adding new heads to old block will destroy bottom half is that true?

 

Just the physical act of mating one with the other? False.

As that question is wholly generic and not at all specific, I'm going to say that just by upgrading heads, no you won't frag the bottom end. Now if you do something stupid once the upgrade is done... that is an another matter entirely .

 

I don't know about ruining the bottom end but you're not going to get the ultimate performance out of them if the rest of the motor is getting tired

 

seems like the bottom is pretty strong maybe its best to redo bottom you know short cuts leave you cut short

 

If you are looking to upgrade the the top half and if you have the money and or ability, I would rebuid it all and start fresh. To me that seems better than spending that money and time on the heads and then not getting the performance out of them because the block is getting tired. Plus depending on what heads you put on it, you may have to change something in the block to get the performance out of the new heads.

 

Upgrading the top end is going to increase your power, hopefully. With HP comes cylinder pressure. More cylinder pressure equals more abuse to the bottom end.

 

I know what your saying, but as generic as the question is it gives a false presence since in actuality if he's using a factory wheezer short block and installs a race head it would probably make less pwr thus being easier on parts LOL!! Bolt a set of 23* big port raced heads on a stock factory block changing nothing else and you see what I'm getting at.

Other than that, a basic answer to your question
No

 

The typical "gotcha" is if the new heads allow more power in the higher RPM range. If they do, you will probably start zinging the motor up to higher RPMs than you did before (becuase you're a performance maniac- you probably wouldn't be on this board if you weren't). RPMs are what kill an old short block. Start spinning an old short block to 6000 when it spent it's entire life below 5000 before and something's likely to let go not far down the road.

 

 

It is myth.

New heads won't hurt the short block.

However, that's not what you're really asking; even though that's what you said.

About 99.99% of the time, the owner is putting new heads on, because he wants/expects more power. Furthermore, the owner typically intends to USE this new power more than before.

Invariably, this means excessively enthusiastic "road testing", showing off all this new-found power to friends, competing in organized events, experiencing this new power while driving on the street, and otherwise adding to the stress on the short block.

So, no, new heads won't hurt a short block; but the driver will hurt the short block more effectively with better heads than with inferior ones.

 

yea i want more power but not at the expense of my bottom half all i want to do is add bigger valves and heavy duty springs to the heads block is 350 tbi with holly carb may add a mild cam but everyone keeps saying your power comes from your cylinder heads so i said hmmmm let tinker with them a bit but if im robbing hp from my overall performance i would just leave well enough alone i was hoping to add a lil more horses is all

 

Wont quite work that easily!


If you threw big port heads on an old wheezer block its never going to run well or barely run at all in the lower RPM ranges. Then when the revs come up to the point that your actually using those big ports your going to blow apart that old bottom end!

 

If you have a lower milage engine then your not going to hurt it but if you have high miles on it then your engine is going to eventually force the pressure out of the bottom end instead of the top of it, usually higher milage engines have worn valve seals and such. not all but sometimes. just my .02 on it. I have bolted together many small blocks with 75k and not had a bit of problem though!

 

Not to start yet another debate on this topic LOL, but it is as easy as that. The stock cams have very low durations and valve timing events to make pwr below 5K. Now install a set of big port race heads on a factory nothing changed short block and you lost all your bottom end due to large runners, and by the time you get the rpm's spooled up to recognized the advanced runner set up's, your now easily outside the stock cams perameters for making power, so it's a lose lose situation and is why soo many guys get upset when they "just installed kick azz heads" and cant see/feel any improvement since they completely screw up the combination and have nothing working together.

Physically bolting them on will hurt nothing mechanically, but like Sofakingdom stated a person will drive more aggressivly showing off the new pwr or at least trying to see if it really feels any faster than before. So long as a person matches the heads,cam,convertor per application it will run great, but just expecting miracles throwing after market heads on a stock block is asking for alot since most folks think bigger is better and will opt for larger runners instead of sticking with a 170-180cc runner to compliment the rest of their stock set-up, you get guys installing 200+cc runners and those just are matched to baby duration stock cams/convertors/gearing so the performance will drop instead of increase.

I've seen first hand the results from a bud that unbolted a set of iron eagles and only change was going to aluminum darts of the same runner size-EVERYTHING else stayed the same. He went from running 10.30's to 10.60's just from the amount of heat being lost through the aluminums great heat disapating ablities.