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Username Post: 235 Oil Pressure        (Topic#250874)
Dean50 
"8th Year" Gold Supporting Member
Posts: 872
Dean50
Loc: Michigan
Reg: 01-02-07
10-13-10 04:37 PM - Post#1989089    

Getting close to 2000 miles on a rebuilt 235PG engine. The needle stays pinned on my 30 LB gauge until the oil gets hot, then runs around 25 pounds at 50-55 MPH. Just wondering what normal is for this engine. I run 10W30 oil.
Thanks
Dean50


 
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52HardTop 
My Birthday Week
Posts: 1626
52HardTop
Age: 60
Loc: North Haven, Connecticut
Reg: 05-09-04
10-13-10 05:32 PM - Post#1989123    
    In response to Dean50

I for one can comment and say my also rebuilt 54 235 with just over 2000 miles does the same. I'm using a straight 30 and it too runs mostly at 30lbs and never dropping below 25lbs. I originally used Rotella straight 30. This year I used Amsoil straight 30 synthetic. With both oils the pressure was the same.
Dom
2011 Camaro SS 426 HP, Red Jewel Tint. Killer!

52 Bel Air a traditional 50s Ride.

51 Convertible a 60s Ride.

51 1/2 Ton pickup soon to be a little of both..



 
Dean50 
"8th Year" Gold Supporting Member
Posts: 872
Dean50
Loc: Michigan
Reg: 01-02-07
10-13-10 07:33 PM - Post#1989178    
    In response to 52HardTop

Thanks Dom
The car seems to me to run real good, pulls pretty strong compared to the old 216, but this is my first Chevy this old so I don't have any reference to compare to. Took a 180 mile ride over the weekend with four folks in the car and it ran real nice.
Dean50


 
b. dudley 
Contributor
Posts: 109

Loc: Rochester, NY
Reg: 09-28-10
10-14-10 06:09 AM - Post#1989311    
    In response to Dean50

My original 59,000 mile '53 runs at 55-60psi when driving and only drops to 30 when at idle.

Oil weight can effect oil pressure to an extent, but nothing major. I have found that with heavier weights there is not as much change in pressure related to RPM.

The general rule of thumb that I have always heard is that you should have at least 10psi for every 1,000 rpm. So if you are consistently running at 30psi when driving, you should be ok.
B. Dudley


 
Dean50 
"8th Year" Gold Supporting Member
Posts: 872
Dean50
Loc: Michigan
Reg: 01-02-07
10-14-10 04:10 PM - Post#1989509    
    In response to b. dudley

Thanks
It took me a couple of years to learn about the 216, now I've got another personality to get used to.
Dean50


 
Gene_Schneider 
Ultra Senior Member
Posts: 10958

Loc: Wisconsin..USA
Reg: 09-27-02
10-14-10 07:00 PM - Post#1989609    
    In response to Dean50

The very early 1953 PG engines had the pump pressure regulated for 35 pounds hot at 50 MPH.
Then it was upped to 45 pounds for the most of 1953 and all of 1954.

The 1955 and up pump was different and was back down to 35 pounds.

If you have a replacement pump the pressure regulator may be "set" for the lower pressure _ or - the rod and main bearings may have tooo much clearence.

Thats why I prefer to stay with the original pump if possible or find and use only a NOS GM pump.

I would suggest trying a master oil gauge as 25 pounds is awful low.
ChevGene 1934 Master sedan 1939 Master DeLuxe Town Sedan 1950 Styline DeLuxe Power Glide 1957 Nomad 283 PG 1963 Corvair Convertible


 
Dean50 
"8th Year" Gold Supporting Member
Posts: 872
Dean50
Loc: Michigan
Reg: 01-02-07
10-14-10 07:36 PM - Post#1989629    
    In response to Gene_Schneider

Thanks Gene
Now you've got me going. I'll follow this up. By master gauge do you mean an independent separate gauge like a service station?
Is a new oil pump the cure?
Thanks again
Dean50


 
Gene_Schneider 
Ultra Senior Member
Posts: 10958

Loc: Wisconsin..USA
Reg: 09-27-02
10-15-10 02:47 PM - Post#1989960    
    In response to Dean50

You can buy an oil pressure gauage had hose from a parts store. It made just for checking oil pressure.
I assume a new oil was installed when the engine was rebuilt. Too bad you couldn't get the original pump back.
Check it out with a different gauge first then see what happens.
ChevGene 1934 Master sedan 1939 Master DeLuxe Town Sedan 1950 Styline DeLuxe Power Glide 1957 Nomad 283 PG 1963 Corvair Convertible


 
Dean50 
"8th Year" Gold Supporting Member
Posts: 872
Dean50
Loc: Michigan
Reg: 01-02-07
10-15-10 04:00 PM - Post#1989992    
    In response to Gene_Schneider

Thanks Gene
I'll talk to the rebuilder and check that pressure with another gauge.
Dean50


 
6-bangertim 
Frequent Contributor
Posts: 2100

Age: 56
Loc: El Cajon, Calif.
Reg: 11-30-08
10-20-10 06:29 PM - Post#1992559    
    In response to Gene_Schneider

Gene, how does one increase the oil pressure in a '55 and later engine?

My 3/4 built 235 ('55 block) spun a rod bearing 2 weeks ago on the freeway in my '57. Wasn't even running it hard when the temp went to 230 and oil dropped from 30 to 12 lbs., then 0 at idle. Engine never had great pressure at idle - 12 lbs. when warm, dropping to 4-6 lbs. after a good freeway run. Oil is 20w-50 NAPA and 1 bottle of STP (for the ZDDP). Stock oil filter was used.

I did a complete tear-down 2 years ago for moly rings and rod bearings. Checked rod and main clearances with plasti-gauge - all checked between .002 and .0025". Rods were also checked by my hi-perf. machine shop and did not require resizing.

Last year I replaced the oil pump with another near-new pump in a attempt to increase the hot -idle pressure, but it didn't help much if any.

Over the years, I've assembled 2 SBC's and 3 or 4 235's. This is my first BOTTOM END FAILURE. I'm sure there has to be a lesson in this, but just don't know what I could have missed. Rods #2 and 4 took the worst beating, with broken inserts. #3 still had the lead-tin, but the others were wiped into the copper.

Gene, could you - or anyone here - shed some light on this? I still have a 261 to build up and another 235 to freshen up. Your knowlege and memory for details is NOTHING SHORT OF AMAZING - so many of us here on CT really appreciate your responses!!!

Many MUCHO Thanks, Tim
Too Poor to Restore...My Nifty 150!
Proud owner of MISS NOVEMBER - 2011 Tri-Five Calender


 
Gene_Schneider 
Ultra Senior Member
Posts: 10958

Loc: Wisconsin..USA
Reg: 09-27-02
10-20-10 07:21 PM - Post#1992592    
    In response to 6-bangertim

First you are runnig too "thick" of an oil. Then adding the STP makes it thicker.
I would run nothing heaiver than a 10W-40 or 15W-40. Adding the STP tp #50 brings it up to #60. Its better to have thin oil passing thru the bearings faster because it is the oil that cools the bearings.
There is enough ZDDP in todays oils for a 6 cylinder with a broken-in camshaft.
Two areas can cause low oil prssure. Either the oil pump its self or too much bearing clearence, especially the main bearings.
Was anything done to modify the oiling system?
If its a 1955 engine does it still have the floating oil pump screen?
ChevGene 1934 Master sedan 1939 Master DeLuxe Town Sedan 1950 Styline DeLuxe Power Glide 1957 Nomad 283 PG 1963 Corvair Convertible


 
6-bangertim 
Frequent Contributor
Posts: 2100

Age: 56
Loc: El Cajon, Calif.
Reg: 11-30-08
10-20-10 10:41 PM - Post#1992677    
    In response to Gene_Schneider

Thanks Gene for responding tonight!

I changed from Rotella 15w-40 - after driving home 40+ miles on the freeway from a club event on 12 lbs. pressure.

Oil pump still has the floating screen. I did slip a tiny washer - maybe .020 to .030" thick between the relief spring and roll pin. Didn't seem to help boost pressure any.

I don't know of any modifications - everything looked STOCK.

Mains had shims, checked at .002-.0025" with Plasti-gauge.

The engine's PO had it rebuilt in 1978, with fully ported head, TRW 9:1 pistons, Crower cam and kit (I got the invoices and cam card). Builder is long gone, but they did leave out the tin baffle under the road draft tube. Six months after the install, broke a valve spring and dropped a intake valve. BITCHIN' ported head was found cracked. Before I pulled the head, checked compression - #6 hole was 20 psi down from the others, thus the tear-down. Never ran without at least one oil leak - despite my care to prevent them. Crank even had battle scars from a previous SEVERE blow-up.

I'm not gonna spend another nickle on this POS.
I SWEAR IT IS JINXED!!! GOTTA LOOK FORWARD - just don't want to screw up the next one!

- Tim

Too Poor to Restore...My Nifty 150!
Proud owner of MISS NOVEMBER - 2011 Tri-Five Calender


 
kitabel 
Contributor
Posts: 291

Reg: 11-28-09
10-21-10 05:40 AM - Post#1992732    
    In response to 6-bangertim

change in pressure related to RPM

That's controlled by the relief valve, heavier oil only makes it reach the same maximum pressure sooner.

More oil pressure?
1. bigger pump (does not exist in 1955-63)
2. faster pump (not possible)
3. tighter bearing clearance
4. higher viscosity
5. tighter pump gear end-play (should not exceed .0025")
6. remove hydraulic lifters

In general, pumps don't wear out (except for end-play, which may be bad in a new pump). There are no seals, it's just metal to metal. The gears are steel, the body is cast-iron.

 
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