Another Cam Selection Question!

[drofdar]

We're putting together a 283 for my girlfriends T-Bucket Bracket Car. I've heard it's easy to over cam the smaller cube 283, and wanted to check with the SBC guru's here. Comp Cam recommends their 12-238-2: 218/224@.050 Lift .462/.469 110LSA.
Car has T350 trans - no trans brake. She holds foot brake, and mashes throttle on green to flash convertor, which is stock. Leaves it in drive, for consistency. Big Hoosier tires 4:56 gear. Looking for low end torque and something that pulls up to 5500rpm. Suggestions welcomed!

[jerry clayton]

how about a stock cam from a 90s vortec or LT except you will need a electric fuel pump

[Scooting]

Jerry, help me to understand, why would a stock vortec cam require an electric fuel pump on a 283 with a carb? Not being a smart a**, just wondering why?

[t-top havoc]

There is no cam eccentric for the manual fuel pump

[drofdar]

Car does have electric fuel pump/water pump. Not being a cam scientist, I wonder why, or what the specs are that make the 90's vortec or LT cam useful for this application? Never heard of this swap before.

[jerry clayton]

you have a 283 sbc

a cam from a 350 will be bigger--------

The vortec/LT cams are hyd roller cams, and they run smooth, bottom end torque and will rev up pass 6000 without any flat spots--------

good milage, smokes tires

[rspears]

.....a cam from a 350 will be bigger--------

Jerry,
When you say "...will be bigger..." that means it will have more lift, plus longer duration on both intake and exhaust to feed the greater volume flow of the 350 compared to the 283, right?

[jerry clayton]

well sort of-maybe------------

A cam that is pretty radical for a 283 would be pretty mild in a 600 inch motor---------

and going the other way, a cam from a 350 would be more robust in a 200 incher-------

his car----foot brake, stock converter, big tire, 456 gear---running in drive---------

and he probably can find one for free so will just have to do lifters outta pocket

[rspears]

well sort of-maybe------------

A cam that is pretty radical for a 283 would be pretty mild in a 600 inch motor---------

and going the other way, a cam from a 350 would be more robust in a 200 incher-------

his car----foot brake, stock converter, big tire, 456 gear---running in drive---------

and he probably can find one for free so will just have to do lifters outta pocket

Just trying to clarify, Jerry, so that someone who doesn't understand cam details knows what "bigger" means in normal terms seen on a cam card.

[NTFDAY]

Roger, the 30/30 I have was pretty radical in the 265, but rather tame in the 400 and it busted a valve spring in the 400 somewhere between 6 and 7 grand.

[rspears]

Roger, the 30/30 I have was pretty radical in the 265, but rather tame in the 400 and it busted a valve spring in the 400 somewhere between 6 and 7 grand.

Ken,
I understand what you're saying. The only things that one can change in a cam are the lift, duration, overlap and advance/retard relative to TDC, right? So doesn't it infer that a "bigger" cam for a specific engine, say the 283, is going to have more duration, more overlap, and perhaps more lift than the "milder" cam, or am I overlooking something basic? Of course the bigger engine or performance heads for the 283 will have bigger valves to breath better, but I'm just trying to clarify the understanding of the cam numbers. This is not a big deal, but sometimes we throw around terms that are second nature, not thinking that the guy asking the question may not be so well versed in how to spec a part, like a cam.

[NTFDAY]

Since my understanding of cam numbers is not the greatest I will leave that up to someone who knows how to explain it. Hopefully Jerry, Pat, or tech will come along and give a better explanation than I ever could. I just know how that particular cam reacted in two different engines, but trying to explain it is definitely out of my pay grade.

[jerry clayton]

OKKKKKKKKKKK
there is a difference between flat tappet and rollers in that on a flat tappet setup, the cam to lifter contact is a line tangent to the lobe/tappet and the line moves across the face of the lifter---- on a roller set up that is a constantly changing contact point/angle as you have two curved objects getting friendly---------
On a flat tappet cam you are limited by the edge of the lifter reaching a point where it would hook the edge into the cam(sorta like a garden hoe into the dirt as you scraped it across the surface------

On a roller setup that is a constantly changing line angle with no hook and it allows a much faster opening rate which allows the valves to open much faster to there max and with the radius of the lifter roller allows it to stay near max opening much longer where a flat will go up there and slow down stop and then start lowering the valve sooner

These are factors why the cam companies use .050 from base circle to be a measuring point for the cam cards numbers
A roller cam can open the valve so fast that we have to watch for tappet flying off the cam nose as the deceleration near full open occurs while on a flat its necessary to run really high spring seat preasures just to keep the valve from bouncing----------

[rspears]

OKKKKKKKKKKK
there is a difference between flat tappet and rollers in that on a flat tappet setup, the cam to lifter contact is a line tangent to the lobe/tappet and the line moves across the face of the lifter---- on a roller set up that is a constantly changing contact point/angle as you have two curved objects getting friendly---------
On a flat tappet cam you are limited by the edge of the lifter reaching a point where it would hook the edge into the cam(sorta like a garden hoe into the dirt as you scraped it across the surface------

On a roller setup that is a constantly changing line angle with no hook and it allows a much faster opening rate which allows the valves to open much faster to there max and with the radius of the lifter roller allows it to stay near max opening much longer where a flat will go up there and slow down stop and then start lowering the valve sooner

These are factors why the cam companies use .050 from base circle to be a measuring point for the cam cards numbers
A roller cam can open the valve so fast that we have to watch for tappet flying off the cam nose as the deceleration near full open occurs while on a flat its necessary to run really high spring seat preasures just to keep the valve from bouncing----------

All very good information, Jerry, but rather than getting into the differences between flat and roller cam profiles I would think it would be more informative to stick with the differences between mild and wild only on roller cams, since we all know that today's oils make the use of a flat tappet cam questionable at best. That said, perhaps what you were saying back in post #6 is that the new vortech/LT cam is "bigger" compared to the old flat tappet cam that was in the 283 before, apples & oranges because the profiles are so much different as you explained above, and like you point out, switching over to the roller requires higher spring pressures to keep things together.

I thought it was a simple question, trying to give drofdar a better understanding about what was being stated, but I guess it was not simple. Sorry for hi-jacking the thread, drofdar, I'm done.