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Blown engine advice #736973
June 04th 2018 7:53 pm
June 04th 2018 7:53 pm
Joined: Jun 2018
Posts: 1
FL-CA
K
KenD941 Offline OP
stranger
KenD941  Offline OP
stranger
K
Joined: Jun 2018
Posts: 1
FL-CA
Greetings all my name's Ken and this is not an ideal first post. I screwed up and severely overheated my engine and now it's time to pay the price.

I have 1990 Chevy G30 van with a 5.7 (60K on the odometer) which was overheated and is now running rough with some detonation/timing issues. I took it to 2 different shops to diagnose, one stated the timing chain was loose and needed replacing, and the other shop simply couldn't diagnose the problem. So I was about to pay the first shop to replace the timing chain for $800, but thought it prudent to do an engine oil analysis, and compression test first to see if it was worth it. The compression test was as follows;
Driver side --- Passenger side
140 ---130
35 --- 50
30 --- 50
125 --- 130

I tripled checked the first 2 reading on the driver's side as I thought (hoped) the gauge broke, but the numbers repeated. So no need to do an oil analysis. I'm assuming I heated the engine enough to warp the heads. My instinct is to replace the entire engine, but since I'm traveling and my shop is 3000 miles East I'm scrambling. Local shops have quoted $3000 to $4500 just in labor. Additionally this engine apparently no longer grows on trees! The local chevy dealer says there're no more in stock, and while JEGS quoted me an ATK brand rebuild I found out today it's out of stock and they don't know when one will be available.

Options I'm pondering are unloading the van, or shipping it home, and just having the engine rebuilt locally once I remove it.

Another option I'm considering, which I'm hoping to get some opinions on, is just having the top end rebuilt. I figured I can remove the heads and have them rebuilt locally without having to remove the entire engine. Has anyone here done this? And also do you think the engine block surface that mates to the heads needs to be resurfaced due to the overheating? This option sort of feels like I'm rolling the dice (again!) and hoping nothing else, like damaged pistons/rings/cylinder walls, was damaged by the overheating.

Lastly (fingers crossed) is it possible a loose timing chain can cause low compression in some cylinders, but not others?

Thank you for any thoughts on this,
Ken

Re: Blown engine advice [Re: KenD941] #736978
June 04th 2018 8:35 pm
June 04th 2018 8:35 pm
Joined: Aug 2001
Posts: 11,620
Fircrest, WA
Reed Online content
Maniac
Reed  Online Content
Maniac
Joined: Aug 2001
Posts: 11,620
Fircrest, WA
Well, when a motor overheats badly you can score the cylinder walls and cause a loss of compression, crack the valves, crack the heads, warp the heads, and warp the block. The first thing I would do is a leakdown test to see if you can pinpoint where you are losing compression.

A loose timing chain would cause low compression in all cylinders. It is possible you wiped out some lobes on the cam.

If the heads warped, then the block deck likey also warped and would need to be cleaned up.

Lousy situation, sorry to hear you are in it. Good luck!

Hey, maybe post where you are at and someone local can help you out.


Windows- they're what make a van worth owning!
Re: Blown engine advice [Re: KenD941] #736982
June 04th 2018 9:05 pm
June 04th 2018 9:05 pm
Joined: Sep 2005
Posts: 8,355
Georgia, USA
CatFish Offline
carpal tunnel
CatFish  Offline
carpal tunnel
Joined: Sep 2005
Posts: 8,355
Georgia, USA
1.) Are you able to do a cylinder leakage test?
Compression tests are almost useless (IMO worms), it'll tell you there is a problem (which you already know) but don't help much to diagnose.
A leakage test will show you where the pressure is escaping, if there is a head gasket/cracked head or a bent valve or a scored cylinder,etc so that you can make a more informed decision.
If it turns out to be cracked heads/gaskets (for instance), a new set of heads/gaskets to get home now and a new short block later would be a more wise use of resources. If the "bad" cylinders show low/normal leakage (again for instance) then you wiped the cam lobes. But you'll need more info....... a leakage test by someone who is competent will speak volumes.
My 2%

Last edited by CatFish; June 04th 2018 9:20 pm. Reason: kant spel

They can have my fried bologna sandwich when they pry it from my cold dead hands.
Re: Blown engine advice [Re: KenD941] #736985
June 04th 2018 9:37 pm
June 04th 2018 9:37 pm
Joined: Jun 2010
Posts: 13,354
Van Diego California
frscke1 Offline
frscke1  Offline

Joined: Jun 2010
Posts: 13,354
Van Diego California
Welcome to the site Ken ....


SUNSHINE VANS-VAN DIEGO
ADRENALIN BY THE GALLON & CHASIN RACIN
ONE FOR THE DIRT & ONE FOR THE STREETS
'93 CHEVY G30 454 4X4 SPORTVAN EXT 146" WB
'92 CHEVY G30 454 BEAUVILLE EXT 146" WB
Re: Blown engine advice [Re: KenD941] #736989
June 04th 2018 11:01 pm
June 04th 2018 11:01 pm
Joined: Mar 2016
Posts: 309
Tucson,Az.
H
Hasan Ben Sobar Offline
enthusiast
Hasan Ben Sobar  Offline
enthusiast
H
Joined: Mar 2016
Posts: 309
Tucson,Az.
Those numbers tell me that the head gasket is blown between the 2nd & 3rd cylinder on each bank.


Tucson-it's a dry heat...like an oven

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