Slow Cranking motor, fresh rebuild

It could be that the bearing to journal clearances on the crank are too tight. When you turn the car off does the rotation of the engine come to an abrupt stop?

A quick check would be to remove the oil pan, and the bearing caps. Place a piece of Plastigauge on the journal and reinstall the cap torqued to spec. Remove the cap again and compare the Plastigauge width to that on the package.

Another indication of too tight of a clearance would be excessively high oil pressure.

my guess is going to be timing too advanced. try retarding the timing just a bit and see if it cranks better.

All excellent suggestions! Man what a crack team we have here at Team Impala!! :-D

Nacho65SS said:

Got my 350 SBC rebuilt motor cranking, but it cranks slowly, good battery, new alternator, new starter,

even with spark plugs removed it turns slow,

i jump it with a runnng truck snf it goes slightly faster for longer, i got all the grounds good, battery to block, block to frame and block to body..,,

What can it be?

Thanks

~Nacho65SS

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67SS said:

my guess is going to be timing too advanced. try retarding the timing just a bit and see if it cranks better.

Click to expand...

How will timing affect a motor spun over with no plugs in it?

Big Dave

I did see a load difference with open plug ports, i started the motor today thank you all for your input, it turns out my distributor was 180 out...all good now

So how is it running now?

Like I was telling Eddie the motor should spin freely with the plugs out. Was it turning freely or still binding (dragging)?

If so fixing your distributor allows it to run, but you may be overpowering another issue that could come back to haunt you. A motor shouldn't have more than 50 to 55 pounds of drag with standard width high tension cast iron rings and 30-35 ft lbs of torque required to spin it over with modern narrow low drag rings. It should spin like a top with the plugs out.

Big Dave

I don't know how I missed the spark plug removed part.

So the motor starts up, two issues i need to handle better grounding and a complete carb rebuild. The carb has partially clogged jets. Once started the motor idles nicely.

Idle and jets are isolated from one another; two different circuits in the carburetor. Main jets come into play once you are off idle and you are driving, which makes me ask what makes you think your main jets are clogged? Are you reading the plugs or have you installed a Lambda meter? (wide band Oxygen sensor in the exhaust that allows you to tune the car based upon the fuel air ratio read off of a gauge).

Big Dave