Thread: 302 build

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Hi all, I've got a late 70s to early 80s (going to have to check) SBC sitting in my yard and I've decided to lift it and put it to some real use.

Now before you look at me all crazy like, I can imagine what you're thinking, "Why destroke the 350?" the answer is complicated, this engine will most likely be tagging out a tired V-6 from a Pontiac Fiero, the limited selection of transmissions for these cars puts a serious damper on how much bottom end torque I want to be wielding around it's fragile little 1st and 2nd gear teeth... the emphasis here is on as LIGHT shock-loading on the transmission off the line as possible. As I am 19, will be taking it to the strip, and will most likely be stressing the engine, I am simply going on the knowledge that 302s were known to be a bit tamer torque-wise in the bottom end than similar displacement, or larger, small block Chevys, until they reached some higher RPMs where they picked up like mad. I know camshafts have a huge effect on powerbands, it's also the high-reving nature of the engine that is appealing to me (despite similar revs from 350+ these days).

The concept I have is to pull the 3" crank/ 5.940" rods from a 1994-1996 4.3L Caprice block and to swap them into the 350 bottom end, effectively destroking it to 302CI. Heads will be essential to reach my initial 350ishHP (havn't decided weather this is going to be WHP or not yet...) goal, and I am seriously considering a set of small-port Iron Bow-Tie Vortec heads paired with a single plane Vortec intake (I have a link to 105 dyno pulls where this setup hit the highest numbers for Vortec combos). I have to consider a cam as well as aftermarket valve-train components, which is where I could use a little bit of advice.

As I'm leaning towards iron heads obviously this is a bit of a budget build, I would LIKE to spend less than 3x the cost of the car and insurance combined on just my engine but any input or particularly any experience with 302s is welcome!

I admire your spirit. You're thinking outside the box. Here are a couple of my thoughts on this.

The early block is a 2-piece rear seal. The late crank uses a 1-piece seal. Have you figured out how to do this?

Will you be able to get high-compression L99 pistons off the shelf? The rods are longer, so the pin will be higher than a 302 piston. What about the L99 piston crown design and valve reliefs mating up with a Vortec chamber and valves?

If you can get around these issues and keep cost down, congratulations. The alternative might be to check with one of the hot rod Chevy dealers like Scoggin-Dickey and price a 302 crank. A 1969 crank should have had large journals and would be a drop-in in your 350 block. With 5.7 rods, you should be able to find off the shelf pistons for the required 11.0:1 static c.r. Use a solid lifter cam with an operating range of 3,500 to 7,500 with an intake closing point of 55 degrees after bottom dead center. This should yield a dynamic compression ratio of around 8.2:1. You should be able to run pump gas with it if you keep the squish at 0.035". You could do that by popping the piston out of the bore by 0.006" at TDC and running a Fel-Pro 1003 head gasket. At 7,500, the beast will inhale 655 cfm, so a 700 cfm carb should do the trick.

I'm glad you bring up these clearance issues, these are things I should indeed be looking into, especially weather I will be able to use that crank from the L99.

I feel a bit like a fool, I didn't explain that I wasn't planning on using the L99 pistons, simply the crank and rods, but I'm unsure as to weather the rods will even clear the cam or fit the pistons anyways, I guess I must do this methodically, start with a 3" crank that will work, then find rods that will fit the crank and clear the cam, then find pistons which will fit both the rods and play nice with the heads.

I remember the original cranks changed between different years of production, that journal size is pretty important, I'll make SURE to match them prior to buying if I go with a 1960s style 3" crank, you say I might actually be able to order one? Would it be reproduction or refurbished? Custom reproduction may be useful if I chose to go for stronger internals, but that means more money.

Forgive me for sounding ignorant but I've only been dealing with aftermarket rods up until now and this is my very FIRST build, aren't my stock 350 rods 5.7"? Doubtful on how well they would hold up if I reused them though, the engine will be pushing high revs on a regular basis, hopefully not killing it's longevity too much...

I would love it if I managed to keep excellent breathing/torque/power while maintaining a tame compression, I'd like to run it on regular gas even? (embarassing, but even mileage is nice these days). The car is going to be a daily driver that I can take to the strip to shake things up whenever it strikes me(I'm looking at 2800lbs after the swap on a FAT day, even with iron heads), so I'd prefer to keep compression and powerband streetable while still running some nice high RPM muscle under the deck.

Hopefully with some legwork and some phone calls things will begin to come together in the next little while, at least some outlying details and parts sources, possibly even cold hard parts numbers. Like I said before, I'm aiming for the end result to be a streetable but beastly engine, it is a 302 after all and I feel responsible to make it live up to the pedigree at least a LITTLE bit. So more than anything I hope the resulting power will be enough to justify the lengths gone into creating such a one-off example. At the same time I'm really looking for an engine that will stick around and be somewhat practical (mileage that doesn't make you grimace, all-racing powerband etc.) because it's a pretty big investment from my standpoint, and I hope to use it for a while, you get attatched to these big hunks of metal.

why hello there, i run 283/301/302's myself here. i used my stock gm 283 rods and crank. the rods are shotpeened. for strength and i shift at 7-7500 every single pass at the track. no worries on stock rods. i made my 302 a little differntly by taking a 283 and boriing .125 to 301.6 <aw its only .4 off!> and yes your stock rods will be of the 5.7 icnh variety. need anymore just ask im always here! ....scooter p.s. way to think outside the box!

nfswift,
sounds like your building a kickin lil mill, and put alot of thought into it..
did you say you were puting it in a fiero? if so i knew a guy that had a 406 sbc in one with a auto it was very quick and wouldnt even sqeek the tires.

i was thinking about trying to destroke my lt1 but im not sure..
well best of luck

Harmon

The '68 and '69 Camaro Z28 302 motors used a crank with the larger (2.45"/2.10") journals. It should bolt right into your 350 block. Casting number on the '68 crank is 3923279, '69 is 3941178.

Scooter has done a bunch of those bored out 283 blocks, but you'd be much better off in my opinion to use a Z28 crank in a 350 block. The cylinder walls wouldn't be so thin.

Like I said, call some of the Chevy parts departments and see if they just might have one on the shelf. Also do a search for the crank on Google.

not that thin

Thanks Scooter, that's great to hear you're running a nice little small-small block. 7,500RPM shift points sure do sound nice to me... from your experience with these high revvers do they require more maintainence than you're average smallblocks from winding them out so much or are they fairly hassle-free?

Out of curiosity what's your Nova run in the 1/4? Have you dyno'd your set up, or do you have a rough HP estimate? I'm just trying to get a general idea of how much I am going to be able to make given a certain budget on certain parts. I may pick your brain about cranks/rods/cams/heads/everything if it's no bother!

Thanks as well Chevyboy. Yep, the plan is for this to sit in a Fiero. I too have heard of a 406 in a Fiero, I'm impressed that the driver had it down to such a science, lighting up the back end in such a little car with that kind of torque should be as easy as breathing on the throttle, even with the superb weight transfer of a mid-rear car. I bet it was a quick one! If you're considering destroking, you're LT1 should work fine, any 4" bore blocks can be shortened up to 302s as long as the crank will work out.

Tech: thanks for the parts numbers and the journal tip, I thought it was the later years that the journal fit properly, I guess I must have read the right info somewhere. If I don't find such a vintage type crank from parts departments I always have the option of running a regular 283 crank like Scooter.

"If I don't find such a vintage type crank from parts departments I always have the option of running a regular 283 crank like Scooter."

The main journals and the rod journals are smaller on the 283 crank, so it is not a drop in in a 350 block. Someone may make thick bearings to make it work, but I'm gettin' a little fuzzy on that in my old age.

i run 12.60s HP not sure yet as i dont have slicks and pulling 2 second 60 foot times its hard to guess accuratley a lot of time is wasted spinning the tires.

Hmm, crap, because I found a shop that apparently makes adaptors for 1-2 piece rear seals. Hopefully those large journal 283 cranks are magically common every day finds... Xfingers.

Are you sure the L99 3" has small journals?

That sounds like a mean car Scooter. I'd love to hit low 12s, how streetable is yours? Pump gas? Daily-driveable? Stall setup?

pump gas? i run 12:5-1 compression it will run on a 92 with octane booster with no ping. trick makes more power. my new stall is a 10 inch 3500. i did have a 9 inch 4500 not streetable! it could be a daily driver if i put 3.73 gears in it. doubt it'd run 12's then the car is just like what has been pin striped on the core support for 17 years "Barley Legal"

just checkin around, where in victoria are u NFSWIFT??

i too am in victoria and interested in building a 302, i already have the complete 283 and i've located a 327 down near my place in san francisco.

i think that is one way to build one(dunno for sure)

In case anyone is wondering,,,,Childs-Albert makes the bearing spacers to use the small journal 283 crank(their all small journal) in a 350 block,they are the only ones I can find that sells them. Thats the good news! Now for the bad news,,,( Scooter,,,why don't you ever tell us these things?) The cost is almost $300 with tx. What,,,how cheap is that 383 to build? PS- after loseing your butt with the spacers,,,want to hear how much the 'special' pistons will cost you and your Wal-mart shopping wife???

Originally Posted by gassersrule_196

pump gas? i run 12:5-1 compression it will run on a 92 with octane booster with no ping. trick makes more power. my new stall is a 10 inch 3500. i did have a 9 inch 4500 not streetable! it could be a daily driver if i put 3.73 gears in it. doubt it'd run 12's then the car is just like what has been pin striped on the core support for 17 years "Barley Legal"

Oh Scooter, you're such a kidder !!!!!