bayer-z28

iTrader: (14)

The 918's are apparently rated good to .600 lift. Are these ratings cam or valve lift? The reason I ask is a mild cam would produce more than .600, therefor making the beehives no good on a bigger or mid cam. -Explain...


Second Question... How does LSA relate to power gains? I know what it is. I have done my homework on cams, but I am wondering if there would be any difference in power when going from a 112 to a 114 LSA or vice versa. NA motor, btw. -I'm thinking no difference besides idle

hammertime

iTrader: (1)

The springs are rated for valve lift. .600 lobe lift would be over an inch at the valve.

Answers to both questions are going to depend on the cam and what your design criteria are. The 918's are good up to 234 duration in the XE-R series, and cover the whole XE family of lobes.

Tighter LSA's tend to concentrate the power in a tighter range, which is actually not a bad thing since you have an M6. A wider LSA would come on a little earlier, and perhaps carry the power a little higher, but would not peak as high (hp, not rpm) as the tighter LSA.

For cam only, a tighter LSA with mild durations give sharp low end throttle response and great torque due to the tighter LSA. Excessive duration can give you to much overlap to have good manners in a daily driver. Larger cams with wider LSA are a compromise, and tend to close the intake valve rather late, dropping Dynamic Compression in an attempt to maintain acceptable idle quality.

If you are doing heads and cam, you can get away with a wider LSA and stretch your powerband some by milling the heads and optimising the Dynamic Compression.

Really, it all comes down to what you want your cam to do. Daily driver, weekend warrior, emissions friendly, nasty lope, great power with stock heads, max effort track car - all require different cams.

bayer-z28

iTrader: (14)

Ok.. I get ya... I am going for a 228 TSP cam.. It's streetable, but I want the 112 lope. But not too aggressive overall cam, tho. My buddy just installed the MS4 and I think it's way to aggressive for a DD. I understand what you mean by the LSA difference. I'd have to read it over a couple times to really let it sink in.

I like the TSP 228 .588 112. I was thinking about maybe an exhaust biased cam, but I can't make up my mind. The 224R 228R TSP cams have a wide (1600-6800) powerband I am also thinking about going w/ a turbo when I get the money. So I may have to switch to a wider 114 LSA and an exh biased cam anyway. Was thinking about the 225/225 .581 .581 114 for a turbo, but I want a lopier idle. I suppose i can't rally have it w/ a turbo, tho.

Come to think of it, I swear I remember LS1 Speed carrying a 232/234 .581 .588 cam for turbo/FI. But ti's not listed in their selection now under Turbo/Blower.

cws T/A

iTrader: (3)

918 vs Duals .. single breaks you drop a valve , dual breaks the inner spring may save your engine

bayer-z28

iTrader: (14)

^ Huh.. How so?? If the spring breaks regardless, if the retainers are still intact, the valve wouldn't fall... The stem is considerably thinner then the ID of the inner spring.. The 918's are supposed to control valve float better up to some insane RPM #'s.. Lie 9k RPM or something like that... I read about it somewhere, but I can't find it for the life of me.

cws T/A

iTrader: (3)

Your right , I wasn't thinking good at 2;am

bayer-z28 cws T/A

bayer-z28

iTrader: (14)

^... ... nah.. it's kewl... I was looking to pick up some new info.. I never heard of duals offering PTV spring breakage protection.

hammertime

iTrader: (1)

Yes, dual springs do offer some additional insurance against valve drop. If you are relying on the retainer to keep the valve off the piston, the valve is going way in the chamber before that stops it.

Also, no way a 918 spring is going to allow you to spin 9,000 rpms. Hell I don't know that 921's would have the spring pressure to do that. The valvetrain is one of the biggest limiting factors to spinning an engine at excessive speeds, and there is no way a budget spring will contend with that.