More info on "weak" V6's...
 

There's been a very large rift between some of the aftermarket companies claimed horsepower on the new DELTA 2.7L V6's, versus what some of our Korean friends have been telling us about the life expectancy of such setups.

Quite a few aftermarket places have been touting 240, 280 and 300+ horsepower setups on the V6 for a little while now. Key Motorsports claims 240, but doesn't say if that's measured at the flywheel or at the tires. Thundercharger folks were, for a while, claiming 280 horsepower on their supercharged abomination -- no word on if that's flywheel or tire numbers either. And there have been a few stories of 300+ horsepower V6's rolling around South Africa, Australia and even in Korea.

The problem is, the Korean race market hasn't seen any of these wonderful setups. They have instead been watching the 2.7L DELTA rip apart at the seams: breaking crank caps, cracking sleeves, bending rods, breaking piston ring lands, and spinning main bearings.

Well, while doing a small bit of battle with some of the n00bs on NewTiburon, I dug up this picture here...
http://www.hmaservice.com/xml/graphics/ed/edja500a.jpg

This is an exploded diagram of the 2.7L V6 motor from the Tib and Santa Fe. Pay notice to the main caps (for those who aren't part literate, at the very bottom see the Bearing Cap (main cap), Bearing Cap Bridge (girdle) and the one line that says M10: 14-16 (140-160, 10-12) which is in reference to the main cap bolts.

What you have here is a fully girdled block with four bolt mains. (For the new people: notice, four bolts hold down each crank main cap, that's a four bolt main) This would usually indicate great strength; if you're talking about a Chevy 350 with four bolt mains, then you've got a very stout motor to build. But our 2.7L also has that full girdle setup (all mains are bridged) which provides even better lateral and anti-vibration support to the block.

Wow, so you'd think with all this cool stuff, the 2.7L should be pretty damned strong right? Well, is it strong, or was Hyundai suddenly making up for something they found after the original casting design?

Look at this diagram now:
http://www.hmaservice.com/xml/graphics/EC/ECBB001B.jpg

This is the same diagram, but for the 3.5L V6 out of the XG 350. Look again at the bottom end of the picture, and notice the differences... Instead of two seperate parts, the mains and girdle are one integrated unit... And look closer to find that the mains are only two-bolt design. Also check out the bolt specification: M10: 90-100 (900-1000, 65-72) Actually, they're missing the M10 notation, but those bolts ARE a metric 10mm.

Ok, so here's the deal:

The 3.5L V6 has more rotating mass, produces more horsepower, and yet only is needing 2 bolt mains and a smaller girdle. Also, take a look at the bolt specs I provided on the 2.7L:

M10: 14-16 (140-160, 10-12)

M10 is the bolt size, Metric 10mm.
14-16 is tightening torque in Newton Meters
140-160 is tightening torque in kg/cm
10-12 is tightening torque in lb/ft

Ok, now since most of us here are yanks wink look at the pound feet... Hyundai is wanting 10-12 pound feet of torque to completely tighten down the main caps on the DELTA. Compare that to the number on the 3.5L of 65-72 pound feet! For reference, the I4 BETA motor needs around 43-50 pound feet...

There has been speculation as to how exactly the main crank caps break on the DETLA: Do they indeed fracture and break apart like a piece of pottery? Or do they simply rip out of the block?

If you ask me, in light of the way Hyundai is treating the Delta, it looks like the tapped sections of the block that hold the main cap bolts is far too weak and the bolts are physically ripping themselves out of the block casting.

We do know, 100% for sure, that the bottom end of the DELTA has been shown in multiple cases to come apart in large expensive pieces when dealing with horsepower around 240+ to the tires, depending on a few circumstances. What we haven't been able to fully verify is HOW it comes apart...

But my guess, again just by looking at the Hyundai technical manuals, is that the block itself is weak. Not much you can do to strengthen this thing; even newly helicoiled threads in the block wouldn't hold the necessary torque.

Thought I'd share, since this has been the source of heated debate on nearly any site that deals with the new Tiburon. You can guess how much I'm loved over on NewTiburon forums :D

[ December 17, 2002, 02:19 PM: Message edited by: Red ]

Damn, you've been digging deep! :D

From what I know about the Key Motorsports Tiburons, we did not had any problems with the main caps themselves (I worked there).

Only problem I can remember was with the con-rods. They seem to be the first thing to go on these engines. Worst I saw was con-rods coming out of the block wall ... three times in one weekend! But it seemed there was a problem with the oil pressure (probably too high), washing the con-rods bearings...bad.

I can't really elaborate on the inners of the V6 because we dealt with an engine builder. The V6 used in Grand-Am cup have to be stock (blue-printed of course) and can have minor mechanical improvements made (such as headers).

As for the dyno run, if I remember correctly it was done on a Rolling Roads. I can't remember the numbers we got at the wheels, but once correction factor applied, it got to 240 bhp (yup, crank).

<div class='quotetop'>QUOTE </div><div class='quotemain'>Bjurr:
Damn, you've been digging deep! :D </div>naw, that is just another day at the office for Red. :D

http://forums.clubsi.com/images/icons/laugh1.gif

Sadly, you're not too far off...

Holy jinkies......

You would have to machine a new cap and cap bridge.

Give me a XG350 anyday. Get Alpine to pop a supercharger on that. wink

Thank you, Red, for putting those n00bs over at NT in their proverbial places. :D

I beleive there is a problem with bolts pulling out that hold the main caps for the 2.7, they use a low torque because they are threading directly into aluminum threads and due to the expansion of the aluminun as it heats up the bolts will actually get tighter. What they need to do is add a steel insert into the casting of the block so the threads will be steel, a steel heli-coil would not be good cause as the aluminum expands it will loosen up cause alu. expands more than steel. I seen a blown up one at the dealer and the guy showed me a main cap bolt and you could see where the threads were still on the bolt.

The BETA actually has steel inserts in the block for the bolts to screw into, but the block is cast iron...

I'm relatively convinced that you're on the right track -- the aluminum block is, one way or another, causing the threads to either expand physically and not hold tight enough, or is too soft in comparison to the steel bolts and the threads are just letting go.

Sucks to be a V6 owner and want uber-horsepower frown

Makes me think, if someone were to reverse engineer a Delta block and cast one out of iron, it would handle all kinds of power with the 4-bolt mains and girdle.

I know that the 300Z guys have similiar problems at high hp. What they do is after final engine assembly they WELD the bolts and main caps. The only problem is once it's together it is together forever. I believe SCC did this on their vg30 when they built theirs up. Maybe this would help? How about tapping further into the block and using longer bolts?

could you just use something like titanium bolts and using a higer torque to tighten them down? I mean if the bolts are shattering, just make sure they're super-high quality and are locked down enough. That would help right?