My students rebuilt a 305 in class. It's going to be my shop test motor, so I need it to run. It cranked really hard when we got it(it was donated, so I didn't complain to much). We made 1 good starter out of 2, and we tested it before we put it on the motor. All we did was put new rings in it, cause the old ones were stuck to the pistons. So, now with old bearings, and new rings, it still cranks really slow. The connection between the solanoid and case glows red hot after only a few seconds of cranking. We melted 2 sets of quality jumper cables trying to get it to spin using an 800 CCA battery. I checked the starter for binding, and it's not. It won't crank fast enough to consistantly spark(i'm using points in a rebuilt distributer), and suck air and fuel in(pouring gas down the carb). What would make this thing not crank? Thanks in advance. -Shop Teacher Bugman Jeff
if you have it on a engine stand or crate you are going to have to make sure you have a good ground, jumper cables from a battery are not going to cut it.a ground strap from engine block to battery is needed.
How does it turn over by hand, socket on balancer bolt or turning flywheel by hand or with screwdriver? If it doesnt turn farly easy with spark plugs out could be binding somewhere internally. Rod & main bearings are cheep!! Dont know your engine building experience level so kinda hard to answer. Lots of possibilities.
Two things best done alone-[takin a shit] and [buildin motors] :.........Id say best case scenareo =poor starter ground/worst scenareo .......mixed up rod or main caps during assembly.......[too many cooks in the kitchen]-hope it is the best one.
You need to know if the engine turns freely by hand. Incorrect installation of parts may have the engine locked up. I've started lots of engines with jumper cables only.
also the pistons could have to much gas on top of them and it wont fire?.....but I guess that would cause all the burnt wires....but a thought if youve been dicking with the carb alot before the start up....you could pull #1 plug and see if it blows fuel out when you hit the starter button? good luck
You may try adjusting the timing some. It may be too far advanced. I had this problem on my 50 and chased it for years before realizing it was just the timing off.
I've spun the distrubuter around 270 degrees in both directions,(as far as it goes till the vac advance hits the intake) and it didn't help so it's not timing. It does spin fairly easy by hand, about like the other motors I've rebuilt. I was watching close to make sure the rods and caps went in right. It does spin must easier with the plugs out, so I know there's compression. I didn't replace the bearings cause they were ok, and I can't really afford the $30 they'd cost. I need that for welding supplies, and it's just a shop motor anyway. We've flooded it a few times, and we've starved it a few times, we even tried to fire it on propane and ether. Just got a very few random flames out the intake or exhaust, depending on where the timing was set. We're going to give it another shot this morning. -Bugman Jeff
How easy does it spin by hand compared to w/o plugs by hand?Try to crank the motor over w/o plugs..any difference in how it turns over? How did you check the starter? Cam timing correct? Do a compression check if you suspect some isssues in this area.If you flooded it get a set of new plugs. Good luck.
This happened to me once, whith the motor feeling kinda tight, but not really . I did all the checks mentioned above as well. I found out there are two different torque specs for 305 rod bearings. The Chevy Small block book told me so. Any way I had used the wrong torque spec & overtightened the rod caps; re-torqued and used the motor for a season of dirt track racing w/ no priblems... my $.02 BYC
Double checked the flexplate. It's ok. It does spin a little hard now that I rethink it. Here's my latest theory... I know the engine was apart once before because of aftermarket gaskets, and excess silicone. When we tore into it, the rods weren't numbered, so we numbered them before we took them off. I wonder if 2 rods got switched around last time it was apart. Just enough mismatch to cause some drag. Sound reasonable? Next idea...What if I reduce the torque on the rod nuts? Remember, this isn't a 100,000 mile motor. It'll probably only run a few hours a year, and I'm sure it'll be completely apart in the next few years again anyway. It is a learning motor afterall. If a rod started to come loose, I'd hear it long before it came apart completely. -Bugman Jeff
If you can turn it over by hand, the starter shouldn't have a problem spinning it. I'd be very suspicious of the starter, even if your class already made one from two used ones. Sounds like the armature may be grounding out on the fields, causing a huge amount of resistance.... Make sure both end bushings are in the starter and are tight. Good luck, Jeff.
jeff, I agree with rocky if they had the starter apart I'd be suspect of it.. however, when duck and I tried to fire my old 403 olds with jumper cables we had NO LUCK.. I ended up stealin some battery cables off another car and it turned right over.. so My suggestion as one shop teacher to another.. Blame it on that one wise ass kid in your class... then swap out the starter, and try better battery cables.. later jeff
Youre using a battery along with the jumper cables-I presume?sounds like you've cranked it over plenty -so I am guessing its a timing issue- sounds like it is possible the distributor is in the wrong knotch.also are the points gapped properly[possibly no gap]? an easy way to end up in this situation is to have a balancer from an early 305 of a year that had the timing tab spot welded at about"3 oclock" on the timing cover-then it gets swapped for one of the newer ones that has the timing tab["tube"] straight up at 12 o clock.......see where Im going here? kinda hard to tell when its at "top dead center" with those dual indicators confusing you. a common mix up of parts?
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