SBC won't idle right and dies when put in gear - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-22-2010, 08:30 PM
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SBC won't idle right and dies when put in gear

Alright guys I have build several engines and never had one that was this big of a pain. Here is the background on the engine 350 sbc with xe274 Comp cam, Procomp 210 heads, Hurricane single plane manifold, 600 holley vacuum secondary carb, points stock type distributor all brand new. New harmonic balancer with multiple markings for timimg, the vertical timing mark (not using it), a degreed marking (one I'm using) and a single timing mark. They are on the balancer in that order. The timing doesn't make any sense, reading 40 degrees BTC without vacuum. The dwell is 28. If I try and take the timing lower it won't start. It also seems that when I have the timing set so it will start that it is way advanced (hot starting is a bear). I can only get it to idle down and run at about 900-1000 rpm, but if you put it in gear it dies. The tranny is a new rebuild th350 with a new stock stall converter.

I know that the intake will kill the bottom end for this setup and plan on a dual plane later, however I can't believe this is causing my grief. The valves are adjusted correctly, triple checked them with the last time engine running. The timing I set watching the #1 intake valve close and the bringing it to 0 on my timing tab , this will fire it off but must add advance to keep it running without giving it gas which is as expected. Like I said earlier though my timing shows 40 degrees before tdc.

So what do you think?
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Old 12-22-2010, 08:47 PM
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That cam will not work with a stock converter. Needs a 3000 stall.
Made all the more critical by the racey single plane manifold.

get a 10" 3000+ stall.
The tdc point is wrong. Use a piston stop to find true tdc and correct the pointer position.
That cam will want 18 to 24deg base at idle 34 to 36 at max mech adv.

10-15deg of vacuum advance at cruise.
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Old 12-22-2010, 09:25 PM
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why are you measuring dwell? are you running points?
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Old 12-22-2010, 09:42 PM
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Yes I'm running points, didn't want to bash in the firewall for HEI. As far as the cam requiring a high stall I emailed comp cams with all my engine/trans specs and they suggested the xe274 and said the stock stall converter was fine so it should work. It shouldn't have anything to do with idle as it is free spinning, it will engage earlier (lower RPM) without slippage when put into gear though. I also ran a comp cam 280h years ago with a stock stall converter and it ran fine.

I tried the straw in the #1 spark plug hole for a piston stop to get close and it ends up landing me close to where I am setting but to start it I have to move it to where it is now.

The cam was put in straight up also.
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Old 12-22-2010, 09:52 PM
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i agree you are running _WAY_ too much initial timing.

bring the timing back to what they suggested earlier, then work with the carb to get it to run, my guess is you probably set way way to lean on the idle.

turn the idle speed up until it WILL run with the timing at reasonable number, and chase the idle speed down with mixture and speed adjustments...
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