I can't seem to get the 78 Sedan tuned enough to not smell like it's burning a lot of gas, but still idle low enough without the engine shaking like crazy.
Is it normal to hear the sound of a vacuum "leak" coming from the carb barrel?
Hello dave1987,
Have you done a compression check???
YES! you should hear a high-pitched noise while the engine is at idle especially if the it is running fast while the butterflys on the carb are closed.
I suspect a bad cam or siezed rings or blown head gasket.
I have NEW 2.3 cams you just pay 20.00 for the shipping.
I have 80+ new 2.3 cams and they NEED to go!!!!
From Pintony
Greetings,
It sounds like you have adjusted the Carb to a rich mixture to compensate for a lean condition. And then had to adjust idle speed to stop the engine from shaking.
First, make sure that you have no visually obvious vacuum leaks( hoses unhooked, Missing EGR screws, loose carb flange nuts, etc) , then get the engine speed down to correct RPM for idle, slowly lean out the mixture, recheck idle RPM. If it won't hold a smooth idle, then get the closest correct idle speed. Now shut off the motor, find a intake manifold vacuum port between the carb base and the cylinder head (use a T fitting to splice in to a hose if necessary) and attach a Vacuum gauge. Restart the motor, check the Vacuum gauge reading at idle. It should read a steady 15 to 17 inches (or HG ) on the gauge dial. If the needle is wildly swinging high and low, you have a vacuum leak , very poorly adjusted or worn-out carb, or a mechanical issue ( blown head gasket, stuck lifter, bad cam, burned valves or worse). Each of these has a testing procedure or inspection process.
Always start with the tuning, unless you know about the existence of a mechanical problem first. Look now , spend money later..
Good Hunting..
Pintosopher
I am highly doubting it is the cam as i have a less than 2 year old cam in there which has less than 8k miles on it.
My cousin rebuilt the entire engine with me. I am not thinking he did to much wrong seeing as he has build racing engines and raced cars for 30+ years. However, sometimes people miss things.
I will try a basic tune again.
yeah... I build racing engines for over 20 years.. completing one a week over 5 years...I still f*<k thing up once in a while....the cam is one of the easiest things to screw up in a rebuild honestly....
Spongbobpintoheead
If the motor has a rectangular module hanging off of the manifold just under the carb, that might be where the intake leak is. It is a backfire valve and if the motor has ever in its life backfired, it has burned the diaphram in that module and will cause a major vacuum leak. I had a 76 wagon that was famous for that problem. I just pulled it off and sealed the hole with a plug. The thing ran like a top after that. That is just a thought as the Pinto's with all of the smog crap thru the late 70's were bad as far as vacuum leaks. Hope that will help!
Is this the backfire valve you are talking about?
http://429mustangcougarinfo.50megs.com/canister12.jpg
I've seen it called a thermactor valve before, and it goes in line between my carb base and my air pump. It is located on the left side of my engine above the exhaust manifold.
I pulled the carb off last night and took it apart entirely, cleaned it all out really well, tightened down screws, and reset my float setting.
The baseplate for the carb comes apart into two pieces, where the crank case vent EGR valve output goes into the base of the carb. I split the two piece base by removing the two allen screws and used carb cleaner to clean it out, but it wasn't cutting it so I used brake cleaner which did a bit better. It was so caked with oil and grease and fuel that it was difficult to clean it even with a screw driver! I let to soak in gas for about 30 minutes which softened it up a good deal, enough for me to clean it out and allow more flow through it.
The car is running much better now, but I still have that concern that it may come back up at any time.
Still smells like gas though...
Dave,
I might have confused you with the term backfire valve. The tecnical term is called a deceleration valve and it is located just under the carb attached directly to the manifold. It will have vacuum line attached to it. There is a diaphram in that unit that will burn out if the engine backfires. I have attached a picture to give you a better idea of what it will look like. Sorry for any confusion!
Thank you for the picture. After seeing that it reminded me that I saw it once before in one of my shop manuals. I went through my Clymer manual and sure enough, it shows exactly where it would be bolted in.
I do not have a decel valve on my intake or anywhere else. I have a plug in place of it's mounting position.
A few months ago I was having trouble tuning the car and was looking into blocking off the EGR mounting port, skip the EGR vacuum and go straight to the choke vacuum. Would this make a difference in the performance of the car at all as far as tuning goes?
If I go and remove the EGR valve, do I need to remove the entire pipe that is connected to the block on the other side of the engine as well?
Why are EGR valves so expensive? I'm looking at $90+ for a replacment!
If the engine doesn't have to go thru a smog test, I would just replace the EGR gasket with a metal plate and just block it off. You won't need to remove anything else and just block off the vacuum line going to it. I know that the California models had all kinds of vacuum lines and thermo switches that could always cause vacuum problems. If you never have to smog test the car, I would just eliminate as much of the garbage as I can. That would really make tuning alot easier
Right now I've plugged the vacuum port on the EGR valve as well as at the T connection on the vacuum line that continues up to the choke vacuum valve. It seems to have eliminated my idling issue!
I popped the carb off the car again since I didn't do any adjustments to it when I rebuilt it, due to the rebuild happening on a day that I had to put it back together quickly after replacing everything since I had some unexpected emergencies come up that day.
The float drop setting was off by about 1/4 inch. The setting when the float bowl is full was only off by a very small fraction of an inch. Everything else was okay though. How does the float drop setting effect the operation of the engine/carb?
How ironic. I think I have found my issue with a lot of stuff, like failing to pass emissions last year.
I have had the distributor hooked up to the manifold vacuum all along!
Emissions testing is due this month again, wish me luck!
Quote from: dave1987 on October 14, 2009, 07:04:52 PM
Emissions testing is due this month again, wish me luck!
Good luck!
:afro: