Do I need to rebild the bottom end now?

smf · 08-29-09, 12:28 PM

The heads are off getting cleaned up. The top of the pistons look like they have a nice thin layer of something burned on them. Is there a way to clean this? What is it? Burnt on Caked on carbon build up? The motor is a sbc 400.

First motor tear down so not sure what I'm looking at.

Can I just clean up?
Do I need to replace piston and rings?
Should I even worry about it?

dargreg · 08-29-09, 01:16 PM

Looks like the piston liners are glazed and the rings wont be doing there job.carbon build up not bad ,looks like the valve seals are gone,water jacket surprisingly good.Depending on the ridge on the top of the cyl walls.you might get away with bearings, rings, and a hone job.You,ve got the heads off now at least do that.Make sure you tap the head bolt threads they are wet and are full of sealant.SBCs are very simple to re&re,get a Haynse book though.

smf · 08-29-09, 05:42 PM

Quote:

Originally Posted by dargreg

Looks like the piston liners are glazed and the rings wont be doing there job.carbon build up not bad ,looks like the valve seals are gone,water jacket surprisingly good.Depending on the ridge on the top of the cyl walls.you might get away with bearings, rings, and a hone job.You,ve got the heads off now at least do that.Make sure you tap the head bolt threads they are wet and are full of sealant.SBCs are very simple to re&re,get a Haynse book though.

By bearings you mean, bearings for the crank / piston rod?

dargreg · 08-29-09, 06:04 PM

Yup mains and rod bearings.You will get the seals and gaskets all in one kit.Determine if it is still standard,meaning the crank hasnt been ground unless you already know there has been no previous rebuild,and that the pistons are standard.Re use the pistons if you want,saves a lot of grief pressing wrist pins.Just run a broken ring around the grove in the piston to get the carbon out.Get an RV cam and lifters and give er.

smf · 08-29-09, 08:47 PM

Quote:

Originally Posted by dargreg

Yup mains and rod bearings.You will get the seals and gaskets all in one kit.Determine if it is still standard,meaning the crank hasnt been ground unless you already know there has been no previous rebuild,and that the pistons are standard.Re use the pistons if you want,saves a lot of grief pressing wrist pins.Just run a broken ring around the grove in the piston to get the carbon out.Get an RV cam and lifters and give er.

I know the motor has been rebuilt once. It has about 106k on it. I pulled it to replace the time chain and since I have it out I figured I would fix what I can.
I don't have a lot of money so I really want to only replace what's needed. BUT,
I want to avoid pulling the motor again in 15k miles because I did not fix the worn out parts as well.

Forgive the noob questions, what's the difference between an RV can and a regular cam?

Knowing that's is been rebuilt, what would you do?

dargreg · 08-29-09, 08:56 PM

If its been done that explains the clean water jakets.Get a valve grind gasket set do your timeing chain,double roller,put the heads back on it and go.Dont forget to clean the head bolt holes.

smf · 08-29-09, 10:00 PM

Quote:

Originally Posted by dargreg

If its been done that explains the clean water jakets.Get a valve grind gasket set do your timeing chain,double roller,put the heads back on it and go.Dont forget to clean the head bolt holes.

Sorry, I really appreciate the advice! Just so I'm clear.

Valve grind gasket set?

New gaskets(which I have)
I will add new double roller timing chain, put the clean heads on and run it?

Don't need to worry about the bottom end.
You think it will be good for a few more miles?

Thanks again.

dargreg · 08-30-09, 10:23 AM

A valve grind set just gives you the gaskets to to take the heads off,youve got the gaskets .I,ve seen sbc go 3 to 400 thou. miles with proper maintenance,you should be good for quit a while.Put new valve seals on the heads though.Its easy to do if you want to try,but a shop wont charge you much cause the heads already off.