narrowed down to 2 cam choices, convine me which to buy (solid or hyd)

Edbert · Apr 13, 2005

So this

.581/.596 lift

is the valve lift not the lobe lift?

DarkoStoj · Apr 13, 2005

Edbert said:
So this

is the valve lift not the lobe lift?

the origional specs I got were

249/258 dur @.50 and a lift of .540/.554 with 1.6 rockers 108 lsa

D.Hearne · Apr 14, 2005

DarkoStoj said:
the origional specs I got were

249/258 dur @.50 and a lift of .540/.554 with 1.6 rockers 108 lsa

It's not the lift specs that will cause contact there, it's the long duration.

PoliceInterceptor · Apr 14, 2005

DarkoStoj said:
the origional specs I got were

249/258 dur @.50 and a lift of .540/.554 with 1.6 rockers 108 lsa

So it is a 41008LUN "SOLID, Rough idle. Good for hot street car w/ 4-speed or short track car. Needs increased C.R." (3800-7000)

That cam is a HUGE jump from the two that you first asked about.

From the number it appears to be one of the old UltraDyne grinds. The story is (supposedly) that Lunati hired one of their grinders and he brought many of UltraDynes grinds along. The UltraDynes were strong cams. However, if you will look at the advertised numbers compared to the .050 numbers, there is something rotten in Denmark. You will find no other cams with such a short advertised and similar .050. I have to believe that the advertised numbers are incongruous with other makers advertised for some reason. If you calculate the ramp rate for one of those cams in DynoSim, it is higher than most solid rollers.

FWIW, that 3800 beginning power band is going to be a pain on the street IMHO.

My vote would go to Crower.

brianj5600 · Apr 14, 2005

Why the fascination with 7000 rpms? Why not slow the motor down and use bigger pills? You won't make enough cylinder pressure with flat tops to use a cam that will make 7000 rpms. I am suprized a cam company would recomend that much duration with that little compression. You could mill the heads, but then ptv will be a problem. IMO a cam that big will need a complete rethinking of the bottom end. Then you will deal with a soft bottom end 95% of the time for a little on top 5% of the time. I may just be getting old, but that does not sound like a good trade. Get a smaller cam and a bigger hose.

Edbert · Apr 14, 2005

I like your approach Brian.

There are a hundred different cam choices out there that will work. There's no way to say this one is right and that one is wrong, an engine has a personality and like people..."there's someone for everyone"...and you have to like whatever personality you build not me/us.

My approach to choosing a cam would be to first identify how you intend to use the car. For me it is a weekend cruiser, that i can drive to work once a month on a nice day. Something that can chit-it-and-git-it when I ask it to (low 12s was a must for me) but still get decent mileage with a light foot. Something that has enough vacuum for power brakes, run on pump gas, and can cruise the freeway below 2,500RPM. So I built a motor around the torque curve not hte peak hp numbers. My engine should have ~375 ft/lbs at 2,000RPM. it should be over 400 when the converter locks up, and remain at or above 400 ft/lbs all the way to redline. I had DSS Racing build/balance/blueprint my shortblock. I splurged on rods/studs/caps/girdle, my builder said the bottom end was good to 7,500RPM. Then I put a mild cam on it that will fall off at about 6,250, then I put a 6,000RPM limiter into the MSD box...LOL...basically I wont have to worry about my block until I supercharge it or run NOS

DarkoStoj · Apr 14, 2005

PoliceInterceptor said:
So it is a 41008LUN "SOLID, Rough idle. Good for hot street car w/ 4-speed or short track car. Needs increased C.R." (3800-7000)

That cam is a HUGE jump from the two that you first asked about.

From the number it appears to be one of the old UltraDyne grinds. The story is (supposedly) that Lunati hired one of their grinders and he brought many of UltraDynes grinds along. The UltraDynes were strong cams. However, if you will look at the advertised numbers compared to the .050 numbers, there is something rotten in Denmark. You will find no other cams with such a short advertised and similar .050. I have to believe that the advertised numbers are incongruous with other makers advertised for some reason. If you calculate the ramp rate for one of those cams in DynoSim, it is higher than most solid rollers.

FWIW, that 3800 beginning power band is going to be a pain on the street IMHO.

My vote would go to Crower.

well this is the first high hp motor i've ever built, so I really didn't know what durations are good for what when I made this post. Since then i've talked to many people and have tried to educate myself as much as possible. Basically what I want is a car that will hit 10sec in the 1/4, but will get a lot of street miles. I want that lumpy idle, and screaming rpm motor, and I don't think the lower torque #'s would bother me... considering I have nothing to compare it to, so any torque #'s I do get even if they are low will be amazing to me.

Edbert · Apr 14, 2005

DarkoStoj said:
Basically what I want is a car that will hit 10sec in the 1/4, but will get a lot of street miles.

10s eh, thats a lofty goal for an old unibody on leafs, not imposible at all but will take more than motor. What suspension mods are you planning?

How many miles are we talking here? Take her out once a day or twice a month, 1,000 per year or 10,000 per year? I know folks who drive 10 second cars on the street, but not any more than 2,000 miles a year, and when they do drive on the street that have to be on the gas pretty hard and are always at high RPM just to keep it running. Loud cars running 5,000RPM will attract a lot of unwanted attention even if you are at or under the speed limit.

If you intend to keep the street driving to a minimum I think you can make that work, but if you intend to drive it in public much at all you're not gonna be happy with the power curve. Forget cruising, carrying on a conversation and abandon any hopes of a sound system. What you are building is pretty much a racing engine.

PoliceInterceptor · Apr 14, 2005

10’s are a real lofty goal. That is super fast for anything approaching a "Street Car".

I am all for your decision to go with Lunati over Comp, but I think that particular Lunati is a huge mistake if you have any intention of putting lots of street miles on the car. I think you are going to be real disappointed in the performance unless you are looking to swap to a gear in the high 4's or low 5's (IE 4:56-5:12) range.

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