402

[bakerman]

How you all doing? been a while. my ques. is i've got a 402 in a 1972 suburban that came trough the yard. block # 3999290 not sure if its a 2 or a 4 bolt main haven't pulled the pan. or what heads yet. (but i soon will) is this a good block to start about a 600 hp motor? or should i just do a mild build for my truck? thanks in advance BAKER MAN aka Ty :cool:

[fourspeednup]

I've seen a couple 402 El Camino's. From what I've read, the 402 was a great truck motor (long stroke+small bore=much torque) but never gained much of a high performance following. Kinda seems ass backwards for a jet. That's just my $.02 now lets hear it from a guy who know's what he's talking about...:D

[Roostertail]

I have a 402 in my 18 foot Nordic Jet. It is bored .060 over. It has a tunnel ram and two 600 holleys. The compression is about 10.5 to 1. All roller cam and lifters. It pushes the boat across the water about 68 mph at 5200 Rpms. It has been very reliable.

[cyclone]

Originally posted by bakerman
How you all doing? been a while. my ques. is i've got a 402 in a 1972 suburban that came trough the yard. block # 3999290 not sure if its a 2 or a 4 bolt main haven't pulled the pan. or what heads yet. (but i soon will) is this a good block to start about a 600 hp motor? or should i just do a mild build for my truck? thanks in advance BAKER MAN aka Ty :cool:
I owned a flatbottom with a 402 chevy in it. The only thing that sticks out in my head as being weird with that motor is that the starter isn't your average BBC starter. I had a hell of a time finding one at my local parts store.

[Hustler]

I have one in my boat and have had very good luck with it, it's a very mild build and dynoed at 425hp. I think if you want to get that much power out of it your going to need some good heads and a fairly high compression.

[21rayson]

Originally posted by bakerman
How you all doing? been a while. my ques. is i've got a 402 in a 1972 suburban that came trough the yard. block # 3999290 not sure if its a 2 or a 4 bolt main haven't pulled the pan. or what heads yet. (but i soon will) is this a good block to start about a 600 hp motor? or should i just do a mild build for my truck? thanks in advance BAKER MAN aka Ty :cool: this is from mortec. and really all that motor is a .030 bored 396. 3999290....402.......70-72...2 or 4 bolt, Truck
3999290....402.......72......2 or 4 bolt, Passenger. here is the bore and stroke. 402 = 4.125" x 3.76"

[PE 316]

Originally posted by cyclone
I owned a flatbottom with a 402 chevy in it. The only thing that sticks out in my head as being weird with that motor is that the starter isn't your average BBC starter. I had a hell of a time finding one at my local parts store.
I've got a 402 in my flat...
It takes (took) your STANDARD (depending on # teeth on flywheel) "Big-Block" Chevrolet starter!!!
Mike

[Fiat48]

Either 168 tooth flywheel or 152 tooth. Different starter depending on flywheel. Standard GM.

[cyclone]

Originally posted by PE 316
I've got a 402 in my flat...
It takes (took) your STANDARD (depending on # teeth on flywheel) "Big-Block" Chevrolet starter!!!
Mike
that's news to me. then again, the people at autozone never seemed to be that bright either. lol:D

[Bense468]

It was hard to find plugs when we were at the river for that 402 flat mike.

[PE 316]

Originally posted by Bense468
It was hard to find plugs when we were at the river for that 402 flat mike.
I'm a "Parts Guy" for the last 20 years I've done G.M., Honda/Acura, Nissan/Infiniti, Toyota/Lexus, Mitsubishi, Hyundai and Suzuki so it may NOT be that difficult for me, but I use AC-Delco# R44TS Spark Plugs in mine. (My cylinder heads are POST 1970 "small", Taper-Seat heads)
R = Resistor
4 = 14mm Thread
4 = Heat Range
T = Taper Seat
S = Extended Tip
OR
N.G.K. spark plug# UR4
NOTE: You will need to know if your cylinder heads are pre-1970 "large", non-Taper-Seat heads OR post-1970 "small", Taper-Seat heads)
"SMALL" = 5/8" hex socket size
"LARGE" = 13/16" hex socket size

[Chris J]

A 402 is really just a 396 Bored .030" over. I've heard several stories as to why GM did this
1) Hard to sell a 396 Big Block when you can buy a 400 small block for less money and less weight.
2) They had a lot of out of tollerance 396 blocks laying around so they bored them .030 over and made 402 using already available pistons.
Anyone have more info?
ALL Gen IV are good solid blocks capable of 600+ hp. Notable diffencences:
2 or 4 bolt mains
Valve reliefes cut in the cylinders
bore size.
9.8 & 10.2 deck height.
Don't get too hung up on 4 bolt mains, I'd rather have a 4.25 bore. you can convert any BBC to 4 bolt mains. If your hoping to get 600+ HP You'll need some aftermarket parts. Might as well start big and go for a 496 or at least a 468 (.060" over 454).
Bore & stroke table
http://users.erols.com/srweiss/tablersn.htm

[bakerman]

so should i build this 402 for my truck or put alittle bit more in my gen 5 454 thats in my boat now? im just wondering if the block is worth boring out or stick with what i have?

[PE 316]

I couldn't convince my machinist to bore my 402 to 4.250" (427 bore size) apparantly the walls wound be too thin at that bore.
So, IF you want something larger than 415 ci (approx.) with a 4.000" strok crank, then get a "later" style block...