Dave WM

sounds like the guy in bev hills. He has a lot of Z cars that come up on ebay, I seem to recall a car like the one you describe.

is this the place? http://www.autorestorationdepot.com/about.html

I still need to post up some pics that maybe clues to exp eyes. there was def something going on from the staining I say on the cylinder walls. I looked like the fire ring seal was not perfect. I will post up as soon as I get the darn cameral to work.

there is no apparent loss of coolant, so the leak you refer is for an exhaust gas to water leak? I did pressurize to about 15psi, is dropped down in about 15 min, but I think that is more my old pressure tester not holding than a leak. I did the same to my 75 which does NOT have the issue, same result, pressure drop off about the same amount of time. I carefully cleaned the under side of the orig head, can see NO defects around the combustion chamber. seems to me in order to get gasses into the coolant, It would have to be cylinder wall to coolant passage block crack cylinder head to coolant passage crack (no evidence of by close visual exam). fire ring seal fail (warped head incorrect clamping pressure). corrosion from combustion chamber to coolant hole (looks fine to me, no corrosion) allowing gas to seep under fire ring. there are NO signs of water in oil pan, or under oil filler cap. I don't see the oil slick in the rad but there is something floating about, but does not look like an oil film. I figure is just residual trash but could be wrong. The chem test passes until the water begins to flow thru the T stat. then a very slight change to green will show after several pulls on the rad top. The tester is well away from the actual water (no contamination of water to test fluid). I rechecked the orig head, I found some 1" bar stock alum to use as a straight edge about 2 ft long ( I had been using a 3ft metal ruler). with the bar stock turned up on its edge I was not able to get even a .0015 between any 3 cylinders, so I am pretty sure its not a warpage issue. this was checked longwise and diagonal two ways. the surface as very clean, not perfect, but clean enough to see the orig machining marks, and marks made by the OE gasket digging in (very small divots). I would assume that if the fire rings seal and the alum combustion chamber shows NO crack, then it has to be the block. But that is my in experienced guessing.

I think I am going to take the block to rev master, do a hot tank and magna flux before doing anything else. The Tampa guy seems to really know about L28 heads. Time for your turbo to take a ride on the test stand!

putting this link is so I can find it again Amtex Cylinder Head and Casting, 1412 N 22nd Street, Tampa. (813) 248-9429 http://www.amtexcastingrepair.com/?fbclid=IwAR2bOxuzAdbRoqd-MhHtBmvAwtvoy_0PXxx34TCJLai-bz6K_adTjzONZCY

The guy at the machine shop really thinks its more likely just a bad sealing head. So the plan will be to bring it all to him (block and both heads) and let him do his thing. check the block and refinish the better of the two heads.

same results with the MN47 head, even burped up a bunch of water before the Tstat opened (although at this point I think that is unrelated). chem still turns green, no other symptoms of a problem. I hot checked the compression, 175psi on the nose for all cylinders, even forgot to open the throttle. (checked again a little over 180 on all with throttle held open) Anyway I am guessing I have two good heads and one bad block, but that is a guess. I am saying this since changing the head had NO effect on the chem test. So I guess my next course of action will be to pull the engine apart and take the block off to be tested. I have some pics of the cylinders I will share soon, some odd looking stuff at least to me. I took them between head changes.

I grabbed that a while ago, installed it today, new head gasket, all buttoned up but I was to wasted from working in the heat that I decided to wait till next week to fire it up. I did adjust the valves and made sure my pump was still working (so the fuel pump relay and all the wiring was still hooked up. I used my cherry picker to help with removing not only the head but the manifolds as well (did I mention it was hot today? prob feels like temp in the low 100's true air temp was in the upper 90's). The cherry picker is proving its worth. I also made a wood timing chain jam tool, worked great! cold compression was about 165 on all but #6 which was about 155. I did not notice any thing valve issues on that one, but will check again after running it some. If this does not fix it I will just tear down the motor an take it to a machine shop for evaluation of the block and heads, use which ever one looks better. I would like to do a full engine build anyway.

Just remember, most folks that mod the suspension say it makes for a "firmer" ride. Are you ok with the current level of "firmness" and do you want more "firmness". If you are using it as a weekend cruiser, the stock setup may be the best option. I find my stock "firmness" more than firm enough. (going for the joe pesci casino award of using the same f word as many times as possible in a single scene).

did test 3&4 (disabled #6, cold start) exact same, still changing color. I am not going to bother trying it out on each cylinder, so will just move on to replace head. If that does not fix it I will pull the head and front cover so I can turn the crank and CAREFULLY examine the block on all cylinders. As a test I did pull air thru the fluid engine off rad cold, no change. Just wanted to me sure the chem could stay blue when being aeriated.

video not working

getting the threads right may be a challenge. I took tire pressure gauge (the round kind that you just push on and read) got it from autozone or harbor freight IIRC, removed the little chrome part, cut off the part that pushes on the valve stem, then used a file to taper the threads a touch. Clean up all the filings of course, it would thread on the block, not a perfect seal just enough threads to hold on, but enough to get a reading of about 40lbs on a cold engine startup. I just wanted to check the calibration of the sending unit.

Test 1&2 combined.

test completed, no gush, some gas, video to be posted later, but I wanted to show Jeff his gauge, I did not do a before shot, but it came out pretty nice. Must be earlier on, has the 140psi oil gauge

series of test to be video recorded cold engine, rad cap off, start monitor water temp with meat themo, check for gusher engine warmed up and running check for exhaust gas in coolant cold engine, rad cap off, #6 disconnected start monitor water temp with meat themo, check for gusher engine warmed up and running check for exhaust gas in coolant

yes I see your point, could have been an air pocket super heating the water before the T stat opens (Gushing), AND a very small leak causing the chem test fail. Perhaps I finally got the air out (no gush) but still the leak enough to fail the chem test. Oh well will test again (I like repeatable results to test a theory) if the gushing is resolved but continues to fail test, perhaps the working theory will be just a very small leak. I did NOT retorque the head bolts (felpro gasket) as that was the instructions.

next week I will do a full video of a cold start thru chem test so you guys can see what's going on (same test I did today), as I would like any observation on what I am doing and if doing something wrong. Might get a little boring waiting for things to heat up (why I did not do today, just figured it would gush and I would then go right to the head replacement and block inspection).

well test today was not what I expected. started about 90f (ambient) engine started fine, #6 connected, NO gusher. This is the 1st time for that with a T stat installed. Now I am really confused. there was no water flowing (had the rad cap off with the meat thermo reading water temps (Plus I just put my palm up to the top of the rad). I was about 1 inch down from the bottom of the filler neck (about 1/2 inch of water covering the core estimated). Let it run fully expecting to see the gusher before the T stat opened. I stay quiet until the T stat opened right at 160f water begins to flow and stays there for a while, after about 5-10 min of idling it rose to about 175 on the T stat and held there. Water flowing everything normal. Block test a few pumps, no change then had to break the vacuum by pulling it out and try again. It eventually did a very slight color change but seemed like I had to not have a tight seal least it suck itself down too hard to pump. Bottom line is I am going to give it a rest, try again next week. If it does not gusher again I will have to ponder exactly what's going on. I guess I could have been a air pocket, but that does not explain the slight change in fluid color. I have the other head prepped and ready to go, so will prob swap it anyway now that I have read up on the swap being a nice performance mod. I still think I have a bit of a mystery on my hands. I suppose the best course of action would be to simply take it to a machine shop that can test for cracks in both the block and head and then get it machined as required (if ok). But at this point in time it seems that would be a waste of money since I really don't have an immediate need, and I really just wanted a spare. I too would like to see the engine in actual use ZH that would be a real world test since the only issue right now seems to be the chem test fail.

got the replacement head super cleaned up, checked for warps again. One other thought, when I get ready to pull the old head off, I am going to rotate the crank 180 degrees off TDC. Then install the jam tool. I figure this will let me inspect the cylinder bore for possible cracks since that has not yet been ruled out (#6 piston will be at the bottom). I am 99% sure its #6 (either the head or the block) based on the test above so I can concentrate on inspection there. I was even thinking of some UV dye in the water and running it one more time, that way I can use the dye to help look for defects. Will run with the cap on so some pressure is built up after shut down. Granted the pressure will not be the same and in the reverse direction, but I figure it cant hurt. Clearly I will have to remember to set the cam gear off 45 degrees as well, will use a grease pencil to mark the chain and gear.

Test one left spark plug in, just pulled FI plug #6 started (miss obviously) let it warm up, NO GUSHER, water temp when T stat opened about 165ish per meat thermos on rad neck. after letting run for a while like this I do the blue chem leak test (pull air from rad thru sieve into blue chemical look for change in color. NO change stayed deep blue. finally hooked #6 FI plug back on while running engine speed picks up adj idle back down, NO GUSHER but then that was expected since the water was moving freely, but it did FAIL the chem test (could see it change from blue to green, would have been yellow eventually. So sure looks like I have an issue with #6. Since the ONLY change from gusher to NO gusher was pulling #6 FI plug I will test results one more time, only change will be putting #6 FI plug back on and restart cold engine, if GUSHER then I would say that proves it beyond a doubt. after that I will pull the head and look under a magnifying glass to see if I can locate any cracks. IF not I guess it could be a block issue, which would be bad since I have the spare head but not a spare block. I will reinstall the new head anyway since I don't know how to test the block. If new head has issues and #6 is the fault, then that would tend to make me think its a block issue since it would seem unlikely that both heads would have the same issue in the same cylinder.

after some more reading it seems this is a popular combo (N42 block/MN47 head), as my spare engine has dished pistons, perhaps the CR will not be as big an issue as I thought.

I was thinking of trying to disable one cylinder at a time (disconnect FI plug) just as the eruption of water starts to happen (it last for maybe 10-15 seconds) After that the thermostat must open and no more issue (other than the orig problem). If just one cylinder is a problem, I figure no combustion no pressure, stops the eruption of water out of the rad, the water that comes out is not hot at all. Kind of moot though, I want to see if the maxima head solves the issue, then I will know for sure. Ok after sleeping on it, the plan is to start one cylinder at a time, remove plug, attach spark lead so spark has someplace to go, disconnect the FI plug. This way there is no compression, no spark, no fuel just a air pump. Then start engine on 5 cylinders and see if the water temp come up without the gusher. Do this on each cylinder away starting cold since I want the T stat to be closed for the test (the gusher does not happen without the T stat inplace). Hopefully I can at least isolate the problem to a specific cylinder. What I do with that knowledge who knows but still I like to experiment so give me something to do. I can pickup a new head gasket and install the MN47 Tomorrow if I have the motivation for that. I am getting pretty good at removing and installing manifolds now, and since I just installed the head, I don't see any complications on the removal. I suppose I should plane on some 93 octane fuel, but for idle no load testing I assume I will be ok.

done for now, tried my 75 car engine, it warms up without any water puking, and passes the chem test perfectly. will post again once I get the maxima head on. I retested the spare engine compression test again, 165-170 across all. I also tried pumping up the rad to about 15 psi and then bore scoping the cylinders with a warm engine, could not see any obvious water leaking in. oh well its a mystery for another day.

ok no change at all, Still fails exhaust gas in radiator chemical test. Still pukes up water until the thermostat opens ( a lot of water, like 1/2 gallon). Exactly the same as before the head gasket, which is really no surprise since the head gasket looked fine. Guess I should be happy that I did not harm and have now done a head gasket pull. Engine still gets hotter than I think it should with extended idling (guess about 10 min it will get to 180ish even with a 160 T stat and a 3 row alum rad). I figure that has to be something in the head I am missing (or the block I suppose). I still have the maxima head and another head gasket on the way. I think will put on the maxima head just to see if the same results happen. Its going to up the compression due to the less volume in the head, but I figure it will just be a test to see if I can confirm this darn problem is a head issue or not. Before I do that I am going to make a proper timing chain holder tool. I realize now I had the wrong tool, It was smaller than what I should have gotten based on pics and now a PDF diagrame of the correct tool.