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Detonation will cause that kind of pitting. Noticeable pinging (or any pinging for that matter) is bad for any engine, especially a forced induction one. I am assuming that one of the unfortunate events was the head gasket blowing... You will need to smooth all this pitting otherwise the hear will be even more prone to detonation. I would also have the head pressure tested. And, make sure that there is no pitting in the area where the head gasket sealing rings sit. What is a "PO"....

This is the lash pad that broke: There are no grooves like this OEM one: This is what Dave Rebello was referring to. With this groove, it give the lash pad a weak spot where it can break. He has never seen one snap like this when there wasn't a groove. This is a full competition head with spring pressures to match. I'm also running slightly less lift than what it ran with in the day. If there were valve float we would have known it way before this happened (going on 1.5 days of tuning). The rocker that came off took out the one next to it. The valves look straight, and the springs are in tact. I will pressurize the cylinder to see if the valves are leaking. Thanks, Pete

Hi Ron, Really nice work on this project. Question, are you using an RT diff mount and poly busing? Are you using poly mustache bar bushings? Did you have your driveshaft precision balanced? Any and or all of these things will contribute to vibration. The most important thing is driveshaft balance when using the RT mount and poly bushings. The stock rubber bushings will absorb a lot of this vibration. Poly bushings will conduct that vibration into the chassis. Most driveshaft shops will do a standard balance, which is good enough for a live axle, but no where near good enough when the diff and trans are both mounted to the body. I had this issue with my RB swap, and I had to ask for the "race balance" on the driveshaft. For the exhaust on my NA RB swap I used the MSA premium exhaust with a custom made down pipe. At 3000RPM, it is quiet, but below that it drones (probably like your S52 powered Z). At 4000RPM it sounds wonderful. So I was thinking of adding an 12" resonator along side the driveshaft, hoping that it will kill the drone below 3000RPM, but still not effect the sweet exhaust note about 3000RPM. I'm also using my Z as a nice day commuter. At 32MPG, it make a lot of sense these days! Pete

Tony, Ever seen a lash pad do this before? Dave Rebello said that on early aftermarket lash pads there was a groove machined for oil along each ear. Those would fail like mine. But these don't have a groove. Since I have to run a distributor, I might as well run a good one. I'm triggering the 6AL2 and adjusting the timing curve there using the retard curve. I set the static advance to 40 deg so I could retard it to where it needs to be. We had to drill another hole in the button to get the rotor tab to line up correctly with the cap.

I think these XXRs are pretty sharp. You can also get 15x8 as well. http://cgi.ebay.com/ebaymotors/16-8-XXR-522-Chromium-Black-Rims-Datsun-240z-280z-280zx-_W0QQcmdZViewItemQQhashZitem53e743a641QQitemZ360362255937QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories I'm running these on my street car: http://cgi.ebay.com/ebaymotors/15-8-XXR-513-Gun-Metal-Rims-Datsun-240z-260z-280z-280zx-_W0QQcmdZViewItemQQhashZitem43a6a70bffQQitemZ290558774271QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories good quality, and you can't beat the price. Smaller diameter wheels look better on S30s IMO.

I spoke with Dave Rebello, and two other engine builders and they have never seen this happen before. I'll call Isky next to see what they say. The AFR goal is 13-13.5:1, but with these Mikuni race carburetors, achieving that goal is not possible across the entire RPM range. You have to live with some rock areas to get the AFR ideal on the top end. And since we had the lash pad issue, we couldn't continue to tune. Most likely we are done tuning for this year mainly for cost reasons.

Nothing fancy. It is 35 deg above 3000RPM. Basically a flat line. Cranking timing is 15 deg. From 1000 to 3000 it is linear from 20 to 35 deg.

The term "shotgun" coming from how often that car backfires. LOUD backfires... I'd be willing to bet that the camshaft timing has always been off, and after all those backfires, the damage has finally been done. Take it apart for sure. Pete

Joe, If the motor has run good in the past, then something has gone awry since then. If you have checked: TDC with respect to the timing tab, cam timing, ignition timing, spark, and fuel, there is something else causing this. Since the motor doesn't turn easily (with the plugs out I am assuming), and compression is low, I think it is time to tear it down. Is this "Shotgun" Jimmies car? Pete

Here is the configuration for the data above: ENGINE: 280Z mon 5-2-11 INDUCTION: taper-bored 44 mikuni 36 155f gages 165 175a 67.5ls 35p Datsun Comp manifold w/44mm isolators 1.375 50mm stacks ITG cleaner in place wide open stops on all carbs PISTONS: 13-1 Cosworth 87mm RODS: Carrillo 133mm CRANK: Datsun 79mm CAMS: Isky to stock marks .010ih .010eh Stock ROCKERS timing measured .035"adv (in open more @tdc) FUEL,OIL: SUNOCO STD @2.5 20W50 valvoline w/Red Line break-in EXHAUST: Datsun Comp 3to1 X2 1.375"x24 2.25x36 6" magnaflow 2.25mufflers and 18" tailpipes 5" flex to mk2 dyno exhaust no uego IGNITION: MSD 6530 AL-2 programable 35 total actually measured at 35deg Total

OK, here is the good news, it's making decent power now that the butterflies are opening up all the way: The bad news, a lash pad broke: The good news. There wasn't a lot of damage. The rocker is dinged a bit. Nothing a file won't cure. Not sure why the lash pad just snapped like that. They are MSA 0.170" lash pads. Anyone ever see this before?

Piston skirt to wall clearance is what I was told by my machinist. Pistons are tapered, because they expand more near the fire than at the skirt. The piston skirt clearance on my build was 0.006", but this was for forged pistons which expand more than cast.

Here it is on the dyno: Video on the dyno (sorry for the rotation): So far the motor has survived the dyno. And the cryo treated Isky cam survived initial break in. We use RedLine break in additive and Valvoline VR 20w-50 oil for break in. After a good 1/2 hour at 2500RPM we changed the oil with Brad Penn 20w-50. Compression is 250lbs across all cylinders. We had to re-adjusted valve lash three times to get everything to settle in nicely. After a bunch of pulls, we realized that the dyno was not opening up the throttle all the way. It was making 250HP in this state. There is also one plug that we can't seem to get indexed right, so it is up in the head more than we would like (using copper washers). It is not firing as good as the other cylinders because of this. Running 35deg advance right now. More tuning Monday, stay tuned... 8^) Pete

Nice work! The ARP rod, main, and head studs all torque to 60ft-lbs with their special lube. Since it looks like detonation caused the piston damage, I suggest you pickup a cheap dial indicator and confirm that your timing pointer is accurate while you have the head off. This way when you calibrate the ignition timing in Megatune you will know that it is accurate. While you at it you can measure the deck height and compute the exact CR. I recently went through this with my C production engine I built: Pete

I've used ITM head gaskets, and they are as good as OEM. Get the Felpro oil pan and valve cover gaskets. Just have the shop press old out/new in. Have them check the size of the big end. I have no idea what teflon pin buttons will do for a pressed pin setup. I suppose Tony will chime in though. If the pin is moving in the rod, you got issues. I know they are an option over pin clips in a floating pin setup.

You mean the camshaft timing, correct? For ignition timing you know you can turn the distributor? Also, are you sure that the oil pump shaft is timed correctly? You can check the cam timing by getting cylinder 1 at TDC with both valves on Cylinder #1 closed. Look through the hole in the timing sprocket at the notch. It should line up pretty closely to the mark on the cam tower plate. Here is a good pic I found on the internet:

That's not a bad deal. I like the ITM stuff. Their timing set looks like OEM. Depending on the gasket set, you may want to use a different oil pan and valve cover gasket. The cork ones suck. The Felpro oil pan and valve cover gaskets are the best. Clevite bearings are the way to go. Nissan bearings are good too, but the last set I ordered were super expensive (2x Clevite), and I had to return them because they were scratched. I would use the rockers from the E31 cam you want to use. If they are in good shape that is. Same with the lash pads. Keep everything sorted so that it goes back on the same way it came off.

Sorry to hear that you have to open up that can of worms. At least you now know what was causing the oil consumption. Not sure what your schedule is, but my torque plate is going to Ron St. Croix in Newfoundland first, then it is available if you need it. Now comes the "while I'm at it" costs...

They are Mikuni 44mm with the chokes removed. So in effect they are 50mm. This is how I received the carbs. This is a mod they did back in the day. Todd at Wolfcreek went through them. According to the guy that will do the final setup on the dyno, properly tuned 44s will perform just as well. To compute the CR you need to know the dome volume. No where in the documentation I had could I find the dome volume. Even Cosworth couldn't tell me what the dome volume was as these pistons were make back in the 70s. So I made a mold and cc'ed the impression. Anyway, I didn't want to make any assumptions about CR. I estimate the final static CR to be 12.5-13:1.

Priming the engine with oil (sorry for fuzzy pic): Next stop the engine dyno: Arizona Z forged flywheel:

That is some nice work. Good job! Pete

Ken, If you find that your right thigh muscle is getting larger, it is probably that 1" MC . The stock 7/8" MC should work fine with the setup you are running. No need for a larger MC. Pete

I think you need to check it with a head or torque plate installed and torqued to spec. It doesn't really matter how round the cylinders are without the head torqued in place. It really only matters when it is all put together.

Could be.

When you say giving up, do you mean performance? I would think that the more out of round the bores are, the longer it will take for the rings to seat. And per my previous post, if the cylinder is out of round enough, the piston skirt could contact the bore once the rings fully break in. What do the pistons skirts look like?