I was bored while the internet was down from all the storms and wind, so came up with a little analysis using the desktop dyno simulator. The comparisons were made as fair as possible using the same components other than tweaking the static compression ratio to make it a closer match on the dynamic compression. So here it is, more entertainment/drivel from Gary. Buick 350 engine specs: Bore: 3.83 Stroke: 3.85 CID: 355 Intake valve: 1.875 Exhaust valve: 1.550 Intake flow: 215/215/215 CFM @.350/.400/.450 lift Exhaust flow: 144/146/147 CFM @.350/.400/.450 lift Induction: 750 CFM dual plane intake Headers: 1 3/4” primary, 3” collector Federal Mogul cs647 (asymmetric lobes) LSA: 114.25*@.006 / 112.75*@.050 / 113.5* 'average' Center line: 116*/112.5* @.006 / 109.5*/116* @.050 I/E Indexing: 1.75* retard @.006 / 3.25* advance @.050 Duration 189*/208* @.050 / 270*/293* @.006 I/E Peak lobe lift: .2433/.2533 I/E Peak valve lift: .3771/.3926 I/E @1.55 rocker arm ratio Average ramp intensity: 1.94 Intake Valve Closing @.006: 71* Compression ratio: 10:1 static / 7.58:1 dynamic Averaged power output between .006 and .050 lift Torque: 426 ft. lbs. @2750 RPM peak 413 ft. lbs. @2000 RPM 411 average between 2000-4000 RPM HP: 322 @4750 RPM peak 308 average between 4000-5500 RPM Crower level 3 (symmetric lobes) LSA: 112* @.050/.006 Center line: 108*/116* I/E Indexing: 4* advance @.050/.006 Duration 210*/220* @.050 / 276*/281* @.006 I/E Peak lobe lift: .288/.302 I/E Peak valve lift: .4464/.4681 I/E @1.55 rocker arm ratio Average ramp intensity: 2.33 Intake Valve Closing @.006: 66* Compression ratio: 9.5:1 static / 7.52:1 dynamic Averaged power output between .006 and .050 lift Torque: 426 ft. lbs. @3000 RPM peak 409 ft. lbs. @2000 RPM 414 average between 2000-4000 RPM HP: 330 @4750 RPM peak 318 average between 4000-5500 RPM GF Custom Cam (symmetric lobes) LSA: 112* @.050/.006 Center line: 112*/112* I/E Indexing: 0* advance/retard @.050/.006 Duration 202*/214* @.050 / 268*/276* @.006 I/E Peak lobe lift: .302/.298 I/E Peak valve lift: .4681/.4619 I/E @1.55 rocker arm ratio Average ramp intensity: 2.37 Intake Valve Closing @.006: 66* Compression ratio: 9.5:1 static / 7.52:1 dynamic Averaged power output between .006 and .050 lift Torque: 434 ft. lbs. @3000 RPM peak 418 ft. lbs. @2000 RPM 421 average between 2000-4000 RPM HP: 333 @4750 RPM peak 319 average between 4000-5500 RPM
What happens if you dial in a 104-106* LSA and a +4 installed position? And then bump the durations a bit to see how high you might push the curve, even if unrealistic profile. Asking for a friend. (just kidding!) More or less seeing where it might fool the computer. Also, what does it do when you push 225-245 cfm?
All that stuff adds more power, obviously. Just wanted to show how smaller cams don't really change a whole lot when RPMs are kept low due to flow restrictions. In short, use whatever cam tickles your fancy, and for whatever behavior characteristics you desire. Don't get too obsessed with the numbers, but rather look at the patterns. You'd never feel much difference in 8 or 10 hp on a street car anyway. Weather changes can make more of a difference than that. Most of the time when people do cam swaps, they see a substantial difference in performance in their otherwise 'stock' engine, mainly because the earlier IVC on aftermarket cams boosts dynamic compression. This alone will improve power noticeably, regardless of cam specs, and explains why the 'stock' cams on the newer 350s, coupled with choked off induction and exhaust, gave a poor impression. Example: if I were to have left the static compression the exact same (as would be typically seen on a 'cam swap' in the same air flow environment), there would have been a greater difference between the Federal Mogul cs647 cam and the others, due to much better dynamic compression they have with their earlier IVC points. Alternatively, you could make the IVC later or similar, but have longer durations and greater lift, better air flow from heads, induction, and exhaust, rev it higher, and effective compression gets boosted this way due to overlap and scavenging. Either move more air or make better use of the air it uses already. Either way will see improvements. We all know more squeeze = more power, as was seen by a forum member's car that used the TA 212-350 cam in an all-iron engine with no head porting, using proper gearing and traction control, got his car into the 12's. There's 455's that aren't that fast. Anyway, I was bored. Maybe this will provide some sort of reference point for someone.
I don't look at the numbers closely on the sims either, I watch the shape of the torque curve. Definitely not to be argumentative, more to show what happens to the shape of that curve with those cam examples. What I see with every engine type tried is that the idle gets raspy, then they wake up huge right off idle, before the converter flash. Quite abruptly in fact. That 10-15 hp down at 2000 rpm is 25-40 lbs tq., which is certainly detectable on the butt dyno. That strategy cam cuts the hp off at the peak, it drops quickly. There isn't enough duration for the overlap to hurt anything (except idle). Wakes up a low compression engine nicely.
Using the same engine stats above for N/A Federal Mogul cs647 and 10 PSI of boost, showed 525ish ft. lbs. and 475ish hp. Race fuel would be required. Of course, boost on any engine is going to transform it. This is just using the stats above--power figures could be improved even more using this "OEM" cam, and even more with a more powerful cam.
I made a cam similar to the one you're describing, and posted results here somewhere, but it's been a while and who knows where the thread is. lol I'm home now and business is done for now, so I'm going to wind down before retiring to bed...and what better way to do this than to fiddle around in the dyno simulator again? Interestingly enough, the Melling sbc-11 (the smaller of the two cams Melling makes for the Buick 350) uses a 105* LSA and produces some stupid low RPM torque for a tiny cam.
Here's one for schiznitz n giggles... Took that puny Melling sbc-11 cam (tiniest 'stock' cam made for the Buick 350), 'converted' it to a roller version using same indexing calculations as original, pumped it up to Schwarzenegger status with .600 lift on both intake and exhaust, bumped static compression to 12.5:1 and used the exact same heads as the above comparison (same valve sizes and flow numbers @lifts), added a 1000 CFM induction dual plane, bored and stroked to 373 CID, and it showed 509.5 ft. lbs. @2250 RPM (lol) and 327 hp @4500 RPM N/A.
An interesting thing I'd like to question but not be construed as negativity is the severe lobe action with the engine choked by the cam events (duration). The sim is showing strong signs of the cam severely restricting the engine by keeping the torque peak so far below the intake port's natural torque peak. Being that such a cam might be really expensive and impractical for cost/hp...I'd play with increasing duration to lessen the severity of the lobe. There are bound to be shelf cams that would all but match the output down low, as well as extend the range. Your tq peak might be at higher rpm, but the curve won't suffer noticeably below that, maybe trim a tad bit from the peak and hang on much longer. Whether it's opening the valve sooner or faster to the point in which the induction loses the pressure differential that keeps pulling it in doesn't really matter. I know it goes against every philosophy in the mild cam near-stock world...but here's where killing off low lift flow and adding earlier intake opening helps in a street driven deal. You can have your big cam and eat it too. I know it's a 'just for fun' thing.
So far this isn't a 3 dog night. Good thing you were playing with more than Onnnne isss theeee lonlieeest nummmberr that.... (sorry, had to!)
We see mixed messages on this here on the forum. Crower claims 4* built in, Steve Caruso says he's found Crower's cams to be pretty accurate, others have found them to be about 1* off from advertised, and still others appear to remain confused as to what 'built in' or 'ground in' on cam indexing actually means. In the end, none of this matters so much because you should degree ALL aftermarket cams for peace of mind on where your specs are, unless you want to roll the dice and build your engine with very generous tolerances on detonation and fuel requirements, using whatever grade the engine happens to end up needing, erring on the conservative side (figuring a 2*-3* error in either direction on retard/advance, which 'serious' engine builders would feel uncomfortable doing, and indeed, advise against). If the 'dice roll' method is used, I'd suggest building the engine with around 8.5-9:1 static or a 'medium octane' goal, so if the compression happens to be off and/or the cam indexing is more than a couple degrees advance or retard, you might end up getting away with regular gas or needing premium. Otherwise, index it or use OEM replacement (which doesn't need it).
I'm not keeping score here and (don't) give a rat's ass how many participate in this 'boredom' thread. lol There's more important points of interest to contend with that may inadvertently help someone reading this (out of boredom, or whatever reason). You know how things can spring up out of nowhere here on this forum, so who knows!
This severe lobe action is permissible on a roller cam which can accommodate it (even though the example I used didn't have ramp intensities that were unusual for such a high lift and small duration), and was only given to show an example of a 'theoretical potential' (as you well know). I don't take it as negativity, but as valuable input on ideas, which I of course will always welcome, especially from you. The fact that you respond at all to my posts/threads is a compliment to me. We both enjoy stimulating dialog. The Buick 350 has a natural tendency to want to rev higher, and these tiny cams purposefully restrict it for other reasons envisioned by the engineers, and is by no means a demonstration of 'ideal' operation. It can be fun seeing what will do what, testing limitations and restrictions, and pushing the limits on both ends of the spectrum. The dyno sim may not be spot-on accurate, but is hella cheaper than the vast ocean of funds needed for thousands of engines/scenarios/dyno runs/track testing and is 'close enough' to show patterns and guide in desired directions. The math is 'spot-on' in an 'on paper' world, but would not reflect variances in a real world environment--but that's where we come in with our 'guesses', based on other empirical data from actual real world dyno runs, track testing, experience and theoretical/philosophical ideas. I've always said I like to take it all into consideration as a reckoning--good, bad, ugly, and beautiful (subjectively and objectively). All that said, I have tinkered with what you suggest here (and see where this is going with the upcoming aluminum heads), where high flow/lift heads coupled with a high lift roller cam that has restricted duration will in fact take a huge gulp of air at lower RPMs with massive dynamic displacement (even more so on stroked engines), with smaller tube primaries to help with lower RPM scavenging. I'm seeing potentials with such an engine in the 2000-5000 RPM range that demonstrates big block torque. It does this by maximizing the energy present in the limited air/fuel capable of flowing through 353 (.020 over) to 373 (.060 over, 3.99 stroke) engines. The more displacement and longer the stroke, the easier this becomes. This is not just a fantasy, it is a reality (albeit still 'on paper'), working out the kinks before putting wrenches to metal. Of course, it would be easier to simply build a 355 and rev it.
Another point of interest, I've noticed the sim seems to favor any cam that uses less advance--closer to 'straight up' or slightly retarded seems to yield the best results (depending on other parameters), so I try to design indexing calculations around this. One might want to install the cam slightly advanced despite this finding, since the timing chain is going to loosen up as it wears in, and will in fact stretch/flex as the engine revs, which gives a natural retard timing as all this happens. There's a lot going on inside these engines! Having said all this, the Crower level 3 cam shows more power when installed straight up or 2* retard (as Steve has his now, last I heard), and if you built the engine around this with an ideal DCR in mind, will show more power than the above example. The better the engine breathes, the more gains you'll see out of these tweaks, since the engine 'wants' to rev and the higher you take it (along with proper componentry) the more power you're going to make because you're moving more air. Zero in on making this extra air/fuel as efficient as possible, and you'll squeeze even more out of it.
Dialing in straight or retarded should mostly show gains at or past the power peak anyways, that extends breathing somewhat. If camming short, I'd be looking at tq below peak and trying to find the +20 jumps...and let better induction flow allow the hp to pass. Coming from the mindset that +12 CFM would allow +20hp and that you'd see gains everywhere, rather than have the cam trade cylinder pressure from one part of the range to the other (hurting the bottom end). I think some programs miss a certain amount of scavenging, so we only see the filling and trapping part. Even the Nascar header makers had to trial & error them to get where they are, and now having seen universal trends from that development, incorporated smaller-faster exhaust valves and ports to the system. If you think about it, those use fairly heavy overlap breathing (relative) and still rev high, with increased emphasis on the intake side. For the mild stuff, some fairly well knowns have had success using intake favored cam profiles with the premise that the exhaust does most of it's blowing down in the early part of the lift cycle. The purpose of the tail end of that being to pull on the intake side. It's your sim. You are the engineer. You get to determine whatever you want and answer to no historical diatribe or any factory reasonings.
I believe Steve sets his cam at 116 . But he would have to confirm that. But in other good news, I heard the pure stock 69 skylark is hitting 12.5 with the 212 cam . They found some more power in that pup.
Sounds like you are referring to drag racing in which the engine is held past peak hp for advantage...makes sense. (sarcastic eye-roll for humor purposes) Keep in mind that Gary is simulating these for street and part throttle/lower rpm use. I'm not going to draw comparisons between what this forum's community is doing to what Nascar or Prostock did to get where they got, it's just for discussion's sake.
