herb Posted May 1, 2017 Report Share Posted May 1, 2017 any advice on what to do , I have a set of dual Hitachi's on my L 20 engine I've changed to a closed chamber head and this head does not have the water chamber that cools the intake manifold. Can using it without the flow have detrimental results ? Thanks HM 1 Quote Link to comment
G-Duax Posted May 1, 2017 Report Share Posted May 1, 2017 The water passage wasn't there to cool anything. It was there to heat the intake to fight icing of the carbs in cold weather. 2 Quote Link to comment
wayno Posted May 1, 2017 Report Share Posted May 1, 2017 What head is it you changed to? You can drill the holes in the head if you want, just put the intake/exhaust manifold gasket on the head, mark where the water passages are with a marker and then drill the holes. 3 Quote Link to comment
herb Posted May 1, 2017 Author Report Share Posted May 1, 2017 OK Thats good news. Thanks HM 2 Quote Link to comment
wayno Posted May 1, 2017 Report Share Posted May 1, 2017 But I still want to know what head casting you have that doesn't have the water passages? 1 Quote Link to comment
herb Posted May 1, 2017 Author Report Share Posted May 1, 2017 had to go out and look its a U 67 1 Quote Link to comment
Crashtd420 Posted May 1, 2017 Report Share Posted May 1, 2017 I thought the u67 heads were an open chamber? 1 Quote Link to comment
john510 Posted May 1, 2017 Report Share Posted May 1, 2017 The water passage wasn't there to cool anything. It was there to heat the intake to fight icing of the carbs in cold weather. The water passages are also there to help cool the intake manifold.Without it connected to the intake you will have problems in hot weather while idling. 1 Quote Link to comment
datzenmike Posted May 1, 2017 Report Share Posted May 1, 2017 U67 are open chamber heads not closed. The water cooled/warmed feature just needs two holes drilled in the head. Just use the gasket as a template. I did this last year. Works just fine. Warming the intake won't prevent carburetor icing, only warming the intake air after it passes the carb. To prevent carb icing you need need the auto temp control (ATC) working. This is the metal shield on the hot exhaust manifold and the pipe to the air filter snorkel. A temperature controlled valve in the snorkel mixes hot and cold air maintaining it at about 100F. With a controlled intake air temp, the engine runs in better tune over a wider range of weather conditions. 1 Quote Link to comment
herb Posted May 1, 2017 Author Report Share Posted May 1, 2017 Ok my mistake open chamber head u 67 and I appreciate the advice will drill out the head next time I have it opened up Thanks one less worry Quote Link to comment
distributorguy Posted May 2, 2017 Report Share Posted May 2, 2017 Don't bother. If anything, the engine will run better staying cool, without the water passing through the manifold. 1 Quote Link to comment
datzenmike Posted May 2, 2017 Report Share Posted May 2, 2017 Not really. It removes radiated heat from the too close exhaust manifold that bakes the intake. This is particularly a problem in the hot summer. In cold weather it warms the air providing a quicker warm up. Together this provides a wider range of usable stable air temperatures and tuning and the engine runs better. All L series 4 cylinder engines have it but the '75-'77 L20Bs with U67 heads. 1 Quote Link to comment
distributorguy Posted May 2, 2017 Report Share Posted May 2, 2017 Its a problem with the late carb and manifold, not the early dual carb setup where the float bowls are extended away from the manifold. Quote Link to comment
datzenmike Posted May 2, 2017 Report Share Posted May 2, 2017 I think all SUs were prone to excessive heat absorption and need heat shielding. In addition this is and Z20B. The SU intakes had water ports, they should be used. 1 Quote Link to comment
wayno Posted May 3, 2017 Report Share Posted May 3, 2017 I have a lot of trouble with my SU bowls boiling these days when it gets over 80 degrees and I get off the freeway and hit all them god damned traffic signals at Mill Plain and 205 south bound, the lack of air moving thru the engine compartment screws things up, I have the heat shield but it doesn't have that material on it anymore, I believe the worst thing is that I have a header, it just jerks and misses until I get moving again, and once above 30mph for 10/15 seconds it cools and I have no more issues. Way too many signals in that area and too many vehicles, that whole section of Mill Plain was designed by a tard, ya get off the freeway and come to a stop, their way of fixing the south bound off ramp congestion was to make the off ramp a 1/2 mile long instead of fixing the issue. Anyway I have always drilled the holes in the head myself, anything that helps keep the intake manifold warm during the winter cold is a plus in my world, but sometimes the summer screws with ya. :lol: Quote Link to comment
john510 Posted May 3, 2017 Report Share Posted May 3, 2017 Don't bother. If anything, the engine will run better staying cool, without the water passing through the manifold. No. Quote Link to comment
banzai510(hainz) Posted May 4, 2017 Report Share Posted May 4, 2017 same here above 80deg with my mikunis and a stop light 1 Quote Link to comment
Draker Posted May 4, 2017 Report Share Posted May 4, 2017 I get it the same thing on fresh carbs from z therapy. Quote Link to comment
distributorguy Posted May 4, 2017 Report Share Posted May 4, 2017 Having owned my MG running real SUs for 17 years, they don't absorb heat. I have a set on the practice motor for the race truck as well, and there are no signs of heat, sitting right above an unwrapped header, running infinitely long parked in the driveway. You'd think that would cause a problem, right? On top of that its over 11:1 compression. I think you guys might just need to learn how to balance a set of carbs. Airflow AND piston lift matter. And most of you guys live in warm country. Try MN on for size in January. I don't need a heated manifold for my SUs. That's why fresh carbs from Z-therapy don't work either. They still need to be tuned/balanced on the engine. By the way, that's not a heat shield between the carbs - its merely a simple steel bracket to hold springs and the throttle cable. [/url]">http:// Quote Link to comment
G-Duax Posted May 4, 2017 Report Share Posted May 4, 2017 And I am in Texas, and already have had about 2 weeks of 90+ days. I never run that damn water passage. Plug them on every car I have. My headers get ceramic coated also, and I take the extra step of layering my heat shields, insulation, another layer of aluminum, another layer of insulation, and another layer of aluminum. Easy to do, cheap, and works. Another source of heat into the carbs is through the mounting studs/bolts. I drill the holes out in the carbs, buy a length of phenolic tube from McMaster-Carr, and cut sleeves, and then add phenolic washers under the nuts/heads of bolts. This eliminates all metal contact from the head, to the carb(s). Along with a fuel bypass, don't have a boiling gas problem, ever. Even on +100 degree days. Quote Link to comment
datzenmike Posted May 4, 2017 Report Share Posted May 4, 2017 Bull shit. It's lined with asbestos or they were unless it falls off. Why make it look like a heat shield if it's only for springs????? Maybe the Skinner's Union carbs don't over heat or maybe it's Minnesota weather but everywhere else, Hitachi's and heat don't mix. 1 Quote Link to comment
wayno Posted May 5, 2017 Report Share Posted May 5, 2017 Let me be more clear, I haul a trailer with 2 complete pressure washing systems in it plus chemicals, sprayers, a concrete cleaner, extra parts, extra hoses, 3 gas cans, it has so much in it now that I cannot even lift the tongue off the ball anymore, and a lot of the time I also am hauling near a ton of debris in the truck flatbed. Now when I am on the hiway my foot is pretty deep into the pedal,, it runs a little warm when it is hot out, now when I take the Mill Plain exit I go from 65ish to a stop at the first signal, I can usually get thru that light without an issue unless there is a big backup, but the second and third signals are a bitch, 90 percent of the time I get stopped at both them signals for a while, I start having issues by that third signal, and if I get stopped at the 4th and 5th signals I have problems, idle is fine but when I give it the gas the engine starts rebelling and cutting out, if I can get thru the 4th/5th signals and get to 3rd gear it smooths out and I have no more issues at all. The block is so hot after exiting the freeway, and coming to a stop like that just heats the SU carb bowls up, at least that is what I believe is happening as once I get moving and cooler air gets into the engine compartment I have no more issues. I know how to adjust my SUs, Dan Garrison(raced Roadsters back in the day) actually checked my adjusting/tuning of them the first time I ever adjusted them, he said I did it right, I have been running them for over 20 years now and they are getting tired as I cannot adjust them by spark plug color anymore, the truck still runs fine so I keep driving it with them carbs, but they have had this heat issue for a very long time. By the way, I also use a modified 510 air filter housing on this truck, it hangs down pretty low and likely reflects heat back towards the bowls, it's pretty tight in that area, like a little tunnel on the underside of the carbs, if I am moving air flows thru and exits under the truck, but if I am sitting still there is not a lot of air movement, even my power steering pump blocks the air flow. Quote Link to comment
datzenmike Posted May 5, 2017 Report Share Posted May 5, 2017 wayno, the 280zx (maybe the 280z also) have small electric fans on the right side of the engine down by the oil pan and plastic ducts up over the valve cover to blow cooling air over the injectors and intake. Check it out... Quote Link to comment
wayno Posted May 5, 2017 Report Share Posted May 5, 2017 wayno, the 280zx (maybe the 280z also) have small electric fans on the right side of the engine down by the oil pan and plastic ducts up over the valve cover to blow cooling air over the injectors and intake. Check it out... It only happens when it is hot out and I exit the freeway, I guess I need to schedule jobs closer to home on the hot days so I don't have to use the freeway. :lol: I suppose I could get rid of that air filter housing and put pancake filters on the carbs, that would open it up in there, that would also make putting a power brake booster and dual reservoir master brake cylinder possible for this truck, but I am lazy and the brakes work fine, so I keep putting that off. Quote Link to comment
datzenmike Posted May 5, 2017 Report Share Posted May 5, 2017 Electric fan with switch would be easier. Quote Link to comment
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