Woc123 Posted April 2, 2018 Report Share Posted April 2, 2018 Hey hows it going i have a datsun 1971 521 and i have it on mikuni Phh44mm. Im getting alot of blow by i think i have the whole crank case set up wrong if semeone can help me thanks 1 Quote Link to comment
banzai510(hainz) Posted April 2, 2018 Report Share Posted April 2, 2018 I have 40s and I open vent the crankcase. meaning the tube coems out and nothing on it. and at idle if alot of smeoke comes out then you have blowby. One can ck by running car at night and use a flashlight youll see the smoke in the air. once you rev up the motor the crackcase will suck in air. 1 Quote Link to comment
G-Duax Posted April 2, 2018 Report Share Posted April 2, 2018 Blow-by is just as the name suggests, combustion gas blowing by the rings. Worn out rings. Time to freshen the engine. 1 Quote Link to comment
banzai510(hainz) Posted April 2, 2018 Report Share Posted April 2, 2018 Was just reminding him to open case the vent. I seen a guy on here plug the cranksase vent with a sparkplug thinking it needed to be plugged. Of coarsse depending on manifold I seen Mikuni have the ports to a hose for a PCV valve but rarely seen them used 1 Quote Link to comment
mainer311 Posted April 2, 2018 Report Share Posted April 2, 2018 I have 40s and I open vent the crankcase. meaning the tube coems out and nothing on it. Why wouldn't you just cap the PCV with a PCV breather filter? 1 Quote Link to comment
Doctor510 Posted April 2, 2018 Report Share Posted April 2, 2018 Do a leak down test, probably bad rings major surgery, it's an L16 right? 1 Quote Link to comment
banzai510(hainz) Posted April 2, 2018 Report Share Posted April 2, 2018 Cap the breather? I notice they kinda plug up with oil . I run a tube down beneath and on the valve cover also. Not a expert on this but thats what I do. I guess a fancy catch can and breather would be cooler 1 Quote Link to comment
G-Duax Posted April 2, 2018 Report Share Posted April 2, 2018 Doesn't do a thing about the problem.... 1 Quote Link to comment
banzai510(hainz) Posted April 2, 2018 Report Share Posted April 2, 2018 My car dont have lots of blowby so I dont worry about it sold my yellow510 it had 44s and no blowby and sold 2 extra sets of Mikunis lastyear so only 40s on my beater 510 and a DGV on my 521(w pcv sytem)once these wear out Im out of the scene 1 Quote Link to comment
G-Duax Posted April 2, 2018 Report Share Posted April 2, 2018 once these wear out Im out of the scene Yeah, that is what we all say.... It's an addiction, and there is no 'Datsun Anonymous'. 1 Quote Link to comment
mainer311 Posted April 2, 2018 Report Share Posted April 2, 2018 "Blow-by" can also be caused by worn valve guides/seats. 2 Quote Link to comment
Dolomite Posted April 2, 2018 Report Share Posted April 2, 2018 Miriam Webster’s redneck dictionary defines blow by as similar to a drive by but with fellatio. 2 Quote Link to comment
G-Duax Posted April 2, 2018 Report Share Posted April 2, 2018 "Blow-by" can also be caused by worn valve guides/seats. No.... 2 Quote Link to comment
Woc123 Posted April 2, 2018 Author Report Share Posted April 2, 2018 I want to know if the set up it has is right it has the crank case hose is going to a T then one hoes is going to the carburators and another hose is going to the hoes that goes to the head cover is that right or do they need to be individually and it doesnt have a pcv valve either i think the set up is wrong 1 Quote Link to comment
banzai510(hainz) Posted April 2, 2018 Report Share Posted April 2, 2018 So 1 hose is going to the carb aircleaner? Never seen a port for 44mm sidedrafts like what your talking about unless a portwas made so a hose can go in. or maybe you mean manifold port? Im just wondering if your over pressure the system photo will help what you got going on 1 Quote Link to comment
Woc123 Posted April 3, 2018 Author Report Share Posted April 3, 2018 How can you ipload photos on here? Quote Link to comment
mainer311 Posted April 3, 2018 Report Share Posted April 3, 2018 No.... Yes. Excessive pressure/smoke under the valve cover, sometimes thought to be caused by worn rings when it’s not. Quote Link to comment
mainer311 Posted April 3, 2018 Report Share Posted April 3, 2018 It sounds like both the valve cover and his crankcase breather are both feeding a single hose that is routed to the air filter housing. Sounds...custom. You could always just remove the hose from the air filter housing. Route it down below the truck and let it vent to atmosphere. No sense in crudding up a nice Mikuni by blowing oily shit all over it. 1 Quote Link to comment
Woc123 Posted April 3, 2018 Author Report Share Posted April 3, 2018 Thats exactly how it is mainer311 i dont know if thats how it should be or if the guy who had it before me ran it like that but to me it doesnt seem right . So your saying the hose that goes to the crank case just route it down below the truck? Quote Link to comment
wayno Posted April 3, 2018 Report Share Posted April 3, 2018 The valve cover hose is supposed to go to the air filter housing, the engine case breather tube is supposed to go to the PCV valve, the hoses are routed this way to keep the engine case/block clean(PCV valve) and to filter the air when the valve cover outlet sucks in air like when under acceleration. The way you have it now will release any pressure created by blow-by to keep the blow-by from blowing your seals out and making it leak oil everywhere, but your oil will not last as long and the inside of the block will build up this layer of crud and make it a dirty mess when it is torn down, I have seen heads that had this brown/white gooey oil crud on everything when the valve cover was removed because the engine didn't have a PCV valve. It has been a long time since I seen that gooey crud as that was when they didn't have PCV valves on engines, all gas engines have them now and have had them since the late 60s, back then one was lucky to get a 100,000 miles out of an engine, now 300,000 miles is not uncommon. Quote Link to comment
G-Duax Posted April 3, 2018 Report Share Posted April 3, 2018 Yes. Excessive pressure/smoke under the valve cover, sometimes thought to be caused by worn rings when it’s not. No... Valve seal, worn guides, worn seats don't create blow-by. They will create smoke out of the tail pipe, but that isn't blow-by. There is no pressure at the valves that can in any way produce pressure in the head (and crankcase, as they are connected by rather large passages). The intake valves will only create a vacuum, and that draws oil into the intake port when guides/seals are shot, and why an engine with worn out valve seals will smoke, especially at idle, and when slowing down, using the engine to brake, as when down shifting before a corner. ..... the inside of the block will build up this layer of crud and make it a dirty mess when it is torn down, I have seen heads that had this brown/white gooey oil crud on everything when the valve cover was removed because the engine didn't have a PCV I haven't run anything crankcase related to a manifold, air cleaner, or carb in years, and I don't get any white crud in my engines. Normally, white/brown crud is from minor head gasket leaks, and water mixing with the oil. Maybe it's because I live in Texas, and condensation never builds up in an engine due to dry air, and mostly warm temps. Quote Link to comment
mainer311 Posted April 3, 2018 Report Share Posted April 3, 2018 So your saying the hose that goes to the crank case just route it down below the truck? No, you want to keep the crankcase and valve cover hoses where they are, and remove the hose from the air filter housing. You still need to vent the upper and lower chambers, but you can do so by dumping the pressure to atmosphere down below the truck instead of back into the carb(s). EDIT: I just noticed your location. Bakersfield, CA? If so, I'd be hesitant to mess with anything CARB related. Commiefornia isn't very car friendly. Quote Link to comment
datzenmike Posted April 3, 2018 Report Share Posted April 3, 2018 Only cure for excessive blow-by is rebuilding it. There is no quick cure and dumping that shit out into the air is just wrong. You will get noticed and pulled off the road. 1 Quote Link to comment
Charlie69 Posted April 4, 2018 Report Share Posted April 4, 2018 A bullet will stop blow by. Quote Link to comment
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