The Money Pit

I put the 1.60's on the other week and finally decided to drive to work today.I haven't reset the timing or carb yet to try to tune it any better,but it seems the bottom end isn't what it used to be.Got half a mind to put the 1.50's back on.Guess I'll tweak it a bit first,but I was wondering if anybody else has run into this.

SteveG75

1.60 rockers increase lift at all points. So, you actually increase the effective duration at .050" lift by 3-4 degrees. This could be contributing to the loss of low end.

Only my $0.02.

Fevre

You could experiement with using the 1.5 in the intake and 1.6 on exhaust and vise versa. This might gain you some power without sacrificing the low end.

Smokehouse69

Tune it up and make sure everything is dead on then test it again, before you change them out. Adding the rockers effectively increase your valve lift about as much as you could expect from a one step cam change. You were already running a cam with pretty good lift, so you have probably moved your torque/hp curve further up the rpm scale. Running your TH350 (I don't know what sort of stall you're running) it is probably pretty luggy below 3000 rpm.
I noticed a post yesterday that linked to a test page from Comp Cams with many of their cams listed, each one was tested in the same engine on a dyno. The hp/torque charts gave you a good look at when the power really kicks in for a specific cam. I can't find the post or the link now! I also saw a post that let you figure your lift with 1.60 rockers vs. 1.52 rockers, I can't find it either. I participated in that post chain, and the search feature can't find it either.
I'll keep looking and get back to you if I find it.

adam

I think this may be the page you were referring to:
http://<a href="http://www.compcams....ynoSheets/</a>

It's funny, as some have pointed out, that the xe262 gets better
numbers than xe268...

Too bad they don't have the standard series on that page.

With a 406 with AFR's I'm surprised you saw a difference - doesn't that
motor smoke em?

Smokehouse69

Here's the link to the post about the Comp Cams, http://forums.corvetteforum.com/zerothread?id=453587
Or, you can go directly to the Comp webpage and see all the cams on the dyno. http://www.compcams.com/information/...fts/DynoSheets
The profile of your XE284 with 1.60 rockers is effectively as follows.
.507/1.52=.334 * 1.60 = .534
.510/1.52=.336 * 1.60 = .537
Your duration is probably increase a couple of degrees at the most, so the cam profile your car is even more radical than the XE294-H10
So it doesn't surprise me that you notice a difference in low and mid range performance.
A 3000-3500 rpm convertor and slightly steeper rear gears would probably turn your car into a tire melting monster, but it probably would be a beast to drive on the street.
As it is I bet it pulls like crazy above 4000 rpm!
PS you interested in selling those rockers? :D

gkull

You need higher compression to regain lost lowed TQ