Small block Chevs

[RESON8]

I am considering putting a small block chev into a torana. I have been told that i can only go up to 308cubes without needing an engineering certificate and full inspection.

What i need to know is there any external difference between a 307 and a 350 chev. Can you fit the internals of a 350 into a 307?

Does the engine number or any other casting numbers on the block giveaway the size of the motor?

Thanks in advance people.

[ducky boy]

ford man myself so im not really clued on chevs. hovever the engine number would be the first giveaway.
engineering should be a snack if everything is done legit
watch these naysayers
what sort of torana?

[RESON8]

Is going into a LX hatch, was going to go the turbo 6 but i think that a v8 is the way to go

[Bitsamissing]

Externally, all the same.

you can pretty well make any size with various crank/bore options.

Make what you like & call it a 307, (or 302), anyway. The chances of a bore/ stroke measurement being called on would be extremely remote.

From memory the aussie car optioned 307 ht's hg's etc had nothing on the engine number relating to cubic capacity.

[Jim]

just make sure the block is from an equivalent year or later so you don't have to go through all the pollution BS.

[Hqcoupe350]

You can get up to 5.8 litres registered in an LX if you have made all the necessary mods to the car e.g. better brakes, chassis strengthening, good suspension, diff etc. In other words, consult an engineer. You're gonna have to do those mods anyway unless you want a death trap. Should be a walk in the park if you are sensible.

Or you could go the easier way and stroke a 308 to 355 cubes. EPA would be none the wiser.

[jmac]

The very abbreviated version :

The 307 is a 3.875 bore and 3,25 stroke. Original 283s (one of the first sizes of any note historically imho) had the 3.875 bore, but a 3 inch stroke, I'm not certain but it's been suggested that they threw the 327 crank (or one with the same 3.25 stroke) into the 283 block which gives 307 cubes for a torquier 'lo po' engine option.

There are some tiny giveaways, but with the amt of mix n match going on, the original head or manifolds wouldn't be used or original. So basically nobody wouldbe able to pick it for sure unless they took it apart and physically measured the bore and stroke (or did a volume test where they attach a guage to the spark plug hole and rotate the engine, as is used sometimes to check an engine is capacity legal by c.a.m.s)

You can typically tell a 400 chev smallblock from the rest. It is the only sb chev that is externally balanced, and so has an 'offset' weight on teh harmonic balancer You can get aftermarket 400 cranks to be internally balanced,. The only other 'obvious' difference is that the blocks have a different number of welsh plugs compared with other small blocks.

But I'd bet my left nut nobody would spot it rego wise (an engine builder would for sure)

What's probably most important is the fact that the 307 has the aforementioned smaqller bore. It means it won't breath nearly as well, and you can't run huge valves as they'd potentially come close to hitting the block edges. even when they don't hit the closer proximity of the cylinder wall means that it obstructs flow in and out of the cylinder.

So with the same basic combination, it'd make less power than a 4 inch bore motor would (i.e. 350 or 327). Even if you were to run a shorter stroke crank in a 4 inch bore block (i.e. a 3 inch stroke, There is actually such a thing as a 302 chev, they were made with 4 inch bore and 283 size 3 inch stroke. They were made specifically for a 5 litre racing class). Anyhoo, siad 302, with the same go fast bits as a 307 would make more power. A 350 with the 3.48 stroke would (obviously) make shitloads more.

So basically, esp considering how relatively affordable a 350 short motor to suit reco is, it'd only cost a tiny bit more to go with a 350 vs a 307. There is even such a thing as a 305 chev. it is the lo po option as well. It uses (from memory, I have nothing to do with the 305s and never will) the same stroke as a 350, but an even smaller bore than a 307. Either one of them for performance is like cloning pharlap then amputating one of it's legs, so to speak)

I'm not advocating fraud, but as a matter of trivia, I'd bet nobody would ever question it's a 307. An engineer _might_ suspect it, as it wouldn't be the first time, but no way someone at vic roads etc would imo. About the only way it might come up is if the motor was previously fitted to a car and that engine number is already known to correspond to a 350. Again, just for trivia's sake, finding a scrap 307 block, then restamping the 350 block with the number that was stamped on the 307 would probably address that. the other thing is that chevy engine numbers are on the block deck, and often end up getting machined off if the block deck is machined down to alter piston deck height.and have to be restamped. Legally there are certain steps required for such a restamp, to the original number, but I guess more than a few engine reconditiones have just gone ahead and restamped the original numbers after deck machining.

And that's all I've got time for,

John McKenzie

[RESON8]

Thanks for the replies guys and Jmac you really know your chev motors

I guess the easiest way to go about it all would be go with a holden 308 and stroke it, no one would quesion that.

But parts for chev motors are looking to be alot cheaper then holden gear these days + plus i have been told that for equivalant engine size mods and capacity the chev motor makes more power "quoting a friend here not proven"

The car will be if fitted with chassis strengthening kit so it wont be a slapper half arsed effort.

[Hqcoupe350]

Given the popularity, price and availability of VN-style EFI heads, the gap between Holden and Chevy is not as far as it used to be in terms of bang for buck. In many ways the VN-style heads are superior to chevy heads (23 degree production angle heads anyway). Still, you cant beat 50+ years of aftermarket support.

[BigMuz]

355 from come, vn heads and single plane carb manifold, and I'll bet it makes the same stick as the equivalent dollars of chev.

Muz

[Hqcoupe350]

Almost but not far off. You cant buy a Holden 383 stroker crank for under 500 bux

[EXWRX]

A retrotech LS1 transplant would be cool