GM installs 48mm throttle bodies on their 500cu crate motors that produce over 450 to the wheels. Boring a 52 to 58mm is not going to get you a lot, if any HP.

Nobody has mentioned ignition related things, im assuming your wires and plugs are new, is the opti old? How does your car idle, do the rpms fluctuate or are they steady? Is it easy or difficult to start? If your idle is good, that argues against (but doesnt rule out) things like vacuum leaks, lash, and obvious ignition problems. See if any of your headers glow, or if you have a dead cylinder (cold header).

If your injectors are used, they should be cleaned if they have been sitting around for a long time. Fixing that a/f ratio should add some power but the a/f ratio is good where the torque curve dips, so fuel is not the primary problem.

I hope you find out whats going on with it. best of luck.

 

Just because a car can make 500hp with a twin 48mm throttle body doesn't mean it isn't a restriction. A twin 48mm throttle body flows less than a stock LS1 throttle body, but yet the LS1 guys somehow manage to gain power by going to a 90mm setup, which flows more than a twin 58mm. I could make 500hp with stock exhaust manifolds, does that mean they aren't a restriction?

 

What im saying is the 52mm bore is not going responsible for anywhere near the 60+rwhp that is missing. Sure he might gain 5, who knows, 10hp, but that will not solve his problem, for the time being, its just a distraction.

Dyno tuners give mixed opinions on the gains made by bigger throttle bodies. I got a bigger one because its such an easy thing to change, i should have dynoed before and after.

 

i have Jet-Hot Longtubes w/ 3" true duals, dr. gas x-pipe, flo-pro twisters, and dumped before the axle.

exhaust isn't a problem lol

 

thanks for your help, i'll check out the ignition stuff.

opti is about 3 years old, runs perfect. start up is VERY quick, just a flick of the key and it's fired up. injectors were bought used, but cleaned before putting 'em on, they work great.

i'll keep things in mind tho and keep trying to locate the problem(s).

-Ben

 

If this was addressed in the earlier posts Im sorry, but I diddn't have time to read all of the posts just yet.....but was the cam degreed in correctly, and adjusted with offset bushings if nesessary?.... or were they lazy and just lined up the timing marks on the chain (as "some" like to call "straight" up, but it's really not).......a cam thats 4-7 (or more) degrees off, which is pretty common(for a list of varying reasons), could easily be responsable for this kind of power loss(seen it all too many times)........if they did just plug it in( Just lined the timing marks up) then I would start there with degreeing it in the correct way, since without doing that, you will have ZERO idea where the cams installed centerline is at in relation to how that cam was designed to run....it really needs to be installed within 1-2 degrees of the recomended centerline.........Joe

 

it was installed "straight up" and yes i believe they should have it degreed the CORRECT way for it to make most power.

i think i'll mention it to 'em and see if they would check it out and possibly open it up and degree the cam the correct way rather than straight up.