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Old 10-19-2004, 05:22 AM
Big Block Z28
 
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BB Oil Pressure

I recently started up the newly built BB engine in my 70 Camaro. All parts are new including the oil pump. When the engine is cold and RPMs held at 2000 the oil pressure is 65-70 pounds and at idle it is around 20-25. As the engine comes up to temperature you can see the oil pressure decrease. At operating temperature the oil pressure at 2000 RPMs is down to 30 pounds and at idle it is at 10-15 pounds. The oil pump is a new Summit pump and has not been shimmed. Does anyone know if this is normal, or should the pump be removed and either shimmed or replaced?

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Old 10-19-2004, 05:36 AM
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It should be a little higher at operating temp. The idle pressures seem OK. Are you sure that all gallery plugs where reinstalled?

Chevy motors big and small are not known for high oil pressure.
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Old 10-19-2004, 05:57 AM
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at operating temp Id like to see atleast 30 lbs. on a fresh motor...no need for any more...10-15 I dont like...Summit oil pump ? ack why ? hard to say where the problem is for sure...but a summit brand pump scares me. who makes it I wonder
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Old 10-19-2004, 07:02 AM
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pressure

What viscosity oil are you running in it??? What are the idle rpm's.

10/15 lbs is a tick on the low side. Does the gauge respond instantly when you apply the gas???

Do you have any idea of what the bearing clearances are inside this engine????

Keith
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Old 10-19-2004, 07:19 AM
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I didn't build the engine myself, so I'll have to check on the oil gallery plugs.

I understand the Summit pump is mad by Melling, so it's a pretty good brand.

The oil is 20W50 and idle is 700 RPM. The gage seems to respond normally when the throttle is pressed. I don't know what the clearances are. I can check. I do know that the engine wasn't built "tight."
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Old 10-19-2004, 07:42 AM
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I've seen several BB do that, and they lived. My self I would rather have more.

Did the pump come with two springs? I would change to the bigger spring.

If there was a gally plug out, there wouldn't be any pressure, would there?

Troy
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Old 10-19-2004, 07:48 AM
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I don't know if the pump came with one or two springs. When I bought it I just handed it over to my nephew who built the engine. (He's pretty good at engines; he's on the pit crew for one of the top Pro Mod cars in the country.) He thinks we should pull the pump and shim it. It sounds like that may be the equivalent of a longer spring.
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Old 10-19-2004, 07:58 AM
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Should have been an extra spring in the box. I have shimmed the org. spring, but I like the accurate spring better.

Troy
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Old 10-19-2004, 08:01 AM
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PRESSURE

I agree with troy that if a plug was out the pressure would be low at the start up also, not just after warm up. You could change the spring but it probably will not help the idle pressure at all. you may get a tick more total pressure or you may not. The spring controles the bypass witch kicks out at a certin pressure. If the engine is not able to obtain that pressure it will never kick the by pass open no matter how heavy of a spring you install. I have cahnged the end play on oil pumps and never gained more then a few psi total. So unless the pump has something drastic wrong changing to a new one will probably not gain and results.

Some thing for your consideration. If you are running a fram filter and the by pass is plugged in the filter adapter this could be a problem for you. Also did you change the filter after the engine was first started???

If the engine was built with the bearing clearance on the top of the tolerances you will just have to live with the lower oil pressure. I owned a 69 buick grand sport. It would put the guage on zero when you stopped and the max pressure the engine ever reached was 30 lbs. It ran like that for 2 years before i bought the car and i ran it like that for a year. If the guage moves when you apply the throttle and the engine reaches 50 or so lbs max pressure i think it will be fine...

keith
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Old 10-19-2004, 08:09 AM
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I have a new GM filter adapter and used a Fram filter for startup. I've changed the oil and now have a K&N filter.
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Old 10-19-2004, 08:33 AM
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filter

You get an A plus for filter choice..

Do you know if that new filter adapter had the by pass blocked???

Keith
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Old 10-19-2004, 08:45 AM
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The new filter adapter was just as I bought it from the GM dealer with no modifications.
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Old 10-19-2004, 12:27 PM
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since your cuz works on a pro Mod car, is it possible he clearanced it like a race engine ?
Drag racers often times dont want much oil pressure, it takes horse power to make oil pressure, so sometimes there intenionally built for low oil pressure
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Old 10-19-2004, 01:24 PM
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That's an interesting comment, however, he knows that the engine is for a street driven car. I'll ask him anyway.
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Old 10-19-2004, 02:01 PM
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My last BBC was the same way. It lasted for 5 years like that. Towards the end before I sold the car, switched from 30wt to 10-40, it brought it up somewhat, but not much.
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