i'm in the process of timing my cam and i figure i might as well put a mild one in there now while it's apart. my car is a 1974 scamp with a "225" engine and automatic transmission. the whole car is stock at this point. i am thinking of adding these modifications: a mild cam, shave the head about 80k, 2 1/4 single exhaust with a free flow muffler, 2 bbl. carb. with manifold. thats about it because it is my daily driver. i am getting just over 16 mpg. with a stretched timing chain and if possible i would like to keep it there if not do a little better. i need to ask for help in selecting a cam right now so i can button her up and getting running again. thanks!

You need to ask yourself What are you looking for from your engine. Higher top end, Better low end torque or best economy. Then look for a cam that will give you what you want.

Comp cams has a nice selection of moderately priced cams for the /6 in the big PAW catalog. I installed their 260H in my 85 D100. It is designed for /6's that pull trailers or RV's. I lost some top end but she pulls like an ox. Thats what I wanted.

They have other grinds that perform diferrently. And if you can't find what you want from Comp, there are many others out there that grind cams for the /6.

_________________
There is no problem that cannot be solved by the proper application of thermo nuclear weapons

first off i am replacing the timing chain and gears because it's all real loose. the car has been totally gutless as far as torque. top end is pretty weak also. i don't have any idea how it will run with a new timing chain or having timed right, but i would go for more performance and stay at 16 mpg. if i get more mpg. in the process that will be great. thanks!

Your stock 74 cam is a pretty nice piece also. It is the biggest stock cam that came in a slant six. Just make sure that it is timed correctly because I think that some of the later engines had retarded cam timing due to emissions. Just make sure that you have a good, high quality timing chain and gear set that does'nt have those damned nylon teeth.

_________________
82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Frank emaled me and asked for some help with this after reading one of my other threads. I have little time right now but will give my 2 cents...

He asked about the comp 264s as a possible option. It is and would probably work well for him. But in the Comp catalog right there next to the cam listing, they are telling you it would work good for towing and have a good idle...well, we know cam companies are conservative!!!...so this should tell you right there that you could get more power and efficiency by careful optimizing.

So assuming that 264 degrees duration open to close is a good target for reasonable rpm range, idle quality, and low end torque...what else to do.

Well, this cam has 220 degrees duration from when the valve opens to .050" lift, to the point it closes to within .050" of fully closed. In other words...220@.050" lift. It also has .440 lift.

Nothing is wrong with this, and would give a nice little boost over stock without hurting any performance elsewhere...and you could most likely install it straight up without degreeing it and have success.

But...we know that /6's are very low compression, even with the head shaved .050 or a little more, you are looking at 8.5:1 that you can count on...I say this because most of you will never cc your heads, or check the deck, or figure your gasket thickness...so factory tolerance and other isssues leads me to predict about 8.5:1 after minor head shaving.

If we go very large on the cam two things will happen, the intake valve starts to close later and later as the piston travels up the bore, reducing effective compression and hurting lowend performance, the other problem is overlap, which the more of it, the more it hurts drivability, but the more it helps power in certain rpm ranges based on a large number of factors specific to your exact combination of other parts...such as exhaust system, header type, collector type, porting work, valve grind style, combustion chamber design, and to some extent, even the type of intake.

For more info see the "cams sanitized" post:

http://www.slantsix.org/forum/viewtopic ... highlight=

Most of the overlap issues can never be known without much testing on an individual combination, so we just use rule of thumb, and cams in the 260 range haven't enough to worry about.

so basically, I believe any cam in the 260 degree open to close (advertised) duration, can be used in a slant (at least a 225") without any issues that could hurt...except maybe grandmas car with air and 2 something gears and a trunk full of last years newspapers etc...

But...if I think that...do I think the comp 264s is the right cam...NO.

Why...it is a lobe designed for mild use on a .875 lifter in stock engines and applications that can still go towing or get good economy. And knowing how conservative comp is with their catalog grinds...

So what if we go to the lobe specifications page...

Ahhh, now here is some interesting stuff...scroll down to the flat tappet section...and theres alot of lobe designs that don't look any better, some even look worse, some lobe types don't even have designs small enough to work for us...

Now before I go on...I must put a caveat out there...

I am willing to put up with more crap from tuning and drivability issues than most people in exchange for power...so there is some killer, and better lobes that would pertain well to this app or even better if we wanted to go 10 degrees larger open to close...so I am going to temper my choice here somewhat to take into account the first time nature of this for Frank. Also, I don't want to push too much valve lift because then you run into other issues with springs, valvetrain setup...etc...So I will keep it to .500 or less lift.

So the lobe I like for Frank is...well...it would be easy to just pick one and here you go...but not yet.

Here is a list of choiices, all of which I think would work well for Frank. These are as I found them, scrolling down the list of lobes by section.

Xtreme Energy solid lobes...

Lobe # Open/Close .050 lift

6053 262 224 .479

These lobes are designed to be quiter, personally, I love valvetrain chatter...it is sweet music to my ears, but if your one of them people who likes quite...then these lobes are for you. This particular one is a safe upgrade from the 264s, probably barely feel the difference though.

6084 268 230 .501

Another one for the quite folks, better, but increasing open to close size is not what we're after.

Max Area lobes

6211 263 236 .497

Thats starting to look really good.

6212 267 241 .500

ooooohhhhhh!!! yeah touch me that way!!! I need some cold water!!!!!

Max area low lift

6192 266 240 .468
6232 266 240 .483

MH Solids

6252 262 236 .518

Now these are just a few of the choices, and lobes around each of these in the lists are also possible candidates, but this is all we need for our purpose here...

I don't know what exhaust is planned, or final gear ratio...but if it was me choosing for FRANK then my choice would be:

Max area low lift
6232 266 240 .483

Now first, this isn't the only choice we need to make to order this cam, and second, it is not a choice I would make for me...but isn't far off, and is better for Franks situation...let me explain:

I believe the biggest issue here is lift. Although, .500" lift is not that much, it is alot based on slant 6 spring choices for a stock head, and for simplicity sake for Frank...he didn't tear into this to build something that would take a rework of the entire engine. So I felt it important that he could easily find springs that would control those heavy valves and last forever. Also, low enough to not worry about hitting a piston, third...he should be able to stick with stock retainers and such. Fourth, there is some (but not much by me) concern over port velocity, When you go to really aggresive lobe profiles, the valve can open so fast to such a large volume that port velocity at low engine speeds suffers, thereby hurting lowend performance. But these cams are still small enough that I don't think this is an issue at all for considering in this particular thread. It might have an impact on a more aggresive engine buildup for street use, but I don't think its a problem at this level.

That said, it is another reason I chose the .483" lobe over other, higher lift versions.

Keep in mind that all these lift figures are for before lash. So a .483" lift lobe, lashed at .020" will have .463" net lift at the valve, ignoring any valvetrain geometry issues that might change this somewhat.

So of all the choices for lobes, I felt that the 266 duration was very managable for his app. The 240 degrees at .050" lift tells us that this has a lot of area under the curve. TWENTY degrees more duration at fifty than the 264, with a trade of only 2 degrees open to close.

This lobe should make at least 10-15 more top end HP just by ordering it over the standard 264s...and without hurting the bottem end performance enough to notice.

What now...lobe separation. When they grind the cam, how much overlap do you want? Well to simplify things...I'm going to say that for a four speed, I would probably go 108. But for an auto trans, I would go 110 with stall convertor, or 112 with standard convertor. 112 will help it idle and overcome the friction of a tight convertor, but the trade is increasing the top end rpm a little. Ah!!! But what if we advance the cam...well, I would degree this cam in at least ten degrees advanced at 102 intake centerline.

102 because we really want 104 and the timing chain will stretch two degrees in the first couple thousand miles. I know this (at least about Pontiacs) from testing different installed centerlines over a season and measuring changes in timing change stretch and how it affects cam timing. It retards it...

This 104 centerline will bring the rpm range back down about the same amount that spreading the lobe centers increased it...so its a wash. But it will close the intake valve sooner, helping the low compression engine to retain good low end torque even with the addition of a larger cam.

So if you were to call comp cams today...you would order a Chrysler Slant six cam core, with the #6232 lobe on both the intake and exhaust, Grind it with 112 lobe separation, and with an intake centerline of 102. If there core allows them to cut that much advance, then thearetically you don't need to degree it or have cam keys around to set cam timing...but you should still check it.

So a week after you make the order...this cam shows up at your door.

Now if it was me and my car...and I would probably want another 10 degrees open to close...but if I wanted a 260 something cam...

I would run the Max Area # 6212 with 267, 241, .500

But there is actually some better ones with more lift that I would try, But I will be using thin stem valves, reshaping the valve spring pocket for different spring dia, changing the installed height to be taller, using lightweight retainers and other components, ordering custom length pushrods...etc...

But my choice above would be what I would run on a stock engine with headers and good exhaust, with a decent intake and carb.

Some others might chime in to talk more about valve springs...since I haven't built a head yet for a slant, I can only talk about what I see on my project head, but some others here probably have some practical input on the limited choices for springs available and there use in a stock configuration cyl head.

I hope thats understandable logic that I wrote. I am very pressed for time all of a sudden, and my propensity for long posts can really screw up my day if I'm not careful.

Gearhead

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"

Gearhead: thanks for taking the time and for sharing your knowledge!! i re-read "cams sanitized" and i think i understand a little more each time i read it. as usual you have a WHOLE lot of good information. by the way you pretty much described my "Scamp" perfectly. 1974 Scamp, automatic transmission, stock everything, rear differential tag says "276", bought from an elderly school teacher. only thing missing is the trunk full of newspapers. i will either go with 2"+ single exhaust or "Dutras" dual exhaust with free flow muffler(s). i really like your "what else to do..." i always know i better hold on, warn the "ole" gray matter... he's not done yet... not by a long shot!! i'm sure you'll get some replies on this post. i wanna read what else come up. gotta get going. thanks, again!!!!!!!

Wow! You can fit a lot in with little time! I wish I could type that fast. Great response. Thank you. It helps others of us "Newbies" reading along too. Thanks for taking the time.

_________________
Rob

I’m Mater
The Kentucky Poser

well, i thought a lot about calling " Comp cams" and talking to their technical department and asking them about the springs for this cam to see if they could help me (probably not?). if i understood right, this cam is a "special order" cam not going to sitting on any shelf. about the springs.... i'm thinking this may be uncharted territory. thanks, again.

I am only home for a few minutes...it is a custom grind, usually takes them two days to complete it and ship it. Whichever lobes you choose they can tell you which springs will work. I didn't mean my choice for you would be difficult for springs, only if we chose a cam lobe with lots of lift like over .540 or more. For the choice for you they should be readily available.

Got to go

Karl

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"