katman

Good question. Don Potter always told me there was a resonance at about 6800 rpm in an L24 with stock balancing (i.e. no heavy metal) but our dyno runs always had a buzz in the floor at about 4000 rpm (lots of different engines, same buzz). I could never confirm the 6800 rpm thing, but never instrumented for it either. The floor buzz at Sunbelt could be a function of the natural frequency of the dyno stand and not the engines. We've put a lot of race miles on junkyard OEM dampers and never had a failure or any sign of impending doom. I suspect folks who have recurring problems with dampers don't have a damper problem, they have a balance or straightness problem.

Yeah, what John said. Racers often get away with things like solid engine mounts and solid dampers because they inspect things all the time or xome of them even expect things to break because they're racing" ("I was making so much power I blew that engine", yeah, meanwhile I was trying not to spin your mess on my way to victory) but to me that just means they're GETTING AWAY WITH IT. Don't make it right, don't make it last. I'd never run a solid front pulley on L6, and I don't even run solid engine mounts in the classes I'm allowed to anymore- got tired of hardware coming unscrewed all the time and welding fatigue cracks in tube chassis and engine blocks. Plus, I guarantee you OEM's would find a way to drop the expense if it didn't have serious merit.

Ha, that's funny. We call them Re-bomb-oh motors.

Alas, the wife, kids, and minivan have conspired to eliminate the machine shop from my current list of liabilities. The strut bar was a n attractive yet very light and stiff piece, but not necessarily any better than some of the other "limited edition" ones others have made. The downfall IMHO of most of the aftermarket ones is the wimpy attachment to the strut tower. The bar part is just a rectangular tube aluminum extrusion, something like 1 inch by 2 inch by 1/2 wall, with lightening holes machined in it for looks. The key is the tower attachment, which on Chet's race cars captured about 4 of the aircraft screws in the Tilton camber plate and about 12 more down the side of the tower to distribute the loads out. I haven't seen Steve's bar up close to see how close to the original design intent he kept it, but if you get in touch with him AND he has means of fabrication I'd be happy to review it (if he wanted me to) to ensure it is as stiff as the original. Looks good though, eh? This would be a great application for carbon fiber since the loads are simple, but I digress...

That's a copy of the custom strut bar I first made for Chet Wittel's ITS 240Z race cars about 6 years ago. It was copied by Tom Thorman's now defunct Z Service Unlimited and has probably most recently been done by Jim Thompson at Sunbelt Performance Engines, or by Sunbelt for Balanced Performance in Suwanee, GA. Nicely done, who's car is it?

Uh, that'd be 4.248 and most virgin heads measure closer to 4.251. We usually mill the slots for the 4mm bolts in the curved guide out a little extra so we can use a pair of channel locks to squeeze the curved guide toward the straight guide and lock it down so there's virtually no slack in the chain for ITS racing motors with heads milled say 0.010 to 0.020. For a virgin thickness the stock slots in the curved guide should suffice. We don't rely on the oil pressure from the tensioner, and you don't want the chain flopping around because it does all sorts of nasty dynamic things to the cam and valve train forces. How much slack is kind of a touch thing. If you rotate the crank backwards a smidge to make the slack on the side with the straight guide, there should still be a little tension there, the chain shouldn't be loose.

DP Racing, or Design Products Racing, or Don Oldenberg and his wife: 714-892-1513 last I tried. Huntington Beach CA. Don used to work for Tilton I believe and still makes a lot of the old Z car stuff for Nissan Comp. Camber plates, oil pans, etc.

Danno, being the typical paranoid structures engineer, has some valid points. My problem with all these aftermarket adjustable control arms (AZ car, ZFRacing, and the one Dan links a picture to, for which I actually did a quickie analysis for the guy who made it- very nice part) is they put the threaded shaft of the heim joints in tension/compression and bending. Maybe not too big a deal, but nothing prevents a guy from extending the threads out a pretty good bit to where the stress in the root of the threads is definitely non trivial. Not really a static problem, more of a fatigue problem. On a race car we inspect that sort of stuff every time the car comes off the track, and if it does fail we got a full cage around us. I don't expect "street" folks to be that diligent with inspections, or even know what to look for necessarily. Just some other things to remember- yeah the braking, accel, and cornering loads are higher for a race car but the number of cycles is way less, and the maintenance tends to be way more. The drag loads on this piece are reacted entirely by the front inner mount, so the forward heim joint gets near all the fore/aft load and hence the shear and bending. Threads are a nice little notch for cracks to start in, even rolled threads. The stresses in the minor diameter of the threaded heim is proportional to the diameter to the 4th power, so you can see it is very sensitive to what size thread you use, and the quality of the part. Analytically they may all be just fine, but I can see why Dan is "stressed".

1-3/8 for an ITS 240Z would be about right. With another 26 cubic inches or so for the L28 and a cam I'd probably be looking at 1-1/2, even for a street car. Best bet- ask Jere Stahl hissownself.

In the quest for an honest 500hp it's my wallet that always ends up being the weak link....

The R160 is smaller, lighter, and barely adequate for a stock L24. Not the kind of thing you want behind a V8. The 160/180/200 refer to the ring gear diameter.

The F54 is the late 280ZX block which is siamesed between cylinders, right? Some builders would prefer to use the early 280Z block (N42?) for it's higher nickel content and unsiamesed cylinders. The siamesed cylinders distort in an "unround" fashion at different temperatures and should at least have the final honing done with torque plate and at operating temperature. This is true for any high performance application, even turbo's.

"Luke...Use the FORCE Luke....."

No. You can grind the throttle shaft down and use flush screws like Ztherapy does on their non IT racing carbs, for a whopping horsepower or two. The key to power with the SU's is getting them to maintain optimum mixture above 4000 rpm or so when the slide is pretty much all up (i.e. mixture isn't regulated by the needle anymore). To do this you need to find a way to slow the slide down for the last 1/4 inch of travel or so and custom taper the needle and make about 100 dyno runs to figure all that out. For another 10 horsepower. Hardly worth the effort unless the stakes are big. Keep them clean, keep them tuned, and you're 99% there.

Stock L28 with SU's say 170 hp. Commercially available cam with no additional compression or headwork- maybe 12 hp. Header and 2.5 exhaust, maybe another 8. Call it 190 for the state of tune that most street cars are in. Well short of a 302, but still lots of fun.

And to muddy the waters a little, flow is just a partial indicator of power potential. How the intake port enters the combustion chamber, and the combustion chamber rework, also determine turbulence, mixing, flame propagation and hence torque, and have as much to do with power production as raw flow numbers. I can make big ass ports that flow great and the engine will be a pig. Unless I'm buying from a builder that can show me the dyno chart for a head/cam combo, then a "ported and polished" head means little to me. Heck, but put it up on Ebay- "ported and polished" is one of those terms that "sells" to a large crowd.

AE growing cracks in old Lockheed airplanes.

For a street L28 with your mods I'd stick with a 1.5 inch primary about 34 inches long with 2-1/4 collectors about a foot long followed by a 2.5 tailpipe. If you can afford it I'd go Jere Stahl for the headers. Short of that, well, lets just say that from a performance standpoint the rest make about the same noise.

Unless it's one of the direct drive units it probably isn't anything special. For instance, the Datsun Comp Upper Close Ratio Overdrive, or CROD, is just a '82-83 280ZX tranny as I recall. May or may not be worth anything extra.

Ahhh, John illustrates the "power" of handling and driving. Reminds me of a Triangle Z Club school at Roebling Road a few years ago when Chet Wittel (ITS track record holder at Road Atlanta) and I took a $300 (honest) 240Z there with some of our cast off race tires and brake pads and proceeded to wax just about every Porsche 911, Acura NSX, BMW5xx and a V8 Z in the instructor class all weekend. Granted our $300 Z came with the old BSR Koni handling package (115/145 springs, Koni shocks, sway bars) but that's all. Stock 200k mile L24 engine. Life begins in the turns. God I miss that old piece of junk. Now give me a V8 240Z for a week to "prep" and put John or Chet in it and I bet we can obliterate some ITS track records. Putting a V8 up against an L24 on a dyno is as unfair as putting an SCCA top notch driver and car up against somebody who does a few track days with his street car every now and then. Just ain't apples and apples.

We always use a torque plate with a new head gasket, install the main caps, and hone it at temperature for race engines. For a street car I'd at least want a torque plate and main caps installed.

Sorry, been away. I'll email off line to you guys. A few months ago I sent it via one of our moderators to SuperDan but I don't think he's got a chance to put it up on this site yet.

Either Crawford Z Service (615) 327-4159, I think they're near Nashville, or Sunbelt Performance Engines (770) 932-0160 in Suwanee GA if you want it done right.

? That just doesn't make sence. That'd be a typo, sorta like "sence". I meant A/T.

325 hp in a 2400 lb car is supposed to be scary...but you probably need new bushings and an alignment, maybe new shocks too. Is i really "roll" about a longitudinal axis or "yaw" about a vertical axis?