dzltek

I'm about to start ordering parts for my rebuild, I found rods 3&4 spun, but barely scratched the crank. I'm wondering about the oil pump. I know lt1's are notorious for low oil pressure, so should I buy a high pressure pump or buy a stock one and mod it? Or will a stock one be fine? It is a street strip car that will see plenty of both. I'll catch a little crap from some of you guys, but oh well. I've got a cc306 cam for $100, in like new condition, what springs do I need for the cam?

Injuneer

The "notorious" low oil pressure is usually the result of excessive bearing clearances, not a faulty oil pump.

The "high pressure" pump is typically the stock pump with an 80psi spring. A blueprinted stocker is more than adequate. The high pressure is not needed unless you are going to push the rev limit way up.

dzltek

What do you consider pushing rpms way up? It's a stock shortblock, gonna add a little compression, cc306 cam, and a little port work.

96capricemgr

With the 306 and mediocre port work you are likely still looking at 6800 that cam will do well to 7000 with some heads.

Let the car sit till you get a better understanding of things.

dzltek

I'm not gonna let it sit because you tell me too. And you haven't got a clue at what kind of port work I'm gonna get. Just a little background on the guy, he took the brodix track 1's off my father in laws car, ported, valve job and shaved a little off. That's all that was done to the car, it picked up 8.5 tenths. So I doubt its mediocre. You don't have to spend big money to run good. I understand AI and le do good head work, but its not a must. Ive read a lot of your post and if it involves a cc306 cam or port work by somebody else, you talk down on people and trash them or try to make them out to be an idiot. I have a vast knowledge of what I'm doin and didn't ask about what you thought of my cam choice, I asked what springs were needed just in case somebody knew but ill just look it up or call comp, and if the stock oil pump is sufficient enough for street strip. I don't care if you don't like my cam choice, I'm the one building and driving it.

shoebox

A Melling 10554 pump with their pink spring (70#) (or GM white spring-same thing) is what I would recommend. It is a standard volume pump.

96capricemgr

I never said you were getting mediocre port work. I said that with mediocre port work the 306 likes a lot of rpm and with better heads likes even more rpm. The rpm plays into the springs needed, stock heads will choke the cam to a lower rpm than a good set of heads.

You have fabricated some idea about bad oiling on the LT1..

dzltek

Thanks shoebox, that's what I was looking for.

How have I fabricated an idea that these engines have bad oiling? Do a search and there's thousands of people asking about the low oil pressure issues. 6psi is low pressure at idle. And honestly I don't want my pressure under 15 psi at hot idle. But I guess 180,000 hard miles will make the clearances loose and oil pressure low.

Injuneer

You seem to think the pump causes the low pressure and needs to be upgraded - at least that's the question you asked. The low pressure is caused by engine wear. That's not a problem with the oil pump or the oiling system. It's a problem with the way the engine is set up, run and maintained. Many of us have never had a problem with low oil pressure.

96capricemgr

The smallblock chevy does NOT need a lot of oil pressure.
Changes from normal oil pressure mean VASTLY more than what the cheap inaccurate dash gauge reads.

That and many oils are very thin these days due to CAFE. 5w-30 the fill cap recommends is also a RANGE some popular brands of oil consistently tending towards the thin end of ranges which will show lower pressure while other brands tend towards the thick end.

Then you get the guys who are nervous about "thin" 5w-30 and dump in 10w-30 because they mistakenly believe it is thicker and some 10w-30s are VERY low in the 30weight range.

Basically what I am saying is the biggest "problem" the LT1 has with oiling or anything else for that matter is a lack of QUALITY information.
The 6psi you want to state as proof of an issue is GM's minimum number for pressure at 1000rpm so idle could go a little lower yet.

People just like to apply OLD OUTDATED ideas and want at least 10psi per 1000rpm and that ideas time has long since passed.

96capricemgr

To expand on what Fred said a little, the pump puts out a certain volume of oil per rotation, the "pressure" is made by the restriction of trying to push it past the bearings and such and the pressure is NOT what keeps things apart. The crank and such basically hyroplane on the oil. The pressure is just easier to measure than flow would be and flow is what keeps things apart. That is NOT to say high volume is good, high volume just maxes out the relief spring at a lower rpm cavitates more easily, takes more power to turn, eats the oilpump drive, and heats up the oil.

I have put high pressure springs in a few LT1 oilpumps but did it more to replace and old stock relief spring than to increase pressure. Did not verify with mechanical but I suspect that a 15yo original oil pressure relief spring probably isn't holding 60psi anymore and a new spring is like $2. The high pressure spring just opens the bypass a little later allowing more of the oil being moved anyway to go across the bearings rather than recirculate in the pump.

MachinistOne

As usual, I will agree with both of these guys, the 10554 is a good choice. For a stockish type rebuild I would use a standard M55 or M55A with the proper 5/8" pickup over the M155(A) due to the thin casting Melling is using on those pumps.

For a bone stock motor sure, you don't need the 10psi per 1000rpm...but for performance motors with elevated cylinder pressures I want to stick to the rule due to higher bearing loads. Seen plenty of bearings that have obviously touched the crank on engines where the driver said pressure was below 10/1000...not going to risk grabbing a bearing because I want to reduce .2hp worth of parasitic loss with a low pressure pump.

dzltek

With this being my first fuel injected muscle car, and also being out of the scene for a while, I wasn't sure if the stock pump was at fault or what. So I was just wanting to get a grasp on that. Also, the engine had been making a little noise at first start up, so i changed the oil and filter, and used 15w40, diesel oil, and it quietened the noise a little. So my rod clearances have probably been a little loose for a while now.

Do any of Yall know where to find bearing clearances or are the they same as say a gen1 sbc?

Injuneer

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shoebox

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