High Ratio Rocker Arms? (3.8)

[Dominic]

After doing research, I found some High Ratio Rocker Arms for our GM 3800's. These are 1.9:1 ratio and utilize the stock cam...

Stock 1.6:1 Lift Values:
Valve Intake Lift 0.413"
Valve Exhaust Lift 0.408"

New 1.9:1 Lift Values:
Valve Intake Lift 0.490"
Valve Exhaust Lift 0.485"

This increase in lift seems to be a good thing, and without changing the duration (which I hope is okay) it supposedly doesn't trigger SES codes. Gains of 15-25hp are expected, and the kit really isn't that expensive...

Now, thats all the marketing for it, but I have some questions for everyone to think about.

1. Is this okay to do, will .490 lift tap the piston?
2. Is this more cost effective and worthwhile than swapping cams?
3. Are any advantages going to be had without increasing duration?
4. Will this newer rockerarm ratio require higher springrate valve springs to keep valvefloat from occuring?

[slacker69]

Would it be good with like the comp cams. Good ??'s u have. Not that bad of a price. What would through codes

[ March 19, 2002: Message edited by: slacker69 ]</p>

[DominusEtDeusNatus]

That's a huge change from 1.6 to 1.9. Good find. More choices are a good thing.

[Dominic]

Very interesting... After running many numbers through desktop dyno 2000 (if its worth a damn persay) I have discovered that (according to it) there is virtually nothing to be gained by increasing lift... and there is everything in the world to be gained by increasing duration.

Also, the supersix original cam in fact makes more theoretical horsepower (by a very very small margin) than the compcams version, but both are very good. And in fact, by decreasing the Intake Lift and Exhaust Lift back to 0.400-0.450 instead of 0.500+ I find a fairly significant power increase throughout the engine range.

Maybe I'm a looney, but if this thing is right, then I've discovered that changing the lift is a big waste of time. Not to mention that the increase in flow between stock heads and supersix ported heads (numbers are in the supersix catalog, last page), is negligable... Changing the heads to ported/polished better flowing heads yielded virtually nothing, while swapping the cam yielded everything - and yes I compared this with different exhausts and it was all proportional in value.

[slacker69]

humm....zoom right over my head so are they good or bad and u saying getting the heads doon are worthless unstead get these and a cam

[Dominic]

Im not saying the heads are worthless... but desktop dyno 2000 doesnt show any power gains with the increased flow capability of them...

The cams, however, frikken rule beyond belief.

[mike24]

Im a little lost too??? Card could u elaborate on that last part a lil.

[DominusEtDeusNatus]

<blockquote>quote:</font><hr>Originally posted by TheCardinal:
Im not saying the heads are worthless... but desktop dyno 2000 doesnt show any power gains with the increased flow capability of them...

The cams, however, frikken rule beyond belief.<hr></blockquote>

Look closer and you'll find your answer. Increasing just lift and keeping the very small stock duration will not do much. Also the flow numbers from .410 to .490 aren't that far apart even for super6 heads. Exhaust is a restriction also. Once you remove all the restrictions you'll see 7-10tq gain across the board and 7-10hp gain at 6K.

BTW, Desktopdyno is very inaccurate. It's only good for comparing some specs.

[Dominic]

It seems inaccurate in some respects and very accurate in others. I'm just using what I've got :D I was just expecting more of an increase in power with the increase in lift, but I guess I was wrong.

We just need to do some "live" testing on "real" engines and find out what works and what doesnt. I would be interested in finding out how the stock heads perform against the ported heads with and without a different cam, not to mention trying out a few lift values to see if it shows any performance gain.

[DEE97GTP]

Check out the L36 forum on clubgp. I know there are a couple of GT guys that love them. I think they are staggering the intake and exhaust. meaning, more lift on the one or the other, I can't remember which. Seems you lose some low end torque but pick up quite a bit of HP.

I believe www.zzperformance.com sells them.

Is it as good as a good cam? No, but it isn't a bad product either. I have been running them in my car. I didn't notice anthing on the low end, but definately on the topend. it is also alot easier to install than a cam. I just didn't want to go through installing a cam in my car, then removing it when I want to sell it.

And no SES codes.

Also, I got a heck of a deal through a group purchase on them.

DEE

[ March 19, 2002: Message edited by: DEE97GTP ]</p>

[DominusEtDeusNatus]

I would use it with a cam. It gives more options. I can pick a low lift cam with the duration I want and just use those rockers to increase my lift. If I can't find the right high lift/high duration cam.

It seems like they'll do any ratio I want for another $25. That's awesome. Now I can really tailor the cam specs.

[ March 19, 2002: Message edited by: Dom ]</p>

[Magnus]

1. It will not tap the piston in a stock application.

2. No. Cam is more cost effective in every way.

3. Yes, top end will be gained due to increased flow.

4. Not in the stock application.

Like dom said, DD2K isn't very accurate with flow #'s.. to see gains by changing lift, you must have the specs flow'd out in your head section.

Increasing lift IS a good thing.

Increasing rocker arm ratio to 1.9 imho is not. It puts much more stress on the hydraulic lifter (Which I have said FROM the beginning) and because the lifter is hydraulic, actual lift will be lost due to the lifter compressing at higher RPM's.

The cost to switch to roller rockers is not worth it either IMHO. ~550 or so just for MAYBE 2-3 rwhp.. the $$ is MUCH better spent elsewhere.

[veesix]

I have been thinking about this for ~2months nowif you go to clubgp.com and do a search under the general section you will find MANY MANY threads about them, and all the problems that have occured with them. Lets see if I can sum it up from what I remember.

The lift is just a little to big for the stock setup. Their has only been one person that had a propblem with the rockers. I acanot remember which ones he bought, but one of the springs binded on him and caused some problems. I would suggest getting new springs either stock, they are $12.xx a piece from gm, or you can wait for some one to come out with aftermarket springs so you can run a higher lift, but I think that springs are a MUST, especially if you have high milage. but again this is just my opnion. their are people running the rockers on a stock setup with no problems. Even tom at SSM said that if you want the lift to go above .450 you should get new springs.

From what i have heard the RR help on the top end. they help the engine breath better. People have said that they pull hard on the top end.

And me personally, I think that I have decided to go with the cam just because it is eaiser to put it in our cars then the GP, and I think that it would be more benifical, better allaround gains, but this is just my opnon. Go to www.clupgp.com and check it out, see what other have to say. Hope I helped :D

[ March 19, 2002: Message edited by: veesix ]</p>