5 Star Rising Posted February 24, 2022 Share Posted February 24, 2022 Have a early 71 240Z that I have been working on off and on for years trying to get it on the road and there is always something to fix. In this episode we have blow-by blowing my oil dipstick out and spraying oil all over the engine compartment while just idling for 10 minutes.. I have not really ever got this car road worthy enough to say it did or didn't do it before. But I switched to triple Weber's and decided to remove all the PCV stuff and I added a catch can. I had done a compression test not too long ago and everything looked pretty even, but I thought maybe I had a stuck valve because the carbs dont run so well but that maybe just needs a fine tuning after rebuilding and installing them for the first time. As far as the catch can installed, this is how I routed the hoses and after looking at it I dont believe there is anyway to vent anything, it just comes off the valve cover, goes to the can on one side and the other side of the can goes to the lower crankcase pipe. Do you guys recommend a batter way to route the hoses or add a filter maybe? Not my engine in this picture but this is how I routed the can. It may not be right and not venting anywhere lol. Oops.. Quote Link to comment Share on other sites More sharing options...
NewZed Posted February 25, 2022 Share Posted February 25, 2022 3 hours ago, 5 Star Rising said: It may not be right and not venting anywhere lol. Oops.. You are correct, you blocked off the crankcase vents and are allowing pressure to build in the crankcase. You could disconnect the hose to the side of the block and leave it open at the catch can. That would allow venting and the catch can might actually catch vapors before they exit in to the engine bay. You would want to block the port in the side of the block if you do that, otherwise you'll have oil vapors leaking our down there. Quote Link to comment Share on other sites More sharing options...
AydinZ71 Posted February 25, 2022 Share Posted February 25, 2022 (edited) In order for the catch can you work, it has to be open to atmospheric (air) pressure. That way, gas flows from the engine, through the can, and back out somewhere. Attached is a schematic of my setup. You can either put a breather on top, or route the gases back to your intake the way I am showing (reduce stinky engine bay while car is on). why do you want a catch can anyway? Im putting one in reluctantly per race class rules. For many years, I have seen people put a breather filter at the valve cover and crank case vents and be done with it. Only downside as I said is the vapors just hang-around in the engine bay and some inevitably get into you cab. The can doesn’t help you here. You need to route the gases back into your intake system. Edited February 25, 2022 by AydinZ71 Quote Link to comment Share on other sites More sharing options...
5 Star Rising Posted February 25, 2022 Author Share Posted February 25, 2022 2 hours ago, AydinZ71 said: In order for the catch can you work, it has to be open to atmospheric (air) pressure. That way, gas flows from the engine, through the can, and back out somewhere. Attached is a schematic of my setup. You can either put a breather on top, or route the gases back to your intake the way I am showing (reduce stinky engine bay while car is on). why do you want a catch can anyway? Im putting one in reluctantly per race class rules. For many years, I have seen people put a breather filter at the valve cover and crank case vents and be done with it. Only downside as I said is the vapors just hang-around in the engine bay and some inevitably get into you cab. The can doesn’t help you here. You need to route the gases back into your intake system. Yeah after seeing how I routed my hoses like a dummy it made since that the pressure would not escape. I hope I didnt blow my head gasket as I found alittle white residue up under the oil filler cap and also way up on the oil dip stick. The oil seems ok and clear and clean and i didnt see any oil in the coolant but you never know. I will do a leak down test on it next week. The reason for the catch can is that with these triple Weber's there really Isn't a place in the cannon manifold to connect the line unless I tap into the brake booster port or drill and tap a new inlet but I dont want to add metal shavings into the intake while it's still on the car, the other reason for adding the can is that this car has a fresh white paint job including the engine bay and I didnt want black soot from breather filters getting all over the place, I think I will plug the bottom engine block port and run the hose from the valve cover into the inlet of the catch can and then add a breather to the outlet of the catch can. This catch can has a brass baffle filter on the inlet side to help catch alot of debris. I will see how it works. Cant believe I routed the hoses like that the first time lol. I unhooked the hose going from the catch can to the block last night and the pressure was released from the block and the blowby went away. I'm going to clean it up better this week. Thanks for the advice.. Quote Link to comment Share on other sites More sharing options...
AydinZ71 Posted February 25, 2022 Share Posted February 25, 2022 Ah! you are in Humboldt county. My in-laws live in Eureka, and we visit several times a year. Here are some thoughts for you. The triple Webbers with bare air-horns look cool as hell, but for long-term daily driving you really should have air filters on them. If you are putting on filters, might as well consider an "air box" to funnel cool air in-front of your radiator back to your carbs. Since your header is directly below your carbs, sourcing cool air for your intake will have a noticeable effect on your performance, especially in situations like traffic or continuous high-load operation. The caveat would be if you are applying a quality header coating like Swain, which will actually drop your engine compartment temperatures considerably. In that case, you can perform some sheet-metal work in your engine bay to ensure warm air from your rad is not flowing to your carbs, and the "air box" idea is not as necessary. If you do decide to funnel air from space in front of your radiator (as I am), you can have your catch can vent to your intake duct (ahead of your throttle bodies) which will just get sucked into the engine again and out the exhaust. I agree you do not want to connect your catch can vent to anywhere BEHIND your throttle bodies, as this will be unmetered gas and your carbs will be impossible to tune. If your oil is not milky, and your coolant does not exhibit oil sheen, you are probably OK. No harm in pressure-testing your cooling system to verify. Even pulling the head is pretty easy, and you just need another head gasket. Quote Link to comment Share on other sites More sharing options...
NewZed Posted February 25, 2022 Share Posted February 25, 2022 You're not going to blow a head gasket from excess crankcase pressure. Maybe a valve cover or oil pan gasket. The milky stuff would be because combustion gases contain water and you had blocked the path for combustion blowby to escape. Don't tear your engine down for the wrong reasons. Quote Link to comment Share on other sites More sharing options...
AydinZ71 Posted February 25, 2022 Share Posted February 25, 2022 Just now, NewZed said: You're not going to blow a head gasket from excess crankcase pressure. Maybe a valve cover or oil pan gasket. The milky stuff would be because combustion gases contain water and you had blocked the path for combustion blowby to escape. Don't tear your engine down for the wrong reasons. @NewZed is right. Crankcase pressure will never have gotten high enough to damage your head gasket. Your dipstick popping out is more than enough relief to have prevented any damage. Quote Link to comment Share on other sites More sharing options...
5 Star Rising Posted February 27, 2022 Author Share Posted February 27, 2022 On 2/25/2022 at 12:20 PM, NewZed said: You're not going to blow a head gasket from excess crankcase pressure. Maybe a valve cover or oil pan gasket. The milky stuff would be because combustion gases contain water and you had blocked the path for combustion blowby to escape. Don't tear your engine down for the wrong reasons. Good to know, I have seen what the oil and coolant looks like with blown head gaskets and this doesn't look like it BUT I will do a leak down test anyway because I just bought the damn tester and the car has a miss and at one point I thought I may have had sticking valves as it was fluttering pretty bad but then again I have not tuned these Weber's yet. Just want to make sure the mechanical part of the engine is working correctly before I start tuning these carbs and possibly rejetting if needed. Here on the coast the humidity is high and moisture could be under the valve cover mixing with the combustion gasses maybe creating the white sooty stuff under the oil cap. Quote Link to comment Share on other sites More sharing options...
5 Star Rising Posted February 27, 2022 Author Share Posted February 27, 2022 On 2/25/2022 at 12:17 PM, AydinZ71 said: Ah! you are in Humboldt county. My in-laws live in Eureka, and we visit several times a year. Here are some thoughts for you. The triple Webbers with bare air-horns look cool as hell, but for long-term daily driving you really should have air filters on them. If you are putting on filters, might as well consider an "air box" to funnel cool air in-front of your radiator back to your carbs. Since your header is directly below your carbs, sourcing cool air for your intake will have a noticeable effect on your performance, especially in situations like traffic or continuous high-load operation. The caveat would be if you are applying a quality header coating like Swain, which will actually drop your engine compartment temperatures considerably. In that case, you can perform some sheet-metal work in your engine bay to ensure warm air from your rad is not flowing to your carbs, and the "air box" idea is not as necessary. If you do decide to funnel air from space in front of your radiator (as I am), you can have your catch can vent to your intake duct (ahead of your throttle bodies) which will just get sucked into the engine again and out the exhaust. I agree you do not want to connect your catch can vent to anywhere BEHIND your throttle bodies, as this will be unmetered gas and your carbs will be impossible to tune. If your oil is not milky, and your coolant does not exhibit oil sheen, you are probably OK. No harm in pressure-testing your cooling system to verify. Even pulling the head is pretty easy, and you just need another head gasket. Yep Eureka is 15 minutes away, small world. I wrapped my headers with fiberglass wrap so the heat is not bad in the engine compartment. I have slip on foam air filters over the trumpets but no air box. Quote Link to comment Share on other sites More sharing options...
5 Star Rising Posted February 27, 2022 Author Share Posted February 27, 2022 Still going to do a leak down test but compression looks good. Spark plugs from cyls 4 and 5 are pretty different.. Quote Link to comment Share on other sites More sharing options...
manimal Posted February 28, 2022 Share Posted February 28, 2022 I bought a $35 ebay special and added some steel wool to the "filter" it has for the inlet. I can't say whether or not that really helps, but some of the more expensive catch cans do that. I plan on running a line from the out to carb filter baseplate eventually. The hose sizing is odd, from memory the valve cover is 16mm and block is 25mm. I cut some 1" 049 tube for the T body and some 5/8 035 for the catch can/valve cover ends to make a custom T. You could do the same with parts from a store specializing in hoses. Idk if this is common, but I have a local store which does custom hydraulic, water, air, etc lines and has adapters out the wazoo. I bought the fabric coated hose there as well. Leak down test is a good idea, but something even easier you might want to try is UV coolant dye + a black light if you are concerned about a coolant leak. The UV dye survives the combustion process and is visible at the tailpipe if there is a coolant leaking into the combustion chamber. If it's leaking into your oil you'll find there. Quote Link to comment Share on other sites More sharing options...
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