Greetings to all. I've been following the discussions in here for a little while, but this is my first serious question and it comes at a time of tragedy for my LT1. Last week I had the unpleasant fortune to get a nice, bent valve in my '96 SS, and after a teardown a few more going-south valvesprings were found, portents of more problems in the future. Now that the motor's out of the car, if I'm gonna make any valvetrain changes, there's no time like the present.

What I've got is a completely stock bottom end LT1 with some (IMO) pretty nice ported stock heads. I had these done by a guy who's now doing heads for Panoz and he did a very good job. 2.00" intakes, 1.6" exhausts, Rev undercut swirl polished valves, Comp 1.6 rockers/pushrods, titanium keepers/locks...all in all a full up head job. With a 58mm throttle body, a ZZ9 cam, and JBA coated shorty headers it made 373rwhp@6000rpm on 93 octane pump gas. This was built about four years ago and I've put about 12,000 miles on this combo. How did I get a bent valve? Well, turns out that the lifters never got replaced when the heads got done, some collapsed, got into premature valve float...you can guess the rest. Note to self: always junk the entire stock valvetrain...at least I stopped the motor before I wrecked a head or a piston.

Anyway, during the last 12,000 miles I've been very happy with the power the engine's made, but the idle's been a bit lumpy for my tastes. I'm in Atlanta and spend a fair amount of time in stop-n-go traffic. Idling along in first gear with the stock cam was easy. With the ZZ9 it's like a bucking bronco.

Which brings me to the penultimate question: has much of anything changed in the LT1 cam arena in the last four years? For a while it was the LT4 HOT cam, then it was the ZZ9...after that I never kept up. I know the Corvette Z06 cam has a nice, smooth idle and gives over 400fwhp with 346cu. in...why can't I get something like that in my LT1 cam? Any cam suggestions? Ideally I'd like to see 400rwhp with my stock displacement motor, but I'm realistic enough to know that'd probably need an unstreetable cam, nitrous, a blower/hairdryer, or a stroker. I've got a redline of 6200rpm in mind, with a desired power peak between 6000rpm and 6100rpm. I wouldn't want to trust the stock bottom end above that.

Any and all advice would be welcome while the engine's sitting on the stands. If you need more info, just ask. I had the head flow numbers long ago, but I've lost them over the years. This will be a solid street car, rarely if ever taken to the track. It weighs whatever a stock '96 SS with T-tops and power everything weighs, but I have invested in a Moser 12-bolt rearend with 3.73 cogs.

Moderators, if this doesn't belong in Advanced, feel free to relocate. It seemed more advanced than the standard LT1 tech, so I figured I'd start here.

Thanks to all!

 

The Z06 sure does make excellent hp with a mild cam because of the great heads and intake. But as you point out, it doesn't have 405rwhp either. Your 373rwhp is quite decent for a stock bottom end. More than a Z06, if that makes you feel good.

I don't know a lot about the ZZ9 grind, it would help me in answering your question if you have the specs and can post them. But if the heads are indeed good (do you have flow numbers?) you can do at least as well and probably better with good drivability. Of course, some of the drivability may be tuning related. How was your car tuned?

Rich Krause

 

TPIS ZZ9 - 212/226@.050, .483"/.520" lift with 1.5 rockers, 112LSA (-5* overlap@.050)
03 LS6 - 204/218@.050, .550/.550" lift with 1.7 rockers, 117.5 LSA (-24* overlap@.050)

I don't know if I've heard the ZZ9 in a car before, but I have heard the LT4 hot cam. Your cam is milder than the hot cam, so I can't imagine too much lope. The Hot cam has -1*overlap@.050.

Overlap is what causes the chop in the idle.

Hmm, if this is too "cammy" for you, but at the right RPM, then you might try a custom grind. Some say the current "best" available lobes are the Xtreme Energy 331x from CompCams.

You might try lobes 3312 and 3314 on a wide LSA. You probably wouldn't lose any hp by going with those on a 115LSA (-15*overlap) and no advance. You will lose some low end torque though.

 

Thanks for the info on the cam numbers. It's been too long since I had the cam installed for me to remember what the stats actually were.

I seem to recall an article in one of the car rags about the new 'Vette cams, how smooth they were and how much power they made. If memory serves, there was a lot of emphasis placed on lobe separation angle and how tight the 'Vette Z06 cam was in this area. Since cams are still something of an arcane art to me (I know enough to know that too much duration is a Bad Thing but not much more), I can't say I fully absorbed the article. Is a tight LSA a power-killer for an LT1?

And the previous poster raised an interesting point: that the Z06 cam can be milder because the LS6 intake/heads are so much better than the LT1 heads. To me, the LT1 heads would seem to have some advantages over the LS1/LS6 heads because of the reverse-flow cooling (less detonation, more compression, more advance, more uniform bore/head temps). Sure, the symmetrical ports are nice but that's more of an intake issue than a head issue. I've heard that the LS1/LS6 power secret is, indeed, the intake. One would think that a custom intake could be fabbed for an LT1 that would mimic the LSx intake (as closely as possible given the non-symmetric ports) and overcome at least some of this, but that's beyond my engineering knowledge to answer. LT1 owners across the nation would likely flock to such an item.

 

Cam selection for LT1's belongs in "LT1 Tech".

Moving to LT1 Tech......

Fred

 

Rich,

The car was tuned on a chassis dyno. The stock '96 computer was junked in favor of a non-OBDII '95 computer which was custom programmed. All the fuel and spark curves have been optimized for these heads and 93 octane pump gas.

Yeah, I know it's more rwhp than a Z06, but I've reached the age where I want a bit of refinement along with all those horses, and might even be willing to trade a few horses for smoothness in the process. Just one long look at the plastic interior of my '96 SS, the poor fit of the kick panels, the overall cheaply made feel of the whole thing...it just makes me long for a 'Vette. Quite honestly I love the fitment of BMW's M3, but you'll not catch me behind the wheel of anything that arrives in the U.S. by boat.

Further, I'm looking at some of the very nice numbers coming out of mildly modded LS1/LS6 motors. 380rwhp seems quite realistic with a stock LS1, long tube headers, and maybe a cam/rocker swap. Nice heads can move that towards the 420rwhp mark or so I'm told. Add to that the luscious (IMO) Vette body, nice suspension, and overall better quality construction and I feel the urge to sell my '96 SS. I've got about $7,000 invested in it thus far above and beyond the $26,000 purchase price.

 

Does anyone have any suggestions for a street-only cam that'll work with an excellent set of ported/big valve heads? Keeping out of valve float at up to 6400RPM? As noted above, I've already got 373rwhp with a ZZ9 cam. Someone has suggested that the LT4 HOT cam is even more radical than the ZZ9.

Is it possible to get 400rwhp out of a NA, non-nitrous stock displacement LT1 and still be streetable and pass emissions? Or have I pretty much just maxed myself out?

 

If you'd like to retain the ZZ9 cam, why not have it ground to a 114LSA? I'd bet your drivability will be much improved.

 

What effects would that have on the power? Would I lose anything, gain anything, or just move the power around in the RPM band?