1970-72 400ci Smallblock
Question:
All I need is the core of the block! Does anyone have one? It must have 4 bolt main caps and extra rod clearance grooves on the insides of the bottom of the block. I don’t care what it’s out of but I prefer that it has never been re-bored. Must be in good usable condition. Please reply with block numbers and original vehicle type if possible. TIA, Chris
Response:
>All I need is the core of the block! Does anyone have one?
FYI, this is not a smallblock. -Clint — Clint Olsen . __ ‘71 Chevy C/20 Fleetside P/U /o / o . __/
Response:
> >All I need is the core of the block! Does anyone have one? > FYI, this is not a smallblock. > -Clint
FYI, yes it is. :) If not, it’s really funny that 350 heads will fit on it.
Response:
>FYI, yes it is. :) >If not, it’s really funny that 350 heads will fit on it.
You’re trying to tell me that the 402ci engine on the Chevy trucks (which is based on the 396) from 70-72 is a smallblock? -Clint — Clint Olsen . __ ‘71 Chevy C/20 Fleetside P/U /o / o . __/
Response:
> >FYI, yes it is. :) >If not, it’s really funny that 350 heads will fit on it. > You’re trying to tell me that the 402ci engine on the Chevy trucks (which > is based on the 396) from 70-72 is a smallblock?
Nope! That (the 402) is indeed a big block. The 400 (less the 2 inches) is a small block. It’s pretty much a 350 with a longer stroke. (I said "pretty much" ok? No flames invited!)
Response:
>Nope! That (the 402) is indeed a big block. The 400 (less the 2 inches) >is a small block. >It’s pretty much a 350 with a longer stroke. (I said "pretty much" ok? >No flames invited!)
I was not aware that such an engine existed from GM at the time. It mustn’t been a Chevy, right? Perhaps Pontiac? -Clint
Response:
nope. it is a chevy engine. it has a 4.125 bore and a 3.75 stroke. it was made from 70-79 or 80 i think. it was usually installed in trucks, station wagons or full size cars. — chris http://www.racemart.com – Hide quoted text — Show quoted text ->Nope! That (the 402) is indeed a big block. The 400 (less the 2 inches) >is a small block. >It’s pretty much a 350 with a longer stroke. (I said "pretty much" ok? >No flames invited!) >I was not aware that such an engine existed from GM at the time. It >mustn’t been a Chevy, right? Perhaps Pontiac? >-Clint
Response:
400 small block chevy was made from 70-80 with a 4.125" bore and a 3.75" stroke. GM casting #’s are 3951511 (only one with 4-bolts) 3951509 (only has 2 freeze plugs) 330817 (least desireable, only 2-brl 180HP max factory rating) GM 402 big block is a 4.125 bore and a 3.76" stroke hence the extra 4 cubes. GM #’s are 3955272, 3969854, 3999290 & 6272177. The last 2 were 402 only from GM and the first 2 were 396 or 402 factory. Of course any 396 bored .030 was a 402 anyway! Small Block Chevy Mania http://www.chevymania.com
Response:
says… >All I need is the core of the block! Does anyone have one? >FYI, this is not a smallblock.
Since when? Hate to tell you this but the chevy 400 is a small block.
Response:
>I was not aware that such an engine existed from GM at the time. It >mustn’t been a Chevy, right? Perhaps Pontiac?
Nope again, Pontiac, like Olds 400 is a big block, the Ch*vy 400 is a small block
Response:
>>Nope! That (the 402) is indeed a big block. The 400 (less the 2 inches) >is a small block. >It’s pretty much a 350 with a longer stroke. (I said "pretty much" ok? >No flames invited!) >I was not aware that such an engine existed from GM at the time. It >mustn’t been a Chevy, right? Perhaps Pontiac? >-Clint
The 400 is indeed a small block Chevy. It looks just like any other small block, has a couple extra freeze plugs, and a weighted harmonic damper, other than that it looks just like a Chevy 350. The 400 was made with a 2bbl carb from 70-72, then with a 4bbl up to 1980. It hops up pretty well, but the early 2bbl engines were real slugs. Jim
Response:
There is a visible difference between the 400 and the 350. If you look at the cylinders the 400 actually bulges out a little.. Not much but enough so they could get the bigger slugs stuffed inside with some cylinder wall left over.. – Hide quoted text — Show quoted text -> The 400 is indeed a small block Chevy. It looks just like any other small > block, has a couple extra freeze plugs, and a weighted harmonic damper, other > than that it looks just like a Chevy 350. > The 400 was made with a 2bbl carb from 70-72, then with a 4bbl up to 1980. > It hops up pretty well, but the early 2bbl engines were real slugs. > Jim
Response:
The Pontiac Is NOT a small-block nor a big-block, but kind of a "mid-block". The blocks are all the same dimensions on the outside, except the 301. The main journals are larger on the bigger displacements, but that starts with the 421. – Hide quoted text — Show quoted text ->I was not aware that such an engine existed from GM at the time. It >mustn’t been a Chevy, right? Perhaps Pontiac? > Nope again, Pontiac, like Olds 400 is a big block, > the Ch*vy 400 is a small block
Response:
>The Pontiac Is NOT a small-block nor a big-block, but kind of a >"mid-block". The blocks are all the same dimensions on the outside, >except the 301. The main journals are larger on the bigger displacements, >but that starts with the 421.
Acctually the 400 pontiac is a large journal and small journal block. Dends on the the year and casting. > Nope again, Pontiac, like Olds 400 is a big block, > the Ch*vy 400 is a small block
Olds is like the pontiac the blocks are physicaly the same from the 307-455. Small Block Chevy Mania http://www.chevymania.com
Response:
>Olds is like the pontiac the blocks are physicaly the same from the >307-455. >Small Block >Chevy Mania
Olds big blocks, 400,425,455 are 2 inches wider and 1 inch higher than the 260,307,330,350,403 small blocks Long live the W-Machines
Response:
On this same discussion, I’ve heard that although a "Peppier" motor, small amounts of over-bore created a cooling problem. Something to do with the sleeve thickness during production. I’ve been told that .060 over was enough to weaken the bores, and although a really tough block as far as bottom went, any build-ups usually included re-sleeving. Any validity to any of this? Dan KC8GYS Electrical Engineering Technology http://mclelland.resnet.mtu.edu Houghton Michigan (Dats in Da U P Eah!) "Sleeping in class won’t get you anywhere… When you wake up, you’re still in class"
Response:
I’m a Ford guy (I’m not well aquainted with the General). The 400 small block Chevrolet engine looks similar to 307,327,350. Internally, the cylinder walls are "siamese". There is no space for water between the cylinders. 4.125 x 3.75 The 1970 2-jet models in station wagons were dogs. While training in Auto Mechanics class in the late 70’s we had two different station wagons that would not make it up the wheel alignment rack. It took myself and a fellow female classmate to push it up the ramp while the driver held the accellerator down. The engine was making lots of "bog" noise during the attempt. The 402 big block Chevrolet engine looks like a 396,427,454 and has always been called a 396 I think. (I thought. Chilton shows 396 and 400 as the same bore and stroke and (402) in parenthasis.) I’ve read somewhere that there were oversquare 396’s and undersquare 396’s. However, I can’t find that article. All the specs I’ve seen show oversquare bore x stroke. The 64-71 Chilton’s that I have shows 396’s as 1966 – 1969 396 4.094 x 3.076 and 1970 – 19?? 396(402) 4.126 x 3.096 1970 – 19?? 400(402) 4.126 x 3.096 The Pontiac/Oldmobile engines look the same to me. The ones I’ve seen have intake manifolds that look like intake ports welded together and a valley pan underneath. I’ve always wanted a Ford 427 SOHC, but I have a 1993 Crown Victoria with a 4.6L SOHC instead (281ci) Anyone selling a $300 -$700 VAXstation with monitor w/keybrd running OpenVMS?
Response:
> On this same discussion, I’ve heard that although a "Peppier" motor, small > amounts of over-bore created a cooling problem. Something to do with the > sleeve thickness during production. I’ve been told that .060 over was > enough to weaken the bores, and although a really tough block as far as > bottom went, any build-ups usually included re-sleeving. Any validity to > any of this? > Dan
Dan, the 400 did indeed have some overheating concerns, but it was not from the cylinder walls being too thin. The 400 was not just a 350 block bored and stroked. It had larger crankshaft bearings and siamesed cylinders. The cylinders were just too big around to have water passages between them, so GM moved the two inner cylinders on each bank out from center until they touched the end cylinders, so there is a pair of cylinders at each end with one water passage in the center of the bank instead of one between each cylinder. This restricted water flow gave them a tendency to overheat.
Response:
>Dan, the 400 did indeed have some overheating concerns, but it was not from >the cylinder walls being too thin. The 400 was not just a 350 block bored >and stroked. It had larger crankshaft bearings and siamesed cylinders. The >cylinders were just too big around to have water passages between them, so GM >moved the two inner cylinders on each bank out from center until they touched >the end cylinders, so there is a pair of cylinders at each end with one water >passage in the center of the bank instead of one between each cylinder. This >restricted water flow gave them a tendency to overheat.
This is all true up to the last statement. The 400 runing these siamesed cylinder walls added small holes drilled into the deck, gasket and heads. The "steam" holes were designed for low RPM venting of the steam buildup in these corners where the cylinders meet. At higher RPM coolant flow was enough to push the steam pockets away. The early hotrodders not knowing about or understanding the pourpous of these holes swaped the stock heads for performance heads from 350’s and 327’s. When this was done the holes were not in the replacement heads and this caused overheating. I own and run 4 406CID small block chevy’s 2 all out race and 2 street. Not one of them has ever overheated even in bumper to bumper traffic. Also on the overbore, not all 400’s were created equal. The early 330817 block was most common and was inferior to the 511 and 509 blocks. The most desireable block is a 3951509 because of it’s higher nickel content and thicker cylinder walls. If your going to bore a 400 any more than .030, even the 509 blocks, have the walls sonic tested first. This will determine if your block’s cylinders have enough material for larger overbore. One of my 400’s is .060 over and 1 is .040 while the others are .030. One of my .030 blocks does have enough material to go .060 though. Small Block Chevy Mania http://www.chevymania.com
Response:
>The 402 big block Chevrolet engine looks like a 396,427,454 and >has always been called a 396 I think. (I thought. Chilton shows 396 and 400
I don’t think that statement is correct… A friend has a GMC truck with a 402, and he has the original option sheet with "402" checked off… I’m not sure why Chiltons would have the 402 in brackets…
Response:
Sorry, guy. 400 Pontiacs are all the same journal size–3 inches. No ifs, ands, or buts. Always. As far as Olds goes, I think that the boys at 442.com would argue about no big or small-block engines. I don’t know personally. Terry – Hide quoted text — Show quoted text ->The Pontiac Is NOT a small-block nor a big-block, but kind of a >"mid-block". The blocks are all the same dimensions on the outside, >except the 301. The main journals are larger on the bigger displacements, >but that starts with the 421. > Acctually the 400 pontiac is a large journal and small journal block. > Dends on the the year and casting. >> Nope again, Pontiac, like Olds 400 is a big block, >> the Ch*vy 400 is a small block > Olds is like the pontiac the blocks are physicaly the same from the > 307-455. > Small Block > Chevy Mania > http://www.chevymania.com
Response:
> I don’t think that statement is correct… A friend has a GMC truck with a > 402, and he has the original option sheet with "402" checked off… I’m not > sure why Chiltons would have the 402 in brackets…
The 402 was often tagged as a "396" or "400" on the cars. Some chevies around 70 had 402’s (factory .030 over 396) but had either "396" or "400" fender emblems. And all things considered I would say that the 400 sb is quite different from the more common 350’s and other related small blocks. I’ve also heard that as long as you keep it a low rpm, high torque motor it would make a great street motor with the right set up.
Response:
- Hide quoted text — Show quoted text – > Also keep in mind that due to it’s shorter stroke the 400 is not a good candidate > for high rpm > applications. They do however make an excellent 4×4 motor.(with minor mods) > If built right the 400 is capable of exceptional low to midrange torque & > horsepower (475 hp > & around 450 ftlbs of torque) all right where a 4×4 needs it most … > the 400 was a favorite in suburbans. (The only Chev 4×4 I’ve owned that was worthy > of the title > 4X4) Now if I could only have kept transmissions in the thing, when it started to > eat tranny #5 > It went down the road… > >Dan, the 400 did indeed have some overheating concerns, but it was not from > >the cylinder walls being too thin. The 400 was not just a 350 block bored > >and stroked. It had larger crankshaft bearings and siamesed cylinders. The > >cylinders were just too big around to have water passages between them, so GM > >moved the two inner cylinders on each bank out from center until they touched > >the end cylinders, so there is a pair of cylinders at each end with one water > >passage in the center of the bank instead of one between each cylinder. This > >restricted water flow gave them a tendency to overheat. > This is all true up to the last statement. > The 400 runing these siamesed cylinder walls added small holes drilled > into the deck, gasket and heads. The "steam" holes were designed for > low RPM venting of the steam buildup in these corners where the > cylinders meet. At higher RPM coolant flow was enough to push the > steam pockets away. The early hotrodders not knowing about or > understanding the pourpous of these holes swaped the stock heads for > performance heads from 350’s and 327’s. When this was done the holes > were not in the replacement heads and this caused overheating. > I own and run 4 406CID small block chevy’s 2 all out race and 2 > street. Not one of them has ever overheated even in bumper to bumper > traffic. > Also on the overbore, not all 400’s were created equal. The early > 330817 block was most common and was inferior to the 511 and 509 > blocks. The most desireable block is a 3951509 because of it’s higher > nickel content and thicker cylinder walls. > If your going to bore a 400 any more than .030, even the 509 blocks, > have the walls sonic tested first. This will determine if your block’s > cylinders have enough material for larger overbore. > One of my 400’s is .060 over and 1 is .040 while the others are .030. > One of my .030 blocks does have enough material to go .060 though. > Small Block > Chevy Mania > http://www.chevymania.com > — > KC7YPJ, Ryan Dorman > QTH: Victor ID, grid# DN431c > ICQ #3834602 > http://www.geocities.com/Baja/Dunes/5496
Well here is topic to debate on to destroke a 400 SB or not to destroke.That is the question. The block is out of 79 GMC 4×4 pick up. The engine has about 180,000 miles on it. She had one light rebuild. I think the shop bored it .020 over. It been about 5 years. I have know problems with it over heating and I don’t wan’t too. I building the truck up again from the ground up. It has 4:10 for gears and 350th for Tranny. She will have 4" susp. lift and 35 for meat.The question is to bore the piss out of it and soup it up or to bore it .030 and destroke it for power and RPM’s. Who got some ideas. Jason from MT
Response:
- Hide quoted text — Show quoted text ->The 402 big block Chevrolet engine looks like a 396,427,454 and >has always been called a 396 I think. (I thought. Chilton shows 396 and 400 >I don’t think that statement is correct… A friend has a GMC truck with a >402, and he has the original option sheet with "402" checked off… I’m not >sure why Chiltons would have the 402 in brackets…
