Please forgive my ignorance with this question. I'm trying to get an idea here. I was looking at possibly buying a new engine for a decent price with a but though.... The but is at what point does a solid roller become uneasy to live with on the street? My concern is that the Cam is a Comp with around .660/.640 lift. Don't yet know other info. It has Morel lifters, and Erson 3860 springs. Which are 240/650 seat and open. Heads are -1's with a Modern CNC job. Will these live on the street for a while? I don't mind maintenance, but I don't know how often or what since it's new. Also don't know if there were any oil/block mods to the block. Sorry if I have something wrong or it's an obvious answer, I don't know. That's why I'm asking. It's a 74 440 block with an Eagle 4.15/Diamond kit.

I ran a 700 lift roller cam on the street for years. 245/590 Isky tool room springs. Zero problems. Lots of 15 to 20 miles type jogs all the time in it. And lots of passes at the track every season.
Go for it

I would drive the hell out of it and check lash / change the oil every 500 miles. If the fuel/timing curve is correct and you have a coated gear the frequency of maintenance could be extended.

If you drive it hard check things over often. Much easier to catch a broken valve spring under the rocker cover than picking the pieces out of the oil pan lol.

Do you have a cam card? How far is the block bored?

Some cam lobes are designed for longevity and some for max power during limited usage. Without knowing more details about the cam you have, nobody can tell you what to expect.

15-20 miles ok. What about 75-100 miles. Just nervous If I were to buy it, I'll munch something rather quickly

Get all the details on the cam and I'm sure someone here will be able to tell you if it has endurance lobes or "you really don't want to drive on the street with that" lobes.

I have done 6 drag weeks with solid roller lifters. Stay on top of your lash, make sure the springs match your combo, and keep your ears open it will tell you if it something isn't right.

I usually check them a few times on drag week, they get loud after hours on the highway, and in my head I always think one is really loose, and it never is lol. Hours on the highway @200* gets the oil and everything nice and hot so the lash gets wider than normal I am sure, it is usually all good the next morning when I check them.

You can find all sorts of stories. I know plenty of guys who have tore up engines because a solid roller lifter came apart while they were driving down the freeway or around town. Then there are guys who drive them a lot without any trouble. As others have said, it is the details that matter. Good lubrication, proper clearances, picking the right lobe, matching the springs to the lobe, using high quality parts, etc.

All good advice - keep after the lash, any 1 valve that changes quickly may be something getting ready to die. Loose lash is what kills tappet rollers.
If you don't know what quality rockers you have, get good ones.

Whose rockers come in the -1 kit from Indy? That's what is on them.

It’s been years since I ran a solid roller on the street. But when I did the standard week end was over 200 miles. I didn’t own a trailer and the town I street raced in was 40 miles away. A lot of the time we would go on Friday and Saturday night. That was 160 miles to get there and get home, not counting cruising or racing once we got there. I put 1000’s of miles on that engine. Broke one tie bar in all those miles. It had one thing that I think is a very good idea. The engine had a rev kit. Basically an extra set of springs that kept the slack out of the lifters. This was in the 70’s so I would think lifters are much better now than then.

A rev kit is a great idea for a solid roller that is street driven but I don't think they are available anymore for Mopar engines. I'm not sure rev kits are available anymore for any engine. The engine shop I work with used to put rev kits in everything but over the years the rev kits have been discontinued.

It depends on when those heads where sold by Indy, if they are black or deep purple extruded aluminum , no needle bearings on the shafts, their probably Doves

If it were mine i would find out exactly what every part of the valve train is. It is the whole combo that makes the difference . If the rockers are doves they have a reputation of limited strength. Probably OK for a flat tappet cam or mild solid roller that won't need a lot of spring. Once you know what is in the motor you can go to a knowledgeable engine builder and come up with a plan. IMHO pressure fed lifters are a very good idea. A cam with endurance type lobes or milder also.
I keep a close eye on lash and am very carefull to check at as close to each 90 degree move, 90, 180 , 270. 0. Cams do flex under spring load and the bigger the springs the more important this becomes. If you see a valve get loose by more than .002 start looking for the problem. My last inspection #6 intake was .003 loose. I have Jesel paired rockers and the intake rocker felt fine till i tried to rotate it full circle on its' shaft. On further inspection the rocker shaft was galled and the roller bearing would have gone bad next, filling my motor with nasty crap. I once had the needles wind up in the oil pump , ruin all the bearings, scratch the cylinder walls, and broke the pump drive
Shaft. So now i keep notes and if anything changes even a little like + .001 or close to .002 it gets rechecked again very soon. Any more movement and i know something is going away.

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gregsdart is spot on...

I will add that having pressurized oil to the bottom of the lifter greatly improves longevity.Also keep spring pressures pressures well under 700# over the nose and a non aggressive lobe.
I sent mine back to be rebuilt with 5 years and about 7500 miles and they only wanted to rebuild 3 lifters,I told them to please do ALL of them at $12 each!!!

Useful rev kit springs are still available, but no specific attachment hardware (or even dimensions) to install. Typically, this levers against the underside of the head casting with seats for the springs following the tappet bore locations exactly. Somewhere there are SBC & BBC install pictures?

Aggressiveness of the lobe, quality of parts and RPM are going to determine maintenance schedule and longevity of parts.

Max effort? Fun cruising car? Cam can always be swapped to one that better suits your needs/goals.

.660/.640 is not that big and the springs seem fairly mild. Need to know lobe design.

I've driven my .680-.660 276-281 @ .050 ISKY solid roller up to 1 1/2 hours for a local movie shoot in L.A. County when I live in S.B. county and many miles since then and a few hundred passes as well. Gentle lobes and frequent lash checks/setting go a long way. Started at 210/530 pressures and stepped up to 245/600 7 years ago.......

Do you know what the duration is at .050 lobe lift and what lobe center the cam is ground on?