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Username Post: Engine rebuild advice        (Topic#351428)
Sails941 
Poster
Posts: 9

Reg: 07-29-17
06-04-18 04:33 PM - Post#2735927    

I screwed up. I 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 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





 
scrambldcj8 
Senior Member
Posts: 2352
scrambldcj8
Loc: MA
Reg: 04-06-03
06-04-18 04:49 PM - Post#2735928    
    In response to Sails941

It's possible you just popped the head gaskets. How hot did it get? Interesting the similarities between the numbers on both pass and driver side.



 
CowboyTrukr 
"7th Year" Silver Supporting Member
Posts: 3989
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
06-04-18 05:08 PM - Post#2735932    
    In response to scrambldcj8

Yup. The 3-5 and 4-6 webs failed. Not a timing chain issue.

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Sails941 
Poster
Posts: 9

Reg: 07-29-17
06-04-18 09:30 PM - Post#2735969    
    In response to scrambldcj8

Q:How hot did it get?

A:Who really knows? I was relying on the factory temp gauge, and while it would never quite touch the red area it did come close a few times.

(The back story is I bought the van off the internet in Seattle, and had the weekend to drive it back to San Francisco. While the test drive went fine once I bought it and started going up mountains the temp would start to climb. On straight aways ran great for hours on end. Anyways I would always pull over when the needle got close to red and let it cool off. I guess it just happened too many times. )

Thanks,
Ken



 
scrambldcj8 
Senior Member
Posts: 2352
scrambldcj8
Loc: MA
Reg: 04-06-03
06-05-18 03:33 AM - Post#2735987    
    In response to Sails941

Have you checked the oil for signs of water/antifreeze?......chocolate milky?



 
bowtie44s 
Valued Contributor
Posts: 3994
bowtie44s
Age: 35
Loc: wv
Reg: 08-29-12
06-05-18 05:11 AM - Post#2735998    
    In response to Sails941

Your compression test definitely revealed that you have problems. Hitting 250° shouldn't crack a head or block.

You can probably take the heads off, have them cleaned and magnafluxed, put new head gaskets in, and be good to go. If you have the money and don't mind spending it, a crate motor is the best bet. If Jegs doesn't have one, check Summit. That is my preferred one anyhow.

You will definitely want to change your radiator and flush the block if you reuse your old one. Your radiator probably looks like the one pictured below. If I hit a hill, the temperature would start climbing. I cut the radiator apart to scrap it (copper/brass) and see what was going on and thought it was picture worthy.



Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
Sails941 
Poster
Posts: 9

Reg: 07-29-17
06-05-18 06:46 PM - Post#2736083    
    In response to scrambldcj8

Q:Have you checked the oil for signs of water/antifreeze?......chocolate milky?

A: Only minimally.
Oil - The dip stick shows only clean oil. No sign of water / milky color. The second mechanic I went to said he did top off my oil, but I'm not sure how much he added. I don't think much, if any, as that was a month ago and it's still at the full mark.

Coolant - My coolant reservoir was empty yesterday, and the radiator coolant level was about 2 inched down from the cap. Color was antifreeze green with no sign of oil. (black floaters?)

Of note though is an increasing puff of smoke out the tailpipe at startup. Usually only on a startup after the engine's been off for hours. (This was another reason I did the compression test).

Thank you,
Ken




 
Sails941 
Poster
Posts: 9

Reg: 07-29-17
06-05-18 07:30 PM - Post#2736087    
    In response to bowtie44s

Jeff thanks for the picture and advice!

I hadn't thought about this issue. My mind went thru bad thermostat, faulty radiator clutch-fan(?), timing too advanced, but I never considered junk in the radiator. I'll definitely look into this further.

I'd love to put a crate engine in, but I can't stomach $4000 in labor for something I can do myself. And finding a location to do it while on the road is proving difficult.

I'm really thinking of just rebuilding the top end. The timing chain diagnosis though is haunting me a bit. I've searched for quite a while on how to determine if a timing chain has excessive play/slack in it, and only found one believable test. Please let me know if you think this is an accurate test, or you know of another.
It goes like this;
1. Remove the distributor cap
2. With a socket on the flywheel bolt turn engine so the rotor is pointing approx to #8 cylinder.
3. Now turn the flywheel backwards to line up #1 at TDC. Timing mark should be at zero.
4. Now turning the flywheel forward slowly, watch the distributor rotor. As soon as the rotor starts to move stop, and note the timing marks. If the marks is 7 degrees or greater timing chain play is excessive.

Credit goes Eric the car guy on youtube.

What do you think about this test?
(One variable that could add some play to this test is the gear at the end of the distributor shaft, but the distributor is new)

Thank you all very much,
Ken







 
bowtie44s 
Valued Contributor
Posts: 3994
bowtie44s
Age: 35
Loc: wv
Reg: 08-29-12
06-05-18 09:40 PM - Post#2736105    
    In response to Sails941

I do like Eric the car guy. I don't know if the 7° is the definitive cut off or not. You HAVE to pull your heads no matter what. At that point, all you have left is drop the oil pan a little bit, pull the harmonic balancer and the timing cover and you can see for sure how much wear it has. At that point you may as well spend $20-$30 and put a Cloyes double roller timing set in it and you will never have to worry about it again.

The timing chain is not why it overheated though. I'd bet about anything your radiator looks similar to the one I posted. If you're in doubt, take the bottom hose off and look in there. The corrosion and gunk seems to be worse at the bottom and on the hot side of the radiator, but you have no way of seeing that. The right side of the picture I posted is the bottom of the hot side.

I haven't done it, but some of the guys here have and can tell you more about it. You may want to upgrade to Vortec heads. Having your old ones hot tanked and checked for cracks will be over $100. You can find ones at a junk yard, but you'll be paying to get them cleaned and checked. You can order new ones from Summit or Jegs.



Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
scrambldcj8 
Senior Member
Posts: 2352
scrambldcj8
Loc: MA
Reg: 04-06-03
06-06-18 05:07 AM - Post#2736125    
    In response to Sails941

  • Sails941 Said:

I'd love to put a crate engine in, but I can't stomach $4000 in labor for something I can do myself. And finding a location to do it while on the road is proving difficult.





I would just go at it as blown head gaskets at this point (and assess/replace as needed the timing chain). Agreed, you'll know more as you pull the heads.



 
1983G20Van 
Super Senior Member
Posts: 3706
1983G20Van
Loc: Bedford, Texas, USA
Reg: 11-13-02
06-06-18 07:15 PM - Post#2736198    
    In response to scrambldcj8

I hope it has not run so long as to erode the deck surface between the middle two cylinders. It is actually very common for these engines to blow the head gasket in those locations, especially the passenger side one. They will run and not leak a drop of coolant.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals


 
Sails941 
Poster
Posts: 9

Reg: 07-29-17
06-06-18 09:54 PM - Post#2736208    
    In response to 1983G20Van

Thank you to everyone. I need to ponder this a bit more and keep looking for a location to work on the van.
I will post an update.
Ken



 
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