what bore/ stroke do i need to make a 427 out of a 400? Are there stroker kits out there for this?

thanks for any info..

Sorry ,i dont know much about what will work together but i put in a few numbers in a displacement calculator and got this.

60 overbore 400 block,was 4.125 went to 4.185

3.875 crank, from a 383 stroker kit ,i think.

Gave me 426.4 cubic inch

OR, 4.125 stock stroke and a 4" crank for 427.6 CI,probly gonna have to bore,so CI is around

eww.. i dont like the sound of a 60 over 400..

4.125 + .030 = 4.155 X 4" = 433.9 CI


Will this work? .020 OB to 4.155 bore,and 3.875 crank offset ground .060 to get 426.9 CI

Nevermind,i think you'll need an aftermarker block for that stroke or custom pistons.

Oh well.

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi/topic/9/15093.html?

420 cubes is something like .03 over and 3.85 crank. Not sure tho. Give DZAUTO a shout, he loves 400 block combos.

you can do a .030 overbore with a 3.875 stroke to make a 421. eagle sells kits and www.cnc-motorsports.com (http://www.cnc-motorsports.com) does to. you can use the stock block but a 4" stroke might not fit. I`ve heard it will and heard it won`t. never built one that big so i don`t know for sure.

I think it's usually achieved by putting in a 4" stroke crankshaft but thereare quite a few other problems with this combo from what i hear. (4.125" x 4" = 427.6 cubic inches).

4.125" bore x 4" stroke = 427"
4.155" bore x 4" stroke = 434"

These can be done with a factory 400 block but is a real pain -- lots of special parts and compromises. Its much easier to go with an aftermarket tall deck block.

4.155" bore x 3.875" stroke = 420"

That is the biggest I would personally take a factory 400 block. You would need a small base circle cam and a fair amount of grinding on the oil pan rails. It would also be a good idea to do a short fill on the block to help stabilize things.

hmm.. so this looks to be more of a project than im ready for.. i was just looking for an alternative from the run of the mill 406 ya know..?

thanks for all the info :)

p.s. Harold you still causing trouble over at the TRP site?

if so.. keep up the good work.

4.165 (.040 over) X 3.85=419.63ci

Here's some pistons that'll work too.

Keith Black KB225 (5.7in rod)

SRP 140034 (5.7in rod)

Matt,
The 420 is a super easy displacement to do, with a very minimal ADDITIONAL expense, with OFF THE SHELF parts. This makes a REALLY good, strong street/performance engine. If you want to go to a hardcore, serious, NOS type race engine, then another approach would probably better. In the past 35yrs of building engines, I've probably built about 25 SB400s and one of them is a 420 that is in my jet boat which we have used to drill some serious holes in the lake. It's still running fine!
First, you need a reputable machine shop who is familiar with SB400s and has done several.
A 420SB is done by boring .030 (DO NOT HAVE THE BLOCK DECKS SURFACED UNLESS IT IS ABSOLUTELY NECESSARY---you need all the deck height you can get) and OFFSET grinding the rod journals down to the small journal size of early 327 rods. This will be no more expensive than having the mains of a 400 crank turned down to fit a 350 block to build a 383.
Next, you will need a good set of early, small journal 327 rods----------------NOT 283 RODS!!! Install premium new rod bolts, such as ARP Wavloc bolts, and then have the rods resized. Something I do myself, is polish the rod beams (lengthwise) and blast them, BEFORE installing new bolts. The bolt heads which face the cam will also need to be clearanced a little (in the same manner as when using 350 rods in a SB400).
Buy pistons for a SB400 that are for using the longer 350 (5.7) rods. The piston tops will need to be milled just a little because of the increase in stroke. I determined this amount by doing a trial assembly of each rod/piston assmebly, then marking with a magic marker. I had my machinist turn down an old SB wrist pin so that it was just barely a slip-fit in the rod. This allowed me to insall the crank into the block, assemble a rod/piston into each hole, then rotate the assembly (one rod/piston/cylinder at a time) and use a dial indicator to determine how much each piston comes up above the block deck. I wanted to maintain a .010 deck clearance (the piston top down in the hole .010). So, for example, if a piston came up ABOVE the deck .018, and I wanted a .010 deck clearance, then I had the machine shop machine .028 from the top of the piston. When I built this 420 engine, each piston needed to have between .025 and .028 milled from each piston to maintain a .010 deck clearance. Now, keep in mind, this was in a block which HAD NOT been surfaced. If you used a block which for example had been surfaced .005, then that amount would either need to be added to the amount removed from the piston, or, maybe change to a .005 deck clearance for your pistons.
As each rod/piston is test fitted for piston top clearance, at that time, rod nut clearance can be checked at the bottom of the block. I only had to do some VERY slight bottom clearancing for rod nuts with a die grinder at 3 locations.
All of the above CAN be done at home if you can do these things yourself. Otherwise, ANY experienced, knowledgeable machinist who has done several SB400s can do all of this for you. Since this will result in 420 cubic inches, you need GOOD BREATHING heads. NOTHING made by Chev will breathe as good as the aftermarket heads such as Dart or World. My preference is heads with 200-210cc ports and stepping up to 2.05/1.6 valves. If your budget won't allow aftermarket heads, then ANY 74-earlier SB head will be fine. DO NOT USE 75-later SB heads!!!! In 75, GM started cutting corners on the production SB head castings. They were thinner, lighter, got hotter and are MUCH MORE prone to cracking! I read about building a 420SB like this MANY yrs ago in HOTROD and always though I would someday try it. I wish I had done this with 2 of my other cars which just have the basic 406! smile.gif

Or to make life easy since you have to buy pistons anyway,,, use the SRP 140034 flat top which has a 1.384 c/h & puts you at 9.022 with a 3,875 which is a pretty standard deal or 9.009 with a 3.850 offset ground crank / 5.7 - 2" rod ;)
BTW, this piston also makes a really cool big bore 350 with a 6" rod & a 3.250 stroke

thanks for the great info guys.. what im looking for is a street strip engine that will run deep into the 11's and still be able to drive my car on a semi regular basis. most likely anything i build will stay n/a but if a small shot of juice will get into in the 10's.. i may be tempted to do it.. lol . sadly i am not much of a mechanic so most of the work would probably be left up to a machine shop.. which here in tulsa we have quite a few reputable places to try..

thanks again for the info guys..

Roadrage, you can get deep into the 11's with a carefully thought out fairly mild 406. I'm doing it with only a 383.

You don't need that many inches!!!

well a street driven 10 sec car would be nice also.. i know it can be done with less motor.. the 383 in my car could do it with a few changes
and a friend has a 68 camaro with a street 406 running 11.30's.. i think the main thing is to just want something a little different..