Making a 350 out of a 327 (3892657)....

**Domenic T.** · August 29, 2010, 11:15 AM

Re: Making a 350 out of a 327 (3892657)....

The 327 is a better engine than the 350 in that car. That small journal crank can spin up faster. I had a 365HP 327 in my old vette and took it out to rebuild it for my 63. I put a fresh 370HP 350 in it and it ran good but didn't wind up as fast as the 327 which may have been the best of all the small blocks in a LIGHT car.

DOM

**Duke W.** · August 29, 2010, 11:26 AM

Re: Making a 350 out of a 327 (3892657)....

First understand that all other things equal a 327 and 350 will make about the same peak power at the same mean piston speed because the only difference is stroke.

So the 327 will have to rev higher to achieve peak power, but the 350 will make higher average power from idle to the redline because it has higher average torque.

The typical way to run a 350 crank in a small bearing block it to cut the mains down to 2.30" from 2.45", which is going to cause some loss of crankshaft strength, stiffness, and durability.

It depends on what the original engine rated power was, but if it was a 327/275 (which is basically the same as the 327/300 except for exhaust manifolds) wait until the next issue of The Corvette Restorer where you will learn how to make L-79 type top end power with the smooth idle and stump-pulling low end torque of the 275/300 HP 327s without altering the OE appearance of these "medium performance" 327s. All the changes are internal, undetectable, and will pass a PV.

So if you can find a correct block, build it to the Special 300 Horsepower configuration specifications with the McCagh Special camshaft.

Duke

**Steven S.** · August 29, 2010, 11:29 AM

Re: Making a 350 out of a 327 (3892657)....

I know of a '66 Nova L79 block that was fitted with a 350 crank, I'd have to double check but I believe he said the crank was turned down to the small journal diameter. This particular engine made the Nova it was in a real street sweeper back in the 70's.

Steve

**Dan D.** · August 29, 2010, 11:39 AM

Re: Making a 350 out of a 327 (3892657)....

Years ago we cut a 350 crank down to fit a 327 block in a stock car. It ran okay for a while, but not too many races. It broke the crank right at the center main. So I would not cut the mains. If you want to use the same block I would leave it as a 327. GM made the 350 mains fatter for a reason - it needed the extra strength. The 327 is by far the best small block there was, especially for street use. -Dan-

**Duke W.** · August 29, 2010, 12:39 PM

Re: Making a 350 out of a 327 (3892657)....

The 327 bearing sizes are perfectly adequate for the 350. The reason the 350 crank journals - both main and rod - were increased was to provide sufficient journal overlap to ensure proper strength, stiffness, and durability.

In a road engine that doesn't see high revs very often, cutting down the crank is probably okay, but as was stated above, in a high revving racing engine it causes limited crankshaft life.

Given that a 350 crank only yields about seven percent more displacement on a 327, I don't think it's worth the risk. On a 283 it yields 16 percent more displacement, which is significant, so it's a viable option as long as you don't rev it too high.

Also, consider that the run-of-the-mill 350 crank is cast and all 327 cranks are forged, so they are inherently tougher and basically indestructible in any reasonable road engine configuration as long as it never gets oil-starved.

The 327 has a great combination of torque and revs in a relatively light car- say no more than about 3300 pounds, which includes early Camaros.

With proper head massaging and attention to assembly detail they will make useable power to 6000-6500 with a hydraulic lifter camshaft and 7200 with the LT-1 mechanical lifter camshaft with nothing more than inexpensive and reliable OE equivalent parts in the valve train, including valve springs.

Duke

**Joe L.** · August 29, 2010, 01:13 PM

Re: Making a 350 out of a 327 (3892657)....

Originally posted by Greg Linton (45455)

.....but he would like to replace it with a correct looking one.

......but the way I understand it, all of these 67 only blocks were small journal except for the 350. Is that true?

Another option I guess would be to just build a correctly dated 657 block and leave it as a 327.....

Greg------

1) A "correct looking" one? A 1967 327 can be externally configured to appear absolutely identical to a 1967 350. There is absolutely no way to externally discern the difference between 1967 327 and a 1967 350.

2) The 1967 350 cid engine used in the Camaro SS was the only large journal 1967 small block. Even the 302 cid engine in the 1967 Z-28 Camaro was small journal.

**Clem Z.** · August 29, 2010, 01:34 PM

Re: Making a 350 out of a 327 (3892657)....

depends on how much $$$ you want to spend but you can buy 350 rotating assy with small mains to fit the block

**Joe L.** · August 29, 2010, 02:49 PM

Re: Making a 350 out of a 327 (3892657)....

[quote=Duke Williams (22045);
Also, consider that the run-of-the-mill 350 crank is cast and all 327 cranks are forged, so they are inherently tougher and basically indestructible in any reasonable road engine configuration as long as it never gets oil-starved.

Duke[/quote]

Duke-----

The 1967 350 cid crank was forged steel. Most 1969+ 350 cranks were nodular cast iron. However, 1969-70 L-46, 1970-72 LT-1, and 1973-80 L-82 cranks were forged steel.

**Greg L.** · August 29, 2010, 03:58 PM

Re: Making a 350 out of a 327 (3892657)....

Thanks for the quick response guys.

It sounds like the way to do this then is to turn the crank to fit the block. I'm just currious why the prefered method is that rather than opening up the mains in the block to fit the new 350 crank?

I'm not too keen on cutting the crank that much for reasons mentioned, plus does it not grind away all the hardness so it will now wear faster? I was hoping to be able to put this together for him with some of the parts from an old 350 that I've had in the shed for some time now but I'll look into a small journal rotating 350 kit and see what it's worth....just seeing what our options are. We're not in a rush to so the next Corvette Restorer will be perfect timing!

Maybe we should just find a date correct 3892657 327 block and build it as per that next Restorer article. The 67 350 was rated at 295 hp so this article should be just what we need. I'm not sure if we should have it broached and stamped as a 350 or just deck it and leave it blank seeing as it will still be a 327. What would you guys suggest? To me stamping it would be about the same as making BC/CC appear like lacquer!

One other thing that I'm wondering about is the location of the Z-bar pivot on the block. Did all of these 657 castings have it machined just above the oil filter boss or would this have been a Camaro (350) only thing? The engine in my brother's car now has this pivot mounted to a flat plate of 1/4" x 1" x 10" steel that picks up on the pivot boss on the bellhousing and a machined hole FORWARD of the oil filter boss. I'm just wondering if this pivot mount location will cause us to look for a real 67 350 block or if the 67 327 also had it in the same location as the 67 350.

**Joe L.** · August 30, 2010, 12:15 AM

Re: Making a 350 out of a 327 (3892657)....

Originally posted by Greg Linton (45455)

Thanks for the quick response guys.

It sounds like the way to do this then is to turn the crank to fit the block. I'm just currious why the prefered method is that rather than opening up the mains in the block to fit the new 350 crank?

I'm not too keen on cutting the crank that much for reasons mentioned, plus does it not grind away all the hardness so it will now wear faster? I was hoping to be able to put this together for him with some of the parts from an old 350 that I've had in the shed for some time now but I'll look into a small journal rotating 350 kit and see what it's worth....just seeing what our options are. We're not in a rush to so the next Corvette Restorer will be perfect timing!

Maybe we should just find a date correct 3892657 327 block and build it as per that next Restorer article. The 67 350 was rated at 295 hp so this article should be just what we need. I'm not sure if we should have it broached and stamped as a 350 or just deck it and leave it blank seeing as it will still be a 327. What would you guys suggest? To me stamping it would be about the same as making BC/CC appear like lacquer!

One other thing that I'm wondering about is the location of the Z-bar pivot on the block. Did all of these 657 castings have it machined just above the oil filter boss or would this have been a Camaro (350) only thing? The engine in my brother's car now has this pivot mounted to a flat plate of 1/4" x 1" x 10" steel that picks up on the pivot boss on the bellhousing and a machined hole FORWARD of the oil filter boss. I'm just wondering if this pivot mount location will cause us to look for a real 67 350 block or if the 67 327 also had it in the same location as the 67 350.

Greg------

The block could be machined for a large journal crank. However, I'm not so sure this would be as easy a machining operation as it might seem, especially the rear main journal. Still, there are probably some shops with the capability and experience.

All of the 657 castings will have the same bosses for clutch cross shaft.

**Clem Z.** · August 30, 2010, 07:23 AM

Re: Making a 350 out of a 327 (3892657)....

grind down the mains and make sure they leave a nice radius in the corners and the crank will be OK for street driving. the heat treat on chevy cranks is less than .010 so any grinding on the journals removes it but this is not a problem with a street engine. there are companies that sell a 350 crank with small main that are forged cranks if you want to pay the $$$$

**Tom P.** · August 30, 2010, 08:44 AM

Re: Making a 350 out of a 327 (3892657)....

Stroking a 327 with a 350 crank is a snap (in the world of engine building).
And yes, I have personal experience at this. And, if you choose, you can even stroke a 327 with a SB400 crank (but I've only done one of these).

To stroke a 327 with a 350 crank, there are two approaches, both of which have already been touched on.
One method is the simplest and probably the cheapest. It involves turning the mains (2.45in) of a 350 crank down to small journal size (2.30in). There is one other machining process that also needs to be done that most people don't know about and they get the big surprise when they go to drop the 350 crank into the 327 block!!! The flange of a 350 crank, BETWEEN the rear main journal and the seal journal, is a larger diameter than the flange of a 327 crank. Thus, the groove for the flange in both the block and the cap is shallower (I forget the different in dimensions of the flange/groove). As a result, the flange on the 350 crank also needs to be slightly turned down so that it will fit in the groove of the 327 block. Another difference between the 327 and 350 block is the difference in main cap bolt length. Consequently, the bolt hole threads in the blocks are different depths. I recommend (althought it is not absolutely necessary) doing a VERY minor modification to the threads/holes in the 327 block to accept the longer style 350 main cap bolts. I also prefer to go one step further and use main cap studs instead of bolts. If you like to use a windage tray, ARP makes studs that have a smaller stud size on the end of the stud for installing a windage tray.
Once all of the above is done, then the engine is built just as ANY 350 would be built, using the larger 350 rods. A 327 BLOCK DOES NOT NEED ANY CLEARANCING DONE TO THE BOTTOM OF THE BLOCK FOR THE LONGER 350 STROKE.

The second method of stroking a 327 block with a 350 crank is to line bore the 327 block to a 350 main bore (as already mentioned above). This method will have a higher price tag, but will also be a little stronger overall. The flange (as mentioned above) between the rear main journal and the seal journal will still have to be reduced in diameter, but nothing else will need to be done to the crank.
When line boring/honing the 327 block for a large journal crank, it is important to know that the notches in the block AND main caps, for the tangs on the main bearing halves, are totally different between the two blocks. So, you will need to use a machine shop that is quite familiar with cutting the new notches in the block/caps. Again, it would be advisable to modify the holes in the block for the main cap bolts to accept the longer 350 bolts, and again, use studs instead of bolts.

While we're on the subject of stroking a 327 block, and since I mentioned that a SB400 crank can also be installed in a small journal 327 block (to make a 383), here's how that's done.
Making a 383 from a 350 involves turning the mains of a 400 crank (2.65in) down to 350 main size (2.45in). So, this will need to be done to a 400 crank (as well as reducing the diameteer of the flange between the rear main journal and the seal journal). OR, a 400 crank can be purchased that already has the smaller mains, but the flange will still have to be reduced.
As described above, the main journal bores of the 327 will need to be opened up to the size of 350 main bores. After that, it's identical to building a 383 from a 350 block. For those who are familiar (and those NOT familiar) with building a 383, it is necessary to clearance the bottom of the cylinders for the added 400 stroke, and WHEN USING STOCK 350 RODS, it is necessary to do MINOR clearancing of the heads of the rod bolts on the side of the rods that faces the cam (for cam lobe clearance).

A couple of additional comments.
NOT all 327 cranks were forged. About 1964, some of the small journal cranks were cast.
As mentioned, the 1967 350 cranks (ONLY USED IN THE 67 CAMARO SS350) were large journal (2.45 mains-2.10 rods). The 350 blocks used in the 67 Camaros were somewhat of a hybrid. They were large journal blocks (ALL 68-later small blocks had the large journal cranks, and the blocks no longer had the rear hole), and they still had the hole in the rear of the block for crankcase ventilation, which permits the use of NO HOLE valve covers. This one of a kind, hybrid block was ALSO available as a replacement engine from GM for a period of time (all the ones I've seen were 3959512 castings, same casting number as early 327 blocks). I have one on an engine stand dated Jan 67--large journal, rear hole for crankcase vent. They are kind of scarce, but if a car is not going to be numbers matching, this is an ideal block for building a 383 with no mods other than clearancing the bottom end for the rods.

**Greg L.** · August 30, 2010, 08:56 AM

Re: Making a 350 out of a 327 (3892657)....

Excellent, thanks again guys.

Does anyone want to give their thoughts on my restamping question?

**Paul J.** · August 30, 2010, 09:28 AM

Re: Making a 350 out of a 327 (3892657)....

Originally posted by Greg Linton (45455)

Excellent, thanks again guys.

Does anyone want to give their thoughts on my restamping question?

Are you trying to start a fight? There are lots of opinions on this and the archives are full of discussions.

https://www.forums.ncrs.org/showthre...mping&uid=1492

Making a 350 out of a 327 (3892657)....

Making a 350 out of a 327 (3892657)....

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