402 Chevs

I didn't know that they had 2bbl 402s in 1970 (I've never seen a listing in any books for one either), but I have a couple of the 1969 2bbl 396 intakes.

 

The books I have say the 2bbl intake was 69 396 only, 265 horse. That's the only 2 bbl big block intake that I could find. I wonder if the intake on the 402 in the stationwagon had been swapped sometime in the past by an owner trying to improve (vainly) mileage? Or maybe it was an early production 70?

 

Well, that could very well be it was a few years, it might well have been a 69...I really can't remember what I did yesterday...If anyone has any old BBC cranks I could use a few more...Thanks, Also I have a 427 69 block that is unlike I've seen before it's casting is March of 1969 with the Connecting rod clearance cast in the lower cylinders for the 4 " arm, it's coded for a 69 Corvette with 2 bolt mains. I had no idea they were preparing for the 454 so early in the 1969 season, can anyone add to my confussion?...thanks!

 

a 402 is a 30 over 396. these motors came in impalas...and they were sometimes referred to as 400's. (not to be mistaken with the small block 400 that also cam in some impalas) the impalas that had the 402's in them, had "400" fender badges. 402's are great motors....they can handle decent rpms, and they can make a ton of torque.

 

What nobody has mentioned is the inherent problems that the 2 bolt main 325 hp 396 had. They didn't like to be revved very high for very long before they would spin a bearing. That had something to do with the oil passages near the rear of the block. I don't really remember which journal was being partially block to getting enough oil but there was part of the casting that was built wrong. The 4 bolt motors did not have the same problem. Just something to be aware of

 

I had a 65' Malibu SS with a 2 bolt main 396 and 4 spd. The motor was laying in an empty lot. It was frozen so I beat the pistons out with a mini sledge and chisel. Micro polished the cast crank, honed the cylinders, re-ringed the cast pistons and re-bearinged the motor. Add 1 Sig Erson Hi-Flo 1 cam, slap on the oval port heads, added a rectangular port factory aluminum hi-rise with an 800 Holley.
First race was against a 75' Nova with an LS7. Gave up 8 car lengths and won. Next race was against a 69' Vette with a 435hp 427. Gave up 3 car lengths and won. I spent 2 years beating the crap outta that motor with 4:88 gears and slicks. Finally spun a bearing. No one believed it was a lo-po 396 until I tore the motor down. You could still see the chisel marks on the pistons.
Put a forged crank in that motor but it never ran the same,,,go figure

 

As Unclee stated if you ordered your car or truck with a 400 you would have needed to request 2bbl or 4 bbl carb the 2bbl you would have a small block chev, if you ordered a 4bbl you then would have gotten the 402 big block chev. I had a 1972 caprice that had 400 badges on the fenders but a 402 under the hood from the factory. Just put an rv cam and intake/carb of choice its a great engine.

 

Wow guys thanks heaps, not only have you helped me make a decision but as usual I have learnt a truck load. Motor will go in a little A roadster or a Fiat Toppo if I can find one so should be fun.

 

i'd have to disagree with you on the fact that they don't like rpms.
i had a 69 396, bored to a 402, 2 bolt main, stock steel crank, stock rods, aftermarket forged pistons, a 0.600 lift cam, 292 duration, solid lifters, edelbrock torker intake, 850 double pumper, mallory distributor, stock chevy rectangle port heads (not ported or polished with1.19- 2.88 valves) hooker competition headers, 7/16 push rods, roller rockers, a t.h. 400, manual valve body with a 3500 stall and a 200 h.p. shot of nitrous. that motor regularly saw 7200 rpm shifts without any problems. i ran it that hard for 2 years. i drag raced it, street raced it, and it was my every day driver until i sold the car. that car was again run that hard for another 3-4 years by the guy that i sold it to, again with no problems. he went through that motor due to a blown head gasket. all the bearings showed normal wear after all that time. the thing ran like a scalded dog...and no one beleived it was "only" a 396. it was in a 70 nova, with a stock 3:08 10 bolt (non posi) rearend...and the car ran consistent 11.90's in the 1/4 with cheater slicks, and full exhaust.
big blocks can handle rpms...if the bottom end is built right.

 

Apparently the heads have "Hi Perf-Pass" cast into them. Does that mean anything to anyone out there in HAMB land?

 

might be rectangular port, neat. how about some casting numbers? also see if there are any numbers stamped on the block deck, in front of the (aussie) driver side head.

 

If it has HI-PERF cast on top of the head, under the valve cover, it should be the high-performance rectangular port heads with 2.19 intake valves (compared to the 2.06 on the regular oval port heads). If you've got some casting numbers, I'll look them up for you.

 

Sorry guys its been so long but just got the numbers - block casting no. is 3955272, heads are 3872702. If someone can decode them for me I would appreciate it.

 

Per Mortec.com:

3955272='69 396, either 2 or 4 bolt main; 3872702='65-'66 oval port closed chamber for a 396 or 427, 98 cc chamber.

 

Back in the day I bought a 70 Chevelle 402 L-78, 375 horse with headers and dual exhaust, it was fast real fast. Used to eat 6.6 Firebirds for breakfast. I blew this motor up and my cousin and I put an L-88 427 in it the power felt very similar. The 427 was a little faster in the old SS, my point is in something light like a rod it should fly and make a good motor for any old car as well. Rags

 

My reference book says '69 396/402, all 2 and 4 bolt mains. Since the 402 was introduced (silently) during the '69 production run, it is likely a late '69 block.

The closed chamber heads are very good for a street motor.

Do you have the engine number from the deck pad on the driver's side (passenger side in U.S.)?

 

I was told it appears motor number was removed when the block was last decked. Does that sound correct?

 

yeah, the deck surfaces on old big blocks were pretty crappy and it's common for the numbers to get machined off.

there should be a casting date code on the block and on the heads if you're curious about just when it was made, that would be a letter followed by 2 to 4 digits, such as D 12 71 is decoded as April (fourth month) 12 1971, or like B 5 9 is Feb (second month) 5th 1969.

 

Thanks guys - I have to look into whats involved down here with getting another engine number stamped into it before going ahead with any purchase. Hopefully my 74 Eldo sells tomorrow and I'll have 3/4 of the money for it.