I lost a fresh motor a few months back and would like to warn others about the way the motor expired. The bypass spring at the oil filter mounting pad failed. It not only dislodged itself, circulating through out my motor but it allowed unfiltered oil to circulate, compounding the problem. The function of this bypass, for those who don't know, is to allow oil to flow passed your oil filter in the event the pressure falls off due to high oil demand, like during high rpm operation. The bypass spring failure is rare but it happens, especially in oil filter mounting pads that have been around for many years. The spring is made of steel and breaks down like any spring will over time.

The cure is pretty simple. Unbolt the filter pad from the block. The spring and attached "washer" can be pried out and replaced with a pipe plug. This is done by carefully making threads with the proper sized tap. There is not a whole lot of "meat" in this area, so do it right the first time. Then insert the plug with the "permanent bond" Loc-tite or JB Weld. This plug is, interestingly enough, the same size as the three oil plugs above the cam in front of the block. So if you have a spare freeze plug set, your ahead of the game.There is also many manufactures of oil pads that have already been cast without the by-pass valve. The cheapest is from Perma-Cool at about $25.

Warning! You now have no bypass and there are some precautions you must now take. First you MUST change the oil every 3000 miles or less. And you must use a high flow oil filter like a K&N. The reasons are when your filter got plugged before, the bypass would allow oil to flow so at least you had lubrication, albiet dirty lubrication. Now there is no where for the oil to go but through your filter. If there is a pressure build up because of a dirty filter, you'll blow out gaskets! Anyone who maintains a high performance car won't have a problem with this kind of maintanance schedule and IMHO...if you are driving a SBC used for high performance use, you should not have a by-pass valve. Think about it. Your buzzing around at 6000 rpm or more. The last thing you want is unfiltered oil circulating through your motor at this high load condition.

 

I agree, as do several publications, that the bypass is evil and must be eliminated. 1/4" NPT tap and pipe plug, with a good coating of red thread locking compound, does the job.

Not sure I agree about MUST change the oil @ 3K miles tho...if you're using synthetic oil for example. I'd add that a nice gentle engine warmup is needed, let it tick over when first started for a minute or so, and don't jump on it until it's up to temp. Again thinner synth oil mitigates most of the risks involved.

 

Good points. The 3000 miles is safety valve to promote caution in ones who tend to push the maintanance envelope....but there are none to those people on this site. Thanks for the exact size of the plug.

 

Will a failure of the bypass spring cause a drop of oil pressure?
I have a brand new engine, didn’t even drive the car yet, I replaced the oil and filter after like 15 min of idle. I was in the process of burning chips to correct the idle, then a friend revved the engine around 5000 and the oil pressure that used to be around 60 psi, dropped to zero.

The engine had idled for more than 1 hr in total, I was using 10-30 oil. Is this the right oil weight to use?

Engine:

383 sb
Superam
AFR190s
etc,

I hope the engine is not damaged so I don't have to kill my friend
.

 

Maybe for an engine that lives at high RPMs...aka circle track...but I see no reason to plug the bypass on a street engine.

Bypass is there to accepts bypass of pressure as well, and maintain correct engine oil pressure (in combination with bearing clearances, etc).

My advice is to not plug the bypass.

 

I agree with Mike. Its better to have the bypass for safety reasons rather then to not have it and blow the oil filter off and yes Ive seen it happen. I personally would rather have dirty oil flowing through my system then have no oil due to a plugged filter or extremly cold oil. I dunno maybee the lesson is to replace the oil filter adaptor with a new one on a new engine.

Primo, I doubt the 5k rev out and out blew the engine. Most likely its a disconnected/faulty sender or worst case the oil pump drive connector busted. If you used a plastic connector then I wouldent doubt it.