tired of carb problems - new motor?

[bmartin9122]

Hey guys,

I am really tired tired of my 79's fuel system problems. I say fuel system and/or ignition problems, because I keep getting an intermittent misfire.

The motor is basically stock with 120,000 miles. The truck has a new carb, rotor, cap, and wires.

I was thinking I could either convert the old motor to EFI via some kind of kit, or I could replace the motor altogether and get one that is already set-up for FI and electronic ignition. I understand the concepts but I don't have any experience in this kind of work, and I would enlist the help of a trusted shop to do the installation.

Any ideas or opinions?

I apologize in advance if this is an old subject.

[Srubydo1986]

well i dont the the engine is the problem. but i cant think what it might be as of know

[bmartin9122]

Originally Posted by Srubydo1986

well i dont the the engine is the problem. but i cant think what it might be as of know

Actually, I agree, but I don't know what to do. I keep thinking that if I can get rid of the carb, then my truck will be alot less trouble to live with. Is there a FI kit available?

[streetstar]

Holley sells a pro-jection kit for about a grand. It is not designed for high hp applications though.

As well, retrofitting a TBI system from a salvage motor should not be too bad.

If i personally had the resources and was building a driver, i would look for a complete motor and tranny from a late model (a z28 LT-1 or LS-1 would be great, but a 5.3 or 6.0 truck motor would be nice too)
Many people have adapted these over the years -- i'm not sure what it takes, only that it has been done

[bmartin9122]

Originally Posted by streetstar

Holley sells a pro-jection kit for about a grand. It is not designed for high hp applications though.

As well, retrofitting a TBI system from a salvage motor should not be too bad.

If i personally had the resources and was building a driver, i would look for a complete motor and tranny from a late model (a z28 LT-1 or LS-1 would be great, but a 5.3 or 6.0 truck motor would be nice too)
Many people have adapted these over the years -- i'm not sure what it takes, only that it has been done

I'm really looking for a reliable system - not big power. The Holley set-up might be the ticket.

Also, what about the MSD ignition system I keep seeing? Is it a replacement for the HEI system? I'm not so sure the ignition system isn't to blame.

[xtreme80]

I see no need in converting to EFI. I can almost guarantee you that this problem is ignition related, and has nothing to do with having a carb on it. I also think that once you learn about the carb and how it works, you'll come to like it just as much as a TBI setup.

For your misfire, does it feel like the whole motor cuts out for a sec, then runs fine, or is it actually a specific cylinder that's cutting out intermittently?

If it's the whole motor cutting out like that, check your wiring to the distributor, loose connections, wires shorting out, check to make sure you have the ground strap in the new cap since you've replaced it.

If it's just a specific cylinder cutting out intermittently, check all plug wires to make sure they have a strong connection with the plugs and cap. Make sure none are burnt, too close to the exhaust, etc. Pull the plugs and check for oil deposits on them, check plug gap, corrosion, etc. If you've got a cheap cap on there (autozone, CSK, etc) then replace it with a good delco or MSD cap.

If none of that does the trick, and it is obviously getting fuel, I would say it's time for a new Dizzy. They do wear out and internal components break over time.

Hope that helps man. You don't need to convert to EFI to try to solve this issue.

[Pyrotechnic]

I agree, I think you have a simple ignition problem. Is that a stock HEI with 120,000 miles on it ? If so, then it's probably time for a new one.

My experience with properly working Q-Jet is that they are almost as good as fuel injection. I could leave my truck sit for a week and come turn the key and it would start right up. I had the stovepot choke setup and it worked like a charm. Got great gas mileage too.

GM TBI is your best bet if you just don't like carbs. You won't get a better tune for a stock or slightly modded 350. Just remember GM spent lots of money and time getting these computers programmed to give the best balance for performance and gas mileage. As a bonus, any parts you need will be available at just about any parts store.

Or, if you want an even better setup, try a TPI setup. Will be a little more costly and more involved swap but it's also a very good system.

[bhunt31]

I'd run a compression check on it before I went spending all that money on an injection system.

[bmartin9122]

Originally Posted by xtreme80

I see no need in converting to EFI. I can almost guarantee you that this problem is ignition related, and has nothing to do with having a carb on it. I also think that once you learn about the carb and how it works, you'll come to like it just as much as a TBI setup.

For your misfire, does it feel like the whole motor cuts out for a sec, then runs fine, or is it actually a specific cylinder that's cutting out intermittently?

If it's the whole motor cutting out like that, check your wiring to the distributor, loose connections, wires shorting out, check to make sure you have the ground strap in the new cap since you've replaced it.

If it's just a specific cylinder cutting out intermittently, check all plug wires to make sure they have a strong connection with the plugs and cap. Make sure none are burnt, too close to the exhaust, etc. Pull the plugs and check for oil deposits on them, check plug gap, corrosion, etc. If you've got a cheap cap on there (autozone, CSK, etc) then replace it with a good delco or MSD cap.

If none of that does the trick, and it is obviously getting fuel, I would say it's time for a new Dizzy. They do wear out and internal components break over time.

Hope that helps man. You don't need to convert to EFI to try to solve this issue.

Thanks for the thoughts... It is definitely the whole motor cutting out, then it fires back up with a cough/backfire. I have isolated it down to when the motor is not completely warmed up. It idles smooth though. I did have an automatic electric choke installed about the same time this started. Maybe related?

[bmartin9122]

Originally Posted by Pyrotechnic

I agree, I think you have a simple ignition problem. Is that a stock HEI with 120,000 miles on it ? If so, then it's probably time for a new one.

My experience with properly working Q-Jet is that they are almost as good as fuel injection. I could leave my truck sit for a week and come turn the key and it would start right up. I had the stovepot choke setup and it worked like a charm. Got great gas mileage too.

GM TBI is your best bet if you just don't like carbs. You won't get a better tune for a stock or slightly modded 350. Just remember GM spent lots of money and time getting these computers programmed to give the best balance for performance and gas mileage. As a bonus, any parts you need will be available at just about any parts store.

Or, if you want an even better setup, try a TPI setup. Will be a little more costly and more involved swap but it's also a very good system.

It was my grandfather's truck for most of that mileage, but I am fairly certain the HEI system is all original. Is a replacement HEI system best, or is there a more modern (read: reliable) system out there?

[bmartin9122]

Originally Posted by bhunt31

I'd run a compression check on it before I went spending all that money on an injection system.

Definitely! I had the compression checked about a year ago, and it was even between cylinders. I wasn't surprised since the bottom unit had been worked over and upgraded about 7 years after purchased - say 1986 or so. I also had a thorough valve job done about 1.5 years ago, as well.

Hopefully, things have not gone downhill suddenly. I do know the engine uses/loses about 2 quarts of oil every 3000 miles (oil change interval). Maybe, I am fowling spark plugs rapidly.

[xtreme80]

If the plugs were fowling that bad, it would cut out per cylinder and stay out. Like I said take a look at some of the things I mentioned.

This could also be fuel related, so I would suggest getting a clear fuel filter (fram makes a cheap one, that's what I use) and hooking it up before your carb. This will tell you if you've got a constant flow of gas to the carb. When it misses like you say, get out and immediately check to make sure the carb has gas.

If it is ignition, a replacement HEI system is best. You can get a remanned dizzy for about a hundred bucks, but if you're gonna do that, just go to Jegs and get their upgraded dizzy for about 120.

http://www.jegs.com/webapp/wcs/store...0002_379706_-1

Just make sure it is ignition before you go buying new parts.

How often does it cut out? Once every morning? Is it doing it more and more?

[bmartin9122]

Originally Posted by xtreme80

If the plugs were fowling that bad, it would cut out per cylinder and stay out. Like I said take a look at some of the things I mentioned.

This could also be fuel related, so I would suggest getting a clear fuel filter (fram makes a cheap one, that's what I use) and hooking it up before your carb. This will tell you if you've got a constant flow of gas to the carb. When it misses like you say, get out and immediately check to make sure the carb has gas.

If it is ignition, a replacement HEI system is best. You can get a remanned dizzy for about a hundred bucks, but if you're gonna do that, just go to Jegs and get their upgraded dizzy for about 120.

http://www.jegs.com/webapp/wcs/store...0002_379706_-1

Just make sure it is ignition before you go buying new parts.

How often does it cut out? Once every morning? Is it doing it more and more?

I thought it might be bad gas or something, but I switched tanks with fresh fuel - same thing. I haven't noticed it increasing, and it came on kind of sudden. It startled me the first time it happened. It is not a daily driver, and I only drive it about once a week at most.

I do have an inline fuel filter near the carb, but I cannot remember off-hand if it is clear or not.

[xtreme80]

Well at least you've got somewhat of a starting point now. Check out the things I mentioned and let me know. We'll help you get this figured out!

[Vitamin GMC]

Hello, new here, Ive been experiancing cut outs on my 84 gmc and got worse as time went on, replced the distributer but not the coil.

[Vitamin GMC]

Still cutting out.

[xtreme80]

Originally Posted by Vitamin GMC

Still cutting out.

Just follow all the steps I gave to bmartin9122. It should give you a good starting point.

[bmartin9122]

Originally Posted by xtreme80

Well at least you've got somewhat of a starting point now. Check out the things I mentioned and let me know. We'll help you get this figured out!

Yup, thanks! Rep points for you!!!

[James McClure]

Hay guys, let me throw in my 2 cents here. Someone mentioned checking to see if the ground strap is still in the distributor cap. Make sure it's there. Next, if you haven't changed the distributor for a new or rebuilt unit check the "pole piece" hooked to the vac advance cannister. Make sure your home when you do this check because the truck ain't going anyplace if it's bad OK? Now, with the cap and rotor off you will see 2 wires going to it. One is white, the other green. Pull on each wire. Not real hard but a solid pull if the pole piece is bad one of those wires will break. What happens over time is the vac advance pulls back and forth on the pole piece and eventually the wires bend often enough and 1 of them will break inside the insulation. Get the wire in just the right position and the circut opens and you loose spark. If this happens out on the road disconnect the vac advance and see if the problem goes away. If it does, pull the distriubutor and replace the pole piece. I've seen this quite often in higher mileage vehicles, not just trucks and not just 8 cyl engines. Hope this helps some, jim

[bmartin9122]

Originally Posted by James McClure

Hay guys, let me throw in my 2 cents here. Someone mentioned checking to see if the ground strap is still in the distributor cap. Make sure it's there. Next, if you haven't changed the distributor for a new or rebuilt unit check the "pole piece" hooked to the vac advance cannister. Make sure your home when you do this check because the truck ain't going anyplace if it's bad OK? Now, with the cap and rotor off you will see 2 wires going to it. One is white, the other green. Pull on each wire. Not real hard but a solid pull if the pole piece is bad one of those wires will break. What happens over time is the vac advance pulls back and forth on the pole piece and eventually the wires bend often enough and 1 of them will break inside the insulation. Get the wire in just the right position and the circut opens and you loose spark. If this happens out on the road disconnect the vac advance and see if the problem goes away. If it does, pull the distriubutor and replace the pole piece. I've seen this quite often in higher mileage vehicles, not just trucks and not just 8 cyl engines. Hope this helps some, jim

Excellent! Rep for you! Thanks.

[Vitamin GMC]

Thankyou guys Ill look at the areas that you suggested, get back to you on what I find.

[Vitamin GMC]

Alright: Heres what I found with your suggestions, Checked all wiring, cleaned all the grounds, checked for power leading to the distributer, replaced the coil, already had a new distributer, Had power but then I wouldnt have power, ran a wire straight from the battery and bingo had ignition. That lead me to the cab wires, all checked out, the only thing left was the ignition switch, there was the problem. Some times with this type of repair and hunting it down, its nice to have a place to bounce these typ of questions with some one who has been through this before, thank you all for the suggestions

[bmartin9122]

Hopefully, I'll have time and money to do some tracking down next weekend.

[James McClure]

BMartin: Ain't it great to have some folks around that got "smart-A-tude". LOL. All kidding asside, glad you found the problem. Ign switch failures are kind of rare through the entire GM line so if this still happens there is only 1 place left to look, the firewall (bulkhead) connector. From the factory, it's filled with what I call "black goo" & thats normal. What your looking for is anything that has turned "green". Clean up the connectors and pinch the female part a TINY LITTLE BIT, grease it up with with "love lube" (vaselene) and reassemble it. If it's a manual trans check the clutch switch on the clutch pedal. I took mine out and by-passed it. I want to be able to use the starter to move the truck a bit if the eng quits. jim

[Thumpin455]

Just noticed this. What plugs are you running? They arent splitfires or anything like that are they? You dont have an ACCEL coil in the HEI do you? We have found both of those items to cause weird misfires and other strange stuff. Just something I felt could be mentioned.