FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: 427HISS on August 22, 2018, 04:34:50 PM
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Where does the lobe seperation come into play, when you're figuring out other specs of the intended use of the engine, valve train, etc,
when building a camshaft ?
What makes the differences between a solid flat tappet, hyd roller and solid roller ?
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You can read volumes just on LSA. It impacts overlap and intake closing point so it does quite a bit to cam behavior.
You can't even get a consensus from the well known cam grinders. One guy will say he plots the lobe timing to optimize blowdown and still trap compression and LSA is what it is once he's plotted the lobes (a bit of a generalization there). Another guy will take intake to exhaust ratio, rod length, head runner volume to cubic inch ratio, and head flow to cubic inches all into play and use that info to influence LSA. Vizard has his 128 "rule" that he uses to calculate it, but that's geared more from experience on one specific platform (the SBC) than a proven formula, IMO.
I think at the macro level, you'd want to consider need for power brakes as the LSA influences overlap and therefore vacuum. Then you get into idle quality and "snottiness" if that's a concern, along with playing nice with a tight convertor if a guy were running an auto.
speedtalk.com forums have some good info, but you'll wade through a lot of bickering amongst builders....and like I said you'll end up with viewpoints 180* from each other, both coming from what seem to be fairly well respected guys so it's hard to distill what's what. But you will definitely learn from reading.
Further muddying the waters....trend seems to be to tighter LSAs for carbed combos and power keeps increasing as obviously cylinder head tech gets better. On the flipside, the latemodel stuff making huge power on EFI generally has wide LSA.
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As chilly pointed out, it (along with duration) controls the amount of overlap.
There will be infinite iterations for how much overlap an engine should have, depending on the cylinder heads, rpm, displacement, application, and about 87000 other parameters.
I would watch about drawing a line between carburetors and EFI though. My last pulling truck engine had two 1450 Dominator carbs on it and used a 119 LSA. It sees 8500-9000 rpm on a pull. Contrast to that, you could have a small engine with a very low rpm goal, with not much overlap at all.....it could be that you could run a 107-108 LSA, even with EFI on it, because the overlap would be so low.
When I sit down and figure out what a cam should be, I look at duration first. Duration controls where the horsepower peaks and where the hp/torque curves lie. That is based on displacement, cylinder head flow (head flow is BIG component), and a few other things. Advertised duration vs. .050" duration (along with the .200" duration) will tell you how aggressive/lazy of a lobe it is, which will determine whether or not the cam will be a spring eater, whether it will be easy on parts, whether it will be noisy, quiet, etc. Lift is based on where the heads flow the best, along with a few other tricks. The intake centerline is based on how much cylinder pressure you need and how efficient the engine will be. Lots of guys put a big emphasis on an advanced cam not pulling high, or a retarded cam not having bottom end, but I haven't seen a lot of direct relationships like that. I do know that advanced cam timing on a street engine makes them pull very hard on the carburetor. LSA focuses on overlap, how much vacuum you need, what rpms you're turning, and how you want the hp/torque curves to play out.
As chilly also said, you could write books on this topic. There are a couple of generalities that you can make, but they are few and far between. To me, there are no universal cams and each engine will demand a specific recipe. My biggest gripe is looking through a cam catalog and seeing the EXACT same cam specs for EVERY SINGLE ENGINE FAMILY in the catalog. I know it's easy for a cam grinder to make a nice lobe and then duplicate it for different engines, but if they think a Tunnel Port FE wants the same cam as a SBC, they're not doing their due diligence as a grinder.
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Brent, thanks, I got a bit too "general" in there. This may be old information by now but I know Pro Stock stuff at one point had gone wide LSA, explained to me is that they'd gotten to a point with duration being so long they needed to reduce overlap. Regardless of exact reason, it just goes to show that LSA should always be tuned to the combo.
I'm trying to understand cam design beyond the simpler concepts of knowing effects of duration/lift/overlap. Seems LSA is a pretty hot topic and is treated as one of the "black boxes" where some power cam really be made if done right. Problem is for normal dudes, it's fairly complex and definitely expensive to go playing with different cam grinds to test theories. That's why the small cost involved in having a builder, that at least has some directional trends and experience to call on, have a cam ground is the most well spent $$$ that can be spent IMO.
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I like Brent's summary and as he shows, all the valve events matter and they are based on many components and desired use
I especially don't like LSA as a stand alone number. If I was forced to pick specific numbers, I would say intake lobe open/close/lift first and exhaust lobe and overlap second. It would end up with an LSA, but without those, the LSA doesn't define anything
That being said, my EFI 489 is at 110 LSA :) my carbed 445 was at 112 and my carbed 390 is at 112. :)
My 462 for the F100 may even go 114, we'll see, but man I like the sound of a little overlap
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If one engine and the specs are all exactly the same, how can the LSA affect the engine, say from 106 to 115 ?
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Hypothetical question: Trying to find the most torque and horsepower over a 3000 rpm band from 3500-6500 rpm, what do you think the camshaft specifications should be?
Engine: 375 cubic inches
stroke 4.000
bore 3.860"
rod 6.300"
Compresion 13:1
head flow 290/205
1 5/8" step to 1 3/4" four into one into 3" collector headers.
wet sump
tunnel ram/2-650s
Going to dyno very soon to verify my camshaft selection, but interested in ideas of those who consider themselves gurus. Joe-JDC
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I’m no guru but I’ll throw in ideas.
For power in that specific range, I’d say a 6000rpm hp peak and 4500tq peak would be about right, on a 375 with decent heads I’d say that’s a around a 238* intake lobe with a solid roller. Engine has an intake bias with tunnel ram and intake port flow, plus headers that may be a bit small on the topend but probably very good for overall curve. The high compression should help the exhaust side as the faster expansion should get the exhaust side moving when the valve cracks open. I’d say 242* exhaust. 6 or 8* split could be argued but that’s what every shelf cam has so I can’t do it.
LSA I’d say 108*, the good intake doesn’t need much overlap to get it moving, and with 13:1 it’s not essential to trap cylinder pressure. I could easily be talked into 106 though
Lift, no idea with head flow figures but typical small block heads with those flow numbers I’d say .650 gross intake, .625 on exhaust.
Interesting to see how far off I am...or if reasoning is sound. Guessing this could be a 550hp/525tq combo pretty easily
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Hypothetical question: Trying to find the most torque and horsepower over a 3000 rpm band from 3500-6500 rpm, what do you think the camshaft specifications should be?
Engine: 375 cubic inches
stroke 4.000
bore 3.860"
rod 6.300"
Compresion 13:1
head flow 290/205
1 5/8" step to 1 3/4" four into one into 3" collector headers.
wet sump
tunnel ram/2-650s
Going to dyno very soon to verify my camshaft selection, but interested in ideas of those who consider themselves gurus. Joe-JDC
Need to know peak flow lift and also port volume. Also need to know type of cam you need....hyd roller, solid flat tappet, etc.
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Lift, no idea with head flow figures but typical small block heads with those flow numbers I’d say .650 gross intake, .625 on exhaust.
My guess is that it's not a small block....is it a Y-block, Joe?
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The more I study this stuff the more I become a stab and try sort of guy. And I have stabbed a lot of cams into reasonably similar combinations....sometimes walking away feeling like I know even less than I did going into the effort. Damn motors cannot read and sometimes they just like what they like, no matter how hard we try to force them to like "something new"...
That noted, I bet JDC will have damn near no duration, a startlingly tight lobe separation, and it will be installed so advanced it'd scare most anybody. Seems I have gone that direction until it makes so much running cylinder pressure through torque peak that you think it'll rip the heads off the top and push the crank through the pan at the same time... Of course I had been running limited octane and was always listening for the sounds of impending doom, which never happened. Means I was not trying hard enough...
Of course he will probably win with a cam that looks like it would work in an 812 inch Pro Mod and make everything I said look silly....cuz motors cannot read....
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Lift, no idea with head flow figures but typical small block heads with those flow numbers I’d say .650 gross intake, .625 on exhaust.
My guess is that it's not a small block....is it a Y-block, Joe?
Jesus, just saw 375ci and tunnel ram and assumed....didn't even look at the bore/stroke that early in the AM. Fail.
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No guru here, especially with a combo like that
Don't know end use but thinking its an EMC with the unreasonably wide desired range for a small cid motor
My WAG for a solid roller, mid 250s intake lobe, a real fast ramp, a little more on the exhaust side, lift in the mid 600s or more if the heads support, 106-ish LSA. Sort of short oval track kind of motor, but I am with Barry though, that would be a stab and try
EDITED for bore and stroke foolishness.....beans above the franks had me crossways :) didn't change my recommendation
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No guru here, especially with a combo like that, BTW, just to be anal, it's 388 cubes no? or was the bore and stroke a typo?
Don't know end use but thinking its an EMC with the unreasonably wide desired range for a small cid motor
My WAG for a solid roller, mid 250s intake lobe, a real fast ramp, a little more on the exhaust side, lift in the mid 600s or more if the heads support, 106-ish LSA. Sort of short oval track kind of motor, but I am with Barry though, that would be a stab and try
I'd say it's not a typo. Could be a completely wrong guess, but with Joe's history, I'd say it's a stroked 312.
If it is an EMC engine, that's not a lot of rpm for a tunnel ram, and I'm along the same lines as Barry......it wouldn't surprise me to see this engine needing something like a 104 LSA, installed on a 98-100° ICL, with as much lift as you can reasonably fit with the valvetrain.
Curious to see the answers to my questions.....I'm eager to take a stab at it and may even float Joe a camshaft to try.
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No guru here, especially with a combo like that, BTW, just to be anal, it's 388 cubes no? or was the bore and stroke a typo?
I think you flip flopped the bore/stroke...
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LOL good catch Chilly, I did :)
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Heads flow just over 305 peak, and 230 on exhaust with header tube, it is a Y Block nearing completion. I am an alternate in this year's EMC. I am undecided whether to run 4V or tunnel ram, but in my experience, the tunnel ram always makes more torque and power. I would definitely cam it different for a drag race engine. Joe-JDC
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Joe, at what lift?
Are you running a solid flat tappet with mushrooms?
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I hope you get in Joe !! Sounds like a fun project , love the Tunnel Ram and good Luck !!
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Joe,
I have done some stuff for Engine Masters competitors for years. One of the first criteria is the test parameters. If the testing stops at 7,000 rpm you obviously don't need to make more power beyond that. Cams for EM competitors have become extreme to the point where some are not practical for actual street use! Next obviously is the engine cylinder hears being used. I totally agree with Brent that there isn't 1 cam design that works for all. Certain cylinder heads need "crutch cams" to make up for flow deficiencies on one side or the other. Some go for short duration and super high lift . I know competitors that have tried 15 cams before picking "the" one to use. Obviously the best overall combination of cubic inches plus HP and TQ will be the winner. Changing LSA and cam advance affect HP and IMHO more importantly "where and how much" TQ is made. The flow balance of your head would favor a longer exhaust duration and "might " like less exhaust lift. "I" have found some cylinder heads favor a particular LSA and I simply play with duration and lift and other that don't seem to care.
Randy
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When I was in my late teens my friends and I befriended a gentleman named Owen Bowling. He owned Owen's cams in downtown Los Angeles. If you brought him a usable core he'd regrind it for $30. He'd also regrind your lifters for $20 extra.
His favorite grind to give a young fella if you just wanted to put a "hot" cam in a stock engine with a stock torque converter was the 68I which was the stock intake lobe of a 440 Magnum MoPar. The specs were (with a 1.5 rocker ratio) .450 lift and 268 advertised duration. He would grind it at 111 centers unless you asked for something else. I used several of these grinds in small block Fords (1.6 ratio made them 480 lift) and they worked fine. He also ground some more "aggressive" cams for me that I later found to like better at 108 centers, but that's a discussion for another day.
Back to the 68I camshaft. Around 1985 I became the sencond owner of a 1970 Torino GT with a 429CJ and an automatic trans. The original owner bought the car new at legendary Foulger Ford and was "dyno tuned" by performance director Randy Ritchie. It had a Holley spread bore 800 double pumper and other performance "tweaks" before delivery. The original owner drove it that way for 90,000 miles before I bought it.
I drove it that way for a few months and always thought it should have more giddy-up off the line. Long-story-short I installed a 68I on 106 centers (.519 lift in a CJ 429) and it became a tire-fry'n beast! Along with the performance boost came that perfect "big cam" idle that was just right!
Eventually I got him to grind a 68I for an FE (.528 lift in an FE) that was on 100* lobe centers. A pal and I installed it in his 1957 Ford pickup with a pretty stock 390. It idled like it had a REALLY aggressive camshaft! Ran OK but was all done by 4K rpm. It was a science project to see what would happen. Don't need to do it again.
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Stock style lifters are mushroom, and solid flat tappet camshaft. It is a stroked 292 engine since the 292 has smaller crankshaft journals than the 312. I am currently running shaft mounted 1.7 roller rocker arms, and .370/.376" lobe lift for .629/ .639" lift at valve. Joe-JDC
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Can you say where lift was for peak flow?
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Very interesting guys. I love bench racing.
How does head volume, intake and expelling react to LSA ?
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Just received my confirmation that I am in the competition! Run in third place on Monday, Oct. 1. I hope to at least not finish last. LOL It is a strong group of competitors, but the little Y should make Vintage Class and Vintage Fords proud. Three Ys on the venue. Ted Eaton has won this class, so I know he will be ahead of me, but we will be helping each other. Jon Kaase is also in this class, so expect some "out of the box" thinking again.
Probably should move any further mention of this engine to the Non-FE discussion site or Members Projects. Joe-JDC
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I'd be low and mid 250's. Like 252/258. I'd put it on a 110 separation, in at 105. I think the long runners will have lots of mid-range, so no tight centers for me. Real fast rockers on both, like 1.9 intake, 1.8 exhaust. JMO.
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Joe, can you share your choice? or keeping it secret for EMC?
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I don't have "unlimited, deep pockets" to go to unobtanium parts like one participant. LOL. When you are working with 1.43/1.54 rocker arms, and it is hard to find 1.6, much less 1.7 rocker arms for the Y Block, you just work with what you can afford. There is only one source for those, and they are not cheap. Taking a lesson from Jon K back in 2015, his camshaft was made on ~101* LS and installed at 98.5* or so. You hear differing numbers thrown around. I will wait until after the EMC to give specifications on the camshaft. I have a couple of back-up camshafts for dyno testing, but I am hoping I will not need them. I could definitely make more horsepower with a different camshaft, but the average would be less, and that is what is needed to be competitive in EMC. There is another Engine Challenge going on the same week in NC with different rules and different criteria. Joe-JDC
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Joe, I thought the previous years winner wasn't allowed to compete in the same category? You mentioned that Kaase was in the Vintage class, so did they change that rule? Is Royce entered again this year? I also see they moved it to Mentor, Ohio instead of the usual UNOH in Lima. That's a bummer because I always enjoyed taking the day just to see some of the engines since it was only a 20 minute drive for me. Now it would be 3 hours.
Good luck with your entry.
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Yes, Jon is entering another MEL. I thought that the previous year's winner could not compete with the same type engine, either. I questioned the rules committee about that, and never got an answer. Royce is flying in, not a participant. I have been trying to e-mail him, but apparently they aren't getting through to him. My computer/e-mail has been messed up since the hack job earlier. Even Geek Squad cannot fix it. Joe-JDC
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Joe, I wondered what happened you! I thought it was something I said LOL... Glad to see you will be competing!
We need to get this email thing resolved my address is brechlrl@charter.net.
Jon has changed intakes and I think we are running twin dominators this yr. Also a possible cam change. It should be a spirited competition as I see SAM is back with a Poly engine.. They are usually pretty strong.. it will be interesting to see a Studebaker .. Ford products have won this class every year.
I did not enter since I am partners with Jon. My other engines have competed several times and really kind of maxed out.. I expect Joe's entry to be strong..
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Very interesting guys. I love bench racing.
How does head volume, intake and expelling react to LSA ?