What the point of having 1.6 RR for the intake and 1.5 for the exhaust? Is there a benefit?

 

Depends on the rst of the motor; heads & cam mostly, but other things as well.

If you have heads with a very high E/I flow ratio and a very free-flowing exhaust (well-tuned open headers), it's entirely possible that the exh as a whole might outflow the intake. Basically won't ever happen on a street motor. Under those circumstances, admitting more stuff into the motor may increase available power, since there's no problem in moving more stuff out of it.

In virtually ALL street motors (I'd say "all" but there might be ONE out there somewhere that this doesn't apply to, which would make me a liar, so I'm always careful with "absolute" words like "all", "none", "never", "always", etc.) the exhaust is the main limiting factor to the engine's ultimate capability. Plus, most street cams are desgined knowing this. So mixing rocker ratios is alomst never (again, one of "those" words) productive in a street motor.

For the most part, if you have to ask, it doesn't apply to you; but it's always good to know the theory even if you can't directly use it.

 

My bro n law has them in his 87 IROC. His heads are vortecs with headers. Ill try to get some pictures up later today.

 

Then he has PRECISELY THE WRONG setup to be doing that on.

The thing that sets Vortec heads apart from all others, is their intake port design. They have all this TERRIFIC intake flow. But ..... they have the same sucky exhaust ports as any other stock SBC head. In other words, they have THE EXACT OPPOSITE situation from heads as described above; instead of a very HIGH exh flow compared to the int, theirs is VERY LOW. Therefore the exh need all the help it can get, just to keep up with the int. Not the other way around.

Which is why they run best with cams that have large split patterns favoring the exhaust side.

If I was the betting kind, I'd almost be willing to bet MONEY he'd get 25 HP by doing nothing more than swapping those rockers between int and exh.

No pics necessary; we've seen rockers, 87 IROCs, and Vortec heads, so pics won't really add any new info the the situation at hand.

 

So down to the bare bones. Should my bro n law have 1.6 all across, or have the 1.6 on the exhaust?

 

Depends on his cam.

He SURE shouldn't have what he's got.

No matter WHAT cam it is, he can go faster FOR FREE by just swapping around the rockers he has NOW.

 

springs are a good thing if going to 1.6 rr's

stock springs are down right pathetic and valve float isn't a good thing

 

would my bro benefit even more by having 1.6 intake and 1.6 exhaust vs. 1.5 intake and 1.6 exhaust on his vortec heads?