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Username Post: 85 g20 engine problems        (Topic#367013)
Maninthevan 
Newbie
Posts: 4

Reg: 11-21-21
11-21-21 07:27 PM - Post#2831254    

Hey there everyone. New to the site and wanted to hop on and see if can find some guidance with issues im having.

I've had this van for almost three years, put about 30,000 on her since then and she's finally starting to scare me with some engine issues.

Long story short, its been consistently losing power, burning oil at idle, occasional misfire, and I can hear some valves clacking.

I put a vacuum gauge on the manifold, and there's a steady 5mm drop and rise. Im suspecting a bad valve, but hoping its just the valve seal. Im going to get her in a shop and get diagnosed asap but I wanted to come here and see what some of my options are.

Its got 174,000 on it. Im thinking if its just the seal, this is a job I can handle for sure. If its a burnt valve, I'm somewhat confident I can pull the head and have it resurfaced. Im just wondering, with so many miles, is this worth it? The 305 and three speed transmission is pretty underpowered for this beast, but I can't afford a new engine and trans with shop costs. No way.

Its a full conversion with a high top that I live in. Im currently in Arizona near Lake havasu. It still runs so I can get it to town, but its starting to run rough and can't be pushed much longer.

Any advice or reality checks are welcome.



 
wagonman100 
Site Ambassador
Posts: 15412

Loc: Baltimore, MD
Reg: 11-27-04
11-21-21 08:33 PM - Post#2831260    
    In response to Maninthevan

Hard to say for certain. I know my co-worker had a 305 in his truck and the oil drain back holes in the heads got gummed up and the oil could not drain back fast enough and build up in the heads. The result was leakage past the valve seals causing it to smoke. It didn’t get to the point of misfiring before he took care of it, but I suppose it could have gotten to that point. And if the oil isn’t draining back to the pan the lifters will not get enough oil and start to clack. It could also cause erratic valve lift which would give erratic vacuum readings and loss of power. Carbon buildup on the valve seats can also cause some of these problems as can a broken valve spring.

Jay
Friends don’t let friends drive Fords.

1999 Silverado Z71 4X4 extra-cab short bed
1983 Malibu Fauxmad - tubbed
1978 El Camino Kustomized
1972 Monte Carlo
1957 210 handyman wagon
1957 Nomad sport wagon
1957 Cameo Carrier


 
gchemist 
Member #271 Senior Chevytalk Moderator
Posts: 25603
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-22-21 12:07 PM - Post#2831277    
    In response to wagonman100

Welcome to the site. Replace the timing chain with any work done! The nylon timing gears will crack eventually. When they do, the chain will strip the cam gear teeth. It happened to my 305. Broke the cam in half. Old valve stems will burn oil. Valve clatter is another sign of worn timing gears. It's hard to say until you open it up.

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles
'08 GMC Acadia 3.6L SLE


 
Maninthevan 
Newbie
Posts: 4

Reg: 11-21-21
11-22-21 04:00 PM - Post#2831290    
    In response to Maninthevan

I will be getting an in shop diagnostic tomorrow. Lucky to get a slot so quickly. Basically realized I will be chasing white rabbits trying to diagnose this myself with the tools I have. Hoping there will be an affordable fix :fingers crossed:



 
Maninthevan 
Newbie
Posts: 4

Reg: 11-21-21
11-23-21 03:20 PM - Post#2831347    
    In response to gchemist

Well the shop i took it to wanted to charge me 240 for a compression test. I said no way and did it myself. Looks like a bad intake or exhaust valve. I have no means of performing a leak down test. Currently camped on blm land near Lake havasu az.

Not sure what to do next here.

Cylinder...

1.) 160
2.) 175
3.) 130
4.) 165
5.) 120
6.) 155
7.) 155
8.) 0 dry and wet

There is visible oil leaking from cylinder 8 around the valve cover. Not quite sure where from, its splattered. The spark plug was totally gunned up. Spark plug from cylinder 5 looked melted or zapped with a noticeable chunk missing from ceramic housing. Spark plug from cylinder one was gunned within the gap.





 
Shepherd 
Frequent Contributor
Posts: 2377

Loc: Lake George, NY
Reg: 11-11-15
11-24-21 10:43 AM - Post#2831397    
    In response to Maninthevan

Gotta take the head off for any further diagnosis or fix.



 
Maninthevan 
Newbie
Posts: 4

Reg: 11-21-21
11-29-21 12:37 PM - Post#2831568    
    In response to Shepherd

So at this point, I need to decide whether its worth it to pull the head or start looking for a new engine. I adjusted the valves and ran some top end cleaner through the carb as a last ditch effort to see if it was maybe a stuck valve. Its burning a lot less oil, but still smoking when I open the throttle. I'm going to run compression on all low cylinders (8,3,5) again to see if this actually changed anything.

The engine sounds good, much better than before,, and if I were to pull the head, I'm thinking of just pulling the side with the dead compression and having it machined with new seals. This would be my cheapest option at this point, but am I just waisting time when a full overhaul is needed here?



 
gchemist 
Member #271 Senior Chevytalk Moderator
Posts: 25603
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-30-21 04:17 AM - Post#2831593    
    In response to Maninthevan

It's a lot of miles. Do you plan to keep it a long time? If so, I would plan an engine upgrade. Time and money put into the old block can be used for upgrades. Valve stem seals will reduce oil smoke for a while. New head gaskets may help. Taking the heads off make it easier to remove the block if necessary. Have a plan for a new engine incase the engine is toast. Having a plan will save you down time on driving it.

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles
'08 GMC Acadia 3.6L SLE


 
gchemist 
Member #271 Senior Chevytalk Moderator
Posts: 25603
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-30-21 04:23 AM - Post#2831594    
    In response to gchemist

Filling up yesterday, this van was next to me. Wish I had time to talk to the owner. It was dark and cold. It would've been nice to look under the hood. The engine exhaust was nice and steady.

Attachment: van.jpg (60.6 KB) 2 View(s)




'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles
'08 GMC Acadia 3.6L SLE


 
Mercedes 
Contributor
Posts: 544

Reg: 07-09-18
11-30-21 07:59 AM - Post#2831606    
    In response to Maninthevan

My advice is to pull the engine and replace it with a rebuilt unit, or rebuild that one yourself. After 36 years and 174k miles, it is totally shot.

I'd also suggest going with a 350 instead of a 305. Everything will bolt up just fine and you'll have to play with your carburetor or swap it out for a carb with increased airflow.



 
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