seanof30306

iTrader: (4)

gathering parts for my cam/ head swap:

already on the car are slp 1 3/4" headers, dual 2 1/2" catco cats, 3" mandrel-bent intermediate pipe, flowmaster 40 series muffler, dual 2 1/2" mandrel-bent tailpipes, ultimate tbi mods, injector spacer and factory cowl induction

i have a set of zz4 heads that have been ported to flow as well or even a little better than vortecs and a weiand 7525 intake to go on the car. i plan on a cam swap at the same time. i've been thinking of an lt4 hotcam and 1.6 rockers. however, i've also been looking at a comp cams grind.

the lt4 hot cam's specs are .525/.525 lift (1.6 rockers), .218/.228 duration, 112 lsa.

the comp cams grind is .510 /.510 lift (1.5 rockers), .220/.230 duration, 114 lsa.

while the comp cams grind has just a bit more duration, wouldn't the 114 lsa make tuning it easier?

also, does anyone have the formula for calculating lift with 1.5 and 1.6 rockers?

ShiftyCapone

iTrader: (7)

With the right tuning you will have an awesome power house there. Have you looked into a larger TBI unit. You will need it to feed that motor properly. Either cam should yield great results. I don't know of anyone that is running the hot cam but I think it would be a great choice for our cars. It should have a nice idle and be pretty striahgt forward to tune. It will be harder to get the tune on the right track with the large duration of the second cam for a novice tuner. To calculate lift with different rockers you need to know what ratio they are specked at first. I think the hot cam numbers are with 1.5 so to see what it would be with 1.6 devide by 1.5 than multiply by 1.6.

So if a cam have .525 lift with 1.5rr than devide by 1.5 to get .35 (lift of cam lobe) then multiply by 1.6 to get .560. Pretty easy. You would do the same thing if you need to go from 1.6 to 1.5 as well.

EDIT: I just re read your post and saw that you have what the cams are specked with.

So the hotcam with 1.5 rr would become .492
.510 lift with 1.6 rr would be .544

Dewey316

you need to do some more calculations to find out which will be 'easier' (they are so close, it is probably a toss up.)

Figure the overlap, the more overlap, the more the o2 is 'fooled' (i really don't know how to state that well).

cali92RS

Do u know the part number or grind number of that comp cam?

JokerRS

Who is going to tune this beast? Which injectors are you going with?

seanof30306

iTrader: (4)

The part number is 07-305-8 and the profile is LT1 276HR-14. i'll be doing the tuning, but that's a ways down the road. i plan to do a lot of tuning with the setup i have to become pretty skilled at it before i attempt something this complicated.

i'm thinking 65pph injectors to start. i have a vafpr, so i can adjust the fuel pressure as needed.

cali92RS

this is going into a 350 correct? Thats one hell of a cam.
I honestly think its kind of big for a tbi.
Put it this way, its larger than the LPE 219 cam, which was designed for a super ram, which flows a lot more than the biggest tbi's and has 8 injectors.
I think the hotcam would be a better choice.

seanof30306

iTrader: (4)

nope, it's going in a 305. the comp cam is only .510 lift (1.5 rr), while the lt4 hot cam is .525 lift (1.6 rr, which is what comes with the lt4 hot cam kit).

the duration is nearly the same: .218/.228 on the hotcam, .220/230 on the comp. the loss of velocity and vacuum caused by the slightly longer duration on the comp cam will be offset by the com cams' greater lsa (114 to the hotcam's 112), i just don't know how much.

as far as airflow, the cam is only a part of that equation. airflow need is dictated most by cylinder volume, then the heads' airflow, then the camshaft. since a 305 has such a small bore, i'm pretty sure the stock tbi unit will flow enough air. if not, i'll have it bored out to 2". way back in 1989, hot rod did a series of articles on a 1989 rs camaro 305 tbi 5 speed. they used tpi corvette heads and a reground camshaft to make over 300 hp at the flywheel with a stock tbi unit. we'll see.

cali92RS

What were the specs on the camshaft used in the article?

I think those cams are way too big not only for a stock TBI, but for a 305. In a 305, those cams are gonna make max hp at around 5800 rpm.
I think induction/cam matching is very important. You are cutting youre powerband in half. On the low end that cam doesnt make power till about 2000 rpm, and in the upper end, your induction falls on its face past 5000 rpm.

seanof30306

iTrader: (4)

they never published the specs. at the time, traco engineering, the company that did the work, was developing the parts to sell and didn't want to release the specs. i ran down the former owner of traco engineering last year. he's now chief of engine development for calloway corvettes. all he could remember was the lift was around .510 and it didn't have enough duration. he said they'd decided to go conservative on the duration because of the map sensor and later regretted it, as they could never get the car to hook up with street tires. he said with more duration the torque curve would've moved up in the rpm band and cut e.t. dramatically.

if you look at the june issue of chp where they did a 305 vortec buildup, they made 229 rwhp with the stock throttle body and without yet tuning the chip. their cam specs were .510/.520 lift and .210/.214 duration on an lsa of 114. they made peak hp @ 4700 rpm and peak torque at 3,800 rpm.

the cam doesn't tell the whole story, though. they had the bejesus ported out of their vortecs. here's their flow numbers compared to the flow numbers on my ported zz4 heads:

lift .... intake/exhaust zz4 ......... intake/exhaust chp vortecs
.300" ... 175/128 .......................... 184/152
.400" ... 206/154 .......................... 221/165
.450" ... 212/167 .......................... 234/173
.500" ... 215/172 .......................... 252/181
.600" ... 215/177 .......................... 237/184 (.550", they didn't go to .600")

while my ported zz4s flow better than the stock vortecs on the exhaust side and a little worse on the intake side, they don't even come close to their ported vortecs' flow numbers. in this case, i need to make up the difference with the cam. i'm in a good position to do so, as they're running the gmpp vortec tbi intake, while i have a weiand 7525 single plane intake. it's single plane design gives me a much greater plenum volume. since neither cam has a lift greater than .525", the flow numbers at .550" and beyond don't have any real meaning.

comparing the two, the big advantage with the vortecs against my zz4s is on the intake side. comp cams makes a 1.52 roller rocker. by running 1.52s on the intake and 1.5s on the exhaust, i'd end up with intake/exhaust lift of .516/.510. the longer duration of the cam i'm considering would also help make up the deficiency, keeping the valves open longer to flow more air.

the larger plenum volume of the single plane carb intake should let me make power at higher rpms than the tbi intake they used, or the performer rpm tbi many people on here use. plenum volume is critical ond oft forgotten. ever wonder how an ls6 make nearly 400 hp @ 6,000+ rpm with such a small throttle body? plenum volume.

i'm looking to make peak hp at around 5,000 and i want the torque peak to fall somewhere around 3,800 rpm, as chp's does (so far). if the longer duration cam i use doesn't have enough bottom end, i can always advance the cam a few degrees.

these cams are actually pretty mild. the issues with making either of them run has little to do with airflow and everything to do with their ability to make enough vacumm at low rpm to make them tunable on a map system.



i

Dewey316

i hope you have a great handle on tuning. i can tell you how much work it is to tune a cam in the 210 intake range. that is nowhere near 230. 230 is a HUGE cam for a 305.

and fwiw my engine is still pulling at 6k.

seanof30306

iTrader: (4)

dewey,

i agree, but there are guys running the lt4 hot cam, which has almost the same duration and 2 degrees less lobe separation. it'll be a long time before i'm ready to tackle this tuning job, but i believe it can be done.


and calirs, com cams says the power range on this cam is 1500-5500, the same weiand claims on my 7525 intake. i am matching the induction to the cam. the ONLY benefit to running a 305 is that the lower cylinder volume means tbi CAN move enough air to supply it over 5000 rpm, where it can't for 350s and 383s.

also, when you're launching a manual trans with street tires, you don't want too much off-idle torque; all you'll do is fry the tires.

cali92RS

I can almost guarantee that RPM range is for a 350 engine. The fact that this is for a 305 means the range is going to shift up about 15%.
All i am saying is that is a pretty stout cam for even a 350. If there is a single person on this entire board with a cam that large in a 305, AND is happy with how their car runs, i would be very surprised.

Dewey316

sean,

all RPM specs given on cams and intakes are basee on a 350. for cam specs add about 1500 RPM to both values, to get a better clue of how it will act in a 305.

that cam is then 3000-7000

Brent

iTrader: (1)

I suspect neither of those cams will match up with 3.42 gears very well.

Something along the lines of the ZZ4 cam would probably work better.

seanof30306

iTrader: (4)

guys, i don't mean to be a jerk, but i really didn't start this thread to get into an argument over whether this cam is too big or not. i'm merely asking people with experience at chip burning whether the greater lsa will offset the tiny difference in duration between the comp cams grind and the hot cam.

mark engle of engle cams, a guy with over 30 years experience with grinding camshafts recommended a .525/.525, .218/.224 on a 114 lsa. it's essentially an lt4 hotcam on a 114 lsa rather than a 112 lsa. he's sold several to 3rd gen 305 tbi and tpi owners, all of whom were happy with them.

i bought my ported zz4 heads from shawn at goautocenter.com. he recommended an lt4 hotcam, as he had one in his 92 305 tbi camaro and was very happy with it.

an engine is essentially an air pump. the amount of air it moves in and out is first dictated by the cylinder volume. the bigger the bore, the greater the cylinder volume and the more air the engine can theoretically move in and out.

next come the heads. when you see flow numbers on heads, they're giving you a theoretical amount of air that can move through the head. so if a head's flow numbers @ .500 are 150 intake and 138.5 exhaust (stock tbi head), that means if you open the intake valve .500" for one minute, 150 cubic feet of air will flow through it. if you open the exhaust valve .500" for one minute, 138.5 cubic feet of air will flow through it.

unfortunately, camshafts (which supply that lift), don't stay open for a full minute. the length of time they do stay open is dictated by the cam's duration; the greater the duration, the longer the valve stays open and the more air flows into the combustion chamber.

when you have a larger bore and cylinder volume, the engine's air requirements go up, so you need better flowing heads and bigger camshafts to feed them. that's why a "peanut" cam on a 406 might be a mild cam on a 383, just right on a 350 and aggressive on a 305. that said, however, a duration of .228/.230 is absolutely not too long for a 5 litre engine. carbed amd maf-efi 5.0 mustangs and 5.0 gms run them all the time. the only reason to not run that much duration in a map system is the map's need for 12" or greater manifold vacuum at idle to work properly.

when your goal is to run fast on street tires (real street tires, not drag radials or d.o.t. legal slicks with grooves cut in them), there are a couple of important considerations. while you absolutely must have a lot of torque to move all that weight, you also must not carry that torque too low in the rpm range ... all you'll do is fry the tires. you move that torque curve upward in the power band by going with a longer duration camshaft.

and brent, the other main thing you do is not run too much gear. again, all you'd do is fry the tires.

my last toy before this car was a 70 chevelle, 400 sbc, turbo 350, 3.31 gear. after a LOT of experimenting and parts swapping, i settled on a weiand single plane intake, an engle .510 lift, .270 (@ 0.50) duration, 110 lsa single pattern cam and big tube headers. that combination was good for consistent 1.7-1.8 short times on goodyear eagle st radials, 12.60s on horsepower and 11.80s with a 250 nos shot. before changing headers and intake, the dual plane/small tube combination couldn't get the short times under 2.2 ... wheelspin. after the swap, 2.0 60' times. swapping from a .489/.224 cam took the short times from 2.0 to 1.8, occasional 1.7s AND picked up 4 mph on the big end. broke the rearend, swapped in one with 3.73s and the short times were right back at 2.0-2.1 ... wheelspin.

there's a reason guys put on vortecs, lt1 cams, 3.73 gears and only run high 14s. yeah, part of it is the 305's 3.767 bore, but while my 400 was being built, i stuck in a stock 283 (3.875 bore) out of a '65 impala 2v with 120,000 miles on it, bolted on a stock quadrajet and intake off of a 350, used the stock exhaust manifolds, exhaust, ignition, etc and ran 14.70s every weekend for close to a year with so little compression the car wouldn't hold on even a mild upgrade without the emergency break (it had a 4 speed at the time).

those vortec heads flow great, but the lt1 cam is too small to take advantage of that flow and the short duration makes tons of off-idle and low rpm torque. couple that with a 3.73 gear and all you do is smoky burnouts that impress the girls but get you wasted by 4 door subarus.

one thing that really annoys me about this board is the way people who don't know that much about what they're talking about make emphatic, definitive statements, then others read them and repeat them until they become "articles of faith".

header size is a perfect example. when i first came to this board, i went all the way back to the beginning of the tbi forum and read all the posts to learn as much as i could about it. the whole reason i bought my firebird was that, while i know a lot about and have a lot of experience going fast with carbs, i was a total newbie to fuel injection and looked forward to the challenge of learning about it. over and over people said 1 3/4 headers and dual cats were overkill on a 305, that they'd kill the bottom end torque, etc. didn't make sense to me. in my experience, shortie headers don't flow nearly as well as full length, and i wanted to bump the torque curve up a few hundred rpm anyway. well, i did 1 3/4" slps with dual cats, 3" intermediate, flowmaster 40 series and dual 2 1/2" tailpipes and i'm here to tell you it didn't hurt bottom end torque a bit. i put the car on the dyno immediately before and immediately after the exhaust with no other changes. i am up in both torque and hp through the entire rpm range. i also believe there's a lot more there through chip tuning.

another misleading "article of faith" is intakes. i saw a number of people trash the gmpp vortec tbi intake. i bought into it and didn't go with vortecs since that's the only vortec intake that is egr capable. now chp is making 230 rwhp with vortecs and that intake and they haven't even tuned the chip yet! i was an idiot for believeing that instead of finding out for myself.

yet another? ultimate tbi mods. i did them. dyno and track before and after. absolutely no difference in hp or et. dyno'd with air cleaner on and air cleaner off. same for the tbi spacer. no difference. zero. the tbi does look cooler, though.

one more? performer tbi intake. way back in 1989 hot rod pulled a 305 out of a camaro, put it on a dyno and compared the performer tbi to a performer carb intake with an adapter. huge difference. performer tbi bit the big one, yet you see person after person on here swearing the performer tbi works great; makes tons of power; they saw a huge improvement (even though they never put it on a dyno or took it to a track).

so really, what i'm looking for here is advice from an experienced tbi chip tuner with a deep understanding of cam theory on whether the 114 lsa on the comp cams grind will make it any easier to tune than the lt4 hot cam.

Dewey316

Which i gave you.

i'll repeat it again.

there is not enough info there to tell you. you need to look at the individual valve events, and determine the overlap. it is the overlap that plays havok with our sensors.

BTW, you got the opinion of 1 cam manufacture. Call Harold Brookshire at lunati, find out what he would recomend. I can't say i have ever heard anyone who manufactures cams, recomend a cam that large for a 305 TBI car. Just like at the doctors office, maybe a second opinion is in order. Take it for what it is worth, You have the answer for your question, some other here just tried to offer up experiance. Some of us here have tuned several EFI cars, with various size cams. we were just giving you an opinion. I assume you will not be needing anymore help, since you are obviously the end-all cam expert in here.

seanof30306

iTrader: (4)

listen dewey, if you want to disagree with me, fine. spirited discussion is exciting and often a learning experience. when you make snide personal attacks, though, you go too far.

BOTH of those cams may very well be too big to be tunable on a tbi map system. i don't know, that's why i asked the question. you'll notice none of the disagreement in my responses had ANYTHING to do with the tunability of either of those cams on a tbi. i don't know, so i kept my thoughts to myself.

however, when people make comments that DO fall within my area of knowledge, i will respond; especially when i believe they're wrong. ESPECIALLY when i believe they're adding to the rash of uniformed disinformation passed around on here by people who simply repeat what they've read or heard.

as far as the effect of overlap is concerned, i agree with you. a wider lsa means less overlap and therefore more vacuum. since the comp cam has just a bit more duration, but a wider lsa, i don't know which cam would have less overlap. i'm thinking the one that does would be more easily tunable.

as far as EITHER of those cams being too large for a 5 litre engine, i strongly disagree. my roommate has a 5 litre mass airflow mustang running a .518/.525 lift, .235/.239 (@.050) cam. he makes 244 rwhp and 262 lbs ft. torque. it's a great driver with plenty of bottom end.

there's a guy in my car club who has an 84 firebird with a carbed 305, unported world products s/r torquer 305 heads and a comp cams xe274h (.490/490 lift. 230/236 duration [@ .050], 110 lsa). with 3.23 gears, he runs 13.40s with street tires, 13.0s with slicks. simulations on desktop dyno have convinced him to go with 1.6 rockers to increase the lift to .526 and to retard the cam 2 degrees. if the program is correct, it should be worth 20+ hp and 20+ lbs ft. torque. comp cams' website describes the xe274h as "very strong mid-range, torque & throttle response, 220+ stall", by the way. a mild street cam.

but you don't have to go that far. go to any mustang board, or even yet, go to the carb or tpi forum on here. plenty of incidences of carbed 305s and maf-equipped tpi 305s running cams that big and bigger. when you and others state either of the cams i mentioned won't work, won't make power to 3000 rpm, won't work with a 3.42 gear, etc., i KNOW you are wrong. there's an example of it sitting in my carport (mustang); i regularly watch an example of it (84 firebird) beat 4th gens down the track, and i've seen numerous examples of it right here on thirgen.org because i took the time to look in forums other than this one.

as far as seeking "more than one opinion"; i have. talked to comp cams. after outlining my combination and giving the tech the flow numbers from my heads, he recommended xr268hr (.495/.503 lift, .218/.224 [@ .050], 112 lsa). he said the airflow of my heads actually showed slightly better results with xr276hr (.503/.510 lift, .224/.230 duration [@ .050] as long as it was run with a manual trans and installed 4 degrees advanced. the only reason he said he recommended the xr268hr over it was the difficulty in tuning it on a map system.

man, comp cam's recommends xr258hr (.480/.480 lift, .206/.212 (@ .050, 112 lsa) for STOCK 305 tbis. when i asked the tech about that, he said it was an "economy cam" designed to work with stock heads, throttle bodies, exhaust, etc. the tech said he routinely recommends the xr264hr (the 305 tpi version of this cam; .488/.495 lift, .212/.218 [@ .050] duration for tbi cars with stock heads but with exhaust, intake and ignition mods. don't take my word for it, it's all right on comp cams' website. http://www.compcams.com/Technical/Cu...ML/128-169.asp just scroll down to page 144.

that xr258hr cam is essentially an lti cam with 1.6 rockers. fine for a stock-headed 305 tbi, but time after time so so-called knowledgable people on here recommending it to people with vortecs. all that airflow going to waste because of too small a camshaft.

regardless of what comp cams says, though, i trust mark engle of engle cams. the last time i took his advice, my car went from 12.10s to 11.80s. not only that, but it did every thing he said it would. improved short times by moving the torque curve up in the powerband slightly and picked up 3-4 mph on the other end because the new cam better utilized the cylinder volume and breathing capability of the heads.

but dewey, what i really don't get is why you'd sneer at mark's advice when YOU said: "i am a BIG fan of the hotcam, it makes great power, and is relativily computer friendly (it will need custom tuning)"

https://www.thirdgen.org/techbb2/sho...ght=lt4+hotcam

the cam mark recommended has the EXACT same lift and duration as the lt4 hotcam. the only difference is that it's lsa is 114, while the hotcam's is 112. that greater lsa means less overlap, more vacuum .... it'll be easier to tune than the cam you're a "BIG fan" of. how is he wrong?

i'm sorry i won't lay down and go with the accepted wisdom of this board when i believe it's wrong. when i do disagree, though, i provide examples and documentation to back up my opinions and invite anyone to do the same.

i also do it without insults and personal attacks.

Dewey316

Ford 5.0s and our cars have nothing to do with each other. through the mustang examples out. a 4"x3" engine is going to behave much diffrently with the same came, than our 5.0's.

My hotcam comment in the other thread, was because he was asking for a 350 build-up. yes the hotcam is a VERY good cam IN A 350. i would say, for the almost everyone here, the hotcam is too much cam for a 305. now, if you have a freshly built, and balanced bottom end, that is capable of 7500rpm blasts, and you are willing/able to try to tune it. then yes, it could make for a very fast 305. BUT, how many of us are really spending the money to have our 305 rotating assimblys balanced, and built to take that kind of RPM?

As for my comment, i am sure you can see why i said that. we offered advice, i explained exactly what causes the computer to misunderstand the information it is getting. I also suggested that it might be more cam than you want. I said that because i have tuned more radical cams in 350s, and less radical cams in 305s. and I can tell you, that if you are looking for lots of mid-range torque, and a cam that will pull to 6k-6500. you need to look in the 206*-212*intake duration range. I know this from person experiance.

JokerRS

I dont know what your intended purpose is. It looks like your trying to build a real fast street car. Sounds like a dumb question doesn't it? The reason I am asking is that while I would like a very healthy running street car, mine is a daily driver and has to be abile to pull the car arround in overdrive at normal highway speeds. I ran a ZZ4 cam with ported S/R torquers and a performer rpm in a 305 ( with 3:42 gears) for a couple years and it worked fine. I had good traction off the line, and I had enough torque in the 1500-1800 rpm range to drive in OD and pull hills with out down shifting. I considered upgrading to a hot cam but decided against it because I felt I would need a lower gear to be streatable.
I ended up putting all the goodies on a 350 shortblock this spring and tuned it. I can tell you the cam acted much bigger in a 305. People are estimating a difference based on cubic inches alone, but you got to consider the poorer flow also.
I guess if your primary purpose is to run at the strip with street tires. then your on the right track. I had to compromise and build a car that would do all the things I wanted to do well, instead of doing one thing excellent.

cali92RS

I know this topic is old and weve gotten a heated discussion over it but there is a topic that was not answered that I would like to know also...
What has more effect on the computer AND on a cam's RPM range, LSA or duration?
Im also getting a cam probably with 224* intake duration (although mine is going in a 350). Im either getting 112* or 114* LSA. Is a car gonna be more streetable w/ 224* duration and 112* LSA or 226* dur. and 114* LSA?

seanof30306

iTrader: (4)

cali,

after not getting a definitive answer on that before, i've continued to research the matter. i spoke to an engine builder the other day who told me the 2 degrees wider lsa would more than offset the 2 degrees greater duration. he explained it in detail to me, but it was way over my head and i don't think i really got it. i'll give you my understanding of it, which could be completely wrong.

both duration and lsa affect vacuum because they affect overlap (the time that both the intake and exhaust valves are open). the greater the overlap, the lower the vacuum.

cam duration is essentually how wide the cam lobes are. the wider they are, the longer the valve stays open at or near maximum lift. if you take two cams with the same lift and duration, but one cam has a wider lsa, the lobes are literally placed further apart from each other, so, while the intake and exhaust valves open and close the exact same amount on both cams, the 114 lsa cam's exhaust valve doesn't begin to open until 2 degrees later in the 360 degree circle the cam travels in than the 112 lsa cam's, therefore giving the intake valve more time to close before the exhaust valve begins to open, reducing overlap. since the additional two degrees of overlap is between the lobes, this has a greater effect on the overlap than the additional two degrees of duration on the intake and exhaust lobes.

WAIT. as i re-read this, i wonder whether i have been given bad information, or whether i simply misunderstood.

if the lsa is 2 degrees wider, then the net effect of the lsa on 360 degrees of cam travel would be two degrees. on the other hand, if there are two additional degrees of duration on the intake valve, AND two additional degrees of duration on the exhaust valve, the the net effect on the camshaft's 360 degree circle would be 4 degrees. if this is correct, then the additional 2 degrees of lsa would have half the effect on overlap as the additional 4 degrees (net) of lobe duration ... wouldn't it? or would it.

sheesh.

i'm going to get an rx7 with a rotary engine so i don't have to worry about this.

Dewey316

Sean did a descent job at explaining. It is all about the overlap. the specs don't tell the whole story. there are diffrent lobe desings, and valve event timing. what you need to do, is look at the cam card, find the timing on all 4 valve events, and then figure the overlap. it is the overlap. NOW, that is just part of the problem. remeber, long duration = more air. which means you have to modify the computer according. once you bump up duration, even if the overlap doesn't change, the fueling and spark needs will change.

the lift figuring is just a ratio.

so, if you have .492 lift with 1.5 and you want to figure the lift with 1.6, you create a ration

1.5/1.6=.492/x

(here is where i assume most of you know how to do this. but i'll still list my steps out.)

(1.6).492=1.5x
.7872=1.5x
x=.7872/1.5
x= .5248 (or in our case, .525

seanof30306

iTrader: (4)

dewey, wouldn't the simplest way to calculate this be to simply first divide the lift with 1.5:1 rockers by 1.5 to get the cam's actual lift, then multiply the cam's actual lift by the new, 1.6:1 rocker arm ratio?

lift with 1.5:1 rocker arms / 1.5 X 1.6 = lift with 1.6:1 rocker arms

in this case:

.492 / 1.5 = .328

.328 X 1.6 = .5248, which rounds up to .525

ShiftyCapone

iTrader: (7)

This way works just as good.

Dewey316

it is the same thing, mine is just the worked out version of it.

same math, diffrent order.

all you are doing is, multipying by one, and dividing by the other.

cali92RS

How does lift affect a cams powerband and streetability?
For example, Im thinking about getting a higher lift version of the CC XR276HR-12 and its specs are 224*/230* with .503/.510 lift and its powerband it 17-5800RPM. But Im gonna get a custom ground one with ALOT higher lift lobes, but same LSA and duration, and my question is how is the dramatic increase in lift gonna affect its powerband?

Dewey316

if it has the same advertised duration, then the duration at .050 might be a hair more. typicly lift is free power. but on the same duration, to get the higher lift, you have alot higher ramp rate. which usualy means the .050 duration is longer. you will also likely need to run heavier valve springs to control the very fast opening and closing of the valves.

cali92RS

\

I got TF 23* heads that can handle .600" lift, so i figure why not take advantage of them and run a high lift cam. Im just wondering how high lift affects drivability and low-mid range torque.

Dewey316

the lift really shouldn't have too much of an effect, you will of course need to give it more fuel, since you will have more air. but the overlap should change. the overlap is what fools the o2 sensor, and causes the vacume drop.

BTW, for everyone who is interested. Comp has a great artical on cams, and how the specs effect things.

http://www.compcams.com/Technical/TimingTutorial/

cali92RS

Thats a good article.
From reading it, i get the impression that faster ramp rates(high lift with lower duration) causes LESS overlap than a lobe with lazier ramp rates, is this true?
Am i correct in thiss ASSumption?

Dewey316

in theory, if the .050 duration is the same, the one with the fast ramp will have less adv. duration. so then less over lap. BUT you have to look at the amount of air let through. it might have less time during overlap, but the lift during overlap, may be higher, allow more charge to pass through to the exuast.

it can get very confusing

cali92RS

I think the overlap would be fine...
Im worried about the punishment on my valve train more than anything this cam would cause.

seanof30306

iTrader: (4)

i thought somewhere in my digging on this i'd been told more lift is essentially free power, but the higher the lift, the peakier the torque curve.

i can't find that anywhere in the pages and pages of notes i've taken, but it's stuck in my head from somewhere.