Cam Talk

seawalkersee

Registered User
It seems like there have been several threads lately that have either included cam talk or branches over into cam talk. Lots of questions and discussions have muddled up other threads. So, I am starting this one.

The cam is basically the heart of the engine. It controls the valve events. We all know and understand that. The questions come from lift, LSA, and duration. The factory cam does the job of having a smooth running vehicle through the RPM band (which is short imho) for anyone from a 16 yoa to and 80 yoa driver to be able to manage. After you start playing with the profile, you start to get into the questions.

Anyone who has ever built parts from scratch, moodded any existing part, or added something where it did not belong has run into the following problem. When you move/add anything, you must be sure the rest of the parts work around what you have done. When you add lift, you can only go so far. Remember, valves are only so big. Heads can only flow so much, and stock parts are only so strong.

Increasing the cam profiles adds rpm to the engine. By having the overlap change, you move the powerband up, but lose boost. Not that it is totally gone, but if the valves are open at the same time for longer, it pushes through the cyl. As long as your exhaust flows, you will see this.

Add what you want/need. I am not an expert per se, but no dummy either. I have been out of the game long enough that if you ask me a question, I can find the answer, but don't remember it like I used to. So ask questions here as well. There was a good post about cams over on v6power a few years ago too. I will see if I can find and link it.

SWS
 
So what cam/valve/spring/exhaust combo would it take to make a solid 400-450ft lbs of torqu and keep it as streetable as possible if thats possible, oh cars a 94 5spd
 
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My existing cam is a 224/228 & .610 lift with 1.73 RR. To me its a great street cam, it is an animal mid range on up. To me if you want the cam to be a great street machine, more HP on the top end is more important than massive TQ on the low end. Most of these cars have a lot of TQ on the bottom end already

I am disappointed at the very little cam discussion in this thread. There is a lot of things about cam timing I know little about like the lobe seperation, 110, 112,114 How does that affect power, TQ? I know supporting factors like blower type and size, heads are important in figuring what cam is best for each application. It would be nice to understand how much lobe seperation, lift, duration affect power and TQ up and down the power range.

Ken
 
I would also like to know more about what cams perform better in what part of the rpm range for the Thunderbird SC. I understand that you need supporting mods to make any engine combo work and make the kind of power it is capable of. So can anyone answer what cams are available for our engine and the effects of adding the cam?
 
Not really a thread from which to order a cam. You need to know more about the engine than just picking a cam. For instance, what type of powerband you are trying to have. Now that you have listed that, you must look at each eninge setup. You can effectively change the range and top end of the engine with a cam without losing the bottom end. It CAN happen. But usually, there is more to it than that. Remember, when you move one thing, you can change 3. Just the facts of life.

As far as the LSA goes, the more, the more vacuum you have. Thus, a better street cam. But, the more CID you have, you can get away with less and not lose vacuum. Remember, a stall keeps the tranny/car from killing the engine by allowing it to (in essence) freewheel, because it is not making enough vacuum to keep running.

Now, with that in mind, remember, you are limited to the effective range by valve size, piston size, head flow, stroke, and a few other things. Think of it like this. If you have a .7" lift at the valve, the piston will probably kiss it on the back side because in order to use a cam with that much lift, it would have to open for a long time, because of the size of the valves. Make sence?

I totally forgot to link a thread into this.

SWS
 
See, now you guys are far more adventurous than I. I've done most every bolt on thanks to these forums, but the elusive cam head combo... Read all the posts you want, there's gotta be 30 ways to screw that up.

Somebody worthy of such things should do a walk through including a comparison of possible combos.

Dave would probably ask why you'd want to tear it up ;)

Mike
 
On forced induction motors the higher lift could yield better results than longer duration, particularly on the intake side. Notably though, higher lift has more potential problems than increased duration, in particular as valve train rpm rises which can result in more inefficient running or loss of torque.

Cams that have too high a resultant valve lift, and at high rpm, can result in what is called "valve bounce", where the valve spring tension is insufficient to keep the valve following the cam at its apex. This could also be as a result of a very steep rise of the lobe and short duration, where the valve is effectively shot off the end of the cam rather than have the valve follow the cams’ profile.
 
A cam is not what comes first in making a car "unstreetable." Airflow is what makes a motor unstreetable. Everybody here that speaks about cams is acting like our heads flow 300+cfm, and they aren't even close. It isn't very reliable to relate a general concept from a completely different motor and impose it on the SC's motor. Fact is that the SC motor's heads do not flow well; therefore, it's safe to deduce that a larger camshaft can be ran.

Plus, just because a cam can raise potential RPM doesn't mean you have to rev it that high. These motor's aren't NA. If the motor is seeing boost, then it will be making power just as instantly relative to other cams. It just so happens that it won't run out of breath as quickly.

The only thing to worry about is the decrease in idle vacuum for the guys with vacuum brakes.
 
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A cam is not what comes first in making a car "unstreetable." Airflow is what makes a motor unstreetable. Everybody here that speaks about cams is acting like our heads flow 300+cfm, and they aren't even close. It isn't very reliable to relate a general concept from a completely different motor and impose it on the SC's motor. Fact is that the SC motor's heads do not flow well; therefore, it's safe to deduce that a larger camshaft can be ran.

Plus, just because a cam can raise potential RPM doesn't mean you have to rev it that high. These motor's aren't NA. If the motor is seeing boost, then it will be making power just as instantly relative to other cams. It just so happens that it won't run out of breath as quickly.

The only thing to worry about is the decrease in idle vacuum for the guys with vacuum brakes.

Everything you are saying sounds right to me Casey. The motor going into boost and making power just as instant as another cam seems accurate to me. Thinking logically:rolleyes: It seems that making more power through out the power band is a function of more lift, or more duration to allow boost pressure to fill each cylinder on the intake side. It would seem on a boosted motor that power would increase over the whole range not just an extended higher RPM. I can see power coming on at a slightly higher rpm. Myself I dont understand the lobe seperation part very well and where or how it affects power ultimately but than thats why I ask lots of questions. What was your cam specs Casey? Did you feel the car was streetable with the cam you were running?

Ken
 
As far as the SC engine and lift, the GM 3800 with the M90 the guys are running a lot more lift and they are using up to 1.9 rockers. I know its a different animal, but it is a M90 and it is a v6. Some similarities can be drawn. :eek:
 
Not really a thread from which to order a cam. You need to know more about the engine than just picking a cam. For instance, what type of powerband you are trying to have. Now that you have listed that, you must look at each eninge setup. You can effectively change the range and top end of the engine with a cam without losing the bottom end. It CAN happen. But usually, there is more to it than that. Remember, when you move one thing, you can change 3. Just the facts of life.

As far as the LSA goes, the more, the more vacuum you have. Thus, a better street cam. But, the more CID you have, you can get away with less and not lose vacuum. Remember, a stall keeps the tranny/car from killing the engine by allowing it to (in essence) freewheel, because it is not making enough vacuum to keep running.

Now, with that in mind, remember, you are limited to the effective range by valve size, piston size, head flow, stroke, and a few other things. Think of it like this. If you have a .7" lift at the valve, the piston will probably kiss it on the back side because in order to use a cam with that much lift, it would have to open for a long time, because of the size of the valves. Make sence?

I totally forgot to link a thread into this.

SWS

I get your point but maybe I didnt ask the question correctly. What cams that are available for our cars bring on low end power and torque, Midrange and what cams have a top end to high rpm pull out of a motor that has port work, roller rockers, modified exhaust and all of what should be necessary modifications for running said cam to make sure it performs at or close to its optimum performance? I know lift and duration changes where the power comes on etc etc but if somone like myself doesnt want to spend a fortune on a custom grind or regrind cam what are the best options on the open market? For example a 270 cam for a ford 429 460 makes good power from Idle or 1000 rpm to 5500 and with the correct supporting mods greatly increases the horsepower through that range.
 
I know lift and duration changes where the power comes on etc etc but if somone like myself doesnt want to spend a fortune on a custom grind or regrind cam what are the best options on the open market?


Not sure what open market cams you are talking about?
 
I get your point but maybe I didnt ask the question correctly. What cams that are available for our cars bring on low end power and torque, Midrange and what cams have a top end to high rpm pull out of a motor that has port work, roller rockers, modified exhaust and all of what should be necessary modifications for running said cam to make sure it performs at or close to its optimum performance? I know lift and duration changes where the power comes on etc etc but if somone like myself doesnt want to spend a fortune on a custom grind or regrind cam what are the best options on the open market? For example a 270 cam for a ford 429 460 makes good power from Idle or 1000 rpm to 5500 and with the correct supporting mods greatly increases the horsepower through that range.

If your just looking for a low end or midrange cams, they are available from diffrent venders here including Dave Dalke. I have bought a mild cam from him that had great low end power and TQ. My cam now is very aggressive from mid range up to about 6300 rpm and they both were not custom grinds, at least I didnt think they were, and were affordable. Whoever specs out the cam should recommend the correct valve spring, valve train. I have gone with one vender because he built my engine, knows the combination of modifacations and can recommend a working cam. As for all my questions in these cam discussions, I am just wanting to understand the whys and wherewiths of it all for my own knowledge

Ken
 
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Not sure what open market cams you are talking about?

He's thinking about something available off the shelf at Summit or perhaps used. There is nothing available "open market" like that. Comp has some part #'s but they cost as much as a custom grind so there isn't much point in that. Used is ok but since most cams used by SC folks were custom ground, the possibility of getting something that was tweaked for a combination different than yours is probable. This can cause issues, but not necessarily as long as you know what you are getting.

The FI 3.8L is different than the carb'd 3.8L so there is no crossover. Plus carb'd 3.8's were flat tappet so that doesn't really help anyway.

The same principles apply to any overhead valve engine and these engines have a lot in common with a 5.0 or other Ford engines if you want to get more specific.
 
He's thinking about something available off the shelf at Summit or perhaps used. There is nothing available "open market" like that. Comp has some part #'s but they cost as much as a custom grind so there isn't much point in that. Used is ok but since most cams used by SC folks were custom ground, the possibility of getting something that was tweaked for a combination different than yours is probable. This can cause issues, but not necessarily as long as you know what you are getting.

The FI 3.8L is different than the carb'd 3.8L so there is no crossover. Plus carb'd 3.8's were flat tappet so that doesn't really help anyway.

The same principles apply to any overhead valve engine and these engines have a lot in common with a 5.0 or other Ford engines if you want to get more specific.

Thanks Dave thats the question I was aking. It seems like the aftermarket is even limited in the cam area for these cars, We are all very unlucky in this sense but ianyone can go out and buy a mustang and make it go fast, wheres the fun in that lol.
 
http://www.v6power.net/vb/showthread.php?t=25479

I think this is the correct thread. No time to read it...gotta go.

SWS

Good lord, please don't refer to that stuff. Those guys are theorizing about things they do not understand. It seems like a great idea to have this kind of discussion on a message board but it couldn't be much further from the truth.

I'm staying out of it altogether other than to say just what I already have.
 
Thanks Dave thats the question I was aking. It seems like the aftermarket is even limited in the cam area for these cars, We are all very unlucky in this sense but ianyone can go out and buy a mustang and make it go fast, wheres the fun in that lol.

Now that new cores are avalible from Comp Cam we aren't really limited on cam selection and can get a cam anywhere from mild to wild at only a little more than a regrind used to cost. For best results, avoid buying an off the shelf grind and have Dave Dalke supply you with a custom grind.

David
 
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