I'm still trying to figure out what a Chevy lobe is, and a Mopar lobe is. Ford lobe anyone? Specifically, where's a diffinitive chart, or data....something credible.... that shows duration at .200", .050", etc...
and lift of said lobe that shows when the lobe becomes either that dreaded god awful Chevy lobe or the awesome almighty Mopar lobe? Seriously, the Chevy lobe nonsense is tiresome. Slow ramp lobe up to very fast and everything in between. Choose your specs accordingly.
OH! That’s easy.
The MoPars as we know use a .904 litter, the Fords are smaller, the Chevies are smallest. The bigger the lifter diameter, the larger and /or quicker rising ramp cam you can use.
Typical cams are ground with the smallest lifter because it makes it easy for the cam company to just slide in the cam core, press a few buttons, walk away and presto, a cam is made.
Generally, you will ya e an increase in performance. There is no doubt. But if your a small lifter engine, (Chevy) and your looking to make serious power at the track, you enlarge your lifter bore to install a cam that will allow more valve lift quicker from the base circle to max lift.
The more aggressive the lift rate at the valve the quicker you can move in more air and fuel for a bigger bang.(HP)
There is a limit to how fast the valve can be opened and still see a power return. It is different for each engine combo. So there really is no way to know unless you have been there and done that on YOUR engine or you have done it ten million times.
MoPars have this big lifter diameter as stock. This allows the ability to take advantage of what is there and not modify anything to do it ether. This is why Wyrmrider always suggests this for any cam change from a 10hp hop up to the sky’s limit.
The more aggressive cam you can install ends up as more HP & TQ. Free power by taking advantage of what is already there waiting.
IS a Chevy lobe bad? No.
Are you leaving power on the table? Yes
How much power is being left behind? That is a variable left to the been there and done that for THERE engine. Not to mention the exact nature of the build!
Is it worth it? Yes, to a degree. It depends on the engines owner.
I haven’t found it worth chasing for mild builds.
I do have a big solid cam from Ultradyn listed as “For the Mopar .904 lifter ONLY.” Because the “Other guys” have smaller lifter diameters. It is a race cam. NOT a street cam @ 272@.050.
There isn’t a Definitive chart per say. But in a cam book, IF they list the lifts of the cams ramp at various lift points, you can see how the cam lifts the valve quicker than another. This shows there “Rate of Lift” by the raw numbers on the cam. Then multiply by your rocker ratio to find the theoretical lift.
What you will find is so small but also having an effect that once again, shows itself better and better as the engine build gets more radical.
Also, I am also tired of the same post by Wyrmrider of what he thinks you need, Chevy lobe, inverse lobe, Slow rise bullshit for the average guys ride. But solider on he will I suppose.
IMO, for the average street guy with the grocery getter, mild hot rod, light to light fun with his buddies, it’s ridiculous to chase the extra free power that only a dyno will show. And only a dyno will show it.
Remember, the more aggressive the cam lobe, the quicker you wear out your valve springs. The more aggressive your build, the quicker they will wear out.
1 last thing, the big company advertised “Use our cam because it takes advantage of your lifter best” is a big bowl of burnt bullshit served in Luke gravy. But sell they do and the complaining of there “MoPar fast rate ramp cams is seen here ALL the time.
The duration spread has more to do with the valves and ports in the engine and little to do with RPM range or being EFI or carb.
I’ll also include that the split pattern cam spread that seems to vary from article to article is ether just there choice of what they think will do well OR someone actually scientifically did some math on the balance between the intakes and exhaust port flow rates and adjusted the cams duration specs (and possibly other parameters of the cam lobes) to suite THAT PARTICULAR engine for what they want THAT engine to do, Specifically!
