So here is a question then. I have been looking at different options for a new motor in my 74 and was going down the 383 road or larger SBC.

Since the intent is street and open RR days or maybe Time attack next year is a BBC the right way to go? In an article I read about the 74 test drives they had said most prefered the SBC version due to the better handling of the car.

What kind of weight difference are we talking and what impact on RR would it have?

 

Well in all things when loosing weight sometimes costs money lol.

If you replace the heads and intake with Aluminum on a Big Block you would be right at the same weight as a factory Small Block. But here is the kicker if you replace the heads and intake on a Small Block then it weighs less.

All one has to do is do a search on weights and there components to come up with the numbers.

And Of Course Factory Small Block against Factory Big Block in handling tests did worse due to the increased couple of hundred pounds or so on the front in which will cause front end dive in both breaking and cornering.

But here is where I would start. You have to decide for yourself what you really Need to accomplish what you are after. Then ask some questions and create a plan to get there. Doing this I think would make you the most happy for the money you spend.

I am sorry if some of this discussion has led you to believe that some people do not like the Small Block as this is not true at all. The Small Block Chevy is a very good Engine. You can just reach a point when you just run out of room to make more HP and TQ with a Small Block without spending a great deal of money. When a Big Block can easily get those numbers say in the 550- 600 HP range without much trouble and then beyond with a stout lower end and a better breathing head arrangement.

But for an everyday Street Car with occasional hard usage and with low costs and yet good power to be made for the money expended and if the car is already equipped with a Small Block Chevy I would go with the 383 CI Small Block. That way everything fits and is easy to work on. I mean like things that are done often like oh Changing Plugs lol. Easy on a Small Block Not so easy on a Big Block lol. Heck I had more room in a Vega with a Big Block than a Factory Corvette with a Big Block lol.

 

Thanks for the ideas. That is kind of where my head was at but some of this discussion seemed interesting enough to ask the question.

 

For those with unlimited funds, you can build an all aluminum big block. Weight problem solved. For most of us, that is way out of reach. I used a small block because the car was a small block car, and I have a bunch of small block parts. Would I like to go big block, sure, but it is not in the budget. I have zero big block parts anymore.

 

You should Always Ask Questions.

 

SB2.2
Big Block power small block package

Big wallet req'd though

 

The notion that having a BBC under the hood will necessarily destroy the C3's handling is a massive exaggeration promoted by those who just don't understand vehicle dynamics and chassis tuning all that well.

An iron BBC with aluminum heads, intake and water pump only weighs ~600# (that's 75# less than with iron heads), while an L82 SBC comes in at ~525# (which is more than an all-alum BBC).

Given that moderate amount of extra weight sits BEHIND (rather than above) the front axle, it's really not all that difficult to tune a BB C3 for improved drivability and handling, even with iron heads. It has admittedly taken a bit of sorting to get my BB '78 to the state of tune it is in, but I'd wager very few SB C3's can out class my BB '78 in the twisty bits (except that it's currently apart for more mods).

FWIW, I too am afflicted with shipwright's desease, evidenced by having completely blown my 427 redux budget.

.

 

If you have money why not off the shelf 570 cfm heads for the BBC no telling what pro stock is wringing out of them. You just can't make comparisons to the two engines. Both are very expensive options very few will take.

 

street torque or race track hp.look at the power made with modified ls1 ,small bore and 500rwhp.I like r/s ratios of 1.6 or better ,good for endurance or high rpms .but for a average Joe going cruising a 1.5 R/S ratio works.

 

I don't have anything against smallblocks.I did a *bolt together* deal for Auto Enthusiast magazine a couple of years ago with a Dart SHP 400" shortblock and inexpensive SHP 200cc heads. Nothing really trick at all. The crazy thing made 555HP with a single plane intake and a 750 Holley. 540 HP with a dual plane. On pump gas....and it's still running great in Forum member Devildog's '61 Vette.

With the parts available today..it's just not that hard to make incredible power. That engine could make 600+ easily with some killer heads.

JIM

 

Is there an opinion at all that a higher rod to stroke ratio is at all helping, (or would hurt), a "big bore short stroke setup ?

I would care to hear Mr. Cstraub's opinion on this matter also, (and all others too).

 

theres advantages and disadvantages to both. for just a short sprint down a quarter mile, would rather have a shorter rod within reason. if you were going to keep things at high rpms for longer periods of time, would rather have long rods.

in the old nascar days of the hemi and bbc trying to compete the hemi had more power because of its heads, it also had several big advantages in durability. a shaft system no cheap *** mickey mouse club ball studs, 6.80 long rods with 1/2 rod bolts for less side loading on the block, the block came down surounded the crankshaft. This was all well and good in nascar that the engine was meant for in 7600 rpm engines of that nascar time period.. In drag racing where long term durability means not much for winning the heavy long rods and big heavy domed pistons to fill up its 170cc chamber limited it in rpm it could turn. 409 chevys could have been a real rever with there 3.50 stroke but they turned very low revs because of the real heavy pistons.

When gm originally designed the sbc it was and still is a nice compact in size engine. With its 5.70 rod it had a nice 1.92 rod ratio with its 3.0 stroke. It kept getting stroked for extra size without ever having a new block made with a taller deck.

 

AWWWWWWWWWWWWW Yes the 265 CI and they can be built to be real SCREAMERS . I know someone that still runs a 265 CI in a 55 Chevy for 1/8th Mile running 5.14 Gears and turns that little Engine to 9500 RPM. .

And the Old 427 Hemi there weak link was the Rods. Till people started Boxing them which helped a great deal but it also increased the Bob Weight.

 

only knew one person owner of razorback transmission that raced a hemi, always chasing down buddy bennet in his 292 e-modified 65corvette and he got the job done most of time even though buddy held the e-mod record for a short time, just an electrician working in his two car garage. Hemi rods were plenty strong as is, i watched him narrow a dana 60 in his trans shop. Only really junk rods i remember were in pontiacs. bennet told me he had 6.17 in his 69 camaro with the 4 speed then when he bought the 65 vette put in a doug nash five speed getting rid of his muncie coming apart problems lol he went to 5.57.

 

I have been very pleased with my big bore/short stroke 388, 4.125/3.625/6.0 inch rods. 11.2:1 compression on 92 octane.
I had a hard time with traction with my old 355 so I knew I could give up some CI's and torque that the larger motors offer. I have a crazy strong mid/upper range that really wakes up when the go pedal is mashed. Have a friend that a gave a ride to and he was all giggly afterwards saying he had never been in a car that can't just be floored and that can use the throttle to help steer.
Enjoy the build process that's almost as much fun

 

Better the heads the shorter the rod....thats another conversation and for street guy not needed.

 

Well, here's one: Smokey Yunick always held that higher R/S ratios are beneficial in engines meant to live long and prosper at higher RPMs, B/S ratio aside. Yes, there's both theory and evidence (including my own previous long-rod experience) to back his opinion up. Not saying there are no potential benefits to lower R/S ratios in certain other types of builds, but for my current purposes I'm sticking with Smokey on this one.

 

Always loved short stroke motors but after getting a feel for motors WITH stroke that can pull rpm Im a convert for sure.
We dont expect them to last 100k mi anyways who cares.

 

yunick did mostly long roundy round durabilty racing. They know today and yunick probably knew it to, that shorter rods work better with big runner heads and bigger cross section intake runners. Its the other way round for longer rods. What 427hotrod said is true about the shorter rod. the shorter rod jerks things away from top dead center quicker allowing bigger runners to be used.

JMO in a street car with reasonable size runner head, reasonable runner intake, i would rather lean torward a longer rod. its a longevity build less side loading on the rings and cylinders. if i ever built anything just for a short sprint " all the time drag racing " i would rather have the shorter rod with its quicker pull on the intake runners.

Cstraub69 could elaborate on what needs to be done on the camshaft for different rod lengths.

I still want to build a 302 even if it is crazy.

 

What's important imo is that port velocity is limited to sonic speed. Once airspeed hits sonic, it won't flow air in any faster. Basically your engine runs out of air at that point.

That point is different depending on the amount of air it inhales, and the piston speed.

So, as a shorter rod, long stroke moves the piston faster and moves more air, it also limits the amount of rpm's an engine can reach, since you run into sonic airspeed. A longer rod/short stroke moves that point upward.

This is of course with the same heads. If you open up runners and the resistance to air speed is less, then you could reach the same top engine speed with that bigger engine, BUT... as you increase your runner, your low end will suffer just as much as mounting a too large runner head on an engine does because air speed gets lower at low rpm.

So, what is ideal ?

IMO (!) if you stay at the same top end speed, but you can pull more rpm's with that short stroke motor, use a shorter rear axle, you'll get the same low rpm wheel torque (which is what makes the car move) and you get in the high speed a lot faster....

If you mount a short rear end with a long stroke motor it will run not as fast (lower top end)...

AND the long rod, short rod has another advantage : minimized dragresistance and lower side forces working on the piston ATDC.