Ive always used solid cams in my 327 & 350 buildups but now I am helping a friend build a lower reving 383. With approx 6000rpm limit, is there much to be gained by using a soild flat tappet cam over a hydraulic. He doesn't mind adjusting lifters.

I was considering using the old LT1 cam as its combination of long duration and wide lobe centre would do a good job dropping the dcr on a 10.8/1 iron headed 383 but let it rev enough to take advantage of his existing 1&3/4 long tube headers. The wide lobe centre would give it a reasonable idle.

Comments?

 

The LT-1 cam is an excellent choice for a street engine, but since you don't need the additional rev range, the L-46/82 cam would work very well and eliminate the valve clearance maintenance. Specs are 224/224 duration at .050" , 114/114 centerlines, 114 LSA.

If your heads flow at least as well as a nicely massaged set of 461s, it should make peak power at about 5500 and the valvetrain is good to 6000.

Duke

 

He will be using my old heads, a set of professionally port set of 461's!!!

My info on the LT1 cam is 242/254, .459/.458, 116 lobe sep angle. Is this correct. Worth a set of 1.6 rockers? I have good springs.

 

If you don't mind going hydraulic, the Comp XE 274 makes excellent power on 383's. I believe Crane also makes an updated (solid)LT1 cam. Both of these grinds have plenty of technology built into the lobes giving much more power under the curve and are still very streetable. .

 

Both OE an aftermarket mechanical lifter cam duration at .050" inch includes the clearance ramps, and this data IS NOT comparable to hydraulic lifter cams. Mechanical lifter duration at .050" ABOVE THE TOPS OF THE CLEARANCE RAMPS must be used for comparison, but about the only way to determine this is to look at the lobe design data and determine the height of the cleanance ramps.

I have done this for the LT-1 cam. The clearance ramp heights are .012"/.017", so the lifter rise at .050" rise above the top of the ramps is .062"/.067" above the tops of the base circle.

Thus, the duration at .050" is 231/239 respectively and the total lobe height (including clearance ramps) is .306"/.323" The points of maximum lift and separation angle thereof, are 110/122, 116, but due to lobe asymmetry the actual "centerlines" using the .050" data are 110.5/121.5 and are offset more if you compute them from SAE J604d duration (.006 valve rise) or lash point duration.

The OE rockers begin at about 1.37:1 at the lash point and attain 1.44:1 at maximum lift. Aftermarket higher ratio rockers are not worth much. I prefer the OE rockers and you should use the '67 up OE valvespring ("068"). OE mechanical lifter cams have soft action and use the same springs at all other SBs. You don't need or even want "big" springs.

You compute the static cold lash adjustment by multiplying the lash point rocker ratio times ramp height. Total actual lift is computed by multiplying the lobe height minus clearance ramp height by the maximum attained rocker ratio at peak lift.

Duke

 

Heres's a nice Crower solid that would be great in that motor...

Crower PN 00321 Mech

 

how do u guys pick a cam w/out knowing the trans or rear? or the use of the car?

 

Also... Hydraulic lifters are much improved over the lifters of the 60's. Lots of guys running hydraulic on motors turning 7,000 RPMs. Why would anyone want to go with solids when hydraulic is a viable option?

 

You're right. That Crower 321 will need a manual trans & 3.70's.

 

Do you have this cam in your engine? I'd be interested to hear your comments and experiences.

Thanks in advance!

tapio

 

Good point. I recommended the 274 as is is a good all around cam that will pull hard to 6000 rpm in a stroker.

 

I'm a fan of solids & I run them in both of my toys. But with a target of 6000 RPMs I just don't see the need for them. There are a bunch of good hydraulic grinds that would work just fine for your friend w/o having to deal with valve adjusments. As Matt suggested, if you post vehicle weight, gearing, intended usage, etc. you'll get better opinions on what would work best.

For what it's worth I used to run a mild Crower hydraulic flat tappet in the Vette that took me to low 12's in the 1/4 mile while trapping at 112+ MPH. The specs wouldn't indicate this but on the dyno the HP peaked almost exactly at 6000 RPMs. I wouldn't hesitate to use another Crower cam.

 

Not yet. I'm going to build a 377 around that cam. I don't want to go with a roller. That cam has nice intensity and it looks like it's close to the original LT-1 design, but with more lift.