Thanks,

Rono

Thanks,

Rono

Rono

Afraid I can’t see your posted chart on my end.  With blown applications, my own preference is thicker cylinder walls than I’d run in a normally aspirated situation.  The 0.125" number Frank throws out there would be good if you can keep it there or higher.  Keep in mind that the major and minor thrust sides of the cylinder wall can be used in your favor if there is some variance in cylinder wall thickness occurring.  If your sonic test sheet shows multiple values per quadrant, then pay particular attention to the lowest values.

Here the link to a past thread showing a sonic test sheet for a 272 that was bored too much.

http://www.y-blocksforever.com/forums/Topic15189-3-1.aspx 

Chuck

Rono

Rono

     That's close to what I'd call a minimum. The extreme cylinder pressures created by a blower will actually bow the cylinder walls outward, causing the rings to lose some sealing qualities. I don't think you can offset the bores much in that direction, but Ted or Lonnie may know a trick in that area I'm missing. Ask him, then tell me hoe=w the H--- he does it!    

I see what you are saying with respect to the #1 cylinder minor thrust (middle). The #1 cylinder major thrust (middle) has alot heavier wall and I'm not sure how/if there can be some compensation there. I did make a few mods to this C2AE block to reduce crankcase pressure. One thing I did was drill out the road draft blank on the block so it could accept the stock road draft canister/tube. I also cut valve reliefs in the block and I'm planning on running 2 of the Moon valve cover breathers. I'm hoping these mods will reduce any excess pressure. I was more concerned with overheating if the cylinder walls were too thin.

Rono

The area I'm talking about is the actual Cylinders. They'll actually bow out from the combustion pressure if the walls are too thin. Better to be a little smaller in displacement and have stiff strong cylinders that seal up. Especially with the blower. there when you want more power, add boost!

As Charlie mentions, timing cover and bellhousing measurements refers to the front and rear of the cylinders.  I’m going to assume at this point that the cylinder numbering is true to the Ford engines and not the scrubs.  You need to ask R&L this just to verify as it makes a big difference in interpolating the values.  But I’ve taken the values you have and based on them being real Ford Y Cylinder numbered values, I’ve put them on my own sheet to make it easier reading.  Looks like this:

If this had been a virgin block, then offset boring the cylinders would have helped to center the bores.  But another 0.030 overbore only requires 0.015” off each side so the current block is doable in that regard.  If you’re talking more than 10 lbs. of boost, then a small amount of block fill would be of some benefit but that needs to be done before the cylinders are final bored.  A plus to your particular block is that the major thrust side measurements are already better than the minor thrust sides.

Frank is right in that boost pressure deforms the cylinder walls.  Having additional crankcase breathers are not going to be much help in that regard.  Here’s the sonic test sheet for Randy’s block which was running 15 lbs. of boost and making gobs of horsepower with injected alcohol.  These cylinders were offset bored to minimize issues with casting core shifts.

Ted;

According to John Erb, this supercharger will put out less than 10 psi boost with the high output impeller (he says 7-9 psi max). I appreciate you taking the time to transpose the numbers to your format. Much easier to interprete. I'll forward that to R&L Engines and see what they have to say. It's not too late to put the brakes on this block work if the motor may blow under moderate boost pressures.

Rono 

Two more things about what Ted's telling you, and I learned from a couple years in a foundry. The cores are not terribly consistent and smooth. Hopefully you are seeing MINIMUM readings in the areas described. A 1/4 inch away from that reading it could deviate.

     As you can tell from comparing your block, core placement in a mold is not accurate in terms that machinists use. We think a +/- .030" core location is pretty good. Remember, your'e placing a 100# block of sand into another core. Likely these cores were made in two or more different core cavities, so they're not exactly identicle and fit differently. Get's to be pretty tricky to be consistent. Lastly as the tooling gets older, repairs and wear will cause the cylinder bores AND the water jacket to increase in size. Castings from older tooling will then have smaller walls as cast. You can't do anything about this but what you've done. I would definitely agree with Ted, if you can get by with .030, use that.

Rono

That's a good thought. I'll talk to the machine shop Monday and then give John M a call. So you guys naybe seeing a set of Probe Forged pistons and rings in the classified section soon.

Rono

I'm not familiar with block fill. How do they do that and can most shops do it?

Rono

Rono

Most of the block water circulation takes place in the upper part of the block.  By using block fill in the lower portion of the block, then cylinder wall integrity (rigidity) is increased by simply shortening the amount of cylinder wall that can flex.  The shorter the unsupported part of the cylinder wall is, then the more rigid it becomes.  A side benefit to using a given amount of block fill is that the block cooling system can actually be more easily temperature controlled simply due to the coolant in the block being refreshed or purged much more quickly.  Less block coolant equals a quicker turnover time.  New engine designs now take this into account so that the engines can warm up more quickly for emission purposes.