...on this cam i've been playing around with for my 427 BBC.

i decided to build the motor as close as i could to what i have now...then modified the cam...and i spent...oh...about 3 or 4 hours playing with this and other settings to get it right.

for what it's worth, according to DD2000 i'd gain 50 ft/lbs (makes 419 ft/lbs with my cam) at 2k and carry a very stout torque curve the whole way...peaking at 586 ft/lbs at 5500rpm with a HP peak of 711 at 7000rpm. Motor makes 600+ hp from just shy of 5500rpm all the way past 9k if you wanted to rev that high. torque is over 500 ft/lbs from a little under 4k to a little over 7k rpms.



i have the DD2000 cam file made up and if you're willing to play around a bit, give me your opinions. I can either upload it to my webspace or send copies to those who are seriously interested in offering opinions and working with me. i'd like some very technical input from those that are well versed in engine building/cams/etc. to offer thoughts & suggestions if you can or would like to donate a few minutes of your time.

Rest of specs used to derive the DD Run above:

427cid
canted/rectangular port heads fully ported (lowest rect port choice in DD2000)
2.19/1.88 valves
12.5:1 compression
850cfm carb
large tube headers open exhaust
solid lifters

single plane manifold

 

hmmm...including the specs would be nice...

these taken from the DD2000 cam math screen directly which is at .050 lift

Lobe Center Angle 118.8
intake centerline 122.5
intake duration 245
exhaust duration 260
intake lift .600
exhaust lift .600

this makes the valve events out to be:

IVO 0.0
IVC 65.0
EVO 65.0
EVC 15.0

-------

and after comparing with other cams...i'm way out of the ballpark on everything but lift. would this work?

 

That's a heck of a power curve. From practical experience, I doubt you will have valve springs that will survive for long in the upper end. I have mainly solid roller-cam experience in bracket cars. Most BBC's make good power and can survive up to about a little under 8,000, like 7200-7800. They can be made to go over that, but parts, mainly valve springs, do not live long. I have no experience with solid lifter cams, but I have to believe they are much less potent at the upper RPM levels due to valve float and lesser cam profile. I shifted my 505" BBC, carburated on gasoline at about 7,200. Cam was only about
.680"/.680" x 270degrees at .050, 110 LSA. It was a "hot boat" cam.

You mention rectangle port heads. Are these the old cast iron LS-7 heads? If so, you can port your brains out but you will never get them to flow like modern aluminum heads. My engine started with these LS7heads and I changed to out of the box-Dart 320's and injected alcohol (over the cast iron LS-7's with Holley 1120 carburated on gasoline and about 10:1 compression/steel rods). I went from 9.40's to 8.70 with the same cam! This was in an altered roadster, about 1700 lbs with driver.

Even later, I changed cams to about .748" x .780" at 286 dgrees at .050, went to aluminum rods and 13:1 cmpression and had the heads ported. I went to high 8.35+'s sec. So air flow is huge in these engines: induction and heads, in addition to the cam. Alcohol was also good for a big portion, maybe half, of the initial gasoline to alcohol improvement of .70 sec's.

My main observation is I think you should expect to keep the engine under 7500 in its power curve, if you expect it to live. The 3-3/4 stroke is very good for fast revs and high RPM's (same stroke as 500" pro-stockers). The latter change valve springs regularly.

BBC's are great fun because you can beat the crap out of them and they hold up, but be cautious with your revs. That is their weak area. I'd start squirming over 7,500.

 

thanks for the response! - and yes, i spent over 3hrs perfecting that curve...making sure it made as much torque as possible while not giving up high RPM power and ensuring the delivery was smooth as silk. it was optimized for the solid lifters i now have. going roller would mean a re-tweak (curve seems to get jumpy in a couple spots) because i am picky, but could be done quickly and does offer a nice boost. i'll definitely be considering that come 496cid time.

the heads are GM cast heads, so you may be right on that. However whoever originally assembled them knew what they were doing. these ports are huge. to port match my Team G intake in some areas i had to remove almost a quarter of an inch, and at least a consistent 1/8" over most of the ports. let me mic those quick...

about 1.8 across and 2.5" tall at the mouth. they are also 2.19/1.88 heads. i have my doubts about making the power shown on the graph, but what really amazed me was the difference between what i came up with and the L88 cam that's in it now. it would be making tons more low end power without hardly sacrificing top end pull. in all actuality, my specs said i shold be making more peak HP then the L88 cam. i wasn't concerned with peak HP though as i was maintaining a broad curve. it might see street duty afterall and will be infront of an automatic.

i also took the time to input the flow charts from 2 sets of AFR heads, the 305 as cast and the 315cc CNC. since i won't be running a ton of cam going much bigger then the 315cc CNC head would be pretty worthless to me since most of thier heads flow the same till over .650 lift. in essence (and did see this in the graphs) anything larger just slows down the mix and makes less power. the 315cc CNC heads are going to be a BIG BIG improvement. so much that i am really looking forward to the day the cast heads come off. if i don't go with 315cc CNC heads i need something that at least flows comparably upto .650 lift. (the 315cc CNC heads flow 387 at .800 lift, but 312 at .400...they flow tons down low)

the valvesprings should live with the upgraded cam. before i assembled the motor i measured them but lost the numbers. they were pretty beefy though. last time this engine was together it saw regular 7500rpm duty, but this time around although rebuilt mostly for drag it will see a few street miles. parts should see little wear or abuse aside from the dragstrip. it is my firm belief thatthe springs will be ok for the time being. if not, they are an easy swap.

i was just hoping those specs could actually be ground. i may get a custom cam this summer to play around with once it's in the car and we'll see the improvement after being baselined.

 

You are dead right about the old L88 profile being a dog. The new profiles make more power all across the board. Don't get me wrong about the cast iron LS-7 heads. They are a good street head. In their day, the pro-stockers ground clear though the runners and then epoxied them back up to get them to flow right. But for a street head they are still good.

A mechanic friend of mine, who specializes in street machines (used to work at a company that built Nascar engines) just finished a 565 engine for his El Camino. I asked him why he used solids in his engine instead of solid rollers. His answer was for longevity. So there are a lot of compromises to be made.

Your lift at .600" should be very doable. As in my story of my engine, it was not a radical idle at .680", but I never drove the car on the street. As I said it was a marine cam with durability in mind. I'd suggest the biggest solid cam you can come up with. That way, when you go to aluminum heads, you are ready to rock and roll. Oh, and my friend's 565" engine seems to work well with a modified 850 rather than a Dominator. Your combination would be dynomite with FI, but they are pricey.

 

I'd go with a huge cam if i was sure it'd clear the pistons. they are domed and domed high. i figure mine is mild enough i won't have to touch it and still offers some solid gains.

solids do last a long time...and stand up to a ton of abuse.

i'd absolutely love...LOVE to go fuel injected with this motor. i'd also just assume rather spend the 2-3k on a good set of heads first. build the foundation first, then the house...but you're right, FI on this motor would rock.

also, the other FI (forced induction) woul rock too. i tested that cam profile with a garrett turbocharger, 10:1 compression and 20psi of 50% intercooled boost with the 850, and according to DD it made almost 1200hp peak. me want THAT kind of FI...

 

Hahahaha. I love computer profiling! It saves buckets of money over trial and error. But it will make you crazy after awhile. best of luck. Sounds like you are just driving the needle in deeper! My engine has morphed into 511", 8:71 Kuhl, MSD Pro-Mag, enderle FI on alcohol. The car is a 125" funny car chassied, 23T built for Nostalgia 1 and Top Comp/ Super Eliminator. It started life pretty much like yours, but a 496" with oval port heads and a hydraulic cam in my 3/4 ton '71 GMC. The only thing left from that original engine is the 4-1/4 " crank. It never ends, but that is okay!

Edit: Incidentally, you probably already know this, but plan for about 4500+ stall. Rear end ratio multipled by first gear ratio should = 9+, ie: 4.10 rear (street) x 2.48 (T400 or T350)= 10, it will get your attention!

 

you're right...the bug has bitten, the infection is spreading rapidly...i fear i don't have much time left...must grow...must assimilate more parts into the collective...must become one with the car...buwahaha

 

Anyone else wanna weigh in?

 

You really need to put the actual head flow data in to DD2000 to a halfway realistic answer out of it. Also, it is not that great of a cam design program. You really need to put realistic cam designs into it and see what you get.

Try these two cams in the program with pro-ported or AFR heads:

A maximum high RPM powerband type solid cam
265/265, 0.600"/0.600", LSA=117, ILCA=117

A street/strip maximum midrange solid cam for limiting RPM
254/254, 0.580"/0.580", LSA=110, ILCA=105

 

i used to work in a performance shop and spent a lot of time dynoing different combinations. i also spent time with DD2000. most of what i found is extrapolated, but there are a few cases where direct comparisons were also made from cam swaps where nothing else was touched.

what i found is that DD incorrectly predicts relative to 2 parameters. one is lobe separation (and IVC), the other is duration split. DD tends to favor a late IVC and wide LSA, and also bigger duration splits. in reality, tight LSAs and early IVCs, along with moderate splits, produce more average power in the upper half of the rpm range.

a couple of other things i found, the intake selections leave something to be desired. nothing in there can properly model what happens with LTx engines, for instance. then, DD also seems to ramp power as a direct function of cylinder head flow numbers, whereas the intake manifold adds to the system in such a way that real engines don't gain as much power as DD says from increased flow rates. lastly, it doesn't properly deal with ramp rate differences. (it assumes equal ramp rates for hy-roller and solid roller!)

just a few things to think about... did you try the iterator too, or just trial and error?

-michael

 

i used it a couple of times, but not for the cam specs. this was mostly trial and error, and what i ended up with just seemed way out of the norm which is why i brought it up with you guys

the engine is meant to be a high revving big block. i never really intended to pull stumps with it and knew most of the power would be north of 4k rpm...

aside from the duration and valve events, the specs i came up with are very close to what you mentioned.

thanks for the help guys!