Stroker... or no?

[inline6]

So, I got my cylinder head back from the machine shop recently... New cam (kind of big). I put it on my F54 short block (which is stock) and I don't have enough piston to valve clearance. So, I had already planned to build a shortblock with forged pistons to work with the cam (rev limit of 7700 RPM). Lack of PTV and winter coming on makes the timing right to pull the bottom end apart and get forged pistons with the valve reliefs I need.

 

So, I've been reading about strokers in the archives... Given that my cam is good for 7700 and the car is almost entirely for track use, what combination makes the most sense for the bottom end? A 3.1 stroker, or something else? I note with some interest, the following:

 

The stock L24 bore and stroke is 83 x 73.7. Dividing bore by stroke, I get 1.126. The stock L28 motor, by contrast has an 86 bore and 79 stroke. Dividing bore by stroke, I get 1.089. It is mentioned in the archives, and of course it is fairly universaly understood that smaller displacement engines with smaller strokes tend to rev higher and typically make less torque over their given speed of operation.

 

Now back to the stroker. Most commonly, the bore and stroke is 89 and 83. Dividing bore by stroke, I get 1.072, which is close to the L28 number. Again, interestingly, taking the same 89mm bore and dividing it by the standard l28 stroke of 79, I get 1.127 -- basically the same as the L24.

 

So... would the characteristics of an 89mm L28 with the stock 79mm stroke be more similar to the L24, (i.e. be a more rev happy motor than the 3.1 LD28)?

 

To be honest, my main concern with going the standard 3.1 LD28 route with this motor is that the cam won't work well with it. I've seen some comments in the archives about it being pointless to rev the LD28 beyond 6500. Is that the case? And if so, what about the 89/79 combo I mention? Would that be a better route if I want to turn some more RPM's (7700 to be exact)?

 

Garrett

Edited November 14, 2010 by inline6

[JMortensen]

There is a tool that you can use to flycut the pistons you already have and then you don't need a new bottom end. It's like a really long valve with the cutter at the valve head. You just stick it in the head, put the head on the block and spin it with a drill motor (tape around the edge of the piston). You can refer back to the million other threads about strokers for more info there, but for my $.02, it's a good idea if you can get all the parts cheap. If you can't you might do better to put the extra money that you would have spent into the head.

[ktm]

There is a recent thread on Hybridz regarding installing a Volvo engine into his Z. The poster does exactly what Jon described (flycutting the pistons). He has photographs of the tool and the process.

Edited November 14, 2010 by ktm

[19762802+2]

There is a recent thread on Hybridz regarding installing a Volvo engine into his Z. The poster does exactly what Jon described (flycutting the pistons). He has photographs of the tool and the process.

 

I believe that would be Crazyoctopus, Here is a link to his blog which has the pictures ktm is talking about halfway down the page.

 

EDIT: forgot the link.

 

http://crazyoctopi.blogspot.com/

Edited November 14, 2010 by 19752802+2

[Tony D]

"I've seen some comments in the archives about it being pointless to rev the LD28 beyond 6500. Is that the case?"

 

It's the intrnet, people state a lot of ignorant and stupid shite, a lot of times they are talking out their arse. This is one of those instances...

 

The cam determines the behaviour of the engine far more than anything else.

 

Frankly, the rpms you propose are actually more street-cam than 'racing'... 7700 is just getting started.

Edited November 14, 2010 by Tony D

[inline6]

I found this thread in the other engines forum to be quite helpful:

http://forums.hybridz.org/index.php/topic/96128-borestroke-and-strokerod-ratios/