Engine tear down '66 427/390 HP....interesting

[Michael G.]

Good day all,

Made tear down of my '66 427/390 hp engine today with some parts giving impression of a virgin block. Interesting observations:

• Original pistons (part #3869968) with ink stamp on bottom (letter A) and well as ink stamp on top (#10) of two to three pistons...what's up wif dat
• Appears to be original timingset...slop and all. Missing some of the plastic teeth as well. Most of the plastic ended up in oil and oil pump screen....that'll kill an engine !
• Original thin intake end rail gaskets with GM stamp on gasket.

Are these the original pistons (part #)for the 427/390 hp?


10 what? 10 dollars? 10 ponies?10 beers? What does this mean?



Appears to original timing set with broken teeth. Engine actually well before tear down.


Chain slop.....no other way to put it!


Debris found in oil pan and pick up....timing gear plastic and gasket material.

[Rob M.]

Re: Engine tear down '66 427/390 HP....interesting

Fun photos - thanks for posting.

[Clem Z.]

Re: Engine tear down '66 427/390 HP....interesting

Good day all,

Made tear down of my '66 427/390 hp engine today with some parts giving impression of a virgin block. Interesting observations:

• Original pistons (part #3869968) with ink stamp on bottom (letter A) and well as ink stamp on top (#10) of two to three pistons...what's up wif dat
• Appears to be original timingset...slop and all. Missing some of the plastic teeth as well. Most of the plastic ended up in oil and oil pump screen....that'll kill an engine !
• Original thin intake end rail gaskets with GM stamp on gasket.

Debris in pan and oil pickup...timing gear plastic and gasket material

the "A" is to select fit size for the piston in the bore during assy at the factory

[Michael G.]

Re: Engine tear down '66 427/390 HP....interesting

Clem,


Letters B, C and E were observed on other pistons? Does the piston part # show to be the original piston for the 427/390 hp?

[Patrick H.]

Re: Engine tear down '66 427/390 HP....interesting

Michael,

If you look on the bottom pan rail (i.e. where the oil pan attaches) you may find letters that correspond to the pistons. At least, they do on small blocks.

Patrick

[Tracy C.]

Re: Engine tear down '66 427/390 HP....interesting

Clem,


Does the piston part # show to be the original piston for the 427/390 hp?

Na...my book says these are out of a 62 Studebaker Six banger... Who you trying to fool Maynard?



tc

[Michael G.]

Re: Engine tear down '66 427/390 HP....interesting

Tracy,

Appreciate your demented less than helpful response......LOL but am needing to confirm the part # show in image as orginal 427/390 hp pistons.

Good to hear from you.

[Chris E.]

Re: Engine tear down '66 427/390 HP....interesting

Here my pictures from my original pistons out of the 327/350. Not sure if this helps at all or not. I didn't observe any markings on the top of the pistons like you did though.

[Jeff G.]

Re: Engine tear down '66 427/390 HP....interesting

Interesting topic since I've experienced the same thing with 2 different 1969 427 / 390 engines. Here's picture of a timing gear I've hung up in my garage. The chain on this one actually jumped off the gear while driving locally. Luckily the valves didn't get crushed by the pistons or worse. On my other engine I had dropped my oil pan to repair a small hole and found the tell tail signs again with nylon teeth sitting in the bottom of the pan.

This is a core weakness for this type of engine. I assume the same timing sprocket is used in the 400 HP engines. I would be surprised if the same is used in the solid lifter engines. Maybe someone can chime in on that. The bottom line is that we should all be on the watch for the problem in these original engines. I know we encourage people to drive these original cars / engines over distances to get judging points, but be aware that this weakness could cut a trip short with a disaster.

[Dale S.]

Re: Engine tear down '66 427/390 HP....interesting

In the late 60's we sold Republic timing compents. The sales pitch was no plastic gear teeth. This was a common problem then. Dale

[Kenny C.]

Re: Engine tear down '66 427/390 HP....interesting

The use of nylon teeth was to prevent gear noise from the front end of the motor which was considered to be objectionable. If any of you ever ran dual idler gears drive in an engine then you know what gear noise can be on an extreme scale. These timing sets were used across the entire line of engines for almost every car without really any distinction of whether or not it was a grocery getter or a muscle car. Frankly I doubt the factory really cared about ultimate longevity since timing sets typically far outlasted any warranty issue. After all if the motor sucked up a valve or two after 100K miles they could sell you another engine or maybe a whole new car.

[Michael G.]

Re: Engine tear down '66 427/390 HP....interesting

Jeff,

My 1968 Z-28 had same type timing set...nylon cog!

[Joe R.]

Re: Engine tear down '66 427/390 HP....interesting

Jeff,

My 427 / 425 (solid lifters) came with the nylon toothed timing gear. I'm replacing it with metal, of course.

Joe

[Joe L.]

Re: Engine tear down '66 427/390 HP....interesting

Interesting topic since I've experienced the same thing with 2 different 1969 427 / 390 engines. Here's picture of a timing gear I've hung up in my garage. The chain on this one actually jumped off the gear while driving locally. Luckily the valves didn't get crushed by the pistons or worse. On my other engine I had dropped my oil pan to repair a small hole and found the tell tail signs again with nylon teeth sitting in the bottom of the pan.

This is a core weakness for this type of engine. I assume the same timing sprocket is used in the 400 HP engines. I would be surprised if the same is used in the solid lifter engines. Maybe someone can chime in on that. The bottom line is that we should all be on the watch for the problem in these original engines. I know we encourage people to drive these original cars / engines over distances to get judging points, but be aware that this weakness could cut a trip short with a disaster.

Jeff-----


The nylon/aluminum cam sprockets were originally used on ALL Mark IV big blocks, including L-88 and ZL-1. The 1965-66 and 1967-71 SHP and HD used sprockets and a chain that were slightly wider than 67-74 non SHP, but all were nylon/aluminum.

[Joe L.]

Re: Engine tear down '66 427/390 HP....interesting

Jeff,

My 1968 Z-28 had same type timing set...nylon cog!

Michael-----


ALL 66 and later small blocks used a nylon/aluminum cam sprocket, including all Z-28 Camaro and all LT-1 Corvette.