Help please. Burns oil, low compression but no broken rings.

rednewedge

New Member
Apr 24, 2020
1
0
1
23
illinois
Hi everyone, i have an 2004 gt 2v that i rebuilt probably 2 years back now. It's been burning oil since then and i mean a lot, mainly when you give it the gas but even if i drove 400 miles it would burn a quart. Amid the virus and car shows/cruise nights cancelled i decided to finally fix it. Before this all i did a compression test and all cylinders except #6 and #5 had 180, #6 had about 135, #5 had about 170. I did do the trick of adding oil into the cylinder to figure if the valve seals or the rings were bad, the pressure went up with oil inside meaning it should be rings.

Upon taking #6 out the piston rings are not broken and everything physically looks fine on it, the top of the piston was clean as can be with no burnt oil but the other 3 had buildup. #7 is caked, #5 has about half of it covered and #8 has minimal buildup. All of the valves have buildup but #6 valves are the worst out of all of them.

During the rebuild i put some cams in and got the heads ported, the guy who did my heads i can't believe would not put new valve seals in when he has to take all of the valvetrain off anyways but i will be calling him soon to make sure of that. I have noticed inside the T/B and plenum where the EGR fitting goes on there is a lot of oil for being the inside of a T/B but the EGR pipe goes into the headers side where all the oil burning is taking place. Also noticed oil in the intake valley at the bottom and in the intake runners of the heads. I have read of the PCV systems on these cars do suck a lot of oil into the intake but with my compression so low i'm not sure that could be the real problem.

The shop that honed my block did go over a thousandth and there was confusion with that, but i'm pretty sure that was all fixed with a tad bigger pistons and rings to fix the issue. I was pretty young at the time and i'll be honest i could have accidentally put the smaller size rings on there by accident. But at this point i can only think the possible smaller rings issue or i didn't break in the rings properly.

Any help whatsoever would be greatly appreciated and can add photos if that helps.
 
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08GT500

Active Member
Jul 12, 2018
897
139
53
50
Massachusetts
Hi,
That’s not good. Well, I’ll list what’s popping out at me....maybe elaborate, further, etc.
I’ve experience in engine rebuilding, 2 shops in the family, maybe able to find out if the shop said something that makes no sense, etc.(Like #1 below).
Don’t post the receipt with a business name there, edit it out. If there’s a receipt
with notes there, I should be able to read between the lines.
1) So this was rebuilt with the automotive machine shop accidentally honing your cylinders oversized, and your positive it’s 0.001 (not 0.010 over) the shop went?
They didn’t then say they bored & honed the cylinders.
Just said they used oversized pistons?
No pistons are made for just installing into a block to correct an oversized honing error, only going larger by prepping the bores (Boring & Honing) minimal size up is +0.020
0.030.
High end is generally +0.060.

2) The person who ported your heads did all the head prep, checking guides, spring load, valve grinding, etc.. as a real Automotive machine shop would, but you believe he never replaced the original valve seals?
Is it a pro shop? Anyone with a die grinder may think they are qualified to do porting, yet many do more harm than good.
There is issues with the 2V intakes, PCV vapors getting pulled into the TB.
Car still running now?
-John