68hemi

I know the 327/300 h.p. engine was super popular for many years and installed in 100s of thousands in nearly every body Chevrolet built over several years.
My question is was the engine identical in all of these cars or were there any differences when installed in the Corvette? I am thinking no but don't know absolutely.

MikeM

Nothing different that would change the horsepower rating. Many differences that made up all the different engine codes over the four year run of that engine.

MOXIE62

All 63 corvette blocks had a single digit for the year in the cast date at rear of block. Not sure but I think passenger blocks had double digits.

68hemi

I am referring to internal differences. I know that the carb changed in 1966 to a Holley and that the h.p. rating I the same. My question is were there any internal changes between passenger car and Corvette engines?

Nowhere Man

The biggest change was the exhaust manifolds But as far as I know the internal parts was the same

Boyan

This has nothing to do with passenger car or Corvette. It has to do with the Plants the engine was made. Tonawanda or Flint. All small block Corvette’s were Flint, but not all passenger cars were Tonawanda.

MikeM

I am thinking the Corvette engines used chrome rings vs unplated rings for pass. car. Could be wrong. That's a long time ago.

SWCDuke

327/300s with manual transmissions in both pass. cars and Corvettes had 2.5" manifolds from '62 to '65, but the pass. cars had 2" pipes so the pipes had to be expanded to fit the manifolds. After '65 all had 2" manifolds, so the Corvette 2.5" pipes (manuals) had to be adapted to the 2" outlet, except PG that had 2" pipes.

For '66 the conn. rods were redesigned adding a little "hump" of material adjacent to the bolt seats that makes these rods more durable than the early rods that were prone to fatigue failure, especially on high revving mechanical lifter engines.

A new camshaft was released for '67. The base cam for all '57-66 engines (220, 230, 245, 250FI, 275FI HP/ 283s , 250 and 300 HP/327s) was replaced with this new cam that recognized that big port heads as machined by Flint are restrictive on the exhaust side, so a few more degrees exhaust duration via a slightly earlier opening exhaust valve is advantageous. This cam/pin assembly, 3896929 (Federal Mogul CS-74) has 194/202 degrees .050" lifter rise duration, 112 LSA and the IPOML is 108 deg. ATDC. The prior cam was a single lobe design 196 degrees .050" lifter rise with about the same LSA and indexing. Chevrolet did not increase rated power, and I don't know if a difference could be measured on a dyno. One advantage of the later cam is that it has milder lobe dynamics, so it's easier on the valve train. A new slightly higher rate valve spring was released for this cam (and ALL other small blocks) and I think it also used a new retainer that yielded slightly higher spring height. If you set up the valve springs for .090-.100" coil bind clearance the valve float speed is in the 67-6800 range, but a 327/300 engine will be wheezing at 5000 without head massaging.

Another change was the appearance of the abominable nylon cam sprocket in 1965. Prior to that the "wide" silent chain was used on pass. cars and Corvettes. I don't know if the 327/300 was available in any truck models, but if it was, the engine would have had the double row roller chain.

Duke

68hemi

Thank you Duke. As always you have covered all the points.

rayL79

I remember reading that Corvette engines used different (Moraine) bearings than the passenger car engines.

MikeM

You need to do a little homework on your first paragraph. This isn't totally accurate.

327/300's weren't available in trucks but 327's were. Also available in boats, generators, and Massey-Ferguson combines.

MikeM

That's my recall as well but I can't substantiate that.

MikeM

You asked for internal differences between Corvette and Pass car. All the changes listed above were across the board. Which way did you want it?

68hemi

Well, I figured that since he made no mention of it as others have that there are no internal differences. Thanks.

Vettegeezer

I vaguely remember reading that the Corvette blocks were cast of higher strength nodular iron which necessitated a different casting number than passenger engine 327's.

W Guy

ALL the 300hp engines were built at Flint, Corvette & Passenger. For other engines, Passenger cars used both Flint & Tonawanda built assemblies, but primarily Tonawanda.

Verne

vettsplit 63

Maybe it was the way the question was asked, but the other internal differences between the 250 horse 327 and the 300 were the heads and intake manifold. The 250s got the single pyramid power pak head, and the 300's got the double hump heads with the intake using the AFB versus the 250's WCFB

MOXIE62

Right, all 63 corvette blocks were Made at Flint, which has only a single digit.

MikeM

That was true until 1965 and then the 250 engine got the double humps.

68hemi

As the OP the original question was about a 300 h.p. engine not a 250, 350 or 375 h.p. engine. Very simple question.
It has been determined in this thread (and these things I already knew) that there was a carb change to Holley in 1966 and there were exhaust changes depending on year and trans.

My question is specific to internal differences between Corvette and passenger cars such as cam and compression.