changing ci's. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

truckerboy · 07-03-2010, 04:42 AM

I have a 400 SBC block. I want to make it 409 ci.. IS it possible, and if so how much over do i need to bore/stroke it?

thanks yall

**bigsnookmaster** · 07-03-2010, 08:12 AM

A 400 .030 over is 406, .040 over is a 408. If you take a 400 .030 over with a 3.875 stroke, you have a 420, with a 4.00 stroke you have a 427. I believe that's it, if I'm wrong, feel free to correct me.

prostreetC-10 · 07-03-2010, 09:16 AM

It's kind of an odd question. Just why do you want to make it a 409? You're not thinking of the 348/409 chevy "W" series BBC motors are you?

Usually, when you hear of someone running a motor that has a really odd displacement, it's because of the amount of overbore they had to go to remove scratches in the cylinder walls or to true up the overall shape of the cylinder. As bigsnook said, you will usually see .030, .040, 060 and so on. You will bore the cylinders to the size and type of aftermarket pistons you can get. You wouldn't bore a motor to a .038 if you can get pistons to match. Some guys will also bore and stroke to match a rotating kit or to achieve a maximum displacement within a certain block casting for racing or some other reason.

So just why to you want this 409?

cableguy0 · 07-03-2010, 10:51 AM

Unless the engine is worn out and needs rebuilt. Its a complete waste of money to change anything to get 9 cubic inches. There wouldnt be any stroke involved it would be done with bore alone for only 9 inches. Your not going to see any power gains or benefits by doing it.

Tom · 07-03-2010, 11:26 AM

Gotta agree with everyone else. Overboring a block will not net anything power wise on a 4"+ bore small block chevy.

chris mc bride · 07-03-2010, 01:43 PM

Have to agree also.Especaily with 400 blocks ,the less you can bore them the better.If you want to make more power buy you a eagle or equal crank with more stroke,throw in some longer rods and good pistons.Theres only one substitue for cubic inches and thats forced induction,better yet both are great together.

truckerboy · 07-05-2010, 02:33 PM

I dont want to bore it out to 409 for power. And yes i was thinking of the w series (348/409).
The main reason i want that specific ci is just to say it is there.

Also, the motor is already tore apart, so if i have to rebore, why not go ahead with it??

cableguy0 · 07-05-2010, 02:39 PM

Most 400 blocks have problems once they are bored. Some blocks have issues even at a .030 overbore. The smaller the bore the better off you are. Have the block checked for thickness as well while its at the machine shop. The 409 has absolutely nothing in common with the 400sbc. They arent even remotely similar.

truckerboy · 07-05-2010, 02:42 PM

ok, would the w series bolt to the 400's transmission?

**regan wilson** · 07-07-2010, 05:39 PM

Quote:

Originally Posted by truckerboy

ok, would the w series bolt to the 400's transmission?

409's are cool but you could build a more dependable and more powerful smallblock . The w block stuff is for collectors (hence that stuff is expensive)

BigDan3131 · 07-05-2010, 10:23 PM

If not directly probably with an adapter from Transdapt.

68GMCCustom · 07-07-2010, 06:03 PM

call it what you like....you can't tell how many c.i. a motor has by just looking at it.
GM bored out a 396 and made a 402....that was called a "396"... and also known as a big block 400.

truckerboy · 07-08-2010, 10:38 AM

I dont want it for the collecters series. (the w block that is). I want it to be 409 CI, and i dont care if it is a stroked/bored SBC or any other way to get that measurement.

http://www.youtube.com/watch?v=xKKP_cZuk54

Thats got something to do with it. And a 74 GMC

07-03-2010, 04:42 AM	#1
truckerboy Registered User Join Date: Mar 2010 Location: madison,nc Posts: 67	changing ci's. I have a 400 SBC block. I want to make it 409 ci.. IS it possible, and if so how much over do i need to bore/stroke it? thanks yall __________________ 79 K20,400 SBC, TBI, 4 speed w/ super low, 4.88's. 89 K2500. 350 TBI, mild cam, longtube hooker headers, glasspack true duals, TH700R4 with shift kit, Corp. 14 10.25'' full float, with 4.11:1 gears, standard ifs cranked to 2 inch lift. RS5000 shocks. 96 f350, Powerstroke, ZF6, DRW, 4x4. .Real trucks have 3 peddles. Real drivers float gears!!

07-03-2010, 08:12 AM	#2
bigsnookmaster Senior Member Join Date: Jan 2008 Location: St.Petersburg,Fl Posts: 1,270	Re: changing ci's. A 400 .030 over is 406, .040 over is a 408. If you take a 400 .030 over with a 3.875 stroke, you have a 420, with a 4.00 stroke you have a 427. I believe that's it, if I'm wrong, feel free to correct me. __________________ greg http://community.webshots.com/user/68406Stepside

07-03-2010, 09:16 AM	#3
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: changing ci's. It's kind of an odd question. Just why do you want to make it a 409? You're not thinking of the 348/409 chevy "W" series BBC motors are you? Usually, when you hear of someone running a motor that has a really odd displacement, it's because of the amount of overbore they had to go to remove scratches in the cylinder walls or to true up the overall shape of the cylinder. As bigsnook said, you will usually see .030, .040, 060 and so on. You will bore the cylinders to the size and type of aftermarket pistons you can get. You wouldn't bore a motor to a .038 if you can get pistons to match. Some guys will also bore and stroke to match a rotating kit or to achieve a maximum displacement within a certain block casting for racing or some other reason. So just why to you want this 409? __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video! Last edited by prostreetC-10; 07-03-2010 at 09:17 AM.

07-03-2010, 10:51 AM	#4
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: changing ci's. Unless the engine is worn out and needs rebuilt. Its a complete waste of money to change anything to get 9 cubic inches. There wouldnt be any stroke involved it would be done with bore alone for only 9 inches. Your not going to see any power gains or benefits by doing it. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

07-03-2010, 11:26 AM	#5
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,750	Re: changing ci's. Gotta agree with everyone else. Overboring a block will not net anything power wise on a 4"+ bore small block chevy. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

07-03-2010, 01:43 PM	#6
chris mc bride Registered User Join Date: Aug 2008 Location: greensboro nc Posts: 686	Re: changing ci's. Have to agree also.Especaily with 400 blocks ,the less you can bore them the better.If you want to make more power buy you a eagle or equal crank with more stroke,throw in some longer rods and good pistons.Theres only one substitue for cubic inches and thats forced induction,better yet both are great together.

07-05-2010, 02:33 PM	#7
truckerboy Registered User Join Date: Mar 2010 Location: madison,nc Posts: 67	Re: changing ci's. I dont want to bore it out to 409 for power. And yes i was thinking of the w series (348/409). The main reason i want that specific ci is just to say it is there. Also, the motor is already tore apart, so if i have to rebore, why not go ahead with it?? __________________ 79 K20,400 SBC, TBI, 4 speed w/ super low, 4.88's. 89 K2500. 350 TBI, mild cam, longtube hooker headers, glasspack true duals, TH700R4 with shift kit, Corp. 14 10.25'' full float, with 4.11:1 gears, standard ifs cranked to 2 inch lift. RS5000 shocks. 96 f350, Powerstroke, ZF6, DRW, 4x4. .Real trucks have 3 peddles. Real drivers float gears!!

07-05-2010, 02:39 PM	#8
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: changing ci's. Most 400 blocks have problems once they are bored. Some blocks have issues even at a .030 overbore. The smaller the bore the better off you are. Have the block checked for thickness as well while its at the machine shop. The 409 has absolutely nothing in common with the 400sbc. They arent even remotely similar. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

07-05-2010, 02:42 PM	#9
truckerboy Registered User Join Date: Mar 2010 Location: madison,nc Posts: 67	Re: changing ci's. ok, would the w series bolt to the 400's transmission? __________________ 79 K20,400 SBC, TBI, 4 speed w/ super low, 4.88's. 89 K2500. 350 TBI, mild cam, longtube hooker headers, glasspack true duals, TH700R4 with shift kit, Corp. 14 10.25'' full float, with 4.11:1 gears, standard ifs cranked to 2 inch lift. RS5000 shocks. 96 f350, Powerstroke, ZF6, DRW, 4x4. .Real trucks have 3 peddles. Real drivers float gears!!

07-05-2010, 10:23 PM	#11
BigDan3131 Registered User Join Date: Jun 2006 Location: Maple Valley, WA Posts: 1,913	Re: changing ci's. If not directly probably with an adapter from Transdapt.

07-07-2010, 06:03 PM	#12
68GMCCustom Truck and auto performance nut Join Date: Feb 2007 Location: McKinney,Texas Posts: 3,848	Re: changing ci's. call it what you like....you can't tell how many c.i. a motor has by just looking at it. GM bored out a 396 and made a 402....that was called a "396"... and also known as a big block 400. __________________ Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken

07-08-2010, 10:38 AM	#13
truckerboy Registered User Join Date: Mar 2010 Location: madison,nc Posts: 67	Re: changing ci's. I dont want it for the collecters series. (the w block that is). I want it to be 409 CI, and i dont care if it is a stroked/bored SBC or any other way to get that measurement. http://www.youtube.com/watch?v=xKKP_cZuk54 Thats got something to do with it. And a 74 GMC __________________ 79 K20,400 SBC, TBI, 4 speed w/ super low, 4.88's. 89 K2500. 350 TBI, mild cam, longtube hooker headers, glasspack true duals, TH700R4 with shift kit, Corp. 14 10.25'' full float, with 4.11:1 gears, standard ifs cranked to 2 inch lift. RS5000 shocks. 96 f350, Powerstroke, ZF6, DRW, 4x4. .Real trucks have 3 peddles. Real drivers float gears!!



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