Rocker Arm Questions

96chevy7.4L · August 31, 2009

Hi guys thought of going to a 1.7 or 1.72 ratio rocker arm on my 7.4L vortec motor (exhaust side only). I have read and heard of truck owners doing this and they claim it really helps. I can understand that it will give the exhaust valve more lift thus evacuating the exhaust gases better. Basically making the engine breathe alot better. I thought this might a be a better alternative then putting a set of headers on. Any thoughts or opinions appreciated. Would it be a better idea to take it one step further and do the intake side as well. More valve lift means more air and fuel thus making more power.

Zembonez · August 31, 2009

I might be wrong here, but it is my understanding that you need to replace ALL rockers with the same ratio when upgrading them.

66nova · August 31, 2009

It is a very common mod to increase rocker arm ratio on the INTAKE side. There is almost nothing to be gained by just doing it to the exhaust side.

Have you done any other mods to your truck? If not, this would not be toward the top of the list, anyway you are considering doing it (exhaust only, intake only or both). Especially, if you are only running stock heads.

Have you done a Custom tune, Headers, Exhaust??? Anyone of them will net you more then the mod you are wanting to do.

66nova · August 31, 2009

I might be wrong here, but it is my understanding that you need to replace ALL rockers with the same ratio when upgrading them.

Jim, a lot of hotrodders run different ratio's on exhaust and intake. But, you will not find anyone that is fast running a higher ratio on the exhaust.

For first gen SBC's(I realize he has a big block, this is just most common) the most common combo is 1.6 or 1.65 on intake and 1.5 or 1.55 on the exhaust.

96chevy7.4L · August 31, 2009

Correction it is a lil bigger ratio on the INTAKE side. But I thought of doing both the intake and exhaust with 1.7 ratio rockers. I have the superchips program in it now but it will soon be a blackbear. 80MM throttle body to which has made the biggest improvement overall. Better throttle response and more torque. And I have the K&N filter of course and a 50 series flowmaster big block muffler. That also will be a magnaflow in the near future. Made the swtich to full synthetics. The rocker arms seemed like the next logical step as opposed to headers. Lil more valve lift will never hurt the big block just make it breathe better.

66nova · August 31, 2009

Correction it is a lil bigger ratio on the INTAKE side. But I thought of doing both the intake and exhaust with 1.7 ratio rockers. I have the superchips program in it now but it will soon be a blackbear. 80MM throttle body to which has made the biggest improvement overall. Better throttle response and more torque. And I have the K&N filter of course and a 50 series flowmaster big block muffler. That also will be a magnaflow in the near future. Made the swtich to full synthetics. The rocker arms seemed like the next logical step as opposed to headers. Lil more valve lift will never hurt the big block just make it breathe better.

Well in that case, it MOST LIKELY will not hurt anything. You may see some improvement, but with stock manifolds, heads, and cam I wouldn't count on too much.

Now, I like the fact that you are talking Black Bear. Justin will take advantage of the changes you have made and actually get some use out of them. On a pure stock truck, Justin would blow the superchips out of the water, but a truck with mods needs him. The superchips was just not designed to work with the upgrades you have.

You are going to love that tune. Make sure you are either doing a in-person tune or a cable tune though, otherwise he won't be able to take full advantage of you upgrades either.