Timing Rebuilt Engine to Start
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Timing Rebuilt Engine to Start
Just finished putting a Vortec 5.7 bottom end into my 1991. I put the stock aluminum TPI heads and intake on as well as just about everything else from the vette. Im using the Vortec timing cover and harmonic balancer as well as the entire rotating assembly which should be very similar. Also have the Vortec camshaft in which is where I believe my problem is. Trying to time the engine by setting to TDC yields intake backfiring and yes I have tried swapping the rotor 180* multiple times. The Vortec cam has a 111* LSA versus the stock l98 114*. Is this where part of my problem lies? Can anyone suggest a way to time this engine? I'm about to start moving the rotor over one notch at a time until it stops backfiring but I figured I'd ask before I went through the trouble. Thanks
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From: Mission Viejo CA
Are you sure the valves are adjusted properly? If you have an intake valve or valves too tight, you'll backfire!
Regarding timing, here's a technique I've used. It's a bit unconventional, and some people to whom I've described it don't understand, but I'll throw it out for you to consider. It does work!
Basics: To get a spark from your distributor, the shaft rotates, and as the ICM creates a rising waveform, the coil creates the spark.
My way: The ICM doesn't care whether the shaft rotates, or the housing rotates. It's the relative motion between the shaft and the housing that will create the rising waveform. Either way, you'll get the spark!
1. Set engine at 6-8* BTDC, compression stroke, #1 cyl.
2. Insert a loose spark plug in wire #1, with grounded shell.
3. Ignition on.
4. Quickly twist the distributor.
5. Note the position of the dist. where the plug fires.
6. Set the dist. at that position.
7. Snug down the dist. clamp.
8. Install #1 plug wire.
9. Start the engine.
10. Adjust the timing the normal way. This procedure is only to get the engine running.
Two advantages: You know you've got spark. And you know you're not 180 out.
Regarding timing, here's a technique I've used. It's a bit unconventional, and some people to whom I've described it don't understand, but I'll throw it out for you to consider. It does work!
Basics: To get a spark from your distributor, the shaft rotates, and as the ICM creates a rising waveform, the coil creates the spark.
My way: The ICM doesn't care whether the shaft rotates, or the housing rotates. It's the relative motion between the shaft and the housing that will create the rising waveform. Either way, you'll get the spark!
1. Set engine at 6-8* BTDC, compression stroke, #1 cyl.
2. Insert a loose spark plug in wire #1, with grounded shell.
3. Ignition on.
4. Quickly twist the distributor.
5. Note the position of the dist. where the plug fires.
6. Set the dist. at that position.
7. Snug down the dist. clamp.
8. Install #1 plug wire.
9. Start the engine.
10. Adjust the timing the normal way. This procedure is only to get the engine running.
Two advantages: You know you've got spark. And you know you're not 180 out.
Last edited by Hot Rod Roy; Jun 7, 2016 at 02:24 AM.
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From: Glenbeulah Wi
Just finished putting a Vortec 5.7 bottom end into my 1991. I put the stock aluminum TPI heads and intake on as well as just about everything else from the vette. Im using the Vortec timing cover and harmonic balancer as well as the entire rotating assembly which should be very similar. Also have the Vortec camshaft in which is where I believe my problem is. Trying to time the engine by setting to TDC yields intake backfiring and yes I have tried swapping the rotor 180* multiple times. The Vortec cam has a 111* LSA versus the stock l98 114*. Is this where part of my problem lies? Can anyone suggest a way to time this engine? I'm about to start moving the rotor over one notch at a time until it stops backfiring but I figured I'd ask before I went through the trouble. Thanks
-Put the engine at 6 degrees BTDC on the compression stoke and align the rotor with the number 1 terminal in the cap. That will be close enough to get it to start and then use a timing light to set it correctly.
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I was pretty confident about the valves but that will be a point i check soon although now i believe the harmonic balancer bolt is stripped in the crank and just holding in by a few threads so thats another beast. I like the timing idea roy but not so sure i could do that with limited space behind the tpi. I used a timing light while turning starter and it didnt look like it was hitting at the timing mark in either positions when i set the dist. Ill attempt to turn the dist once this tropical storm passes.
Also my starter is whining like crazy which it wasnt with the old engine. Should i get a hi torq starter or try to figure out why the engines tighter?
Thanks again
Tyler
Also my starter is whining like crazy which it wasnt with the old engine. Should i get a hi torq starter or try to figure out why the engines tighter?
Thanks again
Tyler
