brianZortiz Posted May 9, 2013 Share Posted May 9, 2013 Hi, I keep posting topics here, but this one is a big mystery to me. I have a 100,000 mile block and I just did a mild head build with new cam, port match, etc... Well 2 weeks ago I had my car parked at work for a long shift and when I finished I drove off home, as I get 1 mile from home the temperature gets past 7/8 on the stock Datsun water temp gauge. As I get home I saw that there was not water in radiator. I filled it back up, checked again back in the morning before the drive to school. I lost water and car goes back to 7/8 temperature on gauge before heading home. I further inspected my car and saw that someone had slashed my lower radiator hose with a razor. I fixed the lower radiator hose, but now my car runs like crap. It idles at 550-600 and sometimes back to 850(regular idle), huge gas mileage loss and big power loss. I checked the compression and I get (1)110 (2)105 (3)107 (4)105 (5)110 (6) 105. Wet compression test: 1 (140) 2 (170) 3(180) 4 (210) 5(180) 6(170) I was really disappointed, but the only positive outcome out of this is that the compression holds. I checked to see if my timing chain jumped a notch but it didn’t. At TDC I’m still aligned with cam tower and cam at 2 on gear. My compression numbers are not a typo. The car runs, but it’s very underpowered. I did a rebuild on head 300 miles ago along other part upgrades. I need your help to see what the problem could be. The car does not smoke. I don’t have the compression numbers before rebuild, but was something I was going to do, but unfortunately this had to happen. Anything I can check to pin point problem? The car ran great after rebuild, except it needed timing to be synced. Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 10, 2013 Share Posted May 10, 2013 Your dry compression readings are kinda low . And readings went up with wet compression test indicate cylinder sealing problem . How much blow by do you have ? Check crank case pressusre . Have you done a block test , since it ran hot twice ? Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted May 10, 2013 Author Share Posted May 10, 2013 "How much blow by do you have ? Check crank case pressusre . Have you done a block test , since it ran hot twice ?" I am sorry, dont know how to do the three suggestions you gave me. Let me do a search online. Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 10, 2013 Share Posted May 10, 2013 You can check blow-by by removing your oil cap while the motor is running to see how much exh. smoke and/or pressure is coming out . High pressure indicates bad cylinder sealing or PCV system faulty . Block test requires a test kit which you can get from your local autopart stores . Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted May 10, 2013 Author Share Posted May 10, 2013 Thanks Domzs, Will check tomorrow and report back. Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted May 10, 2013 Author Share Posted May 10, 2013 Forgot to mention I have a bigger than stock cam, its 470 lift 280 duration. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted May 11, 2013 Share Posted May 11, 2013 How long were you driving it while hot? Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted May 11, 2013 Author Share Posted May 11, 2013 Not long. It never turned off on me. I just drove the car twice while hot. While the temperature was high I never drove more than 1 mile per day while the temperature was 7/8 on meter. Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted May 11, 2013 Author Share Posted May 11, 2013 Checked blow by at idle at operating temperature, no smoke or air pressure. Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 12, 2013 Share Posted May 12, 2013 Still overheating or losing coolant ? Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted May 12, 2013 Author Share Posted May 12, 2013 Nope, fixed that problem. Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 12, 2013 Share Posted May 12, 2013 ? Strange . So it ran fine after the head job ? Only thing i can think of is to do a leakdown test and check your valve clearance . Thought you might have warped the head when it got overheated . Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted May 13, 2013 Author Share Posted May 13, 2013 Yup, it ran fine. I guess I'm going to take it down to sunrise z or a z specialist here in SoCal to have them check. If the block seems to be the problem I guess I will throw in an L28. Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 13, 2013 Share Posted May 13, 2013 Heat does crazy thing to metal . LOL . Wouldn't hurt to check your valve clearance before you take it to the shop , it's easy enough . Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted May 14, 2013 Share Posted May 14, 2013 Any signs of sugar in the fuel? Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 14, 2013 Share Posted May 14, 2013 Any signs of sugar in the fuel? Doesn't explain low compression but i see what you're getting at . LOL . Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted May 15, 2013 Share Posted May 15, 2013 Yes. Sugar will gum up the rings and they will stick in the grooves. If some jackass cut the radiator hose they may as well put sugar in the tank. Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 15, 2013 Share Posted May 15, 2013 I haven't seen it but it could happen . Normally , sugar will eat fuel hoses and clog injectors . Had a few came to shop , had to replace hoses and injectors . Quote Link to comment Share on other sites More sharing options...
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