Hello, I need advice on what to go with. Sofa had recommended the 276 but the more read the more i want to go with the 282. I read a post from i thing it was chevyperformance where they built a 355 with the same holley systemax aluminum heads i have and they made 419 hp and 447ftlbs with a cam similar to the 276 but was flat tappet. so my question really is how much power did you make with the 282 and how streetable was it? Thanks for your advice.

 

im running the 276 in a 355. Made peak power at 6000 rpms with garbage dart iron eagle 180cc heads. 275hp/315tq at the wheels with a garbage exhaust system and an electrical problem that was messing with the computer.

duration effects how high in the rpm band you make power.

make sure youre choosing a cam that makes peak lift in the same area that your heads start to fall off after peak flow for the best combo.

 

Thanks for the input doug, I would be getting it on a 110 lsa. For exhaust i have hooker long tubes with a 3" dual exhaust w/h pipe and no computer. So do you think that the numbers posted by http://www.superchevy.com/technical/...no_graphs.html are realistic?

 

419 hp would equate to around 350 wheel hp (i think, thats just a guestimate) which i would think to be the very upper limit. I would expect around 330 wheel and hope for 350.

I honestly dont have any info on the systemax heads but if you could get flow numbers in the 245-250 intake and 185-200 cfm exhaust it should be possible.

its important that everything match tho, and to figure this out you either need to get your heads flowbenched or talk to someone/find an article where someone has flowbenched that head.

The flat tappet cam they use is very low lift. If you ran a cam that went to .52 lift but your heads dropped off flow at .48 you would be losing power throughout your entire powerband.

With airflow there are two important properties, volume and velocity and you dont really want to sacrifice one for the other. The more the valve opens the more velocity you lose and if youre not gaining airflow by opening it further then the heads can flow.

a motor is not just the sum of its parts, everythign has to be designed to work together for optimal performance.

 

They holley website says that they flow 223 intake and 178 exhaust. their the sbc heads on this page: http://www.holley.com/data/Catalogs/...er%20Heads.pdf

 

theres a guy running that 282 cam that recently posted a clip of his idle. Its a good cam. Can be streetable in a 355 with good tune. will peak around 6200 rpms from what i've seen. Runs good in LT1 cars so a carbed car with decent heads should make good power

 

Thanks again for your advice, I know lasttime i said i was going to go with the 276 you reccommended but everyone i have told that i was going with that cam told me to go one step higher. They say that everyone says i wish i had gone a little bigger but hardly anyone ever says i should have gone one step smaller. That is why i wanted to know what people with that cam in a 355 had experienced. By the way do you remmeber the link to the sound clip? Thanks again.

 

yeah, i'll have to look for it. Or try to search for it. But make sure you run good valve sprigns to handle that cam's lobe profile. They are pretty aggressive and getting them to rev over 6000 requires strong springs

 

I got the springs on the heads checked and they have 120 of seat pressure, so i called comp and they said that they should be fine since the springs they recommend for that cam are rated at i think 123 pounds of seat pressure.

 

thats bare minimum. I'd like to see more like 135-140. My custom grind has less aggressive lobes but alot more lift and designed to rev up my 383. I'm running 165/170lbs on the seat as recommended

 

do you really want to make peak power at 6200 rpms? that calls for shifting at around 6350 and redlining at 6500. Hope you have a bottom end and oiling system planned for that. I would also like to mention that i wouldnt be happy with a cam any bigger then what i have.

the higher you make peak power, the higher the bottom end of your powerband is going to be. My car still needs computer tuning but it doesnt even come alive until 3000...and then it screams till 6. Bigger isnt always better, especially if youre going to be running mostly on the street. Gotta keep the midrange in mind.

also ive got 222/172 out of my iron eagles i have no idea how they pulled 400+ hp out of those heads on an engine dyno. Must have one hell of a port design on those heads, but i wouldnt expect any more then 325 at the wheels.

Youve also really gotta be thinking about what lift youre shooting for, it matters, and as i was trying to explain before more isnt necessarily better.

they may have used a flat tappet cam in that article because these heads make peak flow below .50 (just a guess) which if they can flow that much down low almost explains their power gains. Thats why people run flat tappets is so they can have high duration without running crazy lift.

 

I actually ran the 282 in a 400. I liked it; but it was a handful. It was more than the XE274 that replaced it, by a long shot; although they don't look all that much different, on paper. But they sure are.

Remind us what the rest of the combo will be.

Less CI, less heads, less converter, less gears, argue in favor of a smaller cam. Bigger motor, bigger heads, looser converter or a stick, and short gears tend to allow bigger cams.

 

lol a 400 vs a 350 just throwing random numbers out there but im going to guess that same cam would make peak about 600-750 rpm lower then in a 350

 

Yeah, probably something like that.

The difference between a 350 and a 400 is about the same as one step in most cam mfrs' product lines. So the XR276 in a 350 should run alot like the 282 did in the 400, more or less.

 

Whoa whoa whoa there. You're paying money for heads that flow like that?!? That's barely vortec range. That's ported L98s range. That's nothing to write home about, and NOTHING to pay close to $1000 for a set (or whatever they typically cost). I'd rethink those heads.

And yea, i'd do the xe276hr over the xe282hr. You get tired of the big cam feel pretty quick, and the power difference won't be that big. You'll enjoy the smaller cam more, IMHO.

 

on an afr web page comparing their heads to other manufacturers they list the systemax heads at closer to 145/181

good on the intake side but id have some port work done to the exhaust side before slapping them on your motor.

still wouldnt be my head of choice tho

 

Remember look at the pictures..... no mufflers, tailpipes, alt, power steering, ect ect.... Those are gross HP and Torque numbers. 400 hp - 20% = 320 hp installed = 256 Rwhp with auto. Mag numbers always look good.

 

I guess that was me!!

You can check out my motor and timeslip in my sig. The bottom end still has the stock L98 crank, rods and pistons. We did flowbench and work the AFR heads. We also put shims under the AFR springs. You really should be between 135 to 140lbs on the springs.

I think my et/mph and weight of car figures out to around 330 rwhp. I should be faster this spring going from a 750 vs holley to a 750 Street HP. Should be good for 11.90's.

 

Sonic, I didnt pay full price for the heads i got them pretty much for vortec price with matching intake.

Sofa, as far as what i will use withthe engine is a t56 and 373 rearend.

Bluegrass, so since you are actually running it in a 355, same as i would be running it in how do you like the cam? Thanks again for everyones advice.

 

If the heads aren't installed, i'd think about doing a bit of port work on them. They can probably be improved.

 

Same combo I have...

I think that might be why I suggested the smaller cam. With the close ratios and the high ODs that the transmission has, you don't HAVE to wind the engine up to get the car moving; and on the highway, your RPM will be so low, that you'll end up with the car bucking and snorting and otherwise complaining, if it can't run gracefully at 1500 RPM and still produce useable power. You don't want to cam it up to where you have to downshift 2 gears just to get up a hill.

 

You're still missing the point.

You can't compare a 350 with ported AFR heads with poor flowing heads when deciding on a cam. Meaning wether he likes the cam or not, yours will NOT run the same...not even close. So his input in your decision should be irrelevant unless you plan on buying 190 AFRs and porting them. Even that 276 cam is pushing the limit of those heads, nevermind the 282 cam.

 

from what i've seen, even tho its alittledifferent, LT1 guys run the 282 cam just fine on their stock heads which flow similar to those system max heads

when i was considering cammed L98 this winter, i was gonna run the 282 cam. With a proper tune i think you can get away with it. Also you can run 4.10's in a T56 and be fine. with those overdrive gears. the 282 isnt THAT big of a cam. Get it on a 112 lsa and it will be good to go. most lt1 guys like it to idle around 900 rpms and it sounds great. I dont have teh experience with that cam on a motor, but from everything i've seen ppl tend to like it alot. its DEFINATELY less aggressive than the popular cc306 cam.

YOu cant go wrong with the cc503/xe276 cam tho. It will make probly 10-15lb ft more torque and only give up 10-15whp up at the highest peak rpm range. (5800-6200).

 

I have been told mainly in this website that those heads will not flow enough for the 282, But i have done searches and have read of people running those heads on a 383 with the 282 and they ran fine. So i dont see why everyone keeps telling my that they suck. They flow about the same as vortecs and i have also read that vortecs make 400+ hp easy. Now i am not trying to say i know everything if i did i wouldnt be here asking questions, but i think those heads MIGHT be a lil better than alot of people think. Now i probably will take your advice and have them ported and polished just for good measure. And Sofa i hate that you know what you are talking about because it does make sense what you said. It would be a waste to have the 2 OD's but not be able to use them because the cam wont like it. I really wanted to go with that 282.

 

Well about the rear end/T56. 6th gear is deep. With a 26 inch tire, those gears and 60mph will be 1450 rpms, and 70 is just under 1700.

5th gear would be 2140 rpms or so at 60, and 2500 at 70. That is like stock 700r4 auto in overdrive. Thats very nice for the street and that cam SHOULD handle it from what i've seen.

Whats your motor's compression at? that will help determine your torque output if its gonna make enough usuable power at those low rpms to keep that car going. with the proper tune i think its possible that it will be fine in 6th gear at over 60 mph but then again its hard to say. I dont know for sure. Just trying to relate what i've seen posted about that cam and other similar combos.

4.10's would be a much better choice for that engine/tranny setup anyway if you go 282hr cam

 

The block is actually at the machine shop right now, but i am shooting to be somewhere about 10.1:1 thanks for your help

 

youre still missing the point

still have no idea why you want to make peak power at 6200, if i could make peak at 2500 rpms id be happy as a big in poop if it got me the power i wanted.

The heads are good for 300 wheel hp in their stock form with a manual transmission. Youre simply not giong to get much more out of them then that.

this is my third time trying to tell you that matching the lift specs to the head is waaay more important then the duration, but that doesnt seem to be getting through.

 

I know, I know, all of you are most likely right. And am going to go with the 276 for all the reasons you all have gave me, I just really wanted the 282 for its performance and sound.

 

i dont know about 300whp. if they only flow 225 cfm thats good for near 350whp with a big cam and decent compression. Lt1's only flow like 215 cfm stock and many cam only guys (282 cams to be exact) are making near 350-360whp. vast majority make around 340 tho with a stick. thats pretty good and they peak around 6000 rpms before the heads choke it off, but it holds power for a decent ways beyond 6000 tho.

 

Orr89, so you are saying that automatic trans cars lose less power than a manual trans? I always thought that manual trannies had less power loss.

 

ya youre probably right, i guess i was basing that more off my combo but the 275 wheel i made with my new exhaust system should put me a lot closer to 300.

and iroc manuals have less drivetrain loss then automatics do, just to clear that up it is how you thought.

that 276 with 1.5 rockers should make for a very stout motor in your car. I would still be curious to see those heads on a flowbench tho to see exactly what lift the airflow stops increasing.

 

AFR had a showdown of aluminum heads and the numbers are here http://www.airflowresearch.com/chp_test.php.

 

yes i ment to say auto's lose more power than sticks, typically. When i say vast majority of cammed only LT1's only make 340 with a stick, thats the average, as some guys have made more power on the dyno than others using same setups. Auto's are down 10-15whp more in some cases.

either way the 276 isnt a bad choice. Those LT1 guys run that cam see 340whp. Some almost 350 i believe. The bigger cc306, GM847 and 282 cammed cars are near 350-360whp. GM847 is abit larger than both the cc306/XE282 so it shows when you can have too much cam

The extra 10-15whp you gain at PEAK with the 282 cam will show 10-15wtq lost at the lower rpm ranges. So choose your sacrifices.

 

i am running the 276hr cam in my 383 HSR

 

Orr89rocZ, you are right again, i did a simulation on comp cams cam quest and it said that with the 282 i would make 468.5 hp and 466.5 ftlb and with the 276 456.2 hp and 471.4 ftlb. so yes i gain 12 hp but lose 5 ftlb peak and it would raise the peak power from 5500 with the 276 to 6000 with the 282. I also ran the numbers super chevy used on their build up, and it was pretty close, it was only 5 hp over(camquest)from what the magazine actually got.

89formula how do you like that cam? the times you have posted, are they with your current set up?

 

ya but what youre interested in is flow numbers at

.45
.46
.47
.48
.49

all the way until at least .53 . Its important to know at what point the flow numbers stop increasing dramatically, because thats how much lift you want to have.

that chart isnt useful for that.

 

yep there is a point where heads will back up and become turbulent and having more lift at that point will actually hurt.

Hard to say where that point is without testing it with and without the intake on the heads as intakes will change flow pattern thru the head.

 

it sounds an awful lot like they would be similar to a vortec head, and im guessing they ran a flat tappet cam in that article for a reason. On the other hand .503/.510 lift shouldnt be that detrimental just trying to make iroc realize that while peak numbers are great for bragging rights, having a matching combo is necessary for quality midrange power, which is what you need for a fun daily driver.

 

I dont realy understand what you mean. i do have these flow #
.050 i/e 38/28
.100
.200
.300
.400
.500
.600

 

I dont realy understand what you mean. i do have these flow #
.050 i/e 38/28
.100 66/53
.200 130/92
.300 184/122
.400 222/148
.500 242/172
.600 252/187

I dont know if this helps. But i hope it does.

 

ya but where between

.40
.50
.60

does peak flow start to fall off? If its at .48 and you ran a cam with massive lift like .54 youre not only losing velocity from the valve being open farther then is beneficial, as Orr said the vacuum in the engine is then trying to pull more air in then the heads can flow, causing turbulence and massive amounts of lost power.

for an engine that makes the best power through the whole power range, you want a cam/rocker combination that puts your lift in the same place that your heads make peak flow.

An engine is not the sum of its parts, all the parts have to match for it to run well.

 

Those are the main ones you need to look at. Best overall power will be made with a set of heads that flows the most in the .100-.400 range. Low to mid lift areas. A head can flow more peak at .500 than another, but if that other head flows more in the low lift regions, it stands a good chance of making better overall power than the peak flowing head.

I agree, i dont feel 1.6 rockers with that cam really will deliever any better results than 1.5 rockers, especialy on those heads. now if you had a set of heads that REALLY flowed a big difference between .500 and .550 lift, then the added lift could help.

On a side note, my engine desktop dyno 2003 program has systemmax heads showing good numbers. Same as you posted

.100 66/53
.200 130/92
.300 184/122
.400 222/148
.500 242/172
.600 252/187

If thats the case, then by all means get your moneys worth and run those heads with that 282 cam. I think it will complement it well. Thats my preferance tho, i like a bit of a aggressive street car. BUT that smaller cam will still make good power with good flowing heads. Flow looks to keep increasing with lift, so run as much lift as you can, aka 1.6 rockers.

 

So can i tell if even the 276 is not a good match for my heads? I called summit and holley and both recommended the 276 as well as alot of people here. I understand that its not the parts that make a good engine but the good combination. that is why i want as much info before i get the cam. thanks for all of your help so far.

 

i disagree and would run the 276 simply because i wouldnt want to be making power above 5900 rpms, i just find 6200 rpms to be unnecessary for a street driven 355 and puts your powerband that much higher.

That being said if there are good lift gains up to the .53-.54 range that motor might just benefit from 1.6 rockers with a 276. You cant know without flow bench numbers for every .01 of lift between .40-.60
----------
its not possible to determine what lift you should be shooting for without flowbench data that shows you where your lift falls off.

 

I can agree with that. I just prefer a more aggressive street car than others and dont mind revving to 6500. My 383 should make peak by 6000 rpms all the way to 6500 if the HSR supports it.

The beauty about good flowing heads in the mid range and the right cam grind, you can make great power at high rpms without sacrificing low rpm performance. Just gotta have decent compression to make up for the larger cam's overlap.

To be honest, there are a few options here. the 276 cam you can get with both 110 lsa and 112. Irocbrningrubber is considering the 110. Not a bad choice. What intake setup will you be using? Carb or fuel injection, sorry if i missed that part

You can also get the 282 cam on a 112 lsa from thunderracing or comp cams. That cam has only 2 degrees more overlap than the 276 cam on a 110lsa. Both cams should act about the same at idle and midrange but the larger cam will make abit more power due to the duration...so i dont think you can go wrong with the 282 on a 112 lsa.

its all about the OP's goals tho. Whats your definition of a street/driver car? What do you want out of the car? Again, you cant go wrong with either cam at all. Both are good matches for the head, just one cam is abit more aggressive of a street car.

 

I am going to use the holley street dominator high rise dual plane. It is supposed to flow up to 6500 and it is going to be carb'd. as far as what i am going to use it for, it will see about 80% street driven mostly weekends and some strip( 20 min away). I want it to be fun driving around town and not only when i get it over 4500 rpm's. Thanks again for your help guys

 

well to be honest, my searching (and i ahve done ALOT) about these two cams on camaroz28.com has led me to believe the 282 would be a better choice than the 276. I was nervous about loosing alot of driveability but seeing countless posts on that site about the 282 cam, i chose to go with that cam, but after looking at my old L98, i decided a cam swap was not a good idea I'm not pushing you to go with the larger cam, i just stating its possible it could work well for you and not be the Big bad cam people make it out to be.

But one thing i have learned is this site is abit more conservative with cam size selection, maybe due to TPI's short rpm range, and the LT1 world loves to run big cams and rev up, since they can support it. Oh well, good luck with whatever you choose.

 

Well, I think the trend here is different for a reason. There seems to be a more practical approach here. The GM systems are easy enough to tune a nasty cam to run. The problem is why do it when the intake runs out of gas at what 5500 rms fully modded? Trying to run a cam that peaks above that is pointless. That seems to be the argument i hear most against it. I have never had a tpi car, but have worked on some.

 

yes for the most part that is the reason, but when people switch to HSR/Miniram/etc, i still see smaller cams. Just abit more conservative nothing wrong with that, they still can make great power.

 

whats the logic on more duration making more power because thats something i dont really have a scientific explenation to. Is it simply the valves opening and closing more in the same amount of time will always make more power?

I have to comment tho that i notice a BIG difference in low end power with the 276. Try thromping on the gas at 2500 rpms and it feels like a honda, but at 3200 it goes from steady acceleration to all hell breaking loose.

With a manual tranny its not really a big issue tho cause at part throttle you can keep your rpms wherever you want them to be.

it could still have nice street manners shifting at 6500 rpms thats just a loot more stress on your engine. Higher you go the more often you better be planning on making repairs. I can see wanting it if you desperatly want that extra 10 peak hp, but unless youre in some form of competitive bracket racing i dont see the benefit of taking a v8's powerband that high.