oil pressure high/LT-1

[robert leazenby]

I just got done checking the archives but I guess I still don't have a warm fuzzy on what to do with my specific application.

I have a newly rebuilt motor (1970 LT-1 specifications). I installed the oil pump with the high pressure spring. (Already installed in the pump) It also came with a lower pressure spring.

When cold I have extremly high pressure, pegged or slightly above the 70 psi mark. After warm the pressure drops only slightly and runs about 65 to 70 at about 3500 to 4000 rpms and goes up a little as the rpms go up. As near as I can tell anyway due to the highest number being 70 psi.

My mormal driving is at highway speeds, about 3000 to 4000 rpms depending on Interstate or two lane.

I am dropping the pan tomorrow to replace pan gasket (slight leak at the bottom of timing cover, can't stand leaks) While the pan is off should I install the lower pressure spring (melling pump) or is the high pressure better for solid lifters. Again I am not racing and will only see 6000 to 6500 rpm occasionally.

[Gerry Proctor]

Re: oil pressure high/LT-1

Seventy p.s.i. is not that high, Robert. As to whether you need the pressure or not depends on the machining specs your crank was finished to and the redline you desire to run. If the engine was indeed machined to LT-1 specs, then you'll do no harm running that pressure. There are pervasive myths about high-pressure/high-volume pumps being bad (sucking your pan dry, wearing out distributor gears) but pump manufacturers like Melling have info on their sites that provide the technical info for you to judge this for yourself.

[Gerry Proctor]

Re: oil pressure high/LT-1

Seventy p.s.i. is not that high, Robert. As to whether you need the pressure or not depends on the machining specs your crank was finished to and the redline you desire to run. If the engine was indeed machined to LT-1 specs, then you'll do no harm running that pressure. There are pervasive myths about high-pressure/high-volume pumps being bad (sucking your pan dry, wearing out distributor gears) but pump manufacturers like Melling have info on their sites that provide the technical info for you to judge this for yourself.

[robert leazenby]

Re: oil pressure high/LT-1

The engine was built as close to factory specs as possible. The steel crank was turned 20/20 but clearances were compensated for with bearings. The car has a 6 qt pan so really am not worried about running that dry. Just don't want to blow rear mains.

If I wasn't pulling the pan I would not change the spring, just wondering while it is off.

I will check Melling's site.

[robert leazenby]

Re: oil pressure high/LT-1

The engine was built as close to factory specs as possible. The steel crank was turned 20/20 but clearances were compensated for with bearings. The car has a 6 qt pan so really am not worried about running that dry. Just don't want to blow rear mains.

If I wasn't pulling the pan I would not change the spring, just wondering while it is off.

I will check Melling's site.

[Michael W.]

This begs the question-

what is the advantage of having a high pressure or high volume pump in a street driven engine?

The high(er) pressure is not the way the car came off the line from GM when it was new, and is a dead give away during judging, so why would the car need it now?

We've all seen lots of boy racer go fast snake oil stuff in the catalogs.

[Michael W.]

This begs the question-

what is the advantage of having a high pressure or high volume pump in a street driven engine?

The high(er) pressure is not the way the car came off the line from GM when it was new, and is a dead give away during judging, so why would the car need it now?

We've all seen lots of boy racer go fast snake oil stuff in the catalogs.

[Gerry Proctor]

Re: This begs the question-

Need it? That's an entirely different question an proposed by Robert...HAS it. Rather than write from what I know from experience, go here and read up on the subject of HP/HV pumps http://www.melling.com/techbul1.html For the use as proposed by Robert, I would say he doesn't NEED the pump, but it won't cause any harm and is not worth digging into it. Remember the days before you could buy HV/HP pumps at the grocery store? It was common to get a Z/28 pump or a big block pump to put on your warmed-up small block.

[Gerry Proctor]

Re: This begs the question-

Need it? That's an entirely different question an proposed by Robert...HAS it. Rather than write from what I know from experience, go here and read up on the subject of HP/HV pumps http://www.melling.com/techbul1.html For the use as proposed by Robert, I would say he doesn't NEED the pump, but it won't cause any harm and is not worth digging into it. Remember the days before you could buy HV/HP pumps at the grocery store? It was common to get a Z/28 pump or a big block pump to put on your warmed-up small block.

[Joe L.]

Re: This begs the question-

Mike-----

Most 63+ Corvette small blocks with solid lifters were originally equipped with a high pressure (but NOT high volume) oil pump. They were the only small blocks used in Corvettes which were ever so-equipped. This pump was identical to the standard pump except for the pressure relief spring. Engines included in this were solid lifer, SHP 63-65 and 70-72 LT-1. The only exception was early 63 with 340 and 360 hp engines which received the standard pump.

However, I don't know if the Melling pump with the high pressure spring produces the same oil pressure as the GM pump with high pressure spring. I would expect that it would, but I don't know that. The current part number for the GM high pressure pump is GM #12555884. The GM high pressure spring is available under GM #3848911, but I don't know if it's compatible with or will produce the same pressure if used with a Melling pump.

[Joe L.]

Re: This begs the question-

Mike-----

Most 63+ Corvette small blocks with solid lifters were originally equipped with a high pressure (but NOT high volume) oil pump. They were the only small blocks used in Corvettes which were ever so-equipped. This pump was identical to the standard pump except for the pressure relief spring. Engines included in this were solid lifer, SHP 63-65 and 70-72 LT-1. The only exception was early 63 with 340 and 360 hp engines which received the standard pump.

However, I don't know if the Melling pump with the high pressure spring produces the same oil pressure as the GM pump with high pressure spring. I would expect that it would, but I don't know that. The current part number for the GM high pressure pump is GM #12555884. The GM high pressure spring is available under GM #3848911, but I don't know if it's compatible with or will produce the same pressure if used with a Melling pump.

[Dan White]

Re: This begs the question-

I recently installed the same pump you have in my 66 (with a 68 327), and used the lower pressure spring. I still get 40 to 50 lbs. at idle.

[Dan White]

Re: This begs the question-

I recently installed the same pump you have in my 66 (with a 68 327), and used the lower pressure spring. I still get 40 to 50 lbs. at idle.