Gt40p Roller Rocker Choice

sen2two · Jul 7, 2014

So I'm setting up my gt40p heads and I am deciding between 1.6 and 1.7 roller rockers.

I have an e303 cam which has a .498" lift. With the 1.7 rr's, lift will increase to .529". I also have the gt40 upper and lower intake with 65mm TB as well as 1 3/4" MAC Long tubes. I am also porting the heads as well as my upper and lower intake. I do not plan on shifting past 6000 rpm in fear of splitting my block.

Will my set up breath enough to make the 1.7 rr's worth the cost?

Ps. I am coming from the rotary engine world so I am still learning cam tech. Where does lift actually benefit the rpm band? Or is it better everywhere since it let's more air in?

sen2two · Jul 8, 2014

Also, the car does have nitrous on it. I only spray a 65 shot at the moment. But I plan to at least double that.

Basically, I am wagering the cost of roller rockers vs. the cost of milling the heads and trying to figure out where my money is better spent.

The bottom end is a completely stock 91 302.

84Ttop · Jul 8, 2014

1.6 rockers get my vote. You may run into ptv issues with the 1.7 rockers. Either way it is your best interest to check

sen2two · Jul 8, 2014

Can you elaborate on why you would vote for the 1.6 rockers?

I plan on checking my PTV clearance when I do the swap. But after a lot of searching, there are quite a few people already using this set up with success.

Success referring to it working. Not referring to it being the best choice for the best results. Which is what I would like to find out.

Gearbanger 101 · Jul 8, 2014

I vote 1.6RR's too. If you bought the car that way, or got the combo super cheap, then go ahead and get the 1.7's

But generally, its a better practice to control lift with camshaft selection, not rocker selection.

Why on earth did yo go with the 1 3/4" Long tubes? Did you get a deal on them or something? Waaaay more header than you'll ever use with a set of GT40's.

I wouldn't worry about splitting your block. You aren't making anywhere close to enough power to do that. Even if you were to take it past that, the stock ECU shuts the party down at 6,250RPM anyway......not that it matters since that camshaft start running out of steam in a hurry right around 5,500RPM.

84Ttop · Jul 8, 2014

Exactly as Brian said, I believe that your camshaft profile should dictate your overall lift, not the rockers. While it is a common occurrence to see others bolt on 1.7 rockers it is usually due to that person not changing the camshaft at that same time. If you are changing the camshaft then I vote for picking an appropriate one and staying with the 1.6 ratio

sen2two · Jul 8, 2014

The E cam was installed prior to me buying the car.

The 1 3/4 headers were to good of a deal to pass up. Plus I know they fit the P heads without any modifications at all.

So besides it being a better practice to let the cam dictate lift, is there a reason why 1.6 is better than 1.7 ratio in this scenario?

I'm still confused as to why less lift with the 1.6 rockers would be better here (assuming it is)... Will it create turbulence? Reduce intake velocity? Lose power at the top or bottom end without benefiting the other end?

84Ttop · Jul 8, 2014

Your cylinder heads only flow so much air. That being said, more valve lift isn't always the answer. Your combination all has to work together if you expect it to perform well. Adding more lift to the cam in this situation will likely not yield any more power thus the recommendation to stick with a 1.6 rocker. Ideally if you are looking for more power then look into a set of TFS or AFR cylinder heads. I personally wouldn't invest a lot of money into the gt40 heads

Gt40p Roller Rocker Choice

sen2two

I've been lubing and pulling it all morning

sen2two

I've been lubing and pulling it all morning

84Ttop

They make new pistons every day, so why worry?

sen2two

I've been lubing and pulling it all morning

Gearbanger 101

Straight Outta Locash

84Ttop

They make new pistons every day, so why worry?

sen2two

I've been lubing and pulling it all morning

84Ttop

They make new pistons every day, so why worry?

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I've been lubing and pulling it all morning

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I've been lubing and pulling it all morning

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They make new pistons every day, so why worry?

I've been lubing and pulling it all morning

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