The car is currently a head and cam 355 lt1. The previous owner used a new stock crank and forged rods and pistons.

I want to strengthen the bottom end for a nice big shot of gas.

What all would I need to stengthen it? Is it just the crank that is weak? Also what would happen if I put in a 383 crank but left the rod length the same? (I am still learning about rod length/ bore and stroke, so help me if I sound dumb.)

I believe that stock rod length is 5 something and that 383s use 6 inch rods. If I used just the crank from a 383, wouldn't that just give me like a 37x something displacement?

Is there anything else to consider? I'm just mentally planning the next project .

 

Well, unless you're running 500+ RWHP, the stock crank, easily the weakness in this bottom end setup, is fine. THe stock crank is just fine.

WIth forged rods and pistons, its ready for not only N20 but a Supercharger or Turbo application also. If the compression ratio is low enough.

Rod length doesn't affect anything, its actually the stroke of the CRANK that increases the cubic inches thus displacement of the engine. SInce I just mentioned that when determining C.I.D. you increase it by CRANK stroke and not the length of the rods, it'd still be a 383.

Something else to consider? you bet. BEARINGS. If you're going to actually tear the motor down, then replace the main, and rod bearings.

 

I never realized that, I thought it was rod length and the crank that determined the displacement.

How is a 37x engine achieved? What kind of crank?

I was planning on running a multi stage 200 or so shot. Since the car is already 375rwhp then I was thinking that 200 or 225 would be a bit much. Since a 383 crank and 355 would probably be the same price, I would probably go 383 just for a lil more HP.

What are good bearings? Is that what people mean when they say they are going to 4 bolt mains (bearings)?

Thanks,
Sean

 

About the stroke ordeal, I know it sounds confusing but my teacher just explained it like a week ago so its still fresh on my mind. He asked "Does increasing the Rod length increase displacement?" I said Yes. and he was like, no. While Stroke is the distance traveled from TDC to BDC, the bore, and stroke themselves don;t change. But if you were to get a crank with a longer stroke on it, the distance traveled by the rods would increase.

Anyway, not sure about a 37X engine, maybe they use a 327 with a different crank. Honestly don't know.

Its a good Idea to go with a forged crank 4340 for added protection, although 95% of the time, Cranks are the LAST thing to break when it comes to the bottom end.

Good bearings are CLEVITE bearings. They are tri-metal design and are the best.

4-bolt main is just a stronger block. I'm really vague on the specifics to be honest, I just know that its stronger than a 2-bolt main, but it has nothing to do with the bearings.

The "main" bearings I'm speaking of are the ones that go over the main caps on the engine.

 

The stock crank should do.

The pistons are stroke specific and the rods are piston specific. The pistons are designed for a specific stroke (typically 3.48", 3.75", or 3.85"). Typical rods (5.7" or 6") can be used with any stroke but must match what the pistons were designed for.

 

I guess, I'll just play with it as is and save to fix it later on.

Thanks, I learned something new too.

 

4 bolt it and stop wasting time unless you like rebuilding engines all the time. Milodon has them for $209 thru summit. You can do it yourself (watch out for the water jackets). Displacement is bore and stroke only. Rod is not part of the equation. Longer rod lenght gives you longer dwell time of the piston at top dead and a lot less side scuffing of the piston skirts. That's why I used 6" rods. Haven't done the calculation but 3.75 stroke with no overbore would problably give you something in the 37x CID range.