scott13676

iTrader: (1)

Need some sound advice on a roller cam selection. Its going in my 88 camaro. Its a 383. With the aluminum 64cc heads its going to be around 10.4 with the flat tops. TH400 with 3:50 gears. I have already ruled out a solid roller and anything that i have to run a monster stall. I dont mind a mild stall. Thanks,scott

Orr89RocZ

iTrader: (20)

What heads are on it? What intake manifold and assuming its gonna be carbed?

scott13676

iTrader: (1)

The heads are dart shp's, the intake will either be a holley 300-36 high rise or a eddy rpm. carb is a 750dp.

RamIt

Street, street/strip or track toy?

Orr89RocZ

iTrader: (20)

Good street strip cam would be a comp xe282hr on a 108 lsa. 110 will do but i like tighter lobe seps. Have to call comp and order it that way.

Lunati voodoo has some grinds too that are alittle more aggressive

What rods and crank you have? Just have to watch the rod to cam clearance in some setups.

skinny z

You're leaving a few critical bits of information out of your request so it's tough to nail down a real spec.
If we go with the "street/strip" notion, which is a fairly broad category, then you wouldn't be too far off the mark with the 282 as suggested. Or even less cam like the 276 (both hydraulic rollers). 10.4:1 SCR will build a lot of cylinder pressure with the 276 though. That's from my own experiences with "street" cars of various seriousness.
The critical spec is the amount of overlap any given grind will give you. It's the overlap that'll determine so many aspects of the final result: idle quality, low rpm tporque production, peak torque rpm...to name a few, that it really deserves a lot of research and some real life case studies to nail it down.
Take the 282 previously mentioned. With it's traditional 110 LSA, the overlap comes in at 62 degrees. That'll give a nice lope at idle but still not so much overlap that your idle vacuum is killed and low speed drivability starts to go away. Take that same cam and tighten up the LSA to 108 degrees and the overlap jumps to 66 degrees. Keep in mind that it's just not the number of degrees that affect a change in performance but the lift at the overlap period that really impacts things.
Take the 276 cam. It has 59 degrees of overlap with a 110 LSA. Move to 108 and the overlap moves up to 63 degrees. That more than the 282 had at 110.
All of that makes a real difference in how the engine is going to perform.
For what it's worth, an engine of 350 c.i. tends to respond well to the 108 LSA provided the overlap that results favours the intended use.
When in doubt, choose the smaller cam.
Another thing to consider in your ultimate choice is the efficiency of the exhaust system. From the port flow right through to the tailpipe. Many grinds today will have increased duration values for the exhaust. I understand that a lot of this duration is added to the opening side of exhasut lobe so as to allow more time for the cylinder to blow down. This helps to compensate for an exhaust system that lacks something in flow and produces backpressure that reduces the engines ability to evacuate the cylinder and draw in a full fresh charge.

scott13676

iTrader: (1)

I just want a nice nasty street car thats fun to drive. The rotating assembly is all scat with I beam rods. I was actually looking at the comp282. I saw the 383 build were they did the mild-med-max combos. I thought at first the 282 would be a little much on the street, but saw it turned on pretty good early in the power band. I understand what your saying about the overlap. My 82 T/A has a 350 with ported vortecs and a lunati streetmaster 275 cam with the 108. Its hits hard early and mid, but kinda peters out a little after 5,000. You think the 282 with the 110lsa would be better for my app than the 108?

couchmotors

do what i did, i called Lunati's tech line and talked with there tech guys and i gave them all my engine and car info and what i was using it for and what they recommened turned out great and i have no complaints

Orr89RocZ

iTrader: (20)

108 will make abit more midrange torque. The 110 should keep a tiny bit more top end after peak. Either one will work and are extremely well mannered in a 383. Should be a nice driver

scott13676

iTrader: (1)

Does lunati make oe style roller cams? i thought they only did retro fit. my block is a 87up. i think i will go with the 282 with the 110. thanks guys, much appreciated. scott

skinny z

As the cubic inches go up so does the LSA requirement.
You wouldn't be far of the mark with a 282 and a 110 LSA.
Again, that's dependent on a number of factors. With a 10.4:1 SCR you can take a reasonable amount of overlap/duration and still build some decent cylinder pressure. The XR276HR and that SCR (with everything else in spec) will produce about 200 psi (+ at sea level) in my 355's compression test. That'll require a carefully considered timing curve.
What's your target upper rpm limit?
For what it's worth, the XR276HR in my 355 pulled well past 6000 rpm, strongly through 6500 even though peak hp was probably realized at 5700 or so. Keep in mind that's a function of the cam combined with the heads. Certainly I wasn't making more power up top but the engine certainly had the capability to rev.
If you're really interested in Lunati, check out David Vizard's offering through them. He has a comprehensive line of cams spec'd the way he likes and a reasonable guide to help. Interesting stuff and certainly nothing along the lines of the traditional Comp offerings. Might be something to look at.
If have part numbers here somewhere.

Orr89RocZ

iTrader: (20)

Lunati does

skinny z

Yeah. Last time I was at the Lunati site, I couldn't find the DV spec cams. Might have changed since then.

scott13676

iTrader: (1)

if this motor sees above 6000rpm, it would be a stretch. at what point lift wise do you have to worry about the rods coming close to the cam? the rods im using have arp bolts for more clearance. So lunati does make a voodoo line for OE rollers?

RamIt

Here is their section for the factory hydo rollers.

http://www.lunatipower.com/Category.aspx?id=59

Orr89RocZ

iTrader: (20)

282hr will go to 6200 easy with that combo. Not a bad cam at all for what you are doing. Next size smaller would be 276hr and be strong to 5500. It would idle very smooth, slight lope if 108 lsa but shelf 110 isnt as bad in 383 cubes. Very popular cam in 350-383 street motors.

Lunati is abit more aggressive in the voodoo line.

skinny z

Does the voodoo line of lobes compare with Comp XFI lobes?
I picked a 274/224 intake lobe (Comp no. 3015) with .574 lift and an exhaust lobe with 282/230 ( Comp no. 3036) at .569". That's about as extreme a lift profile as I could find at the time of my last build (2 years ago). Vizard's profile through Lunati were new at the time.

RamIt

The voodoo lobes probably close to the xfi lobe opening but they set the valve down gentler than the xfi. No sewing machine sound with the voodoo cam.

Orr89RocZ

iTrader: (20)

Yup.

The magnum high lift in larger durations and 3100 series xe high lift have much high lifts than xfi. I used magnum high lifts alot. Valvetrain aint super noisey as they kinda open and close abit softer. Very stable tho. Had 230 deg .603" and a 246 deg .640" lobe so far. 7000 rpm no prob

skinny z

I was looking for max lift with minimal duration and a fast acting profile. The best I could find a few years back were the XFI series spec'd for use with a 1.6 rocker.
I'm finding the XFI lobes to be very noisy. Now to put this into context, I am running wih worn valve guides due to some earlier problems with the valve train geometry. That may enter into the noise profile somewhat.
Witness the atached video (better results to the video with a full speaker system).

Orr89RocZ

iTrader: (20)

Have you played with preload at all

skinny z

More than any one person could imagine.
I have the Comp short travel lifters and have had the preload everywhere from almost zero to about a 3/4 of a turn with a 7/16-20 thread. Recommended preload is about .015 thou or around 1/4 turn (+/-).
I know I have valve guide wear that approaches the service limit of .015" lateral on the stem on more than one cylinder. While I can attribute the "sewing machine noise" to the overall composition of the valve train, there's one lifter that stands out above the rest and it drives me nuts!

couchmotors

If your doing a cam change on this motor it would not take but a few more bolts to take the heads off and drop them off at your local head or machine shop for some much needed help putting a bigger cam is just going to destroy or break something with the added lift and stress.

Orr89RocZ

iTrader: (20)

With aggressive cams and high spring rates, geometry is king! Could be wearing guides because of incorrect alignment/pushrod lengths.
Thats what happened to me and why i went shaft rocker. Much easier to setup

I dont know much about the short travel lifters. Seems like less preload is ok for them. Regular lifters may like alot more. Morels are 1 turn on a 7/16 stud i believe. Ls7's guys are saying go .080"! That seems like alot. I ran 1/3-1/2 turns with ls7's. Never had noise.
My current valvetrain has abit of noise. Most of it is slight pushrod rub on heads on some cylinders but hard to tell over the injector noise

skinny z

That was exactly the case. I had followed the "BS" conventional approach to proper valve train geometry and concentrated as much on minimal sweep as I did trying the keep the pattern centred. As a result, I ended up a contact patch that was much too wide, probably .050" when .025" was achievable, but not running off the edge of the valve stem. Had I continued on, adding pushrod length, the sweep would have narrowed however the pattern was off the valve tip. So I stopped with a less than ideal result.
To correct it, I went with Crower .050" offset trunion rockers. This allowed more pushrod length which reduced the sweep while at the same time, pulled the pattern away from the edge. The result was a very narrow contact patch right on the centre of the valve tip. Perfect. Problem was, I had run the engine for a few thousand miles with poor geometry and am presently living with the results. The guides were on the serviceable limit at the last tear down but I reinstalled the heads as they were. Now I'm living with the consequences.
For now...
I appreciate the efficiency of the shaft rockers.