Thread: SBC making me crazy (er)

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So It appears there are some pretty knowledgeable wrench turners on here, hopefully we can run down my demon. First off keep in mind I'm learning as I go and I haven't gone far. I did just replace the entire drive line though so I'm not totally useless.

I'm running a sbc 350 of mid 70' vintage (Had trouble matching the #s but I think that's close) in a jeep and I'm having a coupe issues. Its got a Holley truck avenger carb, possibly a mild cam but I'm not positive as the PO didn't know anything, and an Edelbrock intake manifold.

It used to be fine but now I have issues starting. It sometimes doesn't like to... Sometimes it jumps to life (cold, hot, whatever) other times it's a no go. It may start fine on monday, not tuesday, then I'll try again on friday and it runs like a champ. Sometimes you can crank it until the cows come home with nary a sputter. Sometimes after prolonged cranking it will catch and run fine. Sometimes I can smell gas like its flooded even though I never touched the pedal, other times some enthusiastic pumping will get it to go.

On a side note it has always had some throttle lag with this carb but I understand that's common with this setup and haven't tackled it yet. Finally, I'm getting a tad bit of smoke out the driver's side exhaust though it seems kinda intermittent. Not burning a noticeable amount of oil. I'm wondering if its electrical but not sure where to start. Or is it the carb? I've rebuilt many outboard carbs but this is a whole other beast.

Thanks!
-Patrick

70s vintage? points or electronic ignition?

one basic situation when sometimes an transplanted engine will start right away and other times when it will crank and crank but not fire up is a wiring issue with hot wire to ignition from starter solenoid bypass---------- in other words----ignition isn't powered by ignition switch when cranking---its from a bypass circuit in the starter wiring-----------

sometimes it will? but sometimes it won't? - - never know what it's gonna do? - - - sounds like you've got a "Female" Carb to me !

sorry, but that was too easy to pass - - no hi-jack intended here, good luck with your diagnosis !

Em

Yeah, its definitely a woman...
Electronic ignition, I think I follow you. How do I check for sure?

Originally Posted by sapelo

Yeah, its definitely a woman...
Electronic ignition, I think I follow you. How do I check for sure?

Lift your distributor cap and look under the rotor - it'll be clear if you have a set of breaker points in there. You say

Sometimes I can smell gas like its flooded even though I never touched the pedal, other times some enthusiastic pumping will get it to go.

In my experience, with a carburetor it's standard to get in, stab the throttle once or twice, depending on the engine, to get a shot of raw fuel in the intake, then crank it. It sounds to me like you may have a carb problem, and rebuilding it to get everything sealed up and a new accelerator pump in there may solve your problem. Of course, if you have no ignition power during crank, or an intermittent power during crank that will cause your fuel smell too. Next time it's not starting for you check for spark at the plugs - pull a plug wire, stick a Phillips head screw driver in the plug wire end and hold it about 1/8" from a good ground while a buddy cranks it - ought to have a nice blue/white spark and a healthy "POP, POP, POP" as it fires. If not check for 12V at the + terminal of the coil using a meter, ignition "ON" and also during Crank.

10-4 will dig in shortly.
Thanks!

Welcome to CHR!

Well you right in saying we’ve got some knowledgeable folks here. I learn from these folks all the time and appreciate the camaraderie that is found here. A Jeep with a Chevy small block has always been a real kick. Had a friend in high school that dropped a 327 in an old CJ and it was a real screamer – hard on axles – but a lot of fun to drive.

You’ve already got a few good suggestions concerning voltage at the distributor when cranking but for sake of argument I’m going to assume that you have proper voltage at the distributor as the vehicle ran when you got it and it sounds like it runs okay once it fires up. That said I’d still go through the basics and if you haven’t done so, procure and install new cap, rotor and plugs. If you have an HEI ignition points are not your issue. If you have a point type ignition, change them and set them at .024 -.026 and check the dwell. It should be 28 degrees. If you need help, buy a Chevy tune up and rebuild book from Amazon or your local book store. Chevrolet Engine Overhaul Manual (Haynes Manuals): John Haynes: 0038345103056: Amazon.com: Books

Next, download this document:
http://www.holley.com/data/Products/...0268-4rev2.pdf
It will help you diagnose, adjust and if required, rebuild your carb. If you have the stock fuel pump, your delivery should be fine. If you have an electric pump, get a regulator and a fuel pressure gauge and adjust to +/- 5psi.

Sounds like you may have a raw gas issue (could account for smoke – and definitely the smell). The Holley is fairly straight forward to rebuild and if you’ve done two-stroke outboard cards you should have no trouble here.

Regards,
Glenn

I would also check and replace any fuel filters as any small piece of crud that gets in a carb can find it's way to the needle and seat and wreak havoc.

Originally Posted by sapelo

Sometimes after prolonged cranking it will catch and run fine.

I'm on the same thought as "Jerry Clayton" on this, I would check the ignition to be sure it is on when the starter is cranking.

I had a car years ago that used a fuseable link wire to feed the coil when the starter was engaged, when the link went out it would not start while cranking but would occasionally catch as you let go of the starter.

Progress! Well, I went through all the connections (again) and cleaned them. Went ahead and added fresh plugs plus I replaced the coil. All seemed well. I drove it short distances for a couple days without issue then after a longer trip it refused to start while hot. I discovered I had no spark, a couple bubbas took interest (gotta love south Georgia!), one wound up being an excellent junkyard mechanic. He identified some wear in my distributor that I would have never noticed and concluded that it was shorting out and overheating the modulator. Pulled the slightly melted modulator and switched it for an old one he happened to have in his rig and she fired right up. So I limped home and ordered up a whole new distributor assembly. Looking forward to getting that in to see how she goes. Then I'll tackle the throttle lag issues. Thanks so much for the help gang!

Thanks for taking time to report back on what you found! Gotta love a V8 in a Jeep! I'd be buying a modulator for that bubba that was carrying a spare, just to say "Thanks".