bench starting an sbc?: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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April 11, 2011 8:59 p.m. internetautomart SuperDork

ok so it's not really bench starting it as much as it is trying to start it before we completely assemble the motor.
so far we haven't even been able to get it to crank one full revolution with the starter. that is from trying 3 starters! We can turn the motor over by hand with no issue, but it doesn't want to take a starter. we have put in a new battery,

this is a long block with a dizzy, intake, carb, and a fuel pump.

it is seriously driving me nuts!

The starter bendix doesn't fully retract and gets stuck in the flexplate.
April 11, 2011 9:02 p.m. novaderrik HalfDork

shim the starter out, and make sure all the connections are nice and tight. also, check that one of the starter bolts isn't bent- that's really easy to do with a stock starter if you let the weight of the starter hang on one bolt before getting them both snug.
April 11, 2011 9:54 p.m. internetautomart SuperDork

shimmed it out, connections seemed tight. I'll check the bolts
April 12, 2011 5:50 a.m. GregW New Reader

Bent flexplate?
April 12, 2011 6:05 a.m. 44Dwarf Dork

Is the grond wire going directly to the starter and not the block? If not try that it should turn. As for the bendix sounds like shimming or wrong flex plate. It's been awhile are big block plates dished? Did someone put it on dished out instead of in? I've seen that before.
April 12, 2011 6:21 a.m. novaderrik HalfDork

44Dwarf wrote:

Is the grond wire going directly to the starter and not the block? If not try that it should turn. As for the bendix sounds like shimming or wrong flex plate. It's been awhile are big block plates dished? Did someone put it on dished out instead of in? I've seen that before.

taking the balancing counter weights on the 400 and 454 out of the equation, older Chevy flexplates are physically interchangeable from the inline 6 of the mid 50's to the 454s of the late 80's and really only go on one way- the center hole is "flared" in such a way that it's fairly obvious which way it bolts to the crank and the flexplate mounting holes are embossed so that they stick out towards the torque converter. i have seen some that had what looked to be excessive runout that could cause a starter drive (NOT a Bendix, no one has called them that for like 40 years) to jam if it was too close to the ring gear, which can be compensated for with a shim or two.
April 12, 2011 11:50 a.m. 44Dwarf Dork

True but does a 12 year old that helped him know what obvious is??? E36 M3 happens..
April 12, 2011 1:48 p.m. jstand New Reader

Have you tried without spark plugs installed? Or without power to the distributor?

Sounds like you might be seeing bind due to the timing being out...
April 12, 2011 2:39 p.m. tuna55 Dork

How are you powering the starter? Sounds like a huge loss. Measure the voltage at the starter when you are attempting cranking and then measure the current when cranking.

If you can crank it by hand, then the starter, flexplate or block is either hideously misaligned or there isn't enough power at the starter. Have you checked the plate for runout and round? Made sure of the proper pinion for the flexplate?
April 12, 2011 3:29 p.m. scardeal HalfDork

I have nothing to add, but I think you're taking bench racing a little too seriously
April 12, 2011 7:05 p.m. internetautomart SuperDork

jstand wrote:

Have you tried without spark plugs installed? Or without power to the distributor?

Sounds like you might be seeing bind due to the timing being out...

yup, tried with the dizzy depowered

tuna55 said:

How are you powering the starter? Sounds like a huge loss. Measure the voltage at the starter when you are attempting cranking and then measure the current when cranking.

If you can crank it by hand, then the starter, flexplate or block is either hideously misaligned or there isn't enough power at the starter. Have you checked the plate for runout and round? Made sure of the proper pinion for the flexplate?
we tried it with the power cables from the factory (positive to the starter, negative to the block) and we tried it with jumper cables too.
April 12, 2011 7:10 p.m. tuna55 Dork

internetautomart wrote:

we tried it with the power cables from the factory (positive to the starter, negative to the block) and we tried it with jumper cables too.

Manually ground the starter to the block. Then check to make sure the block ground is right. Sounds like you might have a bad ground?