First Time engine startup woes
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
First Time engine startup woes
I just finished my first rebuild with all stock internals. The problem is that the car shakes when I have it running, but smooths out when I give it a bit more RPM.
My big concern is that I went to a machine shop to get my crank ground down and they just gave me another one they said it was the same kind and I asked about the balance being the same they told me that this was a stock balance and I didn't need to worry.
Did I get duped?? or could there be something else wrong? I think the timing might be advanced too much but I wouldn't think that would make the car shake. There's a big cam in it but I don't think that would do it either(230/236 in an otherwise stock engine).
Is the normal 350 1-piece rear different from the LT1 crank balance wise?
The car is up on jack stands by the way, I'm not sure how much this helps or hurt the shanking.
My big concern is that I went to a machine shop to get my crank ground down and they just gave me another one they said it was the same kind and I asked about the balance being the same they told me that this was a stock balance and I didn't need to worry.
Did I get duped?? or could there be something else wrong? I think the timing might be advanced too much but I wouldn't think that would make the car shake. There's a big cam in it but I don't think that would do it either(230/236 in an otherwise stock engine).
Is the normal 350 1-piece rear different from the LT1 crank balance wise?
The car is up on jack stands by the way, I'm not sure how much this helps or hurt the shanking.
Last edited by mn_vette; Jul 26, 2005 at 09:19 PM.
Le Mans Master
Joined: Jul 2001
Posts: 8,183
Likes: 3
From: Santa Maria, CA
This happened to me also, but for flywheel issues.
What year engine? L98? LT1? What year crank? What trans do you have? Any other changes to the drivetrain? What gears does the shaking happen? Does it do it in Park or Neutral?
Did the machine shop have balancing capabilities? I would have insisted to no end to get the reciprocating assembly balanced.
What year engine? L98? LT1? What year crank? What trans do you have? Any other changes to the drivetrain? What gears does the shaking happen? Does it do it in Park or Neutral?
Did the machine shop have balancing capabilities? I would have insisted to no end to get the reciprocating assembly balanced.
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Originally Posted by danno85
That's a big enough cam to cause an engine to shake at an idle. An out of balance crankshaft will cause a vibration (as opposed to a shake) and at a higher rpm.
What's the difference between a shake and a vibration?
This is an LT1, Roadmaster setup with vette pistons and rods, big cam, big TB everything else is stock. The car is an auto with at 2500 stall and 3.45 gears. The car is up on jack stands with all the wheels off the ground. I'm running a rear mount distributor that I don't have dialed in exactly yet.
I'm curious to know if the LT1 crank has a different balance than the normal 350ci 1-piece rear cranks.
Burning Brakes
Joined: Nov 2001
Posts: 1,189
Likes: 2
From: Austin TX
Originally Posted by mn_vette
What's the difference between a shake and a vibration?
is a more irregular motion.
Have you made any changes to richen the air/fuel mixture at idle? With the increased overlap of the bigger cam the mixture in the cylinder will otherwise be leaner and that will make it run rougher at idle as well.
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Originally Posted by danno85
A vibration is a very "regular and consistent" (for lack of a better phrase) motion, and usually a higher frequency (rapid), whereas a shake
is a more irregular motion.
Have you made any changes to richen the air/fuel mixture at idle? With the increased overlap of the bigger cam the mixture in the cylinder will otherwise be leaner and that will make it run rougher at idle as well.
is a more irregular motion.
Have you made any changes to richen the air/fuel mixture at idle? With the increased overlap of the bigger cam the mixture in the cylinder will otherwise be leaner and that will make it run rougher at idle as well.
I'd really like to know if there's a balancing difference, or where I could find out. If anybody knows please give me a heads up.
The A/F is really rich right now. I pulled one of the plugs last night and it was black. I'm missing an EGR block off plug for my header so I didn't want to use the wideband to start tuning the car. I ordered one and it should be in today.
Burning Brakes
Joined: Nov 2001
Posts: 1,189
Likes: 2
From: Austin TX
I can't help you on any differences in the factory balancing of the two engines - I just don't know. If you really did have an out of balance vibration though I would expect it to get worse, or at least persist, at higher rpms.
Is this the engine you've got the Accel DFI on? If so, is the tach steady at an idle or is it jumping around too at idle speeds and then smoothing out when you raise the rpms?
Dan
Is this the engine you've got the Accel DFI on? If so, is the tach steady at an idle or is it jumping around too at idle speeds and then smoothing out when you raise the rpms?
Dan
