Hi again, As I get ready for my inspection on Thursday, I have been driving it around the neighbourhood to get used to it and to see if there are any other problems. When applying throttle from idle, in gear, it would sputter a bit so I would give it more fuel and away I go - a bit quicker than I would like. I have not allowed it to die during the sputter but it seems like it would. There appears a starvation for fuel at idle. I still get popping from the pipes until it is warmed up and, once warm, no popping. I adjusted my mixtures on the Quickslayer 650 to 1 + 1/4 turns and the plugs are staying clean. My vacuum is 12. The idle, when warm, is about 700-800rpm. This is on a 350 sbc with a th350 tranny. The cam is a bit above mild but no where near crazy. Any ideas? - Daryl
You can also play with the return spring rate on the carb to give you better control ,specially if its jolting you at all.
Had the same problem with a 600 QFT 600 SL. Went up one size on the squirter. Problem solved. Also make sure the throttle blades are only exposing about .020" of the transition slot in the primaries.
I took a step back on this project. I pulled the plugs all were looking good except a bit of darkness on #3 and #7. Because the damper and pointer were new, I reaffirmed TDC (I was out a little). Found a burnt plug wire as well. Tomorrow I will check the valve lash especially on 3 & 7. and reset the timing again.
Is your sputter at idle, or as it transitions off from idle? at idle, check idle mixture, off idle, squirters
Most of the time off idle hesitation is in the accelerator pump circuit, as mentioned above you might need to increase the squirter size. But check and make sure the arm is adjusted correctly. Make sure the nut on the screw for the pump arm is not tightened down, most people will tighten the nut eliminating pump arm travel, while backing the nut off will give you a longer pump shot off idle.
OK Popping while cold is a lean misfire. Liquids do not burn, only vapor burns. When an engine is cold not all the fuel vaporizes so the engine runs lean. The un-burnt fuel then ignites in the exhaust causing the popping noises. Lean mixtures also burn slower so sometimes there can still be fuel burning in the cylinder when the intake valves next open, setting the vapor in the intake manifold alight. Boom again! We overcome this with a choke that causes the carby to give more fuel relative to the amount of air. The extra fuel means that enough fuel turns to vapor so the engine runs properly. If we leave the choke on when the engine is warmed up then all the fuel vaporizes and the engine runs rich. Do you have a choke on the carby? Maybe it needs adjusting to give a little more restriction when the engine is cold. Also check that the accelerator pump is starting to squirt as soon as you move the throttle off idle. Do this with the engine stopped so you can see the start of the squirting. If all seems to be working then maybe a larger accelerator pump discharge nozzle is required or a different cam for the accelerator pump. If the carby has no choke then a long warm up is all you can do.
I had the same problem and ended up changing the accelerator pump cam to allow additional fuel earlier and that cleared up the hesitation/sputter. That was a cheap repair and I quit pulling my hair out.
I think this is where I start getting a problem. I just adjusted the lash for all cylinders. TDC, tighten until no spin on pushrods, tighten 1/2 turn to preload and lock down. Move on to the next in firing order. After I finished all cylinders I went back to #1 on curiosity. TDC and I could spin the pushrod - not easily but still could. My normal inclination is to re-lash it again but I don't think so. Am I wrong?
OK. Here is the progress from yesterday and this morning: I re-lashed the valves (some small errors); affirmed TDC; replaced plugs; checked dist. pointer for #1 (out a tooth); set timing 12-15 deg btdc; raised idle to 900-1000rpm; checked mixture; checked vacuum 14.5 and steady . Now it starts easy but runs slightly rough like it was missing almost (might be the cam) and rocks 1/4 to 1/2 inch when idling. When put in gear it bogs down to 750-800 rpm and does not sound happy. But step on gas (brakes on) and it perks up. Might have to up the idle some more. As my ex-father-in-law used to say "listen to the pipes for 'mommydaddymommydaddymommydaddymommydaddymommydaddymommydaddy' and that is definitely there. Just going to take it out for a run and see how it all plays together. To be continued later. OK. Back from run. Odd backfire drivers side pipes and a lot both pipes while warming up. Choke problem I assume. It's hesitant to drop down in gears approaching a stop and starts to bog down and I have to tap the gas to recover. Also slight hesitation while driving and I add more gas but it does recover. Thoughts?
Hmm. Dying on the over-run when coming to a stop has been a problem for years. Some cars in the 60s & 70s had an "anti stall dashpot" as the idle stop. this was a small diaphragm that looked a bit like a tiny vacuum advance. The throttle would come to rest on the idle stop which would the squish the air out of a small hole in the housing on the other side of the diaphragm, allowing the throttle to close that last bit in an orderly fashion. A light spring behind the diaphragm would push the idle stop back out when the throttle was opened. Later emission controlled cars had a valve that allowed air in to the inlet manifold when there was a particularly high vacuum situation like on the over run while changing down. This prevented the carby from flooding up due to the strong vacuum sucking a load of fuel in through the idle port in the carby. If this were my rig I would be trying a bit more initial advance (16 to 18 degrees at idle?). Check that you have no more than about 36 degrees of total advance with the engine at about 4,000 rpm Is your vacuum advance hooked to ported or manifold vacuum? If it is hooked to manifold vacuum you can loose a heap of advance when you crack the throttle or when the engine revs drop as you put it in gear. This can lead to stalling. I prefer to run ported vacuum on a mild engine as the idle is usually more stable. Also with the vacuum advance disconnected check the timing at idle in and out of gear. If your advance weight springs are a bit soft you may be running some extra mechanical advance at 900 compared to the 650-700 when in gear. Again I prefer a slightly harder spring that does not move too much until it hits 1100. Not ideal for out and out performance but easier too set up for street cruising. Do you have a timing light with timing offset built in? you will need one to make sure you are not giving the engine too much total advance. I like to use ported vacuum for the vacuum advance so it has no effect at idle. put a vacuum gauge on the advance port and make sure you have little or no signal at idle. in and out of gear. Set up your timing with the vacuum advance disconnected. Note where it all idles most robustly then get your distributor re-curved to put in the rest of the timing in up to 36 degrees starting to advance at about 1100 rpm and being all in well before 3,000. Vacuum advance will take your timing past this for light throttle cruising for better fuel economy with a carby set up to cruise lean.
Interesting. The car is in the shop right now for it's safety inspection. I asked the mechanic to check the timing as he has one with the offset built in. I'll let you know when I get it back and can try it out.
Aaaaaand I'm back! Failed the inspection over some little items. There was a brake fluid drop on the bottom of one caliper as well at one of the lines from the line-lock and a fuel drop at the fuel pump. Just have to clean them up and take it back next week. The stalling when going into gear was diagnosed by a guy older than me who said he could "hear it was too rich". he played with the mixtures and it got better. They didn't have time to check the timing with the offset timing light but will do it when I bring it back in. And the vacuum advance is hooked to the timed spark port on the carb while the full vacuum goes to the tranny.
OK. Been away for a bit. UPDATE: Going back for inspection on July 6th. I also talked to him and his co-workers about the troubles with the carb They weren't too much help so I contacted the dealer where I purchased it so long ago. SHAZAM! they gave me a new one to try and if it was good just give them the old one. Took it home, strapped it on and instant start with a few minor adjustments to make. Very happy about that. So now on this beautiful sunny day, I am just listening to the car run and doing a bit of cleanup. Every now and then, I get a whiff of gas and for once, it wasn't in my exhaust. Then I see a puddle on the manifold. Shut down, wipe it all up and put some brown paper in the area of the leak. Activated the pump and found the leak. On my fuel rail is an allen bolt and the gas is coming out all around it. I cannot get it tighter so I took it off, checked it and reinstalled but still have a leak. I tried some thread blocker on it but to no avail. Thoughts?
That is for a fuel pressure gauge, they make that same fuel inlet without the threaded hole if you chose to replace it. Or buy a gauge and thread it in. Maybe that plug is not the correct pipe thread.
I'm willing to bet that hole for fuel pressure gauge is drilled and tapped 1/8-27 NPT and has a 3/8-24 NF plug in it. They will screw in but are straight thread, not tapered, and won't give a good seal.
OK. Inspection is tomorrow and I think everything is good. I used permatex 2 to seal the allen bolt and it worked perfectly. Now to clear up some other items in my posts: After changing the carb there has been no turning back. Just came back from a jaunt and it performed admirably well. It kept wanting to have its head but I am still getting used to this beast. A cramped one at that. Stays running when it is braked to a stop and doesn't die out. Idles around 800 - 900 RPM and seems happy. Cruising down the road and hit the gas - no hesitation. Just gone. After inspection, I will wait until the weather turns crappy to pull the heads. If I didn't mention it earlier, that is where my oil leak is coming from. Rear of the heads and dripping off the back of the block. With the oil being super clean, you just don't see it to well. Thank you, thank you, thank you, to all who offered advice and had patience with me.
The Jalopy Journal
