Stroker 3500 possibilities...

[2.8-350TBI]

So, while thinking of the way I want to do my 3500 build, I have decided I am going to go with narrowed SBC rods. As we all know, the 3500 has the nice big 2.25" journals which need to be ground down for use with narrowed SBC rods.

If starting with 2.0" SJ SBC rods that leaves a .25" of room to play with, and with 2.1" SBC's that leaves us .15" to play with.

So lets say we used the SJ's and offset ground the crank to 2", would stroke increase by that 1/4"? or is my math wrong?

The way I see it, a 1/4" of metal would be removed, but the radius is moved outward only 1/8", meaning the crank would move the piston 1/8" above previous TDC and 1/8" below previous TDC for a total of a 1/4" more stroke.

With the 3500 crank being being 3.31, plus .25 stroke, turns into 3.56" stroke.
Add that to an otherwise stock 3500, and you get 3762 CC with 10.46 compression.

Does that seem correct?

[ericjon262]

seems correct, I like your thinking, now the only thing to worry about would be how much overlap the rod journals have, thats a key part of crank strength.

[ericjon262]

at that though, they make SBC rods that use honda bearings (tiny, 1.888")...

[ericjon262]

just did a little math, you could get a 3900 to almost 4.3L with an offset grind...

[2.8-350TBI]

seems correct, I like your thinking, now the only thing to worry about would be how much overlap the rod journals have, thats a key part of crank strength.

Theres still a decent sized plate between each journal, its not like were talking 4.3's here, with a seemingly paper thin plate between each journal.

I think a 1/4" of stroke is a good improvement, but what im left wondering is how much space do the pistons leave to move the pin up to accomodate longer rods.

And, I will try to source an LX9 with a forged crank to begin with. I am also planning to buy .030 over pistons from the store.

[ericjon262]

if you went the LZ9 route, I imagine LS1 stroker pistons may work, they both have a 3.9" bore.

[ericjon262]

my only other concern was rod to block clearance, but I imagine an offset grind wouldn't have too much of an effect on that, along with the fact that your using smaller big ends on the rods. what about cam to rod clearance though...

[2.8-350TBI]

It would have been cool, but theyre just too big. I may have to get custom pistons, which I dont mind, bcause I should be able to get them with SBC piston pins if the pin isnt moved too high.

As for rod to block or cam clearance, I havent heard of anyone ever having issues with that, and im confident everything will fit.

Can anyone get a picture of 3500 pistons?

[geoffinbc]

I would not ever worry about the cam. The 60 degree bank angle forces the cam way up in the block. There is even room for a cam tunnel floor and in the case of the 3X00 motors they stuffed an oil galley in there.

I would LOVE an increase in stroke on my old iron headed Trooper. I wouldn't even mind the engine being under square. That low end grunt would be magic off-road and cruising up hills at 2500RPM in 5th would be so sweet. My S-10 could use it too but I drive that thing completely differently and I think an aluminum headed turbo motor would be killer. Stroke length would not be my first concern in that motor.

[2.8-350TBI]

I would not ever worry about the cam. The 60 degree bank angle forces the cam way up in the block. There is even room for a cam tunnel floor and in the case of the 3X00 motors they stuffed an oil galley in there.

I would LOVE an increase in stroke on my old iron headed Trooper. I wouldn't even mind the engine being under square. That low end grunt would be magic off-road and cruising up hills at 2500RPM in 5th would be so sweet. My S-10 could use it too but I drive that thing completely differently and I think an aluminum headed turbo motor would be killer. Stroke length would not be my first concern in that motor.

That was my first thought about the cam too. I love how compact yet how great these engines are built

Im pretty sure anyone could get away with offset grinding a 3500 crank to stock journal sizes and cutting the tops of the pistons for a simple stroked high compression build.

Theres a pretty good machine shop in town that specializes in crankshafts, ill give them a call and ask for an estimate

[ericjon262]

I'm really considering a 4.3 LZ9 for my fiero right about now...

[2.8-350TBI]

I'm really considering a 4.3 LZ9 for my fiero right about now...

Its been done, I forgot the builders name, but he did an amazing job on it!

Theres a thread around here somewhere.

After playing with more math, I found out that if I want to keep at least a stock rod/stroke ratio of 1.72, I would have to go with 6.125" rods, I would have to get piston measurements to see if its even possible to do that. .425 longer rod and .25 longer stroke equals piston pin .450 further in than stock, so I doubt theres enough space...

EDIT: THIS POST HAS BAD MATH, see post below

[ericjon262]

anyone know the compression distance of a stock 3500 piston? how about a 3900 piston?

[ericjon262]

stock compression distance for a 3900 has to be somewhere around 1.25 inches, 1.263 with 0.00"of quench @ TDC

[ericjon262]

the squatiest Ls1 piston I could find was 1.050 compression distance. for a 6.125" rod with a .25" offset grind, you'd need a piston with a .913" compression distance def custom, and would need some kind of a ring support.