30 over for a 69 RR 383

[mpro69rr]

Hey Guys,

I'm having my bottom end done (I think), is it worth it to have it bored 30 over? Will it gain much more power or more torque? Thanks for your advice!

Oh, my intention is to get a 450hp motor that is streetable, but will lay the rubber down when I want to!

 

[steve340]

It would not be worth taking all that "life" out of it for what you may gain.
If it does not need boring I would leave it alone and put decent heads on it and gain a lot more.

 

[1967coronet440]

Yup of it doesn’t need it leave it alone imo, put money into heads intake and cam.

 

[Photon440]

Bore when necessary, but not otherwise. Yes, you will gain a couple of cubic inches, and may possibly unshroud the valves a fraction. But your cylinder walls will be a bit thinner and that tiny amount of extra flexing could lessen the ring seal enough to negate the gains.

That, and the block will be that much closer to the end of its life.

 

[mpro69rr]

Yup of it doesn’t need it leave it alone imo, put money into heads intake and cam.

Bore when necessary, but not otherwise. Yes, you will gain a couple of cubic inches, and may possibly unshroud the valves a fraction. But your cylinder walls will be a bit thinner and that tiny amount of extra flexing could lessen the ring seal enough to negate the gains.

That, and the block will be that much closer to the end of its life.

Well the majority have it, I won't do it unless it needs it. Thanks Guys!

 

[biomedtechguy]

Another idea if the cylinders need to be cleaned up and you want or need new pistons is to just go .10 over and that way you have room to go.
I went from .030 over (came that way) to .35 over on my wife's 421 when it needed a rebuild. Ordered dished forged aluminum pistons from Race Tech to drop the CR to 10:1 (worked iron heads).
That won't really increase power from a few cubic inches, but it could get you a better CR and a lighter, stronger piston.

 

[super-bee_ski]

Leave it alone...or as our esteemed forum member biomedtechguy states...
Here is the deal,
You throw money into it and guess what?
It still will not be fast enough for you later on.
Why?
Simply put, it can be a vicious cycle...
Be happy (VERY HAPPY) with your 1969 383 Roadrunner!
Its a great car as is...

 

[miller]

Mopar BBs are fairly stout motors to begin with. Like anything else, you can throw gobs of money into them, or do a simple overhaul...saving the parts. A 383 HP is a good motor, with good parts in them.
Your goal should be, for a solid bottom end, and it will give you what it's got, with the added parts.

 

[4mulas]

The cylinders will tell you if it needs it. Ie: ridge if there is any, squareness of the bores, etc....

Gaining 6 cubic inches won’t change anything you can notice in terms of power. If it needs a bore I think KB offers a selection of pistons in .020 over as well, this leaves enough meat in the bore to do it again should you HAVE to.

If the cylinders are square, and there’s no ridge to speak of, and the bore size is still 4.25”, a hone job and re-ring is a good way to go. I’m doing that very thing on a HP 383 20 over block I have. New cam, timing set, oil pump, gaskets, aluminum heads, intake and carb. The top end stuff will liven it up quite a bit. 450 horse power will be a little difficult on the 383 without spending some good money on tti’s, and some other more aggressive power mods and choices which may open up a whole new can of worms.

 

[miller]

Available size pistons will be one deciding point, adding in desired CR, and the like. Bore size AND shape tells you what needs to be done, at what size. A 383 is a 'B' motor, what's called a low block, opposed to an 'RB' motor, a raised block.
Either can put out good HP, by how it's built, and parts used.
My 440 bore measured +.008 average. No way it would clean up at +.010, so planned on +.020, next plus size.

Fair WARNING...seems many machine shops will always say it needs +.030! Even though that's a common 'go to + size'...I say bullsh*t.
A +.010 cut equals a 100,000 miles run on the motor, before it will need another overhaul.

Don't go into a machine shop, and say do as you will...say this is what I want, once it's down and checked.

One thing you should always change, from a stock BB Mopar, is the timing chain. Stock ones are junk...go to a good double-row roller timing chain, and never look back.

 

[mpro69rr]

Available size pistons will be one deciding point, adding in desired CR, and the like. Bore size AND shape tells you what needs to be done, at what size. A 383 is a 'B' motor, what's called a low block, opposed to an 'RB' motor, a raised block.
Either can put out good HP, by how it's built, and parts used.
My 440 bore measured +.008 average. No way it would clean up at +.010, so planned on +.020, next plus size.

Fair WARNING...seems many machine shops will always say it needs +.030! Even though that's a common 'go to + size'...I say bullsh*t.
A +.010 cut equals a 100,000 miles run on the motor, before it will need another overhaul.

Don't go into a machine shop, and say do as you will...say this is what I want, once it's down and checked.

One thing you should always change, from a stock BB Mopar, is the timing chain. Stock ones are junk...go to a good double-row roller timing chain, and never look back.

Thanks guys for all your help! It really clears up a lot!

 

[Cojohnso1]

Depending on what you mean by "Doing bottom end?" Stroking with a 440 3.75" crank will wake up the B-block. Especially on the lower end torque side. That would add about 42 ci (depending on bore) if you are replacing rods and pistons anyways? A stroker build is no sin to consider. Stroking to a 426 with modest cam and head combo? 450 HP easily. Closer to 500 HP.

Telling the story of your short deck 426 Wedge doesn't sound too shabby. You can get 450+ HP with todays hydrolic roller cam and head setup. Very streetable at 6500 red line. Plenty of head options and configurations to keep it pump gas.

In closing. You will pull on any stock 426 max wedge or hemi. Why? Because of the shorter deck of the b-block. Shorter piston profile. Shorter pushrods. Smaller 383/400 main bearings. All adding up to lighter rotating assembly and less bearing friction. I have a 400 stoker to 451 b-block. It's a big block that thinks it's a small block.

 

[mpro69rr]

Depending on what you mean by "Doing bottom end?" Stroking with a 440 3.75" crank will wake up the B-block. Especially on the lower end torque side. That would add about 42 ci (depending on bore) if you are replacing rods and pistons anyways? A stroker build is no sin to consider. Stroking to a 426 with modest cam and head combo? 450 HP easily. Closer to 500 HP.

Telling the story of your short deck 426 Wedge doesn't sound too shabby. You can get 450+ HP with todays hydrolic roller cam and head setup. Very streetable at 6500 red line. Plenty of head options and configurations to keep it pump gas.

No, I really don't want to stroke it. I'm going to use the same crank and rods depending if they check out.

 

[miller]

Fingers crossed, it didn't get hurt too bad.

When I had my 69 R and R, back in 69-70, I dropped a Mallory RevPol dual point in it, swapped carb to a 625 cfm Carter Competition Series, and Hooker headers. Simple bolt on stuff, and she kicked up the dance.