350 no start

Discussion in 'Trucks and Trailers' started by Sawbones, Oct 23, 2000.

  1. Sawbones

    Sawbones LawnSite Member
    Messages: 14

    I just put in a 350 that has some tweaks(shaved heads, larger cam, bored to 357, 9.5:1 compression) in my 77 GMC K15. It runs great but now Ive been through 2 hi-torque starters (broken noses) and having trouble with the 3rd. It seems to lack enough power to crank the engine. It will turn over slowly if at all unless its jumped from another car and starts fine but the cranking is overly loud. I have had the battery(optima 800) checked which is relatively new, played with the timing, adjusted the shim of the starter, and checked the alternator but cant seem to find the problem except for lack of amps. Do I really need more than 950 cranking amps? Please advise before I screw somthing major up.
    Thanks, Sawbones.

    OBRYANMAINT LawnSite Senior Member
    Messages: 555

    my opinion is that with a high performance engine you will need some high performance acces to make it run/start properly get a bigger battery

    i had a camaro way back that had a very high compression eng that always started slow

    lots of things can contribute to a slow start situation after you change the engine soo dramatically
  3. John DiMartino

    John DiMartino LawnSite Silver Member
    Messages: 2,555

    There are a couple of things you need to check-1st,you have the HD 350 truck starter motor-the 305 and car ones have smaller motors that wont crank over a high compression 350.Next,check your feed cable+ to the starter-maybe you need to buy a thicker one if its the skinny one on there now-the diesel cables are the best and are usually free at the wrecking yards if they arent already cut.Check your ground path back to the battery-make sure there is a big heavy ground cable from the block or alternator bracket- to the battery,then make sure there is a cable to the body/frame from the block or - terminal.The best way to see if its your- side giving you the problem is to take a set of jumper cables-go from the battery and double up the stock cables-go to block with - and the main lug on starter with positive-then see if it cranks over faster-if so-you found some of the problem.Last-you need to check your ignition timing-it might be overadvanced-this is likely the main reason for snapping off drives,it will grunt bad if its to far advanced.try backing off thre timing a tiny bit-push the vacumm advance canister towards the firwall about 1/4" and try it again-see if its better-if its fine-test drive it-if its lost power-you need to get the distributor recurved-go to a good shop or buy a kit from a speed shop,so you can have both the ******** static timing and more advance when rpm's increase.
  4. Power mad

    Power mad LawnSite Member
    Messages: 72

    I agree with John about the timing. When I read your post I immediatly identified with your problem. Right after I rebuilt the Big Block in my 73 I was going through so many starters that I kept two in the cab. Broken nosecones the whole 9 yards. Bigger cables, retarding the timing (2 degrees BTDC ) and recurving the distributor took care of that particular bug
  5. Sawbones

    Sawbones LawnSite Member
    Messages: 14

    You guys are the sh*t!!! How could I have overlooked the ground? the frame was grounded but not the block. Yes, I am am a rock. Thx guys. unfortunately I'm gonna have to make another starter purchase. this one snapped just after i recognised the problem. thanks again.
  6. John DiMartino

    John DiMartino LawnSite Silver Member
    Messages: 2,555

    Glad you found it,its easy to miss the obvious when doing engine swaps.I once helped a guy with the same exact problem,it would crank slow,I seen smoke as he cranked it,I looked over,and the throttle cable was glowing red,on fire in spots .The power found a ground thru it,and welded it solid in the process.He had replaced 2 starters and 2 batterys before he called me-expensive mistake.

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