In this month’s Hot Rod to the Rescue column, the problem car, an older Chevelle, ever since a new 350-something crate engine was installed, it runs poorly. Idles badly, and the engine rpms (and vehicle speed) drift up and down during freeway driving. Several shops had a go at it, but none of them could get it to run well. So the magazine sends the car to an expert of their liking, who determines among other things the carb’s choke isn’t working at all, stuck on, and even if it were working, the choke fast idle cam settings are all wrong. Add to that the ignition timing has way too much advance, as much as 70 degrees. I’m just curious how it could happen than prior multiple shops wouldn’t be able to figure those two problems? I’m not saying they should be able to figure all the problems, but those two should be pretty easy to figure out. What gives? Is it just that modern day techs have no experience on 60/70’s designs carbureted cars these days?
It could very well be that there wasn’t a mechanic familiar with pre 1980 vehicles in any of the shops. Young “technicians” today are trained to begin driveability diagnosis by determining trouble codes.It’s amazing how few young mechanics have any insight into the basics of internal combustion engine operation.
The car must not have seen much highway use. With 70 degrees of total advance an engine would be wiped out fairly quickly.
It must have been a real bear to crank over.
Part of the advance problem apparently was the vacuum advance was connected to the intake manifold rather than a ported vacuum source, and …this is sort of hard to believe a shop would miss … the vacuum advance hose was clogged. There was a screw left in it from a prior test or something. It would leak enough to allow the vacuum to the advance port on the distributor to slowly build up and stay there.
When you buy a stock car, the engine fuel system, exhaust, camshaft and timing are all designed to work with the weight, gearing, torque converter of the vehicle.
When a hot rodder buys a crate 350 and puts in who knows what, then picks an intake manifold ,cam, header and carb from various suppliers, nothing has been designed to work together.
Mechanics are used to restoring cars to like new stock to get them running right, they are not race car designers for the most part and shouldn’t be expected to be.
It is fairly straightforward to rebuild a carb to stock, but if the carb is sized wrong for the engine and parts inside it have been changed in an effort to crutch the problem and it doesn’t work so you take it to another shop, how on earth is the new mechanic supposed to start.
The shop that Hot Rod took it too is a full service hot rod and race engine shop with vast experience and diagnostic equipment. They are more race engineers than mechanics and if you took your ordinary car in to them for anything, you would not ne happy with the bill.
You are right.
With timing advanced 70 degrees, I see no way that the engine would start.
Unfortunately I haven’t read the entire article, but I’m guessing it’s not at 70 degrees advance during start up. That would be a big problem.
I’m inclined to agree with this. But I’ll go further.
Not only don’t kids today know pre-1990s fuel metering systems, many don’t understand the physics behind how cars work. They not only don’t know how to fix a carburetor, they don’t even understand how one works. They can’t recognize the difference between fuel metering by the carb and fuel metering by sending “engine demand” signals from sensors through an algorithm in a microchip. They know fuel needs to be metered, but they don’t actually understand why or how it’s done. They know fuel injection is better because some teacher said so, but they don’t really understand why.
Automotive technology programs are tasked with taking what they’re given and making graduates capable of passing ASE exams (at best). I truly believe that if our primary educational system were doing its job and teaching basic science, and our secondary educational system were doing its job and teaching physics, their way of looking at what they’re taught in the automotive programs would be much different, and the knowledge they come out with would be far deeper.
Perhaps it’s because I spent 17 years working with the graduates of our primary and secondary educational systems, combined with the fact that I love analysis, that I have this opinion. But when I see high school graduates applying for college that need two years of remediation before they can even begin their freshman classes, and see HS graduates that can barely write an articulate sentence, I worry about the future of my grandchildren.
I also spent 17 years watching my college focus on “asses in the classes” more intensely than the education itself. That’s why you see so many totally useless course being offered. They’re cheaper to run and the kids like them because they’re easy, so they’re profitable for the college. You can put 30+ students in the classroom and hire a mid-level adjunct… and make beaucoup profit.
Sorry about the rant, but I truly believe that’s why there are so many “mechanics” out there that can’t solve problems unless they’ve been shown exactly how. They don’t understand d the basics.
I should add that I’ve also worked with a great many truly smart students that truly desire to learn the why and how behind the what. But primary and secondary systems today don’t require knowledge to graduate. Many make it available, but few require it.
You make a lot of excellent points.
But there are very few pre-1990 cars on the road.
It’s probably because so many people do not take care of their cars.
Today’s cars are so much more reliable.
I do not miss points and condensers and having to grease wheel bearings.
Struts last much longer than shocks too.
Take it to a lawn mower guy. They still have carbs-most of them anyway.
Regarding the 70 degrees of timing, I also referred to it as total advance. That would be at very high RPMs. Static timing would be far less. That’s also why I said cranking it must have been a bear. Odds are it was kicking back horribly and spitting back out the carburetor.
Back in the late 80s when I worked for VW/Subaru a gentleman brought in a Westfalia camper for a 30k miles service as he was about to take off on a long trip in a few weeks. The mechanic who was assigned the job was a very good one.
At the end he used the new from VW electronic tool which had as one of its features a digital readout for the ignition timing.
He drove it around town for a few weeks with no issues. Off he goes on the open road. Less than a 100 miles later the engine blew up. This of course was immediately blamed on the mechanic and which I knew just could not be.
When examined it was determined the Bus had 30 degrees of static timing in it which was way above what was recommended.
Mechanic’s fault? Nope. We found out that the new from VW tool was faulty; much to the chagrin of the VW factory rep who had insisted all along it was mechanic error.
With 30 degrees static this meant it probably had around 60 total advance.
The engine would always fire right up without balking even at 30 degrees static.
That’s very true. But IMHO a good mechanic should be able to get one running.
I have to acknowledge, however, that this being a “crate engine” with a carb it’s likely a new long block (block & heads) with the old carb system installed on it. That can take a bit more knowledge, as the carb has to be right for the engine. The first two guys probably didn’t even want to fool with it because of this.
Having said all that, the causes that the well-experienced mechanic found were pretty basic causes that any mechanic should have been able to solve.
With the choke stuck in near closed position the exhaust would be getting dark and the over rich smell would be obvious. If the base timing was more than a few degrees high the starter would be laboring to crank the engine on a hot start and that condition would also be obvious.
When diagnosing an obviously poor running engine back in the good ole days it was standard procedure to remove the breather to inspect the carburetor and get access to the throttle. Did any of the mechanics who failed to diagnose this car move the breather?
When I read ‘This works and this doesn’t work’ in school I wanted to know why. Currently students are taught how to pass the tests.
Never take a modified project to a normal mechanic unless you know he knows what he’s doing. Take it to a speed shop.
Had a friend take his car in to his regular mechanic to get a supercharger installed on a Honda. Guy got it installed, but obviously didn’t know what he was doing. Car ran like crap, stalled at stoplights, etc. A bunch of us got together to thrash on his car and… Hey, what’s this? A golf tee in a vacuum line. It was painted black so we didn’t even see it at first.
Guy obviously ran out of places where he knew vac lines went, and just plugged it up. Doesn’t work. We plumbed it correctly and he ended up with a Honda that could run with Corvettes.
It’s kinda like… You’re not gonna have your cardiologist do brain surgery on you. The regular mechanic is an expert at repairing cars. Your speed shop mechanic is an expert at modifying cars.
Of course they don’t have that experience, much like a mechanic who knows a 72 Chevelle inside and out wouldn’t have much of an idea of how to deal with a variable valve timing or fuel pump control module like we see today. Cars today aren’t serviced or repaired with timing lights and by visually inspecting things. It’s an entirely different methodology. There are 6 mechanics at the shop where I work. Only 2 of us have a timing light.
I’m the shop manager of an auto shop with 5 other mechanics. I’ve put in place some “policies” to try to keep the work flow going well. One of them is that if a car is not running well, you are to drive the car to duplicate the complaint with a scan tool hooked up to get a direction to go in. You are not to even open the hood until you can tell me whether the concern is ignition, fuel, or mechanical related and what the next step will be. Expecting a general repair shop to be able to resolve a carburetor and distributor issue these days is unrealistic, not because of the quality of the technicians but because it’s not part of fixing cars these days. It’s become a specialty.
Yours is an interesting perspective, but I’m still uncomfortable with kids coming out of automotive technology programs being unable to figure out problems as simple as the one described in the post.
Your chosen policy is exactly that; a choice. You’ve chosen to service only modern vehicles. If the work coming to you is sufficient to allow you to do that, I can see where it makes more sense than tying up the bays with old vehicles the cost to repair of which will exceed the value of the vehicle… and the drivers of which may not be able to afford the repair of. You could easily turn into a used car lot that way, filled with cars your acquired from cash-strapped owners.
But the bulk of the country is rural. In rural areas I would expect any mechanic with an ASE patch on his sleeve to be able to diagnose and repair crab problems as basic as those described.
From the perspective of running a business in an area where the volume is sufficient to support market segment targeting, I understand where you’re coming from.
From an educational perspective, that weakness dismays me.
A young mechanic just beginning his career will never see these problems, or if he does he’ll be wise to turn them away. Six of us working in this shop, only 2 would tackle that problem. One grudgingly if there’s nothing else to do, the other (me) has all the tools and experience to overhaul and “dial in” a computer controlled carburetor. But I might have a carb-related repair once every 2 months.
I don’t know that I’d characterize that as a weakness. Maybe as a limitation based on how much one guy is expected to know or do. One of my guys, the Euro specialist, could probably write a book on the diagnosis and repair of engine performance problems on Audi 5-valve turbo engines or fuel supply issues with Volvo fuel pump control modules. But having all that knowledge and experience means there’s not much room left for understanding a system in which when the spark plug fires is controlled by a rubber hose, a carburetor, and a vacuum diaphragm in the distributor, especially in a day and age when the typical car has neither a carb nor a distributor. He has a crystal clear idea of what effect fuel mixture and ignition timing has on an engine, yet not the slightest idea of why you would try to accomplish those things with a carb and distributor when there are so much more reliable and efficient ways to do it.
I don’t see the point in having the instructor teach the kids how to master carbs . . . and then they may never see, let alone work on, one when they graduate from the program and get jobs in the real world
As far as “the fundamentals” go . . . I would say that the carburetor is no longer one of them, and hasn’t been for quite some time. It’s been a generation since the last vehicles equipped with carburetors left any assembly line in the USA
I see a few older Corollas driving around, which MIGHT have carburetors. Bear in mind I"m in Los Angeles. Anywhere else except the southwest, those cars are probably rusted out and sitting in the junkyard, and maybe they’ve already been crushed a long time ago.