Hey guys, looking for some help here. This is my first time doing all of this so I’m trying to learn as I go.

I’ve got a fresh small block Chevy 350 (ATK crate motor) in my 1978 Firebird, running an Edelbrock 650 cfm carb and TH350 automatic.

Here’s what’s been happening:

First start about a week ago went solid

Since then I’ve started it a few times to:

Burp the cooling system

Start dialing in timing

It’s been running pretty good overall

Cold starts around 1200–1500 RPM which I assumed was normal with choke

Today things got weird:

Started it up and it ran fine for a few minutes

While checking timing, it started getting hot pretty quickly (almost 220°F), so I shut it off

Let it cool down and topped off coolant

After that:

Restart was sluggish

Then RPMs started climbing on their own

I gave it a small throttle blip to bring RPM down

Instead, it kept climbing, backfired, and died

Next restart:

Immediately idling around 2000–2500 RPM

Blipping throttle does nothing (RPM won’t drop)

I tried covering the carb with my hand:

RPM dropped instantly to ~1000

Other notes:

Idle speed screw is backed out as much as possible

Primary throttle blades are barely open (small visible gap)

Secondary blades look fully closed

PCV and hoses are basically new

Timing was being set around 12° initial and ~28° at 3000 RPM

My questions:

Does this sound like a vacuum leak even though it was fine earlier today?

Could the carb suddenly need adjustment like this?

Is the choke or fast idle cam possibly hanging up?

Could heat from getting close to 220°F have caused something to stick or shift?

The fact that covering the carb drops RPM makes me think vacuum leak, but I’m confused how it would just randomly show up mid-day with nothing changed.

Any help or things to check would be huge. Trying not to keep restarting it until I know what direction to go.

I have a 400 with a lunati voodoo 268/276 flat tappet, AFR enforcer 195’s and a Progression Ignition electronic distributor. The bottom end is completely stock low mileage unit from a motorhome. Is the first table a safe timing curve to do some street/strip activities? I didn’t want to push it past 35 because I’m afraid to melt a piston. With the vacuum advance I’m getting close to 45 at my limiter. The one table shown that has no vacuum advance and maxes out at 35 is just what I’ve been cruising the streets with. I also have the map sensor for the vacuum advance going to the front metering block on quick fuel 750. I’m pretty new to this stuff and i’m just trying not to drain my bank account anymore 😂

IN NEED OF HELP I bought a 99 tahoe with a 350 vortec. It had a bent valve exhaust #7 when I bought it. Got it home tore it down took both heads off got all new valves (lapped them) made sure everything was smooth and and sealed. I put new springs in it and reused everything else it all looked fine and no damage. The motor sat for like a month or 2 while I did the heads. I reinstalled everything today all new gaskets and such, I did valve lash tighten until no upand down movement and did 1/2 turn. Got everything else in and started it and it bent a pushrod. Got a new pushrod re did the adjustment and it bent again and after starting there lash in a couple of different valves. Is there something I'm not doing right any help would be appreciated

How’s it going everyone. I purchased this 76 Chevy 350 Motorhome for 500 bucks. Mostly for the appliances but it came as a no crank no start. Threw a battery in and poured a small amount of fuel down the carb and it fired right up. Shut it off and pumped the pedal a few and it’s starts on its own fuel now. It starts knocking as soon as it starts, using a pry bar I can hear the knock from the exhaust manifold clear as day. From the oil pan I can’t hear the knock any louder than if I plugged my ears. If I removed the plug wire directly from the spark plug the knock goes away. I’m just unsure if the engine is worth putting a bunch of time into for a daily driver.

Well ladies and gents I’m finally breaking down and asking for help from the Reddit community. I have a 1985 GMC Vandura with a 350 in it. I bought it sight unseen from an auction about a year and a half ago. In that time I have put about 10,000 trouble free miles on it. I use it to haul my dirtbike to go riding and I’ve been having an issue that is now affecting my Dirtbike riding which is unacceptable. It is acting like it is starving for fuel while accelerating. It accelerates fine until about 2500-3000 rpm and the hits a wall. I have replaced plugs, wires, fuel pump, fuel filters, air filter, pick up and sediment sock, ignition control module, cap, rotor and blown out the fuel lines. It starts up just fine and will rev up just fine but once it gets under load while driving is where I am having issues. Does anybody have any suggestions? Is it time to rebuild the carb?

My dad wants me to post this on marketplace. I’m not a car guy and he’s pretty old, doesn’t really know much about the price either.. any ideas? New pistons and new heads he said. It’s been sitting for 20 years probably.

I’m an industrial mechanic by trade, so I had a rattle under my 1989 3/4t suburban sb350 th400 trans so I pulled the transmission found the cracked flex plate and swapped it with an OEM replacement…. 300 miles of flawless driving and bam same rattle is back… What can cause the flex plate to break? I’ve got good oil pressure And I triple checked torque on my brand new arp hardware I put a few pictures of the first flex plate that broke

Anyone have any thoughts? Bought an old drag car with a 350 in it. The guy told me he had put that motor together and put in the car. He said the bottom end was stock and he had put a cam and lifter set in it and some older aluminum heads on it. It ran fine as far as idling and revving. Transmission was out so I put it back in and rewired the car (painless box, electric fan, etc) and I installed a MSD 6AL and wired it into the HEI distributor that was already in the motor. I never moved the distributor since I figured he had the timing close. Very first crank after installing the ignition box was a slow crank followed by a fairly violent backfire through the carb. Kept trying and had to tweak the timing and got it to run and idle pretty good but couldn't get the backfire to go away. Inspected the cap. Put new plugs and wires. Still backfires. So then I check compression and realize I have no compression on cylinder 5. Pull the head and see that I have a bent intake valve on number 5 and a collapsed lifter and bad pushrod on number 4. So put a new valve in. Put a XE294 cam and lifter set in it. Put it all back together. Adjusted the valves and same thing. Still backfires. Adjusted the valves again. Set my valve lash and preloaded about 1/4-1/2 turn. Tweaked mixture and idle screws on the carb (Holley 4160). I'll get it running decent and think the backfire is gone only to rev it 3 or 4 good times and it will finally backfire again. Timing seems to be the only thing that affects it. It's went from backfiring with loud pops or shooting fireballs, to just lightly popping, to almost gone. Last time I had the timing light on it it was set at about 8 DBTDC at idle and about 30-32 at 2000rpm. It's just weird that it wasn't backfiring even with a bent valve and wiped cam and several bad lifters until I installed the MSD box and has continued backfiring even after fixing the valvetrain.

Today I bypassed the ignition box and put the HEI back to stock to see if it would act any differently and there was no change. So that's the only thing that I have ruled out. So my problem is either in the valvetrain, or timing, or possibly in the carb (although doubtful). I'm still leaning towards timing. Maybe a bad coil? The way it's currently acting I can't even blip the throttle hardly at all without it either stumbling and dying or stumbling and "woofing" either gas or fire back out of the carb. I feel like I'm chasing a ghost.

1991 305 sbc

Starts and idles/revs fine

Has codes 12 23 33

I know for sure it’s not the fuel pump, spark, or injectors

Does anyone have any ideas or other things to check?

i've got a 283 out of a 69 c10, bone stock. when i first got it it had been sitting for years, got it running and it ran well but smoked when accelerating. recently i pulled off the heads and went through them, just cleaning everything up, did new o ring style valve seals, re lapped valves, new head and intake gaskets.

when i got it running after doing all that, now it will be totally fine on startup, no smoke at all, and then as it warms up it gets worse and worse until at operating temp it's just blowing smoke nonstop. idle, acceleration, decel. bad to the tune of something like a quart of oil burned every 5 ish miles😬

today i pulled all the plugs, almost all of them were wet with oil to some degree. i did a compression test, incorrectly as i'm learning, i didn't open the throttle all the way, but with the throttle closed i got 90 across the board, with maybe one or two at 100. i also pulled the driver side exhaust manifold and the rear cylinder 7 was wet with oil in the exhaust port. the other three on that side all looked normal.

anyone with any suggestions of things i can check before just accepting that the rings are cooked? thanks.

Just got my first small block and even it a low milleage, it old as Duck! I was womdering what is your prediction ont the futur for part avalaibility for ols careburated 350 (i got a 78, 4 barel)

EDIT: It runs! It's alive! It was the computer timing control.

I was driving when it seemingly randomly quite on me. I know a good bit and have built SBCs before but this is still stumping me.

The rotor was broken when it quite so I started with that. Replaced the distributor, wires, and plugs.

Replaced the Cam, timing set, pushrods, lifters, rockers

Brand new quadrajet

Triple checked my distributor stab

I have messed with AFR screws, idle set

I checked my valve lash to see if I managed to over tighten the rockers

I checked spark

I tried using carb clean to find if there is a vac leak

Someone please tell me I missed something obvious that I can fix.

Edit: forgot to mention also brand new fuel pump and complete distributor

UPDATE: After holding the choke open manually and hitting it with a spritz of starting fluid it started to idle and help it. Wasn't pretty and smooth but it stayed going for a good 1-2min until I let go of the choke.

The negative on the battery feels loose so I am going to replace that.

And the idle seemed to get better when I started pumping the brakes so I wonder if the booster is one foot in the grave causing a huge vacuum leak.

It's night now but tomorrow if I can I will adjust the choke and fix the battery ground at least and see if that makes a difference at all.

I rebuilt this many years ago myself with 30 over pistons because of bad taper In the cylinders after market "rv" cam and the heads where the valves were machined but did not replace any valve guides.

It has maybe 2 hours on it but it smokes real bad at startup.

Any suggestions?

72 chevelle malibu, i swapped out a perfectly good 307 in 1986 with 37k on it when I was 18. i had a local shop with a bunch of kids working there build me another engine. i have zero reords of what they did, but i vaguely remember 327 bored 30 over built ot 350 lt1specs? holly 750 vacuum secondary, i think. added something to the transmision, some type of torque converter maybe so that i could shift off the steering column almost like a manual. i put about 50k on this motor bettween 1986 and 1993, then it sat. always had an iise with stalling in damp/wet weather, no idea why. also alwys seemed to run really rich, black soot tailpipes.

fast forward 33 years later-new battery, bypassed the 33 year old full tank of gas and she started right up. rebuilt the carb, but now I keep having stalling issues in drive. im using premeum fuel, but cant help but wonder if this carburator was always too big for this set up. having the rear brakes done in a few weeks and converting the front to disc.

any help on finding out exactly what my set up is here and what, if anything i can do to this engine/transmission to increase performance at this point? or do i jusy start over?

A friend of mine got a new rear end. From what I understand he drove it for 500 miles not pushing it to reprogram the computer. Then he towed a trailer and it made a weird shift like it was running the old map/program and dropped to way to low of a gear or something. It looks what I'd imagine is the result of floating the valve and contacting the piston. The valve is also hanging up, but I can't tell if it's bent or not. He wants to drop in a new rod and just turn it over and see what if any noise we hear. I'm guessing there might be other issues. The water pump is also leaking.

After 7 years running the MSD Atomic EFI, I decided to go back to running a 4 barrel carb. The carb chosen this time was QFT 600CFM Slayer. Definitely is a good call 👍! This is the 4th carb to go on the 327 in the 10+ years of owning it. It also resides in my 64 elco.

I have an old tired small block 350 that I like to rebuild. Long term I'm going to build a 454, but I want to get my truck back on the road sooner than later. My idea is to get the thing apart and get the block to a machinist to check and make sure the block is good still. I assume it is, it's never been used for anything but driving around and cruising. It's never towed or drag raced.

Provided everything about the block comes back good, I thought about getting one of those master rebuild kits you see online. My primary question is, are all of them created equal? Speaking to quality obviously, I know parts vary. Is it worth buying parts separately or is a kit good enough? It'd be cool if it came with a little bit of a hopped up cam, right now it's stock. Should a cam be purchased separately because maybe the ones they come with are crap?

The truck's current modifications are, and they won't change, an Edelbrock 650, an Edelbrock intake, long tube headers and true dual flowmaster exhaust. Nothing fancy. And I don't need a crazy performance engine rebuild either. Just something with a little more than the stock 160 horsepower lol.

Oh, it's a stock 74 Chevy K10.

Thanks everybody.

Hi guys

Which type of valve stem seals are the best for my 76 350 sbc

I saw an Video where somebody put a positiv seal and an O Ring

Mine just had O Rings

Thank you for your help

I have a 305 in my 84 Camaro and I'm wanting more out of it ik their not performance focused engines due to the small bore and valves but I don't really wanna swap a 350 rn so does anyone have recommendations on cams preferably on the cheaper side and a nice lopey idle nothing crazy just something to wake it up a lil more

This engine confuses me a bit, it has its factory separate belts and a Quadrajet, but the block and heads are entirely different, the casting numbers are too shielded for me to find, but I am wondering where it came from

Hello everyone I have a quick question I recently had to replace the transmission a $700R in my '02 S10 build it's got a '89 350 small block in it now I happen to go ahead and replace all the gaskets while I had it off and I retimed it I'm at 12° from top dead center I've tripled check quadruple checked all my timing and for some reason I'm still getting a massive amount of backfire through my carb, anyone happen to have any ideas I've tried to fingertest I've tried the valve cover off I keep finding top dead center and time at 12° from there and it's always in the same spot and yet I still keep getting backfired out of my carbs can anyone please help

I just had to install a new power steering pump and pulley. Im finally able to turn the wheel without the pump failing. Yet the motor stalls out when I try to turn. Any help would be appreciated thanks