btwick

Hi,

383 stroker/roller in my 71 vert. Built motor myself and used high zinc for break in and regular oil for first 1800 mi or so. Just went to 10w-30 synthetic.

After getting the oil hot, the pressure drops down to about 15-17 psi or so at idle, and idle speed goes up 100-150 rpm. Must be due to the oil thinning at hi temp.

Went looking for 10-40w synthetic and the parts stores don't have it. They have 0w-40, 5w-40, 15w-40, 20w-50, 0w-50. etc.

Have read the older posts on this but recommendations vary widely. Leaning towards the 5w-40 for good flow at cold startup and more pressure at high oil temps.

Any thoughts? Live in mild to warm climate and car likes to run at 200*.

Thanks,
Brian

calwldlife

since you built it, you should know bearing clearances.
I would not run 5w anything.
these engines were10w at thinnest.

REELAV8R

I run 0w-40 full synthetic in my hopped up 350 making 440hp 6300 rpm regularly.
the 0w represents the equivalent cold weight. That's when you start the engine.
40w is what it will see in operation.
if it's flat tappet, you're gonna want oil with a good 1000 ppm zinc. Mobil one 0w- 40 does have that. None of you're typical 5w or 10w oils will have the necessary zinc in them.

Buccaneer

IMO, 15-17 at idle is way to low. 25 would be more normal especially on a new motor. What were the main clearances? You might want to go to something like 10w 40 and skip the synthetic oil all together and ensure that you run enough ZZP in the oil for a flat tappet. I am no longer a fan of FT cams no matter what. However, everyone has their own opinion on this subject. GL with your low pressure.

Purple92

I would go with the 15W-40 full Synthetic. You said "roller" - so I assume that means a roller cam - so no real NEED for lots of ZDDP.

The way the measure the hot side rating on oil is basically just how fast it flows (at 212 I believe). However - that is not the way they measure cold side (just saw this on Engine Masters). They use a different methodology entirely to measure the **W side.

The old racing rule of thumb was 10 psi oil pressure for every 1,000 RPM, so you're still comfortably above that.

You certainly COULD run a 15W-50 - but normally that is for engines that are built with larger bearing clearances. Again - if I were you - I'd try the 15W-40 and see how that works for you ...

kossuth

I’ll ask like everyone else, what are your main and rod clearances? Need to know those first. Although I doubt it you could have a weak bypass spring in the oil pump. Also need to know if it’s a flat tappet or roller motor.

btwick

Thanks everyone.

Hydraulic roller motor, and it's been awhile, but believe my bearing clearances were .002. Know for sure they were in spec using Plastigauge.

Also, recall that I determined at lower pressure, the oil pressure gauge which came with the car ran lower than another, newer gauge I checked it with. So, thinking my oil pressure isn't actually that low at idle with hot oil. Will have to confirm that with another test.

What is annoying is the high idle when hot. Has anyone else experienced a 100-150 rpm jump in idle with hot oil? Could it be something entirely different than the oil?

BTW... It is a Melling high volume and high pressure pump. Saw a video where a guy blocked the oil bypass valve with a plug due to the possibly of a high pressure pump opening up the valve and oil going around the filter. I did block the bypass, and of course will be changing my oil filter regularly, so no risk of too much pressure due to a clogged filter.

calwldlife

Cold weight is base stock then modifiers when heated are supposed to act like a thicker stock.
key here is base stock.
I know mr 0w here claims, and, has had no issue.
for us with stock clearances, gm says 10w

Crimson Thunder

I would think a Melling high volume pump with a blocked bypass would have way more than 15-17 of pressure at idle.

Buccaneer

Oops! I missed the part that you have a roller. In that case, no extra ZDDP is needed, the beauty of a roller vs FT. Also, if you are running a HV Melling pump, there is no way that motor should idle that low of a pressure unless something is wrong, likes clearance issues or a pump that is maybe too close to the bottom of the pan or something? My roller lifters are Morel, so I called them and asked them specifically what oil they recommend with their lifters..10W 40 was the answer setting them at one full turn after zero lash. My pressure at cold start is about 75psi and drops to about 60psi at warm idle. Under 25psi at warm idle would make me rather nervous. I would have that motor checked to be safe. GL

btwick

Thanks. Did mention above that I suspect the pressure gauge is wrong, as after I got it in the car, connected the gauge from run stand and it read higher, especially warm, than the gauge in the dash.

Confident I'm higher than 15-17 (had forgotten I tested it when I started this thread) but will confirm that again. Gauge in the dash does read upwards of 60-75 when cold, so confusing how a gauge would read OK when cold, but when hot, reads low.

Would like to find 10W-40 synth to change out the 10W-30, but can't find it. Thinking with the comments here that I'll go with the 15W-40 synth and see if that keeps pressure up and reduces the idle creep when hot.

Crimson Thunder

Don't rely on the oil pressure gauge on your dash. Buy a cheap gauge and temporarily stick it out the back of your hood and go for a drive.

Stormin_Normin

Bluprint recommends no synthetic for the first 6k miles. My builder recommended just using dyno oil since it's a summer cruiser. I'm running the old 10-40 dyno oil, 75 psi cold and 40 psi hot.

Chagjr

cottoneg

Exactly.My machinist told me to run 20W-50. I do NOT drive the car in cold winter weather. That may help bring up the oil pressure.

I used to run VR-1 Racing oil due to the high zinc. But my understanding is that it is a racing oil that may not contain all the normal additives like detergents and corrosion / rust inhibitors.

I switched to https://drivenracingoil.com/i-304978...t-rod-oil.html

A more modern formula. I do not change to another oil for track events. Driven has technical help. Call/email them, give them the specs on your motor and intended use and ask them for a recommendation.

Jebbysan

If you only have 15-17psi at idle warm with a high pressure, high volume pump only three things can be going on:
1) The bearing clearances are wider than what you say
2) The gauge is way off
3) The pump has some kind of defect

The oil filter bypass has zero to do with oil pressure at the gauge.....
The oiling system is a controlled leak....it leaks from the main and rod bearings and also from the pushrods up top.....some builders use a oil plug in the from by the timing chain that has a hole in it.....that's it. It can come from no where else......sooooo.....the lifters aren't causing it (you would hear one).....so either the pumps internal bypass is blown or stuck open or the bearing clearances are all at like .003 to .004.....
I built five small blocks last year.....all has the standard M55 pump in them.....all had .0025 on the rods and .0025-.003 on the mains......all of the engines had 45-50 at idle cold and 30-35psi hot at idle.......all run 15w40 flavor of the week diesel oil with a bottle of Lucas ZDDP.
I cannot stress hard enough how much a small block and a big block doesn't need a high pressure or high volume pump and there are still many who will argue with me on this.......the Chevy cousins have the best designed oiling system in all of Vintagedom......
My money is on the pump.....
At 6000rpm...a small block uses 7 more horsepower to turn the driveshaft on an HV pump as compared to a STD......the HV should never be run in anything but a dedicated track engine a this is a fact......7hp is 2 more than your lawn mower makes turning the oil pump driveshaft........and that translates to wear on the cam gear and timing chain.......
The oil passages in a small block are too small to handle the extra volume of oil.....and this translates to pressure.....to use an HV properly the block main oil feed to the cam and both lifter galleys have to be drilled larger.......it was SOP in the old days.......
Change the gauge and and document oil pressure....if it is still low......pull pan and inspect pump and or bearing clearances.......
One of the most important measurements on an engine is the bearing clearance......plasticgauge is better than nothing but not preferred.......
There are some who run HV's with no problem and swear by them....but if you build a thousand small blocks with .0025 on the rods and .003 on the mains with a M55 pump....they will all have at least 30psi hot at idle....(given no part failure)....and this is not debatable.


Jebby

btwick

Thanks for the tips everyone. All good info.

First step will be to recheck pressure with second gauge. Will do that this weekend and report back what actual hot idle pressure is.

But, has anyone experienced idle speed increases due to hot and thinning oil? Maybe there is something else moving idle speed up when oil is hot?

Jebbysan

Your idle is not increasing 150 RPM due to oil thinning.....you have something else going on there....

Jebby

sunflower 1972

ContactUs@bp.com <contactus@bp.com>
To:nwh28@sbcglobal.net
Mon, Mar 6 at 5:39 PM
Hello Neil,

Thank you for contacting Castrol North America.

The formula for Castrol EDGE 5W-50 has not changed in many years. Castrol EDGE 5W-50 US contains a typical Zinc level of 1396 ppm and a typical Phosphorus level of 1228 ppm.

As per different marketing directives, the packaging and labels can change from time to time to highlight different aspects of the oil.

The following Castrol oils are blended with a high zinc and phosphorus content to help prevent premature aging, wear, and metal fatigue on engines with high-tension valve springs or performance modifications that create high contact pressure and extreme internal temperatures (i.e., push-rod, flat tappet engines, and performance cam applications):

• Castrol GTX Classic 20W-50 (Conventional Oil Formula)
Features/Benefits:
High Zinc (1400 ppm max)
Specially formulated to provide unsurpassed wear protection for classic/collector cars
& racing applications
Compatible with gasoline and alcohol-based fuels


• Castrol EDGE 5W-50 (Full Synthetic Oil Formula)
Features/Benefits
High Zinc – Typical Level is close to 1400 ppm
Excellent cold temperature properties
High-temperature viscosity (SAE 50) that is suitable for use in many classic car applications

Thank you again for contacting Castrol. We value your patronage!

Castrol Consumer Relations
1-800-462-0835
Hour of Operation: Monday-Friday 9 am-7 pm EST

OMF

The RPM increase could be caused by weak advance springs, or a rusted & sticking mechanical advance system in the distributor pull the top off the distributor and remove the rotor to check. Do you by chance have a dashpot that is holding the throttle open a touch? and how about your throttle return spring....is it working as it should? How about vacuum leaks....they are famous on our 'vettes .....unplug the entire vacuum system (except the brakes) and take it for a spin to check.