Hey guys, The engine in my 62 chevy decided it wanted its crankshaft in two pieces back in may. My buddy lent me an engine he had sitting on the stand until I can get the original one rebuilt. I got the engine in the car and had a heck of a time trying to time it because he gave me a 305 balancer to use on the 350. Neither one of us realized that the timing mark was in the wrong spot. It ran okay at part throttle but would pop when the secondary's kicked in. Well last night I put a new 350 balancer on and set the timing at 10 degrees initial and the mechanical advance is 25 degrees so 35 total. There is no vacuum advance. It was idling great, sounded really nice and had good throttle response. I went out on the road and leaned into it and as soon as the secondaries started coming on it would fall on its face and want to shut off. It runs great at part throttle. I checked the dwell and it's at 25 which is a little out of spec but i don't think it would cause this. I would assume the carb is tuned right, he had this exact engine/carb in his camaro and had it tuned for the strip. Any ideas as to what could be wrong? Information: Chevy 355 Flat top pistons Ported bathtub chamber heads Mild Camshaft Edelbrock Performer Intake Edelbrock mechanical choke quadrajet 2" rams horn manifolds with 1 7/8" dual exhaust Manual Transmission All parts below were new last year and only have 4,000 miles on them. Plugs Wires Cap Points Condenser The firing order was triple checked. All the wires are where they're supposed to be. Thanks, Incognito
Make sure the secondary air valve is working properly. If the allen screw retainer on the spring pre-load is loose the air valve will "fall open" and just flood the engine....if it isn't adjusted correctly it will do the same thing. Some guys mistakenly label the Quadrajet a "quadra-bog" carb because they are too lame to set it up right. That air valve should just slowly feed in the secondary as the engine can handle it. All the other stuff you listed sounds right. Good luck.
you assumed he had it set up right is the main problem you can never assume anything when your buying used stuff, especially when the guy had the wrong balancer on the motor in the first place the only thing you can assume from that point on is that the p.o is a dumbass. i would start with the carb sounds like the issue to me
Thanks, I'll have to check that out. I have a couple extra quadrajets lying around that i might try as well. I rode in the car, and watched it at the strip. It was dialed in right. The engine and carb. have been sitting a few years though, so it could be some gunk in the carb. or a linkage problem. I knew the balancer he gave me wasn't on the engine, he said so right when he pulled it out. We both assumed that since a 305 and 350 are both internally balanced it would work. Neither of us realized that 305's are timed from between the water pump and block. The balancer that was on there was a SFI one that he swapped over to his new engine. He's a good guy and is by no means a dumbass. He lent me the engine no strings attached so I wouldn't be car-less for the summer. I do agree with you though, if buying from an unknown source, never assume it's as they say it is. That's when you get into trouble.
Yikes, I've had a lot better luck with quadrajets and AFB's than holley's. Those zinc plated 600 CFM carbs they made in the late 80's and early 90's were junk. I'm not saying they don't make a good carb, but I'll stick to something I've had decent luck with. I've been away from tinkering with quadrajets for 10 years now so it will take some time to get used to it again.
Hi you write your dwell is 25....it should be about 30....when the dwell changes the timing will change,...so at the 25 dwell the timing will be off from the very start......check the timing at the 25 and then check it at the 30 and see what the difference is...set the dwell 1st and then the timing......Miller
You're probably wasting your time with that carb,it has sat too long. Rebuild it or get a new one.I can almost guarantee the thing is varnished up inside. I don't think gas is what it was a few years ago. I park my hotrods all winter and if they aren't started every week or so,the gas turns into varnish and the jets plug up. I've had this happen with a brand new carb. Of course,I think you should check your fuel filter and pressure first,and make sure you didn't kink off a fuel line when the new motor was installed.
I love the quad it makes great power and easy to tune. shave the pump shaft and work the well area and your set. on the motor I would have to start at 1st base get it top dead and make sure the timimg chain is right then go forword from there. find a HEI. I tune with a vacum gauge it reads vacum and vavle operation.
Timing is off 2 degrees for each degree of dwell change. Dwell should be 30 so you are 10 degrees of timing off right off the bat........adjust the dwell and start over........
Some had a very small sintered brass filter under the fuel inlet fitting. Could be blocked. Verify fuel pressure then move on to the carb. Can't make a silk purse out of a sows ear. Those QJ's are notorious for overly sensitive air valves and can over carburate in a second if you have the valve open prematurely. I recall being able to increase opening resistance. Think with the top off you loosen a setscrew and add/ subtract opening preload.
Thanks for the replies. This weekend I took the car up by a buddies place that is an expert for tuning stuff up. We set the dwell, put a bit more advance at the engine, and readjusted the carb. Part throttle improved a lot and it will get into the secondaries but it still coughs up high. I tried a couple different settings for the air valve. I also took the small fuel filter out of the carb inlet and am running a larger external filter. We're thinking it's a problem with the carb or fuel system. I'm going to try a few more things, but since a new engine/carb is going in this winter I don't know how much time I'm going to stick into solving this.
The Jalopy Journal
