Thread: Big block motor build help

Tweet

Hello all,
i`m new here and from hastings florida.I got a 1980 chevy c10 stepside thats under restomodding.It`s dropped 4 1/2 inches in the front and 4 inches in the rear. A 12 bolt 3.73 rearend and gona have a 700 r4 tranny.I got a question regarding a big block.About 5 years ago i bought a 396 shortblock but disassembled and came with it was a 1972 402 2 bolt main block with main caps.The 396 was from a 68 truck and the 402 was from a chevelle.But i`m leaning towards the 402 since its a virgin block and i`m starting with a base.I know alot of people would get tired of answering this but what would you all reccomend to do for a rotating assembly and to produce close if not over 450 HP out of the 402? I got a set of 049 oval port heads that need to be redone as well. Any and all info would be greatly appreciated.

thanks
pat

A couple things to remember/consider as you contemplate your engine build. The 396/402 and 427 all used the same (stroke is 3.76) crank. The bores obviously are different. In their stock configuration, all of these engines used a 6.135 rod length. There are some very good crankshaft/rod/piston kits available that use the stock dimensions. The reason I mention this is that by using stock components, you avoid machine work and know going in that the reciprocating mass will function as intended and have proper clearances. GM part numbers 3882841 (OEM in high performance 396) and 3882842 (OEM in high performance 427) are really good crankshafts. Both are forged, cross drilled, and nitride treated [improved overall strength and gives a very hard surface].

The 049 heads are pretty good. You probably have stock valves (2.06/1.72) but with a bit of machine work will accept the larger (2.19/1.88) valves that will certainly help in your quest for 450HP. I like dual springs, but there are certainly good single options and I would defer to the wisdom of others on this site for specifics here. A stock ratio (1.7) roller tip rocker arm is probably a good investment (less that $200) as well if you have the cash. Otherwise, the stockers are ok.

My number one suggestion is to keep your cam “streetable”, that is, don’t get too aggressive. A BB should produce a gob of low end and pull strong to 5000RPM plus while still behaving at idle. I always have to smile when a hear what sounds like an “eight cylinder Harley” that smells like raw gas and performs like crap and the owner can’t seem to figure out what when wrong when the cam is just too aggressive for anything less than a funny car.

Intake and carb options are numerous. I’ve always had good lock with Edelbrock manifolds and their carbs work well out of the box. Probably a Performer 2161 and a 750 cfm carb with an electric choke like the Edelbrock 1411 would give you great results.

Good luck and remember to have fun while you’re doing all this work

Use a Performer RPM intake. It's not too much for a street runner and will show more hp and torque over a standard Performer, expecially with headers. That's the key to making a crisp motor, let it breathe on the top and exhale properly on the sides

yes and belive it or not, you could build a q-jet to perform flawlessly

Good call Techinspector - the Performer RPM is a 7161 for the BB Chevy.

Originally Posted by gassersrule_196

yes and belive it or not, you could build a q-jet to perform flawlessly

Best carburetor ever designed. Those who call it Quadrajunk and other such things have simply not learned how to tune them.

Also good call by Gassersrule. I love the sound of those huge secondaries coming to life on the quadrajet!

Ok now for a few more questions, are the 049 heads a good set? I was told they were but see i`m new to the big block scene and like to try and know as much as i can.Also for a rotating assembly is stock ok with the horsepower wants? I know the turkey rod run is about 5 weeks away in daytona beach florida so i`m trying to get a list together to get some things like crank, rods, pistons, intake and camshaft.I paln on going with a good set of ceramic coated headers for it.But what turned me on to a big block was the firig up sound of 1.I was like a kid in a candy store when i hear a big block fire up.I like small blocks but i never owned a big block till about 5 years ago and now finally getting to building 1 while restomodding my truck.

thanks
pat

Is there a rotating assembly i can get that`ll be perfectly matched up to this block? Like SCAT or EAGLE? I want this thing to definately be a road banger and a definate import terrorizer. Plus would just a stock cranks and a set of reconditioned rods do the trick? I`m going to the turkey rod run show next month and i like to find a rotating assembly but if i can i like to find a 454 and build that instead.I know 454s are more plentiful then the 402s and truthfully i had a chance to get 1 for 500.00 but was short and he sold it and turned out to be a 4 bolt main.(man i was dumb not getting it).But i can find a 454 locally and would that be the wiser choice and then just put thi 402 aside or sell it? I wont sell the 396 so lets hear your thoughts?

thanks
pat

Heres a question.Would it be better to just build a 454 and sell the 402?I wont sell the 396 i got but since the 402 is just a block i figure it be more wiser to start with a complete or a shot block motor So i`m trying to get a better idea on what to do as if i go that route would anyone give me a idea on a good idea what this 402 2 bolt main block go for?

thanks
pat

the last 402 i did i lost my A$$ on geat engines but every one wants bigger then 454 for a driver a sbc but for big TQ and power the bbc and i have built many 496 and up the 402 would be good but would be easer to go up on CID like the 454 + if you do not have a 454 then i would build the 402 with some small head work and a hyd roller cam will work good .BUT i may not be the best to post on this i drive a blown 548 and a 632 on the street and think thats just fine and plan to go much bigger

I dont have a 454 yet but i am looking for suggestions as to what to do tothis 402 then.I got a set of 049 heads that need rebuilding and i`m looking at the easiest way to build a big block to produce 450 HP.I`m not 1 for bigger cubes i`m 1 for a healthy sound and a definate rumble and something noone has seen like this 402 for instance under the hood of my 80 c10 once completed.I know everyone says build a 454 or bigger.But I`m not looking for the cheapest way to build 1 just the smartest way to build 1 and get the asking HP out of it.I also forgot to mention this truck i`m building is for my mother so i dont really want to go over 450hp or she may be in more trouble then what its worth lol....

thanks
pat

[QUOTE=80 BB stepside]I dont have a 454 yet but i am looking for suggestions as to what to do tothis 402 then.I got a set of 049 heads that need rebuilding and i`m looking at the easiest way to build a big block to produce 450 HP.I`m not 1 for bigger cubes i`m 1 for a healthy sound and a definate rumble and something noone has seen like this 402 for instance under the hood of my 80 c10 once completed.I know everyone says build a 454 or bigger.But I`m not looking for the cheapest way to build 1 just the smartest way to build 1 and get the asking HP out of it.I also forgot to mention this truck i`m building is for my mother so i dont really want to go over 450hp or she may be in more trouble then what its worth lol....................................WELL the smart way could be a 402?? you have that ... and get it to 400 hp EZ to do but them 049 heads will take a hell of a dome to get any cr the 402 is not a cheap way to go but if you have it use it . a 454 has more pistons availability in many forms cast hyper forged i would build the for max QT not your HP all mine bbc i have built over my 25 + years of building them they all sound healthy They are bbc

I may have found a complete 427 rotating assembly for 375.00 so we will see how that goes so if it does i`ll post some pics on it.

thanks
pat

Originally Posted by 80 BB stepside

I may have found a complete 427 rotating assembly for 375.00 so we will see how that goes so if it does i`ll post some pics on it.

thanks
pat

make sure it is not a tall deck 10.200 block you do know you can make a 427 out of your 402? KB sells a piston and you use a 454 crank did a mass for a guy not to big of a deal