Define..."act bad"..! Like the old 327/365 HP bad? 289/271HP bad ? Its all relative. IF its a standard shift it ain't "bad" like an A/T 6sally6
Like the average guy who buys a cam and can't make it run as smooth as the stock one and wonders why the manifold vacuum isn't as high as the stock cam, or can't understand why he needs to re curve the distributor, kind of bad.
Good video thanks. I like bad, however a guy needs to understand what a particular cam will and will not do. Need to match cam to engine components, transmission and stall speed for auto and rear gears and weight etc etc. A good cam grinder will get you what you want with good data. A lot of engines are over cammed for sure. If you have a cam that doesn’t start making power until 2500 rpm with auto stall speed of 1800 2.70 something rear gears and 4000 lbs the car will be an absolute dog. Probably ok once it’s wound up and going but getting it to go will be painfully slow. Dan
Kind of like watching the old "dry eyes" commercials. In my teens I fell victim to mismatched components by ordering the biggest cam with stock valve springs and wondering why it didn't work...lol Nowadays I have two street driven vehicles with cams well into the 600's and have no issues.
Some of this is really to start a discussion of how the the engine is affected by larger cams and what needs to be to happen to the tune-up to make a larger cam work. It seems that some of the tuning skills have gone missing today.
If looking for a reasonable docile street engine perhaps one should look at what the factory did and did very very well when building performance engines. Even the most powerful SBC as well as BBC for Chevrolet and FOMOCO had to be able to sell cars out of the showroom. On Saturdays I can hear stock 375 hp 327 FI Corvettes and they are barely audible to some jacked up .650” lift roller cam tunnel ram rattler coming by. It seems every BBC “sound alikes” are nothing like there bretheran SS 396” or 427” 425 hp which really have a nice note and have vacuum power assist that still work fine. One needs to think….or supply ear plugs.
It doesn't cost much more to buy a cam that is probably too big for a particular application. "So buy the big one"
It's nice that some cam companies list low and high rpm numbers that show where the cam runs most efficiently but the same cam will raise these numbers in a small cubic inch engine v/s lowering these numbers in stroked big inch engine. Found this chart a few years ago and always research it before buying a new cam
I use a flat tappet cam in one of my big block Mopars that has 276/282 duration @ 050 and the only thing I can bad about it is fuel mileage. 500 to 600 tq from 2800 - 6500 rpm.
For a street engine ! It is always better to put a small cam in a big engine, than putting a big cam in a small engine !!!
For the guy look'in for the bad-ass idle FIRST and performance and longivity Second.. he should check the cam numbers recommended for dirt-track engines. They need big power QUICK to come out of the turns...get to max RPM (which might be 6000 RPMor so) and idle like a 1/3 of the spark plug wires are OFF ! = tight LSA numbers ISKY cams are big on the tight LSA theory (cams normally ground on 108* LSA) They've been around a LONG time ! Automatic trannys need a lot more home work than stick. (S'why most hotrodders run a stick !) Just bumping up the LIFT ain't necessarily the answer either. (need springs/retainers/keepers/rockers etc) 6sally6
The cam we used in our bracket BBC was .680/.714 lift with 278/282 duration @ .050 and the strongest power band was 4500-7500. Launched at 4800 and shifted at 5500. All 820hp was in by 6100. 505ci (427 tall deck, 1/4" stroker, .100 over)
5.0 +.30 ..... 9.5:1 CR Duration @050 230/236 108*LSA Starts really pulling around 1500RPM By 5000 RPM it's taking my breath away ! (Seriously!) 6sally6
I've always liked this discussion. Everybody wants the chop, nobody wants to tune for it or deal with the quirks that come with a big cam on the street. I whooped a lot of nasty sounding cars back in the old street racing days that certainly sounded the part, but coughed and sputtered off the line, poured black smoke under WOT, and just would never act right. Not that I don't have a decent sized cam in my 55, but it's tuned for it, or at least as well as I can tune it. I'm running a Comp XR294 HR on a 10.5:1 350 with a 750 VS Holley Carb in an engine that I shift at 6500rpm with a 3.70 gear. I need more converter to really make this car quicker (I have a 2k unit now), but what I have keeps it nice on the street. It's pretty tame off the line so I can get out of the hole without a ton of drama, but once it hits 3500rpm it's gone. Through tuning I was able to remove the tendency to push against the converter at a light and still keep it idling fairly crisp. It does stink up the joint, but there's not a ton I've been able to do there. My one real sacrifice is the timing curve. I have to use 2 heavy springs to keep it from pinging. I've tried all the tricks like limiting vacuum advance, but could never cure the part throttle ping under a load. In hindsight, I would have chosen less cam were I to build this motor again, but it's been a great lesson in tuning for what you have. My OT Camaro on the other hand has a pretty mild cam and a 3k stall, and it's so much more fun to cruise on the street. It's all torque. It's a 408 with EFI, so all of that helps too. While it's noticeably stronger in the low and mid range, it falls flat on its face at 5k rpm. My 55 is still pulling hard when this engine is out of breath. It's also a heavier car with a bit less gear (3.42). I've always felt that you pick your cam for how you want your engine to make power, then build around it. A lot of guys pick their cam last, and wonder why their engine won't act right.
Nice write up. 3k stall would help tremendously. 242-248 @ .050 is a sizeable street cam. At least you took the time to get it to a driveable state.
Have you tried retarding the CAM TIMING(not ignition timing) just a few degrees ? You DO run 93 octane hi-test fuel....right?! With an A/T there is just so much you can do with a "big-Boy" cam and CR on the skreet. Using a big load of initial timing to crisp up the idle and a limiter to control the total timing and then deal with the car wanting to'creep' at a traffic light.... Alotta balls-in-the-air to juggle to make it happy on the street. Would 'kicking-it-outta-gear at a stop light make it more liveable on the street ? (Just a bunch of questions floating in this big old empty nogg'in) 6sally6
Lotta young rodders first thing I do is tell them to throw away their speed catalogs. They make boomer hot rodder jokes non stop yet do the same cliche trailer park boomer rodder things. And think EVERYTHING has to be brand new. I have a younger buddy with a 77 nova that keeps falling into that trap. Was talking about how just getting a 454 running in the car was going to be over $4k with the engine itself costing $500. On his list included a hairy cam, brand new Edelbrock intake, 950 dominator, pop up pistons etc. Keep in mind this is a street car. And he's used to a cobbled 350 with a high stall converter and 3.73s. By the time I was done picking at his list the tally total was down to $1200....
Cam is installed straight up, which if I recall correctly (it's been 17 years this engine has been going strong), Comp builds in a few degrees at straight up. This car has never seen anything but 93 octane. I've tried some Torco in it which didn't seem to make much difference. Initial timing is currently 15 degrees. I've tried up to 18, but it begins to kick back at that level. I tried the advance limiter. It helps, but doesn't cure. For the ping to go away, I have to basically stop the vacuum arm from moving at all. The ping was never too bad, the engine would still pull hard through it, but it was there. 2 heavy springs and no limiter on the vacuum advance seems to be what it likes to not ping. Part throttle power and response didn't change much when i went from 1 light and 1 medium spring to the 2 heavies. It's to the point that I'm good with where it is and I don't feel like fiddling with it anymore. I'm sure an expert could clean it up and find a few horsepower, but I am proud of how it runs and being able to say nobody else has touched the tune. Throwing it in neutral cleans the idle up at a light, but it's not bad in gear. Neutral idle is 950-1000rpm, and I get 750-800rpm in gear, and I'm not mad at that. It's rich at idle no matter what I do though. I've always had a mild stumble off idle that I've been able to make a lot better than it used to be, but have never been able to totally eliminate it. It's most only when I wing the throttle from idle in park, in gear it seems to pull through it. If I rev it repeatedly without letting it settle back to idle, it's perfect. I'm not mad about where it is, it drives nice and has pretty decent street manners. It chops hard at a light and I dig it. At some point I'll upgrade the converter and I'm willing to bet that will cure what ills are left. MY only real beef with it is stinking like exhaust after I get out of it, but tailpipes would surely help with that.
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