Is it big or small?

[Ronald F.]

Please forgive my ...lack of knowledge...but as I'm hearing GM label the C7 engine a small block, I'm wondering exactly what is the criterion used in the industry to classify an engine as a big vs. small block. I know in the Camaro world the 1969 350ci engine was a small block and the 396ci engine was a big block. Is it just a certain cylinder volume cutoff, or what?

Thanks!

[John H.]

Re: Is it big or small?

Please forgive my ...lack of knowledge...but as I'm hearing GM label the C7 engine a small block, I'm wondering exactly what is the criterion used in the industry to classify an engine as a big vs. small block. I know in the Camaro world the 1969 350ci engine was a small block and the 396ci engine was a big block. Is it just a certain cylinder volume cutoff, or what?

Thanks!

Probably the 4.4" bore centers - that's been a constant since the first 265 V-8 in 1955; big-blocks are 4.84".

[Jack H.]

Re: Is it big or small?

Then we have the case of the 348 and it's big uncle the 409 which some classify both ways...

[Mike E.]

Re: Is it big or small?

Then we have the case of the 348 and it's big uncle the 409 which some classify both ways...

Those sure had odd shaped heads. The first time I saw a pair of those was on a dump truck.




Mike

[Terry M.]

Re: Is it big or small?

Mike,
The folks at Tonawanda -- at least the old ones, now deceased or retired -- Took great offense at any connection between the W-block and trucks.

BTW My LS7 (at nearly 427 CID) is officially a small block. Go figure!

[Mike E.]

Re: Is it big or small?

Mike,
The folks at Tonawanda -- at least the old ones, now deceased or retired -- Took great offense at any connection between the W-block and trucks.

My mistake, I could have sworn that's where I saw one.

Mike

[Larry E.]

Re: Is it big or small?

Probably the 4.4" bore centers - that's been a constant since the first 265 V-8 in 1955; big-blocks are 4.84".

OK; I throw you another curve ball. Does not the Chevy Nascar Engine(ROX Engine) also called a "small block" have 4.5 " center to center bores?

Correct me if I'm wrong. Larry

[Terry R.]

Re: Is it big or small?

The oddest thing with a 348/409 was the combustion chamber.

[Joe L.]

Re: Is it big or small?

My mistake, I could have sworn that's where I saw one.

Mike

Mike and Terry-----

The "W" block, including the 409, was used in trucks. In fact, MD and HD trucks of the early 60's are one of the last remaining sources for original 409 blocks.

[Joe L.]

Re: Is it big or small?

Then we have the case of the 348 and it's big uncle the 409 which some classify both ways...

Jack-----


There was some parts commonality between the 348/409 and small blocks (things like harmonic balancers and fuel pumps). However, GM always considered the 348/409 to be a big block series engine. In fact, being classified as the Mark I, it was the ORIGINAL big block. The 409 had the largest bore size of any PRODUCTION V-8 ever used in a Chevrolet in modern times. Only one other GM PRODUCTION engine of the period ever even equaled its bore size.

[Duke W.]

Re: Is it big or small?

OK; I throw you another curve ball. Does not the Chevy Nascar Engine(ROX Engine) also called a "small block" have 4.5 " center to center bores?

Correct me if I'm wrong. Larry

I believe that's correct. Last time I heard it was called R07, and it is a unique engine for NASCAR that doesn't share any parts with any past or present small blocks.

In an attempt to get more revs, which means more power, Chrysler cam up with a 4.125" x (about) 3.25" (can you say 327) configuration, and every one else had to follow. In order to prevent this from escalating, NASCAR limited engine bore to this value.

So in order to get this bore without siamizing the cylinders, Chevrolet had to increase the bore center spacing, but as I said above, even though this engine is about the same physical size and displacement as the classic 350, it shares nothing with any generation production small block.

That and the tube frame architecture is why they are no longer "stock cars".

Duke

[Joe L.]

Re: Is it big or small?

I believe that's correct. Last time I heard it was called R07, and it is a unique engine for NASCAR that doesn't share any parts with any past or present small blocks.

In an attempt to get more revs, which means more power, Chrysler cam up with a 4.125" x (about) 3.25" (can you say 327) configuration, and every one else had to follow. In order to prevent this from escalating, NASCAR limited engine bore to this value.

So in order to get this bore without siamizing the cylinders, Chevrolet had to increase the bore center spacing, but as I said above, even though this engine is about the same physical size and displacement as the classic 350, it shares nothing with any generation production small block.

That and the tube frame architecture is why they are no longer "stock cars".

Duke

Duke-----

Yes, I don't think there's an engine in NASCAR today that's in any way based on a PRODUCTION engine or that shares any components with a PRODUCTION
engine. I think the last one that was actually partially based on a PRODUCTION engine was the GM engine with SB2 cylinder heads. The bottom end of that engine was based on a PRODUCTION Gen I small block.

This past year at the NCRS convention there was a NASCAR car on display. As we looked at it, a fellow that was manning the display came over and asked us if we had any questions. I then asked him about the engine. He told me it was a stock-based engine just as could be purchased through any GM dealer. I didn't ask him any more questions.

[Larry E.]

Re: Is it big or small?

Duke-----

Yes, I don't think there's an engine in NASCAR today that's in any way based on a PRODUCTION engine or that shares any components with a PRODUCTION
engine. I think the last one that was actually partially based on a PRODUCTION engine was the GM engine with SB2 cylinder heads. The bottom end of that engine was based on a PRODUCTION Gen I small block.
This past year at the NCRS convention there was a NASCAR car on display. As we looked at it, a fellow that was manning the display came over and asked us if we had any questions. I then asked him about the engine. He told me it was a stock-based engine just as could be purchased through any GM dealer. I didn't ask him any more questions.

Joe:
From what I have heard the (ROX or RO7) engine is kinda a blend between the older S/B Chevy Engine and the LS Engine. NASCAR will not permit the
Chevy Teams to use a pure LS type all out engine because it would produce too much horsepower making the series unbalanced. Larry