fastlt1

iTrader: (4)

Buddy of mine was talking old car and how bad azz it was had a "3/4" race cam those specs are based on 1.5 rockers. Since we use 1.7 stock rockers all our specs are based on 1.7 rockers. What would the specs be on a cam equivalent for our cars.

squarles67

Based on my calculations you'd have a 27/32 race cam using 1.7 rockers instead of 1.5.......

AnotherWs6

iTrader: (17)

I did the same calc, looks like you'd be running a 27.2/32 race cam bu using the bigger rockers.

ChopperDoc

Are you all talking about duration increase or lift increase? I'm a bit confused as to what you mean by 27/32...

I had a neighbor that used to build some pretty bad *** cars. He too used to talk about the 3/4 cam. However, as I understood that by asking him, the lift was .750 (3/4"). If that lift was at a 1.5 ratio, then wouldn't the cam be a .500" lobe? Using that number, at 1.7 it would be .850" lift... Geez. That's insanity. Wonder that the reliefs look like... Or are the pistons just molded around the valves? lol.

ChopperDoc

Lmao, damn you internet explorer. I had no idea there was a picture in his post until after I posted mine... LOL

fastlt1

iTrader: (4)

I guess my question is does rocker arm ratio effect duration or lsa. I know it does lift

fastlt1

iTrader: (4)

And lift would be .564 on this cam with 1.7 rockers

ChopperDoc

Yes, it will affect duration, but not where it starts or stops per-se. It is a ratio, so lift is affected along the entire slope. LSA should remain the same, since centerlines will still be in the same place. Seat to seat will also remain the same. What really changes is advertised duration @ .050, since that will occur at different places due to the increase in lift.

I'm not a cam master, so I could be wrong, but in my head that makes sense. If the lifter isn't moving, then I don't see how the rocker is going to change where the lobe begins or ends.

ChopperDoc

When I wrote my first post I could not see the picture due to shitty Internet Explorer. I know there are actually 3/4" cams out there, but on heavily modified race engines. I was just assuming you meant one of those... I even saw one in an LS7 Yukon Denali (.750 lift, no ****). I talked to the guy and that's what it sounded like. His buddy had a Z06, and he said his truck could keep up with it. I believed him too. It was furious sounding. He also had cutouts, so it was even more awesome. It was the coolest SUV I have ever seen, so far.... Lol, never thought I would say that.