cam questions

[propit21]

need a little help maybe someone can explain. Just recently change cams and heads on a motor of ours. What is the differance the the cam perviously in the motor had 106 intake centerline and the new one has a 102 intake center line what does this mean and how does it effect the motor?

the first set up we were told was to big
dart 230 heads on a 383ci motor
performance products single plane intake
cam spec for this
gross valve lift .596/.608
@ .20 292/296
@ .50 262/266
valve timing @.050
open closed
int. 25 btdc 57abdc
exh. 59 bbdc 27atdc
lobe lift .3730/.3800
lobe separation 106.0
intake centerline @106.0

second set up
world 220 heads
same manifold
gross valve life .562/.584
@ .20 291/300
@ .50 259/269
valve timing @.050
open closed
int 27.5 btdc 51.5 abdc
exh. 65.0 bbdc 24.5 atdc
lobe lift .374/389
lobe separation 106
intake centerline 102

which is a better set up for a 383 lite wieght forged rotating assb. with 6inch rods and forged pistons. In a superstock/prostock 3000lbs 3 link car. Runs on 3/8 mile track most the year and two smaller tracks twice a year. Hopefully someone can explain the differance in the two, the driver feels that the first set up had more power and is lacking power on the smaller head and cam setup.

[perfconn]

Listen to your driver.
The first cam is to big but has the right spread between the intake and exhaust duration.The second cam has the right intake duration but has too much exhaust duration.Neither one is exactly right.You need something more like a 256 intake duration and a 260 exhaust duration at. 050 lift and it needs to be ground on 104 for that heavy a car.Oh yeh,put the 230 Darts back on,much better head.

[stockcar5]

nobody will be able to give you accurate advise without knowing if you run gas or akly and if its a 2bbl or 4bbl

[propit21]

its gas, 750 cfm 4 barrel holley. Like to turn around 7200 rpm

[sj valley dave]

Hey ProPit21, when we were running the East v West Super Stocks in CA, we had a 14:1 360" SBC with Dart 215's and Bill H recommended the Crower 00308 FT cam. 252*/260* @ .050. LSA 105* .600/.586 with a 1.7/1.6 rocker. Back then we had to run a gauge legal 4412 and it pulled real hard to 7800 or so. For a few late season races we put on a 750 cfm 4 bbl and that thing pulled real hard up to the 8200 chip we ran..We never really got out horse powered and we ran against Randolph, Denman, Lee Jensen, Bell, Corwin and all those guys...3000 lbs w/ driver on leafs...

[perfconn]

Dave is right on for a two barrel cam but you need a little more intake duration for the 383ci and 4 barrei.

[DANNY]

Terry,

How would that cam work on a 360 flat tops with 50cc pro toplines 235cc runners on a 2 bbl gas?

[perfconn]

Too big.You need a 250-254-104 Turn it 7200-7300 with a guage legal 500.It will work better with a 6.200 rod.

[DANNY]

Lol anyone that wants to trade for a smaller set of heads lol... But seriously thank you for the info.

[propit21]

the first cam was a custom grind from comp cams the only problem is to get the cam and heads to flow to make total power we need to be around 8500 rpm is what dart told us which is not what we want to do.

as for the other its jr motorsports prc 109 cam that they run in all there mod motor which a local motor guy told us he runs in all the motors he builds for mods. He also told us the big 230 dart head flow way to much for our engine and was not getting peak performance out of it.
so we switch to a set of 220 worlds heads we had and put in the 109 cam and the motor seems flat right now but we did add more timming to it and it ran a little better but not the pull we were excepting to have, it has 36 degrees of timing right now. the other thing that was mention was we need to run a different gear maybe. We run a large 3/8 mile tighter corners and long straights. we are running a 6.14 gear with 265 dirt bozz tires and turn 7000 rpm. we were told to run a 6.20 gear now and that would also help?

[perfconn]

My best 360ci 2 barrel engines have been with 200cc iron eagles with a 2925 intake and 6,200 rods.Angle mill the heads as much as possible(.285) and run flat top pistons.You will end up with about 33cc combustion chambers and 15-1 compression.Turn it 7200-7300.Use a cam thats 250-254-104 and you will have as good as it gets.
By comparison my best steel head 4 barrel engines are the big bore short stroke with a 6 inch rod,RHS raised runner heads with 245 cc intake runners,256-262-106 cam,1.9-1.8 rockers,turn ing 8000-8100rpm.You will see about any 23* head start laying down after 8300rpm.

[DANNY]

Lol how bad will it be with the heads i have and 6.0 rod with same cam and intake as you said?

[perfconn]

Not too bad,probably be down about 20hp over the 6.200 rods and 200cc heads with more compression.It would be cheaper to build than the angle milled Darts but budgets always control what you can afford.

[propit21]

so the best thing to do is to put the big darts 230 heads back on the motor we have go with a different cam. a little smaller then the first one we got from comp cams? We would only like to turn around 7000 to 7200 rpms.

With the set up we have right now which is the second one i mention it just lacked power what it seems like. Not a whole lot of get up and go could you please explain why you think it is. all we changed was the heads went from 230 darts to 220 worlds, and changed cams. This is in a 383 with lightweight egale crank and rods, dome pistions about 11.1 compression i believe is where we are at. What do you think we need to do to as far as heads we have already either the 220 or the 230 and what size cam would be good to get us in the rpm ranger we would like to be in?

[perfconn]

The Darts would be a better choice between the two sets you have.The reason the second cam was weaker was because of two reasons.First it is way too big for the low rpm that you are trying to run.Second is the 10 degrees of split on the cam is not letting the engine have any static compression because the overlap on the cam allows the compression go out the exhaust.I don't think you will ever be very sucesful trying to run that low of rpm in a four barrel class but if you insist on doing it then you need a cam for lower rpm.The 250-254-104 should be about as good as you can get but don't be surprised that you are not competetive.

[let-r-eat]

What compression ratio? Just saw in the thread above you thought 11:1? What chamber size on the two? The 230 is the better head. Way too much cam for a 383 at 11:1.I would try to get 13:1 with the darts. 252 intake .620 lift or so. 258 exh .600 lift or so. 107 on intake centerline with 109 LSA. Use a lobe with as much area on those numbers your rockers will stand.

[sj valley dave]

When we ran the 14:1 360 we used Dart 215, angle milled with 2.05 and that Crower cam, but turned it 7800 rpm with a 4412...We used a 13:1 377" with Dart 230's with 2.08 intakes, but it had a smaller roller ion it and it pulled hard to 8200...Used it for the end of season "open" races in CA...Trying to limit the RPM's to 7200 is going to be tough as Perfconn mentioned...It will be hard to get the grunt out of a 383 with only 11:1 compression and be competitive with the WCSS cars...

[perfconn]

The reason I say to keep the 360ci-4412 guage legal engines to 7200-7300 is simply the numbers.You can figure the air requirements of any engine by using the following formula:ci÷2x max rpm÷1728 therefore- 360ci devided by 2 equals 180 times 7200 equals 1,296,00 ci per minute.To get cfm divide that by 1728,which is how many ci is in a cubic foot,which is how carburetors are rated.You end up needing 750cfm for a 360ci @ 7200 rpm.So you see that even at 7200rpm the 4412 which is rated at 500cfm is really not enough carburetor.A Holly 4412 is exactly half the size of a Holly 750 so everything being even it should only be rated at 375cfm.
This is not revelant to the original question but very helpful in classes where carburetor sizes are dictated by rules.

[propit21]

perfconn WOW you got this stuff down to a science. Thanks for the help. another quick question is there any place or any way to tell what a cam is if you have no paper work on it? can you send them to a company to copy the cam or do it yourself? hope you understand what am asking,

[perfconn]

You need more rpm to go with the cam you have or use a smaller cam if your going to keep the rpm low.I don't use anything but Comp Cams and yes they have what is called a cam doctor.They can tell you everything about any cam except the valve lash.Usually cost about $50.00,another reason these dummy engine builders don't need to waste their time grinding the numbers off a cam.