Well, the '75 runs much better if you actually put gas in it. It was on E when delivered, I filled it half-way up with 92 and it's doing better now.

However, I think it still has carb problems. It will idle fine, but when you touch the gas the engine tries to die, and will shut off if you don't give it enough gas. If you give it too much pedal the carb seems to be backfiring. It does get better as you drive it and it warms up, but it's hard to get it going from a start without it dying.

I checked vacuum hoses a little but I'm not quite sure what I'm looking at anyway. Does this behavior sound like anything specific?

Jeff

 

I forgot to mention that the car diesels for a few seconds when you shut it off too. I don't know if that's related or not.

Is there a CFM range that is recommended as an aftermarket replacement for this carb? I wouldn't want to buy something too big.

 

Sounds like you have a vacuum leak. I'd plug everything and start from there to isolate the carb. A common source of vacuum leakage is the vacuum advance diaphram at the distributor. If you pull the hose off the carb and suck on the hose then cover it with your tongue it should maintain a vacuum...you should also hear the vacuum mechanism in the distributor. If you are getting a backfire, then check timing...again the vacuum advance may be the fault. Good luck.

 

My personal opinion is that you should just take out the old carb and intake and swap in it for a new one. A lot of people will say that you should just get a rebuild kit but i believe that its not woth it trying to fix an old, outdated bogged down intake system. Im guessing its a 350 with a q-jet, so i highly recomend a demon carb, theyre a bit more expensive than a holly or edelbrock but they defintely provide more performance and flow more air. Id also sugest getting a new intake manifold. The old intake manifolds are EXTREMLY heavy and bogged down with emmisons equipmemnt. I went with a performer RPM, its a good starting point if you want to get some performance or if you just want a daily driver. my .02 :cheers:

 

What kind of difference did you see with the 650cfm carb? Was there much in the way of tuning that Demon carb? Did you just plug up all the unused emissions hoses and other stuff when you put in the new manifold?

I'm seriously considering this. I've never taken out a distributor or swapped an intake before though. I don't even know how to set timing. :-P

I've only swapped carbs and have gone carb to EFI, etc.

Jeff

 

Well the driveability is WAY better and theres definitley better throttle response. never stalls, runs perfect. As for adjusting, you can adjust the idle speed and mixture, but to actually tune the air/fuel mixture you have to change jets. Thats about the only downfall that the carb has. As for the emmissions hoses, when you take off the manifold, all of them come off with it. So theyres nothing to really plug up. Youre gona have to get a drop base air cleaner though. the stock snorkel wont fit. As for actually taking everything off and swaping it out, it was fairly easy, a few rusted in bolts, but nothing to complicated. If you want me to i can send you an email with the details and explain more persisely how i did it!!! :cool:


[Modified by killervette666, 5:44 PM 1/20/2004]

 

Yeah that would be great, actually. Every little bit helps. :)

I only wish my dad would've taught me this stuff when I was a kid... :-/

 

Three years ago I replaced my old Holley with a Edelbrock (the Holley was leaking fuel and didn't perform very well). What a tremendous difference.
:thumbs:

 

phungus...

This is a good opportunity for you to develop your troubleshooting skills.

Carburetors don't back fire... the engine backfires from the combustion chamber past the valves through the head to the carb or to the exhaust system.

If the valves are okay (not leaking or bent) & the timing chain & gears are ok, then the backfire is caused by an ignition problem. .. spark plug is firing when a valve is open.

Don't go spending money on stuff you don't need.... the car will not run any better if you replace/repair the wrong component.

Learn how to check & set the timing.
It's extremely easy after you do it the first time.

After you check the timing- - check the timing chain & gears by removing the distributor cap & turning the engine over by hand... turn the crank one way until the dist rotor starts to move... then turn it back the other way. If there is a big gap in crank rotation before the rotor begins to turn again... you have a worn out timing set. A new carb will not fix that.

If the timing wanders all over the balancer and cannot be set/checked, chances are your timing set (chain/gears) is shot.

Check the easy, cheap stuff first.

Fresh cap & rotor? Caps can fall prey to "carbon tracking" inside the cap.... causing a backfire.

On a first pass, does sound like a vacuum leak to me though.




[Modified by Tom454, 6:13 PM 1/21/2004]

 

Youve got mail!!!

 

:eek: :eek: :smash:

 

When at idle there is very little advance or vacuum. Dieseling at idle with higher octane is likely an advance (BTDC, before top dead center) setting problem, particularly if the engine has high compression or shows carbon fouled plugs. Check the BTDC and advance the timing while setting it at idle, the dieseling will most likely go away. The Q-jet Rochester carbs are OK. They were even used for the 427CI engines and are still in my ZZ4 (CR= 1:10.5, with new jets and metering rods). Good luck

 

Thanks for the input guys. I'm really just trying to get this thing up to state inspection quality so that I can then start driving it and turn my focus to the real project... I have a new built 350 in another vehicle waiting to drop in. I'm not looking to stay original or anything because this car isn't nice enough, just trying to learn as I go.

I was out looking at it today and I saw several vacuum lines disconnected from various tees, also saw numerous wires that weren't connected anywhere. Aagh I've never had a car with so many vacuum hoses. Why couldn't they just have made everything electric? :)

I plugged a few hoses back in to where they should be and I'll see if I can go start it up tommorow. I didn't notice anything really *near* the carb, but what do I know. I did notice a cracked hose down by the canister on the drivers side. Several disconnected wires down there too. Hmmmmmmm.


Ugh, I need to figure out why my wipers don't work. Is all of that nasty black tar stuff really supposed to be by the wipers? It looks all cracked and rotted up there in the cowl. Pretty ugly. Does it come out? Looked like a vacuum hose was buried in it too.


I'll go buy a timing set and vacuum tester supplies soon. Maybe a compression tester and some new plugs too.


Jeff