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#1 |
Registered User
Join Date: Mar 2007
Location: San Pedro River, SE Arizona
Posts: 734
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Help[ !! What happened here?
I just experienced an unusual event with the engine of one of my old Chev trucks (‘71 C20/SB350) and am thinking that some of you may have had, or heard about, the same kind of thing. Before I start in to diagnose and fix the problem, I would like to benefit from your knowledge/experience.
As background and with the thought that many of you have experienced the bad outcomes of ethanol sitting in our gas tanks and fuel lines, due to a prolonged recovery from a health matter I was not able to run most of my trucks for quite a while. So, then spent a lot of time and effort – and some $ - dealing with the corrosion/particles formed due to ethanol absorbed moisture in the OE fuel tanks and collected in fuel filters and carbs, not to mention damage to fuel lines, fuel pumps, etc.. I have been moving my trucks to a new home and this was the final one – 250 mile drive from rather high elevation to desert - and all went just fine for the initial 150 miles from cool morning to mid-day 95+ degree temps. Engine running easy/quiet with excellent output (pulling a 1500 lb. trailer) – and normal amps/temp/oil pressure. Periodic stops to check the loads, hitches, tires, etc. showed zero leaks or problems. But, the fuel gauge seemed to be dropping more than expected. After a short stop at a rest area and then running about 10 minutes at 60 mph on an interstate, the trailing partner on radio saw a sizable puff of blue smoke from under my truck which then tapered away, and also smelled something like petro burning – and I smelled the same thing. Oil pressure dropped slightly. Stopped at the first good opportunity and found plenty of oil on the pass side of engine and dripping from the frame – level on dipstick slightly below “add” and dipstick holder out of its hole in the block. Oil leak seems to be coming from the joint between oil pan and block in middle of pass side of engine. I am figuring a blown gasket there. After adding oil and trying to drive it a bit further (good oil pressure), a stop to check showed continued leaking. Hauled the whole rig home on a 40 ft. trailer. Now – please evaluate my guesswork and/or tell me your diagnosis before I tackle the job. I think that ethanol damage had caused an opening in the diaphragm of the fuel pump and that it was pumping fuel into the crankcase and, after accumulation of fuel and heat in there, a sudden flaming or explosion caused the blowout of the dipstick holder and pan gasket – and the escaping blue smoke. Or??? Thanks in advance for any replies/advice.
__________________
CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp |
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#2 |
Senior Member
![]() Join Date: Apr 2016
Location: Cypress, TX
Posts: 3,703
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Re: Help[ !! What happened here?
I like your guesswork, it seems like a good theory to me.
As for your Or? question, you could just have a combination of gasket leaking oil (could be somewhere besides oil pan gasket, such as valve cover gasket), and a rich condition and backfire because of crud stuck in the carburetor's needle and seat. I suppose the fuel pump would be pretty easy to remove and look at. I got mine from Autozone for about $20, it is Delphi and has lasted a couple of years so far. The only reason I changed it is because I physically damaged it, not because the diaphragm blew. Drain some your oil and see if it smells like gas. I have heard that letting them sit makes them go bad when they are sitting with gasohol in them. I wonder if that is true. i've always used gasohol and not had problems, but mine is a daily driver. If I had one of these trucks that I mostly stored and didn't drive often, I would probably try to use non-ethanol gas in the last tank before storage, or if that was not an option at the gas station because of where you live, run the truck completely out of gas or drain it and restart it with a quart or 2 of the fancy Trufuel 4-cycle gas that you can get in Lowes or Home Depot in cans (roughly $6/quart). |
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#3 |
Registered User
Join Date: Jan 2016
Location: Barber City, CA
Posts: 4,781
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Re: Help[ !! What happened here?
PCV valve stuck closed
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I started out with nothing - and I still have most of it |
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#4 |
Senior Member
![]() Join Date: Apr 2016
Location: Cypress, TX
Posts: 3,703
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Re: Help[ !! What happened here?
Killer Bee, would the PCV valve stuck also need to be combined with the breather tube or breather filter clogged to cause a malfunction? Just curious.
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#5 |
Registered User
Join Date: Mar 2007
Location: San Pedro River, SE Arizona
Posts: 734
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Re: Help[ !! What happened here?
Thanks for the thoughts so far. PCV valve is clear and functioning. No oil leaking from under valve rocker covers - but one visible leak/stream from top of crankcase pan running down the side. It was hot under there on the roadside yesterday and the dripping oil seemed somewhat thinner than it should have been, and oil on dipstick has some gas smell. I'm wondering if gas-thinned oil did a good enough lube job on the various bearings/surfaces while this was happening.
I now go to great lengths to keep non-ethanol fuel in all of the old Chevs/GMC now - went through a bunch of fixes on almost every one after they sat with ethanol in them. Quite vexing. Any other thoughts out there about cause?
__________________
CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp |
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#6 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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From your own words high elevation to desert sounds like your carburetor will need adjusting for the difference in the elevation change maybe.
Does the gas you use have something to do with it, yes. Pulling a trailer also added to it. ![]()
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#7 |
Registered User
Join Date: Mar 2007
Location: San Pedro River, SE Arizona
Posts: 734
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Re: Help[ !! What happened here?
Ordinarily, I adjust idle mixture to compensate for such change in elevation - but usually do not have to adjust for air available at driving speeds. If that is needed, a change of jet size can be done. And, timing advance may need attention. However, none of the above seems at all related to the described surprise, nor does the trailer.
__________________
CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp |
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#8 |
Registered User
![]() Join Date: Aug 2019
Location: Cheraw
Posts: 1,305
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Re: Help[ !! What happened here?
Take an oil sample in and have it analyzed. That will tell you if there is gas in the oil. I would change your oil anyway to be on the safe side.
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#9 |
Registered User
![]() Join Date: Aug 2019
Location: Cheraw
Posts: 1,305
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Re: Help[ !! What happened here?
In the 70's I had an engine blow up because of gas in the oil. The farmer said it wouldn't start but didn't give me the whole story. I charged the battery and changed the points. Pow!
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#10 |
Registered User
Join Date: Mar 2007
Location: San Pedro River, SE Arizona
Posts: 734
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Re: Help[ !! What happened here?
It will be a day or two before I can get this truck on the lift to work on it because another truck (69 Longhorn) is sitting in the way waiting for me to finish rebuilding the Holley 4bbl for it. I plan to drain and analyze the contents of the crank case, remove the pan and be prepared to replace the pan gasket which looks to be blown out in the middle of the pass side of the engine. As much as I am able, will try to determine if any damage has been done to the lower end by the ostensible "explosion" or due to running with motor oil diluted by gasoline. I hope the findings are pleasant because this is a really nice truck with a very solid 350. Also will change the fuel filter and replace the fuel pump before cranking it up again.
Thanks to those who posted thoughts. Actually, I am somewhat surprised that more folks here have not experienced or heard of such an issue - but maybe some have not read the thread. Thanks again.
__________________
CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp |
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#11 |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,487
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Re: Help[ !! What happened here?
-
I once had a problem with gas entering the crankcase and exploding in the pan. It actually killed the engine with a big puff of blue smoke, but I was only going about 20mph at the time. It started back up and I drove it to a friends house close by. It ended up I had a hole in one of the pistons and gas was getting into the crankcase through that. It actually deformed the pan between each pan bolt and I had to rebuild the engine and replace the pan. I would do a compression check first off..... LockDoc
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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
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#12 |
Registered User
Join Date: Jul 2009
Location: Space Coast, Fl.
Posts: 1,050
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Re: Help[ !! What happened here?
Sounds like your "blown out" pan gasket is beyond help... but awhile back I had a bad pan rail oil leak on my Nova. A smart guy I know sealed the breather openings on the valve covers and the dipstick tube with duct tape. At the leak point he loosened 3 bolts on the pan rail and hooked a vacuum pump into one of the breather holes in a valve cover. He put a dab of RTV at the leak point on the pan rail/oil pan and it sucked the sealer into the gap. Tightened the bolts and cured my leak. Ran the car that night & busted the case on the powerglide. I've never had good no leak success changing pan gaskets in the veh. I've had 'em leak installed upside down on an engine stand.
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Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!! |
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