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Chevy 350 oil pressure


broughy84
12-12-2004, 06:16 PM
Okay, I don't proclaim to be an automotive guru, but I think I know alot about automotives, anyway. Today I took the oil pressure sending switch out of my 1988 Chevy C1500 Silverado, 350 / 700R4, and replaced it a manual gauge. I left the original wiring there, but unplugged. (You see I have been having trouble with the acuracy of the electric gauge, and I didn't have the money to buy a sending unit and I already had a good add on gauge) ANYWAY. I think I know alot about this truck, but I drove it this evening and BOTH gauges worked. Is there another sending unit on this truck? Did I screw up? It runs okay. I took the sending unit off the top of the block. Everyone should be proud of me too....I pulled the distributor out today and put it all back together in perfect TIME!!!

BTW

All you folks with a 5.7L TBI (350ci, throttle body fuel injection) What are your oil pressure readings at:

Hot Idle in gear?
Hot Idle in Neutral?
Running about 60mph down the Highway?

Mine are

12-15 psi
20 psi
35 psi

Sound about normal???

1979Lee
12-12-2004, 06:45 PM
Okay, I don't proclaim to be an automotive guru, but I think I know alot about automotives, anyway. Today I took the oil pressure sending switch out of my 1988 Chevy C1500 Silverado, 350 / 700R4, and replaced it a manual gauge. I left the original wiring there, but unplugged. (You see I have been having trouble with the acuracy of the electric gauge, and I didn't have the money to buy a sending unit and I already had a good add on gauge) ANYWAY. I think I know alot about this truck, but I drove it this evening and BOTH gauges worked. Is there another sending unit on this truck? Did I screw up? It runs okay. I took the sending unit off the top of the block. Everyone should be proud of me too....I pulled the distributor out today and put it all back together in perfect TIME!!!

BTW

All you folks with a 5.7L TBI (350ci, throttle body fuel injection) What are your oil pressure readings at:

Hot Idle in gear?
Hot Idle in Neutral?
Running about 60mph down the Highway?

Mine are

12-15 psi
20 psi
35 psi

Sound about normal???



those psi numbers look normal
they are very close to my 90 gmc 350 tbi 700r4 truck 125K
good job getting the distributor back in they can be difficult at times! :banghead:

when i bought my truck it had a manual guage under the hood and had the in dash one as well,the last owner said the dash guage was broken for a while but he fixed it and just left the under hood one hooked up.
the under hood one was hooked up just above the oil filter you know on the side of the block about 1 to 2 inches above the filter.

any way hope this helps!!!


oh by the way how is your 700r4 tranny holding up with 151k?

my 700r4 125k still works ok planetary gears are a little loud , fluid no burt smell ,clean fluid

do you know how long these trannys go before a rebuild will be needed?
i try to go easy on this truck try to make it last longer.

thannks in advance :lol2:

broughy84
12-12-2004, 09:58 PM
My first one went out at 95k, then the second went out at 147k, but this was a MUNICIPALLY OWNED VEHCILE before I bought it, so it was RUN HARD. I am on my third tranny it is used out of an Astro van, it has about 110k on it. No slippage or anything, planetary gears a little loud, common complaint, but nothing out of the ordinary though.

Yeah I was tickled pink when the distributor dropped right in !!!!

1979Lee
12-12-2004, 11:58 PM
My first one went out at 95k, then the second went out at 147k, but this was a MUNICIPALLY OWNED VEHCILE before I bought it, so it was RUN HARD. I am on my third tranny it is used out of an Astro van, it has about 110k on it. No slippage or anything, planetary gears a little loud, common complaint, but nothing out of the ordinary though.

Yeah I was tickled pink when the distributor dropped right in !!!!

Makes me wonder about my transmission now.
At least now I know that the planetary gears noise complaints are common .
Hope my tranny will last quite a bit longer.

Thanks and good luck with your truck.

Cam7
12-13-2004, 04:56 AM
If yyou replace the Trans you need to stay in the 88- 91 years because of the ABS sensor ring in the output shaft of the TRans. Other wise No ABS. The 88-91 ABS system works out of the Trans not the Diff. Found out when going to do Tranny swap from a earlier Trans.

sitdusa
12-13-2004, 06:24 AM
Mine are as follows but I only have 10,000 miles on the new engine...


Hot idle 20 psi
Runnign 70 mph 41-43 psi

broughy84
12-13-2004, 12:49 PM
Thanks to everyone....yes I found out about the ABS when i changed to this one. It had the mechanical speedo, not the speed sensor. Had the tranny shop change the tail shaft. Not a problem now.

BoatCop
12-17-2004, 05:56 PM
'96 Sierra X-cab
350 CI Vortex
111.000 miles
Air-Hog Filter

Idle cold - 40+
Idle warm - 20 +/- No diff. in or out of gear
60 MPH cold 50+
60 MPH warm 42

No problems whatsoever with the tranny.

Replaced A/C Compressor @ 65,000
Replaced water pump @ 91,000
Replaced Alternator @ 95,000

Fuel gauge is whacky - Full tank - needle is WAY past the "F" mark. Starts cutting out around 1/2 tank - takes 20+ gals at this point
Fuel pump went and was dealer replaced @ about 82,000 miles. This was when the gauge problem started.

If that's all the problem I have, I can live with it.:loser:

skipr
12-18-2004, 11:56 AM
If yyou replace the Trans you need to stay in the 88- 91 years because of the ABS sensor ring in the output shaft of the TRans. Other wise No ABS. The 88-91 ABS system works out of the Trans not the Diff. Found out when going to do Tranny swap from a earlier Trans.
There's another reason why your right about getting a trans above 1988. The pump behind the torque convert. in the first overdrive hydromatic's where causing trans failure at 50,000 or less in alot of cars prior to 1988 (they redesigned after 87).

LT-Z71drvr
12-20-2004, 10:34 PM
On my 96...

Hot Idle-35
Hot Cruise-45

I was worried about this the first time I ran the truck, but I guess its normal. My Silverado I had much more than this.

Fireplug
12-21-2004, 10:32 AM
A Good rule to live by .
10 psi oil pressure per 1,000 rpm

broughy84
12-21-2004, 10:39 PM
okay, that make sense.....I'm okay then. Hell even If I wasn't I'd drive it till i blows up!!!

tbranscom
12-30-2004, 11:56 PM
so if im idling in my 99 tahoe at 700rpm its ok fot it to be at 7lb pressure? stays about 20 at crusing speed and high 30's whenin im acelarating... i also have the problem of starting cold it knoces for a second before the psi builds.. i have it parkrd now becouse im scard to drive it. i just spent a ton on rebuilding the bottom end crankkit, oil pump rod and main bearrings. i scard somthing went wrong. when i did the initalk oit i used 10 40 o ran it for 3 days and changed over to 5 30 synthetic seems i have lower psi with the sinthetic... what do you guys think? my psi did drop low enough at the drive through for the check guages light to come on.. didnt catch its low point but it made no noises. taho runs great no noise after startup... any help?

chevytrucks92
12-31-2004, 12:05 AM
so if im idling in my 99 tahoe at 700rpm its ok fot it to be at 7lb pressure? stays about 20 at crusing speed and high 30's whenin im acelarating... i also have the problem of starting cold it knoces for a second before the psi builds.. i have it parkrd now becouse im scard to drive it. i just spent a ton on rebuilding the bottom end crankkit, oil pump rod and main bearrings. i scard somthing went wrong. when i did the initalk oit i used 10 40 o ran it for 3 days and changed over to 5 30 synthetic seems i have lower psi with the sinthetic... what do you guys think? my psi did drop low enough at the drive through for the check guages light to come on.. didnt catch its low point but it made no noises. taho runs great no noise after startup... any help?

Well, it should most def. do better then that. After reading the first part of your post, I was about to say need new bearings, becuase that is a dead give away when your pressure is slow to build.

Synthetic is thinner, so this may or may not be the problem. I do know you're supposed to run conventional oil in the engine for a little longer then 3 or 4 days though, lol. I'd alteast go one oil change on conventional oil before switching.

Did you have this oil pressure problem on the 10w40 oil?

chevytrucks92
12-31-2004, 12:16 AM
I believe you're OK with your oil pressure.

My 92 350 TBI on Valvoline MaxLife 10w30 oil pressure is like this:

190 degrees, in gear holding the brake: 15-20 psi
190 degrees @ 60 mph: 30-35 psi
190 degrees, in park: 30 psi
start up: 45 psi (give or take 5 psi, mainly depends on the weather)

Also, that 190 degrees is pretty accurate, becuase I have a manual water temp. guage. My factory guage (when hooked up) varies from 220-240, lol, so yeah, it def. is messed up, and like you, I dont have the money to go spend $300+ on a new cluster (which is what you have to buy for my truck). I did replace the sending unit, water pump, and thermostat when the problem developed, but it turned out to be the guage itself.

Back to the oil pressure, my truck usually stays about a small mark or two above 30 psi at cruising speeds, and usually drops anywhere to 15 to a small mark or two above 15 psi when in gear holding the brake (like at a drive thru), and when in park (and I assume nuetral) usually stays either right at 30 psi or a small mark below it.

I shoudl say my truck has guages with needles, and not with the little slide deal that yours has. My dad's 91 though has the same cluster as yours, and it usually runs about what mine does, maybe just a hair higher, but he usues Valvoline MaxLife 10w40.

roonie
12-31-2004, 12:21 AM
mine reads over 200.........kps that is.up in Canada..........EH!!! what would that conversion be anyway?

tbranscom
12-31-2004, 08:32 AM
Well, it should most def. do better then that. After reading the first part of your post, I was about to say need new bearings, becuase that is a dead give away when your pressure is slow to build.

Synthetic is thinner, so this may or may not be the problem. I do know you're supposed to run conventional oil in the engine for a little longer then 3 or 4 days though, lol. I'd alteast go one oil change on conventional oil before switching.

Did you have this oil pressure problem on the 10w40 oil?

no when i had the 10-30 in it idled at 20 and then 40psi on accelaration. but it still had the cold start knock. also the motor had been neglected of oil nges and the pan was full of sludge, the dealer had tried to flush the motor. withch removed the sludge, but its my guess thats probably what wiped the crank and bearings out also. i had someone tell me that the external oil coler couold be clogged up, would this slow my oil pressure down at at sratup?

so this weekend ill change it back to regular oil do i go with 5 or 10 weight?

Fireplug
12-31-2004, 10:05 AM
New bottom end and only 7 psi at 700 rpm boy there is something screwed up there. I would not run that engine to much.

chevytrucks92
12-31-2004, 11:21 PM
no when i had the 10-30 in it idled at 20 and then 40psi on accelaration. but it still had the cold start knock. also the motor had been neglected of oil nges and the pan was full of sludge, the dealer had tried to flush the motor. withch removed the sludge, but its my guess thats probably what wiped the crank and bearings out also. i had someone tell me that the external oil coler couold be clogged up, would this slow my oil pressure down at at sratup?

so this weekend ill change it back to regular oil do i go with 5 or 10 weight?

Yes, that could do it I would think, also, the screen on the oil pump its self could be partially blocked.

About the weight of oil, the heavier the weight, the better oil pressure you'll have, so I'd go with 10w30 atleast. But you really need to find out why you're pressure is slow to build, becuase if not, then those new bearings won't last long at all.

tbranscom
01-01-2005, 02:21 PM
ok guys thanks for the responces, fri i changed back to 10-30 with a quart of lucas oil stabaliser.... i flushed the oilcoler while i was at it... i wouldnt think the pump screen coulld be cloged becouse its not got 600 miles on it.. but anyhow my psi now is at about 16-18 at fullstop in gear
and ranges from 20-40 while driving depending on the rpms. im still considering takeing that cheapie oil pupm out and trying to go with at highvolume.. what do you think about thte pump and the psi numbers? thanks agian

Fireplug
01-01-2005, 07:31 PM
much much better

Jm93
01-01-2005, 10:46 PM
my 79 runs around 40 at startup.
30-35 at 60mph,
20-30 at idle in gear.

not to terrible for a engine that is 25 years old, with 200k km, and not rebuilt.

clampjockey
01-04-2005, 08:23 PM
i bought an 88 6 mos ago. it had the roughly the same numbers except a little higher during start-up. 1 good, hard run & it's shot. the rebuilt 305 i replaced it with has unbelieveable high pressure on the guage, though it's only got 1000 km's on it yet.

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