My Cam and Your Cam
 

I have a SB Ford with 11:1 compression, racing pistons, crank, oil, and a 35-518-8 comp cam. The cam produces a fairly nice torque and hp curve, and a somewhat nice idle if I take the idle rpms down to 600-700. I would prefer to idle the engine around 950-1050 RPM but the cam looses most of it's great sound and rumble - smooths out quite a bit. Perhaps I want something a bit more nasty sounding... not sure if that is the right word, but I think it can be interpreted.


I'm hoping some of the more experienced engine builders could give me their input on this cam, and the possibility of putting a more aggressive or bigger cam in this engine. Is this a large cam to start with? Average?

Does changing the cam require removing the engine? What else would need to be done once a cam is changed? Should I take it to an engine shop or try to do this myself? Thanks for all your help?

Can I ask WHY??
 

Redeye Idling a motor down in the 650-700 rpm range is not a go thing to start with. OIling of the motor is border line. A motor will internally leak pressure off in the 15-30 psi range. The closest parts getting the pressure you read on your dash gauge to the farest point of the motor getting maybe just enough to float the bearings. IF the oil has oiling modifications this could be even worst. Most motors get too much oil to the heads and rockers and stavre out the bottom ends. With modes we keep the oil down on the rotating assembly more. This helps alot. Other note is solid roller lifters or just solids don't like to be ilded at all. Hydro roller will last 200 k miles with good maintainance, solid lifter or roller will last from 200 miles to 20k miles and then maybe need rebuild or checking. Alot depends on valve spring pressures and RPM range.
If you want the car louder, change the mufflers to spirals or straight pipes. Overlap of the camshafts are partially what makes the nasty noise. I think thumper cams would make what you want.
With radiator out of car, camshaft cam be done in the car with loose motor mounts to move it around. Side note, For the time it takes to remove and install the motor and do this on an engine stand will save your back 10 fold. Prelube everything and run motor for 15 minutes at 2,000 rpms for brake in, no exceptions, change oil and filter and look for any metal partials in filter. You should be goto go. Rick L.

That's about where you want to be with a 331. When you start playing with durations, you move the powerband either higher or lower. You can add more duration, but it may make the engine softer on the bottom than what you want, and may actually put the top end up in a spot where you get into valve float issues.

Here's what I would recommend....

On a hydraulic roller, no real reason to keep the idle up so high. If it idles at 850-900 without issue, then let it idle there.

It it labors to idle it that low, and it sounds too smooth for your preference when you idle it up, then you have the option of going with a custom cam. This would keep the same duration, but we could tighten up the LSA to make it sound "healthy". This would probably add a little broader torque curve to your engine as well.

Hey Brent, had an idea
 

Bylins Brent Had a brain fart, How about either leaving a spark plug wire off for that nasty idle or swapping 2 wires on cylinders to get that nasty fire out the side pipe deal. Have done both in the early years and scared the hell out of friends. :eek::rolleyes::LOL::LOL::LOL:

REDEYE, only kidding with Brent.

Or pull the choke shut when you're rolling through the parking lot....;)

Open up the side pipes so you hear every cylinder firing.

If you want a nasty cam, build a Chevelle. Cobras are sport racing cars.

Yep..cruisers of old would retard the timing ....

I have a custom grind cam, sounds nasty but it does fine around town and cruises down the highway at 1400 rpm with no trouble. I would never change this cam, I love it.

I think with 11:1 compression, 240 - 250 @ .050 would be more appropriate.

When I was 16, driving a serious looking 55 Chevy hardtop with a stock 6 cylinder under the hood, I'd pull off a vacuum hose before idling through the local McDonald's parking lot. As long as I didn't rev it up, most fellow 16 year olds couldn't tell it was all show and no go.

I am running 11:1 and the duration on my cam is between 240 and 250 @ 0.050" I was asked that I not share the specs on this cam so that is as close as I can tell you to the actual specs. I can tell you that this thing is a beast. It is a Dart block 363 so not to far off from what you are building. Gordon estimated with my parts combination 525 - 530 hp @ 6500 rpm and somewhere around 475 on torque. Runs great around town and has more power than you could ever use and still gets 17 mpg, what more could you want.

Any chance your cam builder would like to sell me one as well?

I suppose too, i would love to hear what it sounds like.