Recent Topics
Walmart closing all Tire and Lube Express in Canada
by tenderloin - 06/03/20 10:38 AM
Seeking Exterior Home Aesthetic Advice (UPDATE!)
by DriveHard - 06/03/20 10:22 AM
Do you have your home HVAC system maintained?
by E150GT - 06/03/20 09:21 AM
Mixing vavoline & mobil
by ThePCMasterRace - 06/03/20 09:03 AM
Pre-Oiler?
by AJB0009 - 06/03/20 09:02 AM
1992 Acura NSX, Red Line 10W-30, ~1400 miles/1 year
by robertcope - 06/03/20 06:37 AM
Rural telephone boxes along road
by dlundblad - 06/03/20 05:06 AM
Mobil1 12 quart $30 at Walmart
by wkcars - 06/03/20 12:58 AM
"The Bright Knight"
by GumbyJarvis - 06/03/20 12:35 AM
Pennzoil Axle oil with LSA.
by Snagglefoot - 06/02/20 10:03 PM
Replaced the plugs on the bike: HUGE improvement!
by 14Accent - 06/02/20 09:26 PM
Accord Trans Case crack (bad casting?)
by redhat - 06/02/20 08:38 PM
Replacement SLA Battery for Clore Jumper
by SubLGT - 06/02/20 08:34 PM
ABS codes
by 2010Civic - 06/02/20 08:02 PM
Tie rod ends - which manufactures ok?
by jdw1222 - 06/02/20 07:40 PM
Who makes their own seltzer water?
by JLawrence08648 - 06/02/20 07:23 PM
Slight Tire Bulge
by coopns - 06/02/20 06:13 PM
Newest Members
boathead, Digital_Dad, RobertChapmant, NewMex, RandyN11049
71596 Registered Users
Who's Online Now
95 registered members (ABerns, 830Lee, 2010Civic, 53' Stude, 2015_PSD, 2009Edge, 9 invisible), 1,917 guests, and 38 spiders.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums67
Topics306,089
Posts5,287,208
Members71,596
Most Online4,538
Jan 20th, 2020
Donate to BITOG
Print Thread
Hop To
Page 1 of 2 1 2
GM 305 cleaning out... How should I proceed #5431184 05/17/20 08:43 AM
Joined: Mar 2009
Posts: 15
L
luca Offline OP
OP Offline
L
Joined: Mar 2009
Posts: 15
Ok so I have a 305 in my 22 year old GMC pickup truck. Overall the engine runs extremely well and only has 87,000 original miles. I plan on keeping it for a long time.

I did the lower intake manifold gaskets recently and when I had the intake manifold off the valley of the block was sludged up. I think part of that issue was coolant was getting in there which was most likely contributing to the issue. I very carefully cleaned what I could but didn't mess with any of the larger chunks since I didn't want that clogging up the oil pump.

I did an oil change with some semi synthetic castrol 5w30 and the lower end purolator filter with the plan to do an OCI at 500-1000 miles to get whatever gunk that was left over from the intake gasket replacement.

When I had the valve covers off to change the gaskets, the top of the heads/rockers looked really good with minimal carbon deposits. I was actually impressed with how clean it looked after 22 years of unknown OCI's.

Anyway I am wondering if I should do another very short OCI with cheap oil and filter or if i should get an oil that has more of cleaning detergents in there next (like PUP)

Re: GM 305 cleaning out... How should I proceed [Re: luca] #5431201 05/17/20 08:58 AM
Joined: Aug 2018
Posts: 295
M
mpack88 Offline
Offline
M
Joined: Aug 2018
Posts: 295
Since the top end looked good and you cleaned what you could in the valley pan I would run maybe a 10w30 or 15w40 diesel oil as they have more detergents. You could use a full synthetic but I wouldn't want anything to aggressive. I would drive it 3k making sure it got good and hot maybe change the filter inbetween changes. Check the pcv system to. I ran a 5w40 euro synthetic in my 30 year old truck with a 302 and it stopped my filter up in about 500 miles. Funny thing is I also had the intake and valve covers off and it looked fine to me. Not sure if the oil was to blame but that truck never has a synthetic in it before until I did it.

Re: GM 305 cleaning out... How should I proceed [Re: luca] #5431223 05/17/20 09:23 AM
Joined: Feb 2018
Posts: 883
B
BAJA_05 Offline
Offline
B
Joined: Feb 2018
Posts: 883
Cheap conventional oil like Super Tech 5W30 paired with a Super Tech filter and run it 1000 miles. Dont forget to treat your fuel system good also -- Chevron Techron Complete Fuel System Cleaner per instructions on bottle. wink


2017 VW Jetta SE TSI 1.4L Turbo (hers)
PP Euro 0W40 & FU (42K)
2008 Acura TL 3.2L PPHM 0W20 & FU (117K)
2005 Subaru Baja AWD 2.5L N/A 5spd.
T6 MV 5W30 & FU (103K)
2000 Ram 4X4 5.2L (93K) T6 MV 5W30 & FU
Re: GM 305 cleaning out... How should I proceed [Re: BAJA_05] #5431226 05/17/20 09:27 AM
Joined: Jun 2003
Posts: 20,846
C
Chris142 Offline
Offline
C
Joined: Jun 2003
Posts: 20,846
Originally Posted by BAJA_05
Cheap conventional oil like Super Tech 5W30 paired with a Super Tech filter and run it 1000 miles;)
x2. Warren makes great oils.

The 305 was known for it's v8 fuel economy with v6 performance!


02 Wrangler Napa high milage 10w40
87 F250 Valvoline 15w40
07 fjcruiser Car lube plus 10w30
Z400 castrol T 10w40
Can am Maveric edge 5w40
57 case tractor Chevron sae30
Re: GM 305 cleaning out... How should I proceed [Re: luca] #5431237 05/17/20 09:39 AM
Joined: Oct 2005
Posts: 5,545
D
DuckRyder Offline
Offline
D
Joined: Oct 2005
Posts: 5,545
Well, obviously you have no choice but to put a 383HT in it... grin2

Id run a couple of quick OCI 500-1000 miles with a high detergent oil and then call it good...

Rotella is cheap, Delo is cheap, M1 HM is cheap with rebates...

Last edited by DuckRyder; 05/17/20 09:59 AM.

Robert
  • 2019 Volkswagen Jetta R-Line
  • 1972 F100 Ranger XLT (445FE/C6/9” 3.50 Truetrac)
  • 2002 Ford Ranger XLT 4D Supercab 3.0L
Re: GM 305 cleaning out... How should I proceed [Re: luca] #5431250 05/17/20 09:51 AM
Joined: Sep 2019
Posts: 745
J
Jackson_Slugger Offline
Offline
J
Joined: Sep 2019
Posts: 745
I would use a cheap 5W-30 and Rislone for a full, but short, OCI of maybe 3K but keep an eye on it. The go with a quality syn on sale or with a rebate...

Re: GM 305 cleaning out... How should I proceed [Re: luca] #5431258 05/17/20 10:06 AM
Joined: Oct 2019
Posts: 123
B
buddylpal Offline
Offline
B
Joined: Oct 2019
Posts: 123
I’ve had plenty of 305 chevy’s in the past. They aren’t picky at all. I always ran 5w-30 which was specified in the owners manual but plenty of people use 10w-30. I always used synthetic M1 back then. I’m sure today’s conventional oils will be more than adequate at cleaning out your engine.

I have a soft spot for 305 chevy’s, the Chevy Caprice with the F41 suspension and performance axle definitely changed the whole feel of the car. The 305 wasn’t well loved by the enthusiast community but I will say there is a stark difference between the carburetor vs fuel injected versions. The fuellys had decent performance, although someone looking to add more power was better off with a 350. The tuned port injection engines offered decent power but the TPI was finicky at times and long term not reliable. The throttle body versions were dead reliable and they still function to this day. The TBI engines didn’t make as much power as the TPI but they still had more power than the carburetor ones. The later version 305 became part of the vortec family and they are pretty reliable too except for intake gasket failures and also fuel injection issues.


A couple GM's and a Hyundai.
Re: GM 305 cleaning out... How should I proceed [Re: luca] #5431301 05/17/20 11:01 AM
Joined: Jun 2014
Posts: 2,870
U
UncleDave Online Content
Online Content
U
Joined: Jun 2014
Posts: 2,870
If you are worried about it an interim low mile OCI/FCI with some delvac might clean a bit more (or " diesel oil" as previously mentioned)

If the top end looked good I wouldnt bother if it were - and didnt when it was mine.


As a gen Xer we got our licenses in the 80's and (at least my circles) drove really bad cars from the 70's.
We got the 150 hp v8s no one wanted, 305's 318's on 2 barrels.

Mine ground a lobe flat and I put an "RV" cam back in my 305 wagon and drove i all over the USA woke it up nicely. Towed a 23 t bucket using a VW tow bar from LA to Chicago and back across the Rockies - had plenty of snap even with a 3 speed.


UD


Uncle Dave
Cat 3126/2 MB3500/Titan/RX400H/17 Ridgeline
700HP V10/ 725HP BBC/ Raptor 700/ KFX450/ YZ250/Onan 8K/ Cat3011C
Re: GM 305 cleaning out... How should I proceed [Re: buddylpal] #5431311 05/17/20 11:19 AM
Joined: Jun 2003
Posts: 20,846
C
Chris142 Offline
Offline
C
Joined: Jun 2003
Posts: 20,846
Originally Posted by buddylpal
I’ve had plenty of 305 chevy’s in the past. They aren’t picky at all. I always ran 5w-30 which was specified in the owners manual but plenty of people use 10w-30. I always used synthetic M1 back then. I’m sure today’s conventional oils will be more than adequate at cleaning out your engine.

I have a soft spot for 305 chevy’s, the Chevy Caprice with the F41 suspension and performance axle definitely changed the whole feel of the car. The 305 wasn’t well loved by the enthusiast community but I will say there is a stark difference between the carburetor vs fuel injected versions. The fuellys had decent performance, although someone looking to add more power was better off with a 350. The tuned port injection engines offered decent power but the TPI was finicky at times and long term not reliable. The throttle body versions were dead reliable and they still function to this day. The TBI engines didn’t make as much power as the TPI but they still had more power than the carburetor ones. The later version 305 became part of the vortec family and they are pretty reliable too except for intake gasket failures and also fuel injection issues.


The early(mid to late 70's) had very soft blocks. The bores wore out quickly and caused oil burning. That is what started the dislike for them. A couple years ago I drove a 66 chevelle with a 305 and an edelbrock top end plus cam. Car had 3.31 gears and was very snappy and fun to drive. A 327 would have been even better.


02 Wrangler Napa high milage 10w40
87 F250 Valvoline 15w40
07 fjcruiser Car lube plus 10w30
Z400 castrol T 10w40
Can am Maveric edge 5w40
57 case tractor Chevron sae30
Re: GM 305 cleaning out... How should I proceed [Re: Chris142] #5431364 05/17/20 12:21 PM
Joined: Mar 2013
Posts: 6,792
S
skyactiv Offline
Offline
S
Joined: Mar 2013
Posts: 6,792
Originally Posted by Chris142
Originally Posted by buddylpal
I’ve had plenty of 305 chevy’s in the past. They aren’t picky at all. I always ran 5w-30 which was specified in the owners manual but plenty of people use 10w-30. I always used synthetic M1 back then. I’m sure today’s conventional oils will be more than adequate at cleaning out your engine.

I have a soft spot for 305 chevy’s, the Chevy Caprice with the F41 suspension and performance axle definitely changed the whole feel of the car. The 305 wasn’t well loved by the enthusiast community but I will say there is a stark difference between the carburetor vs fuel injected versions. The fuellys had decent performance, although someone looking to add more power was better off with a 350. The tuned port injection engines offered decent power but the TPI was finicky at times and long term not reliable. The throttle body versions were dead reliable and they still function to this day. The TBI engines didn’t make as much power as the TPI but they still had more power than the carburetor ones. The later version 305 became part of the vortec family and they are pretty reliable too except for intake gasket failures and also fuel injection issues.


The early(mid to late 70's) had very soft blocks. The bores wore out quickly and caused oil burning. That is what started the dislike for them. A couple years ago I drove a 66 chevelle with a 305 and an edelbrock top end plus cam. Car had 3.31 gears and was very snappy and fun to drive. A 327 would have been even better.


Why would someone drop a 305 in a 66' Chevelle?


Wife: 15' Audi A4 quattro 6 speed manual
Me: 18' Elantra Sport 6 speed manual
The rude guy that points out reality


Re: GM 305 cleaning out... How should I proceed [Re: UncleDave] #5431385 05/17/20 12:57 PM
Joined: Feb 2018
Posts: 883
B
BAJA_05 Offline
Offline
B
Joined: Feb 2018
Posts: 883
Originally Posted by UncleDave
If you are worried about it an interim low mile OCI/FCI with some delvac might clean a bit more (or " diesel oil" as previously mentioned)

If the top end looked good I wouldnt bother if it were - and didnt when it was mine.


As a gen Xer we got our licenses in the 80's and (at least my circles) drove really bad cars from the 70's.
We got the 150 hp v8s no one wanted, 305's 318's on 2 barrels.

Mine ground a lobe flat and I put an "RV" cam back in my 305 wagon and drove i all over the USA woke it up nicely. Towed a 23 t bucket using a VW tow bar from LA to Chicago and back across the Rockies - had plenty of snap even with a 3 speed.


UD


ANYDAY I would take a 318/5.2L over a 305 in the trucks back then. NOT EVEN comparable!!!! When the 305s were put in the Monte SS and Camaro I Roc Zs in 87 -- then the 305 was relevant.


2017 VW Jetta SE TSI 1.4L Turbo (hers)
PP Euro 0W40 & FU (42K)
2008 Acura TL 3.2L PPHM 0W20 & FU (117K)
2005 Subaru Baja AWD 2.5L N/A 5spd.
T6 MV 5W30 & FU (103K)
2000 Ram 4X4 5.2L (93K) T6 MV 5W30 & FU
Re: GM 305 cleaning out... How should I proceed [Re: BAJA_05] #5431434 05/17/20 01:57 PM
Joined: Jun 2012
Posts: 591
W
wolf_06 Offline
Offline
W
Joined: Jun 2012
Posts: 591
I had a 1990 Chevrolet Caprice, bought brand new from my dad, then he gave it to me.

That 305 was the "non HO", so was 170 hp and 255 lbs of torque. Very durable and robust engine, very good fuel economy as well. Mine was the fuel injected 305.

My father ran strictly a diet of Castrol GTX 5w30 or 10w30 for summer, and every two oil change after 100k km, he would add 1/2 a bottle of Wynns Stop Leak, even tho the engine was leaking no oil, as a preventive maintenance.

I drove that car till it reached 385,000 km, no smoke, same oil usage since new, about 1/2 a quart every 5,000 km. Ran like brand new basically.

Then we sold it to a guy, he drove it for another 150,000 km trouble free.

I was young when I had it, beat the heck out of it, never had problems.

So 500,000 ++++ km on regular oil. A good conventional should be fine.


2018 Mazda 3 GS 2.0 Skyactiv 6AT
Petro Canada Full Syn 0w20 + OEM filter
Re: GM 305 cleaning out... How should I proceed [Re: wolf_06] #5431438 05/17/20 02:01 PM
Joined: Dec 2005
Posts: 1,703
C
caprice_2nv Online Content
Online Content
C
Joined: Dec 2005
Posts: 1,703
Originally Posted by wolf_06
I had a 1990 Chevrolet Caprice, bought brand new from my dad, then he gave it to me.

That 305 was the "non HO", so was 170 hp and 255 lbs of torque. Very durable and robust engine, very good fuel economy as well. Mine was the fuel injected 305.

My father ran strictly a diet of Castrol GTX 5w30 or 10w30 for summer, and every two oil change after 100k km, he would add 1/2 a bottle of Wynns Stop Leak, even tho the engine was leaking no oil, as a preventive maintenance.

I drove that car till it reached 385,000 km, no smoke, same oil usage since new, about 1/2 a quart every 5,000 km. Ran like brand new basically.

Then we sold it to a guy, he drove it for another 150,000 km trouble free.

I was young when I had it, beat the heck out of it, never had problems.

So 500,000 ++++ km on regular oil. A good conventional should be fine.

I got 535,000kms (335k miles) from my 89 Caprice. It ran like new still, smoothest engine I've had, but used some oil, didn't get great mileage anymore and the body and frame rusted out.

My current one an 83 only has 240k miles. Runs good but has some piston slap when cold and needs valve seals (installing a catalyst got rid of the symptoms of that), uses very little oil.


84 Olds Cutlass - 350 Olds
83 Chevy Caprice - 305 Sbc
05 Silverado 1500 4wd - 4.8/4L60E
79 Honda CX500
Re: GM 305 cleaning out... How should I proceed [Re: caprice_2nv] #5431444 05/17/20 02:06 PM
Joined: Jun 2012
Posts: 591
W
wolf_06 Offline
Offline
W
Joined: Jun 2012
Posts: 591
Originally Posted by caprice_2nv
Originally Posted by wolf_06
I had a 1990 Chevrolet Caprice, bought brand new from my dad, then he gave it to me.

That 305 was the "non HO", so was 170 hp and 255 lbs of torque. Very durable and robust engine, very good fuel economy as well. Mine was the fuel injected 305.

My father ran strictly a diet of Castrol GTX 5w30 or 10w30 for summer, and every two oil change after 100k km, he would add 1/2 a bottle of Wynns Stop Leak, even tho the engine was leaking no oil, as a preventive maintenance.

I drove that car till it reached 385,000 km, no smoke, same oil usage since new, about 1/2 a quart every 5,000 km. Ran like brand new basically.

Then we sold it to a guy, he drove it for another 150,000 km trouble free.

I was young when I had it, beat the heck out of it, never had problems.

So 500,000 ++++ km on regular oil. A good conventional should be fine.

I got 535,000kms (335k miles) from my 89 Caprice. It ran like new still, smoothest engine I've had, but used some oil, didn't get great mileage anymore and the body and frame rusted out.

My current one an 83 only has 240k miles. Runs good but has some piston slap when cold and needs valve seals (installing a catalyst got rid of the symptoms of that), uses very little oil.


Yeah my dad had an 84, piston slap since new, never had a problem, just a slap. I cant remember if he had it fixed or not. I think it was on cold startup.


2018 Mazda 3 GS 2.0 Skyactiv 6AT
Petro Canada Full Syn 0w20 + OEM filter
Re: GM 305 cleaning out... How should I proceed [Re: luca] #5431458 05/17/20 02:21 PM
Joined: Mar 2009
Posts: 15
L
luca Offline OP
OP Offline
L
Joined: Mar 2009
Posts: 15
I will stick with the cheap oil and filter and low mileage OCI's. thanks!

BTW - Not looking to hot rod anything. It's just my Home Depot truck. It runs great as is and I am happy with it. I did upgrade the fuel injection module to the MPFI unit which made a big difference.

Page 1 of 2 1 2
Previous Thread
Index
Next Thread

BOB IS THE OIL GUY® Powered by UBB.threads™