Ok bought a 91 5.0 conv, it has a bbk cai, flowmasters and headers. I am installing bbk x pipe next week, have already purchased gt40 upper and lower intake and 70mm throttle body. Just purchased gt40 heads and I am not too knowledgeable with rocker arms, I believe the stock ones are 1.6? Would it be beneficial and why to go with 1.7? Not really sure what the different measurement does. I plan on staying with the stock ho cam for now. Thank you in advance for the help!!
Need Rocker Help
- Thread starter tonymwc
- Start date
Congratulations on the fox and welcome aboard.
1.7s are an upgrade. Is the intake a tubular or an explorer? The convertibles need a little more gear, auto or stick?
Whats the end game, dailey driver or weekend warrior?
1.7s are an upgrade. Is the intake a tubular or an explorer? The convertibles need a little more gear, auto or stick?
Whats the end game, dailey driver or weekend warrior?
It's a ratio, it's that simple. Increasing the rocker arm ratio increases the lift.
So then,...... math time. If a given cam has a lobe that that measures .300" lift,..the 1.6 rocker increases that lift at the lobe to .480" at the valve. A 1.7 rocker ratio will increase that to .510". So it adds .030". After that, it becomes a supporting equipment issue...Will the springs tolerate an additional .030" lift? Is there clearance to allow for that?
I
So then,...... math time. If a given cam has a lobe that that measures .300" lift,..the 1.6 rocker increases that lift at the lobe to .480" at the valve. A 1.7 rocker ratio will increase that to .510". So it adds .030". After that, it becomes a supporting equipment issue...Will the springs tolerate an additional .030" lift? Is there clearance to allow for that?
I
I run full roller 1.7 rockers on a stock cam. Love it! Mine are ford racing pedestal type. Like Mike says, its good to upgrade other valve train stuff too. I'm running trick flow valve springs and push rods too.
On your parts combo of 70mm tb and explorer intake I have suggestions. First you will need a 70mm egr spacer to match the tb. Also, the stock opening on the explorer intake is 68mm. To avoid turbulance caused by the step facing the intake charge, you'll need to slightly port the explorer intake opening to at least 70mm. Also check gasets size to make sure they are not smaller than the opening. You can carefully enlarge a stock gasket or buy a larger one to begin with.
On my explorer intake swap, I used a modified explorer tb which is 65mm. I got a 65mm egr spacer to match and left the intake opening at 68mm.
On your parts combo of 70mm tb and explorer intake I have suggestions. First you will need a 70mm egr spacer to match the tb. Also, the stock opening on the explorer intake is 68mm. To avoid turbulance caused by the step facing the intake charge, you'll need to slightly port the explorer intake opening to at least 70mm. Also check gasets size to make sure they are not smaller than the opening. You can carefully enlarge a stock gasket or buy a larger one to begin with.
On my explorer intake swap, I used a modified explorer tb which is 65mm. I got a 65mm egr spacer to match and left the intake opening at 68mm.
It depends on your final setup. Specifically, if there has been milling done to heads or block and what thickness head gasket you use. Also what type of rocker arms you use matters too. If you use screw in studs and stud mount rockers, the pushrod length can easily be adapted for by adjusting the rocker are nuts. If you use stock pedestal mount rockers, the only way to make adjustments to them is to add shims between the pedestal mount and rocker pedestal.
I dont know what your case will be so I can't tell you what length you'll need. In my case I used stock length pushrods in two different setups, both pedestal mount 1.7. During one setup I used shims to make up the difference for head milling. The shims allowed me to obtain proper lifter preload. The second time, when I rebuilt the bottom end I used thicker head gaskets, .020 thicker than stock. Doing this I was able to assemble without using shims and gain proper lifter preload.
When you put it all together, at that point you'll need to determine if you can get away with stock length, or need to order something different.
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