I have a 92 Camaro with an LO3. From what I here installing 1.6 Rockers would almost be like putting a bigger cam in my engine. I assume factory is 1.5 roller rockers and 3/8"stud. What is involved with a swap like this? What parts do I need? I would much rather do something like this than install a new cam. What type of gain should I expect?

 

I would imagine not much. I mean right now, your cam has x intake lift, and y exhaust lift, therefore the valves have 1.5x and 1.5y respectively. With 1.6 RR, you will simply have 1.6x and 1.6y. Not much extra lift, not a btter centerline, and not any more duration. Plus it'll cost like 200 bux or so...Grab a LT1 cam fer 50. I will be swapping a LT1 cam in this spring, and someone around here said something about a tech article they intened to write? Anyways, just my 2 cents...

 

it makes for a nice gain in performance. i had 1.6's on my car when i was runnign the stock cam. all you really need are the rockers. the stock springs are capable of handlinghte extra lift. it will effect teh lift and duration of th ecam. so look for increased power and a little bit longer power band.
to compensate for the little bit more cam you will want to run a little bit more base timing and add a little fuel.

later
tim

 

Uh, how would 1.6 RR increase duration? They just increase lift, I thought. Now, I havent tried it, so I'll take your word for it about performance, but about how much do you think? Would it really be comprable to the cost vs the cost of a new cam?

 

Well lets weigh out the differences.

1.6:1 rockers / increase lift / ~$200

LT1 cam / increase lift & duration / $50

Seems to me that the LT1 is the way to go.

BTW NJ, how exactly does increasing the ratio of valve lift to the lobe lift alter the grind on the cam to increase how long the valve stays open? That's a new one to me.

AJ

 

1.6 rockers (any 1.6 ratio rocker) will increase valve lift by the ratio of 1.6/1.5 assuming you started with 1.5 ratio rockers. That's a 6.6% increase in lift. If you look carefully at head flow numbers versus average lift during an valve open/close cycle, you'll see that you don't quite get a corresponding increase in flow, but it's close so long as you aren't over-lifting the valve (where no increase in flow occurs).

For a typical Fcar, a 6.6% increase in lift will behave like a 5% increase in flow, and hence a 5% increase in torque and power. On an L03 engine with 170 fwhp stock, that would be 181 hp, or an 11 hp increase at the rpm for peak power. You'll also see a fairly constant level of torque increase of around 5% at all engine speeds.

Do you need to spend $200 on 1.6 rockers? No. There are 1.6 stamped self-aligning rockers for $70 a set, then there are 1.6 roller tip rockers for about $170, and then you have the full roller rockers for around $250. There is a slight advantage to roller- and roller-tip rockers at rpms above around 4500, but the gains aren't huge until you run above 6000 rpm, and even then they aren't huge. Do a search on 1.6 rockers and you'll find a lot of info on them.

The increase from the camswap (assuming used LT1 cam for $50) will be larger because the stock L03 cam is soooo mild even compared to the mild LT1 cam --- so the camswap does provide more bang-for-the-buck, but it involves more swap work and you really need to do a spring swap with new valve springs at the same time.

Lastly, the cam swap plus 1.6 rockers still puts you at under $200 for the rockers (1.6 self aligning, used cam, new springs) so it's all good. If I were doing the job, I'd wait until after I replaced the stock exhaust because that's really a huge source of power loss in the L03. I'd do a cold air intake, the exhaust, and then the cam. Remember too that you'll only be making the engine work better as an air pump, but it won't make all the potential power unless you supply the fuel to match the extra air. That means at a minimum using the vFPR, and the right way is a combo of vFPR with an ECM mod.

If you just slap the parts onto the engine without modding the fuel feed, you'll be disappointed in the results and you might lean the engine out enough at WOT to damage it. FYI. - Ken

 

It will not increase the TOTAL duration, however 1.6 RR over 1.5's will increase the .050" curation slightly. Seeing that the 1.6 will allow the valve to open further (more lift), that means the valve will be at .050" lift at a earlier position on the cam lope than it would if it was running with 1.5's.

Like I said, this is only a SLIGHT increase, but it could be a few degrees.

 

Where can I get a set of those $70 rockers for my '93 5.7 truck? I thought the centerbolt heads required a narrower rocker arm due to the hold down bolts? SC

 

maybe i shoudl have made that more clear, it will increase the duration at .050 lift, sionce the arms have a greater lift they will get teh valve to .050 sooner than the 1.5 rockers will and hold it above that lift longer, thus increasing eht duration at .050. the total duration from open to close will stay the same.

later
tim

 

[QUOTE][

 

Thanks DM91.
SC

 

Finally I see how you guys came up with that. I understand your thinking now. You see things as you are inexperienced, which is good. Kinda like a kid saying "why don't you just set the car down a little so the wheel won't spin when you tighten the lug nuts."

Anyway, your thinking is right. Since all measurements of duration on a cam are taken from the lobe itself, and not at the valve, then yes it would effect the duration of lift at the valve itself.

.050" of lift at the lobe (which is were the duration is measured from) would calcuate out to .075" at the valve when a 1.5:1 ratio is used.

SO, if you were to change all things equally and measure the duration at valve lift, then yes, the amount of degrees of duration would also go up. But not by a 1.5:1 ratio. Hell, if it did then that would bring a 200 deg. duration at .050" to 300 deg., and that's just not right because the degrees of ration are measured at the crank, and the crank spins twice as many times as the cam.

And you can't calculate the amount of degrees it would change because it would vary way too much on the angle of the profile that the lobes are ground on.

But yea, if you increase the ratio to 1.6:1, then the .050" would now become .080" at the valve. Again, only if everything else is changed accordingly, the location that which duration is measured at on the lobe will change, and effect the degrees of rotation and amount of duration.

But that also means that you could increase your duration just by calculating in differently, which is what you would be doing if you measured it at VALVE lift using 1.5:1 instead of LOBE lift which is 1:1.

And on the same token, I think the amount it would change would make about as much difference as putting a mole on Rosie O'Donnell's face and and saying it makes her as beautiful as Cindy Crawford.

AJ

 

Good lord!!!!!!!!! LOL

 

Um... I read somewhere (in one of the magazines) that the .050 was measured at .050" vavle lift. But now IIRC, I remember seeing somewhere that is it measured at lifter lift (or Lope lift).


Heck, now I'm all confused!

Well, I guess this would be the bottom line. If it's measured at vavle lift, then it would increase the duration (again, only slightly). But if it's measured at lifter lift, then no there would be no increase in duration.

As far as seeing things as inexperienced, I disagree with you AJ on that one. I've been working on cars now for over 20 years. I'm not saying I know everything, but sometimes we get conflicting info, or even get mixed up with info at times. As far as NJ Speeder, I don't know his mechanical background, however judging from the many replies full of infomation he has givien, I would not call him as been inexperienced either!

You know, just maybe we read the same artical many, many years ago about duration being increased with larger ratio rockers.

AJ, I'm not saying you're wrong, not at all. Without looking into it deeper, I would probably say I was incorrect with my data. However, I am a little offended by the 'inexperienced' statement.

Later...
Mike

 

Here all of this time I've been thinking that it was duration at .050 valve lift. Is it really measured at lobe lift?

 

there are usually 2 durations listed on a cam sheet
1. advertised duration, which is from the moment teh valve moves from closed until it is fully closed again
2. duration at .050, which is measured from teh time that the valve is .05 inches open until it is under .05

later
tim

 

No.... I'm not saying you ARE inexperienced. What I said was a compliment.

Sometimes I get so involved in the analytical aspect, that I overlook the obvious. The way that you're looking at this is a good thing.

Like NJ said, there are 2 ways to measure duration. One is advertised that can be measured from anywhere on the cam. Some companies pick .006", some .005", some .010". That makes them very hard to compare to each other.

Then the standard (I assume by SAE) became .050". That way all cam durations are measure the same way. So really, advertised duration don't mean ****.

But the .050" is measured from the lobe, not the valve. If it was measured from the valve, then you'd have the same problem that 'advertised' duration gives you. Some companies would use 1.5:1, some 1.52:1, some 1.6:1, etc. It would become very confusing again.

Have you ever set or checked the timing on a cam? Or verified the lift/duration specs with what the cam card say? When checking duration, you place the dial guage on the lifter. Then you rotate the engine and when the lift reaches .050" of lift, then you take note of the crankshaft position by using the degree wheel. Then you keep rotating until the cam almost closes, and is back to only being open .050" again. Then again you take note of the position of the crankshaft. Then you subract the first # from the second #, and that gives the duration in crank degrees. Well there's a little more math involved than that, but you get the idea.

So I'm not saying you're wrong. Looking at it from a different way is all you're doing. And looking at it that way is not wrong, it's just not the same as the way others look at it. Like the Earth spins clockwise if you look at it from the bottom.

AJ

 

I think I am gonna go ahead and get the self aligning rocker arms. I do not have the mechanical experience or the time do all that is involved with a cam swap. I know I could get a used LT1 Cam cheap and that it would make a much bigger difference. But, If I can accomplish some with the rocker arms, I will spend the money and do the easy swap. At least I will still have a roller cam.

Now, I seen 1.6 rocker arms (3/8" drive) for $80 in Summit or Jegs. So, I assume all 87-up Stamped long slot 1.6 rocker arms are self aligning, right? And that is all I would need, plus maybe some valve cover gaskets. Anything else, fill me in.

Plus, the rockers made by Federal Mogul for $64 at SDPC. Part #R-1023R...........where can I get these?

 

i got the proform 1.6 self-aligning rockers from jegs for 170.... very nice... i changed them when i built the engine