Have any of you guys tested out the 1.6 ratio rocker arms with the GM hipo cam? Now that my motor's all fastened together, I want to find out if these rocker arms will work with my hipo cam and dished pistons without bashing the valves. I'm sure the fuel system can handle the increased airflow at high revs because I'm running well on the rich side.

Don't know about the any valve bashing, but you'll get some extra valve guide wear if you use 1.6 ratio...

Eric,

A couple of things to keep in mind when using a HiPo cam AND 1.6:1. The result is like (but no exactly) bumping the cam two sizes from stock. You may be creating a problem with the computer. Remember, the computer is running everything based on FIXED tables that include fuel, air, ambient temperature, engine temperature, etc. If your cam to ratical, the computer maps can't properly compensate and the result may be a motor that runs poorly. From what I've heard from this group, the recommendations are to either increase the cam size OR use 1.6:1 rockers... not both when keeping the electronic fuel injection.

If your determined to use both, you'll need to check for valve clearance using the "clay" method. That is: before installint the head(s), make a ball out of clay and place it on top of the piston under the valves. Use you old gasket (it's pre-compressed) and install the head and torque it down. Rotate the crank at least twice (for one complete vlave cycle) and remove the head. Check the clay and make sure there is at least 0.06" (correct me if I'm wrong on this guys)clarance. If so, no problem.

Good Luck,
Roy

Standard, I have also heard the same about valve guide wear when using 1.6 rockers. However, couldn't that wear be mitigated by the use of roller tipped rockers? If you think about how a stock rocker pushes on the tip of the valve stem, I can see that a 1.6 ratio rocker could want to put some pressure on the valve stem tip in less than a vertical direction. A roller tip, on the otherhand, seems like the rotation of the roller tip would not cause the same outward stress on the tip of the valve stem.

I put 1.6 rollers on my 4.3L V6 that is in my boat, coupled with a edelbrock dual plane manifold and a Holley TBI setup, it produces some really good power for a V6. I am opting for some 1.52:1 ratio roller rockers on the 3.4L that I am building cause the guy at the machine shop said i would probably be better of than taking the chance with 1.6:1.

According to Dyno2000 you will gain about 3 horsepower Eric.

But if you use a roller rocker, won't it hit the valve stem a bit beyond center? I would go with 1.52 ratio, just to be on the safe side.

Everyone is assuming that the difference between a 1.5 to 1.6:1 rocker arm is the length from the fulcrum to the valve tip. If this is the case then, yes, you move the contact point out farther on the valve stem and MAY produce more guide wear.

The other way to in increase the ratio is to move the push rod saddle closer to the fulcrum. The same effect is acheaved and you don't move the valve tip from it's stock location. The difference is added pressure to the camshaft. This added pressure, however, would be less than the increased pressure of using stronger valve springs (like in the 3.4).

Roy

My 3.2 thats going into my car is setup with 1.6 ratio rockers and and a high performance crane cam. The total lift is going to be .454 .480. with the 1.6 rockers

I dont think this will be a problem at all for the computer. The thing that computers dont like is going crazy with duration, that's why, the fiero engine will never be a high reving engine with the stock computer. It can't handle the vacuume losses associated with higher duration cams. Higher duration cams are what makes engines give great power up top.

My cam is a 204/216 duration. I wouldn't go any higher on a stock computer.

Also i haven't had any problems with valve guide wear with my 1.6 rockers in the past. I also had hardened bronze guides installed in my heads when they were done-up. Just in case.

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Mike LeCompte
86 Fiero GT 3.2L w/ Nitrous

You would make better gains by going with SI stainless steel valves and smoothing the bowls of your heads than using 1.6-ratio rocker arms.

From what I have seen the roller tip rockers are not much of an improvement. But- the full roller rockers are being under rated by many people. The extra horsepower from using these is not in the ratio of going from 1.5 to a 1.6 but in the fact that valve train friction is greatly reduced. This is a factor that the dyno programs do not take into account.

The GM cam is rated at .454 intake and .427 exhaust lift with 1.5 ratio rocker arms. My heads have had extensive porting work and hardened bronze valve guides installed of the best quality. I don't believe there are any other areas of concern that may yield more horsepower. But if there will only be a gain of three horsepower with the bigger rocker arms, I think I'll just save my money. A little N20 may be in my future.

My machinist Ron from Aeric High Performance has a real engine dyno and he has tested all kinds of Roller rocker arms. He says that you will gain about 5 horsepower on a small block Chevy with 16 rocker arms, not 12 like our six cylinder engines have. That is with the pedestal mount rocker arms like the Crane Gold roller rocker arms.

In fact he says that those Crane Roller rocker arms are junk and I have to agree with him because I have those rocker arms. They look like they were made in China. He says that you have to go with a shaft mount rocker arm system to see a significant improvement from roller rocker arms and those shaft mount systems cost about $1200-$2000 for a small block Chevy.

So Teerrybogin you are right about the Dyno2000 program not compensating for the Roller rocker arms. The program is still very accurate when you compare it to real dyno’s and manufacturers test results. The good thing about Dyno2000 is that it gives you an idea of how a particular camshaft will perform and were it will make the most power in the power band without just guessing at it. I gave a copy to Ron at Aeric High Performance and he was a skeptic just like you until he started comparing actual dyno’s he did with the Dyno2000 dyno’s. He was amazed at how close they came to the real thing. He told me that one engine dyno was within 4 horsepower on a 350 horsepower 350 Chevy he tested and the other was within 25 horsepower on an engine that made over 500 horsepower. That is within 1.1% and 5% respectively.

The thing with this program is that if you do not know how to use it than it will give you inaccurate dyno’s, which are usually on the optimistic side. For example, when I first got the program I tested out a modified 2.8-liter engine and came up with over 190 horsepower. After I figured out how to use the program and I got some real head flow data results that same engine made a more believable 170 horsepower with a camshaft, ported heads, 9.5 compression pistons, headers, and a performance exhaust system.

I get allot of “that program is not accurate” and “it cannot compensate for this or that so it is no good” type of talk here on the forum. If these people on the forum do not know anything about Dyno2000 (not you Teerrybogin) than don’t just say that this Dyno2000 is inaccurate and that the dyno’s don’t count. I get that allot here on the forum when I post a dyno for someone. The Dyno2000 dyno’s do count when you know how to use the program. It is a great tool that has helped me and many others out allot!

Had to get that out.

Not bashing the dyno2000, but by "full roller rocker", I meant the real system (shaft mount), not stud mount. I also have an engine dyno and you are right about the accuracy of the simulation programs, but you have to be realistic in entering the info. I usually use it to compare cams to help make suggestions to customers- they usually want something way too big, so I show them on the sim. what happens when they over cam. It is a good sales pitch.
BTW- My latest project- a 440 "6 pack" picked up 17 H/P and 23 F/P of torque by going with the full roller shaft rockers. The best part was the improvement in BSFC at normal RPM's (1500-5000)An economical hot-rod? NOT!

[This message has been edited by Terrybogin (edited 12-13-2000).]

I'm glad we have some common sense posts on the 1.6:1 rocker topic this time around. About a year ago when this came up, seemed like I was the only one cautioning the use of them in a daily street driven car. If this is a hipo weekend warrior, then go for it.

Eric, my guess is that with dished pistons there will be no valve to piston clearance problems if you use the 1.6 rockers. The computer probably will keep up too. But, there is not enough power gain (in my opinion) to justify the additional expense of the rockers and extra wear that it will cause. The 1.6:1 ratio rockers do change the valve train geometery and will accelerate wear.

Terrybogin is right about the stamped steel roller tip rockers. I've seen several reviews about them and they offer little if any power gains due to the roller tip. The roller is too small and there is too much pressure, so the rollers never roll. If there is any gain, it's because the side walls are stiffer than the stock ones. Howver, the more expensive fulcrum roller rockers HAVE been proven to be friction reducers (which does gain power).

How much would a decent cam cost? Not looking for a million horsepower here, just something to give a 2.8 some more power..
I doubt the car will be racing regularly, so streetability is a big issue..

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steve@fieroproject.com
http://www.fieroproject.com

Cams are cheaper than the roller tip rockers.