MILD THUNDER

iTrader: (3)

yes, lol. And probably a good time to discuss the effect of lobe lift vs duration, acceleration of the lifter, .006, .050, .200 duration numbers, and how one lobe can beat the snot out of a valve train and need big spring pressure, vs another lobe, that will be easy on the valvetrain, and not need excessive spring pressure. Like for example, a .410 lobe vs a .370 lobe, on a 240* deg cam lobe, and what the larger lobe does to lifter motion. .

I used to think what made a cam choice the best, was its dyno numbers. I now look for a cam, that won't beat my valvetrain up in a short time, just to make an extra 20hp. .

SB

iTrader: (1)

Hard to determine that way..but we all have our thoughts based off those numbers when given.

Some companies inverse ramps are kept in control...but how ? We can't tell off a sheet of paper right ?

Also, how well lobes are machined can be a big factor.

Valvetrain weight, rocker arm ratio vs lobe design, etc,etc,etc

SB

iTrader: (1)

How would you feel with a .356 lobe with only 218° at .050", 268° at .006" and 143° at .200" ? Yes, it goes 6k or so a good amt.

MILD THUNDER

iTrader: (3)

Good points. I dont think there is much getting around the negative aspect, of increasing lobe lift, without increasing duration. At some point, things become an issue.

There must be a reason, competition cams, crane cams, and many others, do not make short duration, high lift, hydraulic roller, Marine, or endurance profiles. When looking thru any of their catalogs, anything "marine", or "endurance racing", with durations of say, 230-245ish range, .370 is about the max lobe lift they will run, including mercury marine.

I've seen alot of custom cams lately, sporting those kinds of durations, but with .400+ lobes, and .680+lift. Crane, comp, and many guys (including myself), have ran those .370 short duration sticks for years, with 165/450ish spring pressures. But the guys with the big lobes, are running 225/600 spring pressures. I wonder why that is. Probably, because if they tried less pressure, the lifter lofts, valve train fails in short order.

I like new stuff, but sometimes going with whats been proven, works better! I have yet to see a guy running these .400 lobe deals, come back after 300 hours, and say how they've never had a valve cover off of it. It very well could happen, and if so, maybe then I'd try it.

SB

iTrader: (1)

Back in the 90's, lift at/near .600" w 1.7 rockers was extreme for bbc in cars for everything but solid rollers. Even when talking near 250-260 at ,050"

We've come a long way...haven't we ?

MILD THUNDER

iTrader: (3)

We talking flat tappet?

SB

iTrader: (1)

Solid FT and HR

MILD THUNDER

iTrader: (3)

I would say that is towards the aggressive side of things as far as valvetrain/lifter acceleration. Certainly not outlandish, but not exactly a stock 502 mag cam either that might go 1000 hours without taking a valve cover off lol

SB

iTrader: (1)

BBC blocks notoriously have lifter bores not indexed correctly. That poor roller wheel and what that does to stability.

SB

iTrader: (1)

So, .605" , 218 at .050"lobe is milder than say .650" or so 240 at .050" lobe ? How can you tell ?