, the performer is a nice intake for a mild build...but it pretty much dies at 4500 so there are not too many more aggressive cams out there that you will be able to run without swapping at the very least the intake.

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Not all this is absolutely neccessary for good results. There are lots of parts combos that wil make HP without being all "matched components" In some instances a too small carb gets you excellant bottom end. And in some instances a 1050 cfm Dominator can be made to work on a 289. And there are lots of more "agressive than stock" cams that will work with the stock intakes. In short, you can do mods in steps to build HP and learning experience and not have to go "all out" and do everything at once & at the same time emptying the bank.