C1: Crate engine or rebuild?

[Robert I.]

I'm about to start restoring my 62 340 hp 4 speed.

My father bought this car new.

The engine is a 327 but was a short block, installed in the 70s. So the engine number does not match.

I'm assuming that since the engine number doesn't match, the value will be the same: rebuild or crate.

Should I rebuild the current engine or go with a crate engine?

It will be a driver.

One can find 290 hp crate engines. How do 290 2008 hp compare with 340 1962 hp?

Eventually I'd like it to look like the original engine, so I want heads that will accept the original aluminum valve covers.

[Alan S.]

Re: C1: Crate engine or rebuild?

Bob,
You posted your question in the section for folks looking for help using the
Tech Board. If you re-post in the Technical Discussion Section I'm sure you'll get lots of replies.
Regards,
Alan

[Peter M.]

Re: C1: Crate engine or rebuild?

Rebuilt and get the block properly renumbered, assuming that the casting #s are correct.

[Bob R.]

Re: C1: Crate engine or rebuild?

If you go with the crate engine you will have some difficulty trying to make the engine look original. The old valve covers won't fit on a new crate engine. The 327 block vents from the rear of the block and you can't do that with a crate engine. So if your intention is to make the car look original I would go with the rebuild of the 327.

[Robert I.]

Re: C1: Crate engine or rebuild?

Rebuilt and get the block properly renumbered, assuming that the casting #s are correct.

I've always questioned the fact that so many Corvettes out there, from this era, have matching numbers.

So I can take a block, which I know is not the original, and have it renumbered to match the car, and presto, the numbers are matching?

[Dennis A.]

Re: C1: Crate engine or rebuild?

To me...the 327 is a great engine and the 327/340 had the get up and go. If you rebuild, your engine will be balanced, where the create engines just don't make it my book....

[Joe C.]

Re: C1: Crate engine or rebuild?

I'm about to start restoring my 62 340 hp 4 speed.

My father bought this car new.

The engine is a 327 but was a short block, installed in the 70s. So the engine number does not match.

I'm assuming that since the engine number doesn't match, the value will be the same: rebuild or crate.

Should I rebuild the current engine or go with a crate engine?

It will be a driver.

One can find 290 hp crate engines. How do 290 2008 hp compare with 340 1962 hp?

Eventually I'd like it to look like the original engine, so I want heads that will accept the original aluminum valve covers.

Robert,

1968 was the last year that SBC had the block casting with the road draft tube outlet (crankcase vent) in the rear. If you use any later block, you'll have to use a vented rocker cover. Further, you must use an intake manifold with the oil fill tube hole in front (crankcase vent). Very few modern intakes still have this provision. Two of which are the "Edelbrock Performer" or "Edelbrock Performer RPM" intake manifolds. Edelbrock's preferable (IMHO) "Air Gap" series do not!

"Value" of your car probably won't change very much whether you have a crate engine installed as opposed to a "numbers' matching" engine (i.e.: a restamped, matching , correctly dated block), versus the "original engine".

Power ratings (advertised horsepower) were given as gross flywheel, up to and including 1971. 1972 and later numbers are SAE net, flywheel HP. These later numbers are typically about 20 per cent less than gross ratings.

"Horsepower" in and of itself, is not a valid parameter to use when determining engine choices. One should look at the overall engine output curve as related to torque.

Most modern crate engines like the ZZ3,4, and especially the ZZ383, make monstrous torque, fairly low in the RPM range. They typically peak early (before 4000 RPM), which means that "horsepower" numbers are relatively low. These engines are a "blast" to drive around town because they'll light up the tires easily, and be very "quick" from a standstill. They will, however, be wheezing fairly early, and are just about "done" by 5500 RPM.

Vintage SHP engines make lots of peak power, but relatively little low/midrange torque. These engines are what you'd call "peaky", and require a close ratio transmission, to keep them in their peak power band. What this means is, that "on paper" they sound "powerful" but in the real world, compared to the modern "torquers" or vintage "low horsepower" engines, they are "dogs" at low engine speeds. The only real beauty of building a vintage "high horsepower" engine, is that when it "comes on the cam" at speeds over 3000-4000 RPM, you begin to feel those G forces in the SOTP, pushing you back into your seat. This "rush" is not felt with milder engines, because their power "curves" are broad, with a relatively flat apex.

My vote would be to build up your 327 block using its stock 3.25" stroke, and installing a set of strong connecting rods. Camshaft choices would be limited to L76/L84, LT1, L79 or L82, and L75, in that order.

L76/L84 and LT1 camshaft will provide very similar operating characteristics in terms of peak power. The difference between the two is that the L76/L84 develops less idle vacuum and consequently provides a noticeably "lumpier" idle. It also develops considerably less torque, up to about 2000 RPM. The L76/L84 has a very slightly higher peak power output, which occurs about 100-200 RPM later (approx 6700RPM), depending on engine volumetric efficiency. The LT1, being stronger in the low range, will not deliver the power "rush" of the L76/L84 cam because of its slightly broader torque curve.

Joe

[Robert I.]

Re: C1: Crate engine or rebuild?

To me...the 327 is a great engine and the 327/340 had the get up and go. If you rebuild, your engine will be balanced, where the create engines just don't make it my book....

A friend of a friend just put a 383 crate engine into an ElCamino and is not pleased with it.

[Peter M.]

Re: C1: Crate engine or rebuild?

I've always questioned the fact that so many Corvettes out there, from this era, have matching numbers.

So I can take a block, which I know is not the original, and have it renumbered to match the car, and presto, the numbers are matching?

Yes, Bob, that's right. If you take note of the NCRS guidelines, there is a difference between restoration and counterfeit. A restored car can have a "numbers' matching" engine (i.e.: a restamped, matching , correctly dated block), versus the "original engine". There is nothing wrong with having a CORRECT restamped, matching , correctly dated block for restoration pursposes. When doing this one MUST notifiy any prospective purchaser of the car that such a car has a correct, numbers matching engine, but it is NOT the original engine. To do otherwise would violate the letter and spirit of the NCRS restoration process. Moreover, to make these changes and not tell anyone is FRAUD, clear and simple. Any such fraudulent misrepresentation will certainly form the basis for a civil, if not criminal, law suit.

FYI...

[Joe L.]

Re: C1: Crate engine or rebuild?

A friend of a friend just put a 383 crate engine into an ElCamino and is not pleased with it.

Bob-----


Why isn't he pleased with it? The 383 crate engine is a great engine. Great torque and power.

In any event, from an originality standpoint, I think your best bet is to obtain a good, solid used block of the correct casting number (3782870) and correct date (within 6 months prior to the car's build date). You don't need to go as far as re-stamping the pad. It should not be too hard to find such a block; the 3782870 is NOT unique to Corvettes and there were LOTS of these made during the 6 month period that would be correct for your car (although a lot are Toyotas by now).

Keep in mind that once all is "said-and-done", building up such an engine is going to cost you quite a bit more than a crate engine, even a ZZ350 or ZZ383 which will have a lot more power and torque than the 340hp 327. But, all-in-all, how much power does a guy really need for a street engine, anyway?

[Stuart F.]

Re: C1: Crate engine or rebuild?

I have been faced with the same dilema on my 63 340 hp (L-76), only mine is the original engine which makes it even harder to justify on the basis of preservation. Since discussing it on this TDB, I feel confident that I am better off leaving it alone. I was mostly concerned with fuel availability for it as mine has not been apart yet so I have the original valves (no hard seats) and compression ratio. It still runs like a rabbit and it would take a "LOT OF CRATE" to beat it. The car has a 3.36 rear and, coupled with the Duntov cam and 461-x heads, she pulls like a banshee from mid to 6500. It will still pull red line in 1,2,and 3 (I'm chicken in 4th). I kinda have a rep as "Speed Racer" and resently dusted an El Camino w/383 crate from 30 mph up w/o a sweat. This makes my son cringe as he's afraid either my old metal or this old man may fold under the fatigue! Ha!

Stu Fox

[Joe C.]

Re: C1: Crate engine or rebuild?

Bob-----


Why isn't he pleased with it? The 383 crate engine is a great engine. Great torque and power.

In any event, from an originality standpoint, I think your best bet is to obtain a good, solid used block of the correct casting number (3782870) and correct date (within 6 months prior to the car's build date). You don't need to go as far as re-stamping the pad. It should not be too hard to find such a block; the 3782870 is NOT unique to Corvettes and there were LOTS of these made during the 6 month period that would be correct for your car (although a lot are Toyotas by now).

Keep in mind that once all is "said-and-done", building up such an engine is going to cost you quite a bit more than a crate engine, even a ZZ350 or ZZ383 which will have a lot more power and torque than the 340hp 327. But, all-in-all, how much power does a guy really need for a street engine, anyway?

Well........................partially true. Attached, find the dyno sheet from a currently available ZZ4 (350) engine. Notice that the torque curve is flat and broad. This engine makes very nice torque, and is a fun street motor, and excellent truck motor. The torque peaks early, though (3500 RPM), which means that peak power is going to occur early, too (about 350 SAE net @ 5250). Remember that this motor has a 3.48" stroke.

A vintage SHP engine, like the 1964-65 L76 using the 3849346 ("30-30") camshaft, made 365 peak HP (gross) @6200 RPM and 350 FT-LBS (gross)@ 3400RPM. Converted to SAE net, this would be about 300 @6200 and 290 @3400. This is with a 3.25" stroke.

Because the ZZ4 engine has a longer stroke, if you de-stroked it to 3.25, its entire torque output would shift lower and would also peak later. The ZZ engine has a higher VE, better combustion, sealing, and less friction losses than the vintage engine due to more efficient heads and manifolding, 750CFM Holley, smaller chamber volume, hypereutectic pistons, lowered friction piston rings, and less viscous lubricating oils, among other improvements. If you only factor in the VE difference, you would have to shift the ZZ4's entire power curve lower again, by an additional 15 - 20 per cent, to match the VE of the vintage 327.

So, in a (theoretical) "apples-to-apples" comparison, a de-stroked ZZ4, using older, less efficient heads, manifolds, and a 585 CFM carburetor, would make less peak power at a lower engine speed than a vintage L76. In fact, the theoretical engine would perform more like a vintage L75 than a vintage L76!

Conversely, if one built-up a 327 (4.00 x 3.25) engine using a vintage SHP camshaft, but using modern manifolding/heads/carburation to boost VE, then the result would produce much more peak power at a higher engine speed than the ZZ4, but with less low speed torque. The result would produce the same torque profile as a vintage SHP engine, but with the entire output shifted upwards by 10 - 20 per cent!

It all comes down to what the owner wants from his vintage Corvette. If he wants his prize to retain its original characteristics, but with improved performance across-the-board, then he should "modernize" his original engine around its vintage camshaft. If he wants a low speed "torque monster/stump puller" and super-duty truck motor, then he should install a ZZ4 or ZZ383.

Joe

[Jimmy G.]

Re: C1: Crate engine or rebuild?

My vote would be a crate motor so you can have new technology and not worry so much about rebuilt parts.

[Joe R.]

Re: C1: Crate engine or rebuild?

I'm about to start restoring my 62 340 hp 4 speed.

...Eventually I'd like it to look like the original engine, so I want heads that will accept the original aluminum valve covers.

Hi Robert:

Just to reinforce what some other posts have already said, you can not use the original valve covers on a modern crate motor. On your original engine (and presumably on the replacement short block), the intake for the PCV system was from a hole in the bock back by the distributor. This hole is not present on modern crate motor.

To use a modern crate motor, you would have to switch to valve covers that have appropriate holes for the PCV system.

Also, modern crate motors do not have an oil input in the intake manifold, so you would have to use your old manifold or use valve covers that have an oil cap.

In summary, if you want a truely original appearance including original valve covers, you will need a pre-1969 block that has the "road draft tube" opening in the back. You probably have such a block right now, so that is one option, but you could also get a different block that has the same feature.

That block could even be one with the correct casting number and correct casting date for your car, which is worth 262 to 300 of the 350 points that the NCRS allocates to the block, depending on the pad surface. So, you don't even have to restamp the pad to get into the Top Flight category.

[Jim T.]

Re: C1: Crate engine or rebuild?

Robert from GM you can purchase part #24502540 and use your 62's cast aluminum valve covers on the later cylinder heads on GM's crate engines. This part is a aluminum spacer that is retained with the center bolts and you can attach the earlier valve covers to the spacer. This spacer also allows the use of roller rockers raising the valve cover higher.
This application still does not cure the problem of having your type of early Corvette cast aluminum valve covers on crate engines since they do not have holes in the covers for the pcv valve and fresh air into the engine.
You could purchase the LT-1 type valve covers.
I had always liked the appearance of the earlier Corvette cast aluminum valve covers and purchased a set for my 70 Corvette about 30 years ago. I cut a hole for the pcv valve and the fresh air source and installed new gourments. Removed the pcv valve to install oil using a funnel. I later bought a set of LT-1 valve covers but did not install them on my 70.
The 350/350 fuel injected GM crate engine set up is something I would like to have but it will not fit under the hood of my 70, the injection unit is to tall. I think I have seen it installed in earlier Corvettes like yours.
The 350/330 GM crate engine is another good choice to consider as well as the 350/290.