Do I need oil restrictors in my engine? - Team Camaro Tech
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post #1 of 12 (permalink) Old Sep 3rd, 02, 11:05 AM Thread Starter
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I am currently in the process reassembling my 400 small block. This time around, I am using the Comp Cams 282S solid cam. The oil pump is stock with a high pressure spring in it. The car mostly sees street use, but it does occasionally get autocrossed and drag raced. Do I need oil restrictors in this engine? I am using Comp Cams solid lifters. Do they restrict oil to the top end of the motor when compared to a hydraulic lifter?
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post #2 of 12 (permalink) Old Sep 3rd, 02, 01:36 PM
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Oil restrictors are made for "race only" applications with soild ROLLER cams. I spoke with several cam companies about this and was told absolutely not to use them on a street car (was building a solid roller street engine). The reason being the oil you are restricting is what cools your valve springs (they restrict oil to the top end). On the street you need that oil on the valve springs. On a drag only car you "can get away with it 1/4 mile at a time (they also run at high RPM's which will still put more oil to the top end). Most companies didn't even recommend them for all out race engines. Your flat tappet cam needs the oil as do your vavle springs. Your cam (flat or hydralic) and valve springs will die an early death if you run oil restrictors. I'm sure others will have more to add or maybe even a different opinion.


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post #3 of 12 (permalink) Old Sep 3rd, 02, 02:35 PM
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Don't even think about using oil restrictors in a street car. I rather doubt with your cam that the valve springs will die with restrictors in, but everything else in the valve train will. I used them in drag race only engines but that was the only place.

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post #4 of 12 (permalink) Old Sep 3rd, 02, 04:38 PM Thread Starter
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My machinist and Comp Cams both said to run a restictor, although Comp was kind of in between on the subject. That is why I ask. I have always read that you didn't need them on a street engine then Comp and my machinist both recommend them.

I bought a set of .060" restrictors today. I am undecided as to if I am going to install them or not so keep the opinions, facts, real world experience, or anything else coming. I really want to hear what you all have to say.
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post #5 of 12 (permalink) Old Sep 3rd, 02, 05:50 PM
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Put my vote in for NOT using the restrictors.
My opinion was based on the exact facts that the others have previously mentioned.
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post #6 of 12 (permalink) Old Sep 3rd, 02, 06:39 PM
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I would just ask the question "am I trying to fix a problem with this?"
If not, then I would'nt do it just because.
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post #7 of 12 (permalink) Old Sep 3rd, 02, 07:07 PM Thread Starter
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The general consensus seems to be that I should not run the restrictors. Anybody else got a reason to run them or to not run them?

Has anybody here ever run them on a street engine and had problems? Has anybody run them on the street with no problems?
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post #8 of 12 (permalink) Old Sep 3rd, 02, 10:02 PM
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If you use the standard lifters, watch your oil pressure when autocrossing or consider a better oil pan with small kickouts.
A lot depends on your engine rpm's, length of straights, and rocker arm type.

I had oil pressure fluctuations on my 67 with stock rockers and mech lifters when autocrossing. I switched to the orifice type lifters that are supposed to reduce oil flow by 20% and had no more oil pressure problems when autocrossing.
Didn't have any valve spring problems when street driving either, but the orifice lifters supply less oil the more lift you have because the oil hole is exposed less time.
The Z/28 valve covers with cast in drippers are mandatory with the orifice lifters.
I see many vintage race vettes using a metal strap over the oil hole in the rocker to deflect oil to the rocker ball. They have to use stock type rockers, the grooved rocker balls are Legal.
You have the option of drilling the restrictors to get just what you want. I have no idea what size might work best though.

If you use roller rockers and the car will corner hard, the restrictors would make the most sense.

If you use stock rockers, have less than max cornering power, no restrictors might be best.

I know for sure the anti-pumpup type lifters are bad news, they pass too much oil to the top end and can starve the bottom end when cornering hard. If you have skinny tires, it's not so bad.

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post #9 of 12 (permalink) Old Sep 4th, 02, 05:29 AM Thread Starter
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David, that is kind of what I was thinking. I would like to restrict oil to the top end, but just a little bit. I went with the Milodon Claimer oil pan and I am pretty pleased with it. It is much better than the stock oil pan. I also have roller rockers. The car doesn't corner hard right now, but a set of slicks at all four corners along with the Hotchkis suspension that I already have will probably change that.

Now, I wonder what size the restrictor hole needs to be to restrict oil about 20%. .060" seems a little small to me. Would it be safe to say that the hole needs to be approximately 80% of the original oil galley?
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post #10 of 12 (permalink) Old Sep 4th, 02, 02:34 PM
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There seems to be a lot of strong opinions on this subject - standard oil pump vs high volume, restrictor or no restrictor. But I think there is a lot of middle ground that could be explored.

Melling now has high volume oil pumps that increase flow by only 10%. Their old HV-55 pumps increased by 30%. Maybe 10% is just what us street strip folks need . . .

Oil restrictors are another one. .030" restrictors would be suicide for a hydraulic cammed street engine with stamped steel rockers, but what about a roller rocker engine with with a solid cam and oil drippers? Maybe a .050 or .060" restrictor would be good in this situation. You could even drill them out to .100 if you want to provide just a little restriction - all the SBC galleys are like 3/16" DIA anyway.

I talked at length with my machinist friend yesterday about this. It all boils down to what is needed to maintain that 10 psi oil pressure for every 1000 RPM. If you run loose bearing clearances and light 10w30 oil you may NEED an HV pump to maintain pressure, you might also NEED a deep sump pan to keep the pump from sucking air at the top end.

Oil viscosity plays a key role in all this too. 20w50 oil being thicker resists flow more and consequently builds more pressure. You could conceivably create more pressure with a standard volume pump (high pressure spring) and thick oil than with an HV pump running thin oil.

I also bet that if you run oil restrictors oil pressure will increase. 20w50 oil, an HV pump combined with restrictors would probably have a tight engine idling with 70 psi of pressure hot - on the other extreme a standard oil pump in a loose engine with 5w30 oil will have trouble making 10 psi per 1000 RPM.

Just my opinion.

Sorry so long.
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post #11 of 12 (permalink) Old Sep 4th, 02, 06:44 PM Thread Starter
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I spoke with Comp Cams again today, this time with a different person. He recommended that I not run restrictors in the engine. He seemed to think that it would shorten cam life.

I also spoke with my machinist at length about the subject today. He is still all for running restrictors. He also mentioned that he puts them in all of the solid lift motors that he builds without any problem so far, except for motors that originally came with solid lift cams like old Corvette motors.

Running restrictors even makes sense to me. If a solid lift cam and roller rockers don't need as much oil as a hydraulic cam and stamped rockers, why would you not restrict the oil going to the top end of the motor? I am also looking at it like this: If I had to choose what end of the motor that I wanted to repair, it would be the top end. Everything can be done while the motor is in the car in a relatively short time. Even a cam can be changed in a day. A broken valve spring would probably mean that I would have to remove a cylinder head, but that is still better than rebuilding the bottom end of the motor. If you can't tell, I really don't want to have to rebuild the bottom end of this motor again for a long time.

As it stands right now, I think that I will run the restrictors with the holes drilled to .060" to .100". I don't want to restict oil to the top end much, but I do want to restrict it a little bit. I am planning on installing the motor tomorrow. I'll let you all know what I ends up happening between now and then.

In the mean time. If anyone here has run restrictors and had valvetrain problems, please post on this thread. I would really like to hear what happened. Also, if anyone has run the restrictors and not had problems, I would really like to hear about that as well.
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post #12 of 12 (permalink) Old Sep 5th, 02, 06:01 AM
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Iíve run restrictors on my solid lifter BBC (Crower with roller rockers) for 2 years on the street. However I did drill them out to .1000 from the original .062. Blueprinted small pump set at 55 lbs. Small pan (6 Quart) with windage trays top and bottom. It appears to be a fairly good setup without any cornering hassles or ľ mile problems. Good luck
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