Guest bang847 Posted May 29, 2002 Share Posted May 29, 2002 Okay guys i got no compression of those two cylinders which have white soot on the smog piping.. any idea what is happened? I think it is rings but i just wanted to hear someone else's input.. Quote Link to comment Share on other sites More sharing options...
DAW Posted May 29, 2002 Share Posted May 29, 2002 Head gasket/warped head between those two cylinders. White is from steam from water leaching out of water jacket passage in gasket. Another possibility, though remote, would be that the intake manifold gasket was leaking for those two cyls, leaning them way out and you burned holes in the pistons. It's the head gasket. DAW Quote Link to comment Share on other sites More sharing options...
Tony240ZT Posted May 29, 2002 Share Posted May 29, 2002 I'd say you were running lean on that carb, and you burned your valves. Now there is burned on carbon to those valve not allowing for a good seal. Which snow balls. Do a leak down test, I bet your rings aren't half as bad as your exhaust valves. Quote Link to comment Share on other sites More sharing options...
DAW Posted May 29, 2002 Share Posted May 29, 2002 It's not your rings. There would be a lot of oil and there isn't. I think Tony may be right re the back carb being lean. Was the engine pinging? DAW Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted May 29, 2002 Share Posted May 29, 2002 the engine was chuggin bad.. barely ran.. after i got it home it wouldnt run anymore.. i didnt seem like it was pinging... actually it probably ran rich on #1-#3.. that is when i had a stuck float.. and the carbs were dripping gas... before i started pulling things off I could start the car if i squirted liquid into the manifold... (gas/carb cleaner) Anyways I am comtemplating my next move on this car.. is it definite that i should pull the head? only 2 cylinders had compression over 100psi... how do i do a leakdown test? Thanks guys Quote Link to comment Share on other sites More sharing options...
Tony240ZT Posted May 29, 2002 Share Posted May 29, 2002 By the way, when water gets in your cylinders it cleans things really well since it turns into steam. You've heard of steam cleaning your engine compartment, right, steam is great at getting rid of burnt on oil/carbon. Look at pictures where people have had a blown head gasket and water came into the cylinder, you'll see that the cylinder with water has little to no carbon, and is sparkly clean. Kinda makes you wonder if you should inject water every once in a while to clean things out. I'm sure if done properly it could be a good thing, but too much and you could -try- and compress the water, which doesn't work too well Pull the head, have a fresh 3 way valve job done by a confident head shop. If you've ever thought about going for a different cam now is a good time. While you're at it look at other parts that could wear like timing chain, tentioner, seals, etc. Clean up the deck, bolt on the freshly resurfaced head with a fresh head gasket, torque properly, set the carbs up correctly and you will be amazed at what a difference it'll make. A leak down test is when you put oil into the cylinder to make a temp seal for the piston. Do the presure test again on the cylinder and this will tell you if it is your valves leaking, since the cylinder will have a really good seal. You will probably have very similar results in doing this since I'm pretty sure the majority of your loss in compresion is due to burned valves. If for some reason though you get a good number for compression when using the oil then it is your rings that are bad. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 30, 2002 Share Posted May 30, 2002 I have to disagree on the leakdown test. I believe a leakdown test involves pressurizing the cylinder with air, and measuring how much it loses. There is a specific tool that is used, but since I have never tried it, I am not sure much more beyond that. Corky Bell's book indicates leakdown of 91 or less as impaired,( 9% leakdown or more ) so you will need to fix it. Depending on where you hear the air leak, that indicates where you have a problem, be it a head gasket, valve(s) or rings. If you are getting water into a cylinder, chances are that one will need rings since water does not compress very well. Probably piston(s) too. For now, do a compression test, and record your figures, and then repeat only adding some motor oil to each cylinder thru the spark plug hole. If your compression goes up, then you have ring problems, if not, valve problems. Generally. Good luck with it. Quote Link to comment Share on other sites More sharing options...
DAW Posted May 30, 2002 Share Posted May 30, 2002 I think KD Tools sells spark plug hole adapters to put a compressed air hose to each cylinder in turn. You want the piston at TDC on compression stroke (so that both valves are closed). If you've got air coming out of the carbs or intake port of the head: intake valve leaking; exhaust, that valve; oil cap hole of valve cover: rings or piston hole; radiator cap: head gasket or crack in block or head. If you've got no compression on two cylinders though, the problem may be visible to you without a test. On another note, it's time to consider the economics and logistics of performance. The pic of your car looks like it's a '72. If so, it will have an E88 head with combustion chamber volume to yield about 8.5:1. There are some rare E88 heads which have a smaller chamber volume like the '70-'71 E31 (but shaped different) which yield about 9.0:1. Regardless, they have 33mm exhaust valves and 42mm intakes. L28s have 35mm and 45mm respectively. The L24 exhaust valve is somewhat limiting to breathing and performance and Nissan put in a 35mm valve on L26s and later L24s. If you're doing a valve job on an early L24 it would benefit from installation of L28 exhaust valves. These can be installed on the L24 seats with machining (intakes need new seats). What I suggest you do is to go to your favorite JY and pull a head off the lowest mileage '81-'84 Maxima L24 you can find and if the chambers look uniform in color and no oily deposits, bolt it on. The head will be a P79 but it is very different from the 280ZX P79. The Maxima has small chambers for 9.0:1 compression on your car, better quench design than your E88 or the E31 (less pinging tendency), already has 35mm exhaust valves (has 42mm intakes), and has notches in the intake ports so that you can install f.i. in the future. You will want to transfer your cam & rockers to this head. Exhaust manifold? Use the Maxima or 280ZX with an O2 sensor for future use. Forget about the square exhaust port vs round port issue between the head choices, it's completely meaningless in the street engine you're building and the round port exhaust liners accomplish the same thing that those air supply tubes on your original manifold do, i.e. promote burning of all hydrocarbons in the exhaust gases. Look at the pros and cons and bang for the buck. There's a good chance you can pick up a Maxima head that needs nothing and with the money you saved from not doing your valve job you might be able to pick up the distributor with IC module and the entire fuel injection set up from the Maxima. DAW Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted May 30, 2002 Share Posted May 30, 2002 so many choices so little time... actually the car is a 70.. #1663... (i dont know if that is worth mentioning) it has a L26 block and a E88 head.. I just looked into the intake ports and i looks like the valves are burned... I guess the question on my head is what do i need to do.. I'm not into getting a high performance car yet... as of now it is a "get it running keep it running project"... Also I am short on mechanical skills. I need to build up more experience before i even think of swaps.. So now... given that the intake valves are burned I should proceed with pulling the head? I cant do a compression test right now cuz I pulled out the starter already... shall i put it back in to confirm if the rings are bad or shall i skip that step?? Again thanks for all you guys help! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 30, 2002 Share Posted May 30, 2002 Looks like oil in the exhaust passages from the picture. Is the inside tip of the rear exhaust pipe oily or sooty or wet with water. You definitely want to pull that head and check the valves and pistons for cracks and holes. Your compression is poor. What is the lowest? Any oil in the radiator or water in the crankcase oil (gray goo)A water oil combination will indicate a head gasket problem. You may have a timing fuel adjustment problem but it looks like a rebuild to me! Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted May 30, 2002 Share Posted May 30, 2002 actually everything was very dry when i pulled... from a earlier post i was trying to get that manifold off so i sprayed wd40 that is probably what youre looking at.. i also sprayed carb cleaner down the manifold to see if it was coming out between the flanges.... also there is no oil in the water and no water in the oil... i thinking it is only a burnt valve... but again i need you guys opinion.. Thanks Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted May 30, 2002 Share Posted May 30, 2002 Not much you can do about a blown head gasket or burnt valves. Once the damage is done; it is done. If the damage has existed for an extended period of time; and the the engine is alowed to rest. "Rust" builds up inside where there should've been an oil film. But if you have burnt vavles then anything you can do should only be thought of as a [very temporary] band aid. About the "steam cleaning" effect; my high school buddy's dad was a master mechanic & owned a small multi line shop in Dallas for many years. I remember a story he relayed about using water to remove the carbon from valves and piston tops. He said while working the throttle by hand he could pour minute amounts of water into the carb (notice I said minute amounts) and then work the throttle by increasing the rpm's. The only problem he ever encountered was to "NOT LET THE ENGINE DIE" while performing this procedure. Once the engine dies w/water in the carb-you've really got a problem in restarting. Another point, when using WD40; understand that it is not a "lubricant". WD40 stands for "WATER DISPLACEMENT" and the "40" represents the 40th attempt NASA made on this formula before getting it right. The bottem line is that wd40 evaporates. So, dont use it as a lubricant. Definately use it when you think water is somewhere it doesnt belong. But when you need to loosen a seized bolt or screw; use Liquid Wrench or its equivalent. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
DAW Posted May 30, 2002 Share Posted May 30, 2002 You're going to be pulling the head so plan in advance to avoid problems that will make a lot more work. You want to bring the timing mark up to TDC on the compression stroke of #1 cyl, i.e., the dist rotor pointing at #1 cap terminal, the #1 valve lobes angled upwards (not holding valves partially open). Break the cam sprocket bolt loose by whacking the end of a 19mm box-end with a hammer, but leave it on once loose. Then you need to insert a wooden or plastic block between the strands of the timing chain down in the timing cover so it won't move (get loose and force you to pull the cover, radiator, fan, maybe drop the oilpan some, double the time invested). There are two bolts with 10mm heads at the front of the head/top of timing cover. Remove them first. Look up the head bolt tightenning sequence and follow it in reverse to loosen head bolts. Breaker bar into an exhaust port, lift gently, and work along the head until it lets loose. Maybe it was too much info re the head swap but think ahead, the Maxima head also has hardenned valve seats for use with unleaded gas, your E88 probably does not (you can tell on inspection once the head's off). DAW Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted May 31, 2002 Share Posted May 31, 2002 if machining cost are going to be that much i would definetly consider getting a JY head... should i only consider a maxima head? is the 280zx heads out of the question because on displacement difference? also i cant turn my engine right now.. I have a 101 pc craftsman ractchet set and the biggest socket i have is a 1" what is the size for the crank bolt? Quote Link to comment Share on other sites More sharing options...
DAW Posted May 31, 2002 Share Posted May 31, 2002 You are not limited to the Maxima head and any L24, L26 or L28 head will bolt on. However, they will vary in how much compression ratio they will yield on your engine. Higher compression is a plus re performance, mpg and efficiency but if too high it will cut short the life of the engine and/or require special racing ga$oline to operate it even for daily driving. Your engine is relatively smaller displacement so you don't really have worries about getting too high a c.r.; just too low. It's all about selecting a head that gives the best combination of factors, including access, time consumed, $$, performance, longevity, and most important, fun factor. The L28 heads all should have hardened valve seats for unleaded gas as do the Maxima L24 heads. The main difference, other than intake valve size (which doesn't matter for your displacement and intended use) is the volume and configuration of the combustion chambers. The Maxima head would be better for higher quench design/less ping than the L28 for a given c.r. Running a Maxima head on a 280Z would produce a very high c.r. but on a 240Z it would be great because of the lower cylinder swept volume. I'd recommend that you not hesitate to substitute a head that makes sense and represents an evolution in technology over a dozen years. Which is better, points ignition or electronic? Finally, you're likely going to pay less for a Maxima head at a JY than when you say "for a 280Z." DAW Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted May 31, 2002 Share Posted May 31, 2002 hmmm. I think I get it now... actually I am running a l26 block... any suggestions? that means if I slap on a maxima head i will get higher than normal compression ratio? I am a cheap guy and I prefer buying the econo-gas 87 octane... what kind of compression ratio will require using higher grades? I hope to keep using cheapie stuff. my other car has a l24 with a e31 so that is running on 87 octane pretty ok so anything under 9:1 should be ok? a L24 head on a L26 should bring me up to that range? also I was wondering about porting the heads.. but is that only viable in a head rebuild or can i try to grind down stuff with the valves and cam still on a JY head? another concern of mines is also the condition of the JY heads.. usually when i get to them the valve covers are usually off.. anything could of gotten it right? if i find a good condition head but it had no valve cover when i got to it shall i pull it? is it easy to flush out any contaminantes that other JY monkeys might have put in?? Again thanks guys,, I really appreciate the walk through... Quote Link to comment Share on other sites More sharing options...
Mike C Posted June 1, 2002 Share Posted June 1, 2002 Pull all the plugs out and you can probably rotate the motor by hand with a pair of gloves on the crank pulley. Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted June 1, 2002 Share Posted June 1, 2002 Pull all the plugs out and you can probably rotate the motor by hand with a pair of gloves on the crank pulley. I'm weak.... any answers regarding the JY heads? am i limited to a maxima head? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 2, 2002 Share Posted June 2, 2002 In reference to "steam cleaning" your engine; my father used to run a pint of 50-50 mix of grain alcohol and water thru his engine every six months by revving the engine to 2500-3000 rpm and spraying just above the carb opening with a windex bottle. You have to be careful though. Too much at one time will hydraulic lock a cylinder and bend a rod. Quote Link to comment Share on other sites More sharing options...
DAW Posted June 2, 2002 Share Posted June 2, 2002 It would be a lot better to find a JY head with a valve cover on it, or looks to be just recently removed, but it's the cam that's going to suffer most from exposure to rain & dirt if the hood has been left open and you could transfer your cam/rockers/lash pads directly to the JY head. A couple of things you mention don't really mesh, i.e., thinking about porting and polishing the head but running strictly 87 octane gas. They just don't go together. Increasing c.r. over stock will require higher octane gas but could improve mpg and will increase power, whereas the time & money into porting and polishing a stock lower compression head would not offset the savings of using low octane gas. Money would be better spent on higher octane gas using more c.r. The Maxima head I'm referring to, used on an L26 will be higher compression than your L24/E31 combination and you'd have to use at least 89 octane gas. If you insist on using the lowest octane gas then you'd probably be best by using an N42 head off a '75-'76 280Z. It won't increase compression, has hardenned valve seats, and square exhaust ports to match your manifold. DAW Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.