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Old 11-28-2010, 01:52 PM
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SBC 400 still no start

Hey all;
I'm still having the problem with my 75 Monte Carlo not starting and it's really pissing me off now. I was working on her today, and this is what I've done.

Pulled plug #1, and brought the motor around to the compression stroke and the timing on the harmonic dampner is correct. Book says -8btdc, but have been trying everything from 0-30btdc, just to get something out of it.

Last week, the motor would backfire out the exhaust. This week, was doing nothing until the last time I retimed it. It decided to backfire out the carb. Big boom, cloud of smoke, and then the carb was on fire. Tried again just to see if anything would happen, and it eventually backfired out the top again.

Battery is brand new and fully charged. Had my jumper on it as well

Starter is turning over the motor no problem.

Pulled valve covers and all parts are moving.

Took timing gun and checked out all the wires. All have signal. #1 fires where ever I time #1 to be (-8 right now)

Spark plugs are brand new

I don't know what else to do. Bottom end is totally stock. When I got it, was tore down to the bottom end. Everything else went altogether fine and while following the book. Please help!!! Thanks guys

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Old 11-28-2010, 01:59 PM
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Sounds like Valve adjustment too tight?? How did you set it??
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Old 11-28-2010, 02:41 PM
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Quote:
Originally Posted by ericnova72
Sounds like Valve adjustment too tight?? How did you set it??
Tightened the nuts on the valves under the push rods just couldnt spin. Then tightened the center allen key on the nut til tight.

Wouldn't the valves not open if it was too tight?
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Old 11-28-2010, 03:10 PM
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Quote:
Originally Posted by david-b
Tightened the nuts on the valves under the push rods just couldnt spin. Then tightened the center allen key on the nut til tight.

Wouldn't the valves not open if it was too tight?
You have them too tight, you are holding the valves off the seat so they can't seal, and the spark causes a fire in to the intake, or out the exhaust through the gap.

The manuals can be confusing for someone not familiar with them, the "spin the pushrod" method gets more young guys in trouble than you can shake a stick at. You need to spin the pushrod until you just feel a very slight drag, not bound up and no longer able to spin. What you have done is bottomed out the lifter plunger.

A better method is to jiggle the pushrod up and down until you feel all loose play is removed, then add 1/4-1/2 turn more to preload the plunger into just some of its travel in the lifter, then lock it down.

Go back to your valves, loosen everything off, and set them using the method I just outlined above, the "jiggle method".

More than a few of use oldtimers wish they would just quit printing the "spin method" as it fouls up more people than it helps, it seems. works okay for someone familiar with it, or someone who has a teacher familiar with it guiding them, but it hooks a lot of rookies.
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Old 11-28-2010, 03:24 PM
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This is my first larger motor with anything like that adjustable. I've only worked on rice burners and small 4 cylinders

I do appreciate the help. I won't be at the garage until hopefully tomorrow and I will pull everything off and try again. I was always told to tighten them until there was no play, up or down or twisty and then tighten the center nut. Hopefully I can have some good news to report back tomorrow. Other than that the thing is ready to go (and it better go soon as it needs to go in storage for the winter)
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Old 11-28-2010, 03:30 PM
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Good luck, let us know how you make out.
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Old 11-28-2010, 03:49 PM
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And just to clarify, ensure each lifter is on the back side of the lobe when adjusting it, not on the ramp or up on the lobe.

All my toys are in winter storage already, good thing too, we had a "cold front" move through, it dropped to 45 last night, 75 and clear today....sorry, couldn't help saying that, but I just moved here from Alaska last July, already paid my dues for 37 years....
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Old 11-28-2010, 03:51 PM
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Quote:
Originally Posted by ericnova72
You have them too tight, you are holding the valves off the seat so they can't seal, and the spark causes a fire in to the intake, or out the exhaust through the gap.

The manuals can be confusing for someone not familiar with them, the "spin the pushrod" method gets more young guys in trouble than you can shake a stick at. You need to spin the pushrod until you just feel a very slight drag, not bound up and no longer able to spin. What you have done is bottomed out the lifter plunger.

A better method is to jiggle the pushrod up and down until you feel all loose play is removed, then add 1/4-1/2 turn more to preload the plunger into just some of its travel in the lifter, then lock it down.

Go back to your valves, loosen everything off, and set them using the method I just outlined above, the "jiggle method".

More than a few of use oldtimers wish they would just quit printing the "spin method" as it fouls up more people than it helps, it seems. works okay for someone familiar with it, or someone who has a teacher familiar with it guiding them, but it hooks a lot of rookies.
haha i also fell victim to the spin the push rod till its tight method. I thought well thats how the book said it so it must be right. I called up my machinist and he said up and down and that should fix everything and it did. I was also having the same issue popping through the intake and exhaust. Good luck and again like eric said let us know how it works out.
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Old 11-28-2010, 05:17 PM
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Good to know it's a common mistake.

Just to verify this (since I have time to ), at TDC, tighten the nut to where the pushrod is just starting to feel tension. Should have no up/down movement. Then 1/4 to 1/2 turn and then tighten the center allen nut all the way down. That's all!

I hate Chicago weather. Near 50s today, was 70 last Monday, was 20s the rest of the week. Car is in the garage being used for storing her, but I don't like starting the cars for the first time in the garage, especially since they like to catch on fire like today.
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Old 11-28-2010, 05:42 PM
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I always do the same but I go by the rocker arm. I tighten it down to zero lash on the rocker arm an top of valve. Tightened to where there is no slack an you have side to side movement with rocker arm on top of valve. Tighten additional 1/2 to 3/4 a turn an you are done.

Note, make sure lifters are primed.
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Old 11-28-2010, 05:48 PM
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Quote:
Originally Posted by david-b
Good to know it's a common mistake.

Yep it's a common mistake till you adjust the valves to far/to tight and brake the valve off and lock up the engine. JMO



Cole
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Old 11-28-2010, 05:49 PM
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Quote:
Originally Posted by david-b
Good to know it's a common mistake.

Just to verify this (since I have time to ), at TDC, tighten the nut to where the pushrod is just starting to feel tension. Should have no up/down movement. Then 1/4 to 1/2 turn and then tighten the center allen nut all the way down. That's all!

I hate Chicago weather. Near 50s today, was 70 last Monday, was 20s the rest of the week. Car is in the garage being used for storing her, but I don't like starting the cars for the first time in the garage, especially since they like to catch on fire like today.
Yep, rattle the pushrod up and down and tighten rocker nut until there is no free clearance left, this is known as "zero lash", then anywhere from 1/8-3/4 turn farther to set the lifter plunger into its hydraulic travel a touch, and then lock the center allen set screw on your rocker nut. 1/4 to 1/2 turn is the most common.
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Old 11-28-2010, 05:51 PM
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Almost sounds like someone dropped the distributor in before rotating the the crank 360* after installing the timing chain. If that happened, the cam would be 180* off from the crank. Correct alignment would be dot on cam gear and crank gear at 12:00 not 6:00 on the cam and 12:00 on the crank.
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Old 11-28-2010, 05:53 PM
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[QUOTE=ericnova72]Yep, rattle the pushrod up and down and tighten rocker nut until there is no free clearance left, this is known as "zero lash", then anywhere from 1/8-3/4 turn farther to set the lifter plunger into its hydraulic travel a touch, and then lock the center allen set screw on your rocker nut. 1/4 to 1/2 turn is the most common.[/QUOTE.]



This is how i do it most of the time also.



Cole
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Old 11-28-2010, 08:57 PM
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the way my friend showed me to make sure that you was on the base circle was, exhaust open you set the intake and intake close you set the exhaust. i just find it easier to do it that way, then the way the manual says to do it.
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