Brettmc

Trying to get an idea of the differences in cam behavior in small blocks and big blocks. I used to know a little about small blocks back in the day and need a reference point for big blocks. If a 480" lift 230* duration @ .050" cam was put into a sb and a bb, what would the differences be in idle, vacuum and power characteristics between the 2? I had the above cam in a 406 and it idled rough, was sluggish down low but had a strong top end. Surely the same cam pattern will act differently in a bb.

Also, in looking at big block cams from Comp, I noticed that some hyd flat tappets and hyd rollers had somewhat similar duration figures but the rollers had waaaay more lift. How does this affect the power characteristics of the roller?

Brett :thumbs:

Lasse

The 230@.050 cam is pretty mild in a BB, but a good choice for power-street use.

I have Crane hydraulic roller 226/234@.050, 288/296@adv. and .587/.610 lift. The idle is strong with 14 inHG @ 700 rpm. I can drive down to 30 mph in the fourth gear ~1400 rpm (3.55 rearend), but that's my limit. The torque curve seems to be very flat from 2500 rpm and up. I spinn the rear tires (295 wide) without using any technique, in second gear from 2500 rpm, by just accelerate smooth up to 2500 rpm and then open it up. No clutch involved!

I can strongly recommend that cam, if you wan't a 'perfect' cam without any misbehavior such as weak vacuum and bottomend!

Click on this link if you wanna hear it:
http://w1.212.telia.com/%7Eu21203717...raylinks/1.wav
I shout at 95 mph.




[Modified by Lasse, 11:11 AM 9/28/2003]

Fevre

The higher and faster the lift the more air flow, that is why a roller cam with the same duration and lift as a flat tappet cam makes more power, the valves open faster and stay at peak lift longer allowing more air flow. Since a roller cam can use steeper profiles they tend to use higher lifts then a comparable flat tappet cam.

Jvette73

Generally speaking, the more cubic inches of displacement, the milder the characteristics of the the same cam would be. So a cam with a certain grind that would seem moderately radical in a 350SB, with a similar grind would seem less radical, and have less negitive effects on bottom end when used in a 454.

Ganey

As the displacement significantly increases, the same cam acts milder.
So in your example:
While a 280H 230/230 .480/.480 110 is considered bad by some in a 350, it's mild in a 454 & since the rocker ratio of the BB is 1.7 the lift & effective duration is more. The aftermarket roller cams put more area under the curve.
When there is a cam topic & someone says what that cam is like in a significantly different C.I. engine, it's not relevant though it can be interpreted by some to what the guy wants.

That's why some say never too much cam, just not enough motor.

:cool:

Brettmc

Sounds good, L. Not real lopey at idle either. What did you have to do to get the roller lifters to work in your block?

Brett :thumbs:

Lasse

You can leave the block as it is.

You will need shorter pushrods and cam buttom (to prevent the cam walk forward) and of course cam, suitable valvesprings and retro fit roller lifters.

This is my engine setup: http://w1.212.telia.com/%7Eu21203717...motordelar.xls :thumbs:

I picked some of it from this page: http://www.cranecams.com/motorsports...ler/139731.htm


[Modified by Lasse, 9:48 PM 9/29/2003]

Brettmc

Thanks. Even tho they cost more, it seems the rollers are the way to go.

Brett :thumbs:

Corey_68

I agree they allow to run more duration with more streetability. Having said that, I couldn't justify spending the $1,000 for a complete roller set up (cam, rockers, and lifters). :nonod: