Chevy 302 build for my z32 w/th400

[Firion__13]

OK here we go. I have had my car on here since september 6th, 2007 and since the swap it has only gone about 50 miles. As long as its going to take me to save up and build this motor i'll be able to drive it alot more and hopefully work out any kinks. And for anyone new to hybrid swaps, there are always kinks, no matter how much you plan. ok first lets start with a history lesson. I have studied day and night even in my college classes . After i installed the turbo400 i realized i killed my top speed significantly, and having a near bone stock 350 in the car i couldn't get any more rpms out of it before things were going to start coming apart. my first thought was you need to build a 327, they were little screamers, but something was turning me off to them, and im not really sure. just wasn't the motor i was looking to build. And then i stumbled on the Chevy 302. Some of you may say? what? you mean ford 302 right? Nope the Chevy 302.

The chevy 302 made its debut in 1967 exclusively for the z28 camaro. It was build for SCCA racing and back then the cubic inch limit was 305. Ford was destroying any and all competition with the mustang. Meanwhile gm was hard at work building a mini monster that from the factory would turn 7000rpm and make 501hp as a race motor. from the factory they came with 290 hp @ 5800 rpm and 290 lb. ft of torque at 4200 rpm. they ran 11:1 compression from the factory with the famous double hump heads. This was a base motor. from there nearly every part and every trick in the book was done to squeeze some ponys out of this little screamer. Why did they scream? The run a 3.00 stroke. I have seen a few build ones on youtube and other places, and they never seem to dissapoint. 1969 would be the last year you could get a 302 in a z28, and would never be offered as a factory motor again.

 

Now as i am typing this my block is at the maching shop, getting boiled and cleaned, bored, and getting new cam bearrings, to begin this build. I honestly don't have a hp rating in mind i want to reach. not 500 i can tell you that. thats a little much even for me. Here is the thing. you can build a 302 out of a 350 block they share the 4.00 bore, and you can get medium journal cranks. There are few piston makers that make pistons for 302 applications pry due to the lack of people wanting to build them since they were only made for 4 years, racing production stopped in 1970. The pistons you can get have huge domes and a large compression height to make up for the short stroke, all 302s used 5.7 in. rods. This makes the pistons extremely heavy. most are well over 500 grams. to us race car motor guys thats a lot. But thank god there is another route. Now im pretty much building a race motor for weekend events. so longevity is not a huge issue . because it will not be drivin a huge ammount. With the stock 9.025 deck height, a 3.00 stroke, and 6.25 in. rods, and pistons with a 1.260 compression height and 11cc domes. Thats dialing in around 10.69:1 with 64cc head chambers. not too bad for pump gas. i could always get aluminum heads and mill them down to get a perfect 11:1 if i really wanted to squezze everything i could out of it. There is lots and lots i have not even touched on yet. but my wife is screaming at me to get off hybridz and come to bed. So I will continue this tomarrow. If you have any questions, or corrections to make, please feel free.

[dr_hunt]

Nice, the 302 works well with camel heads, particularly in the 2.02 version if they are massaged well. Opt for some decent I beam rods and it's reliable to 8000 rpm easily provided your valve train is stable. I had an arizona hard chrome steel crank and all the 302 stuff back in the days, ran real nice. Would love one in a z with a 5 speed!

 

Deck the block to zero, they are quench head motors and will work better with the proper quench height if your piston combo is for a 9.025 deck. You need quench to be less than .040 optimally.

Edited December 24, 2009 by dr_hunt

[Pyro]

never understand why people spend extra time and money building a small engine.

 

my 362 sbc with flat top, zero deck, compcam 292H, and 64cc dart heads revs to 7200 rpm all day long. The only reason it doesn't rev past 7200 is that is where the valves float.

 

the aftermarket is set up for bigger engines. (hence the big 64cc chambers)

 

Plus 302 and 327 pistons are long and heavy and expensive. The piston are about as long as the rods to make up for the short stroke. You are giving up 15% more torque and hp for no reason by building a 302 instead of a 350.

 

throw some good aftermarket 64cc heads on your 350 with a good set of valve springs with a cam in the 290 degree range. then your 350 with rev like crazy.

 

kind of funny, but a friend of mine did exactly this to a autozone 350 short block and ran it for 2 or 3 years. he drove it to work every day and raced it at the track every weekend and street raced during the week. furthermore, he sprayed a 200 shot of N02 on top of that. He had about a 20 to 30 lbs a week n02 habit. Plus a 3500 stall and 4.56 gears. The engine revved up to 7000 easily. Finally developed a knock (hammered bearing) but only after eating 30 lbs a week of n02 for over 2 years and revving to 7 grand 20 or 30 times a day (drove like a mad man).

[BRAAP]

Yes, if the only goal, regardless of any other factor whatsoever is out right performance, the rule of; “always build as much displacement as you can afford” is a sound foundation from which to start purchasing parts. Yes, a 400 CID small block can be built to rev to 8000 RPM same as 300 CID V-8 and the 400 being 33% larger in displacement, if comparably built will also make on the order of 33% more torque and overall power! If out right power is the goal, then the choice here is obvious.

 

Now keeping in mind that we are individuals, not everyone wants to follow the establishment and these same guys are willing to sacrifice all out power for the sake of building an engine that runs down a different beaten path, we should not chastise him for that or brow beat him for that.

 

If that person feels that his choice for less displacement via shorter stroke would more easily meet his intended performance goals based on facts taken out of context, (i.e. magazine engine builders). The argument of "shorter stroke revs higher which is more power", is a true statement, but that statement is often taken out of context and applied to mere mortal street builds where the longer stroke will rev just as high in a moderate build, just as Pyro accurately posted. In the realm of the street engines we play with, the larger displacement engines can and will rev just as high as the smaller engine therefore producing that much more power as well. When taken out of context, it becomes marketing hype that magazines preach as gospel and the consumer swallows, hook line and sinker. In reality, keeping the, "shorter stroke equal higher revs" in context, the shorter stroke being able to rev higher only becomes reality when you start getting into the upper racing echelons of engine performance that run in the 8000-11,000 RPM, i.e. NASCAR, Pro stock drag racing etc. Then educating the consumer that the reason for his choice of a short stroke was falsely contrived is productive, though doing so in a constructive manner is sometimes difficult.

 

Along those lines, I regularly hear the old timers that come to the shop get all strung out over the factory Corvette 327 as being the be-all-end-all of performance small blocks that Chevy ever produced! Better than any performance small block a shop could custom build! They'll claim, "It revved like no other small block, ran like no other, sounded like no other small block, yadda yadda"...they yammer on and on… For a factory offered engine of the era, that 327 was cool, but not a magical power plant by any stretch of the imagination that soo many believe! Its bore is 4”, same as the 302, and 350, as well as many other V-8's offered from Ford and Mopar! Its stroke is 3.25”. Nothing magical about the number or 3 1/4" worth of stroke. the 302 is a 3” stroke, the 350 is 3.48” stroke. Again, nothing magical about those particular stroke lengths that makes them "special" above and beyond other strokes available.

 

I am pretty sure it is the way Three twenty seven sounds as it rolls off the tongue when spoken has everything to do with its mystique and cult following. It has a masculine, proud undertone, a sound that many glum on to as being special. Say it out loud.. THREE TWENTY SEVEN... Feel it? Same as the Four Twenty Seven. Three fifty and Four Fifty Four just don't have that same ring when said a-loud. They sound more mundane, truck like. Subconsciously those engines become revered as low performance truck power plants based on the engine size/name sounds when said aloud even though they are actually higher output power plants when built similarly.

 

I digress…

 

Sooo… if a portion of the end users intended goals also includes building something less common and a sacrifice in over-all power output is acceptable, the 302 is a wonderful engine that will readily rev to 7000 RPM with stock rods (and ARP rod bolts) and cast pistons. In that light, build it!

Edited December 24, 2009 by BRAAP

[Firion__13]

Thank you paul, couldn't have said it better myself. And Pyro i totally understand what you are saying. I used to have an 86 camaro with a 406, and it was a monster. And it had way more power than i wanted. I didn't hate the motor for that. The whole reason i want to build a 302 is because i don't know how many times i have been to a car show. and if you see a SBC in your mind don't you automatically assume its a 350? Or if someone says they have some sort of GM project car how many times have you heard 350, or 400, 0r 327. Its not that i dislike these motors, its just when i am asked i want to have something they wouldn't expect. Kinda like swapping a SBC or SBf into a Z. I want something different, than the everyday built up 350. I chose the 302 because from the factory it was a screamer. Because it was exclusive to my favorite muscle car. And because it It was something that you just don't see or hear everyday.

Here let me show you what im talking about.

http://www.youtube.com/watch?v=9ajVMgVp4s8

Or of yout not much of a dyno guy here is a z28 with a 302 in action against cars it was built to fight it out with

The end is the best part.

Paul i would love to throw a t56 behind it. but for right now im gonna build the motor and see how it feels with the th400. A manual would be so much more fun though. The Z28s came with a muncie.

[BRAAP]

My current SBC project, (the single plane crank project), is a ridiculous project that from a budgetary and a performance standpoint makes little to no sense on many levels.

I am aware of the short comings my project is plagued with, yet my gift of stubbornenty, (yes that is a word, I just made it up...) is strong enough that I am still pursuing it for its "different" factor and for the self satisfaction of building something that far out in left field.

 

If the 302 is what you truly desire, then by all means, build it!

[HarrisonTX]

YESSS

 

Brother, you are speaking my language.

In 2003, i bought a 3.00 stroke crank. From there i decided to build a 302. Then i realized, i need a light car for this motor.

Six years later, and a couple stacks of cash here I am

 

I got the machine work done on the motor, and the rotating assembly is balanced as of last summer.

I'm deployed right now, and havnt had more than a 2 week vacation with the car in the last 5 years, but that hasnt stopped my from buying piles of parts.

The shitty part is, i cant tell you exactly what i have, i just plumb forgot the specs on the heads and pistons, and such.

 

283 crank (forged.. all of them were)

SCAT h beam rods

JE pistons (5.7 rod, fair dome on them, last set in the country supposedly)

AFR 210cc eliminators.. just to name the fun parts.

Im going to run a Team-G intake, and a solid roller cam. The cam is the only part i dont have, and dont even have a clue yet what to go with.

 

I got a tko500 last year.

 

In short, the motor is ready to be assembled, and i have just about a complete drivetrain. Now its just car prep.

My contract ends this summer, and i will be free to spend night after night, un-interrupted with my Z. It should be finished by August.

 

People will talk sooo much ♥♥♥♥ to you about building a 302.

Well, im not trying to be the fastest car in town, and im not trying to squeeze every single last bit of horse power out of my car.

Im also not trying to be like every other Joe, and build a 383.

 

i simply want a fun, quick little ride. This 302 will produce that, i guarantee it.

[Firion__13]

HarrisonTX, first i would like to thank you for what you are doing for our country. My buddy Joe Whitely is in afganistan right now but is normally stationed at fort hood. He Is big into OFF ROADING, and isn't much of a motor guy but he is getting there. Again Thank you for what you are doing. And Your motor sounds sweet. you gotta let me know how it turns out. Mine will pry take me over a year to build, cuz all the parts im going with are some of the best. My bottom end alone is around 2 grand and thats without berrings wrist pins main caps, and what not. im not really building a motor for the street. It will be a weekend warrior of sorts. Thanks for your support!

 

Paul i have been following that thred since you started it! I see you got your crank. I seriously spent like 5 min just stareing and drooling at the pics...my wife walks past and is like stop looking at your motor porn! haha. Its gonna be awesome. And who cares how rediculas of idea it is. Its a lot of fun to follow and learn just how much i, myself didn't know about 180* motors. I can't wait to see more.

[Firion__13]

Merry christmas hybrid z folk!

Look what my wife bought me for christmas!!! Wahoo

click the attachment

[jt1]

There's no doubt the 302's and 327's have a sort of legendary status that none of the other sbc displacements enjoy. I've got a large journal 302 on the engine stand right now, it's sort of stalled till I get my 358 running. It will have a set of period correct 292 angle plug heads, and I know it won't make as much power as my 358, but hopefully the cool and fun factors will more than make up for it.

 

I fully agree with Braap; Build what you want, it's your car and your money.

 

jt

[Firion__13]

My friends dad races dirt track late model, and he has a 358 in his car. But its like an all out race motor. He and his sponsers Have 12grand just in the bottom end. I i think thats pretty ridiculous. He only races at 3 tracks in the state. seems like a lot of money to me for not racing some more presigious places, but hey its not my money. lol. I know the block was quite a bit its a DART block.

 

This is what i got figured out so far for bottom end parts Eagle crank, eagle h beams 6.250, and JE SRP Professional pistions with a 1.260. with a 3.00 inch stroke that will give me 0.015 inch of clearance below deck. I have been involved mainly in the assembly of race motors not so much the piecing of them together. I have 3 friends that race dirt circle track, and i have been on their pit crew off and on since i was about 15. Every motor i have ever built with them we have always had a minimum of .015 inch below deck for the expansion under hard rpm loads. Atleast thats what i was always told. Is this wrong? we have never broken anthing by doing this? What do you mean by this DR. HUNT?

[bleakdragonmage]

What are your power goals...

 

And why did you choose the TH400 if you dont mind me asking...

[dr_hunt]

My friends dad races dirt track late model, and he has a 358 in his car. But its like an all out race motor. He and his sponsers Have 12grand just in the bottom end. I i think thats pretty ridiculous. He only races at 3 tracks in the state. seems like a lot of money to me for not racing some more presigious places, but hey its not my money. lol. I know the block was quite a bit its a DART block.

 

This is what i got figured out so far for bottom end parts Eagle crank, eagle h beams 6.250, and JE SRP Professional pistions with a 1.260. with a 3.00 inch stroke that will give me 0.015 inch of clearance below deck. I have been involved mainly in the assembly of race motors not so much the piecing of them together. I have 3 friends that race dirt circle track, and i have been on their pit crew off and on since i was about 15. Every motor i have ever built with them we have always had a minimum of .015 inch below deck for the expansion under hard rpm loads. Atleast thats what i was always told. Is this wrong? we have never broken anthing by doing this? What do you mean by this DR. HUNT?

 

Not really, the quench head engines like the sbc make more power if the quench is the designed .040 or less. With the head gasket at a compressed .038 you need a zero deck to achieve quench and receive the gains of the intended design. In blown alky motors with aluminum rods you can have pistons down the hole at tdc as the rods grow when hot more than steel rods and stretch to some degree with use, but I still deck the block to zero. Steel rods stretch very little under rpm, but probably more so due to heat. Like rings do on the pistons, and the reason why when running hypereutectics that you have to open up the top ring gap to .027 instead of .017 for instance. The rings grow more with more heat and you have to open up the gap to accomodate the growth or it'll pull the top of the piston off.

[Firion__13]

Ohhhh. i see what your saying now. thank you for your insite.

[Firion__13]

Bleakdragonmage i chose the th400 for its duribility, cheapness, and wide range of parts. The plan someday is to have a t56 in it. but for right now it has the th400 my wife just got me a pro ratchet from b&m and im looking to get a fully manual reverse styled valve body for it. And as far as power goals id be happy with something over 350hp maybe 400... pry 400 which with parts im using can be easliy achieved. I spoke to a guy the other day that bought a z28 for his first car and he told me they use to do every small mod they could to these motor in SCCA. Polishing the rod and the exterior of the crank so they would shed oil weight quickly, de-bur and polish the oil valley even. I have a book that mentions some of this but it really only talked about de-burring the oil valley not polishing it.

My redline i would like to be 8k, which is the redline in the book i have of the 501hp SCCA motor build they do.

For anyone wondering about the book it is called Musclecar & hi-po Engines Chevy 302 & 327. There is a lot of good information in this book, on how to get easy hp out of a 302, what cams work best, and heads too.

[dr_hunt]

Yup, been on that road before, spent days polishing the lifter valley, rod beams, etc. But these days you can buy lightweight aftermarket rods and lightweight pistons, get it all balanced and run some sort of solid lifter cam. Duntov was a fan of low lift and lots of duration back in the day, but I think now technology has provided many more profiles that will make bette power when matched with the great heads we have available now. What heads you going to run?

[Firion__13]

Thinkin about dart 230s. for now pry just double humps cuz i already have a set. they just need rebuilt.

[bleakdragonmage]

If your goal is only going to be 350-400ish, i would go with a TH350. It will hold the power, is slightly smaller, and is less parasidic with the drivetrain loss.

[Firion__13]

i was considering that... but i already have the th400, and its already mounted up in the car.

[bleakdragonmage]

ah. thats what i figured. Well, have fun.