Frank;

I guess the only way to really proove there are gains or not in a measurable way would be to build to identical motors, one with the block reliefs and one without. I spoke to an engine builder down on Long Island (a friend of a friend) who said he did  very similar reliefs on 351 blocks. I'm just sayin'

  Ron Lane,  Meridian, ID

I've also talked to Gord and he has sent me a lot of info as well. I believe that like John M and Ted, Gord does a number of things because of his experience.

Quote from Gord on the subject:"The valves are shrouded by the deck surface in a Y-block because the combustion chambers hang over the sides of the block.  This restricts the air flow into the cylinders".

Does it lower CR? Maybe, but then you can run more boost. Does it mess with turbulence? Don't know, but great quanities of air are being forced in by a blower or turbo.

Joe Abbin of Roadrunner Engineering (blown flatheads for the street) has done extensive dyno work and has imperical data to show that in flatheads, the slight loss of power due to lower cr is more than made up for by improved airflow and the increase in power it provides. Yes, I know, that's a flathead, not a y block. 

Don't know if it works, don't know that it doesn't.  But how many with high performance Y blocks are doing the little bit of block relieving that Ted showed us.

Just sayin'................

Missouri Mike

I'd rather be lucky than good.................

    but good ain't bad!!

I'd really like to see some substantial proof that it works before I chopped the block. I can actually see a couple reasons why it would detract from the hp numbers. Lower compression and driving mixture away from the plug during compression. I'm thinking that if there was a benefit, Ford would have done it on the F codes.

No shortcuts. There is a benefit to porting a supercharged engine. If you can attain the same flow with less blower pressure, you can reduce that pressure and achieve the same power or more. There's less parasitic drag from the blower and reduced intake temperature. Obviously you want to help the exhaust side as much as possible, because you have really helped the intake with the blower. 

Frank/Rebop

Bristol, In ( by Elkhart) 

I want to thank everybody for their comments and thank Ted for his pictures and advice. I'm glad I checked the distance from the piston top to the first compression ring on the new forged pistons because that only measured about 0.250" as compared to the stock piston which was about 0.330". So, my relief will be shallower and I don't plan on going any deeper than 0.125" max. I'll post more pictures when I get it done.

Rono

  Ron Lane,  Meridian, ID

Here are some pictures of what I do.  This simply gives a bit of room around the intake valve when it’s fully depressed.  When using higher than normal lifts at the valve, this notch becomes mandatory in that it keeps the intake valve off the edge of the cylinder.  When notching the cylinders, make sure the notch does not get into the top ring area of the cylinder.

 

 

 

 

 

Lorena, Texas (South of Waco)

The value of some things done in modifying an engine are hard to measure (unless you have a dynamometer). IF you look up the bore of a y-block with the cylinder head in place the valves are significantly shrouded. Relieving the block (flathead Ford terminology) is an effort to improve volumetric efficiency not unlike porting cylinder heads.



Yes, you are modifying the combustion chamber shape. Yes, you will slightly increase the effective combustion chamber size, you will slightly decrease the compression ratio, and you will change the turbulence in the combustion chamber.



When I have done this, it has been on normally aspirating engines, not supercharged or turbocharged. I mention this because some feel that even cylinder head porting is of less value when the air fuel mixture is pushed into the combustion chamber rather than merely drawn in by atmospheric pressure and the 5th cycle of the 4 stroke engine.



Make sure that the depth of the material removal is less than the top ring groove of the pistons you will actually be using. Although time consuming, I have finished the material removal by using a hand file to ensure a uniform taper from the gasket ring to the top of the cylinder bore.



IF you look closely at the pictures of Ted Eaton's EMC entry in Y-Block magazine earlier this year, you'll notice that the deck of his engine had the same relieving that you are proposing to do.



I think that little things do make a difference in the building of an engine. I like the way AussieBill put it.



Regards,

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Another opinion. If the purpose of grinding on your block is to unshroud the valves then I say don`t do it. Most sources I have seen recommend that the heads should be relieved not the block. Since you are using a blower that may not be very important anyway. And modern theory is that swirl of the intake charge is more important than absolute airflow. And the valves are really only shrouded at low valve lifts so what do you hope this will gain. Like I said, just an opinion. Pete

Hi

Im new to the forum, but this is my 2 cents.  If you understand the risks and you can afford to possibly ruin this block, then i say go for it.  Remember that buy doing this you will be lowering the compression ratio.

Hope this link helps

http://www.streetrodderweb.com/tech/0905sr_ford_flathead_myths/index.html

I have done this block relieving on y blocks for years and see no problems if you go carefully. Many of us have little pecularities/features that we like to do when building engines, After being on here for a fair while it sure is obvious that a majority of relative newcomers seem to want to reinvent the wheel or y block. Go with your idea carefully and doubt you could toast your block. Just my opinion. regards bill.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Okay, Gord McMillen has been providing me the info and pictures. He has built and raced quite a few supercharged Y-blocks and is manufacturing the blower kits for y-block set-ups. His rationale for the block relieving is so the motor can breathe better under boost considering the typical valve shrouding of the Y-Block heads. Maybe the 471 heads I'm using pose less of a problem than the "G" heads or Mummerts new aluminum heads, I'm not sure, but if you guys think I can skip taking the risk on doing this (one bad slip and the block is toast), I'll be happy to pass on it. below is one of the pictures that Gord sent me.Rono

  Ron Lane,  Meridian, ID