Small Block or Big Block Chevy Swap

[foodstamp]

i hered that small block would be good, a big block can crack a chassis becouse the high torque, and you can get the same amount of power out of a 350 as you can a 454.....and 350s i hered are cheaper......ide chose a 350

[Barrman]

Foodstamp,
I normally let statements like yours just be because everyone has their own opinion. You are the 15 year old, right? I figured you should be made aware of a few things.

I personally love SBC engines. They fit just about anything, they are light and parts are cheaper for them than any other engine made. But, except for the 2000 and newer Gen III electronic engines and a 383 stroker conversion, most SBC engines develop their torque at rpms above 3000 rpm. With many making peak torque at 4500+ rpms.

BBC engines for the most part and just about all big block engines for that matter develop torque at lower rpms. A 1970 Buick 455 was listed as having 510 ft pounds at 2800 rpm by the factory. I used to have a '70 Riviera. That kind of torque is like a drug. You become addicted and can never get enough.

Sure, you can buy or build a SBC that puts out those kind of numbers. But, it will cost more than a big block with the same output. What kind of big block you use matters too. I have a 1966 396 in my M715. It is more of a screamer compared to the 454's, so I have to have more rpm than them to make the same torque. But, I was flat towing a 13000 pound M35 last month and just kept it right in the middle of my torqueband. 2200-3500. I had no trouble merging with traffic beside the fact that I couldn't see backwards or sideways. I don't think a small block with the same money invested could have done near as well. Same situation while I pulled a M715 on my trailer behind my M715 for 500 miles back in October. A small block could have done it, but not as well or as easily.

That leads us to diesel engines. A modern turbo diesel truck is the best thing since sliced bread in my opinion. As good as a big block is over a small block, a diesel is the same over the big blocks. They get better milage and last longer too. But, the cost of admission to the diesel side of the force is higher.

It all depends on what you want the truck to do and how much you want to spend. Oh, I do not recall any reports of M715 frames ever cracking or warping because of engine power issues. Power steering mounts breaking off because of too big tires, yes. But not too much power induced problems.

[tacoma]

^^ what Tim said, with some extras

1. Small blocks can be built to have big block power, but the torque peak will always be higher. That's just physics. In trucks, the lower rpm the torque kicks in, the better.

2. "that kind of torque is like a drug." Hell yes it is!!!

3. Most of our vehicles will never see the high side of 4000rpms, so spending lots of money on a motor that doesn't kick in below that is not cost-effective. Again, small blocks like to rev a lot more than big-blocks. 454's can be built torquey for very little money (relatively).

4. I have a big Suburban with a 350, and a bigger K30 dually crew cab with a 454. The crew cab lost .75mpg and zero speed driving into a headwind with 5k loaded up. The Burb requires many RPM's to get up hills. The difference is torque.

5. Diesels absolutely ROCK, but they are heavy and expensive. Really, really heavy. For that reason, I absolutely love the 6.2/6.5 for the M715-- they can rev a little higher, are a little lighter than the other options, they fit, they're cheap, and they're easy. But they don't make huge power like the other ones.



and I've never heard of any cracked frames either.

[dave]

Im runnin a 350 in my 725 and its strong but needs overdrive to drive on the highway plus the 205 to keep it running cooler. I can turn the boggers over pretty easy but Ive hurt the engine reving it to around 6000 on a rebuild that someone else did so now Im going to tear it out and go and rebuild a later 350 with efi and the nv 4500 and the 205 and tow my 715 around with it.
One 715 is getting a 635 cid chevy, nv4500 and 205 plus rockwells just for offroading use only.
Tac, my 725 hits around 6000 alot and its held together pretty godd all but the engine which has about 3500 milkes or less on it. cant drive it without turning it tight. LOL!

[Channing]

I am looking for some one who has done the BBC to 3053A mate with none cast iron parts for high rpm use

[randyscycle]

I am looking for some one who has done the BBC to 3053A mate with none cast iron parts for high rpm use

I can tell you in my experience with Big Block Chevys, that to turn lots of RPM, they take lots of $$$.

A 454 is lazy and long stroking, so it isn't a big RPM turner.

A 396 is a short stroker and a small bore, so its a bit faster revving, but lower in the torque output area.

A 427 is a good choice for RPM and torque, as it combines the 396 stroke and the 454 bore.

A stock hydraulic lifter 396 will peak out at about 6,000 RPM give or take. A solid lifter version will go for about 7,000 for short stints.

They can and do suffer from oiling problems at high RPM in stock form as they tend to pump most of the oil to the top in those situations without a bigger pan and pickup assembly.

[Channing]

Sorry I was thinking in my tunnel vision I was asking for help seting up a steel flywheel and SFI bell housing between a BBC and a 3053A thanks

[gimpyrobb]

Probably won't happen, the input splines on the 3035a are too large for that small of a clutch.

[wrecker]

If the big block is running, run it. The swap to the small block later would be very simple if you ever decided to. Biggest obstacle would be changing the exhaust. Maybe a different starter and engine accessory brackets too. Not a super big deal. Everything else I can think of would be a direct swap out.