Cam selection

65fastbackresto · May 25, 2007

After reading huge article on cam selection on Popular Hot Rod website, I get some ideal numbers in mind for my cam. I call a profesional cam grinder, ask him what would work best, without ever even asking me my vavle sizes, he spits out his PERFECT for the job. Shouldn`t this scare me?

rbohm · May 25, 2007

that depends, did you tell them what rpm range you are planning on driving in most of the time? or did you tell them what you wanted from the engine? when people ask me what cam they should choose, i dont care about valve size, port size etc. i want to know what rpm you are going to drive in, or what application the engine is for. you tell me you want a street engine, i recommend a cam that will work best in the 1000-5000 rpm range. you say a street/strip car, then i say the 2000-6500 rpm range. etc. a cam is going to work in what ever rpm range it is designed to work in regardless of valve size, port size etc. i would however also recommend other parts to select depending on what you tell me you want.

65fastbackresto · May 25, 2007

According to the article

One of the most important numbers is the LSA, which you cant know without knowing the valve size.

http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/index.html

Check that out, I`m trying to use some of the info in the article to spec a cam. Let me know if any of it makes sense.

I`m a new car guy, no experience in this field, but I`m trying to smarten up so to speak, I`m open to any input.

brianj5600 · May 25, 2007

65fastbackresto said:
I call a profesional cam grinder, ask him what would work best, without ever even asking me my vavle sizes, he spits out his PERFECT for the job. Shouldn`t this scare me?

Who did you call? I am not sure that reading an article equips you with everything you need to know. Some people use average cross section on the ports and flow to design a cam. I have a lot of respect for Vizard, but simplifying to valve to bore is over-simplification IMO. There should be at least 2 pages of info for a cam request.

57fairlane · May 26, 2007

65fastbackresto said:
One of the most important numbers is the LSA, which you cant know without knowing the valve size.

how do you figure?

Camshafts are just one of those forever hot subjects.
Yes, you can pick a decent OTS cam but there will always be those that shout "custom". Unless you want every last ET, or care, or have some extra cash laying around, stick to newer grinds (Comp XE series is a very good line) and look for something with lift that will fit the heads.

rbohm · May 26, 2007

mr vizard is a brilliant man, i know because he was one of my instructors in college. but you need to look at what level he is talking about when it comes to how he picks parts for engines. he is usually talking about a 10/10th's race engine, or an extremely healthy street engine that will see alot of race track time. if you really do want the maximum amount of power available from a particular engine design, then follow what david tells you to a "T". one thing though is you WILL need alot of dyno time to properly tune the engine combination. if you can afford it, go for it. another one of my instructors, denny wykopf, designed a computer program that after inputing everything about your engine, it selects a cam for you. you can then take the print out to your favorite cam grinder and have a custom ground cam made. it includes everything from ramp rates, to lobe lift, to lobe center angles, etc. if you want to spend the money, be my guest, but i can select off the shelf cams that get you close to what these guys tell you is the optimum cam for your application. and i should be able to because they taught me well.

Max Power · May 27, 2007

65fastbackresto said:
After reading huge article on cam selection on Popular Hot Rod website, I get some ideal numbers in mind for my cam. I call a profesional cam grinder, ask him what would work best, without ever even asking me my vavle sizes, he spits out his PERFECT for the job. Shouldn`t this scare me?

I don't want to sound condescending, but you are very new to all of this. I see threads where you are questioning the opinions of people who have been doing this for a living for years. One magazine article and the consensus of a bunch of people on the internet (some very knowledgeable, some less so) doesn't necessarily arm you with enough information to question these people.

If you doubt this mans cam selection, ask for testimonials from people using the same grind. Seeing as he made the recommendation with confidence, it sounds as if he might have made this grind before and has happy customers. Also keep in mind that there is no right answer for all of this. There are a million ways to skin this cat, and many answers are simply based on personal preference.

D.Hearne · May 27, 2007

I pick mine based on what and how I want the engine to perform and what the compression ratio is. Lots of others do as well. If you want a lopey idle but someone picks one based on your combination of engine, vehicle,etc, you could end up with something like a mild RV style cam. That may be the optimum cam for the combination, but if you wanted a lopey idle, that ain't gonna cut it.

bnickel · May 27, 2007

D.Hearne said:
I pick mine based on what and how I want the engine to perform and what the compression ratio is. Lots of others do as well. If you want a lopey idle but someone picks one based on your combination of engine, vehicle,etc, you could end up with something like a mild RV style cam. That may be the optimum cam for the combination, but if you wanted a lopey idle, that ain't gonna cut it.

ooh ooh ooh, i know, i know...compa cams new Thumper series that's the cam you'd need for this application.

D.Hearne · May 27, 2007

I called an old friend yesterday to give him an "earfull" of the 331 I just stuck in the Comet. It's got a Ford Racing Z303 with 1.7 rockers. Hedman longtube headers and 24" x 2-1/2" collector extensions for an exhaust. After hearing it ove the phone, he asked me if I'd bought a Harley. It's got a healthy lope, but the power comes in at 1500 rpms with the high rise dual plane 3x2 and the trio of Holley 2 bbls. And it'll idle in gear (C-4 with an unknown torque converter) at 700 rpms.

65fastbackresto · May 29, 2007

I`ve done it again.

I wasn`t trying to be condescending to anyone, what I need is input because a bunch of you guys have already crossed this bridge. The only reason I called the cam grinder at all was to see if he was gonna ask me some of the questions that the article I read said was imperative to cam selection. When he didn`t ask me the vavle size, thats when i put this post up.

Yall know I dont know anything about these things, you can tell that from the stupid questions I ask.

I used the info in the article to see what numbers they considered as "optimized" and then called the cam grinder to see if his numbers were even close, and they actually were very close. I`m just curious how he got his numbers.

I dont have the money to spend on a pro ground cam, I`m looking for an off the shelf cam that will do the job.

FYI, the guy never even asked my compression ratio either.

But, according to the article, I need an LSA of around 110, and a duration of 278, I never could figure out the lift.

Do those sound right?

rbohm · May 29, 2007

assuming this is for a street engine that you want to have make decent power, check out the comp cam 268h high energy grind. if that isnt enough for you then the 270h magnum cam from the same company is a good choice.

Max Power · May 29, 2007

65fastbackresto said:
I wasn`t trying to be condescending to anyone, what I need is input because a bunch of you guys have already crossed this bridge. The only reason I called the cam grinder at all was to see if he was gonna ask me some of the questions that the article I read said was imperative to cam selection. When he didn`t ask me the vavle size, thats when i put this post up.

When I said "I don't want to sound condascending", I was referring to me, not you.

65fastbackresto · May 29, 2007

rbohm

Ok, some other guys have recommended a Weiand stealth dual plane intake, those 2 go together pretty well?

My ignorance shines alot when I ask stupid questions,yall just please keep in mind I walked into this car with NO prior car knowledge. I not only want a car that runs good, but I want to know WHY it runs good.

FLStang · May 29, 2007

If a cam grinder can give you a detailed recommendation for a cam, without ever mentioning or asking Compression Ratio, he's pretty much nothing but a salesman. Walk away.

Sure you never mentioned "otherwise stock engine" or something similar that would let him understand that you were looking for a bolt-on performance cam, with no other mods necessary?

Jan

65fastbackresto · May 29, 2007

I will be running almost 10 to 1 comp

Thats not stock is it?

bnickel · May 29, 2007

65fastbackresto said:
Thats not stock is it?

could be. for instance a 69 351 4v has 10.7:1 compression from the factory and a 69 351 2v has 9.5:1 from the factory.

D.Hearne · May 29, 2007

65fastbackresto said:
I wasn`t trying to be condescending to anyone, what I need is input because a bunch of you guys have already crossed this bridge. The only reason I called the cam grinder at all was to see if he was gonna ask me some of the questions that the article I read said was imperative to cam selection. When he didn`t ask me the vavle size, thats when i put this post up.

Yall know I dont know anything about these things, you can tell that from the stupid questions I ask.

I used the info in the article to see what numbers they considered as "optimized" and then called the cam grinder to see if his numbers were even close, and they actually were very close. I`m just curious how he got his numbers.

I dont have the money to spend on a pro ground cam, I`m looking for an off the shelf cam that will do the job.

FYI, the guy never even asked my compression ratio either.

But, according to the article, I need an LSA of around 110, and a duration of 278, I never could figure out the lift.

Do those sound right?

I for one couldn't advise you one way or the other, not knowing what the engine you want this for is built of. Maybe I missed it, but you haven't mentioned any specs here.

65fastbackresto · May 29, 2007

Motor is 302 bored 30 over

Edelbrock Performer RPM heads 1.90 intake 1.60 exh
C-4 tranny with shift kit
Roller rockers
headers of some kind, haven`t got that far yet.
been told carb between 600 and 650 cfm, Edelbrock has been mentioned cause I want the big secondarys so it will moan when I stomp on it.
I have an 8 inch rear with low gears (not sure how low just know its taching a bunch at 70 mph)

car is just for fun, I`ve never had a hot rod and I`m pushing 40, want to make the most I can of the 302 without spending megabucks.

Jimmys66 · May 29, 2007

65fastbackresto said:
I wasn`t trying to be condescending to anyone, what I need is input because a bunch of you guys have already crossed this bridge. The only reason I called the cam grinder at all was to see if he was gonna ask me some of the questions that the article I read said was imperative to cam selection. When he didn`t ask me the vavle size, thats when i put this post up.

Yall know I dont know anything about these things, you can tell that from the stupid questions I ask.

Asking about cam selection is NOT a stupid question.

I've owned my mustang for almost 20 years and I'll be asking the cam question for the next motor I build too.

My first build, which is still in the car, has a "stupid big" cam shaft. When building it I asked a "professional engine builder" what he rec. I bought a .586 .608 solid lift cam with 104 deg of lobe separation.

This is a street car........

The questions you ask may make you feel stupid, but the only stupid questions are the ones you don't ask.

Cam selection

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