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New crate motor installed - running rough

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Old 06-19-2017, 01:57 PM   #1
jakejay
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Default New crate motor installed - running rough

Hey everyone! I'm new here so sorry if I'm putting this in the wrong spot or don't provide enough information.

I just (yesterday) finished the installation of my new 350 crate engine in my 1985 corvette. Everything is back connected, but when it came time to start it, it will start, but idle really rough and won't stay running without manually holding the throttle.

Any ideas on why it might not want to stay running? Could it be a timing issue?

Thanks in advance for any insights you might be able to provide.

Jake
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Old 06-19-2017, 02:09 PM   #2
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Originally Posted by jakejay View Post
Hey everyone! I'm new here so sorry if I'm putting this in the wrong spot or don't provide enough information.

I just (yesterday) finished the installation of my new 350 crate engine in my 1985 corvette. Everything is back connected, but when it came time to start it, it will start, but idle really rough and won't stay running without manually holding the throttle.

Any ideas on why it might not want to stay running? Could it be a timing issue?

Thanks in advance for any insights you might be able to provide.

Jake
New injectors ???? If not the what is the fuel pressure at idle ?
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Old 06-19-2017, 02:31 PM   #3
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without knowing exactly what you've done - other than dropping in a new crate, we need more details. did you use the original TPI system, or are you doing the carb thing? at this point, it could be anything and everything. start with the basics - fuel, spark and timing. as above, new/old injectors and fuel pressure - ???

TB, IAC, TPS, valve adjustment, vacuum leak, coil/distributor issues, timing, electrical ground(s), ECM, etc., you name it. anything and everything. sorry to be so vague, but provide more details - even a couple pics of the engine bay may help. i'd say, go back to square one, and look at and double check everything.

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Old 06-19-2017, 04:58 PM   #4
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Crate motors are usually pretty well dialed in. How is your timing?
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Old 06-19-2017, 05:15 PM   #5
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Which crate motor did you use?
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Old 06-19-2017, 08:34 PM   #6
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Which crate motor did you use?
It's the standard 350 GM Crate.
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Old 06-19-2017, 08:36 PM   #7
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without knowing exactly what you've done - other than dropping in a new crate, we need more details. did you use the original TPI system, or are you doing the carb thing? at this point, it could be anything and everything. start with the basics - fuel, spark and timing. as above, new/old injectors and fuel pressure - ???

TB, IAC, TPS, valve adjustment, vacuum leak, coil/distributor issues, timing, electrical ground(s), ECM, etc., you name it. anything and everything. sorry to be so vague, but provide more details - even a couple pics of the engine bay may help. i'd say, go back to square one, and look at and double check everything.
Thank you for your detailed reply. It has the TPI and I will look at timing. And I'll double check everything! Thank you!
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Old 06-19-2017, 08:38 PM   #8
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Crate motors are usually pretty well dialed in. How is your timing?
I haven't checked that yet. I'm a real noob when it comes to this stuff. I'm going to work on timing.
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Old 06-20-2017, 02:19 PM   #9
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I haven't checked that yet. I'm a real noob when it comes to this stuff. I'm going to work on timing.
The timing is pretty much the most important thing to check after dropping in a crate motor. If everything worked before, it should work after when hooked up to the new motor. You shouldn't have to check valve adjustments or anything internal. As I said before, crate motors if done by a reputable company should be bolt in ready.
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Old 06-21-2017, 02:12 PM   #10
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It's the standard 350 GM Crate.
You mean the $1500 one from Summit? Do you have a part number?
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Old 06-23-2017, 11:17 AM   #11
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The timing is pretty much the most important thing to check after dropping in a crate motor. If everything worked before, it should work after when hooked up to the new motor. You shouldn't have to check valve adjustments or anything internal. As I said before, crate motors if done by a reputable company should be bolt in ready.
So the timing is off and we can't get it to run at idle. Used a timing gun and can't get it dialed in. Made loads of adjustments to the distributor but it won't stay idling. If I gas it, it will rev up and sounds great. But as soon as the gas is off, it chugs to a stop.

I have old spark plug wires that I'm gonna replace and see if that helps.
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Old 06-23-2017, 11:22 AM   #12
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You mean the $1500 one from Summit? Do you have a part number?
http://www.jegs.com/p/Chevrolet-Perf...52506/10002/-1
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Old 06-23-2017, 11:28 AM   #13
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without knowing exactly what you've done - other than dropping in a new crate, we need more details. did you use the original TPI system, or are you doing the carb thing? at this point, it could be anything and everything. start with the basics - fuel, spark and timing. as above, new/old injectors and fuel pressure - ???

TB, IAC, TPS, valve adjustment, vacuum leak, coil/distributor issues, timing, electrical ground(s), ECM, etc., you name it. anything and everything. sorry to be so vague, but provide more details - even a couple pics of the engine bay may help. i'd say, go back to square one, and look at and double check everything.
I'm using the original TPI system. I think it might be a vacuum leak as I have a part that I can't find the hose to connect. Any idea what this is for and what I'm missing?
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Old 06-23-2017, 12:29 PM   #14
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I'm using the original TPI system. I think it might be a vacuum leak as I have a part that I can't find the hose to connect. Any idea what this is for and what I'm missing?
what you have is an EGR solenoid valve. there should be a mounting bracket on one of the RH rear intake manifold bolts. the solenoid valve mounts to that bracket. from the solenoid, there are two plastic vacuum lines. the rear line goes to the EGR valve, and the forward line goes to the bottom of the throttle body. here's a pic of my 85...



Last edited by Joe C; 06-23-2017 at 12:33 PM.
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Old 06-24-2017, 03:33 PM   #15
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what you have is an EGR solenoid valve. there should be a mounting bracket on one of the RH rear intake manifold bolts. the solenoid valve mounts to that bracket. from the solenoid, there are two plastic vacuum lines. the rear line goes to the EGR valve, and the forward line goes to the bottom of the throttle body. here's a pic of my 85...


That's great thanks! I'm going to look at it tomorrow
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