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Old 04-04-2009, 08:26 PM
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Olds 455 Oil Restrictors

I am in the process of replacing the bearings in my Olds 455 powered jet boat.
It appears that the previous owner put the Mondello main bearing restrictors in mains 1-4. Has anyone used these before?
I'm questioning if the restrictors have been pressed far enough into the galleys.
I enlarged the upper bearing oil holes to 5/16" but the restictors still don't line up with the holes in the bearings and I am concerned if I will have enough oil flow to the bearings (see attached photos).

Since I'm replacing the bearings due to apparent oil starvation on the #4 main, I want to make sure I don't run into the same problem again.
Any suggestions or advice would be much appreciated.
Thanks!
Elm
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Old 04-04-2009, 08:54 PM
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The hole needs to be elongated to expose the restrictor hole. Use a rat tail file to do this, or a Dremel if you have a steady hand.
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Old 04-04-2009, 09:02 PM
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Worthless item?

After reading my factory shop manual for the Olds 455, it appears that these restrictors for the cam bearings are really pretty useless.

The issue with Olds oiling is that too much oil gets pumped to the heads via the lifters- These restrictors only restrict the oil going to the cam bearings, not the lifters. These two functions take totally separate paths. How is restricting the oil to the cam bearings going to help with anything? The amount of oil going to the heads isn't affected so why starve the cam for no reason?

Unless someone has a compelling reason why I'd want to keep these in, my instinct is to yank them out and throw them away.

Thoughts/Comments?
Thanks!
Elm
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Old 04-04-2009, 09:20 PM
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The idea is to keep the oil at higher revs from getting to the top end of the engine quicker than it can return. In other words, to keep more oil in the pan.
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Old 04-04-2009, 09:24 PM
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Cam bearings in my book is still considered 'lower' end.
There is no restriction for the oil to get back to the pan from the cam bearings.
The restriction is from the tiny little oil return holes in the heads keeping the oil up there.
Am I missing something?
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Old 04-04-2009, 09:28 PM
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The holes feed the cam bearings then the top end. By restricting the flow of oil to the upper end, it keeps more oil in the pan.

Mondello uses them on everything from the 307 to the 455.

Don't want em? Then don't use em!
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Old 04-05-2009, 06:33 AM
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Quote:
Originally Posted by cobalt327
The holes feed the cam bearings then the top end.
Not on a Olds motor they don't. As the OP noted, a quick look at the factory service manual shows that the Olds oiling system feeds the lifters off the main galleries FIRST (which also feeds the top end), then the mains, and the cam bearings last. Putting the restrictors in the cam bearing feed holes only restricts oil to the cam bearings, nothing else. To restrict oil to the top end, you need to insert restrictors in each of the 16 lifter feed holes off the main galleries. The cam bearing restrictors are worthless but Mondello sells a lot of them based on misinfromation and the fact that they are easy to install.
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Old 04-05-2009, 07:48 AM
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Thanks for the clarification- I stand corrected.

If the bearings were modified as they were supposed to be, I do not believe any damage was done to the OP's mains because of the restrictors. They might not help much, but they do help some amount, IMO.

Like I said earlier, Don't want em? Then don't use em! lol
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Old 04-17-2009, 01:34 AM
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Oil-restrictiong push rods

I spun a rod bearing in a 350 Olds engine, I believe, due to oil starvation. This seems to be a theme with Oldsmobiles. I am currently building a 455 and have done a lot of reading and talking to other Olds guys. The general consensus from everyone except the guys who sell them, is that the oil restrictors in the oil galleries between the main bearings and the cam bearings are worthless. Besides, common sense dictates you do not want to restrict oil flow to any bearing. Adding restrictors to the lifter bore will, admittedly, slow the flow of oil to the top of the engine, but I not sure what the sacrifice may be in terms of reduced oil to the lifters, especially if they are hydraulics. In the 455 motor I am currently building, I have opted of oil-restricting pushrods. These will not restrict oil flow to any bottom end component, but will restrict flow to the top end.

This solution was suggested by a well-known old school motor builder who is still at it in Buena Park, CA and has lots of Olds-powered boat experience. He speaks from his experience and he's a straight-shooter. I trust his advice with this solution.
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Old 04-17-2009, 08:31 AM
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Quote:
Originally Posted by Oldsfart
I spun a rod bearing in a 350 Olds engine, I believe, due to oil starvation. This seems to be a theme with Oldsmobiles. I am currently building a 455 and have done a lot of reading and talking to other Olds guys. The general consensus from everyone except the guys who sell them, is that the oil restrictors in the oil galleries between the main bearings and the cam bearings are worthless. Besides, common sense dictates you do not want to restrict oil flow to any bearing. Adding restrictors to the lifter bore will, admittedly, slow the flow of oil to the top of the engine, but I not sure what the sacrifice may be in terms of reduced oil to the lifters, especially if they are hydraulics. In the 455 motor I am currently building, I have opted of oil-restricting pushrods. These will not restrict oil flow to any bottom end component, but will restrict flow to the top end.

This solution was suggested by a well-known old school motor builder who is still at it in Buena Park, CA and has lots of Olds-powered boat experience. He speaks from his experience and he's a straight-shooter. I trust his advice with this solution.
Restricted pushrods are an excellent and easy way to limit top end oil in an Olds motor. Deburring the passageways where the oil pump attaches to the rear main cap is also a good idea.
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Old 02-14-2012, 10:04 PM
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Another thing you can do is to enlarge the drainback holes in the heads & block (see before & after pics)
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Old 02-15-2012, 11:18 AM
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Quote:
Originally Posted by ezobens
I am in the process of replacing the bearings in my Olds 455 powered jet boat.
It appears that the previous owner put the Mondello main bearing restrictors in mains 1-4. Has anyone used these before?
I'm questioning if the restrictors have been pressed far enough into the galleys.
I enlarged the upper bearing oil holes to 5/16" but the restictors still don't line up with the holes in the bearings and I am concerned if I will have enough oil flow to the bearings (see attached photos).

Since I'm replacing the bearings due to apparent oil starvation on the #4 main, I want to make sure I don't run into the same problem again.
Any suggestions or advice would be much appreciated.
Thanks!
Elm
One can see the restrictors are not placed properly and the worst is #3 where the restrictor has cut off flow from the pressure drilling to the bearing.

The Olds flows from the main galley via a drilling to each main bearing. It then taps drillings for the lifter galleys and the cam bearings using the back side of the bearing shell to close the passage.

Most main bearing inserts don't align the that bearing's feed hole to the crank journal depending instead of flow around the shell to the other distribution holes to suffice as a feed to the mains. I always considered this arrangement weak in terms of flow and similar to Cobalt, I align the feed hole in the bearing shell with the feed drilling, I prefer using the Dremel with a stone bit for the fine finish it leaves and minimum disruption to the actual bearing surface adjacent to the new hole. Left to my own devices I don't use restrictors as in my opinion they are a so-so fix aimed at the real problem which is the hole location in the bearing shell doesn't match the feed hole, depending on fluid transfer in that small slot to feed the bearing and the other two holes. The restrictor is an attempt to force more oil into the bearing at the cost of the upper end. These wild theories about drain back get sold to sell these parts, but as you can see with main #3 the feed to the bearing is greatly compromised by the position of the restrictor.

Boat engines always work hard compared to an automotive installation, the high volume oil pump is a good investment with the boat motors.

Bogie
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Old 02-15-2012, 11:53 AM
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You guys realize this post is almost 3 years old?
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Old 02-15-2012, 02:17 PM
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Quote:
Originally Posted by FmrStrtracer
You guys realize this post is almost 3 years old?
Just wanted to add my fix on what works.

People are still building 'em, ya know?
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Old 02-15-2012, 04:48 PM
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Quote:
Originally Posted by oldbogie
The Olds flows from the main galley via a drilling to each main bearing. It then taps drillings for the lifter galleys and the cam bearings using the back side of the bearing shell to close the passage.
I'm afraid that is not quite correct for Olds motors. Please see posts #3 and #7 above. The Olds oiling diagram is in the factory Chassis Service Manual. Oil from the pump flows directly to the main gallery that is the one that feeds the driver's side lifters first. A drilled passage from this gallery then feeds each of the mains, and from there additional passages feed the passenger side lifters and the cam bearings. Unlike Chevy motors, there is no dedicated main gallery that feeds the main bearings first. The only way to restrict oil to the rockers is with restrictors in the lifter feed holes, or with restricted pushrods.

As a side note, I have GM factory service manuals spanning the 1940s through the 1990s, from Olds, Chevy, and Cadillac, and every one of them calls these passages oil galleries, not galleys. Per Webster, one definition of gallery is a long narrow passage.
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