420a Built bottom help!!

[matt98eclipse]

I have a friend that has a built 420a bottem end with je pistons and eagle rods. One day he noticed the car seemed to misfire pretty bad. We did a compression test and got 180,180,180,135! The car had pretty bad blow-by from the dipstick and valve cover also! Today I took the top end off and found one of the cylinder walls was pretty scratched! All I'm suppose to do for my buddy is put new je rings in the motor but what do u guys think should be done? Also there is no crosshatch in the cylinder walls for some reason when the motor just got built less then a year ago!!!

The cylinder that has the scratches isn't the one thats low!!!
The one with the scratches had 180!


Should i just put the new rings in and hope they will seat ok for now??

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[Locke]

If the depth of the scratches are minor, and the piston to cylinder clearance is acceptable, you can get away with honing the scratches out. Honing must be done anytime you install new rings, in order for them to seat.

• Lack of oil on the cylinder walls can cause smooth bores, as is common with fuel washed cylinders.
• Rings not seating correctly due to an improper hone can also cause the cylinders to be smooth.
• Detonation can cause the piston skirts to scratch the cylinder walls.
• A piston installed backwards (420a pistons are 1mm offset) may cause the pistons skirt to scratch the cylinder walls.
• Improper piston to cylinder wall clearance can also smooth the cylinder bore and may scratch it as well.

And of course, any combination of the above mentioned points will both hasten and worsen the problem.

 

[turbodsm_125]

what he said is very ture. also make sure that you alternate the gaps in the piston rings! if they all get aligned they will blow out oil like crazy! Check the pistions to see if this is what happened the first time. Also look to see what caused the failure the first time. personally i would not put it back together till i found out what happed and made sure that it did not do it again as it takes a lot of time and money to redo these kinda things

 

[matt98eclipse]

Thanks Locke for all the information. I know theres way to much piston to cylinder clearance! I checked the paper work from the shop and It was 3 times the amout of the stock specs from the chilton book! You can rock the piston back and forth a little while its in the block!

Also if you look in the pics you can see little nic marks on the top of all the pistons! The cylinder wall with all the scratches had the worst on that piston!!

 

[VelocitàPaola]

Why do you keep posting 420A questions in the general area; especially when you see them all get moved to the 420A area?

 

[matt98eclipse]

I had only asked 2 questions about the 420a and only 1 of them got moved. Sorry

 

[bullettdsm]

Guy, you got lean conditions and detonation written all over those pistons. You could easily have some broken ring landings. What's goin on with the engine?

MB

 

[matt98eclipse]

I was thinking the same thing about the detontion, this is my buddys car thats his daily driver! Im just gonne be the one rebuilding it. I haven't pulled the cylinder with the low compression out yet to see if the ring lands are broke but i really wounldn't doubt it!!