Blew my engine. Anyone here build a 3.8 or 4.0?

[The Radium King]

i think a 101 mm bore is the max (available to us common folk, anyway) so with a 3.2/3.4 bottom end the biggest you can go is 3.8. the m96 3.6 and the m97 3.6/3.8 got stroked, so they can go to 4.0 with a 101 mm bore. i don't think you can just drop the stroker crank in a 3.2/3.4 bottom end as the bearing races are different (possible, but lots of work?)? and, as stated, the longer stroke increases lateral load on cylinder walls = more scoring, which is the big failure mode on the m97 engines. fixed when Porsche went to a stronger liner with the dfi engnes. so, if you do go with a stroker crank, make sure you do the lne nikasil liner as well.

then there are the heads. there is some voodoo on the interchangeability of the various heads which jake has alluded to in the past, and perhaps if he reads this he'll add some content?

but by the time you've replaced the heads, paid $5k to bore the cylinders, and rebuilt the bottom end, i'd suggest you are well into the cost of a new engine (la dismantler has a 3.6 X51 Powerkit engine for $12k or something on ebay right now - X51 has hotter cams, better heads, dual oil pumps, improved oil baffle, etc.).

[jaykay]

Originally Posted by The Radium King

i think a 101 mm bore is the max (available to us common folk, anyway) so with a 3.2/3.4 bottom end the biggest you can go is 3.8. the m96 3.6 and the m97 3.6/3.8 got stroked, so they can go to 4.0 with a 101 mm bore. i don't think you can just drop the stroker crank in a 3.2/3.4 bottom end as the bearing races are different (possible, but lots of work?)? and, as stated, the longer stroke increases lateral load on cylinder walls = more scoring, which is the big failure mode on the m97 engines. fixed when Porsche went to a stronger liner with the dfi engnes. so, if you do go with a stroker crank, make sure you do the lne nikasil liner as well.

then there are the heads. there is some voodoo on the interchangeability of the various heads which jake has alluded to in the past, and perhaps if he reads this he'll add some content?

but by the time you've replaced the heads, paid $5k to bore the cylinders, and rebuilt the bottom end, i'd suggest you are well into the cost of a new engine (la dismantler has a 3.6 X51 Powerkit engine for $12k or something on ebay right now - X51 has hotter cams, better heads, dual oil pumps, improved oil baffle, etc.).

Yes X51 is another route to consider for.....not sure about all the interface issues and any weak points in that engine.....I think you have one TRK how do you like it?+

[Jake Raby]

The X51 shares the same bottom end and pistons as any other 3.6 engine. It has bigger ports, and larger cams, with a larger intake plenum.

I've never favored X51 engines, even to be built up into our platforms.

[Porsche9]

Originally Posted by Jake Raby

The X51 shares the same bottom end and pistons as any other 3.6 engine. It has bigger ports, and larger cams, with a larger intake plenum.

I've never favored X51 engines, even to be built up into our platforms.

Curious as to why? The changes seems to fall into typical mods a engine builder would use to get more power out of a engine. Does it change the who power is delivered that you do not favor?

[Jake Raby]

Originally Posted by Porsche9

Curious as to why? The changes seems to fall into typical mods a engine builder would use to get more power out of a engine. Does it change the who power is delivered that you do not favor?

Its where and how the power is made. The engines make all their power so high in the RPM range that the hydraulic valve train is the determining factor. The engines don't really start to pull until 6K RPM, and before that they often make less torque than a standard care engine.

The big ports and big cams, with the huge plenums make for an engine that has a narrow power band.

The same characteristics follow the engines, even when they are made larger.

[Porsche9]

Originally Posted by Jake Raby

Its where and how the power is made. The engines make all their power so high in the RPM range that the hydraulic valve train is the determining factor. The engines don't really start to pull until 6K RPM, and before that they often make less torque than a standard care engine.

The big ports and big cams, with the huge plenums make for an engine that has a narrow power band.

The same characteristics follow the engines, even when they are made larger.

For a street driven car this doesn't make sense. Neither does what Porsche charges for it.