1974 Camaro Z28
Discussion
Well it's the height of show season, so I've had the Camaro out and about. So far still haven't seen another '74!
The plus side to all this is that is that I got chatting to another owner who advised me that I'd be better swapping over the vac line on my carb...
...so I did. I won't pretend I understand the intricacies of it at the moment, but what I do know is that my idle has slightly increased and as a result my temperature is now holding steady and there's no longer any boiling over at all. Fixed!
The plus side to all this is that is that I got chatting to another owner who advised me that I'd be better swapping over the vac line on my carb...
...so I did. I won't pretend I understand the intricacies of it at the moment, but what I do know is that my idle has slightly increased and as a result my temperature is now holding steady and there's no longer any boiling over at all. Fixed!
No doubt you have seen this one up for sale? Looks a beauty.
https://www.ebay.co.uk/itm/Restored-1978-Chevrolet...
https://www.ebay.co.uk/itm/Restored-1978-Chevrolet...
Shnozz said:
No doubt you have seen this one up for sale? Looks a beauty.
https://www.ebay.co.uk/itm/Restored-1978-Chevrolet...
I have, that's the third 2nd gen I've seen black/black in the last few weeks at over 20k. I'm more than happy that I only paid a little over 7k for mine https://www.ebay.co.uk/itm/Restored-1978-Chevrolet...
Rogue86 said:
The plus side to all this is that is that I got chatting to another owner who advised me that I'd be better swapping over the vac line on my carb...
...so I did. I won't pretend I understand the intricacies of it at the moment, but what I do know is that my idle has slightly increased and as a result my temperature is now holding steady and there's no longer any boiling over at all. Fixed!
This is where these cars are fantastic for getting a knowledge of how engines work and how you can make them perform better (or worse) with such simple changes. ...so I did. I won't pretend I understand the intricacies of it at the moment, but what I do know is that my idle has slightly increased and as a result my temperature is now holding steady and there's no longer any boiling over at all. Fixed!
What you have there are two vacuum ports. One is above the butterfly in the carb (timed port), the other is below it (manifold port).
Now if you imagine when the engine is running it is drawing in fuel through the carb. The butterfly is the valve that controls the air flow into the engine. When it's shut you have a pressure difference, there is a vacuum on the inside and outside there isn't, air is just being drawn in, but it's at relative air pressure. However, when you go wide open or roll on the throttle, the pressure vacuum begins to build on the port above the butterfly as the engine draws in more air.
By the sounds of it, your distributor has been connected to the port above the butterfly, so your timing will only advance as you roll onto the throttle and go wide open. This is great for fuel economy and it's how a lot of cars during the SMOG era were sold. Now for performance, ease of starting etc, a lot of people find connecting to the manifold port better.. This give you a constant vac advance at idle, which is what you're seeing now your idle RPM has increased. More timing will increase the RPM as it is burning more of the fuel from starting the combustion sooner.
Something to check though is your timing. Running hot (although it now sounds to be cured) can be from running too lean and also running too much timing to the point of detonation and pre-ignition. I've found my SBC run best between 34-36* all in timing. I also like to get my timing in as soon as possible, so run light springs and aim to have all in by 2500RPM, but every engine is different and will depend on the specs of your engine.
All the best with it and have fun, I've always fancied a manual yank, but so far have only stuck with the autos for racing!
Thanks for that explanation - makes it much clearer than I had it in my head! As you say, these cars are great for learning about basic mechanic skills/theory.
I'm not sure I'd say you're missing a great deal with the manual box, it's very agricultural! It is great fun when though trying to heel/toe in something like this though
I'm not sure I'd say you're missing a great deal with the manual box, it's very agricultural! It is great fun when though trying to heel/toe in something like this though
The car has finally thrown its first real wobbly in my ownership. Having gone to take the car out for a drive, the key felt like it turned one step too far and the engine didnt even try to turn over. I figured it was a problem with the ignition barrel as I then couldnt get my key out, so I managed to source one in the UK and make some time this weekend to fit it.
I'm far from a mechanic so just try to reverse-engineer what I can see and work out how it operates. Initially I dropped the column but then found that to be unnecessary. With the wheel off and the sandwich plate removed (which was tricky without specialist tools!) I was here.
It turns out that once you get to this stage, you have to chisel some of the soft metal away to force a screwdriver through and press the tab.
With the tab exposed, I got the barrel out and found that it works absolutely fine. So time to have a look inside and see what isn't working!
I soon found this gear with two teeth missing, one of which was sat next to the gear having obviously just broken off.
From what I can work out, the gear moves an actuator rod that then completes the circuit with the ignition switch. With the front two teeth missing, the actuator doesnt move far enough to make the contact.
However accessing it through the barrel would have been far too easy! So I separated the next section of the column.
Tricky, but there is enough width to get a screwdriver in the back and prize it off.
Finally, problem part out!
I've found the part online, but at $16 plus $63 shipping I'm trying to find alternatives. At the moment a friend has a 3D printer so he's going to try scanning/repairing it in 3D and then printing me another.
I'm far from a mechanic so just try to reverse-engineer what I can see and work out how it operates. Initially I dropped the column but then found that to be unnecessary. With the wheel off and the sandwich plate removed (which was tricky without specialist tools!) I was here.
It turns out that once you get to this stage, you have to chisel some of the soft metal away to force a screwdriver through and press the tab.
With the tab exposed, I got the barrel out and found that it works absolutely fine. So time to have a look inside and see what isn't working!
I soon found this gear with two teeth missing, one of which was sat next to the gear having obviously just broken off.
From what I can work out, the gear moves an actuator rod that then completes the circuit with the ignition switch. With the front two teeth missing, the actuator doesnt move far enough to make the contact.
However accessing it through the barrel would have been far too easy! So I separated the next section of the column.
Tricky, but there is enough width to get a screwdriver in the back and prize it off.
Finally, problem part out!
I've found the part online, but at $16 plus $63 shipping I'm trying to find alternatives. At the moment a friend has a 3D printer so he's going to try scanning/repairing it in 3D and then printing me another.
First test print, looks pretty close:
Luckily (depending on how you see it) an accidental drop highlighted our first issue - it's made of ABS plastic and the original is nylon. A quick test in the ignition barrel after the impact and it sheared the end off.
So time for a re-print and test-fit tomorrow!
Luckily (depending on how you see it) an accidental drop highlighted our first issue - it's made of ABS plastic and the original is nylon. A quick test in the ignition barrel after the impact and it sheared the end off.
So time for a re-print and test-fit tomorrow!
Managed to get some time on the car on Saturday with the new nylon gear, as well as a glued ABS spare. I also decided to get the ignition switch off and clean it up as the last 'step' was very stiff. It seemed quite obvious how the whole thing works once it was apart - the gear moves an actuator, which in turn moves a long metal rod (much like a bicycle spoke) which slots into the ignition switch.
"How hard can it be?"
Luckily a friend was on-hand with a better memory, so we got it all back together. Unfortunately, both gears sheared off in the same place. Our conclusion is that it's down to how 3D printers work, printing laterally and giving it an easy weak spot. If printed the other way round, it would simply shear the teeth off. Luckily Ive managed to find an OE part which appears to be injection-moulded so a lot stronger.
I haven't driven the car now in almost 6wks, so I managed to bodge it and get the car started. My friend has a lovely 67 so we went for a little drive to blow the cobwebs off.
Alright, so a little too giddy at times...although it looks more dramatic in this photo than it really was!
Nice to be back behind the wheel again though and the car was very well behaved.
"How hard can it be?"
Luckily a friend was on-hand with a better memory, so we got it all back together. Unfortunately, both gears sheared off in the same place. Our conclusion is that it's down to how 3D printers work, printing laterally and giving it an easy weak spot. If printed the other way round, it would simply shear the teeth off. Luckily Ive managed to find an OE part which appears to be injection-moulded so a lot stronger.
I haven't driven the car now in almost 6wks, so I managed to bodge it and get the car started. My friend has a lovely 67 so we went for a little drive to blow the cobwebs off.
Alright, so a little too giddy at times...although it looks more dramatic in this photo than it really was!
Nice to be back behind the wheel again though and the car was very well behaved.
Thanks Ben!
The replacement part turned up, I believe it's out of a slightly later Camaro. This one is made of metal though so should be up to the job!
A friend of mine also commented on the noise the gearbox makes and after a little digging, it turns out it's the Muncie 4spd 'rock crusher' which was the one to have on 70s muscle cars. Sounds a lot like a straight-cut box so it's very noisy!
Managed to get the car out to AMT for a supercar meet at the weekend too. Behaved well in the traffic and despite being probably at least £30k cheaper than any car there it drew quite a lot of attention. (thanks to Mike Thomas for a few of these shots on a proper camera!)
Mr lestat said:
You could always just use the ignition barrel to just turn things on. Then wire in a starter button for the final push to actually start it
With the car being numbers-matching, I'm trying to keep it original at least to the point I can return it to OE later in life. I think a push-button start will be a little fiddly to later return to stock.The replacement part turned up, I believe it's out of a slightly later Camaro. This one is made of metal though so should be up to the job!
A friend of mine also commented on the noise the gearbox makes and after a little digging, it turns out it's the Muncie 4spd 'rock crusher' which was the one to have on 70s muscle cars. Sounds a lot like a straight-cut box so it's very noisy!
Managed to get the car out to AMT for a supercar meet at the weekend too. Behaved well in the traffic and despite being probably at least £30k cheaper than any car there it drew quite a lot of attention. (thanks to Mike Thomas for a few of these shots on a proper camera!)
Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff