Little Mouse

No I'm not trying to convince anyone to build a 302. So the 302 had the common 2.02 intake valve for sure good amount of valve area for the cubic inch for a two valve antique lol. So now you build a 540 or even a 632 what intake valve size do you need to be equal to the 302 and how heavy is it lol. It's sad that all three manufacturers of big blocks did not develop a good 4 valve head for them.

TCracingCA

I like rpms, so I focus on rod angle, as 2.02 valves and 4 inch bores are pretty reliable and capable. Why throw away stroke in a Small block, if you have deck still!

I can ET as quick as any big block short of a full slick race car, because the rear tires can only support yeah so much torque and power! I rather push out what can be handled by the rear tires, thru a small block!

We will always have two camps on engine choice (small or big block)!

Jebbysan

The valve size is only part of the equation. Early 2.02/1.60 heads flowed not much more than their 1.94/1.50 counterparts....the heads were crap, this is the reason.
The bowl area before the valve seat is plain awful.....opening it up .060 did very little.
Now when you work with a real port.....valve size becomes more of the equation......but not as much as you would think.
A 632 generally has a 2.400 valve if running a Big Chief head.......so no....it is not proportional.
The top builders pay less attention to valve size and more attention to the port and area under the seat.

Jebby

cv67

x2 on factory seats they are awful. Ever seen an L98 or even LT1 heads? good gawd youd have to replace the seat to even think about a blend or there wouldnt be any seat left where it hit the bowl

stingr69

There are no small block heads that can flow more than the big block heads do so....

There is no replacement for displacement. RPM is a sub-optimal replacement for displacement. RPM works where the rules require it, but otherwise... we build bigger.

suprspooky

I agree but, there are few cooler looking top sides than a 302 sbc cross ram

cv67

Vortecs come close to some big block heads. Youre right though in general BBs rule the streets always have..

7t9l82

Some crappy big block heads maybe.
Unschrouding the valve in a small block must be done if you make the valve larger. Otherwise it's a waste making bore size critical. There is always something.

427Hotrod

Gotta remember that BBC valve angle helps get valve away from cylinder wall when it opens....but you're right....valve limitations hold BBC back. Often you'll see exhaust valve size reduced to allow for a bigger intake.

JIM

leigh1322

You're right, the block shrouds the valves too. Vizard quoted that opening up the bore size unshrouds the valves and adds more horsepower than you would think for the cu. in. difference.
Adding cubic inches with stroke may adds less horsepower than you would think, and more torque.than expected, for the cu. in. increase.

7t9l82

If you really want to see something to blow your mind, take a look at the first version of the Plymouth small block pre 66. Angled valves and Chambers are similar to the big Chevy, Cleveland Ford an 460 Ford. Not as large but the basic architecture. Chrysler wanted a cheap hemi.they have come a long way though

stingr69

Yes - stroke adds cubic inches which adds HP but the torqe below the peak is the real draw. The torque curve tilts to the lower RPM range and makes for a more versatile rpm range. The HP increase is mostly just from the cubes.

Big2Bird

I agree. The car is much more balanced with a SBC, and with today's gizmos, you can have the same HP as the old iron pigs.

If your into straight line, have at it.

Little Mouse

Yes the original sbc heads were not great. But my real point is in this more modern world of now you can buy better sbc heads and of course bbc. But the undersize valves in bbc problem is now far worse with say an easy to build 540 today. Yes the 4 degree can't of the bbc was some help but then the idiots made things worse with a 26 degree intake valve angle compared to sbc 23. Even a baby bbc today of 454 with factory heads at 2.19 int. compared to 302s 2.02 that's a joke. Yes I'm aware you can get some bigger valves in the new aftermarket world but the of cu. To valve size has just got much worse. It was always said that in the old days of smaller sbc even if you ported the heads the choke point was the damn pushrod pinch. But even back then the choke point for bbc was the valves.

Little Mouse

The Cleveland sbc Ford has a really nice intake valve angle and a cant to it. The first year of there 302 they put a 2.25 intake valve in it then next year changed it to 2.19. On bigger cube SBC fords they worked and a god send disign in aftermarket Ford heads they can use today. Then there is the ford design LS they have been putting in newer corvettes today. Lol

Little Mouse

I learned the unsrouding thing mid 70s. Me and a friend shared the cost on a double size storage unit. I kept my 66 in it and he had a 69 Camaro that he drag raced some. I bought the 66 in 75 the original 427/425 hp and trans was gone. I worked at parts warehouse big machine shop there I could get blocks cranks anything I wanted for five dollar shop forman liked me. So a large journal 327 crankshaft showed up I grabbed it and 4 bolt block and put 12.5 pistons in it ended up 331cu. It ran ok the vette still had the original 4.11 rear. But the power mad scientist in me kept it short time , I built a two bolt main 396 for it. So me and this friend of mine I got a 400 block. He used some trw bearing spacers and we put the 327 crank in it ended up I think 348 cu. It ran better then any of the other 350s we had built. The bore size you could tell it made a difference.

Krystal

Why not the best of both worlds?

427 inch small blocks are pretty common builds today.

At this price it's not a cheapo option but still no more than a crate big block will set you back and honestly a lot less than the hot Big Blocks.

https://www.summitracing.com/parts/m...SABEgIr0PD_BwE

Under NO CIRCUMSTANCES would I ever consider a Chevy Big Block for a C3 today, short of a numbers matching museum quality car restoration.

It's just not required anymore.

If you're budget is big enough.......and you really want wild:

Nelson Racing engines can give any one the 302 "appearance" and more power than you'll ever really need on the street.

cv67

Been to their shop a few times they put together some outrageous stuff. not for shallow pockets!

Corvettedave02

I’m biased because I already did this but the big cube small block route with modern heads is a nice option because externally the engine is the same and even lighter than an original 302,327,350 with the aluminum heads intake etc. aftermarket blocks are heavier too (60-90 lbs?) but probably a net loss in weight. I think my big mistake was getting the 210 cc runners instead of the ‘then’ available 227 cc runners. Now AFR has 240 cc intake runners on their 23 degree heads but I checked and they are different castings to the 240s.

The valve size doesn’t seem to change much but the flow numbers do! I’m no expert but the Flow and velocity of the air charge matter more than the intake valve size right? With older tech the bigger valves helped to get you there, but with newer head design it doesn’t seem to be that important.

im amazed at the sb 23* 434 pump gas motors that out out 700 hp. Those look like a 302, lol. Shafitoff racing even has a pump gas 440 sbc with 800 hp. SB2 heads thou so the headers would be a pita. My pump gas 540 Hemi in my cuda only puts out 800 Hp and has 100 more ci!

At least with a street motor. You could put some 302 badging on a sb434 if you wanted right?

Little Mouse

If I were able to go aftermarket 427 sbc would have to use darts iron eagle or would never do it. The spread pan rails and more important the raised cam location with the ability to use a big say 55 mm cam. Otherwise would simply build a bbc.