seuadr 488 #1 Posted April 14, 2021 Hey all, now that my motor is swapped and running, i have been working my way through shoring up other issues that were either created by the swap or existed before and i ignored (like no gauge lights!) next up on the block is the vacuum gauge - i didn't have a spot to hook this up on the replacement engine, (except that i have an electric fuel pump so i guess i could hook it up to the pulse pump port?) so i left it unhooked. but now i'm wondering - does this tell me anything that i need to know? am i missing out on some useful function of the vac gauge? "100% work" doesn't mean much to me, unless i need to know that for some kind of future troubleshooting... what is your opinion? Share this post Link to post Share on other sites
Achto 27,576 #2 Posted April 14, 2021 (edited) Personally I really never saw a big value in the vacuum / power gauge. I was always taught that there are only 2 gauges that really matter on an engine. Oil pressure and water temperature. All other gauges are only there for convenience. Edited April 14, 2021 by Achto 2 Share this post Link to post Share on other sites
seuadr 488 #3 Posted April 14, 2021 12 minutes ago, Achto said: Personally I really never saw a big value in the vacuum / power gauge. I was always taught that there are only 2 gauges that really matter on an engine. Oil pressure and water temperature. All other gauges are only there for convenience. good point - though, gas gauge is pretty nice 1 Share this post Link to post Share on other sites
squonk 41,118 #4 Posted April 14, 2021 (edited) 19 minutes ago, Achto said: Personally I really never saw a big value in the vacuum / power gauge. I was always taught that there are only 2 gauges that really matter on an engine. Oil pressure and water temperature. All other gauges are only there for convenience. Not so!! I remember riding in my Uncle's 65 Impala SS with the big honkin vacuum gauge on the dash. I could have watched that thing all day! In all seriousness , the Toro gauge may not be the most useful one , but I diagnosed many an 8 cylinder engine with a hand held vacuum gauge. " late timing, sticky valves,bad cams ect. Still in the tool box! Edited April 14, 2021 by squonk 2 2 Share this post Link to post Share on other sites
johnnymag3 2,520 #5 Posted April 14, 2021 A Vacuum gauge is a very good diagnostic tool. if you know how to use it !!! A nice gauge to have in my opinion. John 1 Share this post Link to post Share on other sites
seuadr 488 #6 Posted April 14, 2021 8 minutes ago, johnnymag3 said: A Vacuum gauge is a very good diagnostic tool. if you know how to use it !!! A nice gauge to have in my opinion. John alright - so what can i diagnose, and how? Share this post Link to post Share on other sites
lynnmor 7,306 #7 Posted April 14, 2021 4 minutes ago, seuadr said: alright - so what can i diagnose, and how? About the only use would be setting the idle mixture, but doing it by ear works OK. I see my gauge at or near 100% most of the time that the engine is working fairly hard, like mowing. I believe it is most useful as a conversation piece, and it should work if one has a bit of OCD. If there is a boss cast in the intake, drill and tap it for a 1/8-27 pipe thread. Share this post Link to post Share on other sites
seuadr 488 #8 Posted April 14, 2021 1 minute ago, lynnmor said: , drill and tap it for a 1/8-27 pipe thread. so as luck would have it, it already has a connection sticking out of the block for the fuel pump. Doesn't have barbs, but the hose did fit snug so i am sure with a pipe clamp it would be OK. but i'd have to take all the tins off to hook it back up and i'm not sure i actually care, unless it is going to tell me something useful Share this post Link to post Share on other sites
lynnmor 7,306 #9 Posted April 14, 2021 Just now, seuadr said: so as luck would have it, it already has a connection sticking out of the block for the fuel pump. Doesn't have barbs, but the hose did fit snug so i am sure with a pipe clamp it would be OK. but i'd have to take all the tins off to hook it back up and i'm not sure i actually care, unless it is going to tell me something useful That is probably a crankcase pulse connection and won't work correctly. 1 1 Share this post Link to post Share on other sites
seuadr 488 #10 Posted April 14, 2021 1 minute ago, lynnmor said: That is probably a crankcase pulse connection and won't work correctly. you are correct - i didn't read your post correctly. there is NOT a boss nor a connection in the intake of the replacement motor (there was on the original, of course.) Share this post Link to post Share on other sites
squonk 41,118 #11 Posted April 14, 2021 Yes. Setting idle mixture you would want to obtain the highest reading with no flutter or hunting back and forth. Flutter/ bouncing would indicate a valve not sealing good for example. Hunting up and down- lean mixture. Low reading late timing 3 2 Share this post Link to post Share on other sites
johnnymag3 2,520 #12 Posted April 14, 2021 What Squonk said ….!!!!! Those are things you can do...us old timers remember them well !!! ……...well me anyway..... 3 Share this post Link to post Share on other sites
DougC 2,641 #13 Posted April 14, 2021 Yep when the time comes the vac. gauge starts fluttering wildly you know your running on borrowed hours......... 3 Share this post Link to post Share on other sites
johnnymag3 2,520 #14 Posted April 14, 2021 Gotta teach the young ones a thing or two............... If you learn something everyday....your still living !!!!! 3 Share this post Link to post Share on other sites
squonk 41,118 #15 Posted April 15, 2021 Ol' Reliable. Had to get it out of the toolbox just to look at it again in all it's glory! 4 1 1 Share this post Link to post Share on other sites
Handy Don 12,232 #16 Posted April 15, 2021 (edited) My spouse's Subaru Impreza (2013) has an "economy" gauge, which is a vacuum gauge in disguise. It gives a visual to let you know that when the engine is pulling harder you are using more fuel. Edited April 15, 2021 by Handy Don 1 Share this post Link to post Share on other sites
johnnymag3 2,520 #17 Posted April 15, 2021 6 hours ago, Handy Don said: My spouse's Subaru Impreza (2013) has an "economy" gauge, which is a vacuum gauge in disguise. It gives a visual to let you know that when the engine is pulling harder you are using more fuel. Simple word for todays people.......Something they can understand.... Share this post Link to post Share on other sites