My buddy has an 84 TA with an l69. He had the engine rebuilt with a .030 over bore. The cam is stock, as well as the heads, intake, and carb. He has headers, through a catback.
He ran a 15.6 on the 1320. What would be a good cam for this engine? He would like to hit a mid 14 atleast, so what is reccomended to hit this goal?

 

What heads are they (other than stock, but what castings)?
What transmission, auto or manual?
If, auto, what is the stall?
What gears does he have out back?
Where would he like the desired RPM range to be?
How important are brakes and other vacuum accessories?
What type of cam? Hydra flat or roller? solid flat or roller?
What compression does he have?
Is it a computer controlled carb?

The bolded questions are the important ones. "Stock heads and blah blah" really dont account for much. Choosing a cam is not like picking apples. Its not a case of 'if it looks good it probably is.' Anyone can choose a cam. Choosing a cam that works with your particular setup and needs is a whole new story.

 

He's right, that info is important. Here's one to consider, Federal Mogul #1014R The specs are 204*& 214*@.050 423 and 446 lift on 112* lobe centers. I have this in my car and works well. I could have gone a lot wilder if I wanted. (T5 4.11posi) One other thing, staying under 220* will make the computer happier, although mine is no longer around, I bead blasted the stock aluminum intake and used an early Q-jet and HEI that was recurved.

 

That's a pretty mild cam. But I imagine it works well with a stock setup. The third gen computers are pretty picky too, I hear.

By the way.....tell him he's not going to drop a whole second through a cam alone. One second in the 1/4 mile is a hell of a lot to drop. To do what, assuming he's hooking up good, he'll probably need at LEAST heads AND a cam...... There are other goodies as well, like a better intake setup to satisfy the cam/head combo, and a custom chip burned to make the most of it, etc. You dont just do a $200 cam swap and bam, you're in the 14's....when you have a mid 15 second car to start with.

 

Well, if you don't like it you can always step up to 1.6 rockers later. If you do that make sure that you use a stock type head gasket and (prefferably) not planed heads. In those cases there have been some 1.6's that have caused the pushrods to hit the guide grooves in the heads. You'll need to check that on the install.

 

Just to satisfy my own curiosity.....
Planed heads? Is that like decking a block? And....guide grooves in the heads...for the pushrods? I've only really heard of guideplates. I've only been INSIDE of a Ford motor so I'm just curious to know how the heads on these Chevys are so I'm better informed. Don't mean to cut in on the original poster or his questions

 

*Ok, Ford heads are no brainers from the lash adjustment perspective. Most of the stockers you just install the rocker assembly and you're done. If you change to a solid cam, you have to change the rockers. Chevies don't work that way, every rocker is adjustable, which means you have to...adjust each one. The good thing is that you can use a solid or hydraulic cam w/o changing the rockers. The stock rockers are aslo pretty light (stamped steel) and work well in most performance applications.
*Planing heads =decking, cutting or whatever you want to call it.
*Guide grooves- my bad wording, most stock Chevy heads have no pushrod guide plates, they have slots in the heads to align the pushrods. This is usually no big deal, but if you run roller rockers you'll need the guideplates and along with it, you will have to add screw in studs (the stockers are pressed). If you run a roller cam, and I forget exactly when Chevy started doing rollers, you'll need a way to align the lifters as well.
*In some rare cases the use of 1.6 rockers can cause interference between the pushrods and guide slots. This usually occurs when you cut the heads and/or use a shorter gasket, the best way to check it is to install the rocker(s), then rotate the engine over TWICE, this is because lift/duration can vary between the intake and exhaust lobes and you want to check both.
Hope that helps

 

Stamped steel or "rubber" rockers do NOT work well in performance applications. They are light yes. But they are also quite malleable compared to other rockers. This ability to bend means that it can distort the ratio of the rocker. For example, instead of being 1.5, it could be 1.54.

the lobe lift and duration have very little to do with the angle of the pushrod. You can change the cam profile all you want, but in the end the lifter just goes up and down.

Likewise, alignment of the lifters have nothing to do with alignment of the pushrods.

On the same note, just because you switch to roller rockers, does not mean you have to add guideplates.

 

We're talking generalities here..
*http://www.fl-thirdgen.org/rockerswap.html
and I'll turn the motor over TWICE, thank you.
*Stamped rockers were (one) of the reasons that the SBC was noted as being such a good "revver" back in the 60's. they were cheap, they were light, and they'll do 7grand all day long.
I didn't say alignment of the lifters to the pushrods, but you better have them roller lifters lined up on the cam lobes, and you'll need a way to do that.
*If you're going to roller rockers, especially a complete roller rocker setup,(not just roller tipped) you might as well change out the studs and add guideplates and valve springs as well.
It all boils down to what you intend to do, you can build a 10grand valve train for a 5 grand engine if you want, but the engine in question is an L69.

 

Why were they such good engines to rev back then? Because thats when the engines like the 302 and 327 existed. As you shorten ths stroke, you increase the engines ability to hit high RPM's.

So per your suggestion i should use my factory rubber rockers with my Isky full roller valve train?

 

*Sure, do whatever you want. I'm trying to give this guy a little general info and you're picking the crap out of it. We could do this all night. your my hero, you're the man, you know it all, you were probably were hanging out with Duntov too. Can you give this guy the name of the book you wrote on designing the SBC?

 

no, but I can. it's called "how to **** someone off when you catch them with their pants around their ankles"

anyhoo, wyou're right to a point. the stock **** works with stock components, but I wouldn't recommend using a high performance cam with stock rockers/valvetrain components. it's just not a good idea. this car is probably a daily driver, and need to remain reliable. that said, spend the dough on upgrading the rest of the train a little to. it's a freshly rebuilt motor, so it won't be a waste of time. little more money now, little less headache later.

 

you guys are believing your own BS. the guys building an L69 on a budget. If he listened to you guys he'd be buidling a 383 with aluminum heads, 12:1 NOx and all of the rest of the bling.
By the way, why are your pants around your ankles?...again?

 

For a streetable cam with a reasonable rpm limit, the stock rockers will work fine. They do flex some, but its not much. You really probably wouldn't ever notice a difference.

 

^^^^^

that's a much better response. I wouldn't do it, but he's right; if you don't go nuts with the cam, they'll work for now.

No, I wouldn't build a 383. I WOULD save my money, and spend an extra 80 bucks on rockers, though... so i could upgrade my cam to a more radical grind.


and my pants are down cuz I'm porkin your girlfriend in the *** again.

 

Why do you think your opinion is better than anyone else's?
If I had an extra $80.00 I'd upgrade to a Cloyes tru-roller timing chain.
Oh.. you were trying to**** my girlfriend!!, Now I know what she meant when she told me she met a guy that was showing off an inch worm in a turtle neck sweater.