GM's EOS

[G A.]

Back in the day, what made EOS right for break-in's and engine assembly? Would there be anything available today that you would add to CJ-4 oil for your dyno break-in with a hard-lifter cam?

Dan

[John H.]

Re: GM's EOS

Back in the day, what made EOS right for break-in's and engine assembly? Would there be anything available today that you would add to CJ-4 oil for your dyno break-in with a hard-lifter cam?

Dan

Dan -

EOS is still available, and the major cam manufacturers all have their own break-in additives (in addition to their assembly lubricants).

[G A.]

Re: GM's EOS

Thanks John. Yes I know you can still get it. But what made it desirable, as far as GM was concerned, and is there anything today that would supplant it? Nothing outside of what GM used in the rebuild.

[Duke W.]

Re: GM's EOS

EOS is simply a mineral oil with a high dose of ZDDP that increases the level of ZDDP for break-in over and above the level in any API certified oil.

AFAIK, GM did not use "assembly lube" on lobes and lifters nor add EOS to the plain, vanilla API oils they installed at the engine plants.

Moreover, no "engine break-in" was done. In fact the first 30-60 minutes of engine operation was short periods of mostly idling as the car was driven off the line through roll test, then out to the lot, then moved several times and finally put on a rail car or truck. Then more of the same as it was delivered and moved around the dealership before finally being delivered to a customer.

I consider EOS to be optional to add to CJ-4 oil on fresh, restored engine, but not necessary if you use an assembly lube on OE equivalent cam lobes/lifters with the correct OE spring for the cam.

Guys obsess WAAAAAAAAAAAAAAAAy too much over this issue.

If assembly lube is used, the oil filter should be changed after the first 30-60 minutes of operation because the solids in the assembly lube are trapped by the filter and can clog it. BUT the oil should not be changed if EOS is used (or even if it is not used) - just add oil to the full mark to make up for that lost by changing the filter. Leave the CJ-4 "break-in oil", whether enriched with EOS or not, for at least 500 miles, but change the oil and filter by about 1500 miles, and at this first full oil/filter change nothing more than CJ-4 is necessary.

There is no need to change the oil and filter two or three times in the first thousand or so miles as some guys do.

But if you have an aftermarket cam with gorilla springs I can't offer anything other than "good luck".

[G A.]

Re: GM's EOS

Thanks Duke. I seem to remember that there was no break-in at the factory from an old-timer I worked with as a kid. Your info is very helpful as it is simple, for a simpleton like me.

Dan

[Bill M.]

Re: GM's EOS

Moreover, no "engine break-in" was done. In fact the first 30-60 minutes of engine operation was short periods of mostly idling as the car was driven off the line through roll test, then out to the lot, then moved several times and finally put on a rail car or truck. Then more of the same as it was delivered and moved around the dealership before finally being delivered to a customer.

Duke is right about engines delivered in vehicles, but I see the word dyno.

Chevrolet had a break-in procedure for engines we ran on the dyno in 1969. Before they were run at high rpm or full power, there was a break-in procedure, and it was longer and more gentle for the solid-lifter cams.

[Clem Z.]

Re: GM's EOS

EOS is simply a mineral oil with a high dose of ZDDP that increases the level of ZDDP for break-in over and above the level in any API certified oil.

AFAIK, GM did not use "assembly lube" on lobes and lifters nor add EOS to the plain, vanilla API oils they installed at the engine plants.

Moreover, no "engine break-in" was done. In fact the first 30-60 minutes of engine operation was short periods of mostly idling as the car was driven off the line through roll test, then out to the lot, then moved several times and finally put on a rail car or truck. Then more of the same as it was delivered and moved around the dealership before finally being delivered to a customer.

I consider EOS to be optional to add to CJ-4 oil on fresh, restored engine, but not necessary if you use an assembly lube on OE equivalent cam lobes/lifters with the correct OE spring for the cam.

Guys obsess WAAAAAAAAAAAAAAAAy too much over this issue.

If assembly lube is used, the oil filter should be changed after the first 30-60 minutes of operation because the solids in the assembly lube are trapped by the filter and can clog it. BUT the oil should not be changed if EOS is used (or even if it is not used) - just add oil to the full mark to make up for that lost by changing the filter. Leave the CJ-4 "break-in oil", whether enriched with EOS or not, for at least 500 miles, but change the oil and filter by about 1500 miles, and at this first full oil/filter change nothing more than CJ-4 is necessary.

There is no need to change the oil and filter two or three times in the first thousand or so miles as some guys do.

But if you have an aftermarket cam with gorilla springs I can't offer anything other than "good luck".

back in the day if you bought a new HP short block or long block there was a can of EOS in the crate as that is where i found out about it

[Reuben P.]

Re: GM's EOS

Clem is correct, all long and short blocks came with EOS. I worked for a Chevy dealer through the '60s and '70s EOS was added to every engine repair, straight EOS on the cam and lifters and a mix with engine oil for assembly lube. I don't remember a single failure on the engines. Throughout the '70s there were cam shaft issues, I believe there was a TSB about the use of EOS during replacement.

[Domenic T.]

Re: GM's EOS

I also remember the pint can in the crates that said GM engine oil suppliment.

STP and other thick VI's (viscosity improvers) were sold at major oil distributors for $ 3.50 a gallon.

There were advertising tests that you would see at auto parts and booths.

It was the screwdriver test to show how parts just slipped around together.

They would dip the screwdriver in regular engine oil and ask you to hold the screwdriver upside down by the tip with your finger tips, and you could.

Then in the engine oil suppliment (STP) and you could not hold it.

DOM

[John D.]

Re: GM's EOS

GM EOS #88862586. Make sure you get the right EOS from GM. I believe they have two. One of for the oil and the other is for lubricating the cam, etc.
The #888 number above is for the oil. JD

[Paul Y.]

Re: GM's EOS

Yes, the LT1 1970 short block that I just found comes with a can intact inside the crate. This is a lightly stamped CE block dated late 1970 and has been in a garage since shortly after that time just waiting for me to find it.