-I have what I think is a stock 1973 400 engine with #48 heads. Does anyone know if 1.65 ratio rockers will fit without interference? The lift on the cam with the 1.65 rockers would be .528. -Is there any way to tell without removing the heads?
Unless it came with 1.65s, the holes will have to be elongated. You can check by watching the pushrod while rotating the engine with the valve covers removed. Also, be sure to install threaded studs instead of press-in if your going to run that much lift.
Chances are good...no. As said, the pushrod holes in the head castings need to be elongated because they will be running closer to the stud. They more than likely will not fit under stock valve covers either. You will either need to run taller covers or space them up a bit. I run two rubber gaskets and they just clear. No oil drippers either.
Has anyone dynoed their car before and after installing 1.65? The reason I ask is that most of the people I know who have Pontiacs say that they gained very little performance by going to the 1.65 rockers. I'm just wondering if it's worth it for a street car?
I think it has alot to do with the whole setup. Basically how well everything breathes. I had a few guys tell me that it might run better with the stock ratio rockers. Or at least on the intakes because I'm running a cam with so much overlap.(I think that's why) Probably not worth the trouble on a stock motor.
I think it has alot to do with the whole setup. Basically how well everything breathes. I had a few guys tell me that it might run better with the stock ratio rockers. Or at least on the intakes because I'm running a cam with so much overlap.(I think that's why) Probably not worth the trouble on a stock motor.
Stock cams were pretty low lift given the duration. They also don't have much overlap when compared to aftermarket grinds. So if it's true that for a tight LSA it's not a good choice, then for a factory cam it should be a great one.
I've never seen dyno numbers where the only thing changed was the rockers. So no data to say it's good or bad. But how many do actually change just that and then evaluate the power? And if they do, did they do tuning adjustments to compensate and optimize?
Jim Hand seems to love larger rocker arms and he's running a station wagon in mid-11s with 3.42 gears, full exhaust, ported factory heads, modified factory non-H.O. intake, factory spec. cam (although this varies), and a 850 Qjet. So I tend to think he knows what he's doing.
