New 345 rebuild not turning over well

GaryOR

GaryOR

Member
I purchased a '78 Scout II with a new rebuild on a 345 performed by a mechanic. Unfortunately, not everything external was done correctly by the owner. Many things I have already fixed. However, currently I am not getting the engine to turn over well. It's acting like a weak battery. However, it is new and fully charged. As well, I've got a charger/starter attached while I turn it over.

I know this is a pretty general question, and the answers/solution could be one of many things. But it's been many years since I've worked on an engine and just need some starting tips.
 
Like you say, this could be so many things. The easiest thing to check and adjust on the fly while cranking is the timing. If you loosen the disty retaining bolt just enough, it is possible to rotate the thing while starter cranking. If the timing is off by enough, (usually too far advanced) it can make for hard revolutions. These engines are low compression and spin over very quick and easy when everything is correct. If that proves to have little or no effect, then you're most likely dealing with an electric issue. Just because a battery is new doesn't mean it can't have a dead cell. I've seen batteries show a full surface charge and then go to crap when put under load. If you have a hand held dvom, probe the batt terminals during starter cranking. Verify that all your cabling and connections between the batt and the starter are sound, clean and tight. Take voltage readings at the solenoid before and during starter cranking looking for excessive voltage drop. That should keep you busy for awhile.
 
Has this engine ever actually fired off and run???

When doing a full engine build on any engine, it's very common for it to be "tight" initially when done properly. And by tight I mean it cranks over slowly, not from lack of lubrication but just because it's tight!

We need the details of the engine build if you know them...and do you mean that "electrically" it's slow to crank over. How long has it been sitting non-rotated? Have you removed all spark plugs and cranked over? I need to know if by doing that it allows much easier turn-over, makes no difference, or anywhere in between!

Engines I build all get cranked over for several seconds at a time with the plugs out after verifying they are lubricating. Ya need to crank over for no more than 10 seconds with a five minute cooldown for the starter in between bursts, otherwise you will end up needing a replacement starter, these are intermittent duty cycle items.

Then if the cranking test passes, the plugs are installed for initial fire-up, always with a battery charger with real output (minimum 10 amps) connected to the battery throughout the entire initial fire-off process.
 
Has this engine ever actually fired off and run??? No. However, on one of the earliest attempts, I got about a 3 second run (before my son turned off the key in his excitement).

We need the details of the engine build if you know them...and do you mean that "electrically" it's slow to crank over? Don't know. Yes, electrical is what it seems to be.

How long has it been sitting non-rotated? Probably 8 months.

Have you removed all spark plugs and cranked over? I need to know if by doing that it allows much easier turn-over, makes no difference, or anywhere in between! Yes, no difference.

I measure 18 volts at the battery, at the connection to the solenoid, and at the pos side of the coil. At the second 2 locations, the voltage drops to 13 when turning over. I haven't checked the current yet. And, I know I'm getting spark to cylinder 8 because my timing light was firing when turning it over. I'll test the other cylinders for fire next time out and will check spark plug gaps (don't trust the po for anything anymore with all the mistakes I've found).


I'm accustomed to vehicles that spin really fast when cranking. Is the 345 just not one of those and maybe it's all a carb/fuel problem? I've been priming the carb with a little gas when trying to start it, but just found out late today-wait for it-the po had the lines to the fuel pump backwards so I was blowing fuel back into the jug that is serving as my fuel tank!!!!
 
These motors are really lazy about cranking over if compared with other typical deetrot iron.

Typical cranking compression on a fresh motor should be in the 135>150psi range.

Starter current draw at cranking speed onna typical engine is 85>135a, no more than a 15 second burst with at least 3 minute cool-down between attempts.

An engine sitting non-rotated that length of time needs to be pre-lubed, here's the process:

http://www.forums.IHPartsAmerica.co...I-4-sv-engine-non-oiling-rocker-assembly.html

A fully charged battery at 18vdc??? No way! A fully charged conventional lead/acid flooded cell battery is 12.8vdc after the surface charge is removed. Voltage drop to under a nominal 10.8vdc while cranking is unacceptable which means the battery is not up to snuff.

You are right about the po virus, trust nothing that has gone before. I'd start at verifying that the distributor is installed correctly and the cap is wired properly for the firing order:

http://www.forums.IHPartsAmerica.com/ignition-tech/4130-installing-distributor.html
 

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Ok, so that was stupid. Of course my battery doesn't have that much voltage. The stinking battery in my meter was going out. Now that I'm no longer an idiot, my car battery measures 12.3v. When I put a load on it turning over the engine, it drops to about 10.8v (measured directly from the battery). However, measuring at the positive lead on the coil, I only get around 7.8v. Is that appropriate with a 1.8ohm ballast resistor in front of it?
 
Btw, removed the ballast resistor (per michael mayben's suggestion), and with a new basic coil, bingo-instant start on the first try!
 
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