breakthelawinaz

if you have followed my previous posts you know i have been in the process of building (rebuilding) and tuning my big block. well now im on cam number 4. the first cam was a first generation L88 cam, the second was a schneider grind 292-96F and the third was a comp grind CB 294S-10. the first cam was removed because it was the original cam and there are so many better grinds avail. that offer more bottom at no sacrifice of any mid-top. the second was removed because it lost a lobe on #4 int. which i (and alot of other people, including some on here) contribute to oil restrictors. the third cam i just plain dont like, so here i am, searching for #4.
here are my engine specs.
427 L88 short block blueprinted and balanced
12.5:1 forged pistons
forged 7/16 rods
forged L88 crank
iron closed chamber rect port heads ported polished and gasket matched
L88 valves 2.19 1.88 3 angle valve job
L88 springs
full roller 1.7 rockers
chromoly pushrods
cloyes double roller timing set
comp CB 294S-10 cam and lifters (Solid)
L88 oil pump
GM alum. Hi-Rise dual plane intake, gasket matched and polished
850 holley dbl pump
accel electronic dist.
accel super coil
MSD 6AL
hedman 1 7/8 prim. 3 1/2 collector hedders 3 in dual with crossover pipe... there prolly more.. but i cant think of it right now... let me know if you need more info

heres head flow specs done a 28 in/hg
.100 72.35 55.51
.200 146.66 103.86
.300 208.26 132.62
.400 247.85 154.91
.500 283.05 172.30
.600 310.05 180.20

the car is a 70 nova ss 4 speed 20k original miles PDB only option, didnt even come with carpet. the car is my weekend car.. not very often, and track car.
3.73 rear muncie m22 rockcrusher, i just want a fun very quick street car. i want it to pull so hard you cant hold your head up...

the L88 cam was too little bottom mid, it was very hard to drive on the street. not sure of specs but will find

i really liked the schneider for the hour i got to drive it very crisp and pulled very nice,
intake-258 @ .050 .578 lift
exhaust-262 @ .050 .578 lift
LSA- it says 108 106 so im assuming 107?

the comp has lots of bottom-mid but hardly any top. i think it has something to do witn the 110 lsa and low duration high lift design, Kinda lazy off throttle, not really crisp and a mild idle
intake and exhaust-250 @ .050 .595 lift
LSA-110

i want a cam that starts to come on about 30-3500 and pulls extremely hard till 65-7000. i want it to be very crisp off throttle, and a nice lopey idle like the L88 cam was. i run 110 leaded turbo blue so any LSA should be no problem. i know if you close up the LSA it raises running compression. i want to stay solid flat tappet. i was thinking this motor needs a split profile with more exhaust duration and a tight LSA. if you need more info please post your issues and i will try to answer to my best ability.

also what carb should i run i have a 750 dbl pump and an 850 dbl pump, it likes the 850 right now. i was thinking of getting a new one, i also have the original holley 780 vac sec off of a 71 vette LS6 that needs rebuilt, but im looking for anything. i want to keep the dual plane intake even if it cripples me a little, since it is also a show car and i want to try and keep a semi-stock look.

ok im tired of typing please help me out...

*Eric*

rskrause

I'll take a stab at it. But pulling to 7K with the dual plane is not gonna happen, IMHO. Comp XS268S might fill the bill, but that dual plane is gonna be a problem if you want to rev >6K

268/274 .563/.568 110

Rich

Lonnie Pavtis

The factory BBC dual plane with cut plenum divider (as the factory L88 is) with an 850DP will pull hard to 7000+ I used to shift my L88 at 7400 with the factory intake & run in the upper 10's.

You will need more gear if you intend to run the L88 style or bigger cam. The 2.20 first gear & 3.73's is lazy in traffic & hard to launch. 4.10's w/ a 4 speed are way more suitable to these bigger cams, but will suck on the highway if it matters. I got used to keeping up w/ traffic at 3500 rpm.

I now run 25x/26x .708" solid roller. A bit much around town, but it will put out the HP. More duration & you may have trouble launching the car at higher (4500+) RPM due to your limited suspension (wheel spin) & possibly bog it on slicks at lower speeds. It is a fine line with a stick car. The tighter lobe center helps here as well. Your Nova does not have much wheelwell to fit tires. I had a 70SS Nova & feel your pain. Without tires, none of this really matters as you will just have a tire burner.

If you want it to perform go with some lift. Under .600" is not serious big block territory.... look at your head flow. The big block wants lift & the big ports will not do much under 4k anyway. The valve springs will live much better than the typical small block due to the larger spring dia & installed height. I run .580 lift cam in my 427 pickup truck as well & it has lived for years at 6500 with the same springs. Stay conservative on seat timing & look for an aggressive ramp, preferrably the roller.

My cam catalog has vanished, but I'll try to get you some specs later. Hope this helps.

Stephen 87 IROC

You've got a bad combination of parts for what you want to do. There's nothing wrong with all the parts but as mentioned above, the dual plane intake isn't for the rest of that engine no matter what cam you try. All your cam choices so far are fine however with those huge rectangular port heads, you're wasting the cams. If you had some oval port heads, those cams will work much better.

I ran a Comp Cams 11-613-5 cam with oval port Merlin heads, 13-1 compression, Victor Jr intake and 850DP carb to get my best results so far. My new engine this winter finally gets aluminum rectagular port heads and .722 lift roller cam.

Stay with the 850 carb. Even the 427 will want more fuel. If you're intent on keeping the dual plane intake, get rid of those huge heads and find a set of 781 or 049 oval port heads. Have 2.19/1.88 valves installed with some port work and you'll be much happier.

rskrause

I agree. I think those parts are mismatched. The cam I suggested is "too small" for the heads, and not really big enough to pull to 7,000rpm. It's kind of a "Catch 22" situation. He wants good low end and to pull to 7,000rpm. An OHV motor ain't gonna do that. Maybe a multi-valve with variable valve timing, variable length intake runners, etc. But not a BBC, at least from what I have seen. My knowledge of the BBC is kind of out of date though. I used to run them and now again have one, but only for three weeks! So I am both an old fart and a newbie in a way.

Still, even though I usually agree with Lonnie I wouldn't use a dual-plane intake for a 7,000rpm motor. I think Eric needs to decide what he wants to give up. He can have mid-range and top end, or low end and mid-range, but not both.

Rich

OldSStroker

I agree with Rich (again!).

Every car/engine combination is a compromise, and something has to give. If the cam/valvetrain is the only variable you are willing change, and you don't have much overall gear for launch, how about paying an engine designer to try to optimize the system you have? I say pay, because this may take a few hours. As much as you want a 3500-7000 screamer, your car/engine combo may not be willilng to do that for you. You just can't reason with cast iron and aluminum.

My guess is that your combination is a tough one to work with, and since you have already gone thru multiple cam grinds, you might not be satisfied with any cam. Sometimes you just can't get there from here.

Good luck!

breakthelawinaz

yeah, it is a hard situation to deal with... i know its going to be hard to do both with the dual plane.. but it does have the cut plenum divider... which will help. i really dont want to run the single plane for 2 reasons, i like the look of the dual plane (it keeps the original look) and i dont think ill have the hood clearance to run a good single plane. i would give up a little rev if i could make up for it somewhere else, i know that this motor will easly hold up to over 7k but it still scares me, so i dont know what i want... im open to all ideas...

i dont think ill have a problem with valve spring bind but my P-T-V clearance is what worries me... im thinking more lift would be good but i was actually thinking it needed more duration than lift, but i could be wrong?

what i really want it a fast car to put it bluntly, i just want to to be very quick, but still somewhat drivable, but drivability isnt a huge issue since its not a daily driver... (i think the 20k speaks for itself) but id still like to not look like an idiot that cant drive a stick... im focusing on as much mid to top as i can with a dual plane, but its not much of a dual plane its pretty hacked... but since im paying $4.50+/gal for 110 i want to have the most fun per dollar...

ok well im sorry if this is a somewhat incoherant rambling, im kinda tired but i want to try and clarify, if this is totally confusing let me know and ill try to clarify.


*Eric*

Lonnie Pavtis

Here is your dilemma.....
You need to determine what you consider fast....... Is this 11's, 10's etc.
Then you can base your combination from there.

The rectangle ports are not going to give good low end response. Don't expect much under 3000rpm. The port cross sectional area is not compatible with low RPM. If you ported these as well, things are even worse.

The dual plane is not as good above 6k as a single plane, but it is more than adequate for a low 11 sec street car. Getting a tall single plane under a stock Camaro or Nova hood is not going to happen. My own '68 Camaro uses an old ported C427X dual plane Edelbrock intake that barely fits under the SS hood. It required cutting the choke off & cutting the filter base to drop it down over the carb. Usually single plane = cowl hood unfortunately.
I built (2) 427 cars ('68 Camaro & '69 Nova) running 10's with a dual plane intake so don't look at this as a major hindrance.

Your 12.5:1 comp is already limiting your streetability..... due to affordability.
If you can afford $5/gal gas, you could easily afford a more livable compression as well. I have a car that needs race fuel & based on the lack of overdrive, big cubes & a healthy cam with a carb, you will not take many rides that cost under $25. This takes the fun out of many rides unless you are at the track.

You stated in your original post that you want the mean loping sound. That only comes with overlap based on a tight lobe spacing and/or large duration.
It is hard to have the best of both worlds. Your lobe separation will also change your piston to valve clearance. The exhaust is usually the one to watch. If memory serves me correctly, you are good to approx .650" with the factory TRW style pistons unless you cut the heads excessively.

If you insist on high compression & a healthy cam, you will likely be stuck with some low speed drivability issues, poor mileage & expensive fuel requirements...... but it can be made to run & sound well. I insisted on doing this when I was in my early 20's as well. Now I look at more than I drive it.

Erie is not that far from Pittsburgh, so you could always sell me the Nova as I really miss mine....

breakthelawinaz

hmmm... what do i think is fast, well right now in current trim i ran at pittsburgh raceway park, i think thats the name, and ran a 13.7 @ 117 on 245/60SR14 Performer radial GTs, which had a lot of wheelspin which i beleive is obvious. that should translate to a high 11 if i correct according to trap speed with something called traction and that isnt quick enough. what is quick while using the dual plane? you said you were running 10s with one, what do you think im capable of with a car that is semi light like this i think ti was around 32-3300 when i measured it on a truck scale with a full tank of gas. dont worry the next trip to the track will have slicks or et streets, something like that... the dual plane i have is just gasket matched, and has no center divider, is there anything else i should do to it to help?

cowl hood is almost out of the question, so i dont know where else to go, it is all original including all sheet metal and paint so thats why it is out of the question...

well with the race gas its not a problem for affordability, especially considering that the price of 93 keeps going up, and it seems that race gas has stayed steady, i dont mind getting it for as little as i drive the car, the only pain in the *** of that is that there are very few stations you can pull into and fill up...

the lope im referring to is like the factory L88 like lope, this cam in it now sounds alot milder yet has more lift and duration, which leads me to beleive it is LSA, and 110 just dosent seem adaquate for this motor anyways, the lope really isnt anything to me, kinda the last think im looking at. this motor will always have a lope with any sort of cam so i guess disreguard that.

.650 lift leaves me room for a good decent cam, i really wasnt looking for anything bigger than that. ive heard the exhaust is the one to look for, but the heads have never been cut, there isnt hardly any miles on them so there way no need and when checked they were absolutely fine, and the block was never decked, once again flat so that should leave me some more room.

the low speed drivability isnt a huge issue to me, by drivable let me define what i think of it. a little bit more docile at low speeds than the L88 cam, not like stump pulling torque, but not like L88 cam style, i know there have to be cams out there that are a little better then the L88 in terms of bottom mid and top, because after all look how old that design is and how much technology has advanced.
Thanks,


*Eric*

70ss

In my opinion the heads don't flow enough to turn the rpms you are looking for. We do lots of BBC for the marine world which means low rpm hp and tq. The intake side isn't bad for those heads, but the exhaust could use some work. I like to see 80% of intake flow. If you can get anywhere near that you'll be amazed at the increase in performance you will see.

Once you get the heads to flow, you can add some cam.

Rod

breakthelawinaz

i dont disagree or agree with you saying that the heads wont support that much rpm, but i thought i would bring up a valid point, the L88 heads flowed enough to support those RPMs, and i flowed these heads before and after, and i picked up no less then 10 cfm in any one place... which would put me over and above factory heads that did support that RPM. that is why i never questioned whether they would support that...
thats just my opinion


*Eric*

OldSStroker

You may have been told wrong. I've met some pretty savvy folks who were NEVER young and stupid, but became old(er) and wise(er). I have met fewer who were Y & S and later wised up. I've met way too many who were Y&S but became Old and Stupid.

Sorry about picking on your siggy. If you are inexperienced, listen up to what some of the wise folks around here are saying. A couple of them have posted in this thread.

"With Age comes Wisdom....sometimes Age shows up alone."--Anon

CrossupBill

Crane has a great solid flat tappet cam that I have used in the past. Don't remember the part# but the specs are 256/264 .618/.638 Sounds good and runs like stink!

breakthelawinaz

oldsstroker... the sig is kinda a goof, i have been told to many times i have been too young and dumb and noone trusts a 19 year old KID! i put it there to say what i know what some people are thinking, but hopefully i am able to prove them wrong... and about listening to the people here, why else would i post this topic here rather than anywhere else on this entire internet, just the combined knowledge and experience on just cz28 is just mind blowing


crossupbill... actually that is one of the cams i was looking at for my next one back about a week ago when i was catalog surfing, but i was wondering about the LSA and is that duration is at in thousandhs of an inch, i noticed the comp cam i last got was at .015 rather than .050, both were listed but the first is the emphazied...

thanks


*Eric*

CrossupBill

Don't remember the LSA but the duration is in degrees @.050"