Cam Theory

[Sickness]

Just curious....What cam would you recommend for me? Since the car is going to be driven daily, I guess I should put a Hydraulic Flat Tappet in it. I'd like it to sound as wild as possible. It's going to be a 383 with 10:1, Sporstman II ported heads, Vic. Jr, 750 carb, B&M Holeshot 3000, TH350, 4:10s, 28" tire, total vehicle weight being about 3250 w/ driver. I'd like to break into the 11s. What do you think?

 

[540Malibu]

Just curious....What cam would you recommend for me? Since the car is going to be driven daily, I guess I should put a Hydraulic Flat Tappet in it. I'd like it to sound as wild as possible. It's going to be a 383 with 10:1, Sporstman II ported heads, Vic. Jr, 750 carb, B&M Holeshot 3000, TH350, 4:10s, 28" tire, total vehicle weight being about 3250 w/ driver. I'd like to break into the 11s. What do you think?

you'll be fighting the converter for a good launch, but i'd go hydraulic roller with .050 duration somewhere around 240/250 int/ exhaust with lift in the mid to high .500's with a fairly tight lobe seperation, 108-110.

 

[Anonymous]

I have noticed that almost all the engine builders in the Popular Hotroddings BBC engine builder contest have been running tight LSA - 108 seems to be the most used. I've read alot on this subject & this seems to be a very over looked aspect of the cam shaft profiles.I know these builders are very very good & try alot of combos. to end up with the best all around power :!: - any input to this magic 108 LSA ? kirk

 

[Brute Force]

A 108 L/C isnt really a magic number so to speak. If you could get any of the really good engine guys such as the one who are real competitive on the EM Challange to talk to you about their cams, they would tell you its all part of a combination of this such as selecting the opening and closing points of the valves, duration @.050, lobe design (symmetrical or asymmetrical) and overlap. I dont want to say that the L/S is simply a by product of all of these, but they all go kind hand in hand. It all kinda matters on the rest of the lobe.

Look at Prostock cars, at this time they are running between 114-117 LSA. And I've heard that Top Fuel are getting up around 116-118.

Their not magic but todays cam profiles seem to work well at the 108* LSA in an RPM and induction limited engine that 99% of us run when the cam is match to the rest of the engine and intended use.

 

[Anonymous]

Ok, I am no expert so correct me if I'm wrong , on big blcoks going with a 108 lsa is for the guys that want low end torque and do not have problems with traction issues and also the 108 lsa has more of peaky torque characteristics, I use a higher lsa to get rid of some low end torque to help with traction as higher lsa creates a more smooth torque curve. Another thing with cam selection I see people running to small of heads and run a huge lift cam, not realizing that There head doesn't flow better at a higher lift due to small runner size, also the other way around where people run a head with to small of a cam therefore creating a low velocity in there intake runners causing puddling etc. One thing I am not really up to date is cam selection in regards to compression/lift/lsa/duration

 

[Anonymous]

Ok is my combo matched up pretty well? I havent fired it up yet. If I need to change anything just let me know, this is my first real build

350 bored .040 over
flat top pistons with 4 valve reliefs
stock vortec heads with stock springs
comp magnum 270h grind 12-211-2
double roller timing chain
long tube headers with 2 1/2" dual exhaust and turbo mufflers
gm performance dual plane intake
holley 600
stock hei
200r4 trans with stock convertor
3.42 posi rear


The plans for the car is just a weekend cruiser and maybe go to the track on occasion, anything I need to change?

 

[Anonymous]

Are those heads 76cc chambers?

 

[Anonymous]

64cc and 1.94/1.50 valves

 

[eldabo]

The guy that built my motor said, That if you want to run anything over a very small shot of n2o 125 -150 that you need to wider lsa mine is 110 is that true? His reason was that cyl pressure is to high and you run the risk of lifting the head with a tight lsa.

 

[eldabo]

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