It's been a while..... Anyways...I started a new job, and am taking over the last guys work. It's a 64 belair with a rebuilt 283...mostly stock with trick flow heads, mild cam(about .420 lift kind of thing) and a new Holley 6210 spread bore carb, and a petronics ignition. I just cant get it to run right....has black smoke, and falls flat and pops. The carb doesn't seem to be flooding, and the mixture screws are about 1 turn out. With the initial timing set at 8 deg, and the choke properly set, it starts great cold and idles decent, but no power.... Any thoughts would be appreciated! Thanks in advance..... Sent from my SM-G960W using The H.A.M.B. mobile app
most carb problems turn out to be ignition, How long since the rebuild? If they installed one of those cheep so called roller timing chains its a good chance its now loose. grab the harmonic balancer and move it back and forth to feel the slack in the timing chain. late cam timing makes a engine luggish. do the basics run a compression test. There aint a piece of cast iron in the world that can fool you unless you let it.
Get it warm and then turn in about 12* advance on the timing..........screw both adjustment screws in and back out 2 full turns. See if THAT makes it any better. You are using a good timing light, right?! 6sally6
What old wolf said. Check ignition timing? Pertronix is good ? Installed properly? If unsure try your points again? Vacuum gauge reading? Valve adjustment? Electric or mechanical fuel pump? Fuel pressure at carb? Plugged/ dirty fuel lines/tank? Compression test? Leak down test? Good grounds? Good battery? Vacuum leaks? Base timing? Carb confirmed good and all adjustments correct? Are you shoes tied correctly? Did you read this whole list? Pretty much a guarantee if you check all this stuff the car will be running like a top in no time. And other then the compression test and leak down test this can all be accomplished in under 2 hours..... that is if you tied your shoes right.
Check the timing @ about 3000 rpm, maybe the advance weights are sticking, should be about 22 degree movement when full advanced .
The only poop that I have seen run, messes up my underwear. I agree with the theory that perhaps the advance isn't working.
I would check to see if the coil is the right one for the petronix I’ve seen that foul things up more than a few times.
Depending on how the cam was broken in and how much time it has spent idling, starting/stopping without being driven, the oil used etc...you might also want to check for a flattened camshaft lobe.
Is it a new build? Did it ever run right? If new, is the cam out of sync? Is the distributor installed properly?
Holleys often have problems with power valves and accelerator pumps which cause them to behave erratically. Also, if you've looked in all the normal places for vacuum leaks don't forget the diaphragm in the vacuum advance unit and the power brake booster. I've had vacuum leaks in both places and they will drive you crazy! Good luck!
I had a somewhat similar problem, the engine wouldn't RPM, started back firing at 3000 RPM (if I remember correctly), I changed carbs, intake's distributors trying to figure out why it wouldn't run properly. What I should have done (and I would have saved lot's of money had I done so) was to check the cam timing. I had installed a Cloyes timing gear set so I could advance and retard the cam, but....I must have been taking stupid pills because I didn't align it properly. On a 38 Chevy you have to pull the front clip to really get at the front of the engine which was part of the reason I hadn't done it. After dropping the pan and pulling off the front cover I immediately saw what I had done wrong. The cam was out about 20 degrees, I reassembled it and it ran fine, it really RPM's now The only upside is I have parts leftover to use on the 53 Studebaker. This may not be your problem, I just shared my experience of infamy so the reader can get a laugh and say "I've never done that"
All replies are excellent advice. If the car sat for a long time, don't forget to consider a blocked exhaust (mouse nest) , or even a heat riser that won't open if it has stock manifolds. Just a thought.
I am back on this one today... You guys have given me a lot of good ideas, and I appreciate that! The engine is a fresh build with about 30 miles on the clock, with every imaginable part being new...sometimes it gets a little overwhelming! I will report back later this morning! Sent from my SM-T350 using The H.A.M.B. mobile app
First thing I would do is put a set of Accel points and condenser in it, set the dwell and then set the timing. Check the mechanical timing advance by scribing a line on the damper 3/4" away towards advance from the original and use a regular timing light. Make sure the coil has a resister.
Ok...here's what I got.... Has new msd wires 10 deg initial timing, 31 deg advance at 2700 rpm Checked the rocker adjustment...all set correctly. Plugs are new, but have a lot of soot. Will pop from the exhaust at times. When running decent, only has 12 in of vacuum Tried known good edelbrock carb with no change. I checked the voltage from the coil wire with a snap on kv probe and it shows 7000 volts, but on the plug wires shows 2000 volts. All plug wires have about 2000 ohms resistance, and are in the right order..... Sent from my SM-G960W using The H.A.M.B. mobile app
Ok...things changed!....forgot to plug off one vac port.... Set the mixture screws....runs amazing and has 19 in of vacuum! It's like a whole different animal now Will be returning that carb under warranty. Thanks for all your help guys! Sent from my SM-G960W using The H.A.M.B. mobile app
Since everything else seems to be pretty close to right snooping online brings up this bit= A vacuum reading at idle that is much lower than normal might indicate leakage through the intake manifold gaskets, manifold to carburetor gaskets, vacuum brake booster or the vacuum modulator. Low readings could also be caused by very late valve timing or worn piston rings. Two of them are easy to eliminate if the car has either on it by simply putting a cap on the proper vacuum port. I'd think you would have caught and or possibly correted The carb gasket idea and we should be able to rule out bad rigs. Leaving what other's mentioned in the cam timing possibly being off.
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