BIG BLOCK FORD
Would you like to react to this message? Create an account in a few clicks or log in to continue.

Pistons broke at valve reliefs. Any ideas

+3
rmcomprandy
nickpohlaandp
cobra501
7 posters

Go down

Pistons broke at valve reliefs. Any ideas Empty Pistons broke at valve reliefs. Any ideas

Post  cobra501 October 16th 2017, 12:28 pm

This is my buddies engine. Only 5 runs on grudge 521 deal. Two pistons broken and rest cracked at the valve relief. These are Diamond pistons. Looking for answers so he can decide what direction to take. He only hit it with a 350 shot. He found problem during normal inspection.  Engine was running fine before teardown. He did experience a backfire.


Last edited by cobra501 on October 16th 2017, 7:26 pm; edited 1 time in total
cobra501
cobra501

Posts : 95
Join date : 2009-12-13

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  nickpohlaandp October 16th 2017, 12:33 pm

cobra501 wrote:This is my buddies engine. Only 5 runs on grudge 521 deal. Two pistons broken and rest cracked at the valve relief. These are Diamond pistons. Looking for answers so he can decide what direction to take. He only hit it with a 350 shot. He found problem during normal inspection.  Engine was running fine before teardown. He did experience a backfire.

Sometimes the most obvious questions still need to be asked... is your buddy sure he had the ring gap set right? I've seen too tight of a ring gap pull the top off many pistons once you spray the gas on em.

nickpohlaandp

Posts : 157
Join date : 2017-09-24
Age : 45
Location : Lake Charles, LA

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  cobra501 October 16th 2017, 1:02 pm

I should have thought of that. Good point. I will let him know and from there. Thanks.
cobra501
cobra501

Posts : 95
Join date : 2009-12-13

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  rmcomprandy October 16th 2017, 3:25 pm

cobra501 wrote:This is my buddies engine. Only 5 runs on grudge 521 deal. Two pistons broken and rest cracked at the valve relief. These are Diamond pistons. Looking for answers so he can decide what direction to take. He only hit it with a 350 shot. He found problem during normal inspection.  Engine was running fine before teardown. He did experience a backfire.

Detonation or not enough ring end gap or maybe both.

rmcomprandy

Posts : 6157
Join date : 2008-12-02
Location : Roseville, Michigan

http://www.rmcompetition.com

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  lance flake October 16th 2017, 4:50 pm

Is the 2nd ring pinched in the ring land? What does the skirt look like scuffed?

lance flake

Posts : 142
Join date : 2009-12-28
Location : union ms

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  cobra501 October 16th 2017, 5:54 pm

If someone will PM me your phone number I will text you two pics and some more tonight when I get them. I never could upload pics here.
cobra501
cobra501

Posts : 95
Join date : 2009-12-13

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  gt350hr October 16th 2017, 6:48 pm

If the intake valve relief machining left a "wall" , the cylinder pressure spikes caused that wall to flex and the piston cracked at the inside radius of the ring groove. IF the valve notch machining broke through that "wall" , the lateral pressure would be reduced and the failure could be rings butting as Randy mentioned. That is the "cooler" side of the piston and is not known for detonation until a section breaks out and the hot ring causes localized melting of the surrounding area. Detonation would "normally " appear around the top ring land and usually on the exhaust side. It creates a texture like shot peening. Pictures will help the diagnosis.

gt350hr

Posts : 662
Join date : 2014-08-20
Location : Anaheim , CA

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  cobra501 October 16th 2017, 8:00 pm

https://s13.photobucket.com/user/cobra501/library/?sort=3&page=1#
cobra501
cobra501

Posts : 95
Join date : 2009-12-13

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  cobra501 October 16th 2017, 8:26 pm

I tried posting a pic. No luck so far. I got more pics lastnight and they tell a better story than he described. This damage has to be improper ring gap. Pics show that the area above the ring groove is busted from a ring bind. This was new motor and 1300 spent on a new set of pistons.


Last edited by cobra501 on October 17th 2017, 5:35 am; edited 1 time in total
cobra501
cobra501

Posts : 95
Join date : 2009-12-13

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  cool40 October 16th 2017, 10:13 pm

No pics.....private
cool40
cool40
BBF CONTRIBUTOR
BBF CONTRIBUTOR

Posts : 7313
Join date : 2009-08-31
Age : 53
Location : on the 1/8 mile dyno

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  Mark O'Neal October 17th 2017, 3:50 am

On the outside by the intake pocket?

Lean

Mark O'Neal

Posts : 286
Join date : 2009-08-12

Back to top Go down

Pistons broke at valve reliefs. Any ideas Empty Re: Pistons broke at valve reliefs. Any ideas

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum