Projects Chevy 250 running too rich. Need advise please

Thanks in advance for any help. I have a Chevy 250 out of a'68 Nova with a Rochester 2G that my father put in his 1967 109 Series Land Rover over 35 years ago. The cams got flat and it generally needed a rebuild so I pulled the motor myself and had it rebuilt by a good machine shop. They helped me set up the initial timing after I reinstalled it but it had an obvious vacuum leak. I was able to drive it home, pulled the manifolds and took them to a shop to have them lathed. The old duffer there told me the intake was too far gone and he would have to take off too much which would make it unusable. I ordered a new square bore Offy from Summit after hunting high and low for a OEM cast iron with no luck. Using various adapters, I put on the Rochester and fired it up. It ran great for about 3 minutes then gurgled to a halt. Plugs fouled. I put on an Edelbrock 1404 pushing 500 cfm because it is square bored and a better fit for the Offy but couldn't even get it started. I finally caved and had it towed to an experienced mechanic at a reputable repair shop where I have had work done before on it. He also has a 250 in his own truck so he knows the engine. He can't get it to start either. Got it running for about 3 minutes with the Edelbrock then it gurgled to a halt with fouled plugs just like me. I know this is most likely a timing issue but any suggestions would be appreciated. He wants to try different spark plugs but the plugs I am using are the recommended range and always worked in the past. The distributor is brand new as is nearly everything else. I never touched the fuel pump which is rated at 4 psi and fuel filter is pretty new. ARRRGH!!!

 

Did you set the float level on the carb? Is the choke open? You might need to replace the spark plugs with new ones after fixing the fuel problem. Once they get fouled too badly, they sometimes never work again (I've seen this happen a few times).

I have two stock manifold sets in my barn....huh...

 

Brand new plugs! Didn't touch the floats but the Edelbrock is straight out of the box. The Rochester I took to my carb guy who did a great job rebuilding it last year and he had no trouble getting it to run on his test bed. I have seen stuff about recurving the distributor but that seems pretty far over my head.

 

Oh and choke is open.

 

Timing won't cause what you are having trouble with. Check the floats, most likely dirt in the needle and seat. I think mine is around 12 to 24 degrees @ idle running 87 octane fuel. It will run with more or less with out any trouble, fuel mileage seems best where it's at.

 

In the box with a new Edelbrock carb is an instruction book that says you have to check the floats before you install the carb.

See if it helps...don't cost nuthin'.

Having the timing off will not make it run rich.

 

Are you sure it is rich?? A weak coil would give very similar indications, which, coupled with the stalling, would be my first check.

Cosmo

 

Edelbrock you say?

What is your fuel pressure set to?

 

Well I could see why the Edelbrock floats may be off because it hasn't been checked since going from box to manifold, but the Rochester 2G is dialed in and has a lower cfm yet still the same result. Again, thank you for all suggestions.

 

oh and fuel pressure is 4 psi and coil is practically new and worked fine before the rebuild.

 

It sounds like you're convinced there's nothing wrong with it, so it's kind of hard to figure out what's wrong with it. If it has some crap in the fuel system keeping the float valves open, it might do what it's doing.

Pretty hard to figure it out with the info given, unfortunately.

 

Put a timing light on it while someone cranks it. Report back where the line was.

 

FWIW, I had a brand new Edelbrock 1406 on an SBC and had similar problems getting it to run correctly on an engine that already had good running history. I went through the carb and found little slivers of metal here and there from the machining blocking passages etc. it might not be a bad idea to go through the the carb anyways. Even if you don't find anything you can eliminate blocked passages, needle and seat issues/ floats from your list.

 

I have seen numerous Edelbrock carburetors with their floats out of calibration, brand new.

Given the condition of the box, I suspect that was from UPS Next Day Trebuchet delivery.

So glad Summit switched to OnTrac for my area.

I have also seen the conditions that Devin mentioned.

 

also slap a vacuum gauge on it to see what the reading is a leak will show up this way ( and make it run rich ) , and do not forget to spray around the manifold where it joins the head to see if it straightens up as the mounting system they use on them straights is not the best and can develop leaks easily ,
I had a 292 in a truck that would not idle slow for many years and found a stud was not allowing the nut to screw down all the way and compress the gasket and causing a leak . had to replace all the fasteners to fix the problem

 

I tend to agree with others that timing is more than likely not the problem. I have messed with the timing in mine and it will run pretty OK from 4-14. Like someone else mentioned, the only difference is a little more power and better fuel mileage closer to 14 running on 91 octane. Slap a vacuum gauge on there and see whats going on.

 

Well the Rochester is back on but it still wont start. I'll check timing marks as suggested and also recheck for vacuum leaks. I have a vacuum gauge installed and it was right on the money for the few minutes it was running. Thanks everyone for the suggestions!

 

What kind of distributor is it? HEI, points, other?

 

http://www.oreillyauto.com/site/c/detail/A1C0/301612/02780.oap?year=1968&make=Chevrolet&model=Chevy+II&vi=5157283&ck=Search_02780_5157283_3691&pt=02780&ppt=C0334

I was just thinking about it that I might try a different unit. I had a similar situation before the rebuild with my alternator. I bought a remanufactured one from O'reilly's and it was defective right out of the box. I replaced it with a new one and it worked great. I'm wondering if the distributor is also malfunctioning even though it is new.

 

Stovebolt guru Tom Langdon generously called me today to discuss the matter. First he pointed out possible vacuum leak issues I may be having and not realizing and then he pointed out that all aftermarket distributors like the one referenced above are made by Cardone and they all have a design defect with the bushings. Not that this is the source of my grief but he strongly advised to go to HEI which I will be doing. But still not running .....

 

The later Chevy inline sixes are kind of notorious for bushing problems. I think initially they used two bushings, one at the top and one at the bottom of the distributor housing.

Then somewhere along the line, to save a couple pennies, they just put a single bushing in the middle of the housing. After some miles the I.D. of the bushing began to wear in an hourglass shape and dwell and timing would get erratic. They'd still run fairly well with a bit of throttle but wanted to idle poorly. Then they'd get hard to start or with enough wear and an old set of points they wouldn't start at all.

If you pull the distributor be sure to check for excessive side play in the shaft. If you can find a real ignition shop somewhere they may be able to rebush the housing for you.

 

Okay first of all thank you to all that responded. It was very helpful advise. Also thanks to Tom Langdon over at Stovebolt for returning my phone call and advising me on conventional versus HEI dizzys. I bought one from him. You should too. As is nearly always the case, the problem was merely a simple human error. Instead of using a keyed constant power source, I mis-wired the coil's 12 volt supply by mistakenly hooking it to the starter condenser which I replaced AFTER I got it running the first time. The result was every time I pulled a spark plug and turned the key to check for spark it energized the coil and fired the plug which made it appear as though the distributor was functioning, when in fact as soon as I let off the key it would de-energize the dizzy and kill the engine. Learn something new every day - that is why I love wrenching!

 

Wow, didn't see that coming. Good catch.

 

Hi. Glad you found the problem. I definitely second Tom's HEI distributors. When we were building the 235 engine to go in my 46 coupe the mechanic kept recommending a Petronix but I did not listen and ordered the Distributor & coil from Tom. Best thing I did on the engine during the build was make that choice because should it ever have a problem internal parts are avalible in all auto parts stores. Runs great too.
Coupe is going back in the shop tomorrow for new wiring harness, vintage air, seat belts & a trailer elect plug so I can tow my teardrop trailer & then it really will be hit the road time for me.
Jimmie