The subject has been discussed numerous times but a recent Hot Rod Magazine article has prompted me to bring it up.  A switch from conventional to synthetic oil picked up 15 horsepower on the dyno. A local reputable engine builder confirms this. According to a previous post Ted does not recommend synthetic. It’s my understanding that Mobile recommends 10w40 High Mileage for flat tappet cams. I used Valvolene VR1 for break in and after break in with no problems. Picking up 15 horsepower by switching oil appeals to me but not at the risk of destroying a cam.  Opinions please and actual experience please.  I ran Mobile one in a previous build of the same engine for a while with no problems but I’m overly cautious about damaging the build. It runs too good to mess it up. 

As a contestant or team member in four EMC challenges with my own engines, I did not find more than 6 or 7 horsepower difference with my 375Y, and about the same with the 303Y.  I changed AmsOil 30W break-in oil for 10W-30 synthetic, and did approximately 70 dyno pulls with no issues with bearings, or rings, etc.  We made 595hp on Ted's dyno, and changed to 5W-20 AmsOil synthetic and did not pick up any hp.  On the rebuild, we made 613hp with the 375Y and I used the 30W break-in oil again, and changed to 10W-30 full synthetic, for no change in horsepower.  At EMC when changing to 5W-20, there was no measurable difference over the 10W-30.  We made 12 or 13 full dyno pulls in 25 minutes, and had no issues with the AmsOil.  I have 10W-30 AmsOil synthetic in my '55 Thunderbird with 345Y and so far it has been flawless in performance.   I can't speak for any other brand of oil, but the AmsOil does work for me.  Joe-JDC

JDC

Which AmsOil did you use? There are several types.  

Not sure about Joe, but I'm running the Amsoil Z-Rod 10W30 for a couple of years now and it seems to be fine.  I don't have any scientific data on my end, though.  The Z rod is supposed to be high in zinc.

I don't have any scientific info on synthetics, however on older engines, apparently they  tend to aggravate leak issues..

Paul

Paul

Ran Mobile1 with no worse issues with leaks a long time ago.Mobile1 10w40 high mileage is supposed to have high zinc and be recommended by Mobile for flat tappet cams but I thought I saw on a post somewhere that Ted had a problem with it.  

I'm not having much luck trying to remember exactly why Ted doesn't use/recommend synthetic oil. I think he said something about the lifters not rotating when using synthetic, but don't quote me. I'm sure Ted will revisit this upon reading the posts. More recently, I asked Ted about using  Valvoline 10w-40 ATV/UTV conventional oil, which has 1020 ppm zinc/930 ppm phosphorus.He said he wasn't familiar with it, but there is more to motor oil than zinc and phosphorus content. By the way, the Valvoline 10w-40 conventional 4-Stroke Motorcycle oil has 1120 ppm zinc/1030 ppm phosphorus.     

See if some of these links to past threads help.

http://forums.y-blocksforever.com/FindPost163955.aspx

http://forums.y-blocksforever.com/FindPost151780.aspx

http://forums.y-blocksforever.com/FindPost101544.aspx

Lorena, Texas (South of Waco)

Thanks Ted. Found the part where you said not to ever use synthetic in a Y Block. You definitely know more about Y Blocks than anyone  so I’m going with your opinion. I was hoping to pick up a few horsepower by switching oil. It’s not worth taking the chance of damaging the engine. I’ll continue using Valvoline VR1 Racing oil. I may switch from 20w50 to 10w40 or 10w30. Should could lower resistance and pick up a little bit of power. I appreciate all the input.