The following is a copy and paste from the "bench" thred ZEDS DEAD... Id really appreciate some input, any input, on the cause/cure for the lack of joy in the ride... Went to breakfast today and she sputtered a few times and stalled in the intersection. Cranked it for about 10 seconds and she stumbled back to life and seemed normal. No black smoke so I doubt it was flooded. What gives here? Gotta ad that the PO had a 165 T stat in there and it ran at 145 consistently, so I changed it to a 185 and it ran at 230 (bad NEW Tstat!) and got hotter after shutdown with an accurate mechanical gage. I put the old one back in and theres plenty of warm air outa the heater and defrosters so I think engine temp aint the issue. Bill in TR So now the real fun begins; last winter did a complete tune up, just prior had the Q jet apart for the 2nd time, new header gaskets et al, and a myriad of other stuff that needed doing. Backed outa the shop and idled through the hood to the main drag (45 mph zone) and accelerated up to speed. The bastard still snorts and sneezes about 3-4 times until she gets her breath. You hafta be REALLY easy on the gas. It doesn't stall, but cant get out of its own way. Hmmm The temp gage is showing about 150F (30F ambient) but that doesn't cause any difference even at 80F ambient. If I hold it in low (400T) and floor it, she coughs up some sputum then catches her breath and LOOK OUT! All the way up to about 4000 in third gear and its hunky dory. With the air cleaner off in the shop and revving it from an idle, itll blow back outa the carb and literally give an orange flash. The inside of the AC lid is sooted. When its really warmed up it does about 50% better, but still un-acceptable. I have yet to time it, and upon tuning last winter found the advance unit (OEM HEI unit) frozen with rust. Checked it last week after cleaning and oiling last December and its still free as can be. Ive had guys say everything from a distrib re-curve to a new carb, and even a fuel pump may be the culprit here. Other than that it runs great. If I were on the E-way and needed to pass a truck, itll downshift to 2nd and take off. No noticeable smoke outa the pipes, starts right up and runs on fast idle as it should, the choke pull off and heat coil seems correct. Whatcha say der exspurts??? Bill in TR
Fuel problem. You need to check all your fuel lines starting at the back of the car. Check the sending unit/fuel sock. Then look at all the rubber line at rear and front to check for cracks. Check the steel line and make sure it isn't crimped anywhere. Next, check fuel pump pressure and volume. The how to is in the chassis manual. Then there is the carburetor. Holleys, anybody can take apart and rebuild. Q-jets, not so easy. You are running lean. That is why it spits and pops back through the carburetor. It doesn't clear up and run good after snorting and what have you. It's still running incorrectly because it is lean. That will also make it run hot and you could toast a valve, so don't be beating on it. It isn't running right. Once the engine is up to temperature, it should be seamless with no lag, hesitation or any other spitting or popping. I don't remember the history of your carburetor. Is it the right one for the engine? Has it been rebuilt? Could be inadequate accelerator pump, wrong float level, low fuel pressure, bad intermittent fuel pump, or just a blockage somewhere in the fuel line. For whatever reason, it is lean. If you are impressed at all with a crappy running 455, you gonna really love it when it runs correctly.:grin:
Just something to digest for now... got a big evening ahead and only have a few minutes... Season Finale of walking Dead is on tonite! These are the old plugs from last year. The ones on the right are used with a new one on the far left. All are R44TS; note the heat length difference... new and improved, as always! I also know theres a fuel return via carbon filter (removed long ago) discrepancy at the tank end. Man I hate working on the floor! Will continue later but pizza is ready for pick up. Thanks guys... Bill in TR
I agree with Briz, "timing". Make sure your timing is not too retarded. Wouldn't hurt to check the operation of the mechanical advance. If idle is good and mechanical advance sticks momentarily, and then frees up as engine rpm raises it will cause this type of condition, including your plug color. I just corrected that condition on a customers 67 SS396 Chevelle a week ago.
Since I really hate to drop the tank first off, I am gonna swap out the pump which is the easiest thing to do. The 72 has a carbon canister which is long gone, but the diverter plenum is still intact behind the rear seat back. That part is hard piped to the front with an open end just below the master cylinder to atmosphere. That's where the hose would've connected it to the canister. Am I right at guessing the canister was driven by a vacuum tap at the carb or manifold? I know its all in the book, but its out there and Im in here LOL and its 0345 hrs. On to the pump... The motor is a '73 455 and the fuel pump appears to be an earlier model non Stage pump, with just an in and an out fitting. Just inserted this: The pump DOES have a return line to the system (third line) . Never paid that close attention to it. Are all 455 pumps like this or the simpler 1 in and 1 out gonna work? Would I be correct in assuming (?) the tank is non vented except through the canister system? I know ultimately the tank will need to come down which I am dreading, plus theres a fresh 20 gallon load of non ethanol premium in it now as of yesterday. I suppose I could try a cap-off drive with a rag stuffed in the filler. When taking the cap off I never hear a vacuum "whoosh" so it sounds like its equalized from some where. I know Im dealing with PO hastiness, The guy was a real schvoogie, OY! Generally everything he did was a mess... you should've seen the wiring! So if the pump doesn't work, next step is supply routing, then back into the Q-jet (vacuum pull offs (2) seem to be working), then finally on to Larry's specialty, the distributificatator. Is the HEI vacuum advance pulled off the correct carb port??? Bill in TR
I think you have a tuning problem on your hands. If you haven't checked the timing, check it first. Make sure your getting a good pump shot from the accelerator pump. Check and adjust the secondary adjustment spring for the air valves so they don't flop open and bog out your engine. The little spring is known to break
OK... so Im good with setting the stock timing and haven't even checked it yet. The carb was apart for a rebuild last year, looked "OK" as per the retired chevy mechanic that does them. He runs the shop at the local NAPA store. Had it apart a second time when the jesus clip on the choke pull off went missing. Carb has a black phenolic float installed, jet plugs under the base epoxy sealed and everything else was "good". I know that the secondary flaps only open with X amount of velocity and lift the metering rods off the seats, but where is the secondary adjustment spring located. I always thought that was a gravity job. So right now, unless the car is totally warmed up, as in being driven for 1/2 hour, merging onto a thorofare at 45 mph is difficult at least; really feels like a "not gettin' gas" situation, yet after a good warm up she runs like a raped ape. Gonna get the pump today for a $25 peace of mind thing with some new fuel hose to renew the vibration connections. Stuffs all 43 years old ya know? After I get it running "normal" Its gonna get the Larry job on the dist. curve kit etc, so be ready for a million questions LOL... Now, I gotta admit, being in the street/strip section, Ive gotten more input than the bench by far. Mea Culpa?? Seems like everyone reads the posts over there but are afraid to speak up. I didt wanna come here and sound like a neophyte, but I am by no means a newbie at this stuff; just old and confused.
Check the pickup coil. Sometimes the wires will break from the vacuum advance movement You may only have 1 or 2 unbroken strands of wire where they go into the pickup coil. Give the wires a good tug, they shouldn't break. Also, the resistance should be 900 to 1400 ohms.
900-1400 ohms across the two posts to the coil or off the reluctor??? Will check that when I turn the heat on in another 20 minutes! Thanks... Bill in TR first pi was as found with frozen advance unit and second was cleaned and well oiled and is still very free... don't believe that to be the issue but thought it WAS!
Bill, I thought you had checked the timing, but apparently not. Initial timing means nothing as the only time the engine runs there is at idle. You need to check where the timing is going when you rev the engine. Not knowing anything about the HEI you have in there, it's hard to predict what you will find. The HEI is renown for having a lot of mechanical advance built into it. If the timing is retarded, it will be down on power. If you are getting enough total advance at wide open throttle, it will feel great only when you nail it and the revs get up there. If the mechanical advance is lazy because of the stiff springs, it will feel doggy until the revs increase. If it pops back through the carburetor, that means lean to me, not timing related. The third line on the fuel pump is a vapor return line. It is there to circulate hot fuel and vapor back to the tank to fight vapor lock. If you pinch it off, the pump will make a bit more pressure. All cars with A/C got the vapor return as well as others. If the fuel pump is original, it is probably prudent to change it, they are cheap enough. Before you change it, turn the engine so the rotor is pointing at the #1 distributor post. That will make it easier to unbolt and bolt on.
I completely understand your frustration..... I struggled with an unknown hesitation last year on my GS400.. Tracing down my issue helped me to refresh the correct way to diagnose and clear out the old cob webs upstairs. I know there's more qualified posters here then myself but heres is my advice for what it's worth. Before you start replacing things, making adjustments etc there's a few things you really should do. 1) Stick a vacuum gage on it. Blip the throttle... Let the guys here know what the readings are. 2) Pull the plugs to verify burn color 3) Check fuel pressure after changing the filter (if you haven't changed it recently) 4) Varify the timing but don't assume it is correct. 5) Check the carb accelerator pump to make sure it's working properly. Your problem could be anywhere from lean fuel, vacuum, timing or carb related. Even possibly a combination of these. Doing the steps above will help to narrow your search to the appropriate problem and save you a great deal of time, money and possibly future headaches. I would start with these before I made a single change to anything. If everything checks out I'd then go back to timing and maybe try a little more advance just to see if the car gets better. If it does I'd start with timing... If it doesn't I'd look closely at the carb and fuel system. Hope this helps.
Did you say you've confirmed the accelerator pump is behaving properly? That's what it sounds like to me. Another possibility is a weird vacuum leak. I once had a vacuum line (I forget which one) that was leaking- it was at the rear of the intake manifold and only cylinder #7 (or maybe #7 and #8) was running lean, but the rest of the engine was fine. Kinda wish there was a video of the problem, I had a hard time understanding the description exactly. -BC
Well now... ordered the new pump this morning just because I could. Its no biggy to change an old one out for peace of mind... The HEI pick up meggared at 1000 ohms; identical to a brand new one at the parts store, and the reluctor wires are in good shape to. So we moved on to putting it back together including an old HEI coil (unknown condition) and fired it up. Lit right off and after a generous shop warm up goosed it and she still spit out the carb. Hmmm... So, being the dyslexic mechanic that I am, finally put the timing light on it. Its a dial back snap on but I didn't even get that far. Set at zero, I am guessing it was running about 30* retarded. That mark is sooo hard to see and ID with the PS belt in the way, but, I advanced the distributor the old way of advancing it until theres a slight buck on the starter and then back it off a notch and Ill be go to hell if the new 30-34* advance marks were in the indicator range. Floored it off idle and no backfire. Now I know this aint the right way to do it and I am gonna test drive it shortly. The other odd thing , and I did ask about the vacuum tap, is that at idle theres no vacuum, as in ZERO, but pick it up to about 900 and theres plenty on the carb nipple. Idle seemed OK but was actually set about 900 (+or-) and dropped that down to 650 as per the spec. The idle mixture screws were out 1-1/2 turns so I closed each one and lost some RPMs, and re-opened them to about 2 turns each for a smooth even idle. We'll see how she does in a bit! Bill in TR
So the timing may be a few degrees advanced for today.... Theres just the slightest surge when idling slow down 9th street. Got to the main drag and accelerated normally and zero hesitation. Went down to the turn around on the lakefront and opened it up for the return home. Pardon the lousy camera work... too much happening at the same time LOL. Really appears to run 100% better, but either the secondaries are super smooth or they aren't opening. Usually when they open you can hear and feel it. But even for now I am a happy camper. Now to play with some timing advance stuff and the pump tomorrow... its only getting better. BTW, Wednesday I see the guy at the bank to pay off the note.. the 4 year loan lasted 14 months; not too damn bad eh? Bill in TR https://www.youtube.com/watch?v=sEe6AmzIDfc&feature=youtu.be
I'd throw a vacuum gauge on it. Their reasonably priced at harbor freight if you do not have one. A trick I learned years ago to help me view the timing mark was to mark it with white soap stone. You can also use a paint marker. It sure makes it easier to see the mark with the light.
WATCH THE VIDEO! The timing marks shown here (the marker was frozen last January and hard to use) are at the 30-34* full mechanical advance point and these marks were on target today after advancing the distributor. Area painted with a white paintstick and scribed with a back sharpie. Bill in TR
Maybe I missed it somewhere, but can you rotate the distributor rotor, let off and does it snap back? Almost looks like the weights aren't being pulled back all the way even after the cleaning, which means the mechanical advance is stuck.
I can't tell what you are doing with the timing Bill. You want 34* of timing when the weights are extended all the way out. That isn't going to happen at anything under 4000 RPM with the springs you have in there. So as far as I can tell, you advanced the timing with no regard for what it is going to advance to when the RPM comes up and the weights start extending. Then you add in full vacuum advance and wonder why it is surging? Be careful.
