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Old 05-09-2023, 09:55 AM
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Default 68 Corvette Convertible 427 4 speed

I may be inspecting this Corvette which is described as a 427/435 hp, with 3x2 sticker on the air cleaner. In pics it looks like it could use a paint job. Is there a way to verify the pedigree and if the engine matches? What will I be looking for on inspecting to assist with verification?

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'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
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'69 LeMans Vert, 350, #47 heads: Non-running project
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Old 05-09-2023, 10:53 AM
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Last 6 digits of the VIN are stamped into the block in front of the RH cylinder head. There are casting numbers on the top of the block behind the distributor. Get a book called Chevrolet By The Numbers. Once you get past the numbers, time to look at the birdcsge and frame. Also, 68's have many one year only body and trim pieces, making them very unique compared to '69s.

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Old 05-09-2023, 11:07 AM
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Lots of good information on the CorvetteForum.com as well.

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Old 05-09-2023, 12:16 PM
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Thanks. Just watched a YouTube video on C3 frame issues- wow.

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'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
'64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears
'69 LeMans Vert, 350, #47 heads: Non-running project
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Old 05-09-2023, 12:31 PM
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Wow is right. Those early C3 cars are plagued by some amazingly severe rot issues that lead me to believe they are somewhat junks.

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Old 05-09-2023, 01:20 PM
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Yes, there can be rot to the ladder frame, check closely at rear and swing arm at stub( half shafts) driveshafts. If the bolts holding the swing arm brackets are rusted, it can be a real bitch to get out and repair. Also 68's are notorious for overheating due to lack of sealing around the radiator, a problem they resolved in 69. The 427/435 is either the L71 or the aluminum head L89, both create huge heat in engine bay that migrates thru into cockpit area. Lastly, even if the numbers match. be aware that, even when I owned the marque, there were speciality shops that could easily re-create a block to as-built number status including the broach marks on the block. There is no PHS for Chevy like we have for Pontiac.

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Old 05-09-2023, 01:34 PM
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If the '68 you're interested in has lived in a good climate, odds are the metal isn't shot. My '67 is a two-owner Oklahoma car with no rust problems.

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Old 05-09-2023, 03:31 PM
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Thanks. It’s supposed to be an iron head engine. Reportedly needs paint and restoration. Very interesting Re: the ability to fake a matching engine…

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'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
'64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears
'69 LeMans Vert, 350, #47 heads: Non-running project
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Old 05-09-2023, 03:41 PM
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I had a coworker that had a ‘68 350 4-speed Corvette coupe back in the early 1980s.

It was a little rough and man was it a pile of crap for being only about 15 years old at the time. Rough riding and had those odd push buttons on the doors.

I’d consider both the ‘68 and ‘84 Corvettes to be the two years to steer away from, both first years of their generations and too many issues and drawbacks.

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Old 05-09-2023, 03:43 PM
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I'll save you from buying the book. In case of no VIN or non-matching VIN and the block was replaced, the casting number on the back of the block on a 435hp car will be 3935439 or 3916321. The tach will have a 6500 red line on a 435hp car.

I've been building these cars for 50 years, first thing I look at on a C3 are the door jams, once rust gets serious, the body sags and the jams close up. Second area is the body mounts behind the kick panels. Kick panels are easy to remove and the seller should supply pics willingly. This area is where the lower door hinge post and rocker panel are welded together. Common area to rot on coupes and verts from roof and windshield leaks. This area only got body color overspray. If that looks good check out the rear trailing arm mounting and adjacent frame rails. The frame rail that kicks up rots out at the bottom as well as the square recessed end of the main frame rail. Reproduction frame rail sections and birdcage parts are available and although a major repair, it's not too difficult.

'68s have a lot of one year only parts, door shells included and they rot out near the latch assembly. Repops are not available. '69 and later doors have different outer door handles, but they can be modified to fit. Also look at the headlight reinforcement. There is a steel bar that the headlight assemblies mount to. It's a heavy steel piece that is originally riveted to the fiberglass with aluminum rivets. Galvonic corrosion builds up and pops through the paint. In '7e they bonded the reinforcement to the body. Feel underneath for rivets or glue.

The fiberglass after all these years and depending on how many paint jobs it's had can get thin. Also once you strip the paint you might find a lot of edges that have been sanded or rounded off. Fiberglass is pretty easy to shape and work with.

Rust issues are actually less bothersome overall to repair than on steel body cars. C1-C3 Corvettes are fun to work on, like a big model car.

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