Home Grown 302

[bparks6446]

I have recently been looking into building my own 302 like those found in 1st Gen Z28's. I have a 1967 327 to start with, and I know i'm gonna have to get ahold of a 283 crank. But are there any other words of wisdom before I go all out with this project.

I also have a mid 80's 305 (complete), and an early 70's 400 (block only). I'm open to project ideas, and would value some good opinions

 

[hurst01]

Hi bparks6446,

Welcome to the forum. I have been out for a while because of some eye problems. First, let me say that the 302 was a fine engine. It's main characteristic was high RPM and quick revving because of the shorter stroke. It didn't have the torque that the 327 or 350 had, but it made up for it by revving quickly... it was nothing to see one turn 10,000 RPM. Another good thing was the 283 and 302 both had forged cranks.
You can build one by using a 283 crank with your 327 block (providing the cylinder walls are good) and purchasing some 302 pistons. Should you have to bore it, I would not go past .030 over. Another thing to think about is the cam. The 69 302 was a mechanical flat-tappet cam. In 1970 they changed the specs of the cam and began using a hydraulic cam instead of the mechanical. Something that was fairly close to the original 69 302 cam was something that was referred to as the 30-30 cam. It got it's name from the clearances of the intake and exhaust adjustments... .030 of the intake and .030 for the exhaust. The 1970 year cam didn't have the sound of the original, but it was quite a bit nicer to not have to adjust the valves once a week.
Keep us up to date on your progress.

 

[Hog]

I have recently been looking into building my own 302 like those found in 1st Gen Z28's. I have a 1967 327 to start with, and I know i'm gonna have to get a hold of a 283 crank. But are there any other words of wisdom before I go all out with this project.

I also have a mid 80's 305 (complete), and an early 70's 400 (block only). I'm open to project ideas, and would value some good opinions

Not really going to help with your existing parts, maybe the block since it is a 4" block.But.....

If you find a used 1994-1996 GEn 2 L99 4.3(265cid) V8 yes, Vee-eight from the same years Caprice, you can use its 3" stroke nodular iron (not as strong as forged, but stronger than cast iron) 1 piece rear main seal(RMS) and its 5.94" Powedered Metal(PM) forged connecting rods, coupled with stock LT1 350/Vortec 350 hyperutectic pistons(again not as durable as forged, but better than straight cast aluminum piston).
The 4" 350 pistons and 3" L99 crank nets you a modern 302(5.0L) engine.

Raceshop did exactly this by using the L99 3: crank, L99 5.94" con rods,
350 pistons,
modern 350(4"bore) 1 piece RMS block,
ZZ4 crate engine hydraulic roller cam(10185071) 208º/221º duration at 0.050" lift and 0.480"/0.510" lift on a 112º LSA,
along with aluminum GEn 2 LT1 350 cylinder heads,
single roller timing chain and sprockets(14088783),(14088784)
Crane H-11 tool steel valve springs
Camaro 75mm MAF sensor
HPC coated 1.5" x 30" headers
Flowmaster mandrel bent 2.5" exhaust
1995 sequential injection GM PCM
lightweight (10lb) PMGR LT1 starter 10465293
94-94 Impala SS fuel sender and pump
Corvette 7 rib valve covers 24502540

Trans
1995 GM 4l60e trans
PCM controlled 7000rpm shiftpoints
high stall L35 4.3 V6 locking torque converter 24202310 (alphanumeric code for this 4.3 TC is DBLF) behind my Vortec 350 in my 97 reg cab 2wd truck I can footstall to 2800rpm

rearend
1990 T-truck (4wd S-10) 7.625" rear axle
Auburn limited slip 30 spline axles 3.23+ carrier
4.56:1 gears

they put all this into a shoebox, 1955 IIRC.
he engine made:
329hp @ 6500rpm
273 lb/ft torque @ 6000rpm Npt bad for 100% GM parts pulled out of the Chevrolet parts bin.

Shiftpoints were set at 7000rpm and hardlimit fuel shutoff for the LT1 PCM's occurs at 7300-7400rpm when the rev limit is set to the highest numerical input the PCM will accept.

Maybe you can use your existing 4" bore 302/327/350 block and use an adapter to use the 1 pice RMS in your 4" bore 2 pice RMS block?

Whatever a 302 goes into it will want low low gearing, a close ratio manual transmission or auto with a high stall speed and light vehicle weight to match the combo.
I respect the aura of teh 302, but this aura was was developed at a time when the 350 did not exist yet, it was only built to stay under the 305 cid disploacement rule of teh day. As soon as the displacement band was raised, the 350 engine was introduced in the Z-28 as the LT1 with its 370hp in Vettes and 360hp in the Z-28. The 1967 302 used the small journals (2.30"/2.0") while the 1968-69 DZ302 used the larger(medium) journals (2.45"/2.10").
Put the same parts in a 350 cid engine and you will make more power, plus make more useable torque to get the car moving. A 302 will not necessarily rev higher than a 350 will, but if you use EXATLY the same parts between the 2 engines, the smalled engine will make its power at a higher rpm thanteh larger engine, simply because of the volume of air the engines injest. These volumes will be the same when the 350 is at lower rpm than the 302 would be.
Its not because of the shorter stroke, the shorter stroke would only allow a higher rev limit at a much higher rpm as the piston speeds are much higher with the higher stroke of teh 350.

peace
Hog

 

[hurst01]

Nice going Hog! This is why this is called forum, so that everyone can participate in different areas of their experiences. Not many participate with the 302 because of the much better torque that can be obtained by the larger cube engines. But, my hat is off to the original 302 DZ. As you mentioned above, the 302 would not rev higher, but was able to rev much quicker because of the shorter stroke. Also, because of the shorter stroke there was less centrifical force due to less mass of the crank throws.
On the other hand, I have seen the stock 302 Z-28 rev 10K when they first hit the street during street races.

For obtaining a high output engine (torque and HP), as much as I liked the 302, you can get more with a longer stroke. Still, having a stock SBC 302 DZ sitting in a 69 Z-28 can bring a lot of big bucks. Was it your 55 that the engine was put in? If so, what kind of performance did you get? A 55 was a relatively light car to begin with and would scream with the original 265 and 283. I've seen a lot of 283s bored to 302 (301.58) before the 302 ever was heard of for production purposes.

Thanks for your contribution and hope to see you here often.

 

[hurst01]

Another thing I wanted to add... I had a friend that had a brand new 69 Z-28 with 302. I had a brand new 69 Camaro SS 396/375 4-speed (both cars). His car would run circles around mine all day long. Another friend had a 69 Chevelle SS 396/350 4 speed. The 69 Z-28 would run circles around his also. Small cubes as they were, they were freaks of nature and could hold their own against cars with much larger cubic inches, including the Dodge 440 6-packs. Makes me want to build one again myself.

I was talking to a Tennessee State Police officer back then and asked what kind of car gave him the most difficulty during a chase. He told me the 69 Z-28 was the only thing on the road that he could not catch. That was quite a statement for the small cube V-8.

 

[greenhornet-1]

Hog, I have 2 of tose 4.3 v-8 cranks as we speak. I was thinking the same thing on building a 302. Back in the 80's i built a Vega with a 302 out of a 69 camaro and it was unreal how that thing would rev!!!

 

[Hog]

Cool, build her up and make some vids.

peace
Hog

 

[hurst01]

Hog,

I don't know how I overlooked what you said about using the 3" stroke crank from the 4.3 V-8 and the stock pistons from the 350 LT1 engine but that won't work. The wrist pin location on the 350 pistons coupled with the 3" stroke crank from the 4.3 will leave you with a deck height of .480, which means the piston will stop it's upward movement .480 before it reaches TDC.
In order to have the correct deck height he will have to use a piston specially made for the stroke of the 302 that will allow the piston to travel to the correct deck height.
When I was working for a speed shop in my younger days I saw the owner assemble an engine using a 3" stroke and 327 pistons just to see how it would work. It did run but was a absolute DOG because the pistons stopped their travel 1/4" before the piston reached the proper deck height.

 

[Hog]

Hog,

I don't know how I overlooked what you said about using the 3" stroke crank from the 4.3 V-8 and the stock pistons from the 350 LT1 engine but that won't work. The wrist pin location on the 350 pistons coupled with the 3" stroke crank from the 4.3 will leave you with a deck height of .480, which means the piston will stop it's upward movement .480 before it reaches TDC.
In order to have the correct deck height he will have to use a piston specially made for the stroke of the 302 that will allow the piston to travel to the correct deck height.
When I was working for a speed shop in my younger days I saw the owner assemble an engine using a 3" stroke and 327 pistons just to see how it would work. It did run but was a absolute DOG because the pistons stopped their travel 1/4" before the piston reached the proper deck height.

It does work and works well. Thats why you need to use the 94-96 L99 4.3 V8's 5.94" rods, instead of the normal 5.7" rods.
Stock Vortec 350, LT1 350 pistons, along with the stock L99 3.00" stroke crank and the L99 5.94" rods will give you a decent running 302 cube engine, that if using LT1 heads and a ZZ3/4 roller cam will give you 329hp @ 6500rpm
273 lb/ft torque @ 6000rpm.

peace
Hog

 

[hurst01]

Hog,

I stand corrected, I failed to read the "use of the 5.94" rods". I have to admit, this is not the first time I have overlooked something . It will probably happen again. Now my question would be, although it will work... why lose that additional torque unless you would want it to be withing a certain "class" for cubic inch purposes.
Then again, that is what makes the world go around. Otherwise called different "strokes" for different folks :lol:.

 

[greenhornet-1]

You know what sucks, I think i scraped the 2 sets of rods i had as not to get them mixed up with the 5.7's....

 

[Hog]

Hog,

I stand corrected, I failed to read the "use of the 5.94" rods". I have to admit, this is not the first time I have overlooked something . It will probably happen again. Now my question would be, although it will work... why lose that additional torque unless you would want it to be withing a certain "class" for cubic inch purposes.
Then again, that is what makes the world go around. Otherwise called different "strokes" for different folks :lol:.

No problem, I overlook things all the time. Nobody, esp me is perfect.

One reason would be for fuel economy, I mean that is why GM developed teh 94-96 200hp/240lb/ft torque L99 4.3 V8 instead of the iron head LT1 in the Caprice in the 1st place.

No real reason to build the 302 over a 350, unless as you say there is a cubic inch rule, like was the reason the 302 was built for 67-69 in the 1st place. As soon as the limit was raised, CHev immediatley went to he 350 cube LT-1.

A lot of people brag about the 302's hig rev prowess, but this really isnt because of its bore an stroke, it basically is a function of how much air it pumps through it. If you have teh same heads/cam/intake carb on a 302 and a 350, the 302 will make its power and torque peaks at a higher rpm than the 350. Not necessarily an advantage, just a result of less volume of air per revolution. There are small advantages as the rings dont move as far up and down the bore, but they are small. All else equal, a 350 will spank a 302.

A 302 would be fun with a 4000rpm stall converter in a light car with decent gearing, but all else equal a 350 would be more driveable and make more power/torque.

peace
Hog