88 K5 Chevy 350 brought to TDC but back fires out Throttle Body?

[rich weyand]

I think you should start with the tune-up parts before you worry about any potential bigger issues. Any time we had a vehicle in the before times (before FI, ECMs, etc) with performance issues, we did a tune-up first to eliminate that as a factor. Often that's all it needed. Bought a '62 Plymouth cheap that way: pre-purchase inspection we notcied it had a cracked distributor cap, which made it run terrible, so we bought it for a song because the owner thought it was on its last legs.

Plugs is good. I would replace the wires as well, and probably the cap and rotor, maybe even the coil. Then you can cross all those off the list of things to look at or do later.

For wires, I run Taylor spiral-wound. Twice as expensive, but the best bang for the money IMO. The racers around here all use them. They are not resistor wires, but if you are running resistor plugs you don't need resistor wires as well. They are long, to accommodate routing around headers and stuff. I pushed any extra into the space behind and below the distributor and it came out looking good.
http://www.summitracing.com/parts/TAY-74206

I run the Accel 48000-volt cap/rotor/coil and like them. You can get whole distributors cheaper than this, but I haven't tried them, and Accel has a reputation for good products.
http://www.summitracing.com/parts/ACC-8122
http://www.summitracing.com/parts/ACC-140013

 

[88Chevyk5]

We'll I replaced the plugs and the motor was still skipping. It was smoking out the exhaust and it smelled way rich like it was unburnt fuel. I tested compression and my cylinders were all about 145 avg except cylinder 5. Cylinder 5 read 0 psi. Took off the driver side valve cover and all the valves were moving. Any ideas?

 

[350runner]

Valves adjusted too tight. If all rockers are moving and you have no pressure in the cylinder, might be them valves aren't closing.

Sent from the dust in front of you!

 

[rich weyand]

0 psi? I don't think that can be rings, I think it has to be valves. Or a holed piston.

Sounds like it's time to pull the head. Might try backing off the rockers first and resetting the lash on those valves just to make sure one of them isn't way over-tightened.

Also, if you have one of those video scopes, you can visually check the piston.

 

[HotRodPC]

How about blow by? Could have a blown head gasket into an oil port. You're losing that compression somewhere, and no it's not rings. Could be a bent valve or a cracked valve seat also with the other things already mentioned. I say no matter what, you're not getting it fixed without pulling the head, so pull the head and go from there.

 

[ScottyB]

Holed Piston would have fuel in the oil, wouldn't it?

 

[HotRodPC]

Holed Piston would have fuel in the oil, wouldn't it?

Maybe, Maybe not. With a hole in the piston, that cylinder is not likely to produce any vacuum, therefore, not likely to draw in the fuel from the intake. Some may dribble down the runner, but the other runners with vacuum are likely to suck the fuel into those cylinders. So it wouldn't have as much fuel in the oil as you'd think.

 

[ScottyB]

Maybe, Maybe not. With a hole in the piston, that cylinder is not likely to produce any vacuum, therefore, not likely to draw in the fuel from the intake. Some may dribble down the runner, but the other runners with vacuum are likely to suck the fuel into those cylinders. So it wouldn't have as much fuel in the oil as you'd think.

Fair enough. I didn't have the answer which is why I asked the question.

 

[88Chevyk5]

Solved the mystery about 2 days ago just haven't gotten to reply back! Rocker arm was tightened down way too tight and the valve wasn't closing all the way. Adjusted the valve lash and compression is at about 145psi at all cylinders. Odometer says 91k and I believe it! She runs beautifully now! Thanks for all the help guys!

 

[350runner]

No prob glad your back on the road.

Sent from the dust in front of you!

 

[HotRodPC]

Nice that it was a cheap quick fix. Usually you don't get that lucky. That's what I love about forums, is the fact you get more minds to offer up suggestions. I'd probably not have suggested an overtightened valve. Sometimes and I know I'm not the only one, things get over analyzed. I was ready for you to rip the head off.