Who is a cam expert here?

[Zachalanche]

HI,
I have a camshaft in my 418 stroker that I've never known the specs. its a custom grind, so I also can't just look up a part number. So I got out the degree wheel and as best I can tell here are the specs I came up with

intake lift	0.646
intake duration	325
intake duration @.050	249.6
exhaust lift	0.6494
exhaust duration	320
exhaust duration @.050	257.5
LSA	111.525
overlap	99.45
intake centerline	111.8

this may not be 100% perfect, but it should be pretty close.



This engine ran well and pulled pretty hard all the way to 7000 rpms. it made 449 whp @ 6020 rpm and 420ft-lb @5240 rpm on a dynojet. this was through a T56 magnum and ford 9 in with 315 wide rear tires.

I always thought this engine should have made a little more power since it was supposed to be around 600 crank. Now that I have an idea what the cam specs are, it seems like the cam has quite a bit of duration and lift. although the LSA is on the narrow side, so I'm not sure how that affects the power characteristics. but I'm thinking it should make decent power in a stroker motor. Does anyone know if there is a better cam that would make a little more top end power and maybe be better suited for a track car?

[68Formula]

That's a pretty healthy camshaft even for a 418 stroker. The power numbers aren't too far off going crank to rwhp, but with that cam should be a lot more. Also depends on the dyno calibration and the corrections.

But what's interesting is how low of an rpm the peak hp comes in. Tells me there's probably something else with the setup holding it back above 6k. What header type (shorty, mid-length, long tubes), primary size, collector size, and exhaust size are you running? Which mufflers? What air assembly, throttle body size, intake, and heads are you running?

And finally, what was the air fuel ratio from 5k-7k rpm? Was the timing optimized on the dyno?

And if a new cam makes sense (and it probably will) what's your compression ratio? And rectangular or cathedral ports? Which types of track use are planned?

[Zachalanche]

That's a pretty healthy camshaft even for a 418 stroker. The power numbers aren't too far off going crank to rwhp. Also depends on the dyno calibration and the corrections.

What's interesting is how low of an rpm the peak comes in. Tells me there's probably something else with the setup holding it back. What header type (shorty, mid-length, long tubes), primary size, collector size, and exhaust size are you running? Which mufflers? What air assembly, throttle body size, intake, and heads are you running?

And finally, what was the air fuel ratio from 5k-7k rpm? Was the timing optimized on the dyno?

And if a new cam makes sense, what's your compression ratio? And rectangular or cathedral ports?

Thanks for replying. these are the kind of thoughts I'm looking for. Maybe I need to be finding flow restriction somewhere. here's some more details:

1 -7/8 mid length headers with 3in collector to 3in exhaust X-pipe to 3 in warlock mufflers then smooth transition to 2-1/2 in tail pipes. - I think switching to a better muffler might free up some hp the warlocks probably flow worse than a turbo muffler when the caps are on.

102mm TB, FAST LSX 102 intake, stock LS3 heads

air fuel is 12.5 (on average, with slight variation) from 5k-7k. and a lot of time was spent tuning timing so I'm hoping its good.

Compression ratio is 11.5:1, rectangle port - stock LS3 heads

[68Formula]

Immediately I see 2 issues of using that camshaft in your setup.

First let's talk about Dynamic Compression Ratio (DCR). It's a bit of a misnomer since it's not relative to a running engine, but it's a calculation of the effective compression ratio taking the intake valve closing (IVC) @ .006" lift into account. Too high, is a good indicator of octane needs of an engine. Of course there are other factors that can come into play, but it's a great guide. Second, if the DCR is too low, can cause a decrease across the entire rpm range. For 93 Octane a range of 8.3 to 8.6 is desired.

Second, let' talk valve events @ . 050". Quick terminology: I/O = Intake Open, I/C (or IVC) = Intake Close, E/O= Exhaust Open, E/C = Exhaust Close:

I'm just going to highlight the areas where I feel affect you directly. If you want a little more in depth, read this: https://help.summitracing.com/knowle...SR-05440/en-us
IVC is a major player in the rpm range (later moves the power band up, at the sacrificing low-end. I/O and E/C effect the overlap which really affects a lot of characteristics, but even independently how they are biased is also important, especially depending on the combination. Long tube headers with collectors scavenge well. Especially on a dyno where there's usually no simulated exhaust other than those 2 components. They respond well to large overlap and E/C well past piston ABDC on the exhaust stroke. But mid-length and shorties with their shorter primaries do not. With those types, a max of 3-4* ABCD is recommend in order to avoid excessive reversion not only at part throttle, but WOT as well and into high rpm. This is a case where what looks great on a dyno and behave very different when it's in a vehicle. All of these while seemingly smaller, will make power not only below 6k, but above as well.

Now let's look at your current setup:
@ .006" the IVC = 94* That leaves you with a dismal 6.7 DCR. Waaayyyyy to low.
@ 0.050": 13.5 I/O, 56.5 I/C, 60.5 E/O, 17.5 E/C for 15 degrees of overlap.
Too late an I/C, Overlap is a crazy 31*! And the E/C too late for mid-length headers. And honestly, a 418 shouldn't need this much intake duration to reach it's peak power within a 7k operating range (240* should be enough), especially with square ports.

You could solve this with a custom camshaft. But Summit actually created camshafts for caters to exhausts limitations to scavenging and wave effects from a full exhaust. Note the overlap (OL) and EC events.

Big Gun 1 SUM-8729R1 is a 10 I/O, 50 I/C, 65 E/O, 3 E/C for 13 degrees of overlap. (240/247 115.5 LSA + 5.5 Adv. .625/.605). The I/C @ .006 = 74* resulting in a 8.5 DCR.

Big Gun 2 SUM-8730R1 is a 11 I/O, 51 I/C, 67 E/O, 4 E/C for 15 degrees of overlap. (242/251 116 + 6, .625/.605). The I/C @ .006 = 76* resulting in a 8.3 DCR.

Big Gun 3 SUM-8731R1 is a 14 I/O, 53 I/C, 71 E/O, 4 E/C for 18 degrees of overlap. (247/255 117 + 7 .625/.605). I/C @ .006 = 79 resulting in a 8.1 DCR.

There's also a 4, but you'll see why I'm not bothering about that.

The BG3 has a low DCR for racing. It's going to be down on torque though low & mid-range compared to the other 2. And it still has more intake duration than the engine can even take advantage of. So BG4, which you can imagine is even bigger isn't even a thought.

So we're narrowing in on BG1 vs. BG2:
The BG1 is on the upper end for DCR, but still within premium gas capability. Least amount of OL, earliest E/C. It'll have the most low/mid=range torque. t's going to have very long powerband. On tracks with tight turns, it'll give the best torque off a corner, and still with a long powerband. It could also eliminate the need to downshift which can save a lot of time. Normally with a 418 and headers the BG2 will have just a few more ponies (<10hp) right at the top (6500rpm-7500rpm). But with the mid-lengths, it may have no gain at all.

Since you do have the mid-lengths the BG1 has the best compatibility, and for it's size, to me, it's ideal choice for your setup. In any case, either BG1 or BG2 will be a huge improvement to your current setup.

If I was to do a custom cam, it'd probably be a 240/254 117+7 (assuming a .006 to .050" delta of ~50*). 10 I/O, 50 I/C, 71 E/O, 3 E/C for 13 degrees of overlap. So the I/C and OL, same as the BG1. However it allows more exhaust duration to evacuate the system, but still with same E/C of BG1.

If you decided to swap out the mid-length for long tubes, I'd still pick a different cam than your current one. And if you do switch, try to go with 2" primaries. Haven't seen data on the Warlock mufflers, but from the cut-away I'd expect it to be relatively restricted compared to other designs.

[Zachalanche]

Immediately I see 2 issues of using that camshaft in your setup.

First let's talk about Dynamic Compression Ratio (DCR). It's a bit of a misnomer since it's not relative to a running engine, but it's a calculation of the effective compression ratio taking the intake valve closing (IVC) @ .006" lift into account. Too high, is a good indicator of octane needs of an engine. Of course there are other factors that can come into play, but it's a great guide. Second, if the DCR is too low, can cause a decrease across the entire rpm range. For 93 Octane a range of 8.3 to 8.6 is desired.

Second, let' talk valve events @ . 050". Quick terminology: I/O = Intake Open, I/C (or IVC) = Intake Close, E/O= Exhaust Open, E/C = Exhaust Close:

I'm just going to highlight the areas where I feel affect you directly. If you want a little more in depth, read this: https://help.summitracing.com/knowle...SR-05440/en-us
IVC is a major player in the rpm range (later moves the power band up, at the sacrificing low-end. I/O and E/C effect the overlap which really affects a lot of characteristics, but even independently how they are biased is also important, especially depending on the combination. Long tube headers with collectors scavenge well. Especially on a dyno where there's usually no simulated exhaust other than those 2 components. They respond well to large overlap and E/C well past piston ABDC on the exhaust stroke. But mid-length and shorties with their shorter primaries do not. With those types, a max of 3-4* ABCD is recommend in order to avoid excessive reversion not only at part throttle, but WOT as well and into high rpm. This is a case where what looks great on a dyno and behave very different when it's in a vehicle. All of these while seemingly smaller, will make power not only below 6k, but above as well.

Now let's look at your current setup:
@ .006" the IVC = 94* That leaves you with a dismal 6.7 DCR. Waaayyyyy to low.
@ 0.050": 13.5 I/O, 56.5 I/C, 60.5 E/O, 17.5 E/C for 15 degrees of overlap.
Too late an I/C, Overlap is a crazy 31*! And the E/C too late for mid-length headers. And honestly, a 418 shouldn't need this much intake duration to reach it's peak power within a 7k operating range (240* should be enough), especially with square ports.

You could solve this with a custom camshaft. But Summit actually created camshafts for caters to exhausts limitations to scavenging and wave effects from a full exhaust. Note the overlap (OL) and EC events.

Big Gun 1 SUM-8729R1 is a 10 I/O, 50 I/C, 65 E/O, 3 E/C for 13 degrees of overlap. (240/247 115.5 LSA + 5.5 Adv. .625/.605). The I/C @ .006 = 74* resulting in a 8.5 DCR.

Big Gun 2 SUM-8730R1 is a 11 I/O, 51 I/C, 67 E/O, 4 E/C for 15 degrees of overlap. (242/251 116 + 6, .625/.605). The I/C @ .006 = 76* resulting in a 8.3 DCR.

Big Gun 3 SUM-8731R1 is a 14 I/O, 53 I/C, 71 E/O, 4 E/C for 18 degrees of overlap. (247/255 117 + 7 .625/.605). I/C @ .006 = 79 resulting in a 8.1 DCR.

There's also a 4, but you'll see why I'm not bothering about that.

The BG3 has a low DCR for racing. It's going to be down on torque though low & mid-range compared to the other 2. And it still has more intake duration than the engine can even take advantage of. So BG4, which you can imagine is even bigger isn't even a thought.

So we're narrowing in on BG1 vs. BG2:
The BG1 is on the upper end for DCR, but still within premium gas capability. Least amount of OL, earliest E/C. It'll have the most low/mid=range torque. t's going to have very long powerband. On tracks with tight turns, it'll give the best torque off a corner, and still with a long powerband. It could also eliminate the need to downshift which can save a lot of time. Normally with a 418 and headers the BG2 will have just a few more ponies (<10hp) right at the top (6500rpm-7500rpm). But with the mid-lengths, it may have no gain at all.

Since you do have the mid-lengths the BG1 has the best compatibility, and for it's size, to me, it's ideal choice for your setup. In any case, either BG1 or BG2 will be a huge improvement to your current setup.

If I was to do a custom cam, it'd probably be a 240/254 117+7 (assuming a .006 to .050" delta of ~50*). 10 I/O, 50 I/C, 71 E/O, 3 E/C for 13 degrees of overlap. So the I/C and OL, same as the BG1. However it allows more exhaust duration to evacuate the system, but still with same E/C of BG1.

If you decided to swap out the mid-length for long tubes, I'd still pick a different cam than your current one. And if you do switch, try to go with 2" primaries. Haven't seen data on the Warlock mufflers, but from the cut-away I'd expect it to be relatively restricted compared to other designs.

Dang. that was awesome. thank you for the time you spent on this. This is the kind of expertise I was looking for.

Now I see why my tuner was badmouthing my cam when I had this tuned so many years ago. Sounds like BG1 or similar is a good solution. I already had plans to ditch the mufflers I have, so that should help too. In general, the car already hits pretty hard at any rpm, but I have been in a couple turns where I wish I had more torque in 3rd leaving me either trying to scream through second, or lug through 3rd.

[68Formula]

Dang. that was awesome. thank you for the time you spent on this. This is the kind of expertise I was looking for.

Now I see why my tuner was badmouthing my cam when I had this tuned so many years ago.

Haha, I bet. From sounds of it, he did an amazing job considering what he had to work with. That's pretty much a drag race cam meant for a 454LSX with open headers.

[Zachalanche]

Haha, I bet. From sounds of it, he did an amazing job considering what he had to work with. That's pretty much a drag race cam meant for a 454LSX with open headers.

Allegedly (and im not sure theres any truth to this), this engine was built for an air boat. Wonder if that cam makes more sense in that application. Otherwise I'm confused as to why a custom grind like this was needed.

[68Formula]

Allegedly (and im not sure theres any truth to this), this engine was built for an air boat. Wonder if that cam makes more sense in that application. Otherwise I'm confused as to why a custom grind like this was needed.

Well, they do tend to run long tube headers with a few feet worth of tubing and no mufflers etc. Plus high rpm for rotor speed. Still the cam is bigger than the engine can even use. Especially if the heads aren't ported.

[Zachalanche]

Now let's look at your current setup:
@ .006" the IVC = 94* That leaves you with a dismal 6.7 DCR. Waaayyyyy to low.
@ 0.050": 13.5 I/O, 56.5 I/C, 60.5 E/O, 17.5 E/C for 15 degrees of overlap.
Too late an I/C, Overlap is a crazy 31*! And the E/C too late for mid-length headers. And honestly, a 418 shouldn't need this much intake duration to reach it's peak power within a 7k operating range (240* should be enough), especially with square ports.

I made the mistake of telling you the total duration based on the moment the dial indicator started to move. I went back through my spreadsheet and calculated the duration and valve events at .006 lift. (keep in mind I recorded readings every 10* of crank rotation, so I did a linear interpolation to find anything in between, so there could be some minor error here, but hopefully not too bad).

So, due to my mistake we were thinking this cam was bigger (more duration) than it really is. It's still a very high duration cam, but the IVC happens much sooner (77.5*) than we thought initially with brings my DCR into the 8.1 range. here are my updated cam specs, I threw in the BG1 cam for comparison



The IVC and resulting DCR is not so bad. but the lobe separation is tighter by a good margin. This makes the valve overlap a bit more than the summit cam, and I assume this increased overlap would benefit from long tube headers and a more open exhaust.

Sorry to mislead you earlier, but what are your thoughts on this cam now....if any different from before. I'm thinking exhaust reversion is still going to be a big issue for me.

Cheers.

[68Formula]

I made the mistake of telling you the total duration based on the moment the dial indicator started to move. I went back through my spreadsheet and calculated the duration and valve events at .006 lift. (keep in mind I recorded readings every 10* of crank rotation, so I did a linear interpolation to find anything in between, so there could be some minor error here, but hopefully not too bad).

So, due to my mistake we were thinking this cam was bigger (more duration) than it really is. It's still a very high duration cam, but the IVC happens much sooner (77.5*) than we thought initially with brings my DCR into the 8.1 range. here are my updated cam specs, I threw in the BG1 cam for comparison



The IVC and resulting DCR is not so bad. but the lobe separation is tighter by a good margin. This makes the valve overlap a bit more than the summit cam, and I assume this increased overlap would benefit from long tube headers and a more open exhaust.

Sorry to mislead you earlier, but what are your thoughts on this cam now....if any different from before. I'm thinking exhaust reversion is still going to be a big issue for me.

Cheers.

Corrrect: DCR much closer to where you want it; but still too late EVC and too much OL leading to reversion with the current setup.

[Zachalanche]

@68Formula
Gonna give this cam a go. thanks for your support.

[andrewb70]

I made the mistake of telling you the total duration based on the moment the dial indicator started to move. I went back through my spreadsheet and calculated the duration and valve events at .006 lift. (keep in mind I recorded readings every 10* of crank rotation, so I did a linear interpolation to find anything in between, so there could be some minor error here, but hopefully not too bad).

So, due to my mistake we were thinking this cam was bigger (more duration) than it really is. It's still a very high duration cam, but the IVC happens much sooner (77.5*) than we thought initially with brings my DCR into the 8.1 range. here are my updated cam specs, I threw in the BG1 cam for comparison



The IVC and resulting DCR is not so bad. but the lobe separation is tighter by a good margin. This makes the valve overlap a bit more than the summit cam, and I assume this increased overlap would benefit from long tube headers and a more open exhaust.

Sorry to mislead you earlier, but what are your thoughts on this cam now....if any different from before. I'm thinking exhaust reversion is still going to be a big issue for me.

Cheers.

I don't mean to downplay the discussion, but moving cam specs a little one way or the other is matter of 5-10HP on this engine. Fiddling around the edges of the cam specs is not going to be a 40-50HP jump.

What I have experienced over the last 5 years of tuning is that most people over cam their engines. The best bang for the buck are the three things that will impact power the most are:

1. displacement
2. heads
3. cam

Big engines with great heads and a modest cam result in the best overall combination for a street car.

Andrew

[streetk14]

I don't mean to downplay the discussion, but moving cam specs a little one way or the other is matter of 5-10HP on this engine. Fiddling around the edges of the cam specs is not going to be a 40-50HP jump.

What I have experienced over the last 5 years of tuning is that most people over cam their engines. The best bang for the buck are the three things that will impact power the most are:

1. displacement
2. heads
3. cam

Big engines with great heads and a modest cam result in the best overall combination for a street car.

Andrew

Thats more or less what I was going for. 427 cubic inches, Tony Mamo LS7 heads, and a 231/245 116+3. I’d like to get it back on the dyno, but this thing really needs a 3” exhaust.

[Jk918]

Seams to me that its down quite a bit on power for 418, I've seen quite a few ls3 with just a cam BTR stage 4 and a good tune , headers, put down 500+ at tires through 6spd. Although I understand every dyno is different.

[streetk14]

I’m not an expert, but assuming those specs are correct, that’s a big ass cam. As was mentioned, it should be making peak power way higher in the rpm range. Maybe you have a valve control issue or something? My mild cam LS7 makes peak power around 6500 and carries well to 7000. That’s with a little (for a 427) 227/242 116 cam and 2.5” exhaust.

A dyno is a dyno so you have to take baseline numbers with a grain of salt, but my crate engine is rated at 570 hp from GM with Z28 exhaust manifolds. I have long tubes and a ported MSD manifold with a 103 TB. Made 520 whp through a T56 Magnum and 3.89 geared 9”.

[68Formula]

I’m not an expert, but assuming those specs are correct, that’s a big ass cam. As was mentioned, it should be making peak power way higher in the rpm range. Maybe you have a valve control issue or something? My mild cam LS7 makes peak power around 6500 and carries well to 7000. That’s with a little (for a 427) 227/242 116 cam and 2.5” exhaust.

A dyno is a dyno so you have to take baseline numbers with a grain of salt, but my crate engine is rated at 570 hp from GM with Z28 exhaust manifolds. I have long tubes and a ported MSD manifold with a 103 TB. Made 520 whp through a T56 Magnum and 3.89 geared 9”.

Wow, wish my Bird had that setup!

The LS427/570hp illustrates my point exactly. The cam is designed to be compatible with Z28 exhaust manifolds which are basically a factory mid-length header. Thus the overlap is limited to 2.5*. Can't find any info on the amount of advance if any. But unless it's ground retarded, E/C= 5* ATDC @ the most. They designed the camshaft to work specifically with a mid-length "header" exhaust manifold and full exhaust. Same reason even the largest of the Summit "Big Gun" cams (SUM-8732R1) still keeps the E/C @ 4*.

[streetk14]

Wow, wish my Bird had that setup!

The LS427/570hp illustrates my point exactly. The cam is designed to be compatible with Z28 exhaust manifolds which are basically a factory mid-length header. Thus the overlap is limited to 2.5*. Can't find any info on the amount of advance if any. But unless it's ground retarded, E/C= 5* ATDC @ the most. They designed the camshaft to work specifically with a mid-length "header" exhaust manifold and full exhaust. Same reason even the largest of the Summit "Big Gun" cams (SUM-8732R1) still keeps the E/C @ 4*.

I’m pretty happy with it and glad I was able to grab one before they were discontinued. While not cheap, I thought it was a bargain for what I was getting after pricing out LS3 stroker builds.

I never was able to find any info on the 427/570 cam’s advance either, but it’s a mild lobe that uses stock valve springs and the same lift as a stock LS7. But it has good drivability and still makes decent power.

I’m working on phase 2 right now, and have former AFR head designer Tony Mamo building me a set of his 265cc LS7 heads. I still need to pick a cam. Leaning towards a 231/245 116+3 since good drivability is one of my must haves. 6 degrees of overlap is still considered mild in an LS7, and his smaller, higher flowing intake ports should reduce reversion and help it drive better. That’s the goal anyway.

Sorry for the thread hijack, but I guess we’re still talking cams, right?

[68Formula]

I’m pretty happy with it and glad I was able to grab one before they were discontinued. While not cheap, I thought it was a bargain for what I was getting after pricing out LS3 stroker builds.

I never was able to find any info on the 427/570 cam’s advance either, but it’s a mild lobe that uses stock valve springs and the same lift as a stock LS7. But it has good drivability and still makes decent power.

I’m working on phase 2 right now, and have former AFR head designer Tony Mamo building me a set of his 265cc LS7 heads. I still need to pick a cam. Leaning towards a 231/245 116+3 since good drivability is one of my must haves. 6 degrees of overlap is still considered mild in an LS7, and his smaller, higher flowing intake ports should reduce reversion and help it drive better. That’s the goal anyway.

Sorry for the thread hijack, but I guess we’re still talking cams, right?

With the long tubes, but 2.5" exhaust and your compression ratio, and the MAMO heads, I'd:

• Bring the IVC earlier
• Increase the exhaust duration
• Allow slightly more overlap to take advantage of the "5th cycle" but still limit the E/O to 3-4* for driveability.

More like a 231/247 115+5.

But if you work with Mamo and give him all the vehicle details, how you plan to use it, and what characteristics you want and he'll dial it in for you.

[streetk14]

With the long tubes, but 2.5" exhaust and your compression ratio, and the MAMO heads, I'd:

• Bring the IVC earlier
• Increase the exhaust duration
• Allow slightly more overlap to take advantage of the "5th cycle" but still limit the E/O to 3-4* for driveability.

More like a 231/247 115+5.

But if you work with Mamo and give him all the vehicle details, how you plan to use it, and what characteristics you want and he'll dial it in for you.

Yeah, that was one of Mamo’s cams but on a 116 instead of a 115. I’m actually not totally sure on the advance. He was recommending a 115+3, but I’m not sure if that’ll change with the 116. I think we were shooting for 11.4 on the compression. I’m just paranoid about overlap and light throttle drivability, though I’m sure there’s more to it than that. Tony claims his heads really help bigger cams drive better, and the port velocity thing makes sense. I’ll likely do 3” exhaust at some point as I’m sure the 2.5” is costing some power.

What exactly do you mean by limiting the exhaust opening (E/O) to 3-4 degrees for drivability? That’s a new one to me.

[Zachalanche]

I’m not an expert, but assuming those specs are correct, that’s a big ass cam. As was mentioned, it should be making peak power way higher in the rpm range. Maybe you have a valve control issue or something? My mild cam LS7 makes peak power around 6500 and carries well to 7000. That’s with a little (for a 427) 227/242 116 cam and 2.5” exhaust.

A dyno is a dyno so you have to take baseline numbers with a grain of salt, but my crate engine is rated at 570 hp from GM with Z28 exhaust manifolds. I have long tubes and a ported MSD manifold with a 103 TB. Made 520 whp through a T56 Magnum and 3.89 geared 9”.

That engine must be making more than advertised. or the dyno is being generous. the 9" alone should eat up more than 50 ponies, and if it doesn't, what sorcery is inside of it?