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tberg 11-30-2019 08:51 AM

427 Engine rebuild
1 Attachment(s)
I'm looking for some advice. I will be pulling my numbers matching 1968 SS 427 motor out to be rebuilt. I want to know if I should upgrade from a flat tappet cam to a roller rocker set up. Also do I have to have the block decked, because I need to keep the engine pad numbers.
Any and all advice is much appreciated.
Thanks Tom B.

Brooksey 11-30-2019 09:22 AM

One thing the rebuilder did on a straight 6 I had rebuilt is install hardened valve seats to help wear with unleaded gas. The block was decked because it had some pitting as well. I had a very good rebuilder and a very worn engine so I left it up to him on what needed doing. Good luck

tberg 11-30-2019 09:24 AM

Good idea about the hardened seats. Thanks

Brooksey 11-30-2019 09:38 AM

1 Attachment(s)
This is my rebuilt inline 6 for my nova

Big Dave 11-30-2019 09:49 AM

Pull your numbers matching engine and put it in a bag. You can store it on an engine stand or under a bench. Then buy a 454 out of a light pickup and rebuild that as a 496 or bigger motor.

Big blocks are not very efficient on today's pump gas. To get anything out of them you have to increase the displacement. A Mark IV BBC can be easily stroked with a 4 inch stroke crank (so a 454 stroked a quarter inch to get to 496 cubes by boring it 0.060" over) and a more modern Gen V or Gen VI block can be stroked to 4 inch to obtain a 518 cube motor. You will need a new oil pan either way as only a light truck has had a 454 under the hood since 1974. And the truck pan will not fit a car chassis (this goes for all of GMPP's 454 or 502 crate engines as they all ship with pick-up truck pans).

You can recycle your entire top end or buy replacement aluminum heads. You want a roller cam because modern reduced ZDDP motor oil will fail; wiping the cam, if you try to use it with a flat tappet cam. If you want the cheaper flat tappet then you will be paying a lot more for ZDDP rich motor oil which usually runs $8 bucks a quart. So if you run the engine much over time you would actually save money installing a roller cam in the first place.

You can stamp the rebuilt block with your old numbers if you like them: though numbers won't make it any faster or more reliable. Your rebuilt truck engine will look just like your old 427 with the proper decals.

Big Dave

tberg 12-01-2019 09:53 AM

Thanks Dave' but it took me many years to find a real SS427 and numbers matching engine so I really want to put the original mill back in.
Any suggestions along that line would be very appreciated.

Big Dave 12-01-2019 11:24 AM

If it is the original engine it will all fit, without looking for aftermarket parts. The engine you have now requires premium leaded gas and makes it's power by reving. Think of it as a 350 horse 327 engine only super sized. At 6,800 RPM it will make 480 horse on 100 octane fuel (it was derated not by changing any parts for the insurance company, but by testing the engine power at a much lower RPM).

So your 427 engine is just the way the engineers designed it back in 1963 for NASCAR racing, including it's domed high compression pistons. It will also have the closed bath tub shaped small combustion chamber heads that shroud the valves. In 1967 that head had the walls of the combustion chamber laid back to open the chamber up for free breathing. This dropped not only the static compression, but also the power it makes if you do not use a hemi-spherical dome cut in half piston to fill the void (why the Rat was called a Semi Hemi).

With flat tops it will make more than a 396 with open chamber heads, but not as much as it would with 11.0:1 pistons and 100 octane fuel. The big block was designed to be a high compression deep breathing high reving race car engine. That design and tooling was paid for by also using it as a truck engine, but that truck engine had different heads, pistons, block, and cam to make it a slow reving torque beast that is an additional inch wider and two inches taller than a passenger BBC. (the only common parts between the truck and passenger engine was the water pump and valve covers.

The open chamber 454 replaced the 427 in the production line up in 1971 (introduced in 1970 exclusive to the Corvette and the Chevelle SS). In 1972 the compression dropped in an effort to save the engine for use in cars, but the power drop off was so great that people opted for the 350 small block instead of the smog motor version of the big block. It was last installed in a car in 1973 (carried over to the Corvette as an option through 1974 when it was dropped there also). But like I said the small block had more power and better mileage which was important in 1973 because of the OPEC crude oil embargo. This made gas hard to find in 1973, and by 1976 that gas was unleaded with 87 being the highest octane you could buy.

By 1974 you could buy a 454 SS Chevelle or Corvette for twenty to thirty percent of the resale value of a 427 or 454 version of the same car (Hemi 'cudas and 440 GTX-Road runners were being crushed because no one wanted them at any price). That is why the seventies trough the late nieties were called smog era cars and if you wanted a powerful fast ride you bought a BMW or a Porsche, or a Jap hot rod like the Datsun Z.

It wasn't until GM introduced the redesigned second generation small block that power returned. GM did this redesign of the small block not because people were crying for more powerful engines; but to reduce emissions as mandated by ever tightening standards. Making more horsepower was a side benefit that people quickly noticed. Especially when older muscle cars still on the road had their doors blown off by a 4600 pound four door Impala SS.

The LS-x engines know as generation three small blocks replaced the gen two SBC two years after they were introduced; so you may never have even heard of them. From 1974 and up the only vehicle with a BBC installed under the hood was a light truck, because they were exempt from the emission laws of the era (it had to be a three quarter ton or a one ton truck to be exempt).

Big Dave

jayoldschool 12-01-2019 01:26 PM

Talk to your local machine shop. Tell them exactly what you want. No machining of numbers. The block may or not need over boring.

Why does it need a rebuild? Smoke? Compression test results?

tberg 12-01-2019 04:25 PM

In general it is just tired. doesn't ping with 93 octane, I'm sure the heads are worn to enable it to run on 93 octane. Been together for 50 plus years.

BA. 12-05-2019 04:20 PM

I'm a fan of changing to the roller cam setup, I've had it done on 2 engines now.

Regarding the decking of the block, I think you have to 'go through the motion' so that you can clean up anything too uneven but somehow ensuring 100% that the machine shop guy knows not to go so far as to wipe out those precious front pad digits.

Good luck man!

tberg 12-06-2019 08:28 AM

68 Big block 427 engine rebuild
Thanks for the info and support.

Big Dave 12-06-2019 11:31 AM

Decking without removing the numbers can be done it is just going to cost you a lot more. I have never seen any one pop a hood at a car show and say oh look an IE application code! Only you will know that it is all original unless you make a big sign that states it is numbers matching. Even then only you an very few others at the show will care. All the show goers are interested in are those wide valve covers and what you have done to it to make an all original faster.

In 1966 the 427 was a brand new engine. The 427 in a Biscayne two door sedan was considered to be a sleeper; because no one knew anything about the combination. That, and expectations of performance were low compared to a Chrysler with a Hemi or a Ford with a 427 side oiler which where tearing up the track in that time period.

In 1966 the best performing car (that year's stock and super stock winner) was a 350 horse 327 in a Chevy II SS. (because it offered the greatest horsepower to weight of any vehicle this side of a motorcycle). In 1967 it was the 375 horse Camaro in stock and a 427 Camaro in Super Stock once again it was power to weight.

In 1968 the Impala and Caprice were running neck and neck in size and weight with a Cadillac that had a 472 cubic inch V8 powering it. Ford introduced the 427 SHOC engine that made Fords competitive again in racing and in stock and super stock they had the 428-429 powered Mustangs From 1970 through 1975 it was all Chrysler thanks to the 426 Hemi being offered in lighter car bodies.

Newton said it best with his second law of motion with F=ma. Nothing has changed since then, and it is all about power to weight which is why in the sixties it was all about larger engines being introduced every year. The 472 Caddy became a 500 cube engine, the BBC 396 became a 454, and though Chrysler lost the Hemi head to emissions, it still had their 440 as the big dawg.

You can not easily change your car's weight, but you can easily turn a 427 into a 496 and still have all the original numbers and decals on the air cleaner cover. Because the Mark IV block has the mains fed by an oil gallery it is limited in the length of the stroke, so the 4.25" stroke is the max for a Mark IV block. A Gen V block can contain a 4.5 inch stroke because the oil gallery was moved above the cam tunnel.

Using a new Gen V 454 block, that doesn't leak oil thanks to a one piece rear main oil seal, you change the displacement by lengthening the 4.25 inch bore block by adding to the stroke length.

427 had a 3.76" stroke
454 had a 4.00" stroke
496 has a 4.25" stroke
511 has a 4.38" stroke and a
525 has a 4.50" stroke

The 4.500 bore ZZ 502 Gen VI block adds even more cubes, and still looks like your 427. They all look alike from the outside. Retain stock mufflers and dual exhaust pipes you can speak softly and still carry a big stick to beat the competition with. The only 427 that I would run would be a stroked SBC 400 block thanks to today's gasoline.

Back when 104 octane rated Sunoco 260 was pump gas I ran an L-88 427 in my 1968 Camaro RS SS thanks to a Yenko built block in my Baldwin Motion III conversion. It put my Edelbrock tunnel ram equipped, Vertex mag fired, solid roller Crane cam Camaro into the low ten teens with 14 inch wide Firestone slicks to launch it. Power to weight!

Big Dave

67SS 12-06-2019 07:39 PM

pm sent.

tberg 01-17-2020 09:47 AM

Thanks guys for all the input. The TH 400 has been rebuilt and the 427 is in the machine shop. With the motor and trans out I have doing
some clean up on the engine bay and firewall. I have replaced the shifter control cable which was binding. The carb is out and being rebuilt.
The engine rebuilder is leaving the numbers on the pad. Installing new cam and roller rockers. One question, will I have a problem with
the original valve covers being too flat?
I'll keep you updated.

68WASAGOODYEAR 01-17-2020 12:51 PM

Stock valve covers will not clear your roller rockers. If you want to keep the stock look of the engine - and with a numbers matching SS427 you should - take a look at these from CFR Performance. They resemble the OEM covers but are tall enough to clear the roller rockers. They make these in chrome as well.

67SS 01-17-2020 01:24 PM

Or you can always buy a spacer. I run them on couple of engines, RTV spacer to head, gasket valve cover to spacer.

Big Dave 01-17-2020 05:06 PM

Tall valve covers are the same width as the stock valve cover. So the only thing that is different is the height. Unless you are running a STUD GIRDLE (I do) you do not need a taller valve cover. The only thing that interferes or requires a taller valve cover is the poly locks on the top of the rocker stud. BUT CompCams, Crower and ISKY both sell shorter polylocks that allow a stock cover to fit (designate LP or S after the polylock number to get one to clear a valve cover. I ran 1.7 and 1.6 chomoly rockers under a stock seven fin Corvette (Z/28) die cast SBC valve cover.

All of my big blocks use roller rockers. I used stock die cast Gen V valve covers (with 402 decals) on my 582 BBC, with a spacer to get them to fit. But I had some Bill Mitchel and CalCustom stock height valve covers with no drippers under the valve covers and they did fit with short polylocks.

Now obviously if you are a poser and are running a tall valve cover because your hero who runs a valve lift of one inch or more has them than I guess you need them. I prefer to pass as a sleeper than run a lot of decals or SS trim. Much prefer converting a four door taxi into a nine second missile.

Big Dave

tberg 01-18-2020 10:33 AM

Thanks guys, Dave you are right about the poly locks. The engine rebuilder mentioned that about smaller locks.
He also said I may have to bend or remove the oil drippers inside,

Moyock13 02-01-2020 08:51 AM

Quick question about the 454. If junk yard hunting for a 454 what should I look for? Which block would be the best to build?

Big Dave 02-01-2020 12:13 PM

One from 1970 through 1990 would be best as that is a Marl IV big block that is just like what Chevy put under your hood back in the day only bigger. If it is out of a pick-up it will have an oil pan that will not fit your car body (hits the front cross-member). Bad news a BBC was only offered in a pick or van after 1973 because they couldn't pass emission requirements in a car.

From 1991 to 1995 Chevy made the ill fated Gen V that requires you to use the small "peanut port" round (versus oval port) heads that comes on the truck; or you get a bead coolant leak that will fill your oil pan with water in under ten seconds. Chevy redesigned the BBC for EFI so there is no fuel pump boss on the front of the block. It has the aforementioned redesigned coolant passages that do not line up with the holes in a Mark IV head. It makes up for this by not leaking motor oil from the die cast aluminum valve covers (sealed with an O-ring) and the main rear seal is also sealed with an O-ring that fits over the rear crank inside an aluminum housing. Finally the timing cover is plastic and sealed with a rubber seal instead of a paper gasket, and has only ten screws holding it in place instead of the old leaky tin cover that had fourteen screws that held it in place.

A Gen VI BBC also has the O-ring oil seals and shares the same adapter plate and valve covers. What you don't see is the re-redesigned coolant passages that DO accept a Mark IV head without leaking like the Titanic. It also only appears in light trucks and has a truck oil pan so you have to replace it with an aftermarket one. The Gen VI block also DOES have a provision for a fuel pump, even though it still has EFI (but hot rodders complained to GMPP about the lack of a fuel pump for their carburetored applications).

Then there is to Gen VII Vortec 8100 tall deck marine block that is made by and used by Mercruiser in their launches and yachts. Chevy uses it for a cheap imitation wanna be diesel engine until they could finalize the purchase of the Isuzu diesel truck engine from Japan called a Durmax. This engine isn't a BBC it only vaguely resembles one.

It has four big head bolts instead of the six used by a BBC, so the tall thin Cathederal port LS style heads heads do not interchange with a BBC. The water pump is designed to pump sea water and will not bolt up to any Chevy BBC. Oil pan and valve covers are different, in fact the ONLY part off of a Vortec 8100 that will interchange with a BBC is the Hitachi gear drive starter motor. Nothing else interchanges. It is also a tall deck block because it has a longer stroke than the 454 and the designers though that it would have four piston rings like a tall deck truck block, It doesn't: but it is still a tall deck that means it makes it hard to fit in your car and the hood won't close. The tall truck style EFI manifold that only fits this motor is too tall to close the hood even if you could get the motor below the top of the fenders. There are few to any aftermarket parts for this motor that physically resembles an LS, only super sized.

Big Dave

68WASAGOODYEAR 02-01-2020 01:48 PM

Casting number 14015445 is a 2- or 4-bolt main Mark IV block made from 1978-1990 (lots of them out there) and is used a lot in the crate engine world. It is stamped "HI PERF". This would be a keeper if you find one.

Moyock13 02-01-2020 04:30 PM

Thanks ya'll. Happy Hunting!

Big Dave 02-01-2020 09:48 PM

All big blocks are the same in strength whether a two bolt or four bolt. They differ only in the main caps and additional machining to be able to hook up an external oil filter and coolant line for a Corvette (one way to tell in the junk yard if it is a four bolt Mark IV.) All Gen V and Gen VI blocks have four bolts (but since none of them went into a Corvette none of them have the external ports machined into the block).

You can add four bolt caps to a two bolt block at any time, by paying a machinist to put them on (the main caps have to be either billet steel caps from the after market or used cast iron caps from a donor block that was ventilated. All Gen VI blocks are designed for a roller cam (taller lifter bosses and machined for a lifter retaining keeper spring or "spider" and at the front of the block a cam retaining plate). Gen V could have a roller but most didn't as only the last year of production used a roller.

The purpose of a four bolt cap is to keep the cap within the registers at high engine speed (keeping it straight in the block) There is no additional clamping force as both hold the crank in place vertically equally well.

Because of it's truck application, only a Chevy has a four bolt block, none of the other earlier engines "W" series or a SBC before 1969 had four bolt mains. None of the other GM engines (Buick, Caddy, Olds or Poncho) have four bolt mains. Ford small block engines doesn't use them because their blocks split in half right down the center-line of the crank through the lifter valley at high RPM. Only Chrysler RB (426 and the 440) have a four bolt main, while the former FE series of engines 332-390-427 (and the 428 semi competition version) which were race bred for NASCAR had full skirts with 6 main cap bolts The "385" series of big blocks from Ford (429 and 460) had two bolt mains. So a four bolt block this side of the SBC high performance engine and the BBC has them, making a four bolt rare.

It is the side to side motion (cap creep, or walking) that the added two bolts limit above 6,000 RPM. So if you are not intending to rev it to the moon you do not need a four bolt block. They are only used in racing, marine or trucks that live at wide open throttle all of the time. Unlike a SBC that adds extra metal to the bottom end of the block the stock block is the same whether machined for two or four bolt caps which is why the books all say 2 or 4 bolt mains as if they couldn't make up their minds.

All of that said if you are going to make serious power buy a Dart Big M or a Brodix aftermarket block. It really is cheaper in the long run. Stronger and 12-23 pounds heavier than a stock block due to the added metal added to make a bullet proof foundation for your motor. Avoid truck blocks and marine blocks; they are a lot more trouble (expense) than that "good deal" makes them worth.

Big Dave

tberg 02-20-2020 06:33 PM

Just to update you guys on the progress of the 427 rebuild. Just met with the rebuilder to discuss next steps.
the engine was taken apart and inspected. Just like I thought the lifters and the cam were in pretty bad shape.
the heads were black and sooty but overall everything else was in pretty good shape. The only thing we are saving is the forged crank.
when it is back together we will be dynoing the motor, going with the roller rocker set up.
Last week I was at the Atlantic City car auction and was talking to a rep from Amsoil. Only heard good things about their
products. Anybody want to share their opinion.
Thanks Tom B.

Big Dave 02-20-2020 09:04 PM

I am not loyal to any one brand as I buy oil based upon it's formula. I do not buy synthetics because my engines are dinosaurs and grew up with mineral oil. My oil has to have HIGH ZDDP levels because even though I have a roller cam it still has cast iron rings and the rollers all ride on steel bearings that need wear protection. I live in Florida so I run a higher viscosity than those who live in polar regions. I also run an oil cooler in addition to a transmission cooler because that makes the oil last longer without oxidizing (oil is used to cool the pistons and valve springs were the heat is above the oxidation point of oil or above 450 degrees F.).

I do like Valvoline and Lucas Oil because both companies pump money directly back into supporting auto racing rather than just advertising how great they are. I also prefer a Pennsylvania crude to a Texas crude base as there is less paraffin in the oil base, but that isn't as important over all to the other requirements.

Big Dave

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