RICH IDLE? The most COMMON Carburetor issue that often ISN’T Carburetor related.

i got an invitation to an old friend of mine shop today he said he had something in his garage he felt i might like and he needed a little bit of help with well well well i've known this guy for a long time he's watched my kids grow up and we've raced together for years mr mike scarborough out of newark ohio mike is a very dear friend of mine i've known him for years and years we've drag raced together we've slot car raced together we've raced rc cars together and mike is working on this nova for a customer of his this is a 1970 nova with a 427 big block chevy and a 700 r4 transmission street car in every sense of the word the car is gorgeous and it reminds me so much of my car before the kids were ever born my car used to look exactly like this it was all black [Music] i've done a few things for mike over the years rebuilding carburetors and helping him tune things and this car has a little bit of an issue idling rich [Music] but it has very good thrall response it sounds good it runs really good but it'll burn your eyes to sit there and listen to it idle so the first thing i did was check the float levels which looked a-okay [Music] fired up scarborough let me see what you're dealing with [Music] it's hard to beat a big block civic breathing through three-inch flowmasters god this thing sounds good and it sounds so much like my car back in the day which i think is why mr mike's gargoyle calls me over he knows i'm down a little bit there's nothing better for me than some screwdrivers and a timing light to get me in a good mood [Music] so when i went over to see mike today um he fired that nova and it sounds really good he says it runs really good the roads were wet today it was raining so couldn't take it out for a test drive but i can tell just by throttle response and when you put it in gear it doesn't try and die or anything like that it's a really pretty decent combination it's a 373 rear end gear 700 r4 with a 10 inch 3000 stall somewhat in that area uh you know the car the cars it's it runs really good there's no question but it has one of the most common most common issues for someone with a fairly radical camshaft and a street car with a carburetor they tend to idle a little bit rich they sound really good maybe but you can just smell it it just burns your eyes it stinks it's really usually not so much the carburetor's fault it's usually ignition timing related which is what i explained to mike so the only thing i think that you could improve on is really the distributor still has the mechanical advance build in it so when you set the initial timing at 36 and you rev it up the mechanical advance is still in there and it's evidently got a 15 degree bushing in it because it jumps 15 degrees so when you go from 36 well it's not actually it's 10 degrees because it jumps from 36 to 45. so on pump gas at 45 degrees that's probably too much timing if it's got the compression that you said it does if it's got a dome piston well you can because if you turn the initial down past see honestly uh in my opinion it's probably going to need about 40 to 42 degrees initial okay and that would clean up some of the stinking that you're smelling because i've leaned the carburetor out as far as i can lean it out without it stumbling okay but it really needs to have a little bit more initial advance for to burn the fuel at idle the way it needs to so if you set the ignition timing at say 42 degrees right now then you're going to have 52 degrees total once the mechanical comes in so what i would do is pull the distributor out of it and lock the ignition timing out in the distributor so whatever you set it at initial is all it has and it doesn't come up anymore but other than that i think it's in pretty good shape it sounds really good good looking car good looking car wow so when i walked in down there i really had no idea what michael was calling me down there for so i wasn't really prepared to do an impromptu video on tuning a carburetor on a car i was mostly concerned with catching up with mike and sean uh sean allen who i've also known for a long time i've known both those guys usually if there's a situation where you see mike scarborough out screwing around someplace you're going to see sean allen and the three of us have been really good friends for a long time but anyway so when i went over there today i wasn't really expecting to do a carburetor tuning video but after seeing the car you know i was videoing as i walked through the door i didn't know what i was going to see he just said he had something for me and he was acting kind of ornery about us so i had my phone out i was recording just to see what the heck he has planned and i'm glad i did but that leads me to the video i'm going to do tonight now you know i know a lot of you have been asking for tech videos carburetor videos and this is a good one because it's a very common problem uh with i would say mild to hot street cars with carbureted engines that especially small block chevy's because the small block chevy the camcore is so small in them to get to get the engines to run halfway decent the cam profiles get pretty aggressive compared to an ls and what i mean by that is the cam lobe the ramp on the cam lobes have to be pretty aggressive and even with a big block chevy it's kind of the same way but uh anytime you've got a fairly aggressive camshaft what you would consider a mild race camshaft or a high performance camshaft that won't idle below let's say it just doesn't seem to want to idle very well below 900 rpm anytime you've got a camshaft and an engine combination that won't idle below 900 rpm there's a pretty good chance that the engine would run better with more initial timing now you know there's vacuum advance there's mechanical advance and your initial advance and a lot of people get confused on what all those things mean but for this video we're going to concentrate strictly on just a locked out distributor which is really what that car needs and the reason it needs the ignition timing locked out or what i would say locked out there's there's a lot of different ways to do it but in this example that car didn't have a vacuum advance pod so that's out okay so there's no vacuum advance to hook up or use um so what you would do is take the distributor part and i've shown that in some of my older videos i think taking an msd distributor part and locking the timing out if if you need to see that i'm sure if you search on here someone's got a video on there showing exactly uh how to do it but anyway when you've got a camshaft it won't idle below 900 rpm in a combination it needs a little bit more initial advance for the engine to burn the air fuel mixture completely at idle so like a stock engine may only need 15 or 20 degrees they idle really clean they don't need a lot of ignition advance but when you've got a fairly radical camshaft like what's in the 55 chevy in a small cubic inch engine uh you need to run considerably more initial advance and that's why the race cars they generally lock the timing out and whatever the initial is is basically where the ignition timing stays throughout the rpm range but when you've got a big camshaft like that lots of air and lots of fuel lots of reversion due to the cam profile you tend to need a lot of ignition timing to burn that air fuel mixture completely at idle now what you can do is you can go ahead and turn the idle mixture screws in uh generally you they start at about a turn and a half out from fully closed and fully closed means this the idle mixture screws are turned all the way in until they stop and from that point you turn the idle mixture screws out a turn and a half and that's your initial starting point on a holley carburetor uh or a holley style carburetor i should say um and then you can lean the idle mixture screws out from there now usually you can use a vacuum gauge if you want to use a vacuum gauge and you can watch the vacuum reading and you turn the idle mixture screws all in the same amount and you can watch the vacuum reading increase or decrease and you want to turn them in until the idle increases and the vacuum increases to the highest point and that's usually where the engine is going to idle the best and it'll smell the cleanest out the exhaust now uh on the primary side of the carburetor a lot of times you might have to run the idle mixture screws out a quarter or half a turn from perfect and make it run just a little bit rich to overcome a lean condition from transition from idle to part throttle and that's pretty common especially on a race car or something with a pretty nasty cam but if you're good at tuning carburetors and accelerator pump cams and squirters and things of that nature you can you can tune around that you won't have to have it stinking and rich but the main thing that everybody needs to pay attention to right off the bat is to make sure that the car has enough initial ignition timing to burn the air fuel mixture completely to begin with because you can't tune a carburetor to burn clean when you're not giving it when you're not giving the engine enough initial advance to begin with so that's one thing that i see a lot of dead giveaways when you pull the air filter off and the top of the carburetor is all black city looking that's a real good indication that it's not got enough ignition timing and that's how that nova was today the top of the carburetor was kind of black i checked the you know of course i checked the float levels that's a clear indicator if the float levels are way too high that's a clear indicator that it's going to idle rich regardless of how much timing's in it but the float levels looked really good so we moved from float levels to turning all four idle mixture screws in all the way and counting how many turns out they were and they were all exactly 1.5 turns from completely shut completely closed so that wasn't an issue so i got the timing light out and that's when i found out that it only had 36 degrees initial advance which is in my opinion would be bare minimum 36 degrees on a 427 big block or 355 you know with a a fairly hot camshaft in it like what that car had 30 36 degrees is like your bare minimum especially on a pump gas engine um so you know unfortunately that car still had the mechanical advance in it and i explained to mike if you remove the mechanical advance lock it out set the timing at 42 degrees it'll idle cleaner it may start a little harder you may have to use a start on it but it'll run much better or have much better throttle response [Music] and it won't burn your eyes sitting there idling so anyway guys i wasn't really prepared to do a carburetor tech video today and this is kind of all over the place and maybe i'm not doing it justice uh the way i'm doing it but the most common carburetor problem that's never a carburetor problem is not enough initial advance so if you've got a car at home that uh is a pump gas street car and it's got a little bit too much of a camshaft in it or kind of a wild cam shaft and it sounds really good but it stinks and you're embarrassed you pull into the the cruise in night or your car shows or whatever and the thing stinks and everybody's like you know a lot of times uh pump gas engines uh with a radical camshaft in them a lot of times they'll smell really rich and they'll smoke blue and it'll almost look like oil smoke but in reality it's sometimes it's just not burning all the air fuel mixture that's getting into the combustion chamber due to all the reversion in the intake manifold and so running a little bit more initial advance than maybe what you'd think it would need or maybe what you're running now will help cure that but it it can also cause hard starting problems so that's why if it's a street car sometimes i'll i'll tell people to go ahead and run the vacuum advance and hook the vacuum advance port or the vacuum advance pod to the vacuum port on the carburetor that has vacuum at idle and what that does is it will allow the engine to start with say eight degrees less timing let's say the the vacuum advance canister adds eight degrees of advance under vacuum so when you go to turn the car over and there's no vacuum at low rpm it's turning over the car will start once the vacuum builds the vacuum advance pod pulls the timing up and that increases your uh your initial timing at idle and of course it will back off as you give it gas and that's when you would want to have your mechanical weights take over and start to bring the ignition advance in but if you've got something fairly wild like the 55 chevy here uh it's got a hydraulic roller camshaft and it's really it's really kind of too big for it it's it's it's pretty nasty it's not it's not very nice to drive it's kind of a pain but if you've got something that's fairly radical uh 240 degrees at 50 uh duration and bigger in a small block chevy um you're probably going to need at least a minimum of 36 degrees initial advance for the car to run properly and idle properly and clean now on the camshaft situation you know you take a let's say you've got a 236 duration at 50 520 lift hydraulic roller well if you take that camshaft uh ground on say a 106 center line and you put that in a 283 it's gonna sound pretty radical okay because the cubic inch is small but if you take that same camshaft and put it in 400 you won't even hardly be able to hear it so everything's relative to cubic inch and duration okay the more duration and the less cubic inch the more radical the camshafts gonna sound and the opposite is true as well so uh today was fun i really enjoyed catching up with my buddies and i really appreciate them thinking how many of those those two have watched my boys grow up from the day they were born until today i mean they've they know pretty much everything that those kids have ever done and and uh you know they love and they care about our family because they're they're old friends i've known them before we had a youtube channel i've known them before i had a pot to piss in or a window to throw it out of so i greatly appreciate those guys thinking of me today knowing that things are rough around here uh with the kids and things that are going on and they just kind of wanted to get me out of the house and give me something to do and they both know how much i enjoy tuning carbureted engines and um i'm sure mike could have done that on his own he just he just wanted to get me over there today so thank you mike sean greatly appreciate you guys thank you for your friendship uh this lifestyle and this culture is more than just cars it's more than just racing it's more than uh everything that you the sum of everything that you see in these videos it's also about friendship and family and i don't know if you guys watched i'm sure you probably did billy's video when sean ellington uh gave billy the headers off the the og murder nova if you watch that video uh at the kind of at the beginning of the video when billy gets the headers from shawn shawn talks a little bit about family and it was probably the most inspirational thing i think i've ever heard anybody from that television show say and to have him say it to me and billy in person and tell us that they watch the videos and like they keep up with it i'm like sean said we're going to come out watch you guys race sometime i'm like watch us race what the hell would you why would you care about watching us race but the reality is uh there's a lot of different youtube channels uh that in my opinion probably put out a little bit better content than than ours uh the video equipment is better maybe the editing sometimes is better and the music is better and just you know uh i'm not gonna name any names but there's a lot of them out there that put out a really really high quality racing footage content and for whatever reason uh their channels haven't taken off as well as my kids and and in some cases even mine and i've told billy in the past you know part of the reason i started my channel was because i wanted to show the family aspect the personal aspect of it because that's what um people will connect with i mean anybody can watch racing videos on any channel on youtube and they're they're all the same content the same car is making the same passes at the same place you know there'll be four or five youtube channels that dig or die video and making videos but uh what sets ours apart i think is the family aspect of it and i try to show the good and the bad sometimes i get in trouble with my family for showing some of the things that i feel are important but a lot of people connect with it because they go through the same things and it's like a lot of the youtube channels that are very popular uh are i wouldn't say fake i'm not trying to say anything like that but like they don't show the hard times too uh it's not all glamour and glitz and fun times and it's not like that there's a lot of struggle there's a lot of sacrifice there's a lot of problems day to day and uh i think that's what sets us apart a little bit that people connect with us for some reason i think it's just because we show the family aspect of it and i don't know maybe i'm wrong i'm gonna hop off here i feel like i'm rambling that's gonna be my video for today thank you all for watching liking sharing subscribing the whole thing comments good and bad so it's whatever talk to y'all later good night

Channel: The Old Man’s Garage

Views: 374,799

Keywords: Holley Carburetor, Rich idle, Big Block, Small Block, Chevy, Ford, Mopar, Roller cam

Id: 7eA9zwuxt84

Length: 21min 41sec (1301 seconds)

Published: Sun Dec 19 2021