gira

Wow, there can be a million opinions here. Making a Z car handle well is not that hard. Making a Z car handle great is hard. Generally speaking, the compression and rebound adjustment is a great tuning tool, but only applies to corner entry and exit. It's job is to control the speed at which the weight transfers. AND, the driver has to be experienced enough to say, "the car understeers too much at turn in", or "I get on the gas and the front end doesn't work." Many people don't constantly run the car on the edge for long enough to accurately feel these things. I prefer the Koni race shocks. They have been reliable and we put them on the shock dyno and they're surprisingly consistent. When you lower a Z, other things happen. I can't get my race car to push. Our cars exploit the fact that they really dig out of the corners, torque and rear grip. I'd ditch the rear bar and switch the spring rates to have a higher spring rate in the front. UNLESS your car pushes real bad already. Most Z cars inherently oversteer, but it really depends on how much you have changed the ride height and other things. Front grip has a lot to do with how bad the roll center had gotten when you lower the car. Our EP car has a roll center spacer that's about 5 inches tall. Swaybar adjustments are always the easiest way to make quick adjustments. Hope this helps, Greg

Z Folks, I will be in Atlanta next week on business, 2/25-2/26. I will be there Tuesday and Wednesday evenings. I travel quite a bit on business and haven't met very many Z guys outside my area. Would love to have a beer and talk about cars. Let me know if you're up for it. Greg Ira 2013 SCCA National Champion

Here's One, a 1900 lb. Orange Z, Orange Crush. Greg Ira

GK666. SCCA won't cry, they just won't allow you to do it. Or, like someone else said, you may enter an all inclusive class like ITE. If you are trying to better yourself, this isn't the way to do it and the Z car would make short food out of the MR2. For great racing in SCCA and a host of race lengths to choose from, build your Z car to the ITS rules. Power isn't everything and being close to 200 hp ain't nothin to sneeze at. Now, on to NASA. You may time trial your car and compare to the MR2, but wheel to wheel may be difficult. They have a division where you begin in a certain class and end up in another class depending on how many and what type of modifications you have. Remember, the true sanctioning bodies have a job to keep parity. Nobody wants to see a particular car stink up the show week in and week out. So, to be competitive in NASA and SCCA, you must be able to learn the rules and have fun. Otherwise, just look up your local High Performance Driver Education companies and do track days with them. Greg Ira

Hey Guys, I'd like to know which "big brake" set up works and with what mods. We are in the 2:06's at VIR and run stock ZX brakes! The only difference in this and the big brake set up on most cars is the floating caliper. I am particularly interested in how to make the Arizona Z car type brake set up work. It's amazing that I have these huge brakes and have to pump them all the time. I have a vintage Z that I put the aftermarket brakes on. Just the slightest load on the front spindle causes the pedal to almost go to the floor on the next brake use. Lookin around for ideas and so far have, floating rotors, bearing shims, strut gussets. Thanks Greg Ira

280zzzz, I can make 200flywheel horsepower all day long with all stock internals, including cam, pistons, rods, etc. This is in IT prep, so almost no headwork either. It's race engine knowhow, assembly, cam timing, a combination of all of these. Greg Ira

Hey Guys, Darn I missed the track day registration. Well, I couldn't have brought any of my cars anyway. I may travel over there from South Florida. Is anyone interested in a very experienced road racers direction on set up, driving, etc. I might still fly over, especially if I can do some car shake down. Greg Ira SE Div Nat Champion 3 times Runoffs Pole Position 2008 June Sprints Champion 2009

Clark, These parts are typical fiberglass race parts. To build a show car out of them, you'd need to be a good body guy. I know the owner of these molds. I know Ahrens ran them the last year he ran his car. Frankly I think they're ugly and aero wise increase the frontal area too much. Good to see you at Daytona. Sorry we couldn't talk more but I was really worried about my clutch. I stay pretty focused on race weekends unless everything is working perfectly. See you. Greg

Hey Clark, Yeah, we're starting to believe there is another issue. The cam showed oil starvation. We know we ran the engine hard with low oil pressure. Once the center bearing started to go the oil pressure went way down. The crank was quite "not round" when checked post issue. The crank turned by hand and was checked during the build. We'll get it right. I still need to know if anyone out there has a model number for the ATI damper. Thanks Greg

Josh, How fast are you? LOL just kidding. G

Yeah, got some vids of a seriously ill handling car. Heim joints were worn out and we baked a LR tire trying a new thing. Car had about 2" of stagger and it was noticable. My camera uses a card and mega memory so I don't post that often. G

Hey folks, Can anyone out there tell me the exact recommended ATI Superdamper. I am going to take your word for it on this and try it. BTW, we set a new track record this past weekend at VIR by beating the old one by 1.5 secs. That ought to stand for awhile. 2:06.3 Thanks Greg Ira

Jt, No not that I know of. We are going to attack this via what I term the shotgun approach. Firstly, the engine will be re-cammed so as to bring the peak hp down a few hundred revs. The block will be align honed and I am going to have a lot of attention paid to the crank. I didn't assemble this engine, but my engine builder is a trustworthy person. He said that during the build the crank turned by hand after he had all the clearances done and the caps torqued. If the crank isn't straight, it won't really do this without a high spot. I am attibuting this problem to some anomoly we have with our set up combination. I am 99% certain it was balanced properly, BUT this is not ruled out. We are also going to try an ATI balancer. Yes, they do build them for Rebello, but they protect him by not selling to the public. LAME. Rebello does his diligence as a respected engine builder. I'd like to get a model number for some of the ATI balancers that have been used by people on this list and what engine. I believe the LD28 crank can't really be compared with the regular L28 crank for harmonics. We used Mobil 1 on this engine. We usually use Redline but this is a play car and we thought this would be fine. It wasn't an oil type problem, I am fairly certain. My GTR uses Mobil 1, I hope it'll work in my 35 year old car.

What do you mean? Greg

Again, all good plausible ideas. Tony D.- that's the first comment related to inching up to a harmonic and there couldn't be much more inching up than with a 3.36 in top gear, my lord! We're not running a dry sump on this engine, just a typical alternator and juiced up turbo pump up front. The clutch is very very small, a 5.5 inch Tilton with only two discs. I don't know the total weight or if the assembly was balanced on the crank but it's pretty small and it's rotational mass is pretty centralized. We did look at the oil filter while at the track but only to decide if we were going to hang it up or keep going. We knew right away there was an issue with a bearing, heck the oil pressure went away big time before we shut it down. We will concentrate on double checking the balancing, change the cam spec to lower the peak HP range, use a rev limiter, and try a different harmonic balancer. When these engines are working properly, it's amazing how good the parts look. If you get it right, don't mess with it!!! Greg Ira

Wow that's some radical stuff! The bearing didn't look like the above. His piston looks like detonation or too lean. His bearings look like they wore from junk in the oil, possibly particles coming off during the event. My bearings were through to the copper and got better as you go out. It's not the crank twisting necessarily as much at it's the crank whipping like a rope that you raise up and cause to oscillate. The U20 is real bad about this. Anyway, we have a new method in hand to try on the engine dyno where we're going to measure the oscillations with an oscilliscope and accelerometer. Really just where it vibrates the most. How's that sound? This hopefully will tell us where the event is happening so we can tune out OR avoid. Here's the deal. Many of these engines have these harmonics issues that you won't feel. The trick for the driver and unbeknownst to most of us is to be able to blast through that point. For instance my EP engine has an event a 8,000 rpm, not at 5000 rpm. As I am approaching my top gears to shift at 8200, it sits in that bad spot for a second or two. A 3.1 might have this spot at 5k where you blast right through it causing zero damage. We'll figure it out. Harmonic balancers are a must. It's the right one that is the guess, but maybe we'll be able to tell the difference. Thanks for all the great information. Greg Ira

Josh, Thanks, ignitions are open. Tim, no pictures but I know from a top notch engine builder what he described. What he described is not an oiling issue, I do know that. Usually the clutch pressure will hurt the thrust surface, not necessarily the bearing itself, right? This clutch is the same set up I've had for 9 years in the EP car. Marvel Mystery Oil, yeah we might try that. I might just put a Helicoil in it too. That's my friends answer for everything. All assemblies were balanced and all clearances checked during build as normal for this builder. We used one of our special cam grinds that we use on the EP car which is lower lift and more duration. Unfortunately this wants to make the power up higher. We're changing that out. I didn't like that idea to begin with. Connecting rod bearings look great. Center main looks worst and then gets better as you go out. Builder said he knew it was harmonics within the first minute after seeing this, since he's seen this before, mainly in the U20.

1fastZ, I meant to ask you what balancer you run on your car. Thanks in advance. Greg

Good questions from all. I'm going to dig for more specifics. Several observations though. I won't give away our secrets but this had one of the highest HP numbers I've seen on this list for one of these engines. The parts used are high quality parts. High RPMs in the L engines has always been a harmonics issue since day 1. We set this engine up similar to our championship EP engine, the most reliable race engine I've ever had. This wasn't a backyard build. 8500 in a stroker? Not necessary is all I can say. That has to be 2k off the peak hp if I had to guess. Even our EP engine with all the smaller recipricating mass doesn't like much over 8200, as the harmonics begin at 8 so we have to get through that point quickly. It wouldn't like Daytona where you inch up on that mark for 10-15 seconds. We used this trick new dash with all this electronic F1 crap on it. I have a sneaky suspicion that the RPM weren't calibrated correctly. This happened on an earlier generation of this same brand unit. We didn't set the rev limit on our Electramotive crank fire ignition either. Remember this is a race engine, and it'll sit up at redline in the danger area for a much greater percentage of the time compared to a street engine. I'll get back with more details. Greg Ira

Good Day everyone, I have a general question about the stroker engines out there. We built one and it recently beat the middle crank bearings up pretty bad without much time on the engine. My belief is we turned it too many RPM's and I want to know from the list if there has been a general consensus of where NOT to go with the RPM's on these engines, or where the harmonics are. This was a professionally built engine with very good parts. Thanks a million, Greg Ira Revtec Race Engineering www.revtec1.com

jknc, I know a guy in Franklinville that could do it. Don't know what he'd charge. Greg Ira

Does anyone have this? I can't see to find info on the J30 diffs even using the search. Thanks Greg

PS. The U20 engine is known for beating the bottom end bearing to death. Don't rev it up to high. That engine has a super heavy crank that seems like it should be built for a tractor trailer, but the harmonics beat the crap out of the bottom end.

You will definitely be gaining a maintenance issue using Lexan on a streetcar. If you're OK with that, Lexan is great. I cut 10 lbs from an already light rear hatch using carbon fiber hatch only that weighs 2.5 lbs! You can also do a flush mounted quarter window that helps with aero. I used special GE Glue from the polycarbonate store to glue mine in. No problems. Things to consider for rear hatch. 1. I think it's important to follow hatch contour for aero reasons. I bought plastic washer of the appropriate depth to achieve this from McMaster-Carr. I also used aluminum bolts and nuts for attachment approx every 8 inches or so. 2. For the glass not to try and lay flat once you have it all attached at the perimeter, you will need metal straps on the inside and outside. I use two equally spaced AND the inner one has to have a contour built into it. Greg Ira

Shinyuu, I have had the same issue with one of many Z's I've had. Actually it's still on one of my 240 race cars. I call it the cam effect, meaning likage geometry, not actual engine cam. It's almost impossible to apply a little bit of throttle to this car. I attibute this to two things. We don't run any oil in the carb tops to dampen the carb piston movement. Also the geometry of the linkage. You can mess around with both of these. Try a little heavier weight oil in the dashpot of the SU. Make sure all the linkage is lubed up good. Our race engines are hardley ever at part throttle so it's only real noticeable around the pits. Greg Ira