Hemmings Motor News Blog

Never worked on a Pontiac................plenty of GMC trucks and Chevy's though.

One thing was always a constant, besides the fact that they were great engines.............................the engineers were completely out to lunch when it came to the design of the exhaust manifold to exhaust pipe coupling arrangement.

I wish I had a dollar for every stud I busted.

Yes, I wish every automotive engineer had to replace an exhaust manifold gasket on a vehicle after 10 years and 100,000 miles. Maybe then they would change how they do things. Grrrrrrr . . .

The picture on the cover appears to be the standard Pontiac L-74 400 CID block. Jesssh I know this engine, both inside and out, like the backside of my right hand, even after 30 some years!

I once owned a '69 Trans-Am sedan with a L-74 w/ Ram Air IV, rated at 335 HP, and 4:11 rear end & Muncie M-22 4-speed manual. I bought it while I was Active Duty at Ft. Bragg back in '77 & owned it for almost 5 years......spent an entire year part-time (while attending Community College and working) just rebuilding the engine. Installed new everything in that block, from new push-rods, new valves, new hydraulic lifters, new Crane racing cam, and new TRW chrome dome 12:1 pistons, forged connecting rods, and crank. New bearings throughout. It was blueprinted and parts magni-fluxed. Unfortunately after 6 months back on the road the brand new oil pump failed and the engine seized-up solid @ 3am in the morning after leaving the weekly street drags. Man was I pissed. Good thing I didn't race it that night or it could have been much worse! I did have the #1 piston come up through the HO head.....

If I hadn't been in school at the time I would have kept the car. Too bad I didn't have a crystal ball back then 'cause the price of these cars has skyrocketed in the past decade. No way could I afford one now!!! Get this, I bought it from an Army buddy of mine for $2500 'cause he needed to pay his divorce attorney! Now you can't touch a pristine numbers matching one for less than $150K.

Kram, you're right about those damn exhaust manifold bolts and crappy exhaust pipe connections! They're the worse! and to get them to even loosen up you got to hit them with an oxy-ace torch! They have a tendency to rust-up solid in the block!!!! After that fiasco I elected to go with custom fabricated tuned steel headers for my car, even if it meant that I had to re-tighten the bolts every once and a while!

I do miss that Fire Chicken!

ps: I love seeing that ancient Rochester 4-barrel Quadra-Jet carb sitting atop the intake manifold! hehehehehhehe

: I love seeing that ancient Rochester 4-barrel Quadra-Jet carb sitting atop the intake manifold! hehehehehhehe

What do you mean ancient? I've got one sitting on top of my 454 out in the driveway......................which is sitting in my 86 GMC truck. Turbo 400 tranny. Every once in a while, if I've got an extra ten bucks, I'll take her out and stuff the gas pedal into the floor board, listen to that 4 barrel pop open, and blow everything out.

It's fun to see people's faces when they see what that old truck can do.

On that old Pontiac 400 CID block the Rochester most likely is ancient! On my old '69 Trans, it'd be 43 years old today! Old ancient technology and finicky too...

Glad yours is operating correctly!

Ahhhhhh, nottin' like opening up the secondaries and cleaning out the carbon, right Mark?!!! hehehehehehehe I envy you! The largest I have here now is a 6-banger w/ EFI......

I've torn into the engine a couple of times and redid the top end.

The best thing I ever did was to install one of these, along with high performance plugs, wires and cap. The response is instant, and she'll fly. To this day I have no idea what the top speed is. I get scared at about 120 mph. I don't need body parts flying off.

I've had it up to 100 mph..................towing a boat behind me. The looks are priceless.

If you run a Pontiac V8 such as 389-400-421-455 hard make sure you keep an extra quart or liter of oil in the crankcase as these engines are slow draining back from the top end. Oil pumps sucking air are of no use to the crank and other pressure oiled components. The plastic tooth timing gear was not much good past 55000 miles also.. Great engine for most applications.

I had forgotten about the nylon gears on the timing gear....................another brilliant idea.

Changed mine out about 10 years ago..............all metal, no problems since.

The timing gear in my old 400 was steel, not nylon. Thank God!

What year did they change them to nylon? I do remember that steel timing chain well + trying to get the damn harmonic balancer off the crank! I busted the first puller trying to budge loose the harm bal!!!! Then one of the bolts for the camshaft trust plate busted off in the damn block. Ohhhhhhh what freaking fun extracting that mother out......NOT!!!!

Other than those damn exhaust manifold bolts the worse thing about the design of that engine had to be the gasket setup for the water pump! The pits! Come to think of it, most of the gasket arrangements kinda suxed: the intake manifold gaskets and head gaskets in particular!!!! Thank goodness for FelPro gaskets and their red spray-on gasket goooop!!!

The harmonic balancer was horrible.................it's part of the reason I had forgot doing the job.

All three US manufacturers made some really bad decisions back in the 70s and 80s. The bulk of the timing gear was metal, with a nylon ring around the outside for the gears........................I have no clue as to what they were thinking. The replacement kit came with two metal gears and a heavy metal timing chain.

The main reason that I still love my 86, is that it was smog exempt, except for the AIR pump.

Don't even get me started on the miles of vacuum hoses that showed up under the hood of most cars during the 80s to meet emissions standards.

The nylon on the cam gear was to quiet them down.

Thanks. It worked....................right up until the teeth started getting stripped.

I"ve never noticed any noise with the metal replacement.

Not with "Woody Woodpecker" mufflers on.

On a very quiet car with no background noise the metal ones will have a hum after some wear.

Now that I think about it, I think I would like to have a hum.