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Old 11-21-2008, 04:41 PM
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SBC 305 hard start, backfire, no power

Hello Guys,
I have SBC 305 with no modifications as far as I know with TH350 transmission (rebuild).
Rochester 2Jet carburetor rebuild by me (not an expert).
There are new ignition cables, new spark plugs, new distributor cap and coil, new air filter, new fuel filter and new fuel pump.
The car was sitting for some months due to broken transmission. During that time I changed the above parts and rebuild the carburetor. The engine was starting with no problem.

Now I have the transmission on the car but the engine is very hard to start and lacks power.

I have to keep the gas pedal to the floor and to open the choke when it is cold in order to start it. Also it backfires through the carb before starting.

When it starts, there is no idle at all, I have to keep the pedal down.
It is getting very hot as well, today for some 10 minutes it got to the red zone close to 260 F, the fan is working and it has never overheat before.

Also, when in gear it has no �power� at all.

I do not know where to start diagnosing the problems and solving them one by one.
I will really appreciate your help and directions.
I am beginner in this field with no experience at all.

Thank you,
Ivo

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Old 11-21-2008, 04:52 PM
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If it started and ran well before you did anything, you must look at what you have changed. Check and double check the firing order, very easy to get it mixed up. Crossing 5 and 7 especially will make it pop back through the intake. This would affect power and temperature as well. If this is all ok, then I would suspect something may have been missed in the carb overhaul, again easy for a beginner to do.
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Old 11-21-2008, 05:10 PM
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Hm...
Thank you sbchevfreak,
This is good point to start, I measured compression some time ago... so I could have mixed the cables...
I think I did the rebuild correctly because I got stable idle at 500 rpm and engine was revving good, at least on jack stands no road test with broken transmission

Thanks for the help
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Old 11-21-2008, 05:49 PM
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Quote:
Originally Posted by rack
The car was sitting for some months due to broken transmission. During that time I changed the above parts and rebuild the carburetor. The engine was starting with no problem.

Now I have the transmission on the car but the engine is very hard to start and lacks power.
Ivo

Please clarify a couple of things first.

You said that while it was parked, you did a bunch of work on it waiting for the trans. Then you say it started fine. Was it starting fine AFTER you did the parts changing while waiting on the trans?

If so, one thing comes to mind, since the trans was the last thing done. I'm wondering if there is a problem with the trans, as in the converter hub not fully engaged in the front pump. This could really lock things up if the pump is mangled now.
You could try removing the three converter bolts and (hopefully) push the converter towards the trans and then start it up and see how it runs. It will only move back about 1/2" but it will be enough to fire it up without the trans hooked up.

Mark
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Old 11-21-2008, 07:12 PM
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SBC 305 hard start, backfire, no power

ran good before trans install , did you knock the cap loose or may have turned the distributor a bit while at them bolts ?
if cap hit the fire wall you may knocked it up and even bent the rotor button
into cap on inside ,causing spark to jump .
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Old 11-22-2008, 02:59 AM
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Quote:
Originally Posted by Jmark
Please clarify a couple of things first.

You said that while it was parked, you did a bunch of work on it waiting for the trans. Then you say it started fine. Was it starting fine AFTER you did the parts changing while waiting on the trans?

If so, one thing comes to mind, since the trans was the last thing done. I'm wondering if there is a problem with the trans, as in the converter hub not fully engaged in the front pump. This could really lock things up if the pump is mangled now.
You could try removing the three converter bolts and (hopefully) push the converter towards the trans and then start it up and see how it runs. It will only move back about 1/2" but it will be enough to fire it up without the trans hooked up.

Mark
Sorry for not making it clear.
When I changed the parts it was starting fine, but the transmission was broken.
Than, after sitting some weeks it got worst, hard to start,backfiring through the carb, it was with broken transmission on.
And sitting two more months, with rebuild transmission on, it is even worst.

I am pretty sure that converter and pump are engaged because the car is running forward and back, just there is no power and I have to keep pedal to the floor to keep engine running.

Last time I checked ignition timing it was correct.
Now, with engine not running correct how can i check and adjust timing?

Thanks for your help,
Ivo
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Old 11-22-2008, 03:03 AM
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Quote:
Originally Posted by burnt olds
ran good before trans install , did you knock the cap loose or may have turned the distributor a bit while at them bolts ?
if cap hit the fire wall you may knocked it up and even bent the rotor button
into cap on inside ,causing spark to jump .
Hi burnt olds,
It is not the problem because I removed the cap before removing transmission and lowering the engine. Nothing has had touched the firewall.

Thanks for replay,
Ivo
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Old 11-22-2008, 03:52 AM
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Rack,
The fact that it is backfiring through the intake strongly suggests an issue with your ignition system. ( i.e. plug wires crossed, bad cap and/or rotor, improper plug gap etc.) Double check everything with your ignition sys.
If there is a problem there, your engine will become increasingly harder to start and run over time due to the spark plugs fouling, so you will need to pull those out and verify their condition.
You said you installed new cap and coil. Am I corect in assuming then, it is an HEI ignition sys? If so, Did you transfer the "L" shaped ground strap in the dist. cap?
Another reason it could seem to be running extremely worse now could be due to the added load of the trans. pump. Loads on an engine will exaggerate any misfire conditions.
Let us know what you find.

GL,
Tech
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Old 11-22-2008, 07:21 AM
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Hi justacertifiedtech,

You are correct it is HEI system (78 Monte Carlo)

I started to work on these one by one.

First, the spark plugs.
There are black dry deposits on all of them. They look the same. see pics
I cleaned them and measure the gap, all are at 0.045

Then the distributor cap... when I open it there were bras (or what metal the contacts are made of) shavings...

Is this normal or there is something wrong with it?

After that I will arrange the cables and try to start the engine.

Unfortunately my garage is not heated and the winter came here... so it is hard to work a lot

Thank you for your help,
Ivo
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Old 11-22-2008, 07:38 AM
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Ivo, The Black deposits on the plugs is from the miss fires the ignition is having. The Brass shavings in the cap is not normal. Sounds like the rotor may be bent or misaligned causing the rotor to contact the terminals in the cap. You may need to remove the distributor and spin it to make sure the shaft is not bent. Are you sure the engine did not sag down and contact the firewall when the transmission was removed?
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Old 11-22-2008, 10:08 AM
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Hi SSedan64,
Thanks for replay.

The engine did not touch the firewall. The guy who helped me to remove the transmission is much more experienced and took all necessary measures.
Unfortunately I do not know if this has happened before I bought the car

Anyway I will remove the distributor and see how it behaves.
Even I would try to put my old distributor cap to see if it gets better.

Thanks for the help,
Ivo
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Old 12-06-2008, 10:03 AM
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Hello Guys,
I am sorry for being away so long
You were absolutely correct I have ignition problem.
I clear everything ant put it again very careful.

Now the engine runs fine
Thank you for your help.

Best regard,
Ivo
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Old 12-28-2008, 01:05 PM
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Reading through these old posts looking for anything that might help me and wanted to know Specificully what your ignition problem was ?
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Old 12-28-2008, 03:16 PM
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Try a new Hei , Junkyard or Ebay. Also check for vacuum leak, is the vacuum line from the manifold to the transmission modulator valve hooked up? How about a compression test. Did the timing chain jump a tooth, Just advising on things to check.
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Old 12-28-2008, 05:28 PM
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Quote:
Originally Posted by Studebaker
Try a new Hei , Junkyard or Ebay. Also check for vacuum leak, is the vacuum line from the manifold to the transmission modulator valve hooked up? How about a compression test. Did the timing chain jump a tooth, Just advising on things to check.
the guy said its already fixed
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