compression question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

86SILVERADO · 05-30-2003, 10:09 PM

Just got a 72 with a 350 it sat for almost ten years but I got it running after I replaced all the gummed up fuel lines. It runs great but I did a compression test on it and #2 was at 125 and #7 was at 135 all other cylinders were right at 150. put oil in cylinders and compression jumped right up so it is the rings. Is it possible that having sat for so long the cylinders or rings might just have some surface rust and rings might re-seat after driving a bit, or not. How bad is 25 psi off anyway, it says in the book that they should be no more than 20 off and this is only an extra five after all. Any experience with lower compression and how long the engine lasted would be appreciated. Thanks

Norris

CT-Truckster · 05-30-2003, 10:14 PM

does it smoke or have lotsa blowby,

86SILVERADO · 05-30-2003, 10:26 PM

smokes a tad while running. Just a very faint blue haze. I know it is burning some oil in those cylinders I was just wondering if there is any chance it would clear up. Main reason is I am thinking of pulling this motor and putting it in another driver I have because the truck it is in is just to far gone.

solidaxel · 05-31-2003, 02:17 PM

Drive it like you stole it!!!!!! and when it won't run anymore then replace the engine.

82 Silverado 4X · 05-31-2003, 05:18 PM

Could just be a couple of frozen rings from sitting. If the smoking goes away after a couple of days of driving you can recheck your compression to see if it came back up. If the smoking never stops you could either rebuild or replace the engine.

Tom · 05-31-2003, 07:53 PM

No way to tell except drive it and see what happens. I would take it on a good 1hr long freeway trip, and if that dosent help then put some new rings in it.

86SILVERADO · 06-01-2003, 03:22 PM

Thanks for the replies. I probably will drive it and see if it clears up. Thanks,

Norris

05-30-2003, 10:09 PM	#1
86SILVERADO Registered User Join Date: Dec 2002 Location: Hills of Western Mass Posts: 626	compression question Just got a 72 with a 350 it sat for almost ten years but I got it running after I replaced all the gummed up fuel lines. It runs great but I did a compression test on it and #2 was at 125 and #7 was at 135 all other cylinders were right at 150. put oil in cylinders and compression jumped right up so it is the rings. Is it possible that having sat for so long the cylinders or rings might just have some surface rust and rings might re-seat after driving a bit, or not. How bad is 25 psi off anyway, it says in the book that they should be no more than 20 off and this is only an extra five after all. Any experience with lower compression and how long the engine lasted would be appreciated. Thanks Norris

05-31-2003, 02:17 PM	#4
solidaxel Registered User Join Date: Dec 2002 Location: Cactus Patch So. Az Posts: 4,749	Drive it like you stole it!!!!!! and when it won't run anymore then replace the engine. __________________ 53 TuTone Extended Cab 350 4-Spd 3:08 (SOLD) 53 Chevy Moldy pearl green ZZ-4 4L60E 9" 3:25 55 GMC 1st Black Mll (ZZ4) ZZ6 TKO 600 5 sp 3:73 62 Solidaxle Corvette Roman Red (327 340hp 4spd 3:36) C4 & C5 suspension tube chassis LS 3 4L70E 65 Corvette Coupe 327 350hp 4spd 4:11 78 Black Silverado SWB (350/350) 5.3 & 4L60E 3:42 2000 S-Type 3.0 (wife cruiser) 2003 GMC SCSB 5.3 4L60E 3:42

05-31-2003, 05:18 PM	#5
82 Silverado 4X Genuine Chevrolet Join Date: Feb 2003 Location: South West Pennsylvania. Posts: 582	Could just be a couple of frozen rings from sitting. If the smoking goes away after a couple of days of driving you can recheck your compression to see if it came back up. If the smoking never stops you could either rebuild or replace the engine. __________________ George 82 Silverado LWB 4x4 350 SM465 NP208 77 Chevrolet Blazer Chalet 400 TH350 NP203

05-31-2003, 07:53 PM	#6
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,720	No way to tell except drive it and see what happens. I would take it on a good 1hr long freeway trip, and if that dosent help then put some new rings in it. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

05-30-2003, 10:14 PM	#2
CT-Truckster ? Join Date: Jul 2002 Location: Dyersburg, TN Posts: 471	does it smoke or have lotsa blowby,

05-30-2003, 10:26 PM	#3
86SILVERADO Registered User Join Date: Dec 2002 Location: Hills of Western Mass Posts: 626	smokes a tad while running. Just a very faint blue haze. I know it is burning some oil in those cylinders I was just wondering if there is any chance it would clear up. Main reason is I am thinking of pulling this motor and putting it in another driver I have because the truck it is in is just to far gone.

06-01-2003, 03:22 PM	#7
86SILVERADO Registered User Join Date: Dec 2002 Location: Hills of Western Mass Posts: 626	Thanks for the replies. I probably will drive it and see if it clears up. Thanks, Norris __________________ 86 Silverado C10 back to 305 power! 67 C30 Dually Dump, with 350 transplant, Rockhauler 05 Duramax 3500 "If at first you don't succeed, try a bigger hammer" Member of the 1-Ton club!



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