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Here again with another question. I've got a 1969 C3 5.7 L 350 engine. Got her about a year ago, total car newby, but thanks mostly to you guys I am learning.
The car is my daily driver. I stick to neighborhood streets, low speed, just a few miles distance. So I rarely get above 60 mph. But when I do go on the freeway, or when I need a quick boost of power, the car just isn't performing.
The absolute max I can do is 80 MPH on the freeway. And it takes a loooooong time to get going that fast. The car is very low power and very gradual in building up speed. I need tips on how to help the car's performance! I have attached pics of my engine setup and carb.
So what do the experts think? How can I improve this engine and give her more power? Any and all suggestions are welcome, again, I'm still learning.
!
My friend has a '70 with the same carb setup as you have. One problem that he had with his was that the air filter base was pushing down on the rubber fuel inlet. It eventually broke the hose and he had fuel spraying on top of his engine. We just ordered a banjo style fuel inlet line that passes under the choke housing and then goes straight up to the carb inlet. Look at Edelbrock P/N 8131.
Been an exciting and stressful few weeks! New fuel filter. New fuel line. Fixed gas pedal. New oil and filter. Transmission change and filter. Compression and timing tests (both great). Engine sounds MUCH better and already noticeably faster! I have a few concerns, but will post them below. Check out new look.
1. The engine roars, but it's still very "air-y" or "breathy" in my car-ignorant terms. When I hit the gas, it still doesn't jolt forward with power like I want to. It just sort've revs up with what sounds like mostly air, like you're turning up an AC unit at home. Is this normal? Is the problem that the car is getting too much air and not enough fuel? Check out what the engine sounds like in the video I have included.
2. Maybe an even bigger concern is I am hearing ticking that I haven't previously noticed until the last couple of months. One that I just noticed today. Let's start with that.
The noise comes after the engine has run for a bit. It's a light to medium tapping heard when I press the gas. Even slightly. It's a rapid tapping, and the speed/noise level of the tapping doesn't really change much whether I'm barely pressing the gas or whether I'm laying down on it. I've included a video. Keep in mind, the car is in park during the video. Thoughts?
Last edited by BlankSlate; 05-18-2019 at 03:49 AM.
3. The other tapping I have heard for a month or two. It seems to be a rhythmic ticking that coincides with the engine's idle. Is this just a normal thing? I tried to track the source of it. Mechanic thought it was from a missing exhaust manifold plug. We fixed that, but the ticking is still there. You can't hear it when leaning over the open-hood. But you can hear it behind the wheel. And you can hear it at its loudest when you bend down by one of the wheels. Any guesses?
Note: In my first video, you can hear the ticking if you listen closely at the VERY beginning (before the camera is raised to show the engine).
Next up, PCV valve question. Do I have it currently set up? I have no idea.
Check out the pics of my setup above. As you can see, I have a hose running from the carb to the oil port on the driver's side valve cover. From what I have researched, I think that the hose's purpose is for the PCV. Yet, on all the setups I have seen for corvette PCVs, there is supposed to be a hose running from the air filter to a cap on the passenger side valve cover. I don't have that.
Please let me know how I can set up my PCV valve, if I don't already have it set up. I hear it can help the engine a lot. Maybe help with my breathy problem?
Last post for the night. Not really a question here, but wanted to post another vid that will allow you to listen to the engine. How's it sound, in relation to how it's supposed to?
First of all.
Welcome to the forum.
Second
You will find a lot of useful info on here from experienced folks with many years of background with our corvettes.
Third
You will find a lot of misinformation on here also. Some posters, though well intentioned dont have a clue. Be leery of a guy who sounds like a pro but is really just an avid internet commando and has little or no hands on experience. I'll not mention names.
Finally, stick to the guys who have been around for years or people who other people recommend....like our resident carb guru...Lars.
Wish I had seen this thread at the beginning. That Edelbrock 1407 is a square bore carb with 4 equal butterflies. Your stock manifold was designed for the quadrajet carb which is a spread bore design.
Of course aftermarket adapters are available but somewhat of an inexpensive bandaid.
Bubba certainly has worked on your car at some point.
Glad to see you made good progress.
You are learning.
My only concern looking at this pic on my cell phone is your new fuel line. Looks awfully long and hard to tell but could be close to your exhaust manifold. Check that out.
While on the subject of fuel lines these cars were built with steel fuel lines from the tank to the pump to the filter to the carb with very minimal use of hoses. There is a reason for that. If you ever took your car to the track they would not let you run with any more than 12 inches of total rubber line.
On these cars...first focus should be safety, then power and speed.
Good luck with your new baby.
The search function and the AIM/shop manuals are your new friend.
Last edited by bmans vette; 05-18-2019 at 07:20 PM.
First of all.
Welcome to the forum.
Second
You will find a lot of useful info on here from experienced folks with many years of background with our corvettes.
Third
You will find a lot of misinformation on here also. Some posters, though well intentioned dont have a clue. Be leery of a guy who sounds like a pro but is really just an avid internet commando and has little or no hands on experience. I'll not mention names.
Finally, stick to the guys who have been around for years or people who other people recommend....like our resident carb guru...Lars.
Wish I had seen this thread at the beginning. That Edelbrock 1407 is a square bore carb with 4 equal butterflies. Your stock manifold was designed for the quadrant carb which is a spread bore design.
Of course aftermarket adapters are available but somewhat of an inexpensive bandaid.
Bubba certainly has worked on your car at some point.
Glad to see you made good progress.
You are learning.
My only concern looking at this pic on my cell phone us your new fuel line. Looks awfully long and hard to tell but could be close to your exhaust manifold. Check that out.
While on the subject of fuel lines these cars were built with steel fuel lines from the tank to the pump to the filter to the carb with very minimal use of hoses. There is a reason for that. If you ever took your car to the track they would not let you run with any more than 12 inches of total rubber line.
On these cars...first focus should be safety, then power and speed.
Good luck with your new baby.
The search function and the AIM/shop manuals are your new friend.
Thanks! The steel braided fuel line is longish. Is that bad? Doesn't seem to move much but it is long.
Thanks! The steel braided fuel line is longish. Is that bad? Doesn't seem to move much but it is long.
Not what I would use.
If you think it might be laying down on the engine, then either shorten it or come up with some brackets that hold it solidly and up off the engine. Or both.
Keep working on it.
Nothing like hands on experience especially if you have some more experienced person guiding you.
Keep posting.....
BTW...fiberglass burns really fast and really easy.
Stay away from those open top foam air filters for the carb. A simple backfire and the foam ignites under your hood. By the time you notice it the hood will be in flames.
Do a google of that and you will see some Youtubes of that.
A fire extinguisher mounted on the floor within easy reach is a real good idea. Some put it in front of the passenger seat.
Last edited by bmans vette; 05-18-2019 at 07:27 PM.
Been an exciting and stressful few weeks! New fuel filter. New fuel line. Fixed gas pedal. New oil and filter. Transmission change and filter. Compression and timing tests (both great). Engine sounds MUCH better and already noticeably faster! I have a few concerns, but will post them below. Check out new look.
I think that air filter is WAY too small! The Edelbrock 1221 filter assembly is 14" diameter, and with a 2" high element, it will fit nicely under that hood. Think about the filter surface area. If you want your engine to make full power, then you have to let it breathe without restriction from the filter.
John
I think that air filter is WAY too small! The Edelbrock 1221 filter assembly is 14" diameter, and with a 2" high element, it will fit nicely under that hood. Think about the filter surface area. If you want your engine to make full power, then you have to let it breathe without restriction from the filter.
John
Even 2 inches is going to be too high. But I agree I need to put the bigger cleaner back on. I will have to cut a paper filter in half and screw it down tight. That's what I have done with the current air filter there. It's cut down to probably less than an inch tall.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
yes your PCV system will work that way. That chrome filter is pulling pressure out of your head and into the carb PCV intake system You could take the fill plug out and put a filter on there so its drawing air in there and out through your current system.
I tried listening to the recording and it sounds llike it could be an exhaust leak on my laptop speakers. I dont have any headphones handy. If it is tapping, it could be a loose rocker which is easy to set if its hydraulic.
If you dont have a specific area that its coming from, stick a length of hose in your ear and use it like a stethoscope. A garden hose a few feet long will help you isolate it to an area. Then you can hold it right on the the area like a valve cover or manifold to get a more definite decision. If it isnt that specific on the object your checking, get either mechannics stethoscope or just a long screwdriver and stick the handle in your ear and touch the object you are checking. You have to touch it though
And to add to the fuel line, hot fuel will cost horsepower, cold fuel will increase horsepower, so shorten that line and get it off of anything that is hot.
Last edited by Rescue Rogers; 05-19-2019 at 04:30 PM.
yes your PCV system will work that way. That chrome filter is pulling pressure out of your head and into the carb PCV intake system You could take the fill plug out and put a filter on there so its drawing air in there and out through your current system.
I tried listening to the recording and it sounds llike it could be an exhaust leak on my laptop speakers. I dont have any headphones handy. If it is tapping, it could be a loose rocker which is easy to set if its hydraulic.
If you dont have a specific area that its coming from, stick a length of hose in your ear and use it like a stethoscope. A garden hose a few feet long will help you isolate it to an area. Then you can hold it right on the the area like a valve cover or manifold to get a more definite decision. If it isnt that specific on the object your checking, get either mechannics stethoscope or just a long screwdriver and stick the handle in your ear and touch the object you are checking. You have to touch it though
And to add to the fuel line, hot fuel will cost horsepower, cold fuel will increase horsepower, so shorten that line and get it off of anything that is hot.
Thanks! For the fuel line, it's not touching the engine. It's resting on a heater hose, but I wrapped the section of the hose and fuel line in heat resistant tape.
As far as the PCV, so I do or don't need to run a hose up to the air cleaner? I am just confused on how the guy before me has set this up. Are you saying that with my current setup, the PCV system is already working and I don't need to do anything?
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by BlankSlate
Thanks! For the fuel line, it's not touching the engine. It's resting on a heater hose, but I wrapped the section of the hose and fuel line in heat resistant tape.
As far as the PCV, so I do or don't need to run a hose up to the air cleaner? I am just confused on how the guy before me has set this up. Are you saying that with my current setup, the PCV system is already working and I don't need to do anything?
As for the PCV system, You should have fresh air going in so that its easier for the vapors that are in there to get sucked out. You dont need a hose going to the air cleaner, you can just use a plug in little valve cover breather in the oil fill hole. https://www.summitracing.com/parts/k...1490/overview/
Here's a PCV diagram that is so old (in Internet years), that it is a static GIF!
The breather hose on the passenger side lets in filtered air from the air cleaner (and, consequently, prevents oil vapor mist from covering your engine compartment). The PCV lets the manifold vacuum suck out the blowby vapors, and that's the important part, but there must be a breather on the other valve cover, too, whether pulling from the air cleaner through a filter (stock in later years), or just from the engine compartment (as many aftermarket systems, do).
Have you considered a drop-base air cleaner? If you can find one that fits, it might give you more filter area for the same hood clearance.
You may also want to pickup a mechanic's stethoscope to diagnose the location of engine noises. A vacuum hose will work in a pinch.
04-29-2019, 07:57 PM
