zuperair Posted September 8, 2009 Share Posted September 8, 2009 I've got a '77 280 with the stock L28 block and fuely head that I converted to an e31 head for use with triple dcoe webers. Before the conversion, the temp gauge was always about an 8th inch left of center. Pretty standard with many of the other z's that I've owned. After the head swap, the temp settles in for a moment at dead center...but after about 2 or 3 miles starts it's slow climb. It's highest point has been about an 8th of an inch left of 250. Not sure if it's stable there, since I shut it down as soon as possible (till now I've only test drove it no more than 10 miles). I used a raytemp gun on the head, and it showed around 185-190 near the intake ports, and about 205 near the exhaust ports. Intake temp avg about 160...header temp at head about 300. Block's temp is about 205. So far, I've re-timed it....put in a new thermostat (180), checked fluid of course, and I've ordered a new sender. Thing is, the Raytemp numbers aren't where the gauge is....but then again, this gauge worked perfeclty before, I'm using the same sensor, but it's definitely getting hot. Any suggestions would be greatly appreciated. Here's what I've got... Stock Parts 77 L28 Block Stock coil and Ballast resistor New parts e31 Head with Schneider cam, full valve job, top end is new Triple 40mm DCOE Webers (new) Hooker Super Competition Jet Hotted 6 to 2 Header Mallory mechanical advance distributor Aluminized 2 1/4" dual exhaust with Glass Packs and Ansa tips I've got an aluminum radiator for the car (new) and I was planning on putting that in after paint...but I may put that in just to test. Deal is... the stock radiator is like new, and it never had an issue. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 8, 2009 Share Posted September 8, 2009 Why aren't you shooting the radiator with the temp gun? That's where you should get the most accurate temp numbers. On the surface it sounds to me like a bad temp sensor. The other thing to look out for on a fresh conversion is the thermostat, especially if you didn't change it out. I was told that you should always replace the thermostat if it has been used and then goes dry. I didn't buy it until I had two Toyota thermostats take a dump on me during headgasket swaps. Now I just change the thermostat every time the coolant gets dumped. Quote Link to comment Share on other sites More sharing options...
zuperair Posted September 9, 2009 Author Share Posted September 9, 2009 I thought I posted the radiator temp...guess I forgot that little tidbit. I did shoot it, and it was between 185-200 depending where I shot it. I did put in a new thermostat...I meantioned that, but didn't list that under new parts which I should have. Also, while searching...I ran into your thread from '03 "z car getting hot". Read through that, but unfortunately we have different issues (obviously your's is sorted by now) since mine gets hot while moving. Curious...was it the wrap in your case that was causing the overheating issue? I jet hotted my header....and figure there's no way it could cause this issue. But 'till it's solved I hate to rule anything out. Anyway....I'm sorting out the upper radiator hose for my aluminum radiator. I installed it and once I get the hose I can test it out...although, I'm not holding out much hope at this point. Everything I've come up with through research tells me the e31 works fine on an L28....anyone feel differently? Quote Link to comment Share on other sites More sharing options...
smokeybear Posted September 9, 2009 Share Posted September 9, 2009 Did you get the correct head gasket? If not you could be partially if not fully blocking a couple of the cooling ports. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 9, 2009 Share Posted September 9, 2009 Also, while searching...I ran into your thread from '03 "z car getting hot". Read through that, but unfortunately we have different issues (obviously your's is sorted by now) since mine gets hot while moving. Curious...was it the wrap in your case that was causing the overheating issue? I jet hotted my header....and figure there's no way it could cause this issue. But 'till it's solved I hate to rule anything out. It was just a radiator with a bunch of crap in it. I don't think the header wrap was the cause in my case either in retrospect. BTW I ran my old engine which was L28/E31 (same head, different bottom end) for about 40K miles daily and never had any overheating issues aside from the one time the fan belt just decided to let go for no reason. Quote Link to comment Share on other sites More sharing options...
zuperair Posted September 9, 2009 Author Share Posted September 9, 2009 Well, I've got it figured out. Sort of.... I found an upper radiator hose today that would work with my aluminum radiator....tossed in some new fluid and went for a test drive. Seems my stock radiator was the culprit, since I had no issues whatsoever. Could see the tick in the needle on the temp gauge when the thermostat would open...ran it hard, ran it soft, let it idle in the driveway for about 15 minutes. Dead center on the gauge! I took numorous readings with the Raytemp gun.... Head on the pass. side 155 all the way across. On the intake exhaust side 160 near the intakes, 195 near exhaust ports. The block was 155 (wooohoooo), and the radiator 145. Couldn't be happier. Now I can move down my list to the next thing. Getting very close to done now. Odd thing about the stock radiator...never had a problem with it. Always ran cool. I wonder if there was something in the head from the build that plugged up the radiator somehow. It's about the only thing that makes sense at this point. Anyway, thanks for the replies....I'll be posting up pics of the project very soon. Quote Link to comment Share on other sites More sharing options...
woldson Posted September 10, 2009 Share Posted September 10, 2009 Maybe crud finally blocked enough passages from scaling freeing itself when coolant was not present. Happens in plumbing all the time. Good job. Quote Link to comment Share on other sites More sharing options...
zuperair Posted September 12, 2009 Author Share Posted September 12, 2009 Interesting.....hadn't thought of that scenario. Radiator was without fluid for about 3 months. That could be the answer. Guessing if I had it boiled, it'd be fine. Worth keeping on the shelf at any rate. Thanks! Quote Link to comment Share on other sites More sharing options...
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