this isnt anything im doing anytime soon.. possibly ever. but im curious.

a friend of mine is rebuilding his shortblock to stock specs.. well we were looking around at strokers,and i know most guys go with the 4" stroke.

looking around, i find very few people going with the 4.125" stroke.

what pitfalls or problems are there with assembling the 4.125" stroke that shys most people away?
i dont want to talk about piston speed, bore/stroke combos... lets just pretend that we've decided on this stroke.

what are the problems with it?




the one ive heard mentioned ONCE, is that the ring pack is moved upward and closer together on the piston to keep it in the bore... if thats true, how does it effect a nitrous or boosted car? i would think poweradder cars would not be very happy having the rings even farther up and crunched together.

what about rod to cam clearance? i know it'll be tight but are there special rods? can someone tell me "brand XYZ is too close, or hits, but brand ABC clears"
i assume the windage tray can be shimmed up to clear, no problem, right?

anything else like that? i know some of you have built 4.125" strokers...

 

a while ago ppl with 4.125 strokes were burning more oil than others. There is more piston side loading than the 4.000 - whether or not ppls engines have blown due to this, I have never heard conclusive evidence. If it were me, I would stay with the 4.000

 

Ideally you want to keep the motor as close to square as possible. A 4.0" stroke is very close to the 3.9" bore.

 

The 415 LS2 combo I am building next will have a 4.125 stroke. I think for it to be effective more attention to detail has to be placed on piston design, skirt to wall clearance, cylinder barrel length of block you are using etc. I dont feel the ring pack presents any problem at all (1.050 compression height)....I have built MANY a hard running 23' engine with 1.000" compression heights and 4" strokes due to the fact the deck height on the 23' stuff is alot lower (Only 9" total in a standard 23' block). I know the 4.125 stuff seems to have a bad rap, but I feel I can make more TQ and a little more power with a well designed 415 combo than a similar combination with only 402 inches of displacement....the cranks cost exactly the same. The extra stroke and displacement will certainly improve the low speed TQ and HP numbers which will enhance drivability so even if the HP is similar (and happen a little sooner) I still felt this was a good move for a car that wants to also place an emphasis on streetability, not just peak #'s. I still feel in a street/strip application that building the largest motor you can afford will always provide the best all around results, especially in a well thought out and executed build.

As I have yet to start building it, I dont have any advice on pitfalls to avoid but will keep you guys posted in regards to that. Unfortunately, the estimated time of completion with the time I have available to work on it is probably still 4-6 months away (being realistic)....at least it's just in time for the good air to start rolling in

 

thanks tony, im looking forward to hearing about the build...

i agree with you totally.. all this talk about piston speed, square motors, ect are nice... in a ideal world... but realistically, im not going to spin my street/strip motor past 7k... its not getting a huge cam.. and if its built properly, im not going to have any issues by "stroking it too much"... i have yet to see a build of this level lose power by adding displacement (when you can supply the air thru the topend)

like you said, the crank cost is the same... im sure the pistons will cost more... i donno about the rods yet... clearances, or any of the details.. and we all know thats where the devil is. lol.


anyone else build one?

 

ttt...

noone else building very large stroke motors?

 

Tony, are you going to use the LS7 Ti rods and the new small pin pistons like the JE LS1 FSR? I think the length of the LS7 rods works with the standard 1.115" pistons and the 9.24" deck height.