How does a solid roller cam act vs solid flat tappet

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I think why people feel Stoker/large displacement engines shrink cam size, cause most large displacement engines are harder to feed "head cfm".
Take the average street strip cam probably gonna fall between 240-250 @ .050" and make peak power around 5700-6300 rpm.
If you look at head flow, cfm probably gonna be around 70% of displacement for that rpm. 273 = 190, 318 = 220 cfm, 340 = 240 cfm, 360 = 250, 390 = 270, 410 = 290, 440 = 310. A 245 @ .050" is gonna have a similar powerband for each of those cid:cfm combos but most are running and out of the box Eddy head maybe with a bit of port work on a 340-416 cjd engines so the larger displacements are starving head flow making the cam act smaller and move the powerband to a lower rpm.
 
rumblefish360 said:
That’s the popular belief which is inaccurate but has a basis in the way the engine sounds and reacts because the cam became smaller in a way. A duration @.050 cam like yours in a 361 low deck B engine is a whoopin race cam while in a displacement like yours and larger, it can be an EZ street bound cam.

Look at it with this example.

If you take that 361 CID engine and cam it with a small/medium Hyd. flat tappet of lets say 230@.050, what would be a similar cam to use in something at 500 cubes? You would have to go up in size to meet the requirements. The extra 139 cubes needs to be feed. That 230@.050 is now like a RV cam but will still have its operating rpm band that it lists & possibly a few rpm less. This operating rpm band the engine is in changes with the bore and stroke of the engine. It is also not set in stone how it will act and feel.

The 500 is roughly 39% larger. Your not going to need a cam 39% larger! It’s not a equal or linear growth size that’s needed. Perhaps only 7% more cam or more so probably less would produce a similar feel of how, when and actual feel when your behind the wheel driving.

It is something NOT to worry about. The cam still operates the engine in its rpm band reguardless. I the end, I say you’ll not notice at all.

Look up member Jim Lusk and his 470 build.
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Great that made perfect sense, it doesn't make it smaller, it moves it around in the rpm range. That's why a 383 cam is higher rpm rated before it makes power than the same in a 440, got it. Thanks alot. Eased my mind. I'll check out his build. Again, thank you a mcmillion
 
273 said:
I think why people feel Stoker/large displacement engines shrink cam size, cause most large displacement engines are harder to feed "head cfm".
Take the average street strip cam probably gonna fall between 240-250 @ .050" and make peak power around 5700-6300 rpm.
If you look at head flow, cfm probably gonna be around 70% of displacement for that rpm. 273 = 190, 318 = 220 cfm, 340 = 240 cfm, 360 = 250, 390 = 270, 410 = 290, 440 = 310. A 245 @ .050" is gonna have a similar powerband for each of those cid:cfm combos but most are running and out of the box Eddy head maybe with a bit of port work on a 340-416 cjd engines so the larger displacements are starving head flow making the cam act smaller and move the powerband to a lower rpm.
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ah, great points. I shouldn't be starving my 471 with trick flow 240s a track heat intake & a newer xp 950. (I think that's the carb I've decided on)
 
A roller acts like a roller and a flat tappet acts like a flat tappet. Was this a trick question? lol
 
MOPARMAGA said:
Great that made perfect sense, it doesn't make it smaller, it moves it around in the rpm range.
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Ever so slightly. The feel of the move is due to added stroke. If it was added bore, then it (The cam and engine feel) would just wake up more.

That's why a 383 cam is higher rpm rated before it makes power than the same in a 440, got it. Thanks alot. Eased my mind. I'll check out his build. Again, thank you a mcmillion
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Yes, as said above. The bore and stroke combo is an active player in the engine feel. The smaller engine (small stroke, big bore) has to make more rpm to move a similar amount of air where the cam starts to come alive. It’s operating rpm band. The larger engine, has a similar bore but the stroke is a lot longer. This extra travel is moving more air sooner and longer. Because of this, it is taking in more air and fuel making more power sooner. This makes the cam feel smaller.

Also, 273 makes a good note about the cylinder head selection which you have covered. But if you back up....
In the small block arena, a 273/318 head has small valves. 1.78-1.50. A stroker small block that has moved up to a 408 or even a 434 will not breath very well and it’s performance ceiling is, well, pretty dam short since a really nice head for that would be a set of trick flows or greater if raced. You could use a Edelbrock Victor Head with (IIRC) a intake valve at 2.15. These heads would produce spectacular results by themselves never mind a 318 head flowing 160 cfm vs the Victors 370 cfm.
 
rumblefish360 said:
Ever so slightly. The feel of the move is due to added stroke. If it was added bore, then it (The cam and engine feel) would just wake up more.


Yes, as said above. The bore and stroke combo is an active player in the engine feel. The smaller engine (small stroke, big bore) has to make more rpm to move a similar amount of air where the cam starts to come alive. It’s operating rpm band. The larger engine, has a similar bore but the stroke is a lot longer. This extra travel is moving more air sooner and longer. Because of this, it is taking in more air and fuel making more power sooner. This makes the cam feel smaller.

Also, 273 makes a good note about the cylinder head selection which you have covered. But if you back up....
In the small block arena, a 273/318 head has small valves. 1.78-1.50. A stroker small block that has moved up to a 408 or even a 434 will not breath very well and it’s performance ceiling is, well, pretty dam short since a really nice head for that would be a set of trick flows or greater if raced. You could use a Edelbrock Victor Head with (IIRC) a intake valve at 2.15. These heads would produce spectacular results by themselves never mind a 318 head flowing 160 cfm vs the Victors 370 cfm.
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Is there a formula for how much more flow is allowed vs valve size? I've got two sets in mind, my 440 source 210cc? 2.14 & 1.81 & also my trickflow 240cc 2.19 & 1.76 valves.
 
MOPARMAGA said:
Is there a formula for how much more flow is allowed vs valve size? I've got two sets in mind, my 440 source 210cc? 2.14 & 1.81 & also my trickflow 240cc 2.19 & 1.76 valves.
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Not that I’m aware of. While the size of a valve is a limiting factor, it’s not the only one. Shape of the valve, shape and cut of the seat, the various parts of the port from just under the valve (the “Bowl”) up to the port entrance/exit and every last micro meter in between account for the over all picture and abilities of the port.

The thing your looking for is the best area under the curve in the ports.

If I had two different heads with identical flow numbers, I’d choose the smaller port for the job. It should have a higher velocity and fill more quicker.

The larger port has its place. Perhaps super charged or NO2, a larger engine, a high screamer smaller engine? Depends on your goal. It has to be part of the well thought out package.

There is a point of installing a to large of a head for the engine displacement and level of power. I don’t see that as a problem with your build. The imbalance would have to be pretty big. Squeezing out every last bit of power per the goal of the build can be very different from a very mild street machine to a knock’em out drag beast. In this pictured scenario, swapping heads here would be terrible.

In your build (I missed? The compression/cam specs I think) a 470 & TF 240’s are an excellent combination. I’d run with that all day long, no problem, wouldn’t think twice about it or worry an once.

If you had stock small port 361 heads on top, I’d say that is a severe miss match and I’d guess your just rollin with what ya got until the wallet grows thicker.
 
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[QUOTE="rumblefish360, It has to be part of the well thought out package

470 & TF 240’s are an excellent combination. I’d run with that all day long, no problem, wouldn’t think twice about it or worry an once.

.[/QUOTE]

That's what will be going in my 67 Plymouth. Except I'll will only running D451 because I couldn't find a definite answer on if the D452 would fit on a low deck with trick flow heads
 
rumblefish360 said:
Not that I’m aware of. While the size of a valve is a limiting factor, it’s not the only one. Shape of the valve, shape and cut of the seat, the various parts of the port from just under the valve (the “Bowl”) up to the port entrance/exit and every last micro meter in between account for the over all picture and abilities of the port.

The thing your looking for is the best area under the curve in the ports.

If I had two different heads with identical flow numbers, I’d choose the smaller port for the job. It should have a higher velocity and fill more quicker.

The larger port has its place. Perhaps super charged or NO2, a larger engine, a high screamer smaller engine? Depends on your goal. It has to be part of the well thought out package.

There is a point of installing a to large of a head for the engine displacement and level of power. I don’t see that as a problem with your build. The imbalance would have to be pretty big. Squeezing out every last bit of power per the goal of the build can be very different from a very mild street machine to a knock’em out drag beast. In this pictured scenario, swapping heads here would be terrible.

In your build (I missed? The compression/cam specs I think) a 470 & TF 240’s are an excellent combination. I’d run with that all day long, no problem, wouldn’t think twice about it or worry an once.

If you had stock small port 361 heads on top, I’d say that is a severe miss match and I’d guess your just rollin with what ya got until the wallet grows thicker.
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Cam specs howards solid f/t 260-264 @.050 .616-.620 lift with 1.5 rockers .
Compression should be right at 11.40:1
Rod ratio of 1.71 (If that matters)
 
MOPARMAGA said:
Cam specs howards solid f/t 260-264 @.050 .616-.620 lift with 1.5 rockers .
Compression should be right at 11.40:1
Rod ratio of 1.71 (If that matters)
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Cool.
Rod ratio is over played and dissected way to much. I myself like a lot of it, more the merry, but the effects between a high ratio and a low one are so minor and dumb IMO to argue over stating which is the best and better or perfect for what ever. Over square/under square engine still make power. Big rod small rod, etc.... It’s all such small small potatoes.
 
rumblefish360 said:
Cool.
Rod ratio is over played and dissected way to much. I myself like a lot of it, more the merry, but the effects between a high ratio and a low one are so minor and dumb IMO to argue over stating which is the best and better or perfect for what ever. Over square/under square engine still make power. Big rod small rod, etc.... It’s all such small small potatoes.
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Yeah I'd like for the ride in a car with each & whoever says 1 is better than the other take a guess, it sounds to me it's just a wash or something like that.
 
I just remembered .... IF you have motor trend on demand, check out engine masters. Not long ago, they ran a few of these tests we are talking about.
 
Things like rod ratios are only to be worry about in a highly competitive racing like Nascar, or people with deep pockets for the rest of us cylinder heads is where it's for bang for the $$$$. Saying that for me I would probably never build a 4" stroke small block I see why people do, But there's tons of 383,400,440 out there with displacement and good bore rod and stroke ratio's, it's one of the advantages already built into Chrysler engine's don't see no reason to build it out of them and if I want a short rod engine I'd build a stroker 440.
 
rumblefish360 said:
I just remembered .... IF you have motor trend on demand, check out engine masters. Not long ago, they ran a few of these tests we are talking about.
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There's a Small block Chev dyno comparison with 5.565" 5.7" 6", and there was like a 5-6 hp difference between them.
 
The episode wasn’t to show how to take a vantage of a different ride ratio, just strictly the difference of what happens when you put in different length rods into the same engine.

They also did one with engine stroke differences I believe. Or maybe even a few of them?
 
273 said:
Nope everything was the same between.
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Yeah I thought that you can optimize a particular engine build by choosing the right rod ratio. It's said that the shorter rod draws in more fuel & air faster when the piston is on "suck" & a longer rod vice versa gets it out faster. But All that seems to be a cam could be ground to be perfect for any particular r.r. also it's said big ports are good for the short rod & and small for longer rods. That part makes sense.
But I'm no expert.
 
MOPARMAGA said:
Yeah I thought that you can optimize a particular engine build by choosing the right rod ratio. It's said that the shorter rod draws in more fuel & air faster when the piston is on "suck" & a longer rod vice versa gets it out faster. But All that seems to be a cam could be ground to be perfect for any particular r.r. also it's said big ports are good for the short rod & and small for longer rods. That part makes sense.
But I'm no expert.
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Rod ratio plays a big part when the engine is induction limited. And I say anything with a 4 inch stroke and less than a W2 head is induction limited. Even a 3.79 stroke puts a load on the W2 head. And the single 4 intake.

Chrylser did a tom of testing on 2V carb stuff and found power. Too bad they didn’t test what a stroker does to the induction system.

And I’ll add this. If your cam grinder doesn’t take into account r/s ratio you need another cam grinder.
 
MOPARMAGA said:
it's said big ports are good for the short rod & and small for longer rods. That part makes sense.
But I'm no expert.
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I never heard that. I just build with the stock rod ratio and tune to the engines needs. I’m on the street mostly with A rare trip to the track.
 
MOPARMAGA said:
Is there a formula for how much more flow is allowed vs valve size? I've got two sets in mind, my 440 source 210cc? 2.14 & 1.81 & also my trickflow 240cc 2.19 & 1.76 valves.
Click to expand...

Why not 2.19 and 1.81 ?????????
 
famous bob said:
Why not 2.19 and 1.81 ?????????
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On the trick flows? Perhaps this may explain why? IDK

upload_2020-6-16_8-52-44.jpeg
 
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