Can you build a real Chevy 302?

Why are we discussing OT SBC's?

 

Very valid point!! The part where we talk about 283's being bored to 4'' to make a 301 are on topic or a (sj) 327 with a 283 crank. JW

 

Woke up this morning and just decided to open a can of worms on this discussion. It's the why that answers the how.

Fact: In 1966-69 SCCA TA rules indicated you may over-bore an engine, but not de-stroke; and no substituted blocks or cylinder heads from the 1000 production models produced. In 1970, the rules changed. See below

Engines may be modified or altered as desired except as follows: 1) Maximum displacement shall be 5000 cc and may be obtained by alteration of bore and/or stroke as desired. 2) Cylinder block and/or cylinder head(s) may not be substituted.

This is why Mopar ran an over-bored 273 in the 67' Dart, but remained out of SCCA TA until a modified 340 in the 1970 Challenger was allowed.

Back on topic... So as we can see the engine clearly was derived from a chance to race SCCA TA. Rules at time (1962-1969) say you can over-bore, but not de-stroke to achieve 305ci or 5000cc. This means you couldn't legally de-stroke a 327 to meet the rules (block numbers count), only over-boring a 283 would meet the rules until 1970 and by then we had large journals and more options.

From major magazine article on casting numbers:
3756519 Small Block V8 1958-1962 283, 2 bolt
3782870 Small Block V8 1962-1967 327, 2 bolt
3789817 Small Block V8 1962-1964 283, 2 bolt
3789817 Blocks Small Block V8 1962-1967 327, 2 bolt
3789935 Small Block V8 1961-1964 283, 2 bolt
3790721 Small Block V8 1962-1964 283, 2 bolt, recessed oil filter boss
3790721 Small Block V8 1965-1966 327, 2 bolt, recessed oil filter boss
3791362 Small Block V8 1962-1967 327, 2 bolt, recessed oil filter boss

No way those are different bore sbc, remember the factory can bore too.

Some questions I have read in this thread so far that can be lay to rest.
1. No small journal stuff came 4 bolt main, originally (you can add, or some folks have already).
2. All small journal cranks (4 barrel or FI equipped from factory) ping to a wrench and not pong, they are steel not cast iron.
3. Nova or Chevy II 283 engines are thin cast 2-barrel models and pong.
4. There are thick casted 283's with steel cranks, think large 4 door cars for 1961-63
5. Engine calculations, don't get hung up on 301, 302, 349, 350 almost none of these figured out to a round number. But we needed a Turbo-Fire 350, with a Turbo 350 transmission, yep marketing issue.

I love building these 283/302, here is a cheap recipe

Ole school 283 is what you're looking for, should be 283 found with 4-barrel carb rated around 250hp. It's a little Rochester carb, smaller than 4150 Holley pattern. For years I rounded up the ones from the lowrider scene, they wanted crate 350's. Lol, those Impalas were loaded with them, 4 door w/4v carb thick casted 283's. Machine in the 4" bore without concerns, don't use original powerpak heads. On these sourced 283's they have 70cc chambers, small valves, and small runners. Original 302 had 186 humps, other camel humps work too; need to stay at 64cc chambers for the 11.1:1 compression. Engine Labs tested a GM 302 against the 302 Boss (10.5 cr) May 2020, most important part of the test was the cams. GM 302 is a medium lift (480) with longer duration (250@.5 lift), Boss is high lift (.513) with shorter duration (225), little more top end between 6000 and 7000 rpm on the ford. GM 302 was winner from 2500 to 6000 rpm on torque and HP. Just remember when cam is selected, GM used 30-30.

Your last 283, okay so once you punch a 283 to a 4" bore its done after you wear it out. I have always enjoyed using the 283 up before I put the motor in Check as a game of chess. Fun 283 mod that is cheap and delivers some real benefit is heads. As stated, before I have found 4 variations in powerpack heads, and they all have small ports and ole school seats/guides which cause issue with unleaded fuel. However, real fun to be had with 416 heads from GM305 HO motors from 80's; bigger valves (still work in cylinder size), small 50cc chambers, and accessory bolt holes. Have fun

POS really
The Pontiac didn't have the engine displacement in 1968 and then used the 302ci CHEVROLET. PMD had to create a 303ci small block, based on 400 RAM AIR IV. bore/stroke: 4.12"x2.87" (compared to the 4.12"x3.75" 400ci) and TRW forged pistons that provide 12.5 compression. The valves were 1.73" and 2.19" in diameter. The fuel supply was entrusted with two 600cfm Holley carburetors. All this gave a very sophisticated engine with maximum torque located beyond 8000tr/min and 430 horses at the flywheel! This 303ci was installed in a Firebird Trans Am 1969 model and was stirring up trouble on the track, but it did not happen because the engine did not comply with the rules and was therefore not allowed to run.
The 303 was extended to 1970 when new rules came into being and support adaptation engine 305ci series of more than playing on ratings bore and stroke. Thus Chrysler, far away from these races, took the opportunity to adapt its V8-340 and run the Barracuda and Challenger.

 

It's all to complicated, their were no rules on the "street", stroke. bore, de-stroke, mix and match parts from wherever, to your hearts content. Wear it out, blow it up and do it all over again!

 

Wonder what iron AMC used?

 

Totally their own design engine. 304 was the same engine family as the 290.

 

Back in about 1971 a buddy of mine bought a 302 Fitted block from the local Chevy Garage for a little over 300 bucks. It came as a finished 4 inch bore block with 302 pistons and rings with it. Add a 283 Steel crank and a set of rods and a cam and you had a 302 short block ready to go. That one went in what became a pretty strong running 55 Chevy 2 door post. The long block wasn't very fancy as far as trick items went. 202 heads and a cam and kit.

 

Was said above (post # 483) that block #s count and you couldn't de stroke only overbore, BS, as the 67 SJ used a 327 block and LJ used the 010 4 bolt 350 block, and due to the years these Engines (302) are that really makes them OT. JW

 

I just got time to button up this hybrid. LJ block... SJ rotating assembly using Milodon thick main brgs.

 

As I posted in post #483 and here below again an excerpt of casting numbers for SBC, SJ or small journal up to 1967. Take notice that the numbers get higher as they go down, also notice 283 and 327 castings with the same casting numbers. Also notice that towards the end of the run-on exact casting numbers that GM couldn't find any other buyers on a 283 so they bored the remaining blocks as 327's. For instance, on the 3790721-casting number GM decided 283's from 1962-1964 and in 1965 to just bore the remaining castings until 1966.

3782870 Small Block V8 1962-1967 327, 2 bolt
3789817 Small Block V8 1962-1964 283, 2 bolt
3789817 Blocks Small Block V8 1962-1967 327, 2 bolt
3789935 Small Block V8 1961-1964 283, 2 bolt
3790721 Small Block V8 1962-1964 283, 2 bolt, recessed oil filter boss
3790721 Small Block V8 1965-1966 327, 2 bolt, recessed oil filter boss

Hint, Hint, the 3789817-casting listed above 283's can handle a 4" bore as GM did it from 1962-1967 on the 327's with same casting. In fact, they liked it so much the bored 327 version last 3 years longer than the 283 version that started the casting. Impalas, you can still love them in a new way, donors include 4 door 283 w/4v Rochester carbs.

In 1968 GM made all SBC (except 400ci is larger, more on that in a minute Doug, nice tunnel) LJ or large journal.
As you can see below in 1968 all the 4" bores shared the same casting Number, even the precious DZ 302 (Z28) sitting there all just regular amongst all the 2 bolts mains.

3914660 Small Block V8 1968 327, 2 bolt
3914678 Small Block V8 1968 302, 2 bolt, Camaro Z28
3914678 Small Block V8 1968 327, 2 bolt
3914678 Small Block V8 1968 350, 2 bolt
3932371 Small Block V8 1969-1973 307, 2 bolt

Back on topic... If you want a pre-1968 DZ 302, overbore a 283 and be right.
Post-1968 DZ(Z28) 302's would be cheaper to build except the crank, no large journal 3-inch stroke cranks, 3.25 is shortest stroke offered post 1968.

Now Doug has a nice little small block and mentioned bearing spacers for LJ and SJ play. I have experience with making something out of nothing, meaning after everyone built 383's there was a ton of 400ci blocks and 350 cranks just lying around. Comp Cams makes spacers for the 377's we use in the IMCA modified. Different story but shout out to Doug.

 

Welcome to the HAMB. JW

 

Going in... loaning this 302 to brother. Need room on engine stand. For my 67 302 build.

Probably run tunnel first, then switch to single 4bbl. Run the early Nova next year, see what it can do..

 

I have one more 302 build, then might have a free spare s.j. 302 crank for someone to build from.

 

To me for a SBC street motor a small journal 327 block forged 283 crank ( most were) good heads and I love the 097 cam. It has low lift so it's easy on the valve springs for a street car In a light manual trams' car it's a screamer. A 3 inch crank small journal 2 bolt block will be fine

 

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