C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Changed intake Gaskets, Now the engine is angry! Help? :(

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Old Apr 6, 2018 | 04:48 PM
  #21  
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Originally Posted by RWDsmoke
If it started easily the distributor is in correctly and the timing is close. If the Distributor cap not seated properly it will cause the rotor to hit the terminals inside the cap. I did that once. It's easy to tell, pull the cap and you can see the marks where it was making contact.
It starts really well... best it has since I've owned it! If only it wasn't so angry sounding! I'm pretty sure the cap is on correctly, but I'll double check! It's got 4 screws to hold it down, and they went in fine, but at this point I'll check anything I can.

Originally Posted by Kevova
I would spin it over a few times with the plugs out on the chance if something is there it might blow out spark plug hole. Only take about 15 sec. Just unplug pink wire from distributor cap first.
I'll give that a go. I'm going to test compression on each cylinder, then if that checks out, I can take the cap off and confirm TDC lining up with #1 on the cap like factory while I'm doing it. While I'm checking compression, I'll remove all plugs for ease of cranking, and that'll give ample opportunity for something to blow out if it's going to happen.

Originally Posted by Kevova
If distributor is not seated all the was down and is up about 1/8 " or so above manifold. The distributor gear has not engaged oil pump driveshaft. Engine can start and oil pump would not pump oil properly. Gear would be spinning just above drive . If this is the case do not force distributor down! Light pressure while someone bumps engine the gear and shaft will eventually align and distributor will drop in. Balancer can be turned also but make sure is out of ignition.
In what you're saying... wouldn't that mean it would interfere with the little distributor cover that bolts to the upper intake? That fit in place normally, and didn't touch the distributor, but I can certainly check again. The "clamp"/hold down portion at the base with the bolt is clamped on the "ridge" of the distributor base, and it seemed to be resting on my new gasket, but I'll double check that too!

Originally Posted by Bagpype
Could a tool or piece of debris have fallen into the valley when the intake was off? The pushrods do move quite a bit and could cause a great deal of noise if something is in there..
Boy I certainly hope not! I don't recall seeing anything in there out of the ordinary when I put the lower intake back on. It bolted down fine, so certainly nothing should be in the way that interfered with that much. I'm trying to think if there's an access hole to the valley for me to put the bore scope in to, but I don't think there is so I may be SOL without tearing it apart again.

Originally Posted by Hot Rod Roy
Any time you remove the distributor from an engine, you NEED a timing light attached to the engine when you first attempt to start it! Ignition timing is extremely important to keep from damaging a newly assembled engine! Your experience as a mechanic should have taught you that.
My experience and the FSM led me to just marking the distributor... however, I DID mess part of that up, which is that whole "I'm human" thing. So you got me there I suppose. However, I'll be honest and say that the noises the engine makes within the first 5 seconds of it running are scary enough to me to never have had time to check the timing. Heck, I never even got out of the drivers seat before turning it back off!


Overall, I think the next thing is compression test, check timing as best as I can with the engine off, assuming it all checks out, put it all back together, crank it and pray... record video, and then... see what happens. I'll post up the results when I'm done. Thanks again everybody for all your ideas and help! I really appreciate it.

One last question... what's the chances I could have a compressed/stuck lifter that'd cause noise like this?
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Old Apr 7, 2018 | 02:00 AM
  #22  
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Originally Posted by Lunchcopter
It starts really well... best it has since I've owned it! If only it wasn't so angry sounding! I'm pretty sure the cap is on correctly, but I'll double check! It's got 4 screws to hold it down, and they went in fine, but at this point I'll check anything I can.



I'll give that a go. I'm going to test compression on each cylinder, then if that checks out, I can take the cap off and confirm TDC lining up with #1 on the cap like factory while I'm doing it. While I'm checking compression, I'll remove all plugs for ease of cranking, and that'll give ample opportunity for something to blow out if it's going to happen.



In what you're saying... wouldn't that mean it would interfere with the little distributor cover that bolts to the upper intake? That fit in place normally, and didn't touch the distributor, but I can certainly check again. The "clamp"/hold down portion at the base with the bolt is clamped on the "ridge" of the distributor base, and it seemed to be resting on my new gasket, but I'll double check that too!



Boy I certainly hope not! I don't recall seeing anything in there out of the ordinary when I put the lower intake back on. It bolted down fine, so certainly nothing should be in the way that interfered with that much. I'm trying to think if there's an access hole to the valley for me to put the bore scope in to, but I don't think there is so I may be SOL without tearing it apart again.



My experience and the FSM led me to just marking the distributor... however, I DID mess part of that up, which is that whole "I'm human" thing. So you got me there I suppose. However, I'll be honest and say that the noises the engine makes within the first 5 seconds of it running are scary enough to me to never have had time to check the timing. Heck, I never even got out of the drivers seat before turning it back off!


Overall, I think the next thing is compression test, check timing as best as I can with the engine off, assuming it all checks out, put it all back together, crank it and pray... record video, and then... see what happens. I'll post up the results when I'm done. Thanks again everybody for all your ideas and help! I really appreciate it.

One last question... what's the chances I could have a compressed/stuck lifter that'd cause noise like this?
if it's a stuck lifter it would be more like a clack...
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Old Apr 7, 2018 | 05:05 PM
  #23  
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Okay! So I did some more digging and here's some new results. I removed all the spark plugs again, removed the pink wire from the distributor, pulled the fuel injector and fuel pump fuses (can't hurt to pull all 3), and got to doing my compression test. Here's a few things that I noticed and my results.

1. My engine didn't clank or make angry noises when cranking over without the plugs in. So that's positive I think. If there was something in the valley or in the cylinders that I just missed while putting it together, I feel like I'd have heard something.

2. Compression results were less happy than I'd have hoped they were. Cylinders 1, 2, 3, 5, 6, 7, and 8 seem to be a healthy 180-190 PSI. Good! But then... there's Cylinder 5... It's at 155.

Poor Cylinder 5...
Anyway... while I don't think this is what I was hearing, noise wise... that's a variance of 14-15%, which is too much, right? So... does this mean it's valve-job time?

I had noticed that on cylinder 5 the first time around that I had noticed one of the valves looked open. This should be normal... cam rotation and wherever it stops and all... but when I went out to check just now again, the same valve appears to either be partially open, or maybe this is showing a dropped valve seat? Maybe it's nothing? What do you all think?



*EDIT* Yeah... something is up I'm pretty sure. Bumped the motor over and took another photo, you can see the other valve is open now, this one has remained the same. Bummer... head rebuild time?


Last edited by Lunchcopter; Apr 7, 2018 at 05:18 PM. Reason: Took second photo
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Old Apr 7, 2018 | 05:59 PM
  #24  
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All valves have to look like each other so you could start by taking the rocker off and see if you broke a spring
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