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302 Chevy Specs

32K views 87 replies 27 participants last post by  cletus van damme  
#1 ·
Hi Everyone, I was wondering if anyone knew where I could find the factory hp and rpm specs for the 67-69 chevy 302. I showed my dad a video of one being dyno'd and he doesnt believe me that it was a stock engine. I tried to explain to him that it was a factory trans am racing engine, but he says that there is no way that a stock engine will go to 8500 rpm without floating the points. My dad knows a lot of stuff about cars and has a hard time admitting that he doesnt know about this, if you know of somewhere that I could prove that Im right it would be great, thanks in advance. ;)
 
#4 ·
Horsepower @ rpm: 290 @ 5800
Torque @ rpm: 290 @ 4200

Although GM underrated this motor and it probably made more like 350 hp, the cam used wouldn't have been efficient at up to 8,500 rpm's and it isn't likely that the single point ignition would have been good for more than about 7,000 rpm's, even with a stout spring.

Us old guys were there when it actually happened and are immune to revisionist history. Open your dad a cold beer.
 
#6 ·
what we have now compared to then is a great difference. We all know the 302 chevy was a racing engine, and it put out more than what chevy said it did. Anyways, back in those days, the factory also held back more than what we were given, they had the funds and time to experiment with ignition systems while the average shade tree joes like us did not. they had something to hide then due to the horsepower wars. By the time the early 70's rolled around and the smog police like the EPA and the gov had stepped in, why hide anything when it can be used to gain sales? this is why the HEI was introduced, it did everything better than points did, and lasted so much longer, it was on vehicles as early as late 74, right at the dying end of the horsepower wars, how do we know a small cap version wasnt held back? we dont, we also dont know if GM had some kind of special version or anything else up there sleeve. I have heard of anti float points, but wasnt around early enough to experience them, I came around in the HEI age, and I still say to this day, the best place for points is the trash.
 
#7 ·
I'd have to go with tecni... we both were around when these really hit the street and tracks. I spent a lot of time on the Sun machine back then and it was a good project to get single points to run 7000+. You could do it for a short time but the rubbing block wore out pretty quickly. I made my own dual points conversions for years before the Z was around. I even made some dual point dual coil before you could get a good coil. When Accel and Mallory came around the home made stuff was shelved.

As for how fast the stock Z-28 302 was well with a 4.56 gear they were ok but even at $.30 per gallon they were real guzzlers. My BIL had one and I totally owned him with my 396 Chevelle SS. We even switched drivers and it still was not a match. Around the corners well it was tough to beat the Z but with the metalic brakes on the 396 a parking lot race was a lot of fun. there was as much smoke coming off the brakes as the tires . haha My BIL was not a driver and got the crap scared out of him when I took him for a ride in the 396. haha

The Z was a respectable road racer that it was designed for but not a match for the SS of the day on the drag strip.

We bought a crate Z 302 and ran it in our JR fuel dragster. It lived a short life on 80%. With new pistons and rods it was a pretty cheap motor that ran very well.
 
#8 ·
I don't think they were so much under-rated as they were under-revved at the time they were rated. 290hp at 5800rpm was most likely an honest number, but I strongly suspect the horsepower would have been a lot higher if they hadn't shut down the dyno at 5800.
 
#9 ·
I'm with Jim on this, talked to the guys at Westech dyno once about this. Chevy purposely shut it down at 5800 rpm because thats where it REALLY started to make it's power. It was good to 7200 rpm and 420 hp. Ford and AMC did the same thing with thier Trans Am engine program.

Also Bentwings, not to argue but I didn't think you could buy a crate DZ motor back then.........unless you knew somebody????
 
#10 ·
Sorry, we did, several short blocks. These were before the crate motor craze. Probably the first of the crate motors. They worked great in the JR. Fuel dragster as long as you stayed below 80% and didn't get too crazy with the mag and opened up the top ring gap. I can't remember exactly but I think we paid about 400-450 each. We took the stock cam out and put our roller cam in, did the rings, bolted the Mondellos on, Enderle injectors, Vertex mag and went racing.

We pounded the living daylights out of the pistons. You would not believe some of the things I did to pistons back them. Not the least was TIG welding them and using double top rings.

Stock pistons were harder to come by so we just used the TRW replacements. They worked about the same and were dirt cheap.
 
#11 ·
well youve hit my soft spot chevy 301-302's i love em!. i currently run one mine is a poormans 301 <283 bored .125> all the specs are in the newbie forum. i shift mine at 7500 with a plain jane solid flat tappet cam. i cant wait to get a solid roller. i belive the crossram 302's were around 420 horse :confused: but i may be corrected on this. and boy oh boy do they sound great when they are screamin!! whats great about these little motors is when the big blocks cant chase you down boy do they get mad. no disrespect to big block guys. if i had a 55 chevy gasser id have a t-rammed 427 for sure :D.........scooter
 
#12 ·
New age 302

I am currently assembling a new age 302 and intend on the following laundry list ..... I really want to see if I can get a sweet mix of fuel economy and performance in a 3400lb car on a shoestring.

89 genII roller block
Vortech 062 heads
L99 factory crank - Scat I 6.0
CC XFI 252 roller
0-deck with shaved 350 hyper pistons
TBI - start with 2bbl Vic JR or performer adapted

Do Vortech heads on a Gen II require different piston valve reliefs and or dome design to best accomodate their performance boosting ability?

I get what quench is but what is squish ... and does o-deck affect either negatively?
 
#13 · (Edited)
keithnh said:
I am currently assembling a new age 302 and intend on the following laundry list ..... I really want to see if I can get a sweet mix of fuel economy and performance in a 3400lb car on a shoestring.
89 genII roller block
Vortech 062 heads
L99 factory crank - Scat I 6.0
CC XFI 252 roller
0-deck with shaved 350 hyper pistons
TBI - start with 2bbl Vic JR or performer adapted
Do Vortech heads on a Gen II require different piston valve reliefs and or dome design to best accomodate their performance boosting ability?
I get what quench is but what is squish ... and does o-deck affect either negatively?
Gen II is an LT1, correct? I don't think the L31 heads will bolt right on and work. They were designed to work on a '96-'99 Gen I block (Vortec 5700 motor) that was in trucks and vans and will also bolt right up on any other Gen I block ('55-up).

I don't know about the squish/quench question. Never understood quench. Squish is the close-to-a-collision mating of the piston crown with the underside of the cylinder head with the piston at TDC. The closing up of this dimension as the piston comes up in the bore "squishes" air/fuel mixture out of the area, creating turbulence and blowing it over across the chamber toward the spark plug, homogenizing the mixture and eliminating dead areas that might not get lit off when the plug fires.

Under operating conditions, the clearance is all but used up by the crank bending a little, the rod stretching a little and the piston heating up and getting a little taller, so that a very close non-collision occurs each time the piston comes up in the bore.
On a small block Chevy, tightening up the squish to somewhere between 0.035" and 0.045" will go a long ways toward preventing detonation on pump gas. Experiments by David Vizard allowed him to use 0.026" before a kiss was encountered. I have no idea what components he used to do this, so don't try it until you do your own experimenting or call David and talk with him.
 
#14 ·
Chevrolet4x4s said:
Yea, in someone's dreams. Chevy's tuned race engines might have come close but the stock 302 that was available in the Z-28 from the factory.... no way.

Centerline
HotRodsAndHemis.com

"Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."
 
#15 ·
Im not a chevy afficianado yet so am not positive on nomenclature. I now think gen II is LTI starting in 1992 with reverse cooling. Gen I's were still being made maybe? My block is a 1989 pick-up block that I believe will be set up for or is roller cam. I figured that was a generational change but maybe not. I do believe vortec heads are a bolt-on to my block but you need the intake to match. I would not fool with trying to match an old-style. I will be fooling with a tbi adaptor to the vortec manifold I choose tho ... Not too many good reviews on tbi-vortec factory or edelbrock offering.

I believe quench is the sum of factors causing the fuel explosion to terminate quickly enough for the next cycle. In Pontiac heads it is mainly a wall in the combustion chamber that the flame front hits to stop it evenly I believe. I was going to be modifying some pistons for rotating assemblies with various BBC or SBC rods and after reading Jim Hand's book ssuggestion actually found someone who would cut in an angled down to wall in the piston top that would effectively "mate" with the wall in the chamber. (TRW has .125 to play with.) This is still on my board ... I have to get a couple runners done so I can play poncho.

I guess squish is the distance fom piston top to head, meaning closest flat area of the combustion chamber to closest piston top. I believe sbc has flat area like poncho behind quench wall and closer clearance squishes out that hiding area of mixture. I see that deck height rating for sbc is 9.025 which leaves the piston down bore between .030 and .050 ? I think poncho is 10.250 which leaves you at 0-deck. Is there a reason why chev and poncho would be different, one commonly zero decked and the other not? There is still a head gasket ... valves go deeper in one or the other?
 
#17 ·
Here is what I got off the internet:

quench [ kwench ] (past and past participle quenched, present participle quench�ing, 3rd person present singular quench�es)


transitive verb

Definition:

1. satisfy thirst: to satisfy a thirst by drinking something


2. extinguish fire: to put out a fire or light


3. suppress feeling: to suppress a feeling completely, especially enthusiasm or desire


4. cool metal: to cool hot metal by plunging it into cold water or other liquid


[ Old English ācwencan< Germanic]


quench�er noun
quench�less adjective



squish (skwsh)
v. squished, squish�ing, squish�es
v.tr.
To squeeze or crush together or into a flat mass; squash.
v.intr.
To emit the gurgling or sucking sound of soft mud being walked on.
n.
1. A squishing sound.
2. Slang A person regarded as weak and ineffective.

--------------------------------------------------------------------------------

[Probably alteration of squash.]

Well who is the English major??

Looks to me like we really need a better word. Neither really fits from a language point of view but we allow using words that sound about right to express an implied meaning that is mutually understood.

:rolleyes:
 
#18 ·
Looks like it's been answered, but here's a quote from wikipedia.org for 1967 Camaro 302:

"...Advertised power of this engine was listed at 290 hp (216 kW). This is an under-rated figure.[2] Chevrolet wanted to keep the horsepower rating at less than 1 hp per cubic inch, for various reasons (e.g. insurance and racing classes). The factory rating of 290 hp occurred at 5300 rpm, while actual peak for the high-revving 302 was closer to 360 hp (268 kW) (with the single four barrel carb) and 400 hp (298 kW) (with optional dual-four barrel carbs) at 6800-7000 rpm."
 
#19 ·
68NovaSS said:
Looks like it's been answered, but here's a quote from wikipedia.org for 1967 Camaro 302:

"...Advertised power of this engine was listed at 290 hp (216 kW). This is an under-rated figure.[2] Chevrolet wanted to keep the horsepower rating at less than 1 hp per cubic inch, for various reasons (e.g. insurance and racing classes). The factory rating of 290 hp occurred at 5300 rpm, while actual peak for the high-revving 302 was closer to 360 hp (268 kW) (with the single four barrel carb) and 400 hp (298 kW) (with optional dual-four barrel carbs) at 6800-7000 rpm."
Those are much more realistic figures. However, if I remember right the dual quad cross ram version was pretty temperamental on the street.
 
#20 ·
If. Factory spec dz302 made even the claimed 275hp I'd be impressed. People like to believe that a 3" stroke holds some magic voodoo that can make the sum greater than the total value of the parts. Look at what comprised the 302. This thong was built with the best GM had in the 60's but that still wasn't that great. The intake, cam, heads, exhaust, ignition, valvetrain, etc. sucked. Sure you could build one today with good headers, much improved heads (even if you retained the factory casting a valve job alone would pick up major power), much better ignition, MUCH better cam, better carb, hell even a better oil pump. It would appear stock but be about 100hp or more better.

I have never seen a dyno of a true factory spec 302, probably because people don't want to shatter the legend, even if it is nothing more than a myth.

The simple reason it felt so fast was the rear gears, the fact that you could rev it and make some noise only helped bolster that idea in people's minds.
 
#21 ·
keithnh said:
I am currently assembling a new age 302 and intend on the following laundry list ..... I really want to see if I can get a sweet mix of fuel economy and performance in a 3400lb car on a shoestring.

89 genII roller block
Vortech 062 heads
L99 factory crank - Scat I 6.0
CC XFI 252 roller
0-deck with shaved 350 hyper pistons
TBI - start with 2bbl Vic JR or performer adapted

Do Vortech heads on a Gen II require different piston valve reliefs and or dome design to best accomodate their performance boosting ability?

I get what quench is but what is squish ... and does o-deck affect either negatively?
Ayuh,... I ain't the sharpest tack in the box,...
But,...
How the 'ell does this mismash of parts, come anywhere Near 302 cubic inches of motor,..??

Not that I think it could even be assembled...
 
#23 ·
bondo said:
Ayuh,... I ain't the sharpest tack in the box,...
But,...
How the 'ell does this mismash of parts, come anywhere Near 302 cubic inches of motor,..??

Not that I think it could even be assembled...
That is a 302, and it could be assembled much like any other sbc, the only trick may be the headgasket- depending on compression height and deck height.

Vortec heads can be used on an lt1 engine but it takes a little bit of extra work. Google it. IMO a well ported set of lt1 heads would be a better alternative, it'd be much easier and can still produce great power.
 
#25 ·
I just wanted to throw this out . . . When the first Z28s came out, David E. Davis of Car and Driver took one on a road trip, and discussed his experiences in a column in the magazine. After reading his driving impressions and experiences, I made a trip down to my local Chevy dealer. Nothing came of the trip, but the article he put together left a very lasting impression. It's been over 40 years now, and I'd still like to read that column again.

Pat
 
#26 ·
Im no expert, semi-educated guessing is kinda fun tho

I would like to get a good mate on my head and piston choice. I will be going for 10.0 to 1 with iron vortecs or 10.75 to one with aluminum. I guess a flat top piston with or without correct valve reliefs ( according to clearance) makes most sense. I was trying to get all rotating elements so balance could be done by Mar 1. My crank is straight,10/10 with oil holes groomed and ready for nitriding. I like the slightly smaller valves and port flows of the iron vortec because I am trying to make a "High-Torque" motor with a smaller displacement (302) and will let the HP fall where it may. The longer rod (6.0) slows the piston speed as well as shoves the rod journal down straighter ... both torque increases. My cam choice is CC's Extreme(st) torque cam for fuel injection with lower duration and a lift @1.6 that Vortecs will just handle if worked. I found a Brodix dual plane intake I may get and hack up to make a TBI adaptor be the top portion instead of the 4-bbl mount. I will be shaving (on a Bridgeport) the compression height on std 350 pistons so their highest point is at .000 deck. (Is this .000 squish, or .000+ head gasket squish?) I see some sbc pistons in the 4.1xx range, how much is likely to be available to bore safely on my 89 P/U block? I was guessing .040 would be safe .060 iffy.