It's my daily driver in the summers. I don't want a high idle, and definitely don't want the crappy gas mileage that comes with that.

When I get my heads back from being worked/flowed we'll see what my chambers CC at. I'm curious how high my compression is... perhaps that's what's exacerbating the harshness of the stumble.

 

You shouldn't be getting bad gas mileage. My cam has way more overlap than your cam and I have seen 28 mpg in my 3500lb 6 speed camaro. My car idles at 900 rpm too. I get an average of 20 in town and 25 on the highway. Its all in the tune. Overlap produces natural egr in an engine to take up cylinder volume at lower rpms. This can actually help mileage with a proper setup. GM uses egr to their advantage on stock engines for fuel economy.

 

All things considered, it sounds like you are going about it the best way. Replacing the the lifters will give you piece of mind during and after swapping cams. Going through the whole valvetrain will allow you opportunity to check the proper pushrod length, geometry, preload, etc and get it all spot on. Also, not sure how you dropped a valve and were able to repair it with the heads on, but now is a great time to address any concerns. Any improvement you can make to the heads will help you keep the power at the desired level, but stage 3 porting may not have left much on the table.

Your current cam at 225/225 112 has only 1 degree of overlap at .050" lift, so you'll have to go less than that to get an improvement in mileage and manners. An agressive profile will have more duration at higher lifts, at the expense of some additional NVH over a milder profile. With your exhaust, you can probably go to a reverse split to reduce overlap. For example, a 224/222 XFI/XE-R cam on a 114 LSA has 4-5 degress less overlap and still run 149degrees duration at .200" lift.

Best of luck!

 

That's part of my problem, too. I believe the cam I have is a TSP 225/225 and uses XER lobes (the aggressive ones). I have 1.75" longtube headers and between lifter noise and the valves snapping shut from the aggressive lobes, you hear LOUD echoes in the longtube collectors. Sounds like an exhaust leak but I've had the car in the air with the sniffer and everything and it's sealed up tight - no leaks. I've searched and read that long tubes allow you to hear valvetrain rattling away more, and even moreso with aggressive lobes. You gotta remember this engine setup is in an RX7 that looks pretty exotic. I don't want it to sound like a cammed up El Camino... here's a pic (yea yea, the ricey spoiler is from the PO, and is coming off this winter):





PatG recommended a milder road-race type lobe. If it weren't for wanting milder lobes, I'd probably just throw an LPE GT2-3 in the car and be done with it. People have made 360whp with it on stock heads and if I can make 390-400whp with my heads all freshened and optimized, I'd be stoked. I think I remember Pat saying he could go more aggressive on the overlap and lift than the GT2-3 and still have it behave like one at idle. That'd be ideal. Aside from that, I'll probably heavily wrap the longtubes and see if I can muffle the valvetrain noise some more.

I know it sounds like I'm defeating the purpose of having a big V8, but trust me, the difference between the limp-gutless-no-torque Rotary that was in the car is night and day, even on a bone stock LS1.

Thanks for the advice!

 

Forgot to address this.. The car had dual valvesprings on it before... strange ones, too.. the inner spring was more like a square shaped coil - like old small block springs - kind of like linguini coiled up instead of spaghetti. Anyway, a outer coil near the end of the spring broke and the inner spring kept the valve from hitting the piston. Or perhaps it did hit the piston, but couldn't fall into the cylinder and cause massive damage. I wouldn't be surprised if I saw some eyebrows on the piston top of that cylinder.

That's part of the reason I'm taking the heads off.