Cam Choice

[280zgod]

Hey everybody im looking at MSA performance cams and i wanted to ask if anyone knew which of these two cams would be better for 1/4 mile racing. (intake/exhaust) Cam A which is lift: .480/.480 duration: 274/274 or Cam B which is lift .460/.460 duration: 270/280? All imput is much appreciated. Later.

[Ed]

There are other factors you must consider before purchasing a cam. Someone correct me if I'm wrong.

1. Will you ever use this car on the street to go get groceries?

2. What sort of fuel system will you be running (carbs or injection)?

3. What type of engine do you have (L24,26 or 28)?

4. Which head do you have and does it have any port work?

5. What type of exhaust are you running?

6. What type of ignition system (stock points, electronic, or other)?

7. Have you upgraded the brakes yet?

As you can see these are some factors that will determine what cam will best suit your needs. The more upgrades ($) the engine has the bigger cam you can run. But on the other side of the coin you won't be able to drive it on the street without loosing a couple of fillings.:classic:

[240Zdragon72]

You are right. I also am buying a cam from MSA. Stage II. Has good idel, and the powerband is from 2500rpm to 5500rpm. My auto shop is also going to port and polish the P79 head and do a valve job ( what ever that is). With my bottom end set up with the MSA pistons that have a raised dome for higher pompression, I will also have to buy a 1.0mm head gasket. I'm looking at paying around $2,400 in parts and labor alone. (that is not accounting for all the other misc. parts i.e. timing, freeze plugs, gaskets, oil seals, etc.) I say good luck with whatever you decide to go with. You really dont want to overkill the cam choice. If I'm not mistaken, getting a higher cam would hinder you from driving it daily.

p.s. Don't forget the Header :classic:

[280zgod]

well thats a lot to consider. first off i will be using it daily because im 18 and its my only car for college. secondly its an l28 with a header and straight pipes with the stock FI and minor intake mods but im also planning on oredering the performance throttle body from msa. im gonna definitely say it has no port work cuz the guy who owned it before didnt know what he was doing with this thing, poor baby. I have newly replaced stock points as well and as for brakes havent found a need to upgrade mine. they stop quite smoothly and i usually downshift. im not trying to make this thing into a track car cuz its not my ideal z for that and i dont have that much time or money anyway. ill do that after college. just for now i want a car thats hot on the street with a lil bit more go then its got. just wondering which of these cams would do that for me. the main thing is i want a cam that wont make third gear have such a lag til it hits its power. 0-65 is lightning quick shifting into second is like running through 1sts main power band again but then i hit third and it accels slowly for about 750 rpm then starts to kick up again like 1st and 2nd. just wanted to know if anyone has that same feeling in theirs or not and if a cam with certain specs could compensate for that. wow i talk alot sorry hope you can understand what im saying thanks for the input so far i appreciate it

[280zgod]

sorry to not fully answer your questions ed but i have an n42 head and block with compression of 115,130,130,130,130,90 approxiamately thanks again

[Ed]

Originally posted by 240Zdragon72

My auto shop is also going to port and polish the P79 head and do a valve job ( what ever that is).

Porting = Opening up the intake and exhaust passages by removing extra casting material. Take your finger and run it along the port walls. You will feel little bumps and extra casting material. Now you can have mild port work done where only the rough surface is removed or you can have the port worked and opened up to it's maximum effeciancy (done properly with a flow bench and years of experience).

Polishing = This is where you polish the port wall to a smooth mirror finish. You will hear contriversy on this one. Some people say polish only the exhaust ports for smooth air flow. But leave the intake port walls rough to promote air flow. If you have a smooth surface in the intake then your air/fuel mixture will stick to the walls.???

Valve job = Replacing or resurfacing valve seats. As long as the valve is still in good condition, they will cut a 3 angle surface on the valve (for better air flow). They should also check the valve guide to valve stem clearance.

[Ed]

280zgod, I understand your need for speed. I think all of us do. But I can tell you that a little more is never enough. It addictive first this, then that, it really doesn't stop. Until you run out of money or bolt on mods. Seeing that your on a budget you might want to reconsider the cam. Properly done parts alone will cost you close to $500 bucks. I know MSA offers the cam for $160 but that will only get you started. You will need new springs, rockers and lash pads. You don't want to do one without the other or you might as well send me the money cuz you will be doing it over again. Without new parts you will destroy your new cam.

Now if you have the money to do it right I would go with cam A, .480 lift and 274 duration. Anything hotter and you will start to have problems.

If it was me I would first tend to the # 6 cylinder which seems to have low compression compared to the other five.

You mentioned you had a N42 head. The N42 is a good head and has the large valves. Only bad thing is it has less than desirable intake valve seats. With age these seats tend to "sink" (I can't think of the correct word). And would probably need replacing along with a valve job.

I could go on but I better not. Let me know if you have anymore questions.:classic:

[beandip]

For starters it sounds like you need a valve job . Having compression of 130 on four cylinders and 90 and 115 on two. This is not good. Ed is right the cam is only one thing and the cheapest part of a cam up grade. I think from what you have said , you are asking the wrong questions. I dont think the cam change is where you want to spend your limited dollars. I am in the same situation with the cash flow. Insted of driving by t he speed o meter . Watch the tach and feel where the power band is . When you take the engine in first gear to 4500 and shift , the engine should pull hard and take her to the same in secound , and see what it pulls like in third. Be mindfull of the speed at that gear change and how the engine pulls. I say 4500 only because of the lag because if you try for that number it will likely be at 5000 +. I think you are under RPM ing the engine expecting it to have the tork and pull from too low of RPM . Adjust the valves first because if loose you could float a valve and blow a piston. Especially if you have a weak valve spring in the mix . You havent mentioned how many miles sense the engine was rebuilt. Or a complete valve job was done. With the number given it seems ready for a valve job now or in the near future. Change the rear end gear ratio to a 3.90 to 1 and the car will pull like a woonded bull. These engines will spin high RSs stock but at 30 yrs bad things can happen fast if not in good repair. My 2 cs

[Gav240z]

As Beandip says spend the money on a rear end swap. You want a 3.9 or 4.11 if you can get one.

That will help you accelerate alot quicker.

You could also have a poor ratio gearbox, unfortunately I only know which years of Z in Australia containted the good ratio boxes and diff's.

The good gbox here has a 2.9 first gear.

The other reason for lag could be fuel starvation, I know a friend who had this problem with his 260z the electric pump would do fine for 1,2 gears but 3rd it starved.

I found a 240z flywheel which was lightened and a 240z harmonic balancer(lower front pulley) was a good upgrade on my car , engine revved quicker and felt happier only downside is the engine revs drop alot quicker when you let off the gas.

I would spend your money on getting your car in good tune first see how it's going then decide. I wanna put a larger cam in my motor also but I am unsure of how much streetability it will take from my car.

Research first before spending your money.

FWIW I just bought a set of Toyota 4 Piston calipers in preperation for going faster .

Gav,

[280zgod]

wow i wrote this huge long answer to all three of you and it didnt post it so here we go ill try and condense this time.

Ed, The limited amount of money thing was just when i was talking about building my dream 240 later on in life. sorry to confuse you. i know i need to buy new springs, rocker arms, lash pads, the whole nine yards not just the cam and i was planning on getting the valve job done too. thanks for your advice on the compression and cam choice.

Beandip, yeah shifting from 4500rpm into second gear does leave you pretty much at 4500 rpm but im talking about pushing redline. i mean when i shift from first at 6500rpm into second and then from second at 6500rpm into third. third has a massive setback in rpm there it goes from 6500 to probably 3300-3500, which is out of the cars main power band which i belive is 4400-6500 or higher perhaps. thats where the lag comes in cuz from 3300-4400 or even 4500 its a slow climb then the car rips through the rest of the gear. i wanted to know if a cam could somehow end that little gap. thanks for the info tho much appreciated.

Gav, I'm sorry I don't understand gear ratio numbers. It's nonsense to me. But umm entire 1st gear range is 0-35mph, 2nd gear is 10-65mph, 3rd gear is 25-115 mph, 4th and 5th i dunno ive never dared go that fast. but if from that you can somehow tell what my rear end gear number thing is whether 3.9 or 4.11 or whatever i would appreciate and thanks for the tip. And if 115 sounds crazy for third compared to how any normal Z should be then my speedometer might be off but playing with the police departments radar gun said my speedometer was on so i dunno.

Other info: the car had a valve job or cleaning about 2 years ago and then the previous owner let it sit for a year and then i bought it like 9-10 months ago. and it has a 5spd tranny and 270k miles on it still original engine to my knowledge. but anyway im rambling off again thanks for all your help guys i really appreciate it. late.

PS this one was shorter then the first post i originally made to answer you guys hehe.