I'm having issues on a 305 SBC. Supposedly all stock internally but has a 600 cfm Holley on the stock q-jet intake and an accel hei distributor. I've searched and can't find exactly what is going on with this engine. I've tuned it a few different ways and the best running seems to be 14 btdc at idle. However, the idle in gear (750 rpm or so) is rough and it sometimes dies with a burp or chuffed sound. It starts back up immediately but will die with the little burp in drive or reverse. It doesn't do it every time you stop but often enough to be frustrating. At speed it seems fine. Idle in park is smooth. Seems low on power even though I am not expecting much. In short, if we can get it not to die, the owner and I will be happy.
Are you running ported vac. or full vac? Ck. plug gap should .040. Try pulling the timing back to about 8.
Have tried ported and full. It's worse on full vacuum. Factory settings for this motor were 4 btdc and I've tried that, 6 and 10. I ended up timing to highest vacuum in case something had moved on harmonic balancer. Plug gap is at .045. New plugs and wires. Thanks @dan griffin
@Ricks Garage , I have carefully checked for vacuum leaks (it's pulling 18.5 at idle) and I read that if the power valve is blown it won't respond to the idle air screws. Plus the carb is less than a year old and all new ones have the check ball to prevent power valve blowout. I'll pull it tomorrow to look for gasket/adapter problems.
Gas is not old @pat59 . New filter, new carb for that matter, just can't figure out this problem. @saltflats it does have a 700r4. Perhaps the converter is locking up at low speeds? I understand the question, just not how that affects the idle in gear, and in reverse. What tells the converter to lock up, perhaps it's missing or not adjusted correctly. That gives me something else to search for anyway. Thanks to everyone with ideas.
Do you have a brake booster ? Throwing that out there since your vacuum is good at idle but it seems like your problems start when your in gear (foot on brake).
I would check your balancer to make sure the TDC marker is in the right location before I went too much further. When baffled by a problem on an engine, I start with the basics- compression check, TDC check (verifies the timing I think I have I do have), and fuel delivery- clean filters and flow.
It might be lifter pump up. It is rare but not unheard of. If you had a scope you could tell witch cyl. was acting up. If you find the bad cyl. pull the valve cover and run the rocker nuts up and down. This will cycle the piston in the lifter.
1. Make sure the timing changes when you hook up vacuum advance. 2.Watch the carb while idling, with air cleaner off. See if one of the pull offs on pass side closes and lowers idle, causing it to die. Result was I needed to blip the throttle to keep it running. A very smart person told me that reduction in idle RPM was caused by the wrong spring inside carb (not matched to idle vacuum). The pic I saved says Power Valve Springs. Hope that helps.
I chased a bad problem with an Accel HEI when I first joined the HAMB. Even had it tested and it tested good at several places. Finally out of desperation I pulled the distributer out of my truck and dropped it in there and the problem was solved. you are running a lot of lead unless you are checking with the vac line hooked to the distributer. A stock 305 should run fine with about 8-10 static advance. After I did the normal stuff like looking for a vac leak I would drop another distributer in there and see if it cures it.
Well everyone, it's fess up time. I was honestly chasing this problem with the best of intentions and there are two damned lessons to learn. Hopefully this resolution will help. First, never assume that the other guy did stuff right. I got this truck with new wires and plugs, so I never checked the firing order. Second. Check the simple stuff first. A little tic at the back of my brain the other day said check the firing order, but I didn't listen because the owner said he put new plugs and wires on it. I didn't have another distributor hanging around @porknbeaner but I was down to thinking that was a great idea. I did have another carb that I know was running my 300 Ford, an Edelbrock 450 cfm. So, put the known good on there even though it's an old carb never adjusted to this engine. It actually helped, a little, but still on loading things up it would pop. It didn't die with the Edelbrock, so we sat there dumbfounded trying to figure it out. My next step was to get a distributor and check it out. We then decided to check the firing order just to make sure. 3 and 5 were swapped; how it idled and ran so well with no load, I'll never know. We swapped them and it has fixed all of the problems, even the perceptible lack of power. Of course it was down on power, dumbass. Dragging two misfiring cylinders around will do that to you. Thanks again to everyone who helped. @RR, I did check the timing mark at TDC, it was fine. That was one of the first things I did. @laidbackluis there is a booster and taking it off didn't change anything, because that wasn't the problem. Good idea though. @dan griffin the vacuum gauge (and I checked a couple of different ones) was rock steady at idle and I would think there would have been a flutter with the firing order off. I couldn't tell if there was a twitch as it died. We tried to see, but it was so sporadic when it would die. @rfraze and @saltflats , the carb was brand new and I was going to pull it apart and check those things if the Edelbrock had run perfectly and "fixed" the problems. As it was, we found the firing order issue. Thanks for the tips though, and I'll keep them in mind for any future issues. I'll be in the corner with my dunce cap for the evening. But at least it's pizza night and my wife says I can still have some.
The torque converter lockup is controlled (unless you, or someone else mis-wired it) will only lock up in 4th gear, via a pressure switch. Some early 700R4's could lock up in 3rd, too. There is no adjustment. It is locked, or it is not.
Oh, and I cannot seem to get plug wires back on correctly on the first try, despite having memorized distributor rotations and firing orders for a dozen engines, and with 35+ years of experience. At least your wife will allow you pizza.
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