well, I am on my 3rd year of owning my 1984 oldmobile. Its a 307, generation 1. I would strongly like a rebuild on the engine and transmission. I have the 5 hole valve covers which were such a pain for so long. My uncle who changed them thought they were from out of country. I did so much research and they were the stock valve covers. The valve cover on the passenger side, bottome right has a small leak which is better than the leaks before. I bought some after market 10 hole covers that I was just confused on how they would fit with the extra holes. I love my car and it drives. I got the carb rebuilt, some hoses need to be fixed. My dad talked me out of a rebuild on my engine, but I knew it was right. I was thinking longevity, and he seemed to worry about the price. I dont care about the price. I care about driving to work and riding in my olds with no engine problems. I am strongly considering getting it a rebuild on my 307 just becasue it runs good and has that power for that engine. I love it and its smooth. Any advice from the older fellas would be cool.

 

The 5 hole valve covers tend to leak because the factory uses a bead of sealer around the perimeter instead of a gasket. The sealer dries and cracks and then leaks. Stupid, but it is what it is. The manual says to re-do it with sealer too. AFAIK, GM never made any 5 hole valve cover gaskets. You can use 10 hole gaskets, but should consider filling each little unused hole in that gasket with sealer to help stem leaks.

Some may tell you to rebuild it with a 350 or 403 Olds engine. While that might be ok, there's nothing wrong with the 307 rebuild. It's really just an smaller-bored 350 anyway. It's a great crusing motor.

Get yourself a GM Chassis Service Manual (CSM) set for your car. It's invaluable information.

Get at least the mechanical manual, but the electrical manual is good to have as well.

Here's a mechanical manual for around $30 shipped to your door. That's cheap. When you could get them new from Helm, they were several hundred dollars for the sets. It'll show how to rebuild your engine and contains info for checking gaps and clearances and torque values. They show special tools often, but you don't really need those to rebuild the engine. Make sure if you get one, it covers the car you have. If you have a 307, then you want this one.

https://www.ebay.com/itm/266895274666

If you want the entire set, you can get that too. You can get the WHOLE set for any and all 84 Olds here shipped for around $65. You can even sell the Firenza manual for cheap and get some money back. This set has the CSM, the Electrical Troubleshooting Manual (ETM) and the Supplement to the ETM.

https://www.ebay.com/itm/126521510000

There's a different manual for the Firenza, Omega, Cutlass Cruiser, and Ciera. You don't need that one. They look similar, so read the cover to find the application.

Are you going to rebuild it or farm it out? While the physical rebuilding of the 84 307 is the same as just about any other size Olds V8 engine, the main difference is the 5-hole valve covers and A.I.R. emission tube holes. If you still have an operating A.I.R. system that would need to have some attention to it on the engine itself. Get a good rebuild gasket set.

The main thing that is going to be an issue is ensuring you know where all that spaghetti of vacuum hoses and sensors goes, and what they do. This is where the CSM can help. The computer controlled carb and distributor, and all that can be daunting. The best bet on the carb for you right now is if it's running good, is just unbolt it and leave it intact, put it in a box and not mess with it. It'll retain its same settings when you put it back on. You may need to tune it after the rebuild, so be ready for that. It takes some skills to make sure you do it properly as you may have already found out.

Don't go wild on the bolts and things attached to the intake, like thermostat or sensors. The intake is aluminum and you could pull threads if you're not careful with old bolts.

If you haven't messed with computer controlled cars before, take LOTS of pictures of where and how the vacuum hoses are laid out on the engine. It'll help you remember what goes where.

Good luck.

 

I fought the valve covers on my Wife's Riviera for a long time until I took them off and redid them with a bead of RTV the way the factory did. They lasted a good ten years after that and when I rebuilt her entire engine in 2019 I did the same thing and they have not leaked a drop since then.

The key to it is getting everything spotlessly clean and making sure the valve covers are straight. It hard to get the head surfaces clean with the engine in the car but it is imperative that you do so. I use low voc brake cleaner which is mostly alcohol. If someone has used gaskets and over tightened the bolts you need to make sure they didn't warp the covers. There are little "dimples" in the metal that space the cover up off the cylinder head surface so there is room for the RTV.

I use Permatex Ultra Black rtv but any good quality rtv should work.

If the engine is running fine otherwise I would say fix the leaks and leave it alone

 

Navarrojoe which model of Oldsmobile ?

Glad to see the 307 living up to its reputation of being smooth and reliable. The power you like is that 240 lb-ft of torque. Makes the car jump every time you tap the gas.

Agreed !

Yes.

Navarrojoe if a rebuild is a must for your peace of mind, definitely consider both those options. Whatever the 307 does both the 350 and 403 do it better and easier. The emissioned 350 has 275 lb-ft torque and the 403 has 320 lb-ft torque, born in or generic rebuild. Cost and interchangeability are all within the same ballpark, assuming you have the THM200-4R transmission she will handle either factory version just fine... Only 3 reasons to ever keep a 307 instead are. Originality, sentimentality, and not having to lay out money for the internally upsized engines themselves.

Now going back to thinking your 307 may need a rebuild. How many miles on the engine ? Prime Oldsmobile 1964-1972, as well as other car makes from the same era generally averaged 100,000 miles before needing a major engine repair. Now in the 21st century cars are averaging 200,000 miles before needing a major engine repair. Olds 307 powered vehicles likely fall somewhere in the middle... The car guy reputation for Olds 307s is, "not much power but last forever" ...

If yours is relatively low miles then I agree with your dad and double down on what BillK said.

 

If the engine is mechanically sound, fix the leaks and drive it.

If you want to do some preventative maintenance, definitely replace the timing chain. There have been lots of discussions about the nylon covered chain.

Unless the engine is tired, smokes, or is making bad sounds, i wouldn’t tear apart a running car that you enjoy. Quality machine work is expensive and time consuming. If you want to build an engine, find a suitable core to build. That way you can take your time and build the engine as funds allow, while enjoying the car. Once the engine is finished, then you can make the change.