We've all heard one time or another that a stiffer block will seal the rings better and make more power. Does anyone have dyno results proving this, though?

We do now.

One of my friends owns Wall-2-Wall Race Engines in Livingston, LA. They have a high quality machine shop and pride themselves in the accuracy of their machine work. They build offshore race boat engines (namely the ones in the Popeye's boat), SUPR dirt track engines, drag engines, etc. . .

They built a 406 for a friend of mine with 11/1 compression, AFR 210 RR's out the box, 260/270 @ .050 solid roller with .660/.660 lift, Victor Jr. intake, and a Holley 750. The motor was pretty stout and made 633 fwhp and 548 ftlb torque on motor.

After spraying it a few times, the stock 400 block cracked. Wall-2-Wall built him a new engine using all the existing parts, but switched to a Dart Little M block.

They just started playing with it on the dyno and the best pull so far is 637 fwhp and 572 ftlb.

With only a block change, the motor gained 4 hp and 24 ftlb torque. They also expect it to pick up some more power after thrashing on the dyno and tuning.

Mike

 

Good numbers on both engines, but they were two different engines. I suspect they may have used new rings, bearings and perhaps even pistons.

Unless the deck heights were exactly the same and cylinder bores and lifter bores were in exactly the same locations, it's difficult to credit the extra torque & hp to block stiffness alone. Most dynos can't measure friction hp, but that would be an interesting comparison, especially at high rpm.

One would think that block distortion would increase nearer hp peak than near torque peak and stiffer would help hp more than torque.

Thanks for the info. It will be interesting to see what happens when they spray. It does indicate that an accurate as well as stiff block is better.

 

I understand your point. However, this particular machine shop did all the machine work to both blocks. They keep build sheets and dyno tests so that a direct comparison was made. The bore was within .0002", both zero decked, same head gasket, degreed the cam the same, same PN piston, etc. . . It was as good of a comparison as any.

 

the only way that I could think of doing a direct comparison would be to dyno a built motor, then tear down the engine and concrete the block, reassemble, and redyno.

 

That's only .78% increase in power, there are too many variables to determine what the actual difference was. Like was said above, little differences in block to block can make that kind of difference, oil drainback direction to reduce windage and dripping oil on the crank.

What honing procedure did they use? Torque plate alone or hot hone? Was cylinder wall finish check on each block, etc, etc...

What were leakdown numbers on each motor?
How much wall thickness was left on that 400 block?

Just playing the devil's advocate...sounds like a great motor.

 

That was by Joe Sherman.

If the same shop prepped the cylinder bores both times thats one thing, but unless the first block was on a coordinate measuring machine and you could say both blocks were both accurate in terms of placement of the lifter bores and cam bore you can't just chalk this up to the block. Usually the accuracy will show up in oil temps though....

Bret

 

Jeez, you guys are really trying to pick this apart. I thought you'd find the dyno results interesting because I've never seen this comparison made before, but everyone is just pointing out how "invalid" the results are.

As far as the .78% increase in hp goes, I was more focused on the torque reading. Even though each engine made 50+ dyno pulls and the max's were compared, 5 hp on a 630 hp motor isn't much. Anyone who has any experience with an engine dyno knows that the readings can vary +/-10 hp from one pull to the next. HOWEVER, the 24 ftlb is definitely a consistent and measurable gain.

Both blocks were prep'd identically, from the hone finish (this shop particularly prides themselves in hone finish) and procedure (torque plates, cooling between measurements), to the oil drain back (lifter drains plugged, other drains screened), windage tray, etc. . .

 

Mike, it's very interesting info, but picking stuff apart is what everybody in Advanced Tech does. Chalking it up to block stiffness may be jumping to conclusions, but I believe it's probably a pretty darn good comparison of stock blocks and aftermarket blocks.

I'm interested in all the TQ and HP numbers. Before we state or accept anything as fact, we have to be sure the difference is statistically significant.

 

I don't think people are "picking" anything apart. All I see is an attempt to point out that all the variables may not have been controlled, or asking for verification that they were controlled. When you think about it, just the fact that the original engine appears to have used a factory 400 block, and the rebuild used a Dart block could make for a major difference in the engine's output. The temperature profiles in the block are going to be totally different, owing to differences in the casting design.

 

does the aftermarket block have siameised (spelling) bores. The 400 blocks arent known for there ring seal anyway due to the bores!

 

I've personally seen ~15hp from an innards swap. Windowed a factory 2-bolt 400 block, replaced the broken pieces and built an identical engine on a Dart block. Who knows what all contributed to the power increase.

I do know this much, guys were consistently gaining ~3% going from production blocks to full CNC bowties years ago. The extra beef in all the really critical areas are definitely a plus for guys building 400 based engines.

Mr ED,
Yes, they're siamesed but that's the least of the problem.

-Mindgame

 

What exactly is the weak spot of factory 400 blocks?

 

Nova- I don't push engines anywhere near as far as a lot of guys around here. AND I'd be doing handspings if I could build the same engine twice and get within 1% power difference, but like was said above, there's a ZILLION variables that contribute to power and I can control maybe 20 of them at a time, given my modest resources.

Damon's favorite weak points in factory 400 blocks:

1. Head bolt threads that pull out. First ones that go are usually the outside bolt holes, 2nd from the back on both sides (while going the final torque round on the head bolts). If one goes the other side will follow shortly. Never blown a head gasket becuase of it, but you gotta wonder what the real clamping strength is on a head gasket with the bolts screwed into a factory lightweight casting.

2. Cracks in the deck surface between........ well, name any 2 holes of any type in the deck surface and you'll eventually see a crack between them if you play with factory blocks long enough. Top side steam hole to nearest head bolt hole is my personal favorite. If you overheat the motor you'll get a crash course in this subject.

3. Main webs. I agree with conventional wisdom that 2 bolt blocks are stronger than 4 bolt, but not by much. Doesn't seem to matter what you do to them (including installing aftermarket 4-bolt caps on a 2 bolt block), you'll eventually push it far enough to get cracks. Doesn't surprise me that a factory block got cracks at 600+HP at all. I've done it at 200 less than that with a block that previous passed a magnaflux. Then again, I've had factory 2-bolt blocks with stock main caps push well past 500 on occasional nitrous use and run for years without problems.

Oh, the joy of 1970s-vintage quality control!!

400 blocks are like a box of chocolates.... you never know what you gonna git.

 

Maybe the aftermarket people have tougher standards about the metal of the block. I'm not sure about metalurgy, but in chemistry contaminants can effect the melting/boiling ponts. So I'd guess that contaminants in the blocks metal could cause it to expand more/less, or unevenly?
When the the block is poured from the molten metal, could getting that top gop (term for that?) in your cast vs. getting a the middle, good stuff without the contaminants account for factory freaks?


P.S. Its cool to see someone disregarding money and taking a scientific approach to power gains.

 

I chalk some power to aftermarket blocks b/c I too have seen it. I have also seen a engine dyno 710HP on one dyno and it was put on a shelf then we dyno the same engine and get 710HP on ours two years later after sitting up that whole time so dynos are closer than people give them credit. Later Clint