Camshaft theoretical questions

I'm still wanting to put this mechanical roller cam in my truck because I'm over these hydraulic roller lifters. I like the cam that is in it but I think it could be a tad bigger. It's 220/220@.050 with a 108 LSA but only .427 lift with the current 1.5 rocker. I have a 246/246@.050, 108 LSA .498/.498 mechanical roller but I'm thinking that is too big. So the question is since those specs on the solid roller are figured at 0 lash approx. how much duration will I lose with .026 lash? Trying not to spend more money on this thing than I have too. I know there are factors that will play into the actual result like rate of lift etc. but just looking for something in general here. TIA.

I don’t know what your complete car package is, but your engine will wake up significantly above 3500 with that swap. The expected outcome and matched parts are all part of the equation.
As for your specific question, only a degree wheel can give you an accurate answer.

Yeah I know the degree wheel will give me an accurate answer and I will do that if I think it has a chance of getting me in the ball park. I have had a 239@.050 flat tappet hydraulic in it before and that worked out pretty good but ate a lobe. So if it puts me in 235-240@.050 range I think I'll be good.

Instead of worrying about how the two cams compare, just look at the overall vehicle combo, and whether or not a 246@.050 SR cam is appropriate for it.
If it is, it should work fine.

If the cam is too big, it’ll behave like a combo with too big of a cam in it.

yeah I get that. And like I said, it's probably too big.

What stall is your converter?
I would use that cam in a heart beat

I think the answer to your question is about 8° smaller at the valve (i.e. comparing to a hydraulic). That has always held true for the ones that I have measured and would guess that the 8° rule-of-thumb to be +/- 2° depending on lobe and lash setting.

IMO, if the 220/220 hydraulic is just a little to small, then the 246/246 mechanical will be more than just a little too big.

If your concern is idle quality, you should maybe compare the advertised durations too. Some hydraulic rollers have a pretty big on-ramp.

It's a stick but has a wide gear spread.

I think 8 degrees would get me in the ballpark of where I want to be. I'm not concerned with idle quality. This is my 4WD mountain truck. I drive it on the street but in 4WD low in the mountains it runs out of RPM pretty fast. With the wide ratio transmission I end up losing too much RPM. I want to just stick it in 2nd gear in low range and leave it there. So maybe 3000- 6000 RPM range.
The 220/220 cam pulls well from about 1200 to 4000 I just can't seem to find the sweet spot with the gearing. But what concerns me is it being a complete pig on the street below 3000, especially with the wide ratio transmission. I guess I'll find out.

IMO I think the ‘big’ cam will work fine since you have a stick. Vacuum might be a little low so you’ll need carb work to richen the idle feeds. Only thing that changes is the torque band goes up a bit. A 3.08 rear gear will hate it. 3.91 will like it.
Tighten that lash down to .012 ex and .08 in if not you’ll break rollers after awhile. .026 is for racing short term.

It has 4.10s with a 31" tall tire. Interesting about the lash, do circle track guys do that?

I've heard stories about the Nascar guys running zero lash, or the valves being slightly open when cold. In contrast, Comp eliminator guys opening up the lash to 0.038"-0.042"

Hmm, I have the Comp Cams Endure-X lifters with direct oiling to the needle bearings and pushrod oiling for the magnum heads and valve springs are 120 on the seat and 300 @ .500" . Nothing crazy but I could shim them a little for more pressure.

When Engle made me a cam up they said to use a tight lash as well. Said same thing about the rollers. They did a custom quick with the specs of the engine/driveline and car weight.

Knowing your use now I would install and degree that solid roller cam with between 3 to 6 degrees advance on the intake lobes
Be ready for more power than you may want though
Buy the best solid roller lifters (with .820 or larger wheels ) you can get and run at least 250 Lb. on the seats and 600+ lbs. over the nose to help the lifters to live, have the # 4 cam journal groove the width of the oiling passages in your new cam and around .030 to .045 deep this will help the valve springs live in your type of non drag race driving What type rockers and shafts are you using, needle bearings or non needle bearings with extruded aluminum, stainless steel or ductile iron
If needle bearings use a .040 to .065 restrictor in the rocker arm oiling passages, both sides if your using stock type rocker arm oiling, if external oiling like most Indy heads use put that size restrictors in each line to the heads

Probably fair to conclude that looser lash is harder on the valve train. But the ramp design matters. A lot of cams came with a recmmeded lash of 0.026" to 0.032"

It has aluminum full roller rockers but it's a magnum head on an LA block so the rockers are pushrod oiled. That sounds like a boatload of spring pressure. I should note that although I do drive this on the street it doesn't make 100 mile trips or anything like that and since I don't work nothing is driven daily anymore.

Correct. For what your doing, you don't need anything like that. Go with what the supplier or manufactured recommends for your lobes and rpm.

The springs I have are pretty close, I'll have to look at the cam card again to be sure.

If you don't like the hydraulic rollers just put the solid rollers on the same cam. If its a true hydraulic lobe profile it will have aggressive lobes so it will probably make more power on a solid roller lifter with tight lash(.012-.016). I wouldn't worry about duration loss with valve lash on a solid roller profile because some of the solid profiles can have really slow accel/decel ramps and just add unwanted overlap at tight lashes and you wouldn't be doing yourself any favors tightening the lash. If you have lobe numbers and the manufacture of both cams it would be easier to make a more accurate determination.
AG.

I have thought of this and going to a 1.65 or 1.7 rocker.

This was going to be my recommendation.

Engine Masters has an engine that runs solid roller lifters on a roller cam and it worked well for them.

Been tightening up all of my Isky solids and solid rollers forever......my .026 lash request was too damn noisy so .014 cold gets me about .020-.021 hot and runs great.....