Generation III Internal Engine 1997-2006 LS1 | LS6
Sponsored by:
Sponsored by:

Leak down results, need advice.

Thread Tools
 
Search this Thread
 
Old Jan 29, 2024 | 08:39 PM
  #1  
650slpss's Avatar
Thread Starter
Teching In
5 Year Member
Liked
 
Joined: Nov 2018
Posts: 46
Likes: 2
Default Leak down results, need advice.

So I did a leak down because car was down a bunch of power, finally did a leak down and got these results. Pistons did contact the valves so I’m expecting valves of course considering the results. Now I’m debating if it’s worth the hassle of just buying fresh heads and doing PTV check before start up, I know the current heads are milled just don’t remember how much. But anyways given the leak down results, lmk what yall think. Any advice will be very much appreciated!








Reply
Old Jan 31, 2024 | 05:48 PM
  #2  
650slpss's Avatar
Thread Starter
Teching In
5 Year Member
Liked
 
Joined: Nov 2018
Posts: 46
Likes: 2
Default

Wrong forum?
Reply
Old Jan 31, 2024 | 10:39 PM
  #3  
dixiebandit69's Avatar
TECH Resident
10 Year Member
Liked
Loved
Community Favorite
 
Joined: Mar 2012
Posts: 859
Likes: 402
From: Texas
Default

Originally Posted by 650slpss
So I did a leak down because car was down a bunch of power, finally did a leak down and got these results. Pistons did contact the valves so I’m expecting valves of course considering the results. Now I’m debating if it’s worth the hassle of just buying fresh heads and doing PTV check before start up, I know the current heads are milled just don’t remember how much. But anyways given the leak down results, lmk what yall think. Any advice will be very much appreciated!
I would just get some new valves and have the heads refreshed, but that's just me.

Which heads do you have right now?
Reply
Old Feb 1, 2024 | 12:46 AM
  #4  
650slpss's Avatar
Thread Starter
Teching In
5 Year Member
Liked
 
Joined: Nov 2018
Posts: 46
Likes: 2
Default

Originally Posted by dixiebandit69
I would just get some new valves and have the heads refreshed, but that's just me.

Which heads do you have right now?
I have 243s that I bought back in 2013, bought them off here used. I know the dude had them ported and milled just don’t remember how much they were milled tbh. The only cylinder that leaked air thru the dipstick and oil fill was cylinder 1, but I’m sure one of the valves leaks too since all 8 have valve marks 😂.
Reply
Old Feb 1, 2024 | 10:43 AM
  #5  
CattleAc's Avatar
TECH Fanatic
15 Year Member
Liked
Loved
Community Favorite
iTrader: (7)
 
Joined: Dec 2007
Posts: 1,644
Likes: 429
From: Dakota Territory
Default

Originally Posted by dixiebandit69
I would just get some new valves and have the heads refreshed, but that's just me.

Which heads do you have right now?

I'm with dixiebandit69 on this one. I assume you know why the pistons and valves decided to kiss??

If not, I guess I'd get that figured out first.
Reply
Old Feb 1, 2024 | 11:52 AM
  #6  
650slpss's Avatar
Thread Starter
Teching In
5 Year Member
Liked
 
Joined: Nov 2018
Posts: 46
Likes: 2
Default

Originally Posted by CattleAc
I'm with dixiebandit69 on this one. I assume you know why the pistons and valves decided to kiss??

If not, I guess I'd get that figured out first.
right on, I’m assuming because of the milled heads and the lift on my cam, maybe valve float or incorrect pushrod length? This time around I’m do the work my self and make sure it’s done right.
Reply
Old Feb 3, 2024 | 07:27 AM
  #7  
Old Buzzard's Avatar
TECH Fanatic
15 Year Member
Liked
Loved
Community Favorite
 
Joined: Jan 2009
Posts: 1,063
Likes: 475
From: Bostwick, GA.
Default

"I’m assuming"... First mistake.
Do an autopsy as you take it apart.
Reply
Old Feb 3, 2024 | 10:09 AM
  #8  
1988montecarloss's Avatar
TECH Resident
10 Year Member
Photogenic
Liked
Loved
iTrader: (6)
 
Joined: Nov 2011
Posts: 972
Likes: 139
From: maine
Default

as others have said, gotta tear it down to know for sure what the course of action would be and definitely check ptv clearance when putting it back together

and as far as not knowing how decked the heads are you could CC the chambers and that would give you a ballpark compared to what others have for CC with .030", .040" etc cut off them
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-1

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-2

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-3

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-4

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-5

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-6

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-7

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-8

10 Camaros You Should Never Buy

 
story-9

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
Old Feb 3, 2024 | 02:50 PM
  #9  
650slpss's Avatar
Thread Starter
Teching In
5 Year Member
Liked
 
Joined: Nov 2018
Posts: 46
Likes: 2
Default

Originally Posted by Old Buzzard
"I’m assuming"... First mistake.
Do an autopsy as you take it apart.
oh I for sure will, waiting for the rain to go away since I don’t have the car in a garage. But I’ll definetly be taking out the cam, heads and lifters.
Reply
Old Feb 3, 2024 | 02:51 PM
  #10  
650slpss's Avatar
Thread Starter
Teching In
5 Year Member
Liked
 
Joined: Nov 2018
Posts: 46
Likes: 2
Default

Originally Posted by 1988montecarloss
as others have said, gotta tear it down to know for sure what the course of action would be and definitely check ptv clearance when putting it back together

and as far as not knowing how decked the heads are you could CC the chambers and that would give you a ballpark compared to what others have for CC with .030", .040" etc cut off them
when checking ptv, do you use solid lifters for it? Or can I use regular hydraulic lifters with check springs on the valves?
Reply
Old Feb 4, 2024 | 06:32 AM
  #11  
LS1Formulation's Avatar
12 Second Club
Community Builder
Liked
Loved
Community Favorite
iTrader: (14)
 
Joined: Apr 2006
Posts: 3,891
Likes: 1,137
From: Grand Rapids, Michigan
Default

I always take hydraulic lifters and disassemble them and stack some washers below the plunger to make them "solid". Then you know the internal spring isn't collapsing any as you rotate the engine. Obviously, make sure you remove the washers before using them, or have a pair dedicated just to degreeing/ptv checking. Paint dab the top of them with a paint marker so you know they're not to be used for anything else.
Reply
Old Feb 4, 2024 | 02:20 PM
  #12  
grinder11's Avatar
TECH Junkie
20 Year Member
Liked
Loved
Community Favorite
iTrader: (1)
 
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Default

Originally Posted by Old Buzzard
"I’m assuming"... First mistake.
Do an autopsy as you take it apart.
Spot on! One BIG rule we were taught as apprentice toolmakers was NEVER ASSUME ANYTHING.
Reply
Old Feb 6, 2024 | 04:02 PM
  #13  
1988montecarloss's Avatar
TECH Resident
10 Year Member
Photogenic
Liked
Loved
iTrader: (6)
 
Joined: Nov 2011
Posts: 972
Likes: 139
From: maine
Default

Originally Posted by 650slpss
when checking ptv, do you use solid lifters for it? Or can I use regular hydraulic lifters with check springs on the valves?
Either works, if youre gonna use a stock lifter modifed to be solid make sure theres no slack in it, i use a comp checker spring with mine
Reply




All times are GMT -5. The time now is 05:48 PM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE