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  #211 (permalink)  
Old 07-15-2019, 08:17 AM
55 Tony's Avatar
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Not that I don't trust the help on this group, but I was asking the same questions about this heads performance on another group also. More advice can be better, or just more confusing, but I'm grasping at straws.


It has been recommended that I get a cam with a longer duration. Also said was a cam with an earlier opening and more important closing of the valves. Any thoughts on that? The current cam is a lot more mild than I had hoped, so I don't mind if a new one is a little less streetable. Don't get me wrong, I'd still like to drive it on the street more than the track, but I don't mind if it doesn't purr like a kitten at 750rpm like it does now. Also with a cam change to a longer duration, if you could explain to me in what ways will it become less streetable? Thanks so much with this mile long thread!
For you convenience, here is a link again to my current cam specs. http://www.compcams.com/Company/CC/c...?csid=438&sb=2


Oh, and Ericnova, at this point I really don't want to pull the motor, so decking the block is off the table for now. Is just milling the head getting maybe .75 point gain worth the hassle?

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  #212 (permalink)  
Old 07-15-2019, 09:17 AM
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Going to be hard to get earlier opening AND earlier closing points for the intake valve while at the same time trying to add duration.....something has to give somewhere.

I would have wanted a bigger cam from the get go, the smallest I would have considered would have been something at least 8 @.050" bigger than the factory LS-6 solid lifter stick at 242 @.050"....probably something more like the L88 solid at 264/269 @.050".
I'm far from convinced hydraulic roller is a successful way to go with a BBC, seems like there are just too many complaints of either lack of power or lack of RPM capability.

I've put 248/254 @.050 solid in 406 and 383 SBC's and they are mild enough your Mom could drive it, while still making good power..

If it was me, since you are close to 3/4 of the way there while doing a cam swap, valvetrain is all loose, is pull the heads for a mill job at the same time.
Id look to increase the duration while tightening the lobe separation down to 106, trying to add no more than a couple degrees to the intake closing. This will add a bunch to the intake opening point.

"Less streetable"....lower vacuum for power brakes, higher idle speed so it drags harder on the brakes at a stoplight unless the stall rpm is higher, rough idle, poorer gas mileage, stickshift cars will need more downshifts as motor won't like being lugged down to low in rpm without chugging, same with an automatic but to a much lesser extent, might have to stay in 2nd at city suburb speeds.
All things that don't matter if you're really after performance.....you like the 1100 rpm choppy rough "fender shaker" idle, you have no problem tossing the shifter into neutral at every stop light or while creeping forward in a traffic jam or event entry line, you don't need power assist on the brakes

Mentality: Are you Bob Falfa/John Milner, or are you Steve Bolander. (for those of you who get an "American Graffiti" reference )

The only hydro roller that caught my eye in Comp cams list is Cam Part #11-870-11, grind # 3130NHR-08, in Drag Race Hydraulic roller section. I'd link it but their web site is acting really screwy today, can't get to several pages. 260/270 @.050" duration and .670" ish lift, 108 LSA Listed as 3600-6800 rpm bracket cam for 396, so rpm range will come down 400 rpm or so in a 454.
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  #213 (permalink)  
Old 07-15-2019, 01:23 PM
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Holy cr*p that's a huge jump. Did a search for that cam and Jegs lists the specs. I believe that's a bit more than what I want. As for the American Graffiti reference, I think I saw that in the movie theater and not since, and I sure don't remember the names. I know I should since my ride is a 55 chevy.
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  #214 (permalink)  
Old 07-15-2019, 04:17 PM
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Quote:
Originally Posted by 55 Tony View Post
Holy cr*p that's a huge jump. Did a search for that cam and Jegs lists the specs. I believe that's a bit more than what I want. As for the American Graffiti reference, I think I saw that in the movie theater and not since, and I sure don't remember the names. I know I should since my ride is a 55 chevy.
I figured owning a '55 you'd get the movie reference
"Bob Falfa" was the driver of the black '55 Chevy, character played by Harrison Ford. "John Milner" was the driver of the yellow '32 Deuce coupe, character played by Paul LeMat. "Steve Bolander" drove the white w/red striping '58 Bel Air cruiser, character played by Ron Howard(Opie on "Andy Griffith", Richie on "Happy Days").

Anyways...Cam I referred to has near the same power band as what you currently have, as you've said before you don't want to turn this build higher rpm-wise. Just the 8 added intake duration @.050" and tighter lobe separation to get an earlier opening intake valve without drastically changing the intake closing point(nearly identical advertised intake durations).

You may think is seems ultra radical, but you have to dissect the numbers to get the whole picture.
It is 1 LESS total seat-to-seat intake duration, combined with 2 closer lobe separation actually closes the intake valve 2.5 SOONER than your current cam....so it is going to trap more mixture(higher DCR). This means the additional duration is all on the exhaust side, getting the exhaust overlap draw on the intake charge started earlier by about 10. It is also a much more aggressive lobe profile, as it has 16 more duration at .200" lobe lift....which means a lot more "area under the lift curve", and that is a significant difference.
This is what the Lobe Master catalog description of the intake lobe is: "The QXI Series lobe profiles are designed to provide the highest available valve lift for modern cylinder head ports, along with excellent stability and the broadest possible power range in hydraulic roller applications. Designed for both street and racing use".

It's a match to the other board's cam choice advice. Toss this info to your other forum board and see what they think.

Idle will be a more radical lope, but power range is the same rpm window. Should just create a power increase across the entire rpm band. Same compression ratio suggested, same rear gearing, and BBC's always like more lift.
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