Ok I have a good 350. I know I am going to replace the pistons and rods for some better ones. My questions is should i have the blocked bored or just leave it staduard. And does borin it to .030 over really help it any. Thanks

 

boring doesnt really do anything power wise maybe give ya another 10hp or so. Its purpose is to true and clean up the cylinders. It takes the out-of-round and taper out of the cylinders. If your going through all the trouble of buying new rods and pistons u might as well bore it. I would have it aligned honed too. Align honing trues up all of the main caps and perfectly aligns them.

 

10hp if you have a few NOS stickers and bolt on wings maybe.
realistically, you are looking at under 5 hp difference.
you dont bore to get power or displacement, as was already said.
you re-bore the engine to clean it up.
generally speaking, anytime the engine needs a rebuild, its a good idea to overbore it.
sometimes you can get away with less than 0.030" over, but finding pistons in, say, 0.010" over may be more expensive than 0.030" over, so thats why typical increments are in 0.030"... its just cheaper

 

You don't think the 12 cubic inches I added to my 400 will give more power, considering the displacement change and compression ?

-- Joe

 

anethesis - what happened to the 'vette?
Cool '79 Camaro though!!!

You are joking though right? I mean, you're looking at right on 3% increase in displacement. So if you were making 400HP, you'd be making right around 412HP or so. 3% is TEENY !

 

Actually besides displacement you also have slightly better compression and less valve shrouding, so maybe like 17 hp instead of 12, which is still only a few percent, but How many people here throw more money chasing less power- underdrive pulleys, some cam swaps, engine mounts, some intake swaps, higher ratio rockers, etc- all of them on their own are only worth a few percent but when you combine them something magical happens and you actually begin to maek decent power.

That being said most of the power increase you get will actaulyl come from truing the bores and having better ring seal- go for the overbore.

 

I hated it. No matter how much money I threw at it, It just didn't please me.

Thank you. Figured I'd make an f-body comeback.

Of course, but these boards have been so dead lately I thought I'd contribute at least something.

4.185" bore is pretty damn big though. I never had a 400 before so, I hope this thing pleases me. Shooting for over 500hp/500tq.

-- Joe

 

I don't modify stock motors so I don't usually get mixed up with a lot of that stuff. I usually buy rollers, and then plan out what engine is going into it. Do tons of simulations, take notes on other peoples results, etc. It's easier for me. (though, expensive).

There is something to be said about sidewall clearance. You hone a block a few times and you might as well overbore it. I had actually planned on doing a 406, but I got a deal on some eagle rods and forged reverse dome pistons, and a timing set and some head bolts for $350 to my door, where as the parts would have been $780 new. Since going .060 over doesn't cost any more than going .030 over, it was a no brainer really. I think we went like .004" on the final hone for sidewall clearance.

Although, I did end up doing more machine work to this 400 than I have EVER done to a 350. And I wasn't too impressed with how much folks are getting for Forged cranks these days.. wtf.

-- Joe

 

i know what you mean about the boards slowing down. its like people come on - ask a question - never look to see if they can solve someone elses problems and never post how they fixed it - if they did.
and search? why look for search when you can get someone to spoon feed you.
i did that when i first got here but learning about your car is fun.
i am about ready to rebuild my 305 - just cause i want to keep the same numbers as when new.
so if you are only going to bore it once - what kind of hp are you looking at if you a new cam, heads, tpi, - headers - the regular stuff.
eventually i wil go to a 350 - i may still do that, but even that will need work - it just wont be good enough.
as for the crank, i know it has to be balanced for the piston and rod weight - so what would you recommend?

 

You only bore to get the cylinder walls round again.

Boring factory blocks is always risky. You never know how thick the cylinder walls are. So you bore the block until the cylinders are back round again. The less you bore, the more rebuilds you can get out of the block (assuming it's a good block, sometimes there's sentimental value, etc) and my first 350 was a .060 over block. Lasted about a week before I developed a crack in the cylinder bore.

If you've got an aftermarket block that can handle a decent overbore, go for it, but for a factory block, there are much better, more responsible ways to get more power than boring. Stroke it, put a bigger cam in it, port the heads, put some nice backcut valves in it... anything. Boring a motor gets you so little in performance compared to the risks and reduced lifespan of the block (Assuming you go farther than necessary).

.030 over is usually safe. Beyond that you never know.

 

thanks for the info. message understood and will follow recommendation.
thanks
tony