How do stock bottom ends stand double the cylinder pressure?
 

The way I understand things, the only way to get more power out of a given displacement is to increase cylinder pressure (or at least average cylinder pressure).

I also have heard that engineers build about 67% extra strength into the parts that the stock parts are expected to see.

So when I see Hondas, DSM's, Nissans, Supras, or Mustangs claiming 400-500 HP with stock bottom ends, I wonder how the rods , pistons etc. are able to withstand this for very long?

Anyone have any ideas?

Rev

It's not too awful hard if you pick the right combo. But they don't last too long like that..that's why you see guys going with forged cranks..and billet rods and such. ALot of guys will B.S. you in saying they have a "Stock" bottom end..just to make their self look good.

I understand when Carillo rods, forged pistons, and forged cranks and crank girdles are installed. So you think if they're really running those numbers that they may just be lying? Or is it just a suicidal engine?

Rev

Yea most of the time they are lying. Like i said they want people to believe them.

It can be done. A big part of it is maintenance, along with proper setup and tuning of the engine. I have seen a couple of Mustangs that run stock bottom 302's that run in the 9's. This is done with ported aftermarket heads, an aggresive cam, single plane intake + carburetor, and a rather large dose of nitrous oxide. Total flywheel horsepower is somewhere over 600.

When I say 'stock' shortblock, I mean factory block, crank, and connecting rods. The shortblock has been disassembled, balanced, blueprinted, deburred, and the block has been bored .030-.040" over, align-honed, etc., for very precise clearances. The pistons have been upgraded, along with better rings, bearings, and bolts/studs.

In addition, the engine is disassembled after 30-40 passes, and the entire shortblock is checked for wear, bearing and rings are replaced, tolerances are checked, etc.

It can be done, however, don't think you can assemble such an engine and just drive it on the street year after year.

Moxie, I'm a little surprised that the stock rods will hold up for 600 HP, even with the balancing, blue printing and good fasteners. But you did say that they got rebuilt every 30-40 passes. That's about every 15-20 miles, LOL. I hear what you're saying though.

Rev

Why would you say these people are lying and how does that make them look good by saying that? I personally run a stock block, stock ford forged pistons, a ford stock crank, stock ford rods, etc. I am on my second motor now. My first motor was exactly the same and lasted 3+ years. It made close to 575 at the flywheel. After 3 years of boost the stock block cracked, but the stock factory internals were fine. If the car is properly tuned and has a complete fuel system it will withstand that kind of power for some time. The weakest link is the stock block, and that can go at any time. The internals are actually very strong.

Just out of curiosity, how many head gaskets did you go through?

I agree that the block itself is the wekest link, but not just because it's fragile. Ford didn't do a very good job with the design as far as securing the heads to the block. There simply are not enough bolts. Cutting a groove, and using ringed head gaskets helps, but even that isn't fool-proof. Still, the bottom end can withstand a lot more than many people think, when the combination of parts compliment each other.

:)

Take care,
~Chris

One thing I forgot to mention is balancing. This is VERY important too. If the internals are balanced properly then they will last. I run a good balancer and all the internals are blueprinted/balanced.

As far as headgaskets go, I went through about 4 sets (all loc wire) before I installed a full fuel system and the proper size injectors. I have not blown on pair (knock on wood) since installing this system and switching to normal non lockwired heads.

I always thought a 'stock' bottom end meant they never even took the darn thing apart. If you want to tear it down and clean it up, its all still OE stuff, but not stock. That's like having an L88 vette with no overspray and calling the paint job original. Factory correct, maybe. Stock, no.

Am I coming out of left field on this one, or what?

IMO, a stock bottom end is one with entirely stock parts. If they have been modified, then it's a stock bottom end with minor modifications. Usually, people are referring to the source of the parts when they call it stock. Anything aftermarket makes it no longer stock.

An engine that has never been taken apart is "original", or "untouched", as well as stock, but a stock bottom end doesn't mean it's original or untouched.

:)

Take care,
~Chris

Thanks for the clarification. I get confused on how what words mean to people I think Norm McDonald said it best when he said, " I don't know a lot of words"

Hey, these are just my interpretations, what do I know? Everyone has their own, I'm just sharing mine.

:)

Norm is cool.

Take care,
~Chris