Comparing a 383 to a 434, both using a 6" rod and all 4340 assembly, using the same AFR 227 head, will I gain MUCH more with the 434?


Here is my problem. I can buy an early model 350 4 bolt to build a 383 with, but I'm not buying an early model 400 instead I would use a Motown block. So the price to build a 434 is probably 2k more...

 

You will gain more expense with the 434. While big inch small blocks are cool, running that large a stroke is hard on cylinder walls. Also with a 434, I believe you will need to run a custom base circle cam for rod clearance (correct me if i am wrong).

Its your choice, but I think with the extra money you will spend building a 434, you could easily make a 383 perform just as well (solid roller cam, shaft mount rockers, etc) for less $$$.

 

If you're gonna use the same components on both motors, the HP output will be very similar, probably within 20-25 horse. The torque will be higher on 434 by about 50 ft/lbs.

 

You need to run a small base circle cam in the 434. For sure. but it doesnt add expense to the cam, unless the cam you were gonna use was an off the shelf grind to begin with.

Im think the cyl sidewall loading is more affected by rod lenght than stroke, in which case both the 383 and 434 will be similiar.

I am partial to the 434 btw. There is no substitute for cubic inches.

 

IMHO, if I were to buy a Motown block, I wouldn't overbore it. 4.125" is plenty big bore. An extra 6cid wouldn't be worth it. Besides, then you could say you have a "427" eventhough it's actually 428cid

And with the cylinder walls of the Motown block being so thick, I wouldn't worry much about the longer stroke hurting anything. Heck, Mitchell offers a "427" crate motor AND a 454cid crate motor that both use that block and the same 4" stroke. The extra cid comes from the cylidner walls. They both have 2 year warranties too

 

It depends on how you build it honestly.....

if you put the same cam in both motors and used the same AFR 227 heads, the 427 would make more

to build a 427 right i'd use a tall deck motown block so that i could run a longer rod and i'd also be looking into a better set of heads than any AFRs honestly....probably some 18* heads

put in a decent solid roller and you'll easily make over 700hp on motor

 

Can you give me a part number and who makes those?

Thanks...

 

The way you asked the question doesn't really make a lot of sense to me. You need bigger heads, different cam, different exhaust, etc. to get the best out of the two combos. If you used the same parts, for whatever reason, there would be no point in buying that expensive Motown block, IMHO. If you optimzed the two, then it's purely a matter of budget because the "434" would roast the 383. It's gonna have at least 15% more hp and torque.

I agree that it would be silly to max out the bore on that expensive block. That is not a throwaway item, in my garage anyway. Give yourself enough cylinder wall left to rebuild it a few times if you go with the Motown.

Rich Krause

 

If you make the choice to run big cubic inch with aftermarket block and look to find a head that flows max CFM check out the new Little Chiefs from Dart(Assuming your looking to make max power?).

So before you decide to purchase the AFR's call Dart cylinder heads. A buddy of mine that owns a parts warehouse showed me inforamtion about a new released head from Dart for sbc. The cylinder head is called the Little Chief which supposedly right out of the box is supposed to flow over 400cfm! This is a 11 degree head. If you have ever heard of the Big Chief heads Dart makes for BBC then this is supposedly the version for the small block Chevy.

All thought the head my not be out just yet so give Dart a call to see if they are out. Talk has it that these are going to be the cylinder heads to have if your looking for max power and cylinder head that will flow the highest cfm! I'd beat the price will be nice and cheap. LOL!

See Ya,

 

Rich, sorry for the confusion. You answered my question though, that the 434 is worth at least 15% more power. I'm just afraid a 383 might not be enough even with a huge cam/head combo. My goal is to have a street driven high 10 second car (3400 lbs) that runs on pump gas. But at the same time I don't want the motor to have to work to its max to produce those times. So, would the 434 do this easier or is a 383 built right enough to do it with ease?

Thanks for all the input by the way....

 

10s NA i assume? go 434. 18 degree heads.

you will probably end up closer to 9s, on pump gas .. if its built well

 

Oh, it'll be built well... trust me

9s is a little insane, high 10s is my goal...So 383 it is??

 

We are talking about projects that differ by an order of magnitude as far as costs go. A stock block 383 with 23 degree heads at one end and an aftermarket based big cube small block with 18 or 15 degree heads at the other extreme.

Do you need an exotic solution to get into the 10's with a streetable combo? How much does your car weigh? If it's a pig like mine (~3,900lbs), there would no way to get into the 10's with a streetable 383 with 23 degree heads. A 434 would be closer, but I still think it would be a tall order. OTOH, if you car is a lot lighter a nice conventional 23 degree 383 might be fine. It's gonna take ~525 rwhp to get into the 10.9 range for a 3,500lb car (plus driver). This is just barely doable. Add 700lbs (my car plus driver) and you need another 100hp, which ain't gonna happen with a conventional head NA small block.

A more logical approach is to decide on a budget and ask "how much NA performance can I get for my dollar" and let the numbers fall where they may.

Rich Krause

 

high 10s.. everybody runs that. hell, there are a handful of stock bottom end/head/cam LS1s running mid 10s.

I would go 434+18degree heads

 

Amen.

Speed costs money...how fast, etc.