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Suburban 454 non start after rebuild...

K

KeyBlazer

1/2 ton status
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Jul 18, 2007
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Location
Irvine, California
Finally got the motor back in...
It fires and will run but runs really rough.
It backfires too....:o
I am confused about a couple of things..
The distributor is in, but there are 2 positions in the manual.
One says that at #1 TDC the rotor arm should be at "6:30" for the "points style distributor" and the other says "5.30" for the HEI style distributor.
Mine is a electonic pickup, but the coil is seperate, ie, not on the distributor cap.
What is the correct position?
 
As long as the dist is firing the cylinders correctly(as in properly timed), it really doesn't matter where the distributor is pointed. That's not gonna change how it runs, despite how much one instructor at UTI argued that it was a big deal. Recheck your timing, and make sure everything got connected at the dist. I guess it's the '87 with TBI?
 
Did you personally rebuild this or have it done? I have seen this sort of thing with cam timing being off, it's just unusual for it to happen. It's also kind of a pain to check, but if your sure everything else is right it's a possibilty. You've got me hooked now, it's like a mystery novel.:D
 
carb or efi.
who adjusted the valves you or them how long has it been running did you break in the cam upon first fire up?
where abouts in irvine im in bp so not to far might be able to come by and take a peak at it.
is the cap and rotor new aswell as plug wires?
 
I did it myself.... I thought I got it done right..
Is there anyway to check without pulling the front of the motor off again?
 
Ok, tore the front off the motor to check the cam timing..
Here is a pic..
CamTimeE.jpg


I looked in the Haynes Manual.... and was confused...
So I did a websearch and took the info from the Comp Cams site..

Step 2 – Chain Installation
Now that the lower crankshaft gear is installed rotate the crankshaft using your crankshaft socket, (Part #4793 for Small Block Chevy or #4797 for Big Block Chevy), until the appropriate crankshaft gear tooth is in the 12:00 position and the crankshaft gear keyway slot is in the 2:00 position.
The #1 piston should be at top dead center. Rotate the camshaft until the camshaft dowel pin is at the 3:00 position.
Loop the chain over the camshaft gear. Align the camshaft and crankshaft timing marks and loop the chain around the crankshaft gear. Lift the camshaft gear into place on the camshaft. Install the three
camshaft bolts (finger tight for now). Make sure that the camshaft gear timing mark aligns with the proper crankshaft gear timing mark. The camshaft timing mark should be at 6:00 and the crankshaft gear timing mark should be at 12:00. If this procedure is missed by even one tooth, engine damage can result. ​

This looks like the pic I have, or am I wrong?
You can just make out the dot on the crank gear, and I assure you that the crank keyway is at 2 o'clock.
Now, funny thing is that when the engine is in this position, the distributor looks 180 deg wrong..... ie, the rotor arm is at 11 o'clock and pointing at the firewall..
Before anyone askes, I did have a feeling I was 180 on the dizzy, so I tried it the other way... No start!
Confused!​
 
The dizzy does not care where it is pointed as long as the firing order is right. you can drop it or asighn any of the trerminals number one cyl ans then continue the firing order from there.
the pic is alittel hard to see lower gear but looks right can you take one from farther away.
by the way wow way to tear into it who rebuilt the motor and how where the valves adjusted im leaning to a stuck valve or mis adjusted valves.
 
Cam chain gear stripped and took out all inlet valves and inlet pushrods..
See this thread for the start..
http://coloradok5.com/forums/showthread.php?t=213492&highlight=cam+chain

So, measured the bores, and they were good... reringed the pistons, new bearings, and swapped the whole heads from the other engine that showed to be good.
Cam and lifter are new. MT6 Melling RV cam, so should be a torque monster.
 
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pM me you're number and i can call you tommorrow maybe even come by
i also remember that thread now looking back.
also try and do a compression check of all cyl may be a bad valve or miss adjusted is it back firing out the carb or out the exhaust.
 
Valves check and re adjust them. it sounds like they are tight and holding open causing back fire.
 
So we are in agreement that the cam timing is good?
I am going to grab a Cold MGD and put the front of the motor back now and retime the dizzy to the 5-30 position.
More later.....
 
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