Looking for some advice on 400 pistons

[1967coronet]

This winter I am sending my 1976 400 block { standard bore } to the machine shop. I will have it checked out and see what kind of a over bore it will take to clean it up.

I have heard the stock 400 pistons are aprox .0100 below the deck and have aprox 7.1 compression.
I need some advice on what set of pistons to order to get the compression up to 9.5.1 at least.
I would just as soon do this with pistons and not cut/deck the block outside of just enough to clean it up.

I am going to use the stock 400 crank & rods I am not building a stroker
just a mild 350 to 375 hp 400
Thanks for any piston help/ advice.

 

[lewtot184]

KB240 will get you in the ball park.

 

[1967coronet]

Thanks lewtot184, I looked at that piston name and part # and it sounds like just what I am hunting.

The shop wants the pistons on hand before they bore it so I will order them through the machine shop even at 9.1 that will help a bunch.

 

[EV2 GTX]

Thanks lewtot184, I looked at that piston name and part # and it sounds like just what I am hunting.

The shop wants the pistons on hand before they bore it so I will order them through the machine shop even at 9.1 that will help a bunch.

Hey there 67 coronet....hope things are going along well with your build. Just curious, have you already had a rough clean-up bore done at this point? Just not sure how you or the machine shop will order the correct size pistons if you haven't established what it'll take to clean up the cylinders?

I'd hate to see you buy a set of .030 over and it turns out the cylinders clean up at .040 or higher, for example.:sFun_doh2:

 

[1967coronet]

Hi EV2 GTX , Thanks for asking but they are going to check the block out 1st to see how far they need to bore to clean it up. The block looks to be in nice shape , They just want the pistons on hand to finish fitting them to the block.

My original post didn't sound right after re reading it lol
Fingers out running my brain again, To many years in the spray booth.

 

[EV2 GTX]

Ok, just checkin' bud!

Sok, my fingers do the same sometimes....

Good luck with the build!

 

[rumblefish360]

Your 1st post read right to me with you even stating in the first paragraph that the machine shop is getting the engine to check out first.
I think some
People can't read or just like to hear themselfs talk.

 

[HT413]

Your 1st post read right to me with you even stating in the first paragraph that the machine shop is getting the engine to check out first.
I think some
People can't read or just like to hear themselfs talk.

Not sure there was a need for that, seems like he was just trying to help.

 

[383man]

This is the 400 we run in my sons Dart. We use KB pistons and with the block decked and the Eddy RPM heads cut it has about 10.6 comp. Its a stock stroke 383 steel crank and uses the MP .557 cam. Its actually 406 cubes as its .030 over. Its run 11.40's @ 117 in his 3550 lb Dart. Ron

 

[EV2 GTX]

Not sure there was a need for that, seems like he was just trying to help.

Thanks HT...

I was down at the machine shop the other day discussing my 440 build with them and they had commented that, more than once, people have brought pistons in too early in the process. Then it turns out they go home with them after they end up buying the right ones. It seems pretty simple for sure but I guess it does happen! Sometimes it's just a mistake in the communication.

I guess when I read the OP's post, it reminded me!

Rumble fishes' post is a perfect example of someone wanting to hear themselves talk!

 

[rumblefish360]

Not sure there was a need for that, seems like he was just trying to help.

Not sure about my quote but I'm sure about yours.

Rumble fishes' post is a perfect example of someone wanting to hear themselves talk!

Yours was great this time around until this post. If you actually took the time to read and understand what you read, you would not be posting useless info and taking a jab back.

Thanks to you both, the thread quality is falling.

Now you both just try and do you bet to help instead of just jabber on and on now.

 

[Cranky]

Thanks HT...

I was down at the machine shop the other day discussing my 440 build with them and they had commented that, more than once, people have brought pistons in too early in the process. Then it turns out they go home with them after they end up buying the right ones. It seems pretty simple for sure but I guess it does happen! Sometimes it's just a mistake in the communication.

I guess when I read the OP's post, it reminded me!

Rumble fishes' post is a perfect example of someone wanting to hear themselves talk!

Throwing fuel on a very small fire doesn't help matters any either.....just makes the flames get bigger. Just sayin.....

 

[wyrmrider]

This winter I am sending my 1976 400 block { standard bore } to the machine shop. I will have it checked out and see what kind of a over bore it will take to clean it up.

I have heard the stock 400 pistons are aprox .0100 below the deck and have aprox 7.1 compression.
I need some advice on what set of pistons to order to get the compression up to 9.5.1 at least.
I would just as soon do this with pistons and not cut/deck the block outside of just enough to clean it up.

I am going to use the stock 400 crank & rods I am not building a stroker
just a mild 350 to 375 hp 400
Thanks for any piston help/ advice.

before you pull the block down check your compression ht at all four corners and then calculate your new deck clearance
What heads
CC your heads as most are way off published numbers and without cc you cannot figure compression
if using open chamber iron heads run the KB pistons with the reverse deflectors (dome away from the plugs)- since you know your crank to deck dimension, stroke and rod length you can dial in your compression
I put my 2 cents worth in when these pistons were designed many years ago and they really work
If closed chamber heads figure out your quench and compression ratio
and get it all figured out before you bore
run a cam designed for MOPARS not Chevys
BTW why not throw 440 crank and rods in while you are at it
get internal balance and a 426
figure $$ both ways
lot more performance for just a few more dollars

 

[lewtot184]

unfortunately KB doesn't make a quench dome stock stroke 400 piston.

 

[1967coronet]

thanks for the info wyrmrider, The block is already apart, crank & rods all look very good on the bearing surfaces but I will get them all checked at the machine shop. I am going to reuse all the stock parts I can , I just wanted a bump in the compression but not to much so I can buy fuel anyplace and be ok. lol I have read about the stroker set ups but for what I am doing with the car I really don't need it. I do understand though its a very cost effective way to get some big HP. If I can pull 350 hp out of this 400 I will be happy. Thanks again for everyones input , That's what I was after, Lots of Good advice on here and a good bunch of folks.

 

[wyrmrider]

thanks for the info wyrmrider, The block is already apart, crank & rods all look very good on the bearing surfaces but I will get them all checked at the machine shop. I am going to reuse all the stock parts I can , I just wanted a bump in the compression but not to much so I can buy fuel anyplace and be ok. lol I have read about the stroker set ups but for what I am doing with the car I really don't need it. I do understand though its a very cost effective way to get some big HP. If I can pull 350 hp out of this 400 I will be happy. Thanks again for everyones input , That's what I was after, Lots of Good advice on here and a good bunch of folks.

so another reason to use an aftermarket head, 67 915 or earlier head
or
use the stroker
really hard to prevent detonation with flat top piston and open chamber head, tht's one of the reasons they kept dropping the compression and compression height

I knew kb did not have pistons for 383 as I had to buy them form Arias Venolia etc, had not checked on stock stroke 400's

Another method if you must use stock heads is to weld up the chambers- but I do not see that this is a matching number restore build
It's not big hp you are getting it's driveability, gas mileage.
lower compression 400s or any BBM do not like overlap and long slow cams
If you have stock cam now you know how soft it is
Magnum duration cams loose all the low end even with smaller HP converter
bigger than magnum cams require gears and converter
The only way to make em work is with race gas and more revs than you are going to want to do
so if open chamber heads and flat tops on pump gas keep the compression moderate and run a short tall cam- build a torker- the heads are not good for highHP anyway so do not give up low end to get top end that you can't get anyway- I do not see this as a high stall low gear build
correct me if I'm wrong
cheers

 

[1967coronet]

Your right on the money wyrmrider , my 67 coronet is driver until the snow starts, aprox 4,000 miles each year.

3:23 rear diff and a stock convertor 727,
mpg isn't a big deal with me, my 383 that's in the car now gets aprox 14/15 on the hyw , but the old gal is getting tired ,

I have this 400 and figured what the heck if I can bump the compression a little I will make a good engine to rebuild.
I have the correct convertor for the 400 and balancer.

Thanks again for the advice.