[drewhelm1974]

Curious to know if anyone is using it ans what kind of numbers are you putting down.

I replaced an UD solid flat tappet 255/263 with the Lunati solid roller 50715 and am VERY unhappy with it.

Can I run an UD solid flat tappet cam with roller lifters? I did notice Bullet is making a very similar grind in a solid roller.

Thanks,

Drew

[screamingchief]

Though I havent used the lunati cam you mention (#50715),I'll give my thoughts on it based soely on the specs of the cam itself.

First glance shows it to be quite an oddball cam for a solid roller,single pattern duration,very modest lift for a solid roller,and it's ground on a wide LSA too,so not the "average" solid roller,it looks to me that lunati was trying to fashion a very "entry level" "street" type solid roller cam with this item,and in trying to be "all things in every respect" they really made a so/so grind with that effort.

Ask me that lunati #50715 cam would be roughly equivalent to a RAIV hydraulic in many respects,so yeah,if a fella were expecting that cam to be a powerhouse cam based solely on it being a solid roller I would bet that fella would indeed be disappointed with the results.

And that cam would really be less than optimal in a lower compression "pump gas" style combo,the reason for that is this,for a cam that "size",it has a relatively late intake closing event.

I replaced an UD solid flat tappet 255/263 with the Lunati solid roller 50715 and am VERY unhappy with it.

No doubt,a "smaller" cam with a later intake closing event if both cams are installed as recommended,that would kill off both HP/TRQ,not to mention cylinder pressure as well,so I would expect a loss of low speed responsiveness as well with the lunati SR cam.

The UD solid FT closes it's intake valve at 49.5 degrees ABDC (@ .050") when installed at the recommended 102 ICL,that luntai solid roller closes it's intake at 54 degrees ABDC (@ .050") when installed at the recomended 110 ICL,so yeah,I can see why your not happy,should be pretty obvious.

The "bigger" UD solid cam on the tighter LSA,and installed advanced as recommended would almost always build more peak power and have much better mid range power than a cam like that "smaller" lunati solid roller,installed only slightly advanced as lunati recommends.

Can I run an UD solid flat tappet cam with roller lifters?

No,and even if you were to have a similar solid roller cam ground to the solid flat tappet UD cam you had,there would still be significant differences between the resulting cams,as solid roller lobes are "night and day" to flat tappet lobes.

I did notice Bullet is making a very similar grind in a solid roller.

Look at the lunati part #507A3LUN solid roller,it's about as close to the UD solid FT cam as your gonna find,it's based on the original UD lobes so that is as close to a carbon copy of the 288/296 UD solid flat tappet cam,except for being ground as a solid roller as your likely to find.

But I'm sure bullet can provide that same cam as well,as may others.

Said solid roller closes the intake at exactly 49.5 degrees ABDC (@ .050") just like the flat tappet UD solid.

Really would help to know more about the combo in question here though...

[Steve C.]

Curious, what are the specs on this Lunati 50715 solid roller ?

[Mo]

Originally Posted by Steve C.

Curious, what are the specs on this Lunati 50715 solid roller ?

Here ya go! http://www.holley.com/50715.asp

[screamingchief]

Here you go steve.

Does'nt seem to be too terrible a cam,but I still feel it's a bit of an odd duck.

What really suprised me was the noticably late intake closing event for the cam's relatively small "size",my guess is that was to try and get this to work well with the old iron head high compression engines,you know,as a sorta stock replacement high performance "fix-it" sorta deal.

If you read the description it sorta supports that premise as well.

Quote lunati:
Street/Strip Pontiac All V–8 (1955–1981) Solid Roller; Rough idle. Good cam for Pro street or mild bracket racing applications with good low end and mid range torque and horsepower. Needs 2500 RPM stall converter, headers, 9.5:1 compression ratio and 3.73 gearing. RPM Range: 2000-6500

I still feel we need more info on his combo for us to offer him any real advice here,but on the surface of that cam's specs I'd say I could definitely find something I feel is more suited to my build style.

Take for instance the similar sized crower "shelf" solid roller (#60451):
[specs:284/294 adv. 247/254 dur. @ .050",.582"/.567" lift w/1.5,108 LSA]
And you see it is ground on a 108 LSA,and it uses an intake closing event of 48 degrees ABDC (@ .050"),so I'm kinda suprised just how late that 112 LSA #50715 lunati is closing the intake valve due primarially to the wider LSA,and possibly to a lesser degree the single pattern duration specs.

If you look at crowers description of the #60451 in the attatchment I included below you'll notice it's a bit more aggressive sounding than lunati's description of the #50715,but crower has kinda always been like that with their descriptions.

That lunati #50715 has gotta kill off some degree of cylinder pressure,that's for sure!

On a "generic" 9.5:1 455 combo with these two cams I show a full half point loss of DCR using the wallace racing DCR calculator,and this shows a 14lb. loss of cranking compression as well,so yeah I kinda feel that lunati SR cam would be a decent cam for a "borderline high compression" combo that needs to bleed off a bit of cylinder pressure vs. being a questionable cam for a moderate compression "pump gas" combo.

Not real sure why lunati recommends 9.5:1 CR with that cam though,,,see below...

Examples below:

Combo A:Lunati #50715 SR cam
Your engine summary is as follows:
Bore - 4.18 inches
Stroke - 4.21 inches
Rod c-c length - 6.625 inches
With a static compression ratio of 9.5:1.
Your camshaft specifications call for an inlet valve closing of 75 degrees ABDC (after bottom dead center).Note:seat to seat valve event numbers.
Your chamber volume is 111.38 cc's. With this camshaft your dynamic, or effective stroke is 2.97 inches.
Your dynamic compression ratio is 7.00 :1 corrected for cam timing, altitude, and rod length.
Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 133.51 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.00:1

Combo B:Crower #60451 SR cam
Your engine summary is as follows:
Bore - 4.18 inches
Stroke - 4.21 inches
Rod c-c length - 6.625 inches
With a static compression ratio of 9.5:1.
Your camshaft specifications call for an inlet valve closing of 66 degrees ABDC (after bottom dead center).Note:seat to seat valve event numbers.
Your chamber volume is 111.38 cc's. With this camshaft your dynamic, or effective stroke is 3.25 inches.
Your dynamic compression ratio is 7.56 :1 corrected for cam timing, altitude, and rod length.
Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 147.69 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.56:1

I dunno,I just think that the lunati #50715 is a "niche" sorta cam for a specific type of application,and not really a more mainstream sorta solid roller cam,JMO/FWIW.

[Mo]

Originally Posted by drewhelm1974

Curious to know if anyone is using it ans what kind of numbers are you putting down.

I replaced an UD solid flat tappet 255/263 with the Lunati solid roller 50715 and am VERY unhappy with it.

Can I run an UD solid flat tappet cam with roller lifters? I did notice Bullet is making a very similar grind in a solid roller.

Thanks,

Drew

I thought I new this cam...http://mysite.verizon.net/shellybrown1/pontiac/

Nice cam.