[gtofreek]

Originally Posted by Stan Weiss

I have seen those flow tests numbers a number of times and they along with the depression they were tested at do not add up. If we use 12" water for McCarthy's numbers and convert then to 28" water I get.

.1 111.51
.2 198.58
.3 226.07
.4 236.77
.5 245.93
.6 248.99

If we use 15" water for McCarthy's numbers and convert then to 28" water I get.

.1 99.74
.2 177.61
.3 202.21
.4 211.77
.5 219.97
.6 222.70

Stan

I've never had luck converting from one flow depression to another. I have flown the same port, at the same time at 10", 25", and 28". When I do the math, according to these converters, they never convert to what the head really did. I've come to the conclusion that they just don't work because of variables they can't possibly take into consideration. The higher depression you flow it at, the more the velocity gets, and the more things change. It's not a constant. A lot of mathematical calculations just don't seem to work in the real world of engines. I take them all with a grain of salt.

I stick to the ones that really work, like the HP formula, inch's to millimeters, the CID formula, etc. to name a few.

[gtofreek]

I woke up this morning from a dead sleep, rolled over and looked at the clock. It was 4:13! I think this is going to be a good day!

[Doug]

Originally Posted by gtofreek

I woke up this morning from a dead sleep, rolled over and looked at the clock. It was 4:13! I think this is going to be a good day!

I get a feeling like that whenever I happen to look up and the time is 4:21! (All hands together!)

[Skip Fix]

I like those pistons!

[gtofreek]

They are a CP Bullet shelf piston now!

[68azbird]

Originally Posted by gtofreek

A lot of mathematical calculations just don't seem to work in the real world of engines. I take them all with a grain of salt.

Amen
X2

[rohrt]

Pistons look nice and shiny Love this thread.

[71 T/A]

Originally Posted by gtofreek

I woke up this morning from a dead sleep, rolled over and looked at the clock. It was 4:13! I think this is going to be a good day!

I get the same feeling when the clock says 4:55.

[Skip Fix]

I also have found "numbers gone crazy" trying to convert flow bench numbers even using the Superflow correction factor.

[rohrt]

What is the benefit of the steel gas nitrided top ring? First I heard of them.

3.75/2=1.875+6.7=8.575
assuming deck height = 10.243
0 deck hight would have to be 1.668
If you piston CH is 1.630 that is roughly .038 you will have to take off the deck?

Is that pretty normal to remove that much off the deck height? Is it better to have a taller CM piston at the expense of weight? At what point will you have intake fitment issues?

[gtofreek]

Originally Posted by rohrt

What is the benefit of the steel gas nitrided top ring? First I heard of them.

Steel gas nitride ring is a strong, durable, high heat ring. The gas nitride is a hardening treatment. This makes a ring with no coating on it. This makes it good for nitrous, or boosted applications as well as N/A. Problem with coated rings like Moly or chrome is the coating can flake off from the thermal shock of nitrous or the torturous abuse of boosted apps. Moly is good all around ring for N/A performance apps, but not the other uses. Nitrous, and boosted apps need either steel gas nitride, or a hardened ductile iron[Hellfire] top ring if you want it to last.

Originally Posted by rohrt

3.75/2=1.875+6.7=8.575
assuming deck height = 10.243
0 deck hight would have to be 1.668
If you piston CH is 1.630 that is roughly .038 you will have to take off the deck?

Is that pretty normal to remove that much off the deck height? Is it better to have a taller CM piston at the expense of weight? At what point will you have intake fitment issues?

The compression height is where it is because of a couple reasons.

1. People are using them in 40 year old engines that have probably been rebuilt before, and possibly been decked. This allows room for another deck job to clean it up good.

2. I have seen original, untouched factory 400 and 455 blocks come in anywhere from 10.250"-10.220". At 10.220", this only leaves you .015" to square up and zero deck a block. I had one Pontiac block that the deck was sloped .015"" before. Yeah, .015"! It started out cutting all the way across the deck, but about half way, the outside rear corner started sloping off, and quit cutting on it. It took .015" to get it cleaned all the way across. I've seen other blocks as far off as .020" from one side to another{not a Pontiac]. Back then, the machining was far from perfect, and sometimes it takes quite a bit to clean this stuff up. We always square deck, and deck at a 90° angle to the cam/crank centerline. This makes a truly square block, then it can be decked to whatever deck height you want.

On my engine, depending on where the heads come out at, will either have the piston at zero deck minimum, or preferably .005" out of the hole.

CP only offered this piston in .030", and .040" oversize. We talked to one of the piston guys at CP that we deal with and told them that these engines are old, and have probably been rebuilt, and bored oversize in the past, and 400 blocks are getting harder to find, so they should make them in .060" over also[for my case]. He talked to the head honcho, and they decided to offer it in .061" over now.

Which brings me to my next point. This is no longer a 413 build, now it's a 412 build, since the piston is made for a 4.181" bore, so a 4.185" ring can be file fit to use. I thought they were going to make it for a 4.185" bore.

Damn, don't know if I'll meet my power expectations now, without that cubic inch!

I'm going to have intake fitment issue anyway, so that's no problem for me, but normally, it would just depend on the intake being used, and how much a particular deck needed to be cut. Some intakes like the RPM usually need to be cut anyway. They usually sit too high.

[blueghoast]

I like it when I look up at the clock and the wife is turning off the alarm
And knowing I can go back to sleep for a while knowing that she's not
Hogging the bed and snuggled up next to me and snoring like a freight
train in my ear. Now That's A Good Day. LOL

GT.

[Alvin]

Subscribing. Great thread.

Question:

CP only offered this piston in .030", and .040" oversize. We talked to one of the piston guys at CP that we deal with and told them that these engines are old, and have probably been rebuilt, and bored oversize in the past, and 400 blocks are getting harder to find, so they should make them in .060" over also[for my case]. He talked to the head honcho, and they decided to offer it in .061" over now.

Paul: Besides the "557 'thin blocks'" as a builder are you comfortable with a .061 over 400s as street builds?

Reason for my Q: I'm thinking the notorious overheating issues etc. reason is I've diff 400s to consider building...'69, '73, and spare '78 W72.

Reading this thread has got me thinking of working our other 400 - '67 GTO w 670s & 4spd...

[gtofreek]

I don't worry about .060" over at all, and I live in the desert! I have done several 389's at .090" over and they don't overheat. The overheating issues aren't from being bored out, it's more from the lack of sufficient water jacket in the heads, which is where the majority of the heat is. Just make sure the cooling system is good to go with the cooling mod tricks, and what not, and they'll be fine.

If you think about it, a block that is .060" over compared to one that is only .030", the cylinder walls are only .015" thinner on the .060" block. That's just 5 sheets of paper! If .015" is enough to make it overheat, then they were too thin from the factory. Even at .060" the cylinder walls are still .100" thick or thicker. The 389's I did .090" over, were around .090" on the sides of the cylinders[in between cylinders] and over .100" on thrust sides. They are fine.

[gtofreek]

Well, I'm not happy with my chamber mods. They helped the exhaust a little, but did next to nothing for the intake. On a brighter note, I did find several things that DON'T work in creating more flow! I'm sure the mods will help with swirl though, which is some benefit. I think the flat chamber floor is hurting it also. I don't really like the shape of the chamber I did. It's not what I had pictured in my head. Will try a different shape on another chamber.


Now back inside the port!

[gtofreek]

Here's a pic of head sitting on block.

[Alvin]

Originally Posted by gtofreek

I don't worry about .060" over at all, and I live in the desert! I have done several 389's at .090" over and they don't overheat. The overheating issues aren't from being bored out, it's more from the lack of sufficient water jacket in the heads, which is where the majority of the heat is. Just make sure the cooling system is good to go with the cooling mod tricks, and what not, and they'll be fine.

If you think about it, a block that is .060" over compared to one that is only .030", the cylinder walls are only .015" thinner on the .060" block. That's just 5 sheets of paper! If .015" is enough to make it overheat, then they were too thin from the factory. Even at .060" the cylinder walls are still .100" thick or thicker. The 389's I did .090" over, were around .090" on the sides of the cylinders[in between cylinders] and over .100" on thrust sides. They are fine.

Thxs. Reason for the Q was it has often been written on certain blocks not to go over ".xxx"

I'm sure in your profession you've heard the same, and point understood and taken your desert enviro that would manifest overheating if there were a problem w .060" or more.

[Matt Meaney]

since your doing a 2.20 rod journal, any consideration to offset grinding to a 3.79 stroke?

[gtofreek]

Originally Posted by Matt Meaney

since your doing a 2.20 rod journal, any consideration to offset grinding to a 3.79 stroke?

No, for the little I would gain, it would make the main/rod journal cross section thickness, that much thinner. I want the strength. I'm, already loosing some due to the 2.2" journal. De-stroking it would keep it the same that it is now, but then I would need a custom piston. Keeping it stock stroke, should give me enough room to get a good deck height. This engine has been rebuilt before. Stroking it .040" would also probably require me to use a custom piston as that extra .020" of height, would then put me on the edge of even being able to deck it to where I want to be.

[gtofreek]

Rods came in today. They are Callies 6.700" BB Chevy rods with L-19 rod bolts. These rods have a lot of support on the big end, and around the rod bolts.