jt1

Joe, when an engine dumps a lot of debris like yours has, it's very important to clean the entire oiling system. Disassemble the pump, check it for damage and debris, including the bypass plunger, clean the pickup, take all the oil plugs out of the block, remove the filter base, and clean it all up. Anywhere oil goes is subject to have debris in it, and if it's not cleaned out, the debris goes right to the bearings and starts the whole process over. You can clean the block with a pressure washer and rifle brushes, but it may be better to get your shop to do it, they will have all the correct size plugs on hand. The last thing you want to do is start it up with a bunch of junk in the block. John

Mike, how much power are you making now? The canfields are probably good to about 520hp as they are. AFR's are good heads, but way overpriced IMO. Consider the canfield 220's, they outflow the AFR 210's but are a lot cheaper. One downside is the 220's require offset intake rockers, I don't know if the AFRs do or not. What kind of exhaust are you running? That's a big problem on high hp Z's. And, unrelated, with a 3.75 stroke/6" rod, were your wrist pins up in the oil ring grooves? jt

Doc, the holes in the front bearing are at 12 & 4; the three center bearings at 2, and the rear at 12. This is the only way I've seen them done, I checked the passages to make sure they were open. A new cam with new bearings spun freely with no tightness or binding, about the only way I can check the tunnel alignment. John

In it's current configuration, it dyno'd 480hp/465tq at the crank, a pretty good pump gas 355. Especially with the cylinder walls bulging like Roseann's belly at a buffet. jt

Well crap. The bell has tolled for this block. An afternoon playing with my recently purchased sonic tester confirmed something I've suspected, that this block is a POS. While all the thrust sides checked pretty good at 0.200 to 0.250, the sides are very thin, most less than 0.100, quite a few at 0.050 to 0.060, and one spectacular side in the 0.050 to 0.035 range. This engine has never shown the ring seal I thought it should, despite careful clearances, end gaps, etc. It's always had some blowby and oil consumption, and this confirms why. If anybody's interested, I'll post up the whole sheet showing the wall thicknesses. I'm going to hunt a better block and start over. hecho en mexico, indeed. jt

Grumpy, thanks for your input. A few more factors: 1) I've used the M1 15-50 because of the temps the engine sees. In the summertime, 230deg water temp isn't uncommon. I don't have a oil temp guage, but it's bound to be approaching 300deg. 2) The engine was line honed two years ago, the previous freshen. We squared the decks and zero decked it, and my machinist likes to line hone before squaring the decks. Mains were set at 0.003, rods at 0.0025. We didn't check the cam brg clearances. The rod and main brgs still look great; they barely are shiny. 3)The rotating assembly was balanced by a very reputable shop when the engine was originally built, five yrs ago. The engine is internally balanced, I'm using a 6- 1/4" Fluidamper, and the clutch and flywheel balance was checked. 4) Valve spring pressures are moderate but not huge, Comp 977's, 150# seat, 420# nose. 5) The three center brgs are by far the worst, the pic is #4. The F&R bearings show some wear, not as much as the centers, and the F&R bearings don't have the chunks ripped out like the pic. 6) The two pieces of the main cap appear to have still been mated to each other; There aren't any shiny areas indicating the pieces were working. jt

It should take some pressure to seat the tube in the block, such as lightly tapping it with a hammer. If you can seat the tube with hand pressure I would find another one and try it. jt

About 3 weeks ago at a open track event, I experienced a noticable drop in oil pressure when the motor was hot. It was normal cold, but after a run when the motor was really hot, the oil pressure was dropping to about 20 psi. Upon pulling the motor and tearing down, I found this: This was taken with the motor upside down, with a mirror lying in the cam tunnel. Hard to get a good pic, but generally the bearings look somewhat worse than the pic suggests. Lots of wear, with big chunks of material ripped from the bearing surface. Some history: 1) This is the third time this engine has eaten the cam bearings, each time with about 1 yr/3500 miles of track use, with a few street miles thrown in. 2) Each time there has been some other contributing factor, broke pump pickup, broke rocker rollers, and third item noted below. 3) This has occured with three different cams, so the cam doesn't seem to be a common factor. 4) The last time I freshened the motor, I carefully checked the oil passages, running a soft copper wire thru them, and squirting oil in them and blowing compressed air to shoot the oil out. No obstructions I could detect. Oil hole in the bearings are properly aligned. 5) Bearings have been installed by my machinest, pretty sure they are the Durabond brand. 6) Melling M55HV pump, Mobil 1 15-50 after breakin. 7) Along with the oil pressure drop, the motor was running noticably hotter than normal, despite mid-70's ambient temp. The contributing factor this time, discovered during the teardown: This may have been a factor in the low oil pressure, but I can't really see it affecting the cam bearing situation. However, I was pretty fortunate not to scatter the whole show all over the track. The crank, rod and main bearing all still look like brand new. Anybody got any thoughts or opinions on what's causing this? I'm somewhat disgusted with this engine, and am about ready to dump it behind the barn and build a whole new one. John

Thanks for the info Rick. It takes a lot of work to get a YZ kit to that stage of fit and finish, and your efforts show. The first time I looked at the pics, I forgot the headlight cutouts wern't originally there. You've done a great job. John

Rick that looks great. Very nice job on the gills and gas cap. How much backspace do the rear rims have? I was hoping to get 315's on 12" rims under my YZ kit. John

I've got Spin Werkes (formerly Circle Racing) custom Pro 6's on my car. Very nicely made, 14.5 #, fit perfectly, nice polish. They are quite pricey. John

Drivetrain forum???? jt

Bart, the exhaust looks perfect. Sorta hard to tell about the intake, looks like it's smudged some. As long as the valves and valve job were done right they should be the same anyway. Good Job!!!! jt

Faster moving air has less pressure than slower moving air, as per Bernoulli's Law. So by making the under side smoother, the air flows with less turbulence, therefore faster, with less pressure. Only a wind tunnel would tell if any downforce was generated, but there is almost certainly less lift on the front of the car, and maybe some downforce just depending on the pressures involved. Austin, that looks great. Post up some more pics as it comes along. jt

Alf, what was the verdict on this? John

Now this is a good one. "Honey, I need to buy an enclosed trailer so we can use it to move" Congrats on the new house Mike!!!! And the trailer!!!! jt

The 1/8 NPT and M10 x 1.0 are very, very, very close, except the NPT is tapered. John

Manley and ProTech come to mind; Summit also has a house brand h beam rod. jt

Aren't all Z's project Z's????? 73 Street/Track car: Motor showing zero oil pressure when hot after a track session, and down on performance. Pan is off, rod caps pulled, all rod bearings look like new. Motor is stripped and ready to come out, maybe this weekend. Suspect cam bearing failure. 71 Track Car: Completely stripped and gutted, waiting in line to go to the hot tank. 71 VZ Street Car: At least this one is running and driving, needs a wash and wax after getting caught in the rain with it. Too many cars, too much work!!!! John

If you take a two bolt main block, and count the bolts on one side of the crank, there are five of them. I bet that's it. If you are only using 4 bolts now, your motor isn't going to last very long. You should add the other bolt immediately. Be sure and turn the motor off before doing this, or you may wind up with a rare-but-not-desirable 4 digit hand, and blood causes the internal engine components to rust rapidly. The blood and the rust are about the same color, but neither is good for your engine. Also, the bits of flesh will stop up the screen in the oil pickup, resulting in more problems. Search, in the proper forum. jt

WOW You've got to love somebody who is willing to take a sawzall to a 930. jt

The best advice I can give is to take your time on the disassembly and pay close attention to the orientation of all components, so that you can catch the problem. Compare the keyways and dots on the current gears to the new ones. If you pull the cam and lifters, the lifters must go back on the same lobes, and use cam lube on the cam and lifters. Check the pushrods for and bent ones. Check the lifters to see that they are all pumped up, it's at least possible the lifters are collapsing at higher rpm. See if the cam has any numbers on it you can trace down and get the cam specs. The main thing is be methodical and eliminate each component as a possible problem. John

A few thoughts: ATDC: After Top Dead Center ABDC: After Bottom Dead Center BTDC: Before Top Dead Center These figures are referring to the amount in crankshaft degrees that the cam event in question occurs. It does sound like the cam is advanced, but it's really hard to just eyeball it. In general, I would have guessed the cam was retarded, and the problems were caused by a combination of cam timing and low compression. With a 307 and 882 heads, 76cc IIRC, your compression ratio would be pretty low, like 7.5 or 8 to 1, or maybe less depending. The low compression and a retarded cam could cause your problem. The cam timing could be off because of several things: Crank or timing gear keys cut wrong, dots improperly marked, cam dowel wrong, or an accumulation of the above. A new timing set would eliminate everything except the crank key or cam itself. Degreeing the cam would eliminate all these, but it's not possible without knowing the cam specs, and I know you don't want to buy a new cam. Maybe check with the previous owner and see if he knows which cam it is, or if you're lucky he may have the cam card. Before I tore the front off the motor, cracked the pan, and dealt with the inevitable oil leaks, I would: 1)Block off the return on the pump and see what happens. 3.5 psi should be enough, but it would be a simple and easy check. 2) Borrow a known good carb and try on it, just to eliminate the carb. A 650 is a little big for your combo, but not grossly so, it should run decently with the 650. 3) Try another coil on it. The fact that side gapping the plugs helped might mean the mixture isn't lighting well, and it's harder to light the mixture at higher rpm because it has to happen so much quicker. You might just have a weak spark. Take out a plug, put the wire on, lay it on the motor where it will ground, crank the engine, and look at the spark. It should be bluish-white. If it's reddish-orange, it's definitely weak. It's best to do this in a dimly lit area so you can see the spark better. Try another coil just to be sure. If none of this helped I would try the cam timing, first the timing set, then new cam and degree if neccesary. Remember that most really good problems are not one single issue, but usually a combination of smaller issues. In the long run, if you're gonna keep running this motor, I would look for a set of 461 or 462 heads w/64 cc chambers. Upping the compression ratio will give better power, gas mileage, and throttle response. jt