Cam questions
Thread Starter
Safety Car
Joined: Jul 2002
Posts: 3,770
Likes: 3
From: St Louis MO
Cam questions
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:
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:
Burning Brakes
Joined: Aug 2000
Posts: 805
Likes: 0
From: Vasteras, Sweden
Re: Cam questions (Brettmc)
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]
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]
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Cam questions (Brettmc)
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.
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: Cam questions (Brettmc)
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.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Re: Cam questions (Brettmc)
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:
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:
Burning Brakes
Joined: Aug 2000
Posts: 805
Likes: 0
From: Vasteras, Sweden
Re: Cam questions (Brettmc)
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]
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]
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Team Owner
Joined: Feb 1999
Posts: 34,453
Likes: 665
From: Republic of Texas
Re: Cam questions (Brettmc)
Thanks. Even tho they cost more, it seems the rollers are the way to go.
Brett :thumbs:
Brett :thumbs: