High Mileage head swap?

[T-Punk]

Alright my roomates are telling me that swaping heads on a high mileage engine is a bad idea. They say it will retorque the bottom end and will basically kill my engine. I've never heard this before but the reasoning they gave me was pretty logical so i thought i would ask here. Is 100K to late to do heads?

[98 3.8]

If their reasoning is true, rebuilding a high mileage engine is a bad idea altogether... I would think that you'd be fine. Lower miles would be better, but I don't think you'd mess up the bottom end.

[rhouse21]

I've talked to a few folk who advised me that my piston rings may be wearing down by now, so my car might not be able to handle any more pressure in the cylinders, but this is the first time I've ever heard of someone potentially twisiting their engine block.

BTW, I think both are a crock. If the old-schoolers can rebuild a block thats been sitting in a corn field for 40 years, I think you can safely change your heads.

If you've been good about changing your oil and don't have any leaks in your major gaskets, your engine probably thinks its still new.

...as an after thought, I noticed that after I got above 100K miles a lot of random little things stated to break withough warning. Things like tensioner pullies, oil pressure senders, water pumps, heater cores, O2 sensors, gaskets, tie rod ends, drive shaft carrier bearings, etc. No, these don't have anything to do with heads, but consider this a general warning. Our cars were designed for a "lifetime" of a little over 100k miles. And while some components (like the engine block) are probably good forever, you'd be well advised to give the car a very thorough once over and keep a close eye on it, especially once you start with the serious power adders. I've found myself literally stranded in the desert a few times because I didn't pay attention to warning signs that one of these li'l buggers was about to let go and it was not fun.

Bottom line: If your car's important to you, treat her like a lady. Give her what she needs and listen to what she tells you, and she'll continue to give you a ton of fun for years to come. (This is also good advice about significant other.) :D

[Tru2Chevy]

A normal headswap won't damage your bottom end at all. Tell your friends they are full of crap :D

- Justin

[grayman]

ok, my 2 pennies,
first...putting fresh heads on a high mileage engine(does not have to be modified heads...any 're worked/overhauled heads) can restore compression to the piston cylinders. This can cause increased oil consumption due to piston ring blow by. true story, think about it.
BUT...if the heads NEED a valve job...just one burnt valve, etc...then you need to do a valve job, period. just think about what is worse...a much better engine that MIGHT burn a little more oil...or some clunky piece of gargabe that has 15 pounds of compression in cylinder number 5.

Second: I don't think your friends are saying that and entire engine should not be rebuilt...what they are saying is as relates to the raised compression in the cylinders due to a fresh set of heads that crank bearings have a different load on them. At 100,000 miles those bearings are very well broken in and some people think it is taboo to upset the power ballance. With that in mind then nobody should ever add HP building components to any high mileage engine. I have never broken an engine (older v8's) by installing electronic ignitions, dual exhaust, headers, 4bbl carbs or cams on high mileage engines. (but i have never owned a chevy until now either.... [img]tongue.gif[/img] ...mopars don't break)
Now, bare in mind that the 3800series II engine is award winning. it has cross bolted crank jurnals and for many years has been a standard for performance AND reliability. our crank just don't break like other engines can.

[T-Punk]

thanks, this is what i was thinking but i was doubting myself when two people are telling me the same thing.

[rhouse21]

Well said, grayman.

In regards to the blow by:
I bought my car with the intention of making it a high mileage car so I babied it, filling it with Mobil 1 at the first oil change and never looking back. Now, 8 years later, I find that the car consumes very little oil and numbers from my G-Tech confirm that it's still putting out roughly as much as a new stock engine. But I realize that not everyone starts out with the intention of putting 500,000 miles on their engine.

If you're gonna do the heads, you may want to take the time to do a compression check to make sure that your piston rings are still in good order. I'd also switch to a good quality synthetic oil and run at least 10w30. (I've been told that the thinner stuff has an easier time blowing past worn rings.) Mobil 1 even has a new synthetic specificly designed for worn, high mileage engines.
http://www.mobil1.com/USA-English/Mo...h_Mileage.aspx

Oh, and if the heads are going to be off anyway, you might as well take grayman's suggestion and work over the valve train while you're at it.

[T-Punk]

Yeah i plan on doing it all at once. Also i have never used anything but mobil one and i dont burn any oil for sure. Not sure about my compression being perfect but the car runs great. Its still at 75k but by the time i get all the stuff for the head swap it will be at 100k. thanks for the help again.

[Fbody3400]

Originally posted by grayman:
mopars don't break

[img]graemlins/rofl.gif[/img] [img]graemlins/rofl.gif[/img] [img]graemlins/rofl.gif[/img] [img]graemlins/rofl.gif[/img]

[grayman]

[img]graemlins/banana.gif[/img]