Thread: 1st bbc

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hi guys while my block is in the machine shop getting..dipped and sonic tested.i was tryn to figure out the best crank to put in..NOW when i took the motor apart(402ci) i discovered that it had 454 heads #336781 and 454 crank #353039..i dont know yet if it is bored or not..i am planning to make it a 427, it would seem that a lot of the componenets are there..for know i going to use the stock heads via new spring kit and if i can find a forged 4140 steel crank.. i have a couple of specs that ive come across..but dont know which one to go with for maximum hp. if u could point me in the right direction that would be awsum.

I'm not one of the chebby guys but they'll be along for sure.. I just wanted to take a moment and say hi and good to see you here.

what do you anticipate doing with this ride? Cruiser? Racer? Daily driver?

A 402 block (4.125" bore) coupled with a 454 crank (4.000" stroke) makes a 427 cubic inch motor. The original 427 used a 4.250" bore and 3.760" stroke. More than likely, you cannot bore the 402 block to 4.250" without hitting the water jackets, so be happy with the 427 you already have would be my best advice, assuming that the 454 crank and rods clear all the interior components in the 402 block.

On second thought, I'm thinkin' that the block is bored to 4.250" already. Otherwise, where would you get pistons for this combo????? Custom 4.125" pistons for a 4.000" arm would come pretty dear I would think.

KB make the piston for a 402 to 427/434 thats a 4.125 comes as std. 030.040.060.070.100 over bore 6.135 rod and a 454 crank 4.000 . part number kb361. they it this time do not make it in there forged Icon piston line. i told the KB rep a two years ago to get off there ass about making the 1.645 CH piston in the 4.125 to 4.185 bore for the 396/402. i did a kit for a guy using the KB 361 pistons 4.000/454 crank rebuild truck rods . as for boring a 402 to .125 over and using a 4.250 bore and a 3.760 crank that would be any crank two pc seal from a 366 to 427 .3.760 then using a 6.135 rod with a CH 1.765 piston for any 427 the older 1965 and 1967 blocks could go the 125. and more but very few the over bore before sonic checkers the trick was checking thru the center soft plug hole with a arc welding rod size ? not sure must been 1/8 or less i was told as a go no go to check how thick the walls were. but at the end of the day i see no value in trying to bore a 402 block out that far as any thing from the 1970s will not take the bore out. i would think .its just so easy to get a 454 block stock 4.250 bore and you can take the bore to 4.310 to 4.320 and not worry about busting thru a wall . put a 3.765 crank in the 454 block .... PRESTO... Now you have a 427 i done them this way but most guys want 489/496s so i use a 4.250 crank or move up to 4.375 for a 511cid in the 9.800 deck .i done them all and the ones i like ...i done many times

ok...im buildn it to b a street\strip car..I wanna acomplish at least 500 hp..mayb a lil nos..can the 454 crank that i have handle that hp?If so what would the max hp be on that crank? What type of cam would u recommend?

Originally Posted by 78 str8

ok...im buildn it to b a street\strip car..I wanna acomplish at least 500 hp..mayb a lil nos..can the 454 crank that i have handle that hp?If so what would the max hp be on that crank? What type of cam would u recommend?

stock Gm cast iron crank can hold 500 hp easy and used them over the years but there is better in cast steel or forged steel in the 4340 or 4130 like Scat cranks were they will hold up good . the price is in line with a build like this were you do not need a 1500. crank. your old crank will work if a good crank to start with

first off i wanna thank u 4 ur responces..yall r awsum! Ok thanx 4 crank advice..do u think the block could handle a .60 bore?now im going 2 use sum h beam rods with arp bolts..now on my heads im going to do them 2.19in intake 1.88in exhaust..does that sound bout rite? What would be a decent head gasket and cam?

Originally Posted by 78 str8

first off i wanna thank u 4 ur responces..yall r awsum! Ok thanx 4 crank advice..do u think the block could handle a .60 bore?now im going 2 use sum h beam rods with arp bolts..now on my heads im going to do them 2.19in intake 1.88in exhaust..does that sound bout rite? What would be a decent head gasket and cam?

If your gonna make the valves bigger just go up to 2.25 and don't even mess w/ the 2.19. You'll be a lot happier that way!

Originally Posted by 78 str8

first off i wanna thank u 4 ur responces..yall r awsum! Ok thanx 4 crank advice..do u think the block could handle a .60 bore?now im going 2 use sum h beam rods with arp bolts..now on my heads im going to do them 2.19in intake 1.88in exhaust..does that sound bout rite? What would be a decent head gasket and cam?

2.190 /1880 are fine for the small bore in a hi flow valve

Originally Posted by 78 str8

do u think the block could handle a .60 bore?

No, the block could not handle a .60 bore, because that's 600 thousandths of an inch or nearly 5/8 ths of an inch the way you have it written. Should have been written 0.060" (sixty thousandths of an inch). The zero on the left side of the decimal point tells you that you are dealing with less than a whole number. If you wrote it as .060", with no zero to the left of the decimal, then the reader could question whether or not you meant a fraction of an inch or whether you left off a whole number when you wrote it.
0.001" one thousandth of an inch.
0.0015" one and one half thousandths of an inch.
0.030" thirty thousandths of an inch.
0.060" sixty thousandths of an inch.
0.170" one hundred and seventy thousandths of an inch.
0.600" six hundred thousandths of an inch.
4.030" four inches and thirty thousandths of an inch.
You can't just decide to bore a block this size or that size without knowing how much meat there is in the cylinder walls. Specs will vary from builder to builder, but having a minimum 0.200" cylinder wall thickness on the major thrust face (the passenger side of the bore as viewed from the radiator) and 0.135" cylinder wall thickness on the minor thrust face (the driver's side of the bore as viewed from the radiator) after boring and honing would be acceptable to most builders I would think. Wall thickness is determined by "beeping" the walls with an ultrasonic instrument. Either rent a beeper and do it yourself or take the block to a shop that has a beeper and have them do it for you.

Originally Posted by 78 str8

What would be a decent head gasket and cam?

Ask Pat again. He's getting a little old and senile, so you have to keep after him.

Milk and cookies will now be served in the break room.
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Boy are we in great spirits today.

Originally Posted by NTFDAY

Boy are we in great spirits today.

The older I get, the more I tend to be direct and to the point. Like me or don't, I'll always tell you the truth.
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there is no head gasket that is made for the small bore any more .so most lower grade head gaskets will be better then 4.250 bore size in a rebuild kit . a fel pro 1037 can work 4.370 fire ring gasket will need the deck drilled for water or use the Rol hg31170hr and is a 4.345 fire ring .should need no added deck work. if you do not want to drill the lower water port hole in the deck of your block . how to do this is on a small sheet comes with the 1037 felpros head gasket.s this must be done with 1037 felpros. Cam????i only build bbc with roller cam,s hyd or solid NUMBERS lift dur lsa you need to tell me a lot more

ok thanks techinspector 4 gettn me on track with number and decimals..so lets try this again...I want to bore .060" to make my 402ci 4.125" go up to 4.185" that with the 454 crank and heads makes that a 440ci rite?

I just came upon a gen V 454..comes outta 98 truck.. complete minus carb for $500..should i get it? Or should i hang out for a gen lV? Plz respond as soon as u can..thanx alot!