John Scott

I had some similar questions as well, but looking toward supercharging. As I understand the later ZZ4s bottom end was good for up to 500 hp, says Chevy. The pistons, of course, aren't up to the task of pressurized hp. Also since the whole assembly is balanced to the high 10:1 comp. hypereutetic pistons and powdered forged connecting rods, you need to basically start over with the recip. assem. The zz4 is a fantastic powerplant,naturally aspirated, but for supercharging I think you have to start from square one with a bare block and low comp. forged pistons. The $ spent on the zz4 would be wasted since it is a matched assembly. All you would be using is the block and crank. Same with the ZZ430. Don'f forget the turbo profiled cam. For a serious turbo motor I'd start with the bowtie block and steel crank. 500 hp would barely be breathing for a turbo V8. The features on the 4" bore bowtie are impressive Expensive, but if you are looking for bullit proof...Read up in the 2000 perf. parts catalog. Ask Sallee Chev for their price. Always quoted me lower than the other Chev dealers JS [This message has been edited by John Scott (edited November 04, 2000).] [This message has been edited by John Scott (edited November 05, 2000).]

...but not with my carburetor. Rob was generous enough to pull his boat carb off and let me give it a try. Instant revs to 7000! Now I just need to find why mine won't flow. I've blown out everything. At least the problem is located. Anyone know if metering blocks, front/rear can swap locations? JS

Cool, so a 4.3 could have between 408 and 605 hp. Thats a pretty big spread! I agree with the low end for street figuring. Especially with my engine. Boost + well prepared high flowing heads/ cam profile/ exhaust= big increase. Tells you how important matching your components can be. I need to do some reading! JS

Turbos, having nearly the same adibiatic efficiency as cetrifugal superchargers, will have comprable boost limits. Some real basic rules of thumb for boost are as follows. This assumes tuning is already set to optimum condition, no intercoolers, running on premium. 10:1 max 5psi, roots style only 2psi, 9:1 9psi, roots 5psi, 8:1 about 12 psi, roots 8psi. As you can see roots are way less effecient. The exception to my knowledge is the new Whipple design which approaches centrifugal/turbo #s. Aluminum heads allow a little more. Another important consideration will be cam design. Stick to a dedicated blower/turbo profile with a wide sep. angle. A performance grind often leads to excessive cylinder pressures. Sometimes just a cam swap can make the same engine ping with no other changes. FORGED pistons. Worth every penny. JS

Amazing what a simple question will turn into. The amount of knowledge, experience, and some damn stubborn opinions this site can generate is nothing short of amazing. Euro280zx, I think you'll find whatever direction you take, you'll never be short on advice. We all look forward to following your build up. Please keep us updated. Also thanks to all for keeping the posts relatively clean and sane. Not always easy to do when your ideals are challenged. JS

euro280zx, Well you have an ear full, or should I say eyefull of information and opinions. Everyone here will vary on what makes a perfect HybridZ. The main focus isn't always what makes the most hp, but to improve peformance in any area from the stock platform. Beware of any manufacture/seller's claim to big hp. Big figures will make them more $$. I'd say some of our experienced 6 cylinder Z builders have given more realistic figures for obtainable hp. Ask yourself what is going to suit your needs, how it will be driven, how tempermental a powerplant you want. Generally the higher the hp with small displacement, the more difficult and streetable they become. High compression, and big cams only work with good gas and very limited high rpms. You've stated your desire to keep the base engine and fuel injection. You prefer foriegn to domestic powerplants. Sounds like you know pretty well know what makes you happy. Keep researching and listen to those that have been there. I've seen a early Z with a turbo and nitrous hit over 132mph in the quarter! I'm sure it took a lot of cash, but I can only think he was smiling as big as the rest of us. JS

A Ford 390?? That'll take care of my problems! Just kidding! Yes, I'll take you up on the carb offer. Niwot is completed and off North to Windsor. If I could pick it up some evening, that would be great! Thanks!! JS

Probably right about no carbon build up with that few of miles. If the vacuum diaphram is off, whats holding the plate in place? There should be some kind of linkage that connected the diaphram to the plate. I'd have to see the dist. for sure, but something needs to retain/ limit the movement that the vacuum advance used. I know my dist is different, but I disconnected the vacuum line and left the diaphram on the dist. If I were to remove the canister and linkage the plate would be free to move and throw timing way off. JS

Morgan, vacuum advance is like it sounds. It runs the engine at more advanced timing to achieve better economy under no load conditions. On a high performance application, I usually run a distributor w/o the vacuum and just rely on the mechanical. The vacuum advance shouldn't have any effect at WOT conditions. If its out of calibration it usually causes a part throttle pinging. Anyway, your pinging might be due to carbon build up on the pistons which create hot spots and predetonate. Your car is under a more severe load at low rpms, especially with a big cam. Also, a too lean fuel curve can cause pinging. I don't know squat about Webers, but if they come in progressively this might be a cause. Whenever I've had a distributor in even a tooth off, it runs like crap throughout the whole range, if it will even start. With the motor off rotate the engine by hand until your timing marks are aligned. See if the rotor is pointing to the #1 terminal on the cap. (If its not on the compression stroke it will be 180 degrees off. If so make another complete revolution of the engine, then confirm rotor position. A tooth off will be way out of the vicinity of the #1 terminal. If it is off, then either Mike's suggestion of rewiring cap accordingly, or just pull it and install it correctly. Not the distrib? Then I'd try one of the fuel additives that are supossed to remove carbon deposits and get your timing back up to where it should be. If nothing else works, then try an octane booster. I hate the stuff and makes a mess of the plugs! Another thought, if the vacuum advance was disconnected, how was it done? Just unpluged? If its like a Mallory, removing the arm from the vacuum canister that's inside the distributor will cause the distributor plate to move around causing eratic timing. This would be evident by using a timing light and seeing fluctuations in the timing while remaining at the same throttle position. I wouldn't set the timing by the hard to start rule. The best way is whatever gives you the best performance w/o predetonating. The max advance rule doesn't hold true in all engines. This can be confirmed with your favorite accelerometer. JS [This message has been edited by John Scott (edited October 27, 2000).] [This message has been edited by John Scott (edited October 28, 2000).]

This is probably way too simple, but is your emergency brake switch sticking? If mine is even one click on, so is the light. JS

Holley is becoming suspect again. I have a Mallory unilite. Replaced with my spare module, tried wiring direct from battery to ballast, and disconnecting tach. I beginning to think its an internal blockage in the carb. clint78z, this afternoon I'll put some faith in your suggestion. Thanks to everyone so far. If I don't find the problem soon I'm having a demolition free for all followed by a weenie roast Update 10/29: Still chasing my tail! What the @#$% is wrong with this thing!! Took the carb apart everything looked really clean. Floats are free and needle/seat are fine. Blew out all holes with carb cleaner. No difference. Why did my Mallory coil die? Coincidence? A new MSD coil changes nothing. Two different modules have no effect. Never tried before, but if I leave my foot to the floor long enough it can stumble past the dead spot and rev to the sky. I need to find another carb and see if it makes a difference. I've never had a problem elude me for so long!! Emailed a carb tech line, Parker carburetion. Got a response within the hour. Invited me to a phone consult. Big circle track race tuner. Had lots of good tips and advice, but he too, is baffled by the symptoms. Glad to know its not just me. Got my 6AL today Hope I can get this nailed down. JS [This message has been edited by John Scott (edited October 29, 2000).]

Ahhhh this is driving me nuts!! Mallory coil died. Put a blaster 2. Started, but same problem. Lots of fuel in the carb. Just winging in neutral shouldn't cause a fuel starvation problem!! Pressure is 4.5 at idle. Anything past 0 in. 14 psi. (vacuum/boost regulated) Where's a zz430 when you need one?? JS

I wish it were injected!! Nope, its just a holley dp. As of last night, dead. No spark from the coil. Found an old MSD blaster. I'll try it out. BTW what's a near new MSD6AL worth? A local drag racer put 2 runs on his this summer and blew his motor. Bought a 7 series to go on the new 509(?!). Maybe this electical SNAFU was an omen to upgrade? JS

Maybe I should amend topic to ...and my mid range, low end and soon to be everything!! What ever it is is having a slow death. New plugs and wires. Max rpm went from 6 to 5500, to 4500. Hah! pretty soon it'll just be the starter. Tach bounced once, twice and then engine died. Started again and had one good rev to 7500!! That's the ol' engine! Then thppppp! (sound of low reving 6 cyl) Man, it sounds like it hits a rpm wall! All wiring to tach, distributor, and coil seem well. I have an extra module for the distributor, but my experience with Unilites is when they go, its dead. Still worth a try. Dang, where's that old Super coil I had for years? Maybe when this "thing" falls out, burns up, or disintegrates, I can say "There it is!!" JS

I think the transmission of choice for a mid hp Z is the aftermarket T56 (400 ft/lb). Its about as straight forward as a T5 in installation. A little shorter drive line. 2 wires for reverse lock out. Better in some ways, it goes in w/o the weird offset. Same clutch, slave, bell. Big drawback is its price. If your car has a bad habit of eating T5s, it might be worth the cost. My exuberent friend with his stock 92(?) TA w/wimpy 305 blew his WCT5 on the first day. The T5 doesn't like drag race type driving. JS

No wierd misses in the low or mid range. Power is still strong below 6000. Just past 6 it feels like someone stuffed a rag in the carb. Hmmm I did take that out before I reconnected the supercharger last time. Would a coil lose power in just the upper end as it starts to fail? I'm pretty sure its going to be ignition related, but am open to any suggestions. Thanks JS

Started as a really noticible surging between 6-7000. Now seems more like a rev limiter. I've run it w/o the supercharger so I think I can rule out fuel starvation. Valve springs suddenly lost tension?? Never had it happen. Throw some ideas at me. I'm bummed! JS

a57oval, lurid details would be great, but I'd settle for general. I believe in decicated blower motors!! Mine runs 7.5:1 and has run up to 16 psi w/o detonation on premium. Eventually I'd like all the build details as well as your tuning specs. In other words as much as you'd like to share with us. When you get some pictures up it may answer lots of questions. Which carb are you running? How much strut mods did you need to make? Sounds like a great ride! I'll look forward to hearing more. Perhaps this part of the thread could be restarted in the V8 section so we don't clutter up the brakes wheels suspen?? JS [This message has been edited by John Scott (edited October 15, 2000).]

a570val, sorry to veer from the subject, but had a quick question. I've taken lots of measurements with my P600B. In a previous post I stated it might not be possible to run the P600 with the engine in the full set back. Is yours in the full set back position like the JTR kit or more like the Scarab? I'd like to hear more about the car/ engine specs. I'd like to do a project like this someday Some here are running the Toyota brake upgrade. Look at Mikelly's tech articles. JS [This message has been edited by John Scott (edited October 14, 2000).]

Tony, they make BOP adapters to use the chevy to BOP or BOP to chevy. I gave mine to Locutus a few months back. JS

Donna83zxt, good topic starter and welcome to the site. I know there's a lot of work to be done on the design and composition of current sparkplugs. I 've been using the Rapidfires since the came out and found they smoothed my idle. Also cleaned the WOT transition. Not talking great hp gains, but noticible. I'd like to hear more on the Iridiums.

Myron, I've had runs that vary as much. If there's any wheel spin I can't make a judgement. I've also had runs I thought were killer only to find the Gtech says otherwise. I boosted up 4 lbs and lost well over 1/2 second. Spent way more time spinning the tires on my 1-2 shift. My carb is really obvious to the change. It hits a big hesitation with the smaller PV. None with the 8.5. In fact this is the best my carb has run since I put it on! I suppose every engine will have its preferences. Maybe I got lucky and found the one mine likes. BTW I like to spend lots of time behind the wheel. Drivability is an important factor as well as a quick 0-60. A better test of hp gains is run it through the 1/4. Less sensitive to a little spinning as the mph will tell you if you headed the right way. JS

JT, I don't know if AC has a crossover for the Z engine, but I've had excellent luck with the Rapidfires. I use number 1. Also had good results with the stock plugs for the Syclone 4.3. I know ACs don't sound as cool as NKG or Bosch, but work great in mine with lots of boost. JS

The 700 in gear pulled 7 in of vacuum @ 750 rpm. In neutral with the 6 speed @ 900 rpm pulls 11 in. Regardless of rpm it pulls more w/o a load in neutral. JS

Practiced what I preached and put a new power valve in the 600. I had a piddly 7" in gear with the 700. The new trans gives me 4" more with 11". (in drive with the 700) An 8.5 PV is super smooth from a stomp and no hesitations anywhere. Too bad we're about to get the high oxy fuels for the winter. This will mess up everything again! JS [This message has been edited by John Scott (edited October 01, 2000).]