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Ls3 swap wont crank and backfires.

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Old Oct 31, 2015 | 05:24 PM
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Default Ls3 swap wont crank and backfires.

Ok heres the background. I bought a used l92 block and had it completely rebuild except for the rods and crank. Crank reluctor was swapped to 24x and tack welded. It has tick street heat stage 2 cam and pnp heads by greg goods. Im using my 411 pcm and was reflashed.

The issue is that car will not start and it backfires on the intake.
Check:
Fuel pressure. Ok
Sparks. Ok
Signals from cam and crank sensors . Ok
Cam gear was 180 degrees off. Fixed it and still no start.
The only thing left to check without dropping the pan is the reluctor wheel to make sure he installed the wheel right since he tack welded it. The engine builder did not have the tool to replaced the wheel so i sent it to lamar walden to do the wheel swap. Could the engine builder improperly installed the crankshaft and cost the relctor wheel to be off? Or is lamar waldens error?

Any help or suggestions?


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Old Oct 31, 2015 | 05:52 PM
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If it was 180* out of tune, you got bent valves.
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Old Oct 31, 2015 | 06:32 PM
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Originally Posted by blk00ss
If it was 180* out of tune, you got bent valves.
The engine didnt even start yet. Will only trying to crank it cause a bent valves?
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Old Oct 31, 2015 | 07:39 PM
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Did you change the cam Sprocket ?
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Old Oct 31, 2015 | 08:00 PM
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Originally Posted by laurentj23
The engine didnt even start yet. Will only trying to crank it cause a bent valves?
Lol oh yeah. I had it happen once. Backfired and then spun over really easy.
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Old Nov 1, 2015 | 12:15 PM
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Originally Posted by KH504
Did you change the cam Sprocket ?
cam gear changed to 1x. theres pressure while trying to turned it by hand while checking the reluctor wheel
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Old Nov 1, 2015 | 12:42 PM
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Reluctor wheel seperated. One half spinning or both spinning
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Old Nov 1, 2015 | 06:41 PM
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Originally Posted by dogsballs
Reluctor wheel seperated. One half spinning or both spinning
From the snake cam, Looks like both are spinning.
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Old Nov 2, 2015 | 11:12 PM
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Ouch, The spec on the reluctor wheel is something like +/-.010 runout front to back. That needs to be right, but the big question, is it timed right when it was welded on the crank? It has to be degreed to the crank or the timing will be off. I agree with 00ss, probably have bent valves. Compression check needed. Those little details can cause big problems.
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Old Nov 2, 2015 | 11:21 PM
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https://ls1tech.com/forums/generatio...tor-wheel.html

Check this post. It shows a reluctor alignment tool. If you do not use something like this, your timing is probably not right.
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Old Nov 2, 2015 | 11:31 PM
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If you used a cam sensor extension harness check to make sure the wires aren't reversed. Very common issue and can cause this symptom. Make sure crank sensor is correct one also.
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Old Nov 3, 2015 | 01:46 PM
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Originally Posted by racecar
Ouch, The spec on the reluctor wheel is something like +/-.010 runout front to back. That needs to be right, but the big question, is it timed right when it was welded on the crank? It has to be degreed to the crank or the timing will be off. I agree with 00ss, probably have bent valves. Compression check needed. Those little details can cause big problems.
Im not sure whether it was timed right or not. the machine shop that rebuilds the engine do not have the tool to take the wheel off, so i took it to Lamar Walden, Along with the 24x reluctor and let him changed it out. After that, I brought it back to the machine shop that rebuilt the engine.
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Old Nov 3, 2015 | 01:47 PM
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Originally Posted by racecar
https://ls1tech.com/forums/generatio...tor-wheel.html

Check this post. It shows a reluctor alignment tool. If you do not use something like this, your timing is probably not right.
I believe Lamar walden used that tools. Not a lot of machine shop in ga able to change the reluctor wheel.
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Old Nov 3, 2015 | 01:48 PM
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Originally Posted by gnx7
If you used a cam sensor extension harness check to make sure the wires aren't reversed. Very common issue and can cause this symptom. Make sure crank sensor is correct one also.
All that has been changed and the wiring has been fixed. Brand new crank sensor as well.
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Old Nov 3, 2015 | 07:42 PM
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Originally Posted by blk00ss
If it was 180* out of tune, you got bent valves.
Yeah, this is definitely a possibility. Almost a certainty.

OP, you may want to do a compression and/or leakdown test. You very well may have bent the valves with the cam gear 180 off from the crank gear.
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Old Feb 20, 2016 | 10:11 AM
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Originally Posted by KCS
Yeah, this is definitely a possibility. Almost a certainty.

OP, you may want to do a compression and/or leakdown test. You very well may have bent the valves with the cam gear 180 off from the crank gear.

Ok. So updates:
Brought the car to abother mechanic. He tore down the engine, changed the crank to 24x reluctor wheel. Inspect everything and adjust clearances. Wire everything up and it still wont crank. Wtf!!?
Im this close to part everything out...!
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Old Feb 20, 2016 | 11:11 AM
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Originally Posted by laurentj23
Cam gear was 180 degrees off
How did you determine this? The gear will be pointed at 6 and 12 on the compression stroke and 12 and 12 on the exhaust stroke.
The cam turns at 1/2 speed so if aligned at 12 and 6 and you turn the crankshaft one revolution they would be aligned at 12 and 12. So I don't think that was a problem, You just thought it was.
So no bent valves from misalignment.
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Old Feb 22, 2016 | 05:08 PM
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Any updates?
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Old Mar 1, 2016 | 12:22 PM
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Originally Posted by LLLosingit
Any updates?
The mechanic tore the whole engine apart and recheck everything again. He couldn't find anything wrong. He gonna try and put a new sensors in and check for compression. Other than that, he's clueless as well.
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Old Mar 5, 2016 | 10:09 PM
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has anyone checked pushrod to see if correct length
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